Bridging and Conformational Control of Porphyrin Units through Non-Traditional Rigid Scaffolds.

Connecting two porphyrin units in a rigid linear fashion, without any undesired electron delocalization or communication between the chromophores, remains a synthetic challenge. Herein, a broad library of functionally diverse multi-porphyrin arrays that incorporate the non-traditional rigid linker groups cubane and bicyclo[1.1.1]pentane (BCP) is described. A robust, reliable, and versatile synthetic procedure was employed to access porphyrin-cubane/BCP-porphyrin arrays, representing the largest non-polymeric structures available for cubane/BCP derivatives. These reactions demonstrate considerable substrate scope, from utilization of small phenyl moieties to large porphyrin rings, with varying lengths and different angles. To control conformational flexibility, amide bonds were introduced between the bridgehead carbon of BCP/cubane and the porphyrin rings. Through varying the orientation of the substituents around the amide bond of cubane/BCP, different intermolecular interactions were identified through single crystal X-ray analysis. These studies revealed non-covalent interactions that are the first-of-their-kind including a unique iodine-oxygen interaction between cubane units. These supramolecular architectures indicate the possibility to mimic a protein structure due to the sp3 rigid scaffolds (BCP or cubane) that exhibit the essential conformational space for protein function while simultaneously providing amide bonds for molecular recognition.

Introduction

Defined molecular architectures are a prerequisite for the logical construction of multifunctional chemical systems. In <span class="Chemical">carbon‐based covalent systems the individual effector units are typically linked by either conjugating class="Chemical">sp‐ or <class="Chemical">span class="Gene">sp2‐hybridized units or by flexible sp3‐hybridized bridges. The use of short, robust, and spatially defined aliphatic linker units opens new avenues with their potential application as molecular isolators, resistors and rigid scaffolds, alongside the benefit of their inherent materials properties.

Synthetic chemists are continually seeking to prepare new rigid multi‐<span class="Chemical">porphyrin architectures due to their potential applications as organic conducting materials, near‐infrared (near‐IR) dyes, nonlinear optical materials, and molecular wires.1 A number of synthetic strategies have been employed to access these multi‐<class="Chemical">span class="Chemical">porphyrin arrays using approaches such as: (a) connecting the porphyrin units via phenylene, ethynyl, ethenyl or alkane linkers2 or (b) connecting two or more meso–meso‐linked porphyrin units via oxidative fusing reactions.3 However, most of the porphyrin arrays reported have problems such as poor solubility, synthetic inaccessibility, and conformational heterogeneity. In meso–meso‐linked porphyrin arrays, the porphyrin units are orthogonal to one another which can cause a significant energy/charge sink. Furthermore, porphyrin arrays joined directly by π‐conjugated linkers exhibit significantly altered UV/Vis spectra, indicating very strong electronic coupling, that is, loss of the characteristic of individual units due to delocalization of π‐electrons. Hence, it is necessary to design a molecule which can predictably exhibit a desired energy‐ and/or electron‐transfer process that is achievable without effecting electronic delocalization and/or an energy sink.1, 2, 3 A straightforward strategy for avoiding any undesirable overlap of the π‐systems may be to attach two porphyrin skeletons through non‐traditional rigid scaffolds such as bicyclo[1.1.1]pentane (BCP) or cubane. These saturated entities are transparent to UV/Vis light and exhibit specific three‐dimensional (3D) arrangements of the bridgehead carbons. This positions the chromophoric units in a rigid and linear fashion without any electron delocalization or conjugation such as to potentially reduce the drawbacks previously outlined.4

Herein, we report the first synthesis of <span class="Chemical">porphyrin dimers that utilize either <class="Chemical">span class="Chemical">BCP or cubane as a rigid linear scaffold (Figure 1). This library of BCP/cubane porphyrin arrays contains some of the largest non‐polymeric structures available for cubane and BCP.

Figure 1

Schematic representation of synthesized porphyrin arrays.

Schematic representation of synthesized <span class="Chemical">porphyrin arrays.

1,4‐Disubstituted <span class="Chemical">cubane is a well‐known bioisostere of para‐substituted <class="Chemical">span class="Chemical">phenylene rings due to the similar distance across the cube body diagonal of 2.72 Å vs. 2.79 Å for a benzene ring.5 BCP is the smallest member of the bicyclic alkane family, in terms of actual size rather than in terms of atoms present. Indeed, BCP exhibits the shortest non‐bonded distance between bridgehead carbon atoms of 1.85 Å, which is closer in bond length to ethyne (1.20 Å).6 The 3D, compact, electronically isolating, and saturated structures of cubane and BCP enable them to avoid undesirable π–π stacking which may lead to improved solubility of chromophoric arrays. Despite their desirable well‐defined dimensions and rigid‐rod geometries, the chemistry of these moieties is undeveloped, particularly in terms of functionalization or C−H‐activation at the bridgehead carbons.7

<span class="Chemical">BCP and <class="Chemical">span class="Chemical">cubane are transparent to UV/Vis light and most often their application is restricted to bioisosteres8 and crystal engineering.9 The structural pre‐organization and high thermal stability of these compounds make them attractive candidates by which to link two chromophoric units, but their use has been neglected so far.7a, 10 The limited use of these non‐traditional scaffolds is due to perceived complex synthetic procedures and limited commercial supply chain of precursors. In addition, appending rigid sp3 linkers as connectors between two chromophoric units is synthetically demanding.

Recent synthetic developments by Baran, Aggarwal and ourselves include methods based on decarboxylative <span class="Gene">sp3 C−C coupling to functionalize the bridgehead <class="Chemical">span class="Chemical">carbons of cubane and BCP.11 Knochel and co‐workers have also reported an efficient method to synthesize 1,3‐bisaryl substituted BCPs.12 Additionally, amide bonds have been introduced at the bridgehead carbons of cubane and BCP,13 however most of these reported moieties were used as bioisosteres8 or in crystal engineering.9 Yet, these compounds also have the potential to be utilized as molecular building blocks. Moreover, cubane/BCP could be implemented as rigid scaffolds linking two chromophores while providing a synthetic handle for molecular recognition of small molecules or ions.

Building upon the progress made in synthetically accessing these non‐traditional rigid scaffolds, we envisioned appending <span class="Chemical">BCP/<class="Chemical">span class="Chemical">cubane between two porphyrin units in a conformationally controlled manner. The utilization of semi‐rigid amide bonds for the attachment of a porphyrin skeleton to a rigid scaffold introduces a controlled conformational flexibility into porphyrin dyad(s). This allows significant modulation of the photophysical properties in the porphyrin dyad(s) through the coordination of transition metal(II) ions (Figure 2). By varying the distance and angles between the two chromophores it is hoped that the extent of the impact that cation coordination has on the photophysical properties of a multi‐chromophoric tweezer‐like system can be investigated.

Figure 2

Schematic representation of potential interactions between amide‐connected BCP/cubane derivatives: (a) H‐bonding interactions; (b) iodine⋅⋅⋅oxygen interactions; (c) intermolecular axial interactions; (d) potential interaction site with external metal ions.

Schematic representation of potential interactions between <span class="Chemical">amide‐connected <class="Chemical">span class="Chemical">BCP/cubane derivatives: (a) H‐bonding interactions; (b) iodine⋅⋅⋅oxygen interactions; (c) intermolecular axial interactions; (d) potential interaction site with external metal ions.

As <span class="Chemical">cubane and <class="Chemical">span class="Chemical">BCP are rigid and relatively inert scaffold, the amide bonds are the only variable in the system and a true measurement of their role in the conformational changes can thus be undertaken. We herein present porphyrin units bridged through non‐traditional BCP/cubane connectors as a test case for multichromophoric and/or electroactive systems in general.

Results and Discussion

Synthesis and characterization

The <span class="Chemical">amide bond is crucially important as one of the main chemical linkages found in biologically and pharmaceutically active compounds.14 <class="Chemical">span class="Chemical">Amide bonds exhibit a planar trans configuration of the N−H and C=O moieties and undergo very little rotation or twisting around the bond due to amido–imido tautomerization. The semi‐rigid nature of amide bonds enables conformational control over the molecular architecture of the compound they are part of courtesy of hydrogen bonds and the coordination of metal ions (Figure 2). To this end, the synthetic design of the current project focused on the functionalization of the bridgehead BCP/cubane carbons through amide bonds. Firstly, we started with the synthesis of small rigid building blocks. Carboxylic acid derivatives of cubane (1 and 2) were reacted15 with substituted aryl amines 3–12 to access the amide derivatives 13–29. The use of HATU/HOAt as an activating agent in presence of DIPEA in DMF at 25 °C provided the most suitable synthetic reaction condition by which to access amide substituted cubanes (13–29).

The reaction of 4‐methoxy<span class="Chemical">carbonyl<class="Chemical">span class="Chemical">cubane‐1‐carboxylic acid (1) with 4‐iodoaniline (3) proceeded smoothly in yield of 61 %. Similarly, we could couple 4‐ethynylaniline (4) and 4‐methoxycarbonylcubane‐1‐carboxylic acid (1) to access cubane 14 in a 37 % yield. Further, cubane‐1,4‐dicarboxylic acid was reacted with anilines 3 and 4 in above mentioned reaction conditions to afford the cubanes 15 and 17 in yields of 39 % and 67 %. The preliminary substrate scope was investigated by incorporating various combinations of structural motifs such as meta‐iodo/ethynyl‐substituted anilines to access the amide substituted cubanes 16 and 18. (Scheme 1).

Scheme 1

Amide coupling of cubane moieties 1 and 2 with amines 7–12.

<span class="Chemical">Amide coupling of <class="Chemical">span class="Chemical">cubane moieties 1 and 2 with amines 7–12.

