research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

ISSN: 2056-9890

Structural characterization and DFT study of bis­­{(S)-2-[(2-hy­dr­oxy­benz­yl)amino]-3-(4-hy­dr­oxy­phen­yl)propano­ato-κ2N,O}(1,10-phenanthroline-κ2N,N′)cadmium(II) tetra­hydrate


aDepartment of Chemistry, Langat Singh College, Babasaheb Bhimrao Ambedkar Bihar University, Muzaffarpur, Bihar, India, bOndokuz Mayis University, Arts and Sciences Faculty, Department of Physics, 55139 Samsun, Turkey, and cDepartment of Chemistry, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., 01601 Kiev, Ukraine
*Correspondence e-mail:

Edited by D.-J. Xu, Zhejiang University (Yuquan Campus), China (Received 26 July 2018; accepted 15 August 2018; online 24 August 2018)

In the title compound, [Cd(C16H16O3)2(C12H8N2)]·4H2O, the Cd ion lies on a twofold rotation axis and is chelated by two monodeprotonated residues of the L-tyrosine-derived ligand (S)-2-[(2-hy­droxy­benz­yl)amino]-3-(4-hy­droxy­phen­yl)propanoic acid (L) in a κ2N,O amino acid chelating mode, exhibiting an (N,N′)-trans disposition, and by 1,10-phenanthroline in a κ2N,N′ mode. The latter ligand is also located about the twofold rotation axis that bisects the central six-members ring. The phenolic groups remain protonated and non-coordinating and take part as acceptors in the intra­molecular hydrogen bonds with the amino groups of the acido ligands. The Cd ion is six-coordinated in a distorted octa­hedral environment. In the crystal, O—H⋯O hydrogen bonds result in the formation of three-dimensional network structures. The title complex has also been characterized by IR and 1H NMR spectroscopy and DFT studies. The crystal studied was refined as an inversion twin.

1. Chemical context

Schiff bases are widely known as an important class of organic compounds and ligands in coordination chemistry. In recent years they have found applications in the fields of analytical chemistry, medicine and biological processes, displaying anti­fungal, anti­bacterial and anti­cancer activities (Przybylski et al., 2009[Przybylski, P., Huczynski, A., Pyta, K., Brzezinski, B. & Bartl, F. (2009). Curr. Org. Chem. 13, 124-148.]; Dhar & Taploo, 1982[Dhar, D. N. & Taploo, C. L. (1982). J. Sci. Ind. Res. 41, 501-506.]). Such systems are considered important ligands for coordination and supra­molecular compounds (Moroz et al., 2012[Moroz, Y. S., Demeshko, S., Haukka, M., Mokhir, A., Mitra, U., Stocker, M., Müller, P., Meyer, F. & Fritsky, I. O. (2012). Inorg. Chem. 51, 7445-7447.]). Coordination complexes with Schiff bases have attracted the inter­est of researchers in the areas of pharmaceutical, agriculture and industrial chemistry (Anis et al., 2013[Anis, I., Aslam, M., Noreen, Z., Afza, N., Hussain, A., Safder, M. & Chaudhry, A. H. (2013). Int. J. Curr. Pharm. Res. 5, 21-24.]). However, the use of Schiff base ligand systems having additional polar donor functions on contrary oximes (Sliva et al., 1997[Sliva, T. Yu., Duda, A. M., Głowiak, T., Fritsky, I. O., Amirkhanov, V. M., Mokhir, A. A. & Kozłowski, H. (1997). J. Chem. Soc. Dalton Trans. pp. 273-276.]; Penkova et al., 2010[Penkova, L., Demeshko, S., Pavlenko, V. A., Dechert, S., Meyer, F. & Fritsky, I. O. (2010). Inorg. Chim. Acta, 363, 3036-3040.]; Pavlishchuk et al., 2010[Pavlishchuk, A. V., Kolotilov, S. V., Zeller, M., Thompson, L. K., Fritsky, I. O., Addison, A. W. & Hunter, A. D. (2010). Eur. J. Inorg. Chem. pp. 4851-4858.]) is limited because of their enhanced reactivity or instability under complex formation (Casella & Gullotti, 1983[Casella, L. & Gullotti, M. (1983). Inorg. Chem. 22, 2259-2266.]). For example, Schiff bases derived from amino­hydroxamic acids undergo spontaneous cyclization resulting in the formation of 2-substituted 3-hy­droxy­imidazolidine-4-ones (Iskenderov et al., 2009[Iskenderov, T. S., Golenya, I. A., Gumienna-Kontecka, E., Fritsky, I. O. & Prisyazhnaya, E. V. (2009). Acta Cryst. E65, o2123-o2124.]). One of the ways to overcome this drawback is the reduction of such compounds to amines. The formed ligands are more conformationally flexible at the coordination site, thus not necessarily forming planar chelate rings (Koh et al., 1996[Koh, L. L., Ranford, J. O., Robinson, W. T., Svensson, J. O., Tan, A. L. C. & Wu, D. (1996). Inorg. Chem. 35, 6466-6472.]). In recent years it has also been found that phenanthroline, another ligand used in this study, has extensive important roles in a variety of fields (Faizi & Sharkina, 2015[Faizi, M. S. H. & Sharkina, N. O. (2015). Acta Cryst. E71, 195-198.]; Faizi et al., 2017[Faizi, M. S. H., Dege, N. & Malinkin, S. (2017). Acta Cryst. E73, 1393-1397.]). In this paper we report the synthesis and structure of a new cadmium complex with an L-tyrosine-derived ligand synthesized by the reduction of a Schiff base precursor.

