Three isostructural coordination networks of Ce, Pr, and Nd nitrate with 4,4'-bi-pyridine N,N'-dioxide (bpydo) are reported, namely poly[[tris-(nitrato-κ(2) O,O')cerium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N')], [Ce(NO3)3(C10H8N2O2)2], poly[[tris-(nitrato-κ(2) O,O')praeseodymium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N')], [Pr(NO3)3(C10H8N2O2)2], and poly[[tris(nitrato-κ(2) O,O')neodymium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N'], [Nd(NO3)3(C10H8N2O2)2]. All three compounds are isostructural to the previously reported La analogue. The asymmetric unit of [Ln(NO3)3(μ2-bpydo)2] contains one lanthanide cation, two bpydo ligands, and three nitrate anions. Both bpydo ligands act as end-to-end μ2-bridges and display nearly ideal cis and gauche conformations, respectively. The bpydo ligands link the ten-coordinate Ln (III) cations, forming inter-digitating 4(4) grid-like layers extending parallel to (-101), where inter-digitation of layers is promoted by C-H⋯O inter-actions between nitrate anions and bpydo ligands. The inter-digitated layers are linked to sets of neighboring layers via further C-H⋯O and π-π inter-actions.
Three isostructural coordination networks of Ce, Pr, and Ndnitrate with 4,4'-bi-pyridine N,N'-dioxide (bpydo) are reported, namely poly[[tris-(nitrato-κ(2) O,O')cerium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N')], [Ce(NO3)3(C10H8N2O2)2], poly[[tris-(nitrato-κ(2) O,O')praeseodymium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N')], [Pr(NO3)3(C10H8N2O2)2], and poly[[tris(nitrato-κ(2) O,O')neodymium(III)]-bis-(μ2-4,4'-bi-pyridine N,N'-dioxide-κ(2) N:N'], [Nd(NO3)3(C10H8N2O2)2]. All three compounds are isostructural to the previously reported La analogue. The asymmetric unit of [Ln(NO3)3(μ2-bpydo)2] contains one lanthanide cation, two bpydo ligands, and three nitrate anions. Both bpydo ligands act as end-to-end μ2-bridges and display nearly ideal cis and gauche conformations, respectively. The bpydo ligands link the ten-coordinate Ln (III) cations, forming inter-digitating 4(4) grid-like layers extending parallel to (-101), where inter-digitation of layers is promoted by C-H⋯O inter-actions between nitrate anions and bpydo ligands. The inter-digitated layers are linked to sets of neighboring layers via further C-H⋯O and π-π inter-actions.
The use of aromatic N,N′-dioxide ligands such as 4,4′-bipyridine N,N′-dioxide (bpydo) in the synthesis of lanthanide compounds comprising coordination networks has been of recent interest (Dillner et al., 2010a
▸,b
▸; Hill et al., 2004 ▸, 2005a
▸,b
▸; Long et al., 2000 ▸, 2002 ▸). The coordination modes of aromatic N,N′-dioxide ligands are flexible; they may act as terminal ligands, end-on or end-to-end μ2-bridges, μ3-bridges, or μ4-bridges (Lu et al., 2002 ▸; Ma et al., 2001 ▸, 2003 ▸; Zhang et al., 2004a
▸,b
▸). When acting as end-to-end μ2-bridges, these ligands can display cis, gauche, or trans conformations where the ideal conformations have M—O⋯O—M torsion angles of 0, 90 and 180°, respectively (Sun et al., 2004 ▸). Furthermore, aromatic N,N′-dioxide ligands are able to participate in a variety of hydrogen-bonding interactions (González Mantero et al., 2006 ▸). Structure prediction with these ligands can be difficult, not only due to their flexible bonding modes and various hydrogen-bonding interactions, but also due to the influences of solvent and anion (Hill et al., 2005a
▸).
