Literature DB >> 27536419

Zwitterionic 4-bromo-6-meth-oxy-2-{[tris-(hy-droxy-meth-yl)methyl]-iminiumyl-meth-yl}phenolate: crystal structure and Hirshfeld surface analysis.

See Mun Lee1, Kong Mun Lo1, Sang Loon Tan1, Edward R T Tiekink1.   

Abstract

In the solid state, the title compound, C12H16BrNO5 [systematic name: 4-bromo-2-((1E)-{[1,3-dihy-droxy-2-(hy-droxy-meth-yl)propan-2-yl]iminium-yl}meth-yl)-6-meth-oxy-benzen-1-olate], C12H16BrNO5, is found in the keto-amine tautomeric form, with an intra-molecular iminium-N-H⋯O(phenolate) hydrogen bond and an E conformation about the C=N bond. Both gauche (two) and anti relationships are found for the methyl-hydroxy groups. In the crystal, a supra-molecular layer in the bc plane is formed via hy-droxy-O-H⋯O(hy-droxy) and charge-assisted hy-droxy-O-H⋯O(phenolate) hydrogen-bonding inter-actions; various C-H⋯O inter-actions provide additional cohesion to the layers, which stack along the a axis with no directional inter-actions between them. A Hirshfeld surface analysis confirms the lack of specific inter-actions in the inter-layer region.

Entities:  

Keywords:  Hirshfeld surface analysis; crystal structure; hydrogen bonding; zwitterion

Year:  2016        PMID: 27536419      PMCID: PMC4971878          DOI: 10.1107/S2056989016012159

Source DB:  PubMed          Journal:  Acta Crystallogr E Crystallogr Commun


Chemical context

Inter­est in mol­ecules related to the title Schiff base compound derived from tris­(hy­droxy­meth­yl)amino­methane (see Scheme) rests largely with the biological activity exhibited by their metal complexes. Thus, various species have been studied for their anticancer potential, e.g. vanadium (Back et al., 2012 ▸) and tin (Lee et al., 2015 ▸). The insulin-mimetic behaviour of vanadium complexes have been explored (Rehder et al., 2002 ▸), as has the catecolase activity of binuclear cobalt complexes (Dey & Mukherjee, 2014 ▸). More recently, the adipogenic (cell differentiation) capacity of vanadium (Halevas et al., 2015 ▸) and zinc complexes has been described (Tsave et al., 2015 ▸). Over and above these considerations, magnetochemistry motivates on-going investigations, especially single-mol­ecule (Wu et al., 2007 ▸; Chandrasekhar et al., 2013 ▸; Dey et al., 2015 ▸) and lanthanide-containing species (Zou et al., 2015 ▸; Das et al., 2015 ▸). It was during on-going biological assays (Lee et al., 2015 ▸) that the title compound, (I), became available. Herein, the crystal and mol­ecular structures of (I) are described, as well as a Hirshfeld surface analysis.

Structural commentary

The mol­ecular structure of (I) (Fig. 1 ▸) exists as a zwitterion in the solid state, with the iminium N atom being protonated and the phenolate O atom being deprotonated. The observed keto–amine tautomeric form for (I) is the common form for mol­ecules of this type, see Database survey. The conformation about the iminium bond [1.295 (4) Å] is E and this residue is almost coplanar with the benzene ring, forming a C2—C1—C7—N1 torsion angle of 1.9 (4)°. This arrangement allows for the formation of a tight charge-assisted iminium-N—H⋯O(phenolate) hydrogen bond (Table 1 ▸). The conformations of the methyl­hydroxy groups are variable, with gauche relationships about the C8—C9 and C8—C11 bonds [N1—C8—C9—O2 is 45.9 (3)°, i.e. +synclinal, and N1—C8—C11—O4 is −80.2 (3)°, i.e. –synclinal], and an anti relationship about the C8—C10 bond [N1—C8—C10—O3 is 178.8 (2)°, i.e. +anti­periplanar]. The meth­oxy group is almost coplanar with the ring it is connected to, as seen in the value of the C12—O5—C3—C2 torsion angle of 177.7 (2)°.
Figure 1