Generally, meta‐/para‐ethynyl‐substituted <span class="Chemical">anilines reacted more efficiently with <class="Chemical">span class="Chemical">cubane‐1,4‐dicarboxylic acid (2) compared to those with iodo substituents. Attempts to purify the crude cubane compounds (13–18) via column chromatography, using silica gel, were mostly unfruitful due to degradation of the product on the silica gel. However, recrystallization from CH2Cl2 and excess hexane proved very effective in removing any remaining aniline and other impurities.

To demonstrate the potential value of this method, we next ex<span class="Chemical">amined the scope of meso‐<class="Chemical">span class="Chemical">amine‐substituted porphyrins in amide coupling reactions with cubane 1 and 2. 5‐(4′‐aminophenyl)‐10,15,20‐triphenylporphyrin (7) and its zinc(II) complex (8) were synthesized by mono‐nitration of TPP followed by reduction using procedures reported in the literature.16 Table 1 outlines the different reaction conditions employed to optimize the amide coupling reaction between 1 and 7. The use of HATU/HOAt in presence of DIPEA furnished the amide‐coupled cubane‐porphyrin array 21 in 79 % isolated yield. However, the use of other activating agents such as DIC and ethylchloroformate in the presence of TEA or DMAP also resulted in the formation of product 21, albeit in lower yields of 43 % and 31 %, respectively (Table 1). Reaction of porphyrin 8 with cubane 1 shows the neat conversion of porphyrin 8 into the cubane porphyrin array 19 in 52 % yield.

Table 1

Test C−H activation reactions for the amide coupling of 4‐(methoxycarbonyl)cubane‐1‐carboxylic acid (1) with 5‐(4′‐aminophenyl)‐10,15,20‐triphenylporphyrin (7).

Cubane [equiv]	Activating agent [equiv]	Base	Sol.	t [h]	Yield
2.0	DIC (1.3)	DMAP	THF	48	65
2.0	ECF[a] (1.3)	NEt3	CHCl3	120	75
6.0	DIC (1.3)	DMAP	THF	48	65
3.0	HATU/HOAt (1.3/1.3)	DIPEA	DMF	24	25

[a] ECF=Ethylchloroformate.

Test C−H activation reactions for the <span class="Chemical">amide coupling of 4‐(methoxy<class="Chemical">span class="Chemical">carbonyl)cubane‐1‐carboxylic acid (1) with 5‐(4′‐aminophenyl)‐10,15,20‐triphenylporphyrin (7).

<span class="Chemical">Cubane [equiv]

<span class="Chemical">DIC (1.3)

<span class="Chemical">DMAP

<span class="Chemical">THF

<span class="Gene">NEt3

<span class="Chemical">CHCl3

<span class="Chemical">DIC (1.3)

<span class="Chemical">DMAP

<span class="Chemical">THF

<span class="Chemical">HATU/<class="Chemical">span class="Chemical">HOAt (1.3/1.3)

<span class="Chemical">DIPEA

<span class="Chemical">DMF

[a] ECF=<span class="Chemical">Ethylchloroformate.

Notable compounds 19 and 21 were subjected to further functionalization. Base hydrolysis of zinc and free base substituted <span class="Chemical">porphyrin 19 and 21 yielded the <class="Chemical">span class="Chemical">carboxylic acid derivatives of cubane–porphyrin array 20 and 22 respectively, in quantitative yields. Similarly, the reaction of cubane‐1,4‐ dicarboxylic acid (2) with 7 and 8 resulted in access to the very first porphyrin–cubane–porphyrin arrays 25 and 26, respectively. Next we attempted the synthesis of ZnII–porphyrin–cubane‐free base porphyrin array 27 via amide coupling reaction of amine substituted porphyrin 7 and carboxylic acid substituted cubane porphyrin 20. Use of optimized reaction conditions resulted in unsymmetric dimer 27 in a 55 % yield.

To overcome the low solubility of <span class="Chemical">phenyl substituted porphyrins we changed to more soluble 4′‐methyl<class="Chemical">span class="Chemical">phenyl substituted amine porphyrins for further reactions. [5‐(4′‐Aminophenylacetylene)‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (9), [5‐(4′‐(4′′‐ethynylaniline)phenyl)‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (10), [5‐(3′‐aminophenylacetylene)‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (11) and [5‐(2′‐aminophenylacetylene)‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (12) were synthesized via modified Sonogashira reaction conditions by reacting the corresponding ethynyl anilines with [5‐iodo‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) in the presence of Pd(PPh3)2Cl2 (0.15 equiv) and CuI (0.3 equiv) in THF/NEt3. Amide coupling of 9 and cubane 1 proceed efficiently and provide convenient access to porphyrin 23 in isolated yield of 75 %. Similarly, porphyrin 24 was achieved in 56 % yield by reacting porphyrin 10 with cubane 1. Additionally, we tried the synthesis of cubane linked porphyrin dimers by using meta‐ and ortho‐substituted aniline 11 and 12. Reaction of 11 and cubane 2 resulted into the formation of dimer 28 in 36 % yield whereas ortho‐dimer 29 was synthesized in 50 % yield via reaction of ortho‐amine substituted porphyrin 12 and cubane 2. This robust reaction demonstrated considerable scope, from the utilization of small benzene rings to large porphyrin systems with varying lengths and at different angles with respect to the cubane plane.

The successful functionalization of <span class="Chemical">cubane motivated us to next attempt functionalization of the <class="Chemical">span class="Chemical">BCP using the same amide coupling method. However, initial attempts to synthesize the required BCP building blocks using HATU/HOAt, EDC, or DIC were unsuccessful. This may be due to unstable BCP intermediates capable of undergoing rearrangement to result in ring‐opened moieties. The BCP carboxylic acid was instead reacted with (COCl)2/TEA, followed by the desired amine. Initially, this reaction was conducted at room temperature similar to the cubane analogues above, however, this was met with limited success as the product was detected only in a small amounts by 1H NMR spectroscopy and mass spectrometry. This limited success was mitigated by the use of an elevated reaction temperature of 40 °C for both steps, which resulted in a significant increase in the product yields (49–77 %) (Scheme 2). The crude reaction mixtures were purified via recrystallization using a small amount of CH2Cl2 and excess hexane to access the desired products as white powders. The reaction of BCP 30 with aniline 3 and 4 resulted into the formation of 32 and 33 in 57 % and 61 % yield. Next, the meta‐phenyl substituted BCPs 34 and 35 were synthesized via amide coupling reaction of BCP 30 and aniline 5 and 6, respectively. Amide coupling of BCP 31 and anilines 3–6 resulted into the formation of amide substituted BCPs 36–39. We had found that the amide coupling reactions proceed optimally with meta‐/para‐substituted aniline in presence of (COCl)2/TEA. Unfortunately, amide coupling with ortho‐substituted anilines resulted in degradation. The ineffective ortho‐substituted aniline coupling may be caused by the proximity of the amine and iodo/ethynyl groups, enabling H‐bonding interactions between the moieties, ultimately reducing the basicity and reactivity of the amine. On the other hand, the cubane porphyrin dimer 29 was accessed in a 50 % yield due to the replacement of the small H‐bonding moieties with a porphyrin, preventing the reduced amine basicity.

Scheme 2

Amide coupling at bridgehead carbon of BCP moiety and substrate scope.

<span class="Chemical">Amide coupling at bridgehead <class="Chemical">span class="Chemical">carbon of BCP moiety and substrate scope.

The synthesized <span class="Chemical">BCP‐based building blocks 32–39 were further subjected to <class="Chemical">span class="Chemical">Pd‐catalyzed cross‐coupling reactions to yield porphyrin‐BCP conjugates (44–53), as shown in Scheme 3. Pd‐Catalyzed cross‐coupling reactions are versatile and straightforward approaches for porphyrins to form carbon−carbon bonds with a wide range of functionalities.1b, 17 In contrast to cubane,18 the BCP ring is more tolerant towards Pd‐catalyzed cross‐coupling reactions.19 The first BCP‐porphyrin array 44 was afforded using Suzuki–Miyaura cross‐coupling reaction of [5‐(4′,4′,5′,5′‐tetramethyl‐1′,3′,2′‐dioxaborolan‐2′‐yl)‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (41)20 and BCP (33). The same synthetic strategy was employed to access the meta‐linked BCP porphyrin array 47 in 78 % yield. Neat conversion of 41 into 44 and 47 encouraged us to try further attempts to synthesize the porphyrin‐BCP‐porphyrin arrays. The BCP porphyrins 50 and 52 were synthesized through Suzuki–Miyaura cross‐coupling reactions with [5‐(4′,4′,5′,5′‐tetramethyl‐1′,3′,2′‐dioxaborolan‐2′‐yl)‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (41)20 and BCPs 36 and 39, respectively. The isolated yields of meta‐derivatives 47 and 52 were higher as compared to those of corresponding para derivatives (44 and 50).

Scheme 3

Suzuki [Pd(PPh3)4, K3PO4, DMF ] or Sonogashira coupling (Pd(PPh3)2Cl2, CuI, TEA/THF) reaction conditions and substrate scope.

Suzuki [<span class="Chemical">Pd(<class="Chemical">span class="Gene">PPh3)4, K3PO4, DMF ] or Sonogashira coupling (Pd(PPh3)2Cl2, CuI, TEA/THF) reaction conditions and substrate scope.

The <span class="Chemical">porphyrin arrays 45 and 46 were synthesized using <class="Chemical">span class="Chemical">Sonogashira cross‐coupling reactions of [5‐ethynyl‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (42) and [5‐(4′‐ethynylphenyl)‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (43) and BCP 32. The Sonogashira reactions did not proceed well for the synthesis of meta‐derivatives 48 and 53, while a copper‐free modified Sonogashira reaction of [5‐iodo‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (40)21 with BCPs 35 and 38 proceeded well to access the porphyrin‐BCP arrays 48 and 53, in 73 % and 46 % yield, respectively. Detailed synthetic procedures are described in the Supporting Information. All newly synthesized compounds were characterized by 1H NMR, 13C NMR, UV/Vis, and IR spectroscopic methods as well as via MALDI‐TOF‐MS spectrometry (see Figures S1–S135 in Supporting Information).