Structural commentary
Three isostructural coordination networks of Ce, Pr, and Ndnitrate with 4,4′-bipyridine N,N′-dioxide (bpydo), [Ln(NO3)3(μ2-bpydo)2] [Ln = Ce (I), Pr (II), and Nd (III)] are reported. All three compounds are isostructural to the previously reported La analogue (Hill et al., 2004 ▸).The asymmetric unit of [Ln(NO3)3(μ2-bpydo)2] contains one lanthanide cation, two end-to-end bridging μ2-bpydo ligands, and three chelating nitrate anions. All atoms in the asymmetric unit lie on general positions (Fig. 1 ▸). The Ln
III atoms have a coordination sphere defined by six oxygen atoms from chelating nitrate anions and four oxygen atoms from bpydo ligands. The ten oxygen atoms in the LnO10 coordination environment form a distorted bi-capped square prism (Fig. 2 ▸). One of the ligands bridges in a nearly perfect cis conformation with an Lnl—O3⋯O4—Ln1iv torsion angle of approximately 5° and a dihedral angle between the rings of approximately 33°. The other ligand bridges in a nearly perfect gauche conformation with an Lnl—O2⋯O1—Ln1iii torsion angle of approximately 92° and a dihedral angle between the rings of approximately 28° (see Table 1 ▸). The bpydo ligands link the Ln
III atoms, forming 44 grid-like layers that are parallel to (01) (Fig. 3 ▸). Each layer interdigitates with a symmetry-equivalent second layer related by a twofold screw axis. The nitrate anions chelate to the metal cations on one side of the 44 grid and are directed towards the square void of the symmetry-related interdigitated 44 grid (Fig. 4 ▸).
Figure 1
Coordination sphere around the CeIII cation in the structure of (I), with displacement ellipsoids drawn at the 50% probability level. Dashed lines represent C—H⋯O interactions between neighboring bpydo ligands within the coordination sphere. [Symmetry codes: (i) x − , −y + , z − ; (ii) x, y − 1, z.]
Figure 2
LnO10 coordination environment forming a distorted bicapped square prism. [Symmetry codes: (i) x − , −y + , z − ; (ii) x, y − 1, z.]
Table 1
Selected geometric parameters (Å, °) for (I)–(III)
Dihedral angles are reported between the mean planes defined by the indicated aromatic rings. Cg1 is the centroid of the N3/C11–C15 ring.
(I)
(II)
(III)
Ln⋯Ln distances
Ln1⋯Ln1iii
13.3398 (13)
13.3127 (9)
13.3035 (5)
Ln1⋯Ln1iv
13.2996 (11)
13.2634 (8)
13.2558 (4)
Dihedral angles
N1/C1–C5⋯N2/C6–C10
27.387 (58)
28.041 (62)
28.471 (109)
N3/C11–C15⋯N4/C16–C20
22.560 (50)
22.552 (55)
22.677 (93)
Torsion angles
Ln1—O2⋯O1—Ln1iii
92.53 (6)
91.80 (6)
91.75 (11)
Ln1—O3⋯O4—Ln1iv
5.38 (7)
4.86 (8)
4.87 (14)
π–π interactions for Cg1⋯Cg1x
Centroid–centroid distance
3.7535 (10)
3.7465 (10)
3.7344 (17)
Interplanar distance
3.2830 (6)
3.2790 (7)
3.2815 (11)
Slippage
1.820
1.810
1.783
Cg1—H15x distance
3.305
3.312
3.311
Symmetry codes: (iii) x, y + 1, z; (iv) x + , −y + , z + ; (x) −x + , −y + , −z + 2.
Figure 3
Diagram showing the 44 grid-like layers that lie parallel to (01) in (I). Dashed lines represent C—H⋯O interactions between neighboring bpydo ligands within the CeIII coordination sphere.
Figure 4
Diagram showing the C—H⋯O interactions between anions and ligands of interdigitated layers in (I). Individual layers are represented in green and blue. Dashed red lines represent C—H⋯O interactions between the layers. [Symmetry codes: (iii) x, y + 1, z; (v) −x + , y + , −z + ; (xi) x + , −y + , z + .]