The mol­ecular structure of (I), showing the atom-labelling scheme and displacement ellipsoids at the 70% probability level. The intramolecular N—H⋯O hydrogen bond is shown as a double-dashed line (see Table 1 ▸)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A D—HH⋯A DA D—H⋯A
N1—H1N⋯O10.85 (2)1.90 (2)2.608 (3)140 (3)
O2—H2O⋯O4i 0.82 (2)1.93 (2)2.741 (3)170 (3)
O3—H3O⋯O2ii 0.81 (2)1.91 (2)2.704 (3)167 (4)
O4—H4O⋯O1iii 0.82 (3)1.98 (3)2.760 (3)158 (3)
C7—H7⋯O1iii 0.932.553.429 (4)158
C9—H9B⋯O3i 0.972.513.242 (4)132
C11—H11B⋯O1iv 0.972.393.353 (3)171

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) .

Supra­molecular features

As anti­cipated from the chemical composition of (I), there are considerable hydrogen-bonding inter­actions operating in the crystal; geometric characteristics of these are listed in Table 1 ▸. Each of the hy­droxy O2 and O3 atoms participates in hy­droxy-O—H⋯O(hy­droxy) hydrogen-bonding inter­actions, while the hy­droxy O4 atom forms a donor inter­action with the phenolate O1 atom. The result is the formation of a supra­molecular layer parallel to (100) (Fig. 2 ▸ a). Within this framework are a number of C—H⋯O inter­actions, i.e. imine-C7—H⋯O(phenolate), methyl­ene-C11—H⋯O(phenolate) and methyl­ene-C9—H⋯O(hy­droxy) (Fig. 2 ▸ b). In accord with the distance criteria in PLATON (Spek, 2009 ▸), layers stack along the a axis with no directional inter­actions between them. In order to gain more insight into the mol­ecular packing of (I), a Hirshfeld surface analysis was conducted.
Figure 2

The mol­ecular packing in (I), showing (a) a view of the supra­molecular layer sustained by O—H⋯O hydrogen bonding, shown as orange dashed lines, and (b) a view of the unit-cell contents shown in projection down the b axis, highlighting the stacking of layers along the a axis. In (a), only acidic H atoms are shown.

Analysis of the Hirshfeld surfaces

The Hirshfeld surface of (I) was mapped over the d norm contact distance within the range of −0.67 to 1.31 Å through calculation of the inter­nal (d i) and external (d e) Hirshfeld surface distances to the nearest nucleus (McKinnon et al., 2007 ▸; Spackman & Jayatilaka, 2009 ▸). Two-dimensional fingerprint plots associated with relevant close contacts were obtained through the plot of d e versus d i (Spackman & McKinnon, 2002 ▸). The electrostatic potential (ESP) of the crystal structure was mapped onto the Hirshfeld surface by an ab initio quantum modelling approach at the Hartree–Fock level of theory with the STO-3G basis set (HF/STO-3G) over the range of −0.122 to 0.189 au. All Hirshfeld surface and fingerprints plots were generated using Crystal Explorer (Wolff et al., 2012 ▸), while the ESP was calculated by TONTO (Spackman et al., 2008 ▸) as implemented in Crystal Explorer. Distances involving H atoms were normalized to the standard neutron diffraction bond lengths. The Hirshfeld surface map provides a visual summary of any close contacts (shown as red) in contrast to relatively long contacts (shown as white and blue). As displayed in Fig. 3 ▸(a), there are several red spots observed on the Hirshfeld surface of (I), particularly around the O atoms, indicating close inter­actions at distances shorter than the sum of the van der Waals radii. A qu­anti­tative analysis of the decomposed two-dimensional fingerprint plot of the relevant O⋯H/H⋯O inter­actions reveals a distinctive reciprocal spike in the plot of d e versus d i (Fig. 3 ▸ b), with the sum of contact distances being approximately 1.74 Å, signifying a strong inter­molecular inter­action. Such strong inter­actions constitute the second major contribution to the Hirshfeld surface, i.e. 25.4%, between the most prominent H⋯H (38.2%) and other major contacts, like C⋯H/H⋯C (15.2%) and Br⋯H/H⋯Br (14.3%) (Fig. 4 ▸). Their contributions to the overall Hirshfeld surface notwithstanding, as seen from Figs. 3 ▸(c) and 3(d), C⋯H and Br⋯H contacts are at distances greater than their respective van der Waals radii. Fig. 5 ▸ shows the O—H⋯O inter­actions formed between a reference mol­ecule and symmetry-related mol­ecules.
Figure 3

(a) Overall Hirshfeld surface and the two-dimensional fingerprint plot for (I), and d norm surfaces and two-dimensional plots associated with (b) O⋯H/H⋯O, (c) Br⋯H/H⋯Br and (d) C⋯H/H⋯C inter­actions.