[Scheme 1]

2. Structural commentary

The asymmetric unit of the title compound contains one half of the mononuclear complex of the mononuclear complex [Cd(L-H)2(phen)] and two water mol­ecules of solvation (Fig. 1[link]). The central CdII atom is located on a twofold rotation axis and coordinated by three chelating ligands, leading to a distorted octa­hedral CdN4O2 coordination sphere. The mixed-ligand complex contains one neutral phenanthroline ligand, bisected by the twofold rotation axis, and two residues of monodeprotonated tyrosine-derived ligands. The latter are coordinated in a κ2N,O classical amino acid chelating mode and have a C9 chiral atom, exhibiting an (N,N′)-trans disposition. The Cd—O and Cd—N bond lengths are similar, being 2.325 (5), 2.335 (6) and 2.323 (6) Å for Cd1—O4, Cd1—N1 and Cd1—N2, respectively. All three ligands form five-membered chelate rings. Unlike the chelate ring formed by the phenanthroline ligand which is virtually planar, the one created by the L residue exhibits an envelope conformation with the deviation of the Cd atom from the mean plane defined by the other four atoms being 1.0692 (3) Å. The N—Cd—O and N—Cd—N bite angles are 70.5 (2) and 72.0 (4)°, respectively. The phenolic O—H group remains protonated and non-coordinating, albeit participating in an extensive inter­molecular hydrogen-bonding network. An intra­molecular N1—H1⋯O1 hydrogen bond (Table 1[link]) occurs between the amino and phenolic groups of the same acido ligand.

Table 1
Hydrogen-bond geometry (Å, °)

N1—H1⋯O1 1.02 2.27 2.992 (10) 126
O6—H6A⋯O2i 0.83 2.51 3.276 (18) 152
O6—H6B⋯O3 0.83 2.43 2.851 (16) 112
O5—H5B⋯O2 0.82 2.00 2.675 (15) 140
O5—H5A⋯O6ii 0.83 2.31 2.709 (17) 110
O1—H1C⋯O5iii 0.82 1.98 2.652 (11) 138
O3—H3⋯O4iv 0.82 1.86 2.640 (9) 159
Symmetry codes: (i) x, y+1, z; (ii) y-1, x, -z; (iii) y, x+1, -z; (iv) [-y+{\script{3\over 2}}, x+{\script{1\over 2}}, z-{\script{1\over 4}}].
[Figure 1]
Figure 1
The mol­ecular structure of the title compound, showing the atom labelling for the asymmetric unit. Displacement ellipsoids are drawn at the 50% probability level. The unabelled atoms are related to the labelled atoms by symmetry operation y, x, −z

3. Supra­molecular features

The crystal structure of title compound is stabilized by inter­molecular O—H⋯O hydrogen bonds in which the phenolic groups of the L ligand and the water mol­ecules act as both donors and acceptors (Table 1[link], Fig. 2[link]). Hydrogen bonds formed by the water mol­ecules link the neighboring complex mol­ecules, forming a three-dimensional structure. ππ inter­actions take place between the central ring of phenanthroline and the C2–C7 aromatic rings of two tyrosine-derived ligands with centroid-to-centroid separations of 3.938 (6) Å.

[Figure 2]
Figure 2
The crystal packing of the title compound viewed along the a axis. Hydrogen bonds are shown as dashed lines (see Table 1[link] for details).