UV/Vis spectra of the chromophore arrays were recorded in <span class="Chemical">CHCl3 or <class="Chemical">span class="Chemical">THF at room temperature. The free base dimers 26 and 51 illustrate a typical etio‐type porphyrin spectrum, having the Soret and four Q‐bands in decreasing intensity. The symmetrical zinc dimers 25, 28, 29, 50, 52, and 53 showed an absorbance maximum at 422 nm. The full width at half maxima (FWHM) of these dimers is nearly equal to 5,10,15,20‐tetraphenylporphyrin (H2TPP) or its zinc(II) complex (ZnTPP), displaying no evidence of exciton coupling between two porphyrin units, which supports the suggested potential trans conformation of one porphyrin unit with respect to another unit.22 The absorption spectra of ethynyl‐linked porphyrin dimers such as 28, 29, and 53 exhibited a 15–18 nm bathochromic shift compared to the phenylene‐linked dimers 25 and 50 due to the π‐extended ethynyl or phenylethynyl moieties. The UV/Vis spectra of ethynyl‐linked dimers (28, 29, and 53) exhibit nearly the same FWHM and λ max as compared to the precursor amine porphyrin (11 and 12). Similar λ max values of monomers and dimers indicate the lack of through space or through bond electronic communication between porphyrin units, that is, a trans orientation of the synthesized dimers.

Single crystal X‐ray analysis

The structure of compounds [5‐(2′‐amino<span class="Chemical">phenylacetylene)‐10,20‐bis(4′‐methyl<class="Chemical">span class="Chemical">phenyl)‐15‐phenylporphyrinato]zinc(II) (12), cubane 13, BCP 33, 35, 38, 45, 46 and dimethyl bicyclo[1.1.1]pentane‐1,3‐dicarboxylate were determined using single crystal X‐ray diffraction analysis. Structural parameter tables and refinement details (Table S1 and S2) are provided in the Supporting Information.23, 24

The crystal structure of <span class="Chemical">cubane scaffold 13 illustrates two types of intermolecular non‐covalent interactions (Figure 3). The structure exhibits a head‐to‐tail N1⋅⋅⋅O1=C interaction at a distance of 2.853 Å with an angle of 175.4°. Furthermore, the <class="Chemical">span class="Chemical">iodo atom at the para‐position of the phenylene moiety exhibits a head‐to‐tail halogen bond interaction with O2=C of the ester group with a distance of 3.074 Å and an angle of 170.1°. The observed halogen and hydrogen bond interactions are nearly orthogonal to each other. Interestingly, the combined and repetitive intermolecular halogen and hydrogen bond interactions result in a supramolecular 3D network between the cubane molecules directed by the substituents at 1,4‐bridgehead positions. There are only a few reports of oxygen‐iodine interactions,25 but the specific 3D‐orientation of cubane potentially favors this packing pattern enabling it to access this unusual interaction.

Figure 3

(a) Molecular structure of cubane 13. (b) Molecular arrangement of compound 13 in the crystal shows the non‐covalent interactions between N1⋅⋅⋅O1=C and C=O2⋅⋅⋅I1.

(a) Molecular structure of <span class="Chemical">cubane 13. (b) Molecular arrangement of compound 13 in the crystal shows the non‐covalent interactions between N1⋅⋅⋅O1=C and C=<class="Chemical">span class="Chemical">O2⋅⋅⋅I1.

The crystal structures of <span class="Chemical">BCP 33, 35, and 38 exhibit non‐covalent interactions between <class="Chemical">span class="Chemical">amide N‐donors and C=O acceptors within the crystal lattices. The nature of these interactions is dependent upon the substitution pattern at the phenylene ring. The crystal structure of para‐substituted BCP compound 33 reveals repetitive head‐to‐head N1⋅⋅⋅O1=C hydrogen‐bond interactions at distances of 2.970 Å (Figure 4). In contrast to 33, the crystal structure of meta‐substituted BCP 35 exhibits head‐to‐tail N1⋅⋅⋅O2=C interactions at distances of 3.061 Å, leading to the formation of a non‐covalently attached inversion‐centered dimer (Figures S138 and S139 in Supporting Information).

Figure 4

(a) Molecular structure of compound 33. (b) Molecular arrangement of compound 33 in the crystal shows the non‐covalent interaction between N1⋅⋅⋅O1.

Similarly, the crystal structure of bis‐meta‐substituted <span class="Chemical">BCP 38 shows head‐to‐tail interactions at distances of 2.910 Å and forms a supramolecular 3D network/array (Figure S141 in Supporting Information).

In nature, the 3D structures of proteins and other biomolecules are controlled using H‐bonding interactions between trans N−H and C=O moieties of amino acids and these 3D architectures are responsible for their specific biological functions. The substituents surrounding the <span class="Chemical">amide bonds direct the non‐covalent interactions in all of the above‐mentioned crystal structures, and this in<class="Chemical">span class="Chemical">dicates the possibility of potentially mimicking protein architecture with sp3 rigid scaffolds (BCP or cubane). This would provide the conformational space essential for protein function, while simultaneously providing amide bonds for “substrate” coordination.

The crystal structure of the <span class="Chemical">BCP‐<class="Chemical">span class="Chemical">porphyrin 46 illustrates the planar conformation of the macrocyclic core while the crystal packing of this molecule further shows intermolecular head‐to‐tail non‐covalent D⋅⋅⋅A interactions between the acceptor ZnII metal of the porphyrin and donor oxygen atom of the carbonyl group in the amide moiety at a distance of 2.191 Å (Figure 5). This particular interaction supports the proposed mechanism of binding between a transition metal(II) and the C=O moiety of the amide bond (vide infra). Similarly, the crystal structure of [5‐(2′‐aminophenylacetylene)‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (12) also exhibits head‐to‐tail D⋅⋅⋅A interactions, in this case between the donor N‐atom of the amine group from one porphyrin to the ZnII center of another (Figure S145 and S146 in the Supporting Information). This interaction is further supported by 1H NMR spectra where the ortho‐amine protons resonate at −0.58 ppm due to the shielding effect of the porphyrin ring current.

Figure 5

(a) Molecular structure of compound 46. (b) Intermolecular head‐to‐tail interaction between the Zn metal of the porphyrin unit (acceptor) and the C=O donor moiety of the amide bond.

(a) Molecular structure of compound 46. (b) Intermolecular head‐to‐tail interaction between the <span class="Chemical">Zn metal of the <class="Chemical">span class="Chemical">porphyrin unit (acceptor) and the C=O donor moiety of the amide bond.

Along with the above mentioned non‐covalent interactions, we also observed a unique example of a <span class="Chemical">porphyrin‐based ion pair complex, that is, a pair of opposite charges held together by Columbic interactions in the same solvent‐shell.26 Although charge‐separated ion pair complexes are quite common in transition‐<class="Chemical">span class="Chemical">metal organometallic chemistry, ion pair complexes of phlorins and porphodimethene‐based systems are also known, this type of interaction has not previously been observed for systems with intact porphyrin cores.27 The crystal structure of porphyrin 45 is unique as it exhibits an ion pair interaction between an axial chloride ligand and a [Et3NH]+ counter ion in the same unit cell without disturbing the aromatic 18π‐electron pathway (Figure 6). Axial coordination results in displacement of the ZnII ion from the 24‐atom mean plane by 0.51 Å. The chloride and triethylammonium ions exhibit an ion pair interaction at a distance of 3.043 Å. This is further supported by the 1H and 13C NMR spectra of compound 45 where the ratio of the porphyrin derivative and [Et3NH]+ was found to be 1:1. To best of our knowledge, it is the first example of a porphyrin‐based charge‐separated ion pair complex. Figure 6 illustrates an example of the [Et3NH]+ [porphyrin(ZnCl)]− ion pair in which a negatively charged porphyrin electrostatically interacts with positively charged triethylamine. In the crystal structure of 45, ZnII binds to the Cl− and the oxidation state of the Zn metal ion remains unchanged, the chloride ion shows noncovalent interaction with [Et3NH]+. Most of the reported examples of chloride coordinated ZnII porphyrinoids either fall into the class of 16 π electron macrocycles or N‐substituted porphyrins.27 In the case of N‐substituted porphyrins, the negative charge of the chloride is counter‐balanced by the positive charge on the tertiary core‐N‐atom whereas in present case charge is counter‐balanced by [Et3NH]+ and the porphyrin core remains intact making this an unique example.

Figure 6

(a) Molecular structure of compound 45. (b) Charge separated ion pair complex of porphyrin 45 and [HNEt3]+.

(a) Molecular structure of compound 45. (b) Charge separated ion pair complex of <span class="Chemical">porphyrin 45 and [H<class="Chemical">span class="Gene">NEt3]+.

Structure elucidation of <span class="Chemical">BCP‐<class="Chemical">span class="Chemical">porphyrin 45 revealed the nearly coplanar nature of the BCP‐appended arm with respect to the porphyrin plane. In contrast, BCP‐porphyrin 46, which has a larger distance between the BCP and porphyrin moieties, showed orthogonal rotation of the phenyl rings with respect to the porphyrin plane. Hence, 45 and its analogues show more promise towards the synthesis of cubane/BCP‐linked porphyrin systems for electron/energy studies owing to their extended conjugation.