Figure 4

Percentage distribution of the corresponding close contacts to the Hirshfeld surface of (I).

Figure 5

The d norm surface for (I), highlighting the O⋯H hydrogen-bonding inter­actions which connect mol­ecules in the mol­ecular packing.

In order to gain a qualitative insight into the electrostatic inter­action and rationalize the packing motif of the structure, the ESP was mapped over the Hirshfeld surface. The result illustrated in Fig. 6 ▸(a), shows that the electronegative sites are predominantly converged on O atoms and that, upon crystallization, the electronegative and electropositive sites are connected (Fig. 6 ▸ b). It is noteworthy that despite bromine being an electrophilic element, it did not form a significant non-covalent inter­action with neighbouring mol­ecules in the inter-layer region where these atoms are directed. The closest contact in this region occurs with methyl-C⋯H12C i, at 3.12 Å, i.e beyond the sum of the respective van der Waals radii (Spek, 2009 ▸) [symmetry code: (i) x, − − y,  + z].
Figure 6

(a) The electrostatic potential map of (I) within the range of −0.008 to 0.008 au and (b) the ESP mapped over the Hirshfeld surface, showing the attraction between the electronegative (red) and electropositive (blue) sites in (I).

Database survey

There are several closely related structures to (I) in the crystallographic literature (Groom et al., 2016 ▸). What might be termed the parent compound, i.e. with no substitution at the phenolate ring other than the imino group in the 2-position, (II), exists in the keto–amine tautomeric form and has been the subject of several investigations (Asgedom et al., 1996 ▸; Tatar et al., 2005 ▸). Similar zwitterionic structures are found in the 4-bromo, (III) (Martinez et al., 2011 ▸), and 6-meth­oxy, (IV) (Odabas˛oǧlu et al., 2003 ▸), derivatives, both closely related to (I), suggesting this is the most stable form for these mol­ecules, at least in the solid state. Despite the similar electronic structures, conformational differences exist about the ring between (I) and (IV) as seen in the relative dispositions of the meth­oxy groups, i.e. C12—O5—C3—C2 is 177.7 (2)° in (I) but −165.75 (14)° in (IV) (Fig. 7 ▸). Differences in conformation of the methyl­hydroxy groups are also apparent, no doubt due to the different hydrogen-bonding patterns in the respective crystal structures.
Figure 7

Overlay diagrams for (I) (red image), (II) (green), (III) (blue) and (IV) (pink). Images have been drawn so the benzene rings overlap.

Synthesis and crystallization

A solution of tris­(hy­droxy­meth­yl)amino­methane (1.21 g, 0.01 mol) was added to an ethano­lic solution of 5-bromo-3-meth­oxy-2-hy­droxy­benzaldehyde (2.31 g, 0.01 mol) and refluxed for 2 h. The solution was allowed to stand at room temperature, during which an orange solid formed. This was recrystallized by slow evaporation of its ethanol solution. Yield: 2.67 (80%). Yellow crystals. M.p. 465–466 K. Analysis calculated for C12H16BrNO5: C 44.48, H 3.70, N 1.99%; found: C 44.81, H 3.42, N 1.64%. IR (cm−1): 3330 (b) ν(N—H, O—H), 1640 (s) ν(C=N), 1528 (m) ν(—O—C=C—), 1066 (m) ν(C—O—C). 1H NMR (400 MHz, CDCl3): δ 8.35 [s, 1H, –N=C(H)], 7.01–7.10 (m, 1H, aryl H), 6.83–6.89 (m, 1H, aryl H), 5.06 (s, 3H, OH), 3.95 (s, 3H, OCH3), 3.37–3.75 (m, 6H, aliphatic H).

