Crystal structure of bis­{2-hy­droxy-N′-[1-(pyrazin-2-yl)ethyl­idene]benzohydrazidato}cadmium(II)

Yang, P.; Xie, X.-B.; Shi, Q.-S.

doi:10.1107/S2056989021000657

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ISSN: 2056-9890

Volume 77| Part 2| February 2021| Pages 153-157

https://doi.org/10.1107/S2056989021000657

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Crystal structure of bis{2-hydroxy-N′-[1-(pyrazin-2-yl)ethylidene]benzohydrazidato}cadmium(II)

Ping Yang,^a Xiao-Bao Xie ^a ^* and Qing-Shan Shi ^a

^aGuangdong Provincial Key Laboratory of Microbial Culture Collection and Application, State Key Laboratory of Applied Microbiology Southern China, Guangdong Institute of Microbiology, Guangdong Academy of Sciences, Guangzhou 510070, People's Republic of China
^*Correspondence e-mail: 191723030@qq.com

Edited by M. Zeller, Purdue University, USA (Received 5 January 2021; accepted 19 January 2021; online 22 January 2021)

In the title complex molecule, [Cd(C₁₃H₁₁N₄O₂)₂], the Cd atom is coordinated in a distorted octahedral geometry by two tridentate ligands synthesized from 2-hydroxybenzohydrazide and 1-(pyrazin-2-yl)ethan-1-one. The molecule has twofold crystallographic symmetry and is isomorphous to its Mn, Co, Ni, Cu and Zn counterparts.

Keywords: crystal structure; cadmium(II) complex; hydrazone derivatives.

CCDC reference: 2051612

1. Chemical context

Aroylhydrazones are competent ligands for various functional coordination compounds. They have the ability of polydentate coordination and are often used as building units of polynuclear magnetic compounds (Huang et al., 2016 ; Zhang et al., 2010 ). Aroylhydrazones can exhibit keto–enol tautomerism, and the uncomplexed aroylhydrazone ligand is commonly found in its keto form (Kalinowski et al., 2008 ; Tai & Feng, 2008 ). Metal complexes of deprotonated aroylhydrazones have been used in various catalytic and biological applications (Sutradhar et al., 2013 ; Yang et al., 2019 ; Yang, Chen et al., 2020 ). Aroylhydrazones synthesized from arylhydrazides and aromatic aldehydes/ketones with a nitrogen or oxygen atom in the ortho position can coordinate to metals in a tridentate chelating mode (Cindrić et al., 2017 ; Patel et al., 2018 ; You et al., 2018 ), and they have been used as probes and chemosensors for various metal ions. For example, the aroylhydrazone ligand containing a 4-(dimethylamino)phenylpropenyl or benzamide substituent specifically senses Al³⁺, Cd²⁺ (Kar et al., 2015 ) and Ni²⁺ ions (Manna et al., 2019 ) through significant changes in their absorption and emission spectroscopic behaviour after complexation with the metal ions. Here, we study the coordination attributes of an aroylhydrazone with cadmium.

2. Structural commentary

In the title complex, the Cd²⁺ ion possesses a distorted octahedral N₄O₂ coordination environment, which is generated by the two deprotonated ligands L (Fig. 1). The complex is bisected by a twofold crystallographic axis with the two ligands being equivalent by crystal symmetry. The complex is isomorphous to its Mn, Co, Ni, Cu and Zn counterparts (Yang et al., 2019; Yang, Zhang et al., 2020 ). The O2—C7 and C7—N1 bond lengths in the title compound are 1.255 (5) Å and 1.355 (5) Å, respectively, indicating that the coordinated ligands are closer to the keto than the enol form, but are slightly more delocalized than in the purely keto tautomeric form as found in the free ligand form of similar aroylhydrazones. The free ligand L has not yet been structurally described, but the equivalent bond distances in e.g. 2-hydroxy-N′-[1-(3-methylpyrazin-2-yl)ethylidene]benzohydrazide, L¹, with one more methyl group on pyrazine (Tai & Feng, 2008), were reported as 1.235 and 1.340 Å, respectively.

Figure 1
The molecular structure of [Cd(C₁₃H₁₁N₄O₂)₂] with displacement ellipsoids at the 30% probability level. Symmetry code: (xi) −x + 1, −y + 1, z.