Conclusion

We have designed, synthesized, and characterized bridgehead substituted <span class="Chemical">bicyclo[1.1.1]pentane and <class="Chemical">span class="Chemical">cubane derivatives via amide coupling reactions. This work demonstrates a broad substrate scope with over 35 new derivatives of cubane/BCP that were synthesized in moderate to good yields. The single crystal X‐ray structures of small rigid linker motifs (13, 33, 35, and 38) revealed supramolecular 3D networks with combined and repetitive inter‐ and intramolecular H‐bonding interactions. Significantly, the crystal structure of cubane 13 showed an unusual C=O2⋅⋅⋅I1 interaction along with the usual N1⋅⋅⋅O1=C interaction to result in a 3D cage‐like structure. The formation of 3D supramolecular network dependent on the structurally pre‐organized BCP/cubane scaffold in association with the semi‐rigid amide moieties.

The crystal structure of <span class="Chemical">porphyrin 45 illustrates a unique example of <class="Chemical">span class="Chemical">porphyrin based ion‐pair complex. Additionally, porphyrin 46 exhibits non‐covalent D⋅⋅⋅A interactions between the acceptor ZnII metal of the porphyrin and the donor oxygen atom of the carbonyl group in the amide moiety in solid‐state. A follow‐up study on selective detection of small molecular motifs via this type of arrays is underway and will be reported separately.

Experimental Section

General information, instrumentation, synthesis of precursors, crystallographic studies, and complete synthetic details of all synthesized compounds are given in Supporting Information.

General procedures

General procedure 1 for <span class="Chemical">amide condensation reactions: 4‐(Methoxy<class="Chemical">span class="Chemical">carbonyl)cubane‐1‐carboxylic acid (1) (1.0 equiv) or cubane‐1,4‐dicarboxylic acid (2) (1.0 equiv) was placed in oven‐dried microwave vial and heated under vacuum. The reaction flask was purged with argon, anhydrous DMF (0.25 mL) was added and the reaction mixture was heated slightly to dissolve the cubane. HATU (1.3/2.6 equiv), HOAt (1.3/2.6 equiv) and DIPEA (4.0/8.0 equiv) were then added and the reaction mixture was left to stir at rt. for 30 minutes under argon. The amine (2.0 equiv) was added under an argon flow to the flask alongside additional anhydrous DMF (0.25 mL). The reaction mixture was stirred at RT for a further 24 h and then diluted with H2O.

General procedure 2 for <span class="Chemical">amide condensation reactions: In an oven‐dried microwave vial, a drop of <class="Chemical">span class="Chemical">DMF was added to the solution of 3‐(methoxycarbonyl)bicyclo[1.1.1]pentane‐1‐carboxylic acid (1.0 equiv) (30) or bicyclo[1.1.1]pentane‐1,3‐dicarboxylic acid (1.0 equiv) (31) in CH2Cl2. Oxalyl chloride (1.2 equiv/2.2 equiv) was added dropwise to above solution at 0 °C. The reaction mixture was warmed to 40 °C and stirred for 2 h under inert atmosphere. The reaction mixture was cooled to 0 °C. NEt3 (3.0/6.0 equiv) followed by substituted aniline (1.1/2.0 equiv) were added slowly to the reaction mixture. The reaction vial was warmed to 40 °C and stirred for 2 h under argon. The solvent was evaporated in vacuo, crude reaction mixture was recrystallized from CH2Cl2/hexane. The desired product was separated as white crystalline material.

General procedure 3 to synthesize ‐ethynyl<span class="Chemical">amine substituted <class="Chemical">span class="Chemical">porphyrins 9–12: Iodo porphyrin (1.0 equiv) was placed in an oven‐dried Schlenk flask and heated under vacuum. The reaction flask was purged with argon and a mixture of THF/NEt3 (3:1) was added. Argon was bubbled through the solution for 15 min then ethynylaniline (5.0 equiv), PdCl2(PPh3)2 (0.15 equiv) and CuI (0.3 equiv) were added. The reaction mixture was heated to 70 °C and allowed to stir for 4 h. The reaction mixture was diluted with CH2Cl2 (10 mL) followed by removal of solvents in vacuo. Crude reaction mixture was purified by silica gel column chromatography.

General procedure 4 for <span class="Chemical">Sonogashira cross‐coupling using ‐<class="Chemical">span class="Chemical">ethynyl porphyrin: An oven‐dried Schlenk tube charged with ethynyl porphyrin (1.0 equiv) and iodo‐substituted cubane or BCP was heated under vacuum. THF (5 mL) followed by NEt3 (2.5 mL) were added to reaction vessel. Argon was bubbled through the solution for 10–15 min. and PdCl2(PPh3)2 (0.2 equiv) and CuI (0.3 equiv) were added. The resulting reaction mixture was heated at 40 °C and progress of the reaction was monitored by TLC. Reaction mixture was filtered through a Celite pad. Solvent was evaporated in vacuo, crude reaction mixture was purified by silica gel column chromatography.

General procedure 5 for Suzuki cross‐coupling: To an oven‐dried Schlenk tube charged with <span class="Chemical">porphyrin (2.1 equiv), <class="Chemical">span class="Chemical">BCP linker (1.0 equiv) and K3PO4 (10.0 equiv) anhydrous DMF (5 mL) was added under inert atmosphere. The above solution was purged with argon for further 15 min followed by addition of 0.2 equiv of Pd(PPh3)4. The reaction mixture was heated to 100 °C and allowed to stir for 18 h. The solvent was removed in vacuo, crude reaction mixture was dissolved in CH2Cl2 washed with NaHCO3 followed by brine. Organic layer was extracted with CH2Cl2. Extracted organic phases were combined and solvent was evaporated. The resulting crude reaction mixture was purified by silica gel column chromatography.

Synthesis of cubane linkers 13–18

Methyl‐4‐((4′‐<span class="Chemical">iodo<class="Chemical">span class="Chemical">phenyl)carbamoyl)cubane‐1‐carboxylate (13): Synthesized via General Procedure 1 from 4‐(methoxycarbonyl)cubane‐1‐carboxylic acid (50 mg, 240 μmol), 4‐iodoaniline (160 mg, 730 μmol), HATU (119 mg, 310 μmol), HOAt (42.5 mg, 310 μmol) and DIPEA (17 μL) in anhydrous DMF (0.5 mL). The product was extracted with a mixture of CH2Cl2/MeOH (×3), dried over MgSO4 and the solvent removed under reduced pressure, the crystals were washed with CH2Cl2 to remove any remaining aniline and dried under reduced pressure. The product was obtained as white crystals. Yield: 120 mg, 61 %; m.p.: 240–245 °C; R f=0.35 (SiO2, EtOAc/hexane, 2:3, v/v); 1H NMR (600 MHz, [D6]DMSO): δ=9.77 (s, 1 H), 7.63 (d, J=8.6 Hz, 2 H), 7.50 (d, J=8.6 Hz, 2 H), 4.29–4.22 (m, 3 H), 4.18–4.15 (m, 3 H), 3.64 ppm (s, 3 H); 13C NMR (151 MHz, [D6]DMSO): δ=171.3, 169.5, 138.8, 137.2, 121.8, 86.8, 57.8, 54.9, 51.3, 46.5, 46.0 ppm; IR (neat): =1720 (m), 1644 (m), 1581 (m), 1512 (m), 1390 (m), 1322 (m), 1219 (w), 1169 (w), 1088 (m), 824 (s), 792 (s), 710 (m), 598 cm−1 (m); HRMS (APCI): m/z: calcd for C17H13INO3 [M−H]− 405.994565, found 405.993716.

Methyl‐4‐((4′‐ethynyl<span class="Chemical">phenyl)carbamoyl)<class="Chemical">span class="Chemical">cubane‐1‐carboxylate (14): Synthesized via General Procedure 1 from 4‐(methoxycarbonyl)cubane‐1‐carboxylic acid (15 mg, 70 μmol), HATU (43.5 mg, 114 μmol), HOAt (15.5 mg, 114 μmol), DIPEA (61 μL), 4‐ethynylaniline (25 mg, 210 μmol) in anhydrous DMF (0.5 mL). The product was extracted with a mixture of CH2Cl2/MeOH (×3), dried over MgSO4 and the solvent removed under reduced pressure, the crystals were washed with CH2Cl2 to remove any remaining aniline and dried under reduced pressure to afford white crystals. Yield: 8 mg, 37 %; m.p.: 243–247 °C; R f=0.67 (SiO2, EtOAc/hexane, 1:1, v/v); 1H NMR (600 MHz, [D6]DMSO): δ=9.86 (s, 1 H), 7.69 (d, J=8.5 Hz, 2 H), 7.41 (d, J=8.5 Hz, 2 H), 4.26 (t, J=4.6 Hz, 3 H), 4.17 (t, J=4.7 Hz, 3 H), 4.07 (s, 1 H), 3.64 ppm (s, 3 H); 13C NMR (151 MHz, [D6]DMSO): δ=171.2, 169.6, 139.6, 132.2, 119.3, 116.1, 83.6, 79.8, 57.8, 54.8, 51.3, 46.6, 46.0 ppm; IR (neat): =3252 (m), 2993 (w), 2950 (w), 1721 (s), 1645 (s), 1585 (s), 1509 (s), 1401 (m), 1336 (s), 1288 (m), 1221 (m), 1090 (s), 931 (w), 833 (s), 721 (s), 671 cm−1 (m); HRMS (APCI): m/z: calcd for C19H16NO3 [M+H]+ 306.112470; found 306.113336.