While a roughly linear decrease in cell volume for a series of isostructural lanthanide compounds due to the lanthanide contraction may be expected (see, for example, He et al., 2005 ▸; Ji et al., 2012 ▸), deviations from a linear trend as observed for compounds (I)–(III) are not unprecedented, and the gradual decrease in Ln—X bond lengths and bridged Ln⋯Ln distances provides evidence of the lanthanide contraction (see, for example, Jia et al., 2013 ▸; Li et al., 2004 ▸, 2015 ▸). Recent studies on several series of isostructural lanthanide compounds have shown that the lanthanide contraction can be observed by the quadratic decay of the Ln—O bond lengths with increasing atomic number (Quadrelli, 2002 ▸; Seitz et al., 2007 ▸; Xu et al., 2013 ▸). An examination of both the Ln—Obpydo and Ln—Onitrate distances for compounds (I)–(III) shows the expected gradual decrease in the Ln—O bond lengths from Ce (I) to Nd (III) due to the lanthanide contraction (Table 2 ▸). The gradual decrease in bpydo-bridged Ln⋯Ln distances within the layers is also consistent with the radius contraction from Ce to Nd (Table 1 ▸).
Table 2
Selected bond lengths (Å) in compounds (I)–(III)
Compound
(I)
(II)
(III)
Ln—O bond lengths involving bpydo ligands
Ln1—O1ii
2.5464 (11)
2.5360 (12)
2.526 (2)
Ln1—O2
2.5192 (11)
2.5009 (12)
2.488 (2)
Ln1—O3
2.4685 (11)
2.4558 (11)
2.451 (2)
Ln1—O4i
2.4692 (11)
2.4554 (12)
2.448 (2)
Average Ln—O distances
2.501
2.487
2.478
Ln—O bond lengths involving chelating nitrate anions
Ln1—O5
2.5929 (13)
2.5750 (13)
2.555 (2)
Ln1—O6
2.6573 (13)
2.6443 (14)
2.640 (2)
Ln1—O8
2.6004 (12)
2.5832 (13)
2.573 (2)
Ln1—O9
2.6428 (12)
2.6242 (13)
2.615 (2)
Ln1—O11
2.6231 (12)
2.6036 (12)
2.585 (2)
Ln1—O12
2.6333 (11)
2.6147 (12)
2.597 (2)
Average Ln—O distances
2.625
2.608
2.594
Symmetry codes: (i) x − , −y + , z − ; (ii) x, y − 1, z.
Supramolecular features
Stabilizing C—H⋯O interactions (C5—H5⋯O4vii, C10—H10⋯O3, C15—H15⋯O1ii, and C20—H20⋯O2iv) are observed between neighboring bpydo ligands within the coordination sphere of the Ln
III cation (see Tables 3 ▸–5 ▸
▸ for symmetry codes; Fig. 1 ▸). The interdigitation of layers is promoted by C—H⋯O interactions (C1—H1⋯O5v, C4—H4⋯O13vi, C9—H9⋯O10v, C11—H11⋯O10v, C14—H14⋯O7ix, C16—H16⋯O13v, and C17—H17⋯O12v) between the ligands of one layer and nitrate anions of the other layer (Fig. 4 ▸). Further C—H⋯O interactions (C9—H9⋯O9viii and C10—H10⋯O7viii) and π–π interactions between Cg1 and the inversion-related Cg1x link each set of interdigitated layers to symmetry-equivalent sets of layers above and below it [symmetry code: (x) −x + , −y + , −z + 2; Fig. 5 ▸). π–π interactions between the neighboring rings are observed with a centroid-to-centroid distance of 3.7535 (10) Å and an interplanar distance of 3.2830 (6) Å for (I); there is a slippage of 1.820 Å such that H15x of the neighboring N-oxide ring lies nearly centered over the centroid of Cg1 at a distance of 3.305 Å [see Table 1 ▸ for distances in compounds (II) and (III)].