The ligand in the title complex is close to planar (the mean deviation from the average plane is 0.0763 Å). The largest deviation from planarity is only 0.145 (3) Å, observed for atom C12 of the pyrazine ring. The Cd1 atom is nearly coplanar with each of the two ligands (deviation = 0.316 Å). The dihedral angle between the two ligands is 78.705 (16)°. The oxygen atom O1 of the phenolic group remains protonated, and forms an intramolecular hydrogen bond O1—H1⋯N1 [2.557 (4) Å, 146 (7)°].

The intramolecular hydrogen bond stabilizes the planar geometry of the ligand. The presence of the intramolecular hydrogen bond does also appear to affect the propensity of the metal complex towards crystallization. We found that when the hydroxyl group is in the meta or para position {3-hydroxy-N′-[1-(pyrazin-2-yl)ethylidene]benzohydrazide (L²) or 4-hydroxy-N′-[1-(pyrazin-2-yl)ethylidene]benzohydrazide (L³)}, where no intramolecular hydrogen bond can be formed, crystallization is substantially delayed and a much longer time is required for the complexes to crystallize.

In the isomorphous Mn, Co, Ni, Cu and Zn M(L)₂ complexes, the ligands are also close to planar (the mean deviation from the average plane ranges from 0.0608 to 0.0754 Å). In dimethylformamide (DMF)-solvated Ni and Cu complexes of similar ligands L² {3-hydroxy-N′-[1-(pyrazin-2-yl)ethylidene]benzohydrazide} and L³ {4-hydroxy-N′-[1-(pyrazin-2-yl)ethylidene]benzohydrazide} [M(L²)₂]·2(DMF) (M = Ni, Cu and Zn) and [Cu(L³)₂]·2(DMF) (M = Ni and Cu), the planarity of the ligands is reduced, with a mean deviation from the average plane between 0.2164 to 0.2290 Å.

In the title complex, the Cd1—N3, Cd1—N2 and Cd1—O2, bond lengths are 2.356 (3), 2.273 (3) and 2.277 (4) Å, respectively, which are close to typical for Cd²⁺ complexes closely related to the title compound, such as bis{N′-[1-(pyridin-2-yl)ethylidene]benzohydrazidato}cadmium(II) (Sen et al., 2005 ), bis{2-[2-(pyridin-2-ylmethylene)hydrazine-1-carbonyl]benzenesulfonamide}cadmium(II) (Sousa-Pedrares et al., 2008 ) and bis[N′-(2-hydroxybenzoyl)picolinohydrazonamide]cadmium(II) (Xu et al., 2014 ), bis{N′-[di(pyridin-2-yl)methylene]benzohydrazidato}cadmium(II) (Kuriakose et al., 2017 ) [the range of N—Cd is 2.360 (12)–2.4135 (11) Å, N(middle)—Cd 2.225 (2)–2.295 (2) Å, O—Cd 2.240 (2)–2.358 (10) Å].

The coordination environment of the Cd ion is highly distorted octahedral, caused by the rigidity of the ligand and its small N—N and N—O bite angles of only 69.86 (11) (N3—Cd1—N2) and 69.83 (11)° (N2—Cd1—O2). As a result, the N—Cd—O, N–Cd—N and O—Cd—O angles in the title compound deviate substantially from the values of 180 and 90° expected for an idealized octahedral complex. The trans angles range from 139.07 (10) to 170.63 (17)°, while the cis angles vary between 69.83 (11) and 117.27 (11)°.

Bond distances and angles within the isomorphous series of the Mn, Co, Ni, Cu, Zn, and Cd complexes follow a trend consistent with the metal ion radius (Table 1). Bond lengths first decrease and then increase, with a minimum value for the Ni or Cu complexes, and a maximum for the title cadmium complex as a result of its substantially larger ion radius as the only 4d complex of the series. The trend of the N—M—O angle (within the same ligand) is opposite to that of the metal ion radius, and first increases and then decreases, with the maximum value appearing for the Ni complex (Brines et al., 2007 ; Reger et al., 2012 ; Sola et al., 1994 ; Database of Ionic Radii, 2020 ). The distortion from octahedral geometry increases with ion radius, and is most pronounced for the title cadmium complex, as can be seen for e.g. the N(mid)—M—N(mid) angles, which range from 172.30 to 174.46° for the 3d complexes, while the value for the 4d Cd complex is 170.63 (17)°.