, ‐Bis(4′‐<span class="Chemical">iodo<class="Chemical">span class="Chemical">phenyl)cubane‐1,4‐dicarboxamide (15): Synthesized via General Procedure 1 from cubane‐1,4‐dicarboxylic acid (46 mg, 240 μmol), 4‐iodoaniline (263 mg, 1.2 mmol), HATU (119 mg, 310 μmol), HOAt (42.5 mg, 310 μmol) and DIPEA (17 μL) in anhydrous DMF (0.5 mL). The reaction mixture was diluted with H2O and CH2Cl2 causing white crystals to crash out of the solution. The product was collected by vacuum filtration, washed with CH2Cl2 to remove unreacted aniline, and dried under reduced pressure to obtain white crystals. Yield: 55 mg, 39 %; m.p.: 257–259 °C; R f=0.37 (SiO2, hexane/EtOAc, 1:3, v/v); 1H NMR (400 MHz, [D6]DMSO): δ=9.77 (s, 2 H), 7.64 (d, J=8.6 Hz, 4 H), 7.52 (d, J=8.6 Hz, 4 H), 4.24 ppm (s, 6 H); 13C NMR (151 MHz, [D6]DMSO) : δ=169.9, 138.9, 137.2, 121.8, 86.7, 57.6, 46.3 ppm; IR (neat): =3342 (w), 2985 (w), 1738 (w), 1645 (s), 1588 (m), 1505 (s), 1390 (s), 1324 (m), 1289 (w), 1243 (m), 1217 (w), 1061 (w), 1007 (m), 955 (w), 809 (s), 795 (m), 669 (m), 610 cm−1 (w); HRMS (APCI): m/z: calcd for C22H15I2N2O2 [M−H]− 592.922847; found 592.922494.

, ‐Bis(3′‐<span class="Chemical">iodo<class="Chemical">span class="Chemical">phenyl)cubane‐1,4‐dicarboxamide (16): Synthesized via General Procedure 2 from cubane‐1,4‐dicarboxylic acid (46 mg, 240 μmol), Oxalyl chloride (45 μL, 530 μmol), NEt3 (0.13 mL, 960 μmol) and 3‐iodoaniline (64 μL, 530 μmol) in DMF (0.25 mL) and CH2Cl2 (1.5 mL). Solvents were evaporated in vacuo and resulting solid was washed with CH2Cl2 to give the product as white crystals. Yield: 44 mg, 31 %; m.p.: 243–248 °C; R f=0.37 (SiO2, EtOAc/hexane 3:1, v/v); 1H NMR (600 MHz, [D6]DMSO): δ=9.75 (s, 2 H), 8.13 (s, 2 H), 7.70 (d, J=8.2 Hz, 2 H), 7.41 (d, J=8.2 Hz, 2 H), 7.12 (t, J=8.2 Hz, 2 H), 4.25 ppm (s, 6 H); 13C NMR (151 MHz, [D6]DMSO): δ=169.9, 140.5, 131.7, 130.7, 127.7, 118.7, 94.4, 57.5, 46.3 ppm; IR (neat): =3200 (w), 2996 (w), 1738 (w), 1642 (s), 1580 (s), 1537 (m), 1474 (s), 1406 (m), 1333 (m), 1287 (w), 1242 (w), 1197 (w), 1092 (w), 996 (w), 947 (w), 901 (w), 865 (w), 845 (w), 772 (s), 721 (w), 681 (m), 657 (w), 615 (w), 572 cm−1 (w); HRMS (APCI): m/z: calcd for C22H17I2N2O2 [M+H]+ 594.937400; found 594.937107.

, ‐Bis(4′‐ethynyl<span class="Chemical">phenyl)<class="Chemical">span class="Chemical">cubane‐1,4‐dicarboxamide (17): Synthesized via General Procedure 1 from cubane‐1,4‐dicarboxylic acid (30 mg, 157 μmol), HATU (156 mg, 410 μmol), HOAt (56 mg, 410 μmol), DIPEA (219 μL) and 4‐ethynylaniline (55 mg, 470 μmol) in DMF (0.5 mL). The reaction mixture was diluted with CH2Cl2 causing the product to crash out of the solution. The product was collected by vacuum filtration, washed with CH2Cl2 to remove any leftover aniline, and dried under reduced pressure to obtain white crystals. Yield: 39 mg, 67 %; m.p.: 247–252 °C; R f=0.74 (SiO2, EtOAc/hexane, 3:1, v/v); 1H NMR (600 MHz, [D6]DMSO): δ=9.84 (s, 2 H), 7.71 (d, J=8.5 Hz, 4 H), 7.42 (d, J=8.5 Hz, 4 H), 4.26 (s, 6 H), 4.08 ppm (s, 2 H); 13C NMR (151 MHz, [D6]DMSO): δ=169.9, 139.6, 132.2, 119.3, 116.1, 83.6, 79.8, 57.5, 46.3 ppm; IR (neat): =3283 (m), 3218 (w), 3086 (w), 3001 (w), 1650 (s), 1590 (s), 1510 (s), 1404 (s), 1338 (s), 1290 (m), 1252 (s), 1090 (m), 944 (m), 877 (m), 840 (s), 770 (m), 667 (m), 619 cm−1 (s); HRMS (APCI): m/z: calcd for C26H19N2O2 [M+H]+: 391.144104, found 391.143171.

, ‐Bis(3′‐ethynyl<span class="Chemical">phenyl)<class="Chemical">span class="Chemical">cubane‐1,4‐dicarboxamide (18): Synthesized via General Procedure 1 from cubane‐1,4‐dicarboxylic acid (15 mg, 78 μmol), HATU (77 mg, 200 μmol), HOAt (27 mg, 200 μmol), DIPEA (108 μL) and 3‐ethynylaniline (27 μL, 234 μmol) in anhydrous DMF (1 mL). The reaction mixture was diluted with H2O and CH2Cl2 causing white crystals to crash out of the solution. The product was collected by vacuum filtration, washed with CH2Cl2 to remove any leftover aniline, and dried under reduced pressure to obtain white crystals. Yield: 36 mg, 50 %; m.p.: 297–302 °C (charred); R f=0.69 (SiO2, EtOAc/hexane, 3:1, v/v); 1H NMR (600 MHz, [D6]DMSO): δ=9.76 (s, 2 H), 7.86 (s, 2 H), 7.69 (d, J=7.9 Hz, 2 H), 7.33 (t, J=7.9 Hz, 2 H), 7.16 (d, J=7.9 Hz, 2 H), 4.26 (s, 6 H), 4.17 ppm (s, 2 H); 13C NMR (151 MHz, [D6]DMSO): δ=169.9, 139.3, 129.1, 126.4, 122.4, 121.8, 120.2, 83.4, 80.4, 57.5, 46.3, 45.9 ppm; IR (neat): =3312 (w), 3218 (w), 3048 (w), 2999 (w), 1649 (m), 1603 (m), 1524(m), 1480 (s), 1406 (s), 1331 (s), 1298 (m), 1225 (m), 1086 (w), 950 (m), 859 (m), 782 (s), 683 (s), 599 cm−1 (s); HRMS (APCI): m/z: calcd for C26H19N2O2 [M+H]+ 391.144104; found 391.143981.

Synthesis of cubane porphyrin dimers 25–29

, ‐Bis[4′‐{(10′′,15′′,20′′‐tri<span class="Chemical">phenyl<class="Chemical">span class="Chemical">porphyrinato)zinc(II)‐5′′‐yl}‐phenyl]cubane‐1,4‐dicarboxamides (25): Synthesized via General Procedure 1 from cubane‐1,4‐dicarboxylic acid (15 mg, 80 μmol), [5‐(4′‐aminophenyl)‐10,15,20‐triphenylporphyrinato]zinc(II) (8) (110 mg, 160 μmol), HATU (79 mg, 210 μmol), HOAt (28.5 mg, 210 μmol) and DIPEA (111 μL) in anhydrous DMF (0.5 mL). H2O was added and the product was extracted with CH2Cl2/MeOH (×3), washed with H2O (×4), dried over MgSO4 and the solvent removed under reduced pressure. The crude material was purified by column chromatography (SiO2, CH2Cl2/(CH3)2CO, 100:0 to 98.8:0.02). The product was obtained as purple crystals. Yield: 35 mg, 28 %; m.p.: >350 °C; R f=0.71 (SiO2, CH2Cl2/(CH3)2CO, 20:1, v/v); 1H NMR (600 MHz, CDCl3/[D8]THF): δ=8.90 (dd, J=14.4, 4.5 Hz, 8 H), 8.86 (s, 8 H), 8.21–8.19 (m, 16 H), 7.99 (s, 2 H), 7.98 (s, 4 H), 7.75–7.70 (m, 18 H), 4.58 ppm (s, 6 H); 13C NMR (151 MHz, CDCl3/[D8]THF): δ=169.9, 150.2, 150.1, 143.4, 139.6, 137.2, 135.2, 135.2, 134.6, 134.6, 131.7, 127.3, 126.5, 120.8, 120.1, 117.8, 60.5, 58.9, 47.2 ppm; IR (neat): =1736 (w), 1660 (w), 1594 (w), 1486 (m), 1439 (w), 1398 (w), 1338 (w), 1235 (w), 1203 (w), 1174 (w), 1067 (w), 993 (s), 796 (s), 749 (m), 718 (m), 701 (s), 569 cm−1 (w); UV/Vis (CHCl3): λ max (logϵ) = 422 (6.19), 549 (4.80), 589 nm (4.15); HRMS (MALDI‐TOF): m/z: calcd for C98H62N10O2Zn2 [M]+ 1538.3640; found 1538.3662.