Diagram showing C—H⋯O interactions and π–π interactions that link each set of interdigitated layers to similar sets of layers above and below it in (I). Individual layers are represented in green and blue. Dashed red lines represent C—H⋯O interactions, and dashed black lines represent π–π interactions.
Database survey
A survey of the Cambridge Structural Database (CSD, November 2014; Groom & Allen, 2014 ▸) returned hits for 333 structures with 4,4′-bipyridine N,N′-dioxide. Sixty three structures are reported where bpydo coordinates to a lanthanidemetal and acts a as bridging ligand in a coordination network. Of these structures, ten are reported with nitrate as the counter-ion. In [Tb(bpydo)2(NO3)3], linear chains are observed (Long et al., 2002 ▸). A one-dimensional network composed of zigzag chains is observed for [Tb(bpydo)(CH3OH)(NO3)3] (Long et al., 2002 ▸). In {[Ln(bpydo)1.5(NO3)3]·CH2Cl2} with Ln = Eu (Dillner et al., 2010a
▸), Gd (Dillner et al., 2010b
▸), and Tb (Long et al., 2002 ▸), a one-dimensional network composed of ladder-like chains is observed. [La(bpydo)2(NO3)3] is a two-dimensional network composed of sheets with 44 topology and is isostructural to the Ce, Pr, and Nd structures reported herein (Hill et al., 2004 ▸). In {[Er2(bpydo)3(NO3)6]·2CH3OH}, {[Tb(bpydo)1.5(NO3)3]·CH3OH·0.8H2O}, and {[Tb(bpydo)1.5(NO3)3]·0.4CCl4·0.8CH3OH}, two-dimensional networks composed of sheets with 4.82 topology are formed (Long et al., 2000 ▸, 2002 ▸). In {[Sm(bpydo)2(NO3)3]·0.5H2O}, a twofold interpenetrating three-dimensional network is formed (Long et al., 2000 ▸).
Synthesis and crystallization
4,4′-bipyridine N,N′-dioxide·H2O was synthesized from 4,4′-bipyridine according to the method of Simpson et al. (1963 ▸). All other chemicals were obtained from commercial sources and used without further purification. For the Ce, Pr and Nd compounds, respectively, the appropriate Ln(NO3)3·6H2O (0.113 mmol) was placed in the bottom of a test tube and covered with CH2Cl2 (5 ml). 4,4′-Bipyridine-N,N′-dioxide·H2O (0.0376 g, 0.182 mmol) was dissolved in methanol (8 ml), and this solution was layered over the CH2Cl2 solution. The two solutions were allowed to slowly mix. Over a period of several weeks the Ln(NO3)3·6H2O dissolved, and red block-like crystals of [Ce(μ2-bpydo)2(NO3)3], yellow block-like crystals of [Pr(μ2-bpydo)2(NO3)3], and yellow block-like crystals of [Nd(μ2-bpydo)2(NO3)3] were formed.
Refinement
All aromatic H atoms were positioned geometrically and refined using a riding model with C—H = 0.95 Å and with U
iso(H) = 1.2U
eq(C). Crystal data, data collection and structure refinement details are summarized in Table 6 ▸.