4. DFT study

Density functional theory (DFT) calculations were performed to investigate the electronic structure and characteristic vibrations. The calculated frequencies were found within the range, shown in Table 2[link]. Two factors could be responsible for the shift between the experimental and computed spectra (Fig. 3[link]). The first is the environmental factor as the DFT calculations were performed for the gas phase while the experimental data were obtained for the solid state. The second reason for the shift is that the calculated values are only harmonic frequencies while the experimental values contain both harmonic and anharmonic vibrational frequencies, but the pattern of the spectra appear to be quite similar in both cases, which validates the experimental vibrational spectrum. Some animated images of the characteristic vibrations with displacement vector are given in supporting information.

Table 2
Some selected experimental and calculated wavenumbers (cm−1)

Vibrational band Experimental Calculated
ν(N—H) stretching 3402 3414
ν(COO) anti-symmetrical stretching 1597 1598
ν(COO) symmetrical stretching 1459,1376 1487, 1396
ν(C—N) stretching 1266 1237
ν(N—H) wagging 853 885
ν(C—H) rocking 722 756
[Figure 3]
Figure 3
(a) Experimental vibrational spectrum and (b) B3LYP/DFT simulated vibrational spectrum.

5. Frontier mol­ecular orbital analysis

The LUMO and HOMO orbital energy parameters are accountable to a significant extent for the charge transfer, chemical reactivity and kinetic/thermodynamic stability of a mol­ecule. Metal complexes with a small energy gap (ΔE) between the HOMO and LUMO values are more polarizable, thereby acting as soft mol­ecules with a higher chemical reactivity. However, complexes with large energy gap offer greater stability and lower chemical reactivity than those with a small HOMO–LUMO energy gap. The DFT study revealed that the HOMO, HOMO-1, HOMO-2 and HOMO-3 energies are localized on the N1, N4, O2, O3, O6, O7, C8, C9, C35, C36 and C37 atoms of the amino acid ligand, partially localized on the Cd centre, namely dx2y2, as shown in Fig. 4[link]. In contrast, LUMO, LUMO+1, LUMO+2 and LUMO+3 are totally delocalized over phenanthroline moiety. It could be said that the HOMO and LUMO are mainly composed of σ and π-type orbitals, respectively, and that intra­molecular charge transfer occurred from the amino acid moiety to the phenanthroline moiety. The LUMO–HOMO gap of the complex was calculated to be 2.30 eV. The frontier mol­ecular orbital energies are given in Table 3[link].

Table 3
Calculated frontiermolecular orbital energies (eV)

FMO Energy
LUMO+3 −0.90
LUMO+2 −1.68
LUMO+1 −2.73
LUMO −2.78
HOMO −5.08
HOMO-1 −5.15
HOMO-2 −5.82
HOMO-3 −5.89
[Figure 4]
Figure 4
HOMO and LUMO frontier molecular orbitals with respective mol­ecular orbital number.

6. Hirshfeld surface analysis

The Hirshfeld surfaces of the title compound are illustrated in Fig. 5[link], depicting surfaces that have been mapped over a dnorm range of −0.5 to 1.5 a.u., shape index (−1.0 to 1.0 a.u.) and curvedness (−4.0 to 0.4 a.u.). The dnorm surface has a red–white–blue colour scheme, whereas deep-red spots highlight shorter contacts i.e. hydrogen bonding. The white areas represent contacts around the van der Waals separation, such as H⋯H contacts, and the blue regions are devoid of such close contacts. On the Hirshfeld surface mapped with the shape-index function, one can examine both red regions corresponding to C—H⋯π inter­actions as well as `bow-tie patterns', which indicate the presence of aromatic stacking (ππ) inter­actions. The curvedness surface indicates that the electron density of the surface curves around the mol­ecular inter­actions. The fingerprint plots, presented in Fig. 6[link], can be decomposed to highlight particular atom-pair close contacts. This itemization allows visualization of the contributions from different inter­action types, which overlap in the full fingerprint. For the title compound, the proportions of H⋯H, C⋯H, H⋯O and O⋯O inter­actions comprise 50.1%, 15.4%, 29.2% and 4.7%, respectively, of the total Hirshfeld surface for each mol­ecule.

[Figure 5]
Figure 5
Hirshfeld surfaces mapped over (a) dnorm, (b) shape index and (c) curvedness.
[Figure 6]
Figure 6
The two-dimensional fingerprint plots of inter­atomic inter­actions showing the percentage contributions to the Hirshfeld surface.