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. The carbon-bound H atoms were placed in calculated positions (C—H = 0.93–0.97 Å) and were included in the refinement in the riding-model approximation, with U iso(H) set at 1.2–1.5U eq(C). The O- and N-bound H atoms were located from difference Fourier maps and refined with distance restraints O—H = 0.82±0.01 Å and N—H = 0.86±0.01 Å, and with U iso(H) set at 1.5U eq(O) and U iso(H) set at 1.2U eq(N), respectively. Owing to poor agreement, several reflections, i.e. (−9 7 7), (−12 4 6), (−10 5 6) and (−3 3 2), were omitted from the final cycles of refinement.
Table 2

Experimental details

Crystal data
Chemical formulaC12H16BrNO5
M r 334.17
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)12.2872 (9), 10.7186 (8), 10.5830 (8)
β (°)108.462 (1)
V3)1322.06 (17)
Z 4
Radiation typeMo Kα
μ (mm−1)3.13
Crystal size (mm)0.26 × 0.10 × 0.08
 
Data collection
DiffractometerBruker SMART APEX
Absorption correctionMulti-scan (SADABS; Sheldrick, 1996)
T min, T max 0.497, 0.788
No. of measured, independent and observed [I > 2σ(I)] reflections5095, 2257, 1923
R int 0.032
(sin θ/λ)max−1)0.595
 
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S 0.030, 0.068, 1.04
No. of reflections2257
No. of parameters185
No. of restraints4
Δρmax, Δρmin (e Å−3)0.41, −0.54

Computer programs: SMART and SAINT (Bruker, 2008 ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015 ▸), ORTEP-3 for Windows (Farrugia, 2012 ▸), QMol (Gans & Shalloway, 2001 ▸), DIAMOND (Brandenburg, 2006 ▸) and publCIF (Westrip, 2010 ▸).