, ‐Bis[4′‐{(10′′,15′′,20′′‐tri<span class="Chemical">phenyl<class="Chemical">span class="Chemical">porphyrin)‐5′′‐yl}‐phenyl]cubane‐1,4‐dicarboxamides (26): Synthesized via General Procedure 1 from cubane 2 (50 mg, 69 μmol), 5‐(4′‐aminophenyl)‐10,15,20‐triphenylporphyrin (7) (129 mg, 210 μmol), HATU (34.1 mg, 90 μmol), HOAt (12.2 mg, 90 μmol) and DIPEA (48 μL) in anhydrous DMF (0.5 mL). H2O was added and the product was extracted with CH2Cl2 (×3), washed with H2O (×4), dried over MgSO4 and the solvent removed under reduced pressure. The crude material was purified by column chromatography (SiO2, CH2Cl2/(CH3)2CO, 100:0 to 98.8:0.02). The product was obtained as purple crystals. Yield: 55 mg, 56 %; m.p.: >350 °C; R f=0.52 (SiO2, CH2Cl2/EtOAc, 40:1, v/v); 1H NMR (600 MHz, CDCl3): δ=8.87 (d, J=3.4 Hz, 8 H), 8.85 (s, 8 H), 8.23–8.22 (m, 16 H), 8.02 (d, J=7.8 Hz, 2 H), 7.78–7.75 (m, 20 H), 7.58 (s, 2 H), 4.63 (s, 6 H), −2.76 ppm (s, 4 H); 13C NMR (151 MHz, CDCl3): δ=189.7, 142.3, 135.4, 134.7, 127.9, 126.8, 120.4, 118.1, 47.3 ppm; IR (neat): =1674 (w), 1584 (w), 1494 (w), 1397 (w), 1317 (w), 1190 (w), 965 (m), 798 (s), 753 (m), 722 (m), 701 (s); UV/Vis (CH2Cl2): λ max (logϵ) = 422 (6.01), 518 (4.65), 554 (4.40), 593 (4.29), 649 nm cm−1 (4.21); HRMS (MALDI‐TOF): m/z: calcd for C98H67N10O2 [M+H]+: 1415.5448, found 1415.5514.

‐[4′‐{(10′′,20′′,15′′‐Tri<span class="Chemical">phenyl<class="Chemical">span class="Chemical">porphyrinato)zinc(II)‐5′‐yl}phenyl]‐ ‐[4′‐{(10′′,20′′,15′′‐triphenylporphyrin)‐5′‐yl}phenyl]cubane‐1,4‐dicarboxamide (27): Synthesized via General Procedure 1 from compound 22 (30 mg, 37 μmol), 5‐(4‐aminophenyl)‐10,15,20‐triphenylporphyrinato zinc(II) (8) (31 mg, 45 μmol), HATU (43.5 mg, 114 μmol), HOAt (15.5 mg, 114 μmol) and DIPEA (61 μL) in anhydrous DMF (0.5 mL). The reaction mixture washed with brine and the products were extracted with a mixture of CH2Cl2/THF (×3), dried over MgSO4 and the solvent removed under reduced pressure. The crude material was purified by column chromatography (SiO2, CH2Cl2/(CH3)2CO, 100:0 to 98.8:0.02). The product was recrystallized from CH2Cl2/CH3OH and obtained as purple crystals. Yield: 28 mg, 51 %; m.p.: >350 °C; R f=0.64 (SiO2, (CH3)2CO/CH2Cl2, 1:20, v/v); 1H NMR (600 MHz, [D6]DMSO): δ=10.21 (s, 1 H), 10.16 (s, 1 H), 8.92 (s, 2 H), 8.86–8.84 (m, 8 H), 8.80–8.78 (m, 6 H), 8.25–8.15 (m, 20 H), 7.83 (dd, J=25.5, 5.4 Hz, 18 H), 4.52 (s, 6 H), −2.88 ppm (s, 2 H); 13C NMR (151 MHz, [D6]DMSO): δ=170.1, 149.5, 149.3, 149.2, 142.8, 141.2, 134.6, 134.4, 134.2, 134.2, 131.5, 128.1, 127.4, 127.0, 126.6, 120.3, 120.0, 117.9, 117.7, 46.6 ppm; IR (neat): =1658 (w), 1596 (w), 1489 (m), 1400 (w), 1320 (w), 1179 (w), 1071 (w), 1002 (m), 994 (m), 796 (s), 718 (m), 700 (s), 563 cm−1 (w); UV/Vis (CHCl3): λ max (logϵ)=422 (5.79), 451 (5.66), 550 (4.43), 671 nm (4.81); HRMS (MALDI‐TOF): m/z: calcd for C98H64N10O2Zn [M]+ 1476.4505; found 1476.4495.

, ‐Bis[3′‐{(10′′,20′′‐bis(4′‐methyl<span class="Chemical">phenyl)‐15′′‐<class="Chemical">span class="Chemical">phenylporphyrinato)zinc(II)‐5′′‐yl}phenylacetylene]cubane‐1,4‐dicarboxamide (28): Synthesized via General Procedure 1 from cubane‐1,4‐dicarboxylic acid (10.5 mg, 55 μmol) (2), porphyrin 11 (85 mg, 110 μmol), HATU (54.4 mg, 143 μmol), HOAt (19.5 mg, 143 μmol) and DIPEA (76 μL) in anhydrous DMF (0.5 mL). The reaction mixture was then washed with brine and the products were extracted with a mixture of CH2Cl2/MeOH (×3), dried over MgSO4 and the solvent removed under reduced pressure. The crude material was purified by column chromatography (SiO2, CH2Cl2:(CH3)2CO,100:0 to 98.8:0.02). The product was recrystallized from CH2Cl2/CH3OH and obtained as purple crystals. Yield=32 mg, 36 %; m.p.: >350 °C; R f=0.33 (SiO2, CH2Cl2/(CH3)2CO, 20:1, v/v); 1H NMR (600 MHz, CDCl3): δ=9.77 (d, J=4.4 Hz, 4 H), 8.97 (d, J=4.4 Hz, 4 H), 8.80 (dd, J=21.3, 4.5 Hz, 8 H), 8.19 (s, 1 H), 8.16 (d, J=4.4 Hz, 4 H), 8.08 (d, J=7.2 Hz, 8 H), 7.80–7.77 (m, 3 H), 7.74–7.69 (m, 8 H), 7.59 (s, 1 H), 7.55 (d, J=7.2 Hz, 8 H), 7.52–7.49 (m, 3 H), 4.50 (s, 6 H), 2.71 ppm (s, 12 H); 13C NMR (151 MHz, CDCl3): δ=169.7, 152.3, 150.7, 150.0, 149.9, 143.2, 140.1, 138.1, 137.1, 134.6, 134.5, 132.8, 131.9, 131.7, 130.5, 129.5, 127.4, 127.3, 126.5, 125.4, 122.7, 122.5, 121.9, 119.7, 98.8, 95.2, 93.9, 67.7, 58.8, 47.1, 21.7 ppm; UV/Vis (THF): λ max (logϵ)=443 (6.13), 557 (4.65), 624 nm (4.94); IR (neat): =1650 (w), 1598 (w), 1519 (w), 1483 (m), 1401 (w), 1339 (m), 1305 (w), 1207 (m), 1180 (w), 1064 (w), 996 (s), 845 (w), 792 (s), 714 (m), 701 (m), 682 (m), 569 cm−1 (m); HRMS (MALDI‐TOF): m/z: calcd for C106H70N10O2Zn2 [M]+ 1642.4266; found 1642.4296.

, ‐Bis[2′‐{(10′′,20′′‐bis(4′‐methyl<span class="Chemical">phenyl)‐15′′‐<class="Chemical">span class="Chemical">phenylporphyrinato)zinc(II)‐5′′‐yl}phenylacetylene]cubane‐1,4‐dicarboxamide (29): Synthesized via General Procedure 1 from cubane‐1,4‐dicarboxylic acid (8.4 mg, 44 μmol) (2), porphyrin 12 (65 mg, 87 μmol), HATU (43.5 mg, 114 μmol), HOAt (15.5 mg, 114 μmol) and DIPEA (61 μL) in anhydrous DMF (0.5 mL). The reaction mixture was then washed with brine and the products were extracted with a mixture of CH2Cl2/MeOH (×3), dried over MgSO4 and the solvent removed under reduced pressure. The crude material was purified by column chromatography (SiO2, CH2Cl2:(CH3)2CO, 100:0 to 98.8:0.02). The product was recrystallized from CH2Cl2/CH3OH and obtained as purple crystals. Yield: 36 mg, 50 %; m.p.: >350 °C; R f=0.75 (SiO2, CH2Cl2/(CH3)2CO, 40:1, v/v); 1H NMR (600 MHz, [D8]THF): δ=9.61 (d, J=4.4 Hz, 4 H), 8.91 (d, J=4.4 Hz, 4 H), 8.75 (dd, J=11.1, 4.4 Hz, 10 H), 8.43 (d, J=8.1 Hz, 2 H), 8.15 (d, J=6.4 Hz, 4 H), 8.03 (d, J=7.6 Hz, 8 H), 7.95 (d, J=6.8 Hz, 2 H), 7.74 (dt, J=13.9, 7.0 Hz, 6 H), 7.51 (d, J=7.5 Hz, 8 H), 7.37 (t, J=6.8 Hz, 2 H), 7.22 (t, J=6.8 Hz, 2 H), 3.81 (s, 6 H), 2.60 ppm (s, 12 H); 13C NMR (151 MHz, [D8]THF): δ=170.0, 153.0, 151.8, 150.9, 146.7, 144.3, 141.1, 138.1, 135.4, 135.3, 133.7, 132.6, 132.4, 132.3, 130.8, 130.3, 128.2, 127.4, 124.0, 123.2, 120.7, 114.8, 101.1, 98.11, 91.6, 86.1, 59.7, 47.8, 21.6 ppm; IR (neat): =3380 (w), 2920 (w), 2187 (w), 1652 (m), 1574 (m), 1510 (m), 1313 (m), 1206 (m), 1063 (m), 995 (s), 944 (m), 794 (s), 755 (s), 715 (m), 596 cm−1 (m); UV/Vis (THF): λ max (logϵ)=439 (5.92), 574 (4.53), 622 nm (4.72); HRMS (MALDI‐TOF): m/z: calcd for C106H70N10O2Zn2 [M]+ 1642.4266; found 1642.4304.