7. Database survey

A search in the Cambridge Structural Database (Version 5.39, last update February 2018; Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) for structures with a CdII ion coordinated by 2-hy­droxy­benzyl derivatives of amino acids yielded only one hit (refcode WARLIL; Lou et al., 2005[Lou, B.-Y., Yuan, D.-Q., Han, L., Wu, B.-L. & Hong, M.-C. (2005). Chin. J. Struct. Chem. 24, 759-764.]), a mononuclear complex with N-(2-hy­droxy­benz­yl)-D,L-aspartic acid. In this complex, the doubly deprotonated (by the phenolic and β-carb­oxy­lic groups) residue of the ligand is coordinated in an (O,N,O′)-tridentate mode including the phenolic oxygen, unlike the title compound in which the phenolic group is non-coordinating. The second oxygen atom of the β-carb­oxy­lic group bridges the neighboring mononuclear Cd units into a one-dimensional chain. In addition, there are few structures of complexes with zinc or cadmium analogues (refcodes AZIROQ, AZIRUW, NOLYIW, NOLYOC) with 2-hy­droxy­benzyl derivatives of alanine. In all these complexes, the ligand is also coordinated in an (O,N,O′)-tridentate manner, with an additional μ2-function of the phenolic oxygen, which results in the formation of a Zn2O2 binuclear core in all cases (Lou et al., 2004[Lou, B.-Y., Yuan, D.-Q., Wang, R.-H., Xu, Y., Wu, B.-L., Han, L. & Hong, M.-C. (2004). J. Mol. Struct. 698, 87-91.]; Ranford et al., 1998[Ranford, J. D., Vittal, J. J. & Wu, D. (1998). Angew. Chem. Int. Ed. 37, 1114-1116.]).

8. Synthesis and crystallization

Synthesis of (S)-2-[(2-hy­droxy­benz­yl)amino]-3-(4-hy­droxy­phen­yl)propanoic acid (L)

A methano­lic solution of o-salicyl­aldehyde (1.18 g, 5.51 mmol) was added dropwise to a stirring solution of L-tyrosine (1.00 g, 5.52 mmol) and LiOH·H2O (0.23 g, 5.50 mmol) in methanol (25 mL). Stirring was continued for 2 h, followed by the addition of sodium borohydride (0.21 g, 5.55 mmol) with further stirring for 1 h. The solvent was evaporated and the resulting sticky mass was dissolved in water and acidified with dilute HCl. The pH of the solution was maintained between 5–7. The ligand precipitated as a brown solid. It was washed thoroughly with water and MeOH after filtration and dried in a vacuum desiccator. Yield 1.60 g (76%). m/z (ESI–MS, [M − H]) 379.087 (calculated 379.084). IR (KBr, cm−1), ν(COO)asym 1579 (s), ν(COO)sym 1394 (s). 1H NMR (CD3OD, ppm): Hcp.o (4.10, d, 1H), Hcp.o (4.13, d, 1H), Hcp (3.99, s, 5H), Hcp.m (4.03, s, 2H), Ha (3.51, d, 1H, Ja,a = 12.8 Hz), Ha,c′ (3.22, d, 1H), Hb (3.31, m, 1H), Hc (2.94, dd, 1H), Hc,c′ (2.67, dd, 1H), Hd,d′ (6.96, d, 2H), He,e′ (6.59, d, 2H). As a result of geminal coupling, Hc split into two non-equivalent Hc and Hc′.

Synthesis of [Cd(L-H)2(phen)]·4H2O

A methano­lic solution of Cd(NO3)2·6H2O (0.107 g, 0.348 mmol) was added to a stirred 15 ml methano­lic solution of L (0.200 g, 0.696 mmol) and NaOH (0.028 g, 0.696 mmol), followed by addition of phenanthroline monohydrate (0.063 g, 0.348 mmol) in 5 ml of MeOH. A clear solution was obtained. After 20 minutes stirring a precipitate appeared. The reaction mixture was evaporated under reduced pressure. The residue was washed with water and subsequently diethyl ether, and finally dried under vacuum. Prismatic crystals suitable for X-ray data collection were obtained by slow evaporation of methanol. Empirical formula [Cd(L)2(phen)]·4H2O (2). Yield 49%. [Cd(L)2(phen)]·4H2O: IR (KBr, cm−1) ν(COO)assym 1651, ν(COO)sym 1381, ν(phenolic, CO) 1250. 1H NMR [Cd(L)2(phen)]·4H2O] (DMSO, 400 MHz. ppm): 2.4 (s, br, 1Hg), 2.5 (s, br, 1Hg'), 2.8 (s, br, 1Hf), 3.1 (s, br, 1He), 3.4 (s, br, 1He′), 6.1 (s, br, 2Ha,c), 6.5 (s, br, 2Hb,d), 7.0 (s, br, 4H), 7.9 (s, br, 2Hn), 8.0 (s, br, 2Hm), 8.7 (s, br, 2Hl), 9.0 (s, br, 2Hk). ESI–Mass (-ve) 929.2 (calculated 929.2).

9. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 4[link]. The O—H H atoms were located in a difference-Fourier map and constrained to ride on their parent atoms, with O—H = 0.82 Å and with Uiso(H) = 1.5Ueq(O). All C-bound H atoms were positioned geometrically and refined using a riding model with C—H = 0.93 Å and with Uiso(H) = 1.2Ueq(C). The crystal studied was refined as an inversion twin.

Table 4
Experimental details

Crystal data
Chemical formula [Cd(C16H16O3)2(C12H8N2)]·4H2O
Mr 937.26
Crystal system, space group Tetragonal, P43212
Temperature (K) 296
a, c (Å) 12.4171 (2), 28.4151 (10)
V3) 4381.2 (2)
Z 4
Radiation type Mo Kα
μ (mm−1) 0.57
Crystal size (mm) 0.20 × 0.14 × 0.11
Data collection
Diffractometer Bruker SMART CCD area detector
No. of measured, independent and observed [I > 2σ(I)] reflections 28145, 4310, 3599
Rint 0.049
(sin θ/λ)max−1) 0.617
R[F2 > 2σ(F2)], wR(F2), S 0.053, 0.159, 1.04
No. of reflections 4310
No. of parameters 260
No. of restraints 18
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.75, −0.73
Absolute structure Refined as an inversion twin
Absolute structure parameter 0.02 (7)
Computer programs: SMART (Bruker, 2012[Bruker (2012). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SAINT (Bruker, 2012[Bruker (2012). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]), SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2016 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]).

Supporting information

Computing details top

Data collection: SMART (Bruker, 2012); cell refinement: SAINT (Bruker, 2012); data reduction: SAINT (Bruker, 2012); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXL2016 (Sheldrick, 2015); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Bis{(S)-2-[(2-hydroxybenzyl)amino]-3-(4-hydroxyphenyl)propanoato-\ κ2N,O}(1,10-phenanthroline-κ2N,N')cadmium(II) tetrahydrate top
Crystal data top
[Cd(C16H16O3)2(C12H8N2)]·4H2ODx = 1.421 Mg m3
Dm = 1.421 Mg m3
Dm measured by ?
Mr = 937.26Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P43212Cell parameters from 5678 reflections
a = 12.4171 (2) Åθ = 2.7–21.8°
c = 28.4151 (10) ŵ = 0.56 mm1
V = 4381.2 (2) Å3T = 296 K
Z = 4Prism, colorless
F(000) = 19360.20 × 0.14 × 0.11 mm
Data collection top
Bruker SMART CCD area detector
3599 reflections with I > 2σ(I)
Radiation source: sealed tubeRint = 0.049
Graphite monochromatorθmax = 26.0°, θmin = 2.2°
phi and ω scansh = 1515
28145 measured reflectionsk = 1415
4310 independent reflectionsl = 3335
Refinement top
Refinement on F2Hydrogen site location: mixed
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.053 w = 1/[σ2(Fo2) + (0.1136P)2 + 0.4952P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.159(Δ/σ)max = 0.001
S = 1.03Δρmax = 0.75 e Å3
4310 reflectionsΔρmin = 0.73 e Å3
260 parametersAbsolute structure: Refined as an inversion twin
18 restraintsAbsolute structure parameter: 0.02 (7)
Special details top

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.