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S2056989016012159/hb7605sup1.cif Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989016012159/hb7605Isup2.hkl CCDC reference: 1496206 Additional supporting information: crystallographic information; 3D view; checkCIF report
C12H16BrNO5F(000) = 680
Mr = 334.17Dx = 1.679 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 12.2872 (9) ÅCell parameters from 1493 reflections
b = 10.7186 (8) Åθ = 2.6–27.9°
c = 10.5830 (8) ŵ = 3.13 mm1
β = 108.462 (1)°T = 293 K
V = 1322.06 (17) Å3Prism, yellow
Z = 40.26 × 0.10 × 0.08 mm
Bruker SMART APEX diffractometer2257 independent reflections
Radiation source: fine-focus sealed tube1923 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.032
φ and ω scansθmax = 25.0°, θmin = 1.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)h = −10→14
Tmin = 0.497, Tmax = 0.788k = −12→12
5095 measured reflectionsl = −9→12
Refinement on F24 restraints
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.030w = 1/[σ2(Fo2) + (0.0206P)2 + 0.8903P] where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.068(Δ/σ)max < 0.001
S = 1.04Δρmax = 0.41 e Å3
2257 reflectionsΔρmin = −0.54 e Å3
185 parameters
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.
xyzUiso*/Ueq
Br10.45516 (2)−0.01276 (3)0.80991 (3)0.01835 (11)
O10.79706 (16)0.09687 (18)0.52558 (18)0.0134 (4)
O21.05037 (18)0.27428 (18)0.60436 (19)0.0141 (5)
H2O1.083 (2)0.2087 (17)0.632 (3)0.021*
O30.96322 (18)0.60240 (19)0.62300 (19)0.0174 (5)
H3O0.948 (3)0.641 (3)0.5535 (19)0.026*
O40.85256 (17)0.54263 (18)0.83553 (19)0.0132 (4)
H4O0.824 (3)0.517 (3)0.891 (2)0.020*
O50.70096 (17)−0.12504 (18)0.49502 (19)0.0153 (5)
N10.8572 (2)0.2954 (2)0.6738 (2)0.0118 (5)
H1N0.865 (3)0.245 (2)0.615 (2)0.014*
C10.7122 (2)0.1554 (3)0.6915 (3)0.0125 (6)
C20.7298 (2)0.0719 (3)0.5940 (3)0.0110 (6)
C30.6701 (2)−0.0452 (3)0.5783 (3)0.0122 (6)
C40.5921 (2)−0.0711 (3)0.6427 (3)0.0133 (6)
H40.5531−0.14670.62890.016*
C50.5715 (2)0.0190 (3)0.7308 (3)0.0146 (6)
C60.6309 (2)0.1276 (3)0.7580 (3)0.0140 (6)
H60.61860.18350.81930.017*
C70.7801 (2)0.2645 (3)0.7279 (3)0.0109 (6)
H70.76890.31610.79330.013*
C80.9361 (2)0.4026 (3)0.7066 (3)0.0110 (6)
C91.0558 (2)0.3539 (3)0.7151 (3)0.0129 (6)
H9A1.10600.42390.71590.016*
H9B1.08780.30790.79750.016*
C100.8904 (2)0.4963 (2)0.5932 (3)0.0120 (6)
H10A0.89040.45970.50940.014*
H10B0.81240.52010.58560.014*
C110.9462 (2)0.4610 (3)0.8413 (3)0.0121 (6)
H11A0.94920.39520.90520.014*
H11B1.01750.50760.87250.014*
C120.6500 (3)−0.2459 (3)0.4763 (3)0.0216 (7)
H12A0.6684−0.28790.56060.032*
H12B0.6791−0.29330.41700.032*
H12C0.5683−0.23800.43880.032*
U11U22U33U12U13U23
Br10.01640 (17)0.01891 (18)0.02421 (18)−0.00122 (13)0.01279 (13)0.00285 (13)
O10.0139 (11)0.0159 (11)0.0136 (10)−0.0018 (8)0.0089 (9)−0.0016 (8)
O20.0205 (12)0.0093 (10)0.0139 (11)0.0039 (9)0.0075 (9)0.0016 (8)
O30.0284 (13)0.0112 (11)0.0141 (11)−0.0034 (9)0.0091 (10)0.0029 (8)
O40.0141 (11)0.0153 (11)0.0145 (11)0.0004 (8)0.0108 (9)−0.0009 (9)
O50.0192 (12)0.0123 (10)0.0173 (11)−0.0026 (9)0.0099 (9)−0.0049 (9)
N10.0151 (13)0.0091 (12)0.0109 (13)−0.0001 (10)0.0034 (11)−0.0023 (10)
C10.0106 (15)0.0127 (15)0.0145 (15)−0.0002 (12)0.0043 (12)0.0015 (12)
C20.0079 (14)0.0123 (15)0.0110 (14)0.0025 (11)0.0008 (12)0.0037 (12)