Synthesis of BCP linkers 32–39

Methyl‐3‐((4′‐<span class="Chemical">iodo<class="Chemical">span class="Chemical">phenyl)carbamoyl)bicyclo[1.1.1]pentane‐1‐carboxylate (32): Synthesized according to General Procedure 2 using compounds 3‐(methoxycarbonyl)bicyclo[1.1.1]pentane‐1‐carboxylic acid (30) (52.0 mg, 0.306 mmol), oxalyl chloride (32.0 μL, 0.378 mmol), NEt3 (130 μL, 0.934 mmol), 4‐iodoaniline (77.8 mg, 0.355 mmol). The solvent was removed in vacuo, crude product was recrystallized from CH2Cl2/hexane to afford titled compound as off‐white powder. Yield: 65 mg, 57 %; m.p.: 206 °C; R f=0.75 (SiO2, hexane/EtOAc, 7:3, v/v); 1H NMR (400 MHz; CDCl3): δ=7.60 (d, J=8.8 Hz, 2 H), 7.34 (br s, 1 H), 7.30 (d, J=8.8 Hz, 2 H), 3.70 (s, 3 H), 2.36 ppm (s, 6 H); 13C NMR (100 MHz; CDCl3): δ=169.5, 167.4, 137.8, 136.8, 121.6, 87.9, 52.4, 51.9, 40.0, 36.5 ppm; IR(neat): =3279 (w), 1723 (m), 1653 (s), 1593 (m), 1526 (s), 1392 (m), 1310 (s), 1214 (s), 1044 (m), 812 (s), 785 (s), 691 cm−1 (s); HRMS(APCI): m/z: calcd for C14H15INO3 + [M+H]+, 372.0091; found 372.0091.

Methyl‐3‐((4′‐ethynyl<span class="Chemical">phenyl)carbamoyl)<class="Chemical">span class="Chemical">bicyclo[1.1.1]pentane‐1‐carboxylate (33): Synthesized according to General Procedure 2 using compounds 3‐(methoxycarbonyl)bicyclo[1.1.1]pentane‐1‐carboxylic acid (30) (80.0 mg, 0.47 mmol), oxalyl chloride (47.0 μL, 0.56 mmol), NEt3 (200 μL, 1.4 mmol), 4‐ethynylaniline (60 mg, 0.47 mmol). The solvent was removed in vacuo, crude product was recrystallized from CH2Cl2/hexane to afford titled compound as an off‐white powder. Yield: 77 mg, 61 %; m.p.: 216 °C; R f=0.25 (SiO2, hexane/EtOAc, 7:3, v/v); 1H NMR (400 MHz; CDCl3): δ=7.49 (d, J=8.0 Hz, 2 H), 7.43 (d, J=8.0 Hz, 2 H), 7.23 (brs, 1 H), 3.69 (s, 3 H), 3.03 (s, 1 H), 2.36 ppm (s, 6 H); 13C NMR (100 MHz; CDCl3): δ=169.5, 167.1, 137.6, 133.0, 119.3, 118.1, 83.2, 52.4, 52.0, 40.1, 36.7 ppm; IR(neat): =3281 (w), 3242 (m), 1718 (m), 1651 (m), 1587 (m), 1506 (m), 1312 (s), 1217 (s), 1043 (w), 943 (s), 826 (s), 721 (m), 677 cm−1 (m); HRMS(APCI): m/z: calcd for (C16H14NO3 [M−H]−) 268.0974; found 268.0984; calcd for (C16H15ClNO3 [M+Cl]−) 304.0746; found 304.0754.

Methyl‐3‐((3′‐<span class="Chemical">iodo<class="Chemical">span class="Chemical">phenyl)carbamoyl)bicyclo[1.1.1]pentane‐1‐carboxylate (34): Synthesized according to General Procedure 2 using 30 (80.0 mg, 0.47 mmol), oxalyl chloride (47.0 μL, 0.56 mmol), NEt3 (200 μL, 1.4 mmol), 3‐iodoaniline (57.0 μL, 0.47 mmol). The solvent was removed in vacuo, crude product was recrystallized from CH2Cl2/hexane to afford titled compound as white powder. Yield: 90 mg, 52 %; m.p.: 198 °C; R f=0.35 (SiO2, hexane/EtOAc, 7:3, v/v); 1H NMR (400 MHz; CDCl3): δ=7.93 (t, J=1.7 Hz, 1 H), 7.56 (d, J=12 Hz, 1 H), 7.48 (d, J=7.9 Hz, 1 H), 7.14 (brs, 1 H), 7.07(t, J=8 Hz, 1 H), 3.74 (s, 3 H), 2.40 ppm (s, 6 H); 13C NMR (100 MHz; CDCl3): δ=169.4, 167.2, 138.4, 133.7, 130.5, 128.3, 118.8, 94.1, 52.4, 51.9, 39.9 ppm; IR(neat): =3276 (w), 1653 (s), 1525 (m), 1588 (s), 1525 (m), 1415 (s), 1302 (s), 1212 (s), 1043 (m), 883 (m), 775 (s), 653 cm−1 (s); HRMS(APCI): m/z: calcd for C14H13INO3 [M−H]− 369.9940; found 369.9954.

Methyl‐3‐((3′‐ethynyl<span class="Chemical">phenyl)carbamoyl)<class="Chemical">span class="Chemical">bicyclo[1.1.1]pentane‐1‐carboxylate (35): Synthesized according to General Procedure 2 using 30 (80.0 mg, 0.47 mmol), oxalyl chloride (47.0 μL, 0.56 mmol), NEt3 (200 μL, 1.4 mmol), 3‐ethynylaniline (58 μL, 0.47 mmol). The solvent was removed in vacuo, crude product was recrystallized from CH2Cl2/hexane to afford titled compound as white powder. Titled compound was obtained by recrystallization from CH2Cl2/hexane. Yield: 62 mg, 49 %; m.p.: 185 °C; R f=0.30 (SiO2, hexane/EtOAc 7:3, v/v); 1H NMR (400 MHz; [D6]DMSO): δ=9.73 (s, 1 H), 7.81 (t, J=1.7 Hz, 1 H), 7.65 (d, J=9.4 Hz, 1 H), 7.33 (t, J=7.9 Hz, 1 H), 7.17 (dt, J=7.8, 1.2 Hz, 1 H), 4.17 (s, 1 H), 3.64 (s, 3 H), 2.30 ppm (s, 6 H); 13C NMR (101 MHz; [D6]DMSO): δ=169.8, 167.9, 139.2, 129.5, 127.2, 123.1, 122.3, 120.8, 83.7, 81.0, 52.4, 52.0, 40.6, 40.4, 40.1, 39.9, 39.8, 39.6, 39.4, 36.8 ppm; IR(neat): =3374 (w), 3193 (w), 1713 (m), 1672 (m), 1603 (m), 1406 (m), 1307 (s), 1213 (s), 1054 (w), 862 (w), 791 (s), 686 (s), 630 cm−1 (s); HRMS(APCI): m/z: calcd for C16H14NO3 [M−H]− 268.0974; found. 268.0985.

, ‐Bis(4′‐<span class="Chemical">iodo<class="Chemical">span class="Chemical">phenyl)bicyclo[1.1.1]pentane‐1,3‐dicarboxamide (36): Synthesized according to General Procedure 2 using 31 (70 mg, 0.45 mmol), oxalyl chloride (85.0 μL, 0.99 mmol), NEt3 (0.37 mL, 2.7 mmol) and 4‐iodoaniline (207 mg, 0.98 mmol). The reaction solvent was removed in vacuo and the resulting residue was washed with CH2Cl2, and the insoluble material was collected to yield the desired product as a white solid. Yield: 180 mg, 72 %; m.p.: 301 °C; 1H NMR (400 MHz; [D6]DMSO): δ=9.72 (s, 2 H), 7.63 (d, J=8 Hz, 4 H), 7.49 (d, J=12 Hz, 4 H), 2.31 ppm (s, 6 H); 13C NMR (100 MHz; [D6]DMSO): δ=168.3, 138.9, 137.6, 122.4, 87.5, 52.1, 39.2 ppm; IR(neat): =3321 (w), 1666 (s), 1584 (w), 1502 (s), 1387 (m), 1307 (m), 1004 (m), 814 (s), 661 cm−1 (m); HRMS(APCI): m/z: calcd for C19H17I2N2O2 [M+H]+ 558.9374; found 558.9370.

, ‐Bis(4′‐ethynyl<span class="Chemical">phenyl)<class="Chemical">span class="Chemical">bicyclo[1.1.1]pentane‐1,3‐dicarboxamide (37): Synthesized according to General Procedure 2 using 31 (50 mg, 0.32 mmol), oxalyl chloride (60.0 μL, 0.64 mmol), NEt3 (0.28 mL, 2.7 mmol) and 4‐ethynylaniline (78 mg, 0.64 mmol). Titled compound was obtained by recrystallization from CH2Cl2. Yield: 87 mg, 77 %; m.p.: 326 °C; 1H NMR (400 MHz; [D6]DMSO): δ=9.84 (s, 2 H), 7.70 (d, J=8.5 Hz, 4 H), 7.43 (d, J=8.5 Hz, 4 H), 4.10 (s, 2 H) 2.35 ppm (s, 6 H); 13C NMR (100 MHz; [D6]DMSO): δ=168.4, 139.7, 132.7, 120.1, 116.8, 83.9, 80.4, 52.3, 39.2 ppm; IR(neat): =3292 (w), 3269 (w), 1649 (s), 1589 (m), 1522 (m), 1504 (m), 1402 (w), 1324 (m), 1246 (w), 825 (s), 705 (w), 616 cm−1 (m); HRMS(APCI): m/z: calcd for C23H19N2O2 [M+H]+ 355.1441; found 355.1437.