Refinement. Refined as a 2-component inversion twin.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
O50.5065 (7)0.7805 (10)0.0219 (6)0.192
O60.7175 (8)1.6168 (10)0.0556 (5)0.192
Cd10.97964 (3)0.97964 (3)0.0000000.0540 (2)
N10.8171 (5)1.0589 (5)0.0225 (2)0.0623 (15)
C90.7269 (6)0.9904 (7)0.0079 (3)0.079 (3)
C140.6231 (8)1.3351 (11)0.0780 (3)0.101 (4)
C110.6180 (7)1.1475 (10)0.0258 (3)0.089 (3)
C120.6472 (8)1.1455 (10)0.0743 (3)0.094 (3)
C150.5947 (9)1.3356 (12)0.0318 (4)0.107 (4)
C160.5977 (8)1.2496 (13)0.0067 (4)0.106 (4)
C100.6175 (6)1.0501 (10)0.0045 (3)0.095 (3)
C130.6449 (10)1.2404 (12)0.0991 (4)0.107 (4)
C30.9033 (7)1.2746 (7)0.0637 (3)0.071 (2)
C20.9025 (6)1.1740 (7)0.0832 (2)0.0603 (18)
C40.9866 (8)1.3478 (7)0.0716 (3)0.083 (2)
C70.9869 (7)1.1450 (7)0.1124 (3)0.073 (2)
C10.8112 (7)1.0959 (7)0.0718 (3)0.067 (2)
C61.0698 (8)1.2195 (10)0.1198 (3)0.089 (3)
C51.0699 (8)1.3199 (9)0.0987 (3)0.083 (2)
C171.1960 (8)0.9751 (11)0.0666 (4)0.099 (3)
C211.1830 (6)1.1235 (7)0.0185 (3)0.076 (2)
C201.2837 (9)1.1652 (11)0.0351 (5)0.110 (4)
C191.3356 (10)1.1048 (14)0.0710 (5)0.114 (5)
C181.2943 (10)1.0187 (16)0.0844 (5)0.120 (5)
O10.8199 (7)1.2984 (6)0.0340 (3)0.102 (2)
O30.6285 (7)1.4344 (8)0.1026 (2)0.123 (3)
N21.1419 (5)1.0314 (6)0.0338 (2)0.0660 (16)
C80.7555 (8)0.9297 (9)0.0391 (4)0.093 (3)
O20.6804 (10)0.8780 (10)0.0575 (5)0.192
O40.9391 (6)0.8474 (5)0.0552 (2)0.0880 (19)
C221.3163 (12)1.2687 (12)0.0170 (5)0.142 (8)
Atomic displacement parameters (Å2) top
Cd10.0535 (3)0.0535 (3)0.0550 (4)0.0104 (3)0.0039 (2)0.0039 (2)
N10.049 (3)0.067 (4)0.071 (4)0.010 (3)0.001 (3)0.008 (3)
C90.055 (4)0.097 (6)0.084 (6)0.024 (4)0.008 (4)0.017 (5)
C140.081 (6)0.158 (11)0.064 (5)0.045 (7)0.015 (4)0.006 (6)
C110.051 (4)0.140 (10)0.075 (6)0.001 (5)0.006 (4)0.000 (6)
C120.087 (6)0.121 (9)0.074 (6)0.025 (6)0.012 (5)0.002 (6)
C150.089 (7)0.166 (11)0.065 (6)0.030 (7)0.011 (5)0.001 (6)
C160.072 (5)0.184 (12)0.061 (6)0.030 (6)0.018 (5)0.016 (7)
C100.050 (4)0.151 (9)0.082 (6)0.015 (5)0.003 (4)0.014 (7)
C130.109 (8)0.151 (11)0.060 (5)0.033 (8)0.016 (5)0.004 (6)
C30.060 (4)0.075 (5)0.078 (5)0.005 (4)0.000 (4)0.002 (4)
C20.062 (4)0.071 (4)0.048 (4)0.001 (3)0.008 (3)0.010 (3)
C40.088 (6)0.075 (5)0.086 (6)0.023 (5)0.006 (5)0.004 (4)
C70.077 (5)0.086 (5)0.056 (4)0.008 (5)0.002 (4)0.010 (3)
C10.062 (4)0.067 (4)0.072 (5)0.008 (4)0.007 (4)0.009 (4)
C60.069 (5)0.121 (9)0.076 (6)0.014 (6)0.019 (4)0.033 (6)
C50.069 (5)0.084 (6)0.097 (7)0.016 (5)0.006 (5)0.015 (5)
C170.093 (7)0.122 (8)0.082 (6)0.033 (7)0.025 (5)0.023 (6)
C210.060 (4)0.088 (6)0.079 (5)0.024 (4)0.020 (3)0.037 (4)