C30.0094 (15)0.0149 (15)0.0126 (15)0.0007 (12)0.0038 (12)−0.0008 (12)
C40.0132 (16)0.0104 (14)0.0142 (15)−0.0009 (12)0.0013 (12)0.0009 (12)
C50.0122 (15)0.0180 (16)0.0147 (15)−0.0013 (12)0.0060 (12)0.0054 (12)
C60.0140 (15)0.0140 (15)0.0145 (15)0.0035 (12)0.0052 (12)0.0007 (12)
C70.0121 (15)0.0098 (14)0.0115 (14)0.0028 (11)0.0049 (12)0.0025 (11)
C80.0124 (15)0.0105 (14)0.0114 (14)−0.0008 (11)0.0055 (12)−0.0004 (11)
C90.0137 (16)0.0124 (15)0.0137 (15)−0.0019 (12)0.0056 (12)−0.0010 (11)
C100.0132 (14)0.0117 (14)0.0118 (14)0.0021 (12)0.0052 (11)−0.0028 (12)
C110.0123 (15)0.0117 (14)0.0128 (15)0.0016 (12)0.0048 (12)−0.0002 (11)
C120.0263 (19)0.0138 (16)0.0267 (18)−0.0091 (13)0.0112 (15)−0.0070 (13)
Br1—C51.902 (3)C4—C51.420 (4)
O1—C21.287 (3)C4—H40.9300
O2—C91.434 (3)C5—C61.355 (4)
O2—H2O0.818 (10)C6—H60.9300
O3—C101.419 (3)C7—H70.9300
O3—H3O0.815 (10)C8—C111.525 (4)
O4—C111.432 (3)C8—C101.529 (4)
O4—H4O0.819 (10)C8—C91.536 (4)
O5—C31.365 (3)C9—H9A0.9700
O5—C121.425 (3)C9—H9B0.9700
N1—C71.295 (4)C10—H10A0.9700
N1—C81.473 (4)C10—H10B0.9700
N1—H1N0.856 (10)C11—H11A0.9700
C1—C71.417 (4)C11—H11B0.9700
C1—C61.424 (4)C12—H12A0.9600
C1—C21.432 (4)C12—H12B0.9600
C2—C31.438 (4)C12—H12C0.9600
C3—C41.369 (4)
C9—O2—H2O109 (2)N1—C8—C10106.1 (2)
C10—O3—H3O105 (2)C11—C8—C10111.4 (2)
C11—O4—H4O107 (2)N1—C8—C9107.2 (2)
C3—O5—C12117.3 (2)C11—C8—C9107.0 (2)
C7—N1—C8127.9 (2)C10—C8—C9112.1 (2)
C7—N1—H1N115 (2)O2—C9—C8111.0 (2)
C8—N1—H1N117 (2)O2—C9—H9A109.4
C7—C1—C6118.9 (3)C8—C9—H9A109.4
C7—C1—C2120.1 (3)O2—C9—H9B109.4
C6—C1—C2121.0 (3)C8—C9—H9B109.4
O1—C2—C1123.0 (3)H9A—C9—H9B108.0
O1—C2—C3120.8 (3)O3—C10—C8107.6 (2)
C1—C2—C3116.2 (3)O3—C10—H10A110.2
O5—C3—C4125.2 (3)C8—C10—H10A110.2
O5—C3—C2112.7 (2)O3—C10—H10B110.2
C4—C3—C2122.1 (3)C8—C10—H10B110.2
C3—C4—C5119.2 (3)H10A—C10—H10B108.5
C3—C4—H4120.4O4—C11—C8112.6 (2)
C5—C4—H4120.4O4—C11—H11A109.1
C6—C5—C4121.8 (3)C8—C11—H11A109.1
C6—C5—Br1119.3 (2)O4—C11—H11B109.1
C4—C5—Br1118.8 (2)C8—C11—H11B109.1
C5—C6—C1119.3 (3)H11A—C11—H11B107.8
C5—C6—H6120.3O5—C12—H12A109.5
C1—C6—H6120.3O5—C12—H12B109.5
N1—C7—C1122.7 (3)H12A—C12—H12B109.5
N1—C7—H7118.6O5—C12—H12C109.5
C1—C7—H7118.6H12A—C12—H12C109.5
N1—C8—C11113.2 (2)H12B—C12—H12C109.5
C7—C1—C2—O1−7.6 (4)C2—C1—C6—C51.7 (4)
C6—C1—C2—O1175.5 (2)C8—N1—C7—C1−177.2 (3)
C7—C1—C2—C3170.7 (2)C6—C1—C7—N1178.9 (3)
C6—C1—C2—C3−6.2 (4)C2—C1—C7—N11.9 (4)
C12—O5—C3—C4−1.6 (4)C7—N1—C8—C1116.6 (4)
C12—O5—C3—C2177.7 (2)C7—N1—C8—C10−105.8 (3)
O1—C2—C3—O55.3 (4)C7—N1—C8—C9134.3 (3)
C1—C2—C3—O5−173.1 (2)N1—C8—C9—O245.9 (3)
O1—C2—C3—C4−175.4 (3)C11—C8—C9—O2167.6 (2)
C1—C2—C3—C46.2 (4)C10—C8—C9—O2−70.0 (3)
O5—C3—C4—C5177.5 (3)N1—C8—C10—O3178.8 (2)
C2—C3—C4—C5−1.8 (4)C11—C8—C10—O355.2 (3)
C3—C4—C5—C6−3.2 (4)C9—C8—C10—O3−64.6 (3)
C3—C4—C5—Br1175.5 (2)N1—C8—C11—O4−80.2 (3)
C4—C5—C6—C13.2 (4)C10—C8—C11—O439.2 (3)
Br1—C5—C6—C1−175.5 (2)C9—C8—C11—O4162.0 (2)
C7—C1—C6—C5−175.2 (3)
D—H···AD—HH···AD···AD—H···A
N1—H1N···O10.85 (2)1.90 (2)2.608 (3)140 (3)
O2—H2O···O4i0.82 (2)1.93 (2)2.741 (3)170 (3)
O3—H3O···O2ii0.81 (2)1.91 (2)2.704 (3)167 (4)
O4—H4O···O1iii0.82 (3)1.98 (3)2.760 (3)158 (3)
C7—H7···O1iii0.932.553.429 (4)158
C9—H9B···O3i0.972.513.242 (4)132
C11—H11B···O1iv0.972.393.353 (3)171
  15 in total