, ‐Bis(3′‐ethynyl<span class="Chemical">phenyl)<class="Chemical">span class="Chemical">bicyclo[1.1.1]pentane‐1,3‐dicarboxamide (38): Synthesized according to General Procedure 2 using 31 (50 mg, 0.320 mmol), oxalyl chloride (60.0 μL, 0.640 mmol), NEt3 (0.28 mL, 2.70 mmol) and 4‐ethynylaniline (78 mg, 0.64 mmol). Titled compound was obtained by recrystallization from CH2Cl2. Yield: 59 mg, 52 %; m.p.: 240 °C; 1H NMR (400 MHz; [D6]DMSO): δ=9.85 (s, 2 H), 7.84 (d, J=1.6 Hz, 2 H), 7.70 (d, J=9.5 Hz, 2 H), 7.30 (t, J=8.0 Hz, 2 H), 7.14 (d, J=9.8 Hz, 2 H), 4.15 (s, 2 H), 2.34 ppm (s, 6 H); 13C NMR (101 MHz; [D6]DMSO): δ=168.5, 139.1, 131.8, 120.2, 116.8, 83.8, 80.1, 52.4; IR (neat): =3286 (w), 1651 (s), 1583 (m), 1540 (m), 1426 (s), 1307 (w), 1317 (w), 1217 (w), 792 (s), 686 (m) 643 cm−1 (s); HRMS(APCI): m/z: calcd for C23H19N2O2 [M+H]+ 355.1441; found 355.1441.

, ‐Bis(3′‐<span class="Chemical">iodo<class="Chemical">span class="Chemical">phenyl)bicyclo[1.1.1]pentane‐1,3‐dicarboxamide (39): Synthesized according to General Procedure 2 using 31 (50 mg, 0.320 mmol), oxalyl chloride (60.0 μL, 0.640 mmol), NEt3 (0.28 mL, 2.70 mmol) and 3‐iodoaniline (140 mg, 0.64 mmol). Titled compound was obtained by recrystallization from CH2Cl2. Yield: 68 %; m.p.: 320 °C; 1H NMR (400 MHz; [D6]DMSO): δ=9.77 (s, 2 H), 8.11 (t, J=1.8 Hz, 2 H), 7.79 (d, J=8.0 Hz, 2 H), 7.42 (d, J=8.0 Hz, 2 H), 7.12 (t, J=8.0 Hz, 2 H), 2.33 ppm (s, 6 H); 13C NMR (101 MHz; [D6]DMSO): δ=167.9, 140.0, 132.0, 130.6, 128.0, 119.1, 94.4, 51.8, 45.7 ppm; IR(neat): =3272 (w), 1652 (s), 1586 (m), 1522 (m), 1414 (m), 1310 (w), 1243 (w), 882 (w), 776 (s), 681 cm−1 (s); HRMS(APCI): m/z: calcd for C19H15I2N2O2 [M−H]− 556.9223; found 556.9074.

Synthesis of BCP porphyrin dimers 50–52

, ‐Bis[4′‐{(10′′,15′′,20′′‐tri<span class="Chemical">phenyl<class="Chemical">span class="Chemical">porphyrinato)zinc(II)‐5′′‐yl}‐phenyl]bicyclo[1.1.1]pentane‐1,3‐dicarboxamides (50): Synthesized according to General Procedure 5 using BCP 36 (30 mg, 0.028 mmol), [5‐(4′,4′,5′,5′‐tetramethyl‐1′,3′,2′‐dioxaborolan‐2′‐yl)‐10,20‐bis(4′‐methylphenyl)‐15‐phenylporphyrinato]zinc(II) (41) (40 mg, 0.055 mmol), K3PO4 (140 mg, 0.34 mmol) and Pd(PPh3)4 (13 mg, 0.0056 mmol). Crude reaction mixture was purified using silica gel column chromatography to yield desired compound. Yield: 22 mg, 52 %; m.p.: 207 °C; R f=0.8 (SiO2, CH2Cl2/EtOAc, 8:2, v/v); 1H NMR (400 MHz; CDCl3): δ=8.89 (d, J=4.6 Hz, 4 H), 8.85 (d, J=4.6 Hz, 4 H), 8.84 (s, 8 H), 8.19 (d, J=7.6 Hz, 16 H), 8.04 (d, J=8.1 Hz, 4 H), 7.73–769 (m, 20 H), 2.71 ppm (s, 6 H); 13C NMR (101 MHz; CDCl3): δ=169.6, 167.1, 150.4, 150.2, 149.8, 139.7, 137.1, 134.5, 134.4, 134.3, 132.2, 132.1, 131.9, 131.5, 129.8, 127.3, 126.5, 89.9, 89.7, 52.5, 52.0, 40.1, 21.5 ppm; IR (neat): =2921 (w), 1736 (w), 1666 (w), 1529 (w), 1483 (w), 1339 (w), 1298 (w), 1208 (m), 998 (s), 796 (s), 719 (m); UV/Vis (CHCl3): λ max (logϵ)=424 (6.80), 551 (5.41), 590 nm cm−1 (4.82); HRMS(MALDI‐TOF): m/z: calcd for C95H62N10O2Zn2 [M]+ 1502.3640; 1502.3638 found.

, ‐Bis[4′‐{(10′′,20′′‐bis(4‐methyl<span class="Chemical">phenyl)‐15′′‐<class="Chemical">span class="Chemical">phenylporphyrin)‐5′′‐yl}‐phenyl]bicyclo[1.1.1]pentane‐1,3‐dicarboxamides (51): Synthesized according to General Procedure 5 using BCP 36 (23 mg, 0.042 mmol), 41 (58 mg, 0.083 mmol), K3PO4 (200 mg, 0.50 mmol), Pd(PPh3)4 (20 mg, 8.4 μmol). Reaction mixture was heated at 100 °C for 12 h. The crude reaction mixture was purified using silica gel column chromatography, desired compound was eluted via using CH2Cl2/(CH3)2CO, 8:2. Yield: 34 mg, 60 %; m.p.: 331 °C; R f=0.2 (SiO2, CH2Cl2/EtOAc, 8:2, v/v); 1H NMR (600 MHz, CDCl3): δ=8.92–8.85 (m, 16 H), 8.25 (t, J=7.6 Hz, 8 H), 8.11 (d, J=7.7 Hz, 8 H), 8.03 (d, J=7.9 Hz, 4 H), 7.81–7.76 (m, 6 H), 7.66 (s, 2 H), 7.59 (d, J=7.7 Hz, 8 H), 2.77 (s, 6 H), 2.74 (s, 12 H), −2.74 ppm (s, 4 H); 13C NMR (151 MHz, CDCl3): δ=167.4, 144.2, 142.2, 139.3, 139.2, 138.8, 137.4, 136.9, 135.2, 134.5, 134.5, 127.4, 126.6, 120.3, 120.1, 119.1, 118.1, 52.4, 42.0, 21.6 ppm; IR (neat): =2981 (w), 2832 (w), 1710 (m), 1595 (m), 1367 (w), 1219 (m), 1140 (m), 1093 (m), 1047 (m), 942 (m), 807 (s), 757 (s), 691 (m), 652 cm−1 (m); UV/Vis (CHCl3): λ max (logϵ)=423 (5.92), 519 (4.52), 555 (4.25), 594 nm (4.04), 651 nm (4.06); HRMS(MALDI‐TOF): m/z: calcd for C99H75N10O2 [M+H]+ 1434.5996; 1435.6091 found.

, ‐Bis[3′‐{(10′′,15′′,20′′‐tri<span class="Chemical">phenyl<class="Chemical">span class="Chemical">porphyrinato)zinc(II)‐5′′‐yl}‐phenyl]bicyclo[1.1.1]pentane‐1,3‐dicarboxamides (52): Synthesized according to General Procedure 5 using BCP 39 (19 mg, 0.033 mmol), 41 (50 mg, 0.066 mmol), K3PO4 (70 mg, 0.33 mmol) and Pd(PPh3)4 (0.0066 mmol, 7.6 mg). Reaction mixture was heated at 100 °C for 4 h. The crude reaction mixture was subjected to silica gel column chromatography and titled compound was eluted via CH2Cl2/EtOAc, 9:1. Yield: 37 mg, 73 %; m.p.: 220 °C; R f=0.35 (SiO2, CH2Cl2/EtOAc, 8:2, v/v); 1H NMR (400 MHz, CDCl3/CD3OD): δ=8.85–8.81 (m, 16 H), 8.32(brs, 2 H), 8.17 (d, J=4.3 Hz, 4 H), 8.03 (d, J=7.1 Hz, 10 H), 7.95 (d, J=7.6 Hz, 2 H), 7.71–7.62 (m, 8 H), 7.47 (d, J=7.2 Hz, 8 H), 2.65 (s, 12 H), 2.44 ppm (s, 6 H); 13C NMR (101 MHz, CDCl3/CD3OD): δ=150.1, 149.9, 149.7, 144.1, 140.3, 136.7, 134.4, 131.5, 131.4, 131.2, 127.0, 126.6, 126.2, 120.0, 52.1, 39.0, 21.3 ppm; IR (neat): =2920 (w), 1650 (w), 1603 (w), 1518 (w), 1477 (w), 1388(w), 1204 (w), 1065 (w), 992 (s), 794 (s), 721 (m), 693 cm−1 (m); UV/Vis (CHCl3): λ max (logϵ)=422 (6.80), 551 (5.55), 589 nm (5.08); HRMS(MALDI‐TOF): m/z: calcd for C99H70N10O2Zn2 [M]+ 1562.4770; 1562.4253 found.

Conflict of interest

The authors declare no conflict of interest.

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Supplementary

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