C200.070 (6)0.121 (9)0.138 (10)0.032 (6)0.033 (6)0.073 (8)
C190.071 (7)0.153 (13)0.119 (10)0.003 (8)0.005 (7)0.053 (10)
C180.079 (7)0.173 (14)0.107 (9)0.021 (9)0.030 (6)0.038 (10)
O10.092 (5)0.086 (5)0.126 (6)0.014 (4)0.027 (5)0.016 (4)
O30.131 (7)0.151 (8)0.086 (4)0.041 (6)0.013 (4)0.004 (5)
N20.054 (3)0.080 (4)0.064 (3)0.008 (3)0.006 (3)0.019 (3)
C80.067 (5)0.113 (8)0.098 (7)0.036 (5)0.029 (5)0.007 (6)
O40.119 (5)0.070 (4)0.075 (4)0.013 (3)0.022 (4)0.018 (3)
C220.100 (11)0.134 (15)0.19 (2)0.067 (12)0.036 (10)0.068 (12)
Geometric parameters (Å, º) top
O5—H5B0.8179C3—O11.367 (11)
O5—H5A0.8319C3—C41.394 (12)
O6—H6A0.8336C2—C71.384 (12)
O6—H6B0.8313C2—C11.527 (10)
Cd1—N22.323 (6)C4—C51.336 (14)
Cd1—N2i2.323 (6)C4—H40.9300
Cd1—O4i2.325 (5)C7—C61.399 (13)
Cd1—O42.325 (5)C7—H70.9300
Cd1—N12.335 (6)C1—H1A0.9700
Cd1—N1i2.335 (6)C1—H1B0.9700
N1—C91.466 (9)C6—C51.383 (15)
N1—C11.475 (10)C6—H60.9300
C9—C101.551 (13)C17—N21.345 (12)
C9—C81.573 (13)C17—C181.428 (17)
C14—C131.347 (17)C21—N21.325 (11)
C14—C151.359 (14)C21—C201.433 (13)
C14—O31.419 (14)C21—C21i1.483 (19)
C11—C161.402 (17)C20—C191.42 (2)
C11—C121.426 (14)C20—C221.442 (19)
C11—C101.485 (14)C19—C181.25 (2)
C12—C131.372 (17)C19—H190.9300
C15—C161.285 (17)O1—H1C0.8200
C16—H160.9300C8—O4i1.235 (12)
C10—H10A0.9700C8—O21.248 (13)
C10—H10B0.9700C22—C22i1.28 (3)
C3—C21.367 (12)
H6A—O6—H6B105.0C2—C3—O1116.2 (8)
N2—Cd1—N2i72.0 (4)C2—C3—C4122.4 (8)
N2—Cd1—O4i162.0 (2)O1—C3—C4121.4 (8)
N2i—Cd1—O4i96.0 (3)C3—C2—C7118.3 (8)
N2—Cd1—O496.0 (3)C3—C2—C1120.0 (8)
N2i—Cd1—O4162.0 (2)C7—C2—C1121.6 (8)
O4i—Cd1—O498.5 (4)C5—C4—C3119.9 (9)
N2—Cd1—N1121.3 (2)C5—C4—H4120.0
N2i—Cd1—N189.2 (2)C3—C4—H4120.0
O4i—Cd1—N170.5 (2)C2—C7—C6118.4 (9)
O4—Cd1—N185.7 (2)C2—C7—H7120.8
N2—Cd1—N1i89.2 (2)C6—C7—H7120.8
N2i—Cd1—N1i121.3 (2)N1—C1—C2111.3 (6)
O4i—Cd1—N1i85.7 (2)N1—C1—H1A109.4
O4—Cd1—N1i70.5 (2)C2—C1—H1A109.4
N1—Cd1—N1i143.5 (3)N1—C1—H1B109.4
C9—N1—C1114.3 (6)C2—C1—H1B109.4
C9—N1—Cd1109.8 (5)H1A—C1—H1B108.0
C1—N1—Cd1115.7 (5)C5—C6—C7122.1 (9)
Cd1—N1—H1102.0C4—C5—C6118.8 (9)
N1—C9—C10114.1 (8)C4—C5—H5120.6
N1—C9—C8110.2 (6)C6—C5—H5120.6
C10—C9—C8112.0 (7)N2—C17—C18118.3 (13)
C8—C9—H9106.7N2—C21—C20122.7 (10)
C13—C14—C15119.1 (13)N2—C21—C21i118.1 (5)
C13—C14—O3122.0 (9)C20—C21—C21i119.2 (8)
C15—C14—O3118.9 (11)C19—C20—C21116.2 (12)
C16—C11—C12115.8 (11)C19—C20—C22126.8 (12)
C16—C11—C10120.8 (9)C21—C20—C22116.7 (14)
C12—C11—C10123.2 (11)C18—C19—C20119.0 (12)
C13—C12—C11118.4 (11)C18—C19—H19120.5
C11—C12—H12120.8C19—C18—C17124.7 (14)
C16—C15—C14121.6 (13)C19—C18—H18117.6
C15—C16—C11122.8 (10)C14—O3—H3109.5
C15—C16—H16118.6C21—N2—C17118.9 (8)