1.  Qmol: a program for molecular visualization on Windows-based PCs.

Authors:  J D Gans; D Shalloway
Journal:  J Mol Graph Model       Date:  2001       Impact factor: 2.518

2.  Single-Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln4 Squares.

Authors:  Chinmoy Das; Shefali Vaidya; Tulika Gupta; Jamie M Frost; Mattia Righi; Euan K Brechin; Marco Affronte; Gopalan Rajaraman; Maheswaran Shanmugam
Journal:  Chemistry       Date:  2015-09-18       Impact factor: 5.236

3.  Experimental and theoretical investigations of four 3d-4f butterfly single-molecule magnets.

Authors:  Hua-Hong Zou; Liang-Bing Sheng; Fu-Pei Liang; Zi-Lu Chen; Yi-Quan Zhang
Journal:  Dalton Trans       Date:  2015-10-07       Impact factor: 4.390

4.  Design, synthesis and characterization of novel binary V(V)-Schiff base materials linked with insulin-mimetic vanadium-induced differentiation of 3T3-L1 fibroblasts to adipocytes. Structure-function correlations at the molecular level.

Authors:  E Halevas; O Tsave; M P Yavropoulou; A Hatzidimitriou; J G Yovos; V Psycharis; C Gabriel; A Salifoglou
Journal:  J Inorg Biochem       Date:  2015-03-26       Impact factor: 4.155

5.  In vitro study of the insulin-mimetic behaviour of vanadium(IV, V) coordination compounds.

Authors:  Dieter Rehder; João Costa Pessoa; Carlos F G C Geraldes; MargaridaM C A Castro; Themistoklis Kabanos; Tamás Kiss; Beate Meier; Giovanni Micera; Lage Pettersson; Maria Rangel; Athanasios Salifoglou; Iztok Turel; Dongren Wang
Journal:  J Biol Inorg Chem       Date:  2001-12-19       Impact factor: 3.358

6.  Structure-specific adipogenic capacity of novel, well-defined ternary Zn(II)-Schiff base materials. Biomolecular correlations in zinc-induced differentiation of 3T3-L1 pre-adipocytes to adipocytes.

Authors:  O Tsave; E Halevas; M P Yavropoulou; A Kosmidis Papadimitriou; J G Yovos; A Hatzidimitriou; C Gabriel; V Psycharis; A Salifoglou
Journal:  J Inorg Biochem       Date:  2015-08-11       Impact factor: 4.155

7.  Slow magnetic relaxation in Co(III)-Co(II) mixed-valence dinuclear complexes with a Co(II)O5X (X = Cl, Br, NO3) distorted-octahedral coordination sphere.

Authors:  Vadapalli Chandrasekhar; Atanu Dey; Antonio J Mota; Enrique Colacio
Journal:  Inorg Chem       Date:  2013-04-04       Impact factor: 5.165

8.  Crystal structure refinement with SHELXL.

Authors:  George M Sheldrick
Journal:  Acta Crystallogr C Struct Chem       Date:  2015-01-01       Impact factor: 1.172

9.  Structure validation in chemical crystallography.

Authors:  Anthony L Spek
Journal:  Acta Crystallogr D Biol Crystallogr       Date:  2009-01-20

10.  The Cambridge Structural Database.

Authors:  Colin R Groom; Ian J Bruno; Matthew P Lightfoot; Suzanna C Ward
Journal:  Acta Crystallogr B Struct Sci Cryst Eng Mater       Date:  2016-04-01
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