Table 6
Experimental details
(I)
(II)
(III)
Crystal data
Chemical formula
[Ce(NO3)3(C10H8N2O2)2]
[Pr(NO3)3(C10H8N2O2)2]
[Nd(NO3)3(C10H8N2O2)2]
Mr
702.52
703.31
706.64
Crystal system, space group
Monoclinic, C2/c
Monoclinic, C2/c
Monoclinic, C2/c
Temperature (K)
173
173
173
a, b, c (Å)
26.786 (3), 13.3398 (13), 13.7571 (13)
26.7416 (18), 13.3127 (9), 13.7586 (9)
26.7422 (10), 13.3035 (5), 13.7804 (5)
β (°)
105.837 (1)
105.981 (1)
106.065 (1)
V (Å3)
4729.1 (8)
4708.8 (5)
4711.1 (3)
Z
8
8
8
Radiation type
Mo Kα
Mo Kα
Mo Kα
μ (mm−1)
2.01
2.16
2.29
Crystal size (mm)
0.55 × 0.45 × 0.38
0.55 × 0.37 × 0.26
0.14 × 0.12 × 0.08
Data collection
Diffractometer
Bruker APEXII CCD
Bruker APEXII CCD
Bruker D8 Quest CMOS
Absorption correction
Multi-scan (SADABS; Bruker, 2009 ▸)
Multi-scan (SADABS; Bruker, 2009 ▸ ▸)
Multi-scan (SADABS; Bruker, 2009 ▸ ▸)
Tmin, Tmax
0.536, 0.746
0.579, 0.746
0.682, 0.747
No. of measured, independent and observed [I > 2σ(I)] reflections
15990, 7152, 6686
18363, 7241, 6782
47148, 8277, 5419
Rint
0.018
0.020
0.115
(sin θ/λ)max (Å−1)
0.735
0.737
0.777
Refinement
R[F2 > 2σ(F2)], wR(F2), S
0.020, 0.050, 1.05
0.021, 0.052, 1.05
0.051, 0.067, 1.01
No. of reflections
7152
7241
8277
No. of parameters
370
370
370
H-atom treatment
H-atom parameters constrained
H-atom parameters constrained
H-atom parameters constrained
Δρmax, Δρmin (e Å−3)
1.10, −0.65
0.89, −1.06
1.49, −1.29
Computer programs: APEX2 and SAINT (Bruker, 2009 ▸, 2014 ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015 ▸) and X-SEED (Barbour, 2001 ▸).
Crystal structure: contains datablock(s) global, I, II, III. DOI: 10.1107/S205698901502318X/wm5242sup1.cifStructure factors: contains datablock(s) I. DOI: 10.1107/S205698901502318X/wm5242Isup2.hklStructure factors: contains datablock(s) II. DOI: 10.1107/S205698901502318X/wm5242IIsup3.hklStructure factors: contains datablock(s) III. DOI: 10.1107/S205698901502318X/wm5242IIIsup4.hklCCDC references: 1440109, 1440108, 1440107Additional supporting information: crystallographic information; 3D view; checkCIF report
Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.020
H-atom parameters constrained
wR(F2) = 0.050
w = 1/[σ2(Fo2) + (0.0231P)2 + 5.9858P] where P = (Fo2 + 2Fc2)/3
S = 1.05
(Δ/σ)max = 0.002
7152 reflections
Δρmax = 1.10 e Å−3
370 parameters
Δρmin = −0.65 e Å−3
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are
estimated using the full covariance matrix. The cell esds are taken into
account individually in the estimation of esds in distances, angles and
torsion angles; correlations between esds in cell parameters are only used
when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes.
Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.021
H-atom parameters constrained
wR(F2) = 0.052
w = 1/[σ2(Fo2) + (0.0248P)2 + 6.7123P] where P = (Fo2 + 2Fc2)/3
S = 1.05
(Δ/σ)max = 0.003
7241 reflections
Δρmax = 0.89 e Å−3
370 parameters
Δρmin = −1.06 e Å−3
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes.
Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.051
H-atom parameters constrained
wR(F2) = 0.067
w = 1/[σ2(Fo2) + (0.0161P)2 + 13.5513P] where P = (Fo2 + 2Fc2)/3
S = 1.01
(Δ/σ)max = 0.001
8277 reflections
Δρmax = 1.49 e Å−3
370 parameters
Δρmin = −1.29 e Å−3
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes)
are estimated using the full covariance matrix. The cell esds are taken
into account individually in the estimation of esds in distances, angles
and torsion angles; correlations between esds in cell parameters are only
used when they are defined by crystal symmetry. An approximate (isotropic)
treatment of cell esds is used for estimating esds involving l.s. planes.
Authors: Robert J Hill; De-Liang Long; Mark S Turvey; Alexander J Blake; Neil R Champness; Peter Hubberstey; Claire Wilson; Martin Schröder Journal: Chem Commun (Camb) Date: 2004-07-21 Impact factor: 6.222