C11—C16—H16118.6C21—N2—Cd1116.0 (6)
C11—C10—C9114.9 (7)C17—N2—Cd1125.1 (7)
C11—C10—H10A108.5O4i—C8—O2125.7 (12)
C9—C10—H10A108.5O4i—C8—C9118.5 (7)
C11—C10—H10B108.5O2—C8—C9115.8 (11)
C9—C10—H10B108.5C8i—O4—Cd1115.0 (6)
H10A—C10—H10B107.5C22i—C22—C20123.5 (8)
C14—C13—C12121.7 (10)C22i—C22—H22118.3
C1—N1—C9—C1068.7 (9)Cd1—N1—C1—C255.7 (8)
Cd1—N1—C9—C10159.4 (6)C3—C2—C1—N169.5 (11)
C1—N1—C9—C8164.2 (7)C7—C2—C1—N1109.1 (8)
Cd1—N1—C9—C832.3 (8)C2—C7—C6—C50.4 (13)
C16—C11—C12—C135.1 (15)C3—C4—C5—C62.2 (15)
C10—C11—C12—C13180.0 (10)C7—C6—C5—C42.1 (15)
C13—C14—C15—C166.5 (18)N2—C21—C20—C193.0 (13)
O3—C14—C15—C16173.7 (11)C21i—C21—C20—C19179.1 (10)
C14—C15—C16—C117.6 (18)N2—C21—C20—C22177.2 (10)
C12—C11—C16—C156.7 (16)C21i—C21—C20—C224.9 (15)
C10—C11—C16—C15178.2 (10)C21—C20—C19—C183.0 (17)
C16—C11—C10—C9116.7 (11)C22—C20—C19—C18176.5 (14)
C12—C11—C10—C957.9 (12)C20—C19—C18—C171 (2)
N1—C9—C10—C1154.2 (11)N2—C17—C18—C191.6 (19)
C8—C9—C10—C1171.9 (11)C20—C21—N2—C170.7 (12)
C15—C14—C13—C125.1 (18)C21i—C21—N2—C17178.6 (9)
O3—C14—C13—C12175.2 (11)C20—C21—N2—Cd1178.6 (6)
C11—C12—C13—C144.7 (18)C21i—C21—N2—Cd10.7 (11)
O1—C3—C2—C7178.1 (8)C18—C17—N2—C211.6 (13)
C4—C3—C2—C70.9 (13)C18—C17—N2—Cd1179.2 (7)
O1—C3—C2—C10.6 (12)N1—C9—C8—O4i5.4 (13)
C4—C3—C2—C1177.8 (8)C10—C9—C8—O4i133.6 (10)
C2—C3—C4—C50.7 (15)N1—C9—C8—O2172.5 (10)
O1—C3—C4—C5176.3 (9)C10—C9—C8—O244.3 (13)
C3—C2—C7—C61.1 (11)C19—C20—C22—C22i177 (2)
C1—C2—C7—C6177.6 (7)C21—C20—C22—C22i10 (3)
C9—N1—C1—C2175.3 (8)
Symmetry code: (i) y, x, z.
Hydrogen-bond geometry (Å, º) top
N1—H1···O11.022.272.992 (10)126
O6—H6A···O2ii0.832.513.276 (18)152
O6—H6B···O30.832.432.851 (16)112
O5—H5B···O20.822.002.675 (15)140
O5—H5A···O6iii0.832.312.709 (17)110
O1—H1C···O5iv0.821.982.652 (11)138
O3—H3···O4v0.821.862.640 (9)159
Symmetry codes: (ii) x, y+1, z; (iii) y1, x, z; (iv) y, x+1, z; (v) y+3/2, x+1/2, z1/4.
Some selected experimental and calculated wavenumbers (cm-1) top
Vibrational bandExperimentalCalculated
ν(N—H) stretching34023414
ν(COO) anti-symmetrical stretching15971598
ν(COO) symmetrical stretching1459,13761487, 1396
ν(C—N) stretching12661237
ν(N—H) wagging853885
ν(C—H) rocking722756
Calculated frontiermolecular orbital energies (eV) top
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
Atomic displacement parameters (Å2) top


The authors are grateful to the Department of Chemistry, Taras Shevchenko National University of Kyiv, 64, Vladimirska Str., Kiev, Ukraine, for financial support, and Dr Pratik Sen and Dr Manabendra Ray for valuable discussions.


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