Table 1
Comparative analysis of ion radius and the bond lengths and bond angles of coordination polyhedra (Å, °)

	Mn²⁺	Co²⁺	Ni²⁺	Cu²⁺	Zn²⁺	Cd²⁺
Ion radius	0.83	0.745	0.69	0.73	0.74	0.95
M—N	2.283	2.151	2.114	2.192	2.215	2.356
M—N(mid)	2.193	2.050	1.994	1.979	2.074	2.273
M—O	2.148	2.102	2.097	2.130	2.125	2.277
N(mid)—M—N(mid)	174.46	172.30	173.86	173.64	173.97	170.63
N—M—O (within the same ligand)	142.08	148.53	153.95	151.98	148.84	139.07
O—M—O	99.76	102.86	95.26	97.43	98.87	95.39
N(mid)—M—O (within different ligands)	104.25	99.33	98.33	98.79	100.49	103.58
CSD refcode	CIZJED^a	CIZGOK^b	CIZGAW^c	COYVUK^d	CIZFUP^e	2051612^f
Notes: (a) Yang (2019 ); (b) Yang (2019); (c) Yang, Zhang et al. (2020); (d) Yang, Zhang et al. (2019); (e) Yang (2019); (f) this work.

3. Supramolecular features

Two types of weak intermolecular interactions, C—H⋯N and C—H⋯O hydrogen bonds and π–π stacking and C—H⋯π interactions, have a significant impact on the packing of the complexes in the solid state. Three intermolecular hydrogen bonds (Table 2) are observed in the crystal. Two hydrogen bonds (C10—H10⋯O2ⁱⁱ and C12—H12⋯O1ⁱ, symmetry code given in Table 2; Fig. 2a) form a sheet parallel to the crystallographic bc plane. Adjacent sheets of the complex are connected to each other via a weak C4—H4⋯N4ⁱⁱⁱ interaction, forming a three-dimensional network (Table 2 and Fig. 2b). Intermolecular π–π stacking is observed between the pyrazine rings and benzene rings of ligands in neighbouring complexes [the centroid–centroid distance between N3–N4/C9–C12 and C1–C6^vi [symmetry code: (vi) x, y − $[{1\over 2}]$ , z − $[{1\over 2}]$ ] is 3.641 (2) Å, with a slippage of 1.252 Å, Fig. 3. Intermolecular interactions between carbon atoms C13 and the π ring of lateral benzene rings and pyrazine rings in neighbouring molecules are found, namely C13—H13B⋯Cg1^v [2.71 Å, Cg1 is the centroid of the C1–C6 ring; symmetry code: (v) −x + $[{3\over 2}]$ , y, z − $[{1\over 2}]$ ] and C13–H13A⋯Cg2^iv [2.86 Å, Cg2 is the centroid of the N3–N4/C9–C12; symmetry code: (iv) −x + $[{3\over 2}]$ , y, z + $[{1\over 2}]$ ] (Fig. 3).

Table 2
Hydrogen-bond geometry (Å, °)

Cg1 and Cg2 are the centroids of the C1–C6 and N3–N4/C9–C12 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4⋯N4ⁱ	0.95	2.47	3.349 (6)	154
C10—H10⋯O2ⁱⁱ	0.95	2.55	3.283 (5)	134
C12—H12⋯O1ⁱⁱⁱ	0.95	2.49	3.439 (5)	174
O1—H1⋯N1	0.90 (8)	1.76 (8)	2.557 (4)	146 (7)
C13—H13A⋯Cg2^iv	0.98	2.86	3.740 (6)	149
C13—H13B⋯Cg1^v	0.98	2.71	3.592 (6)	150
Symmetry codes: (i) $[-x+{\script{3\over 2}}, y+{\script{1\over 2}}, z+1]$ ; (ii) $[x+{\script{1\over 2}}, -y+1, z-{\script{1\over 2}}]$ ; (iii) $[x-{\script{1\over 2}}, -y+1, z-{\script{1\over 2}}]$ ; (iv) $[-x+{\script{3\over 2}}, y, z+{\script{1\over 2}}]$ ; (v) $[-x+{\script{3\over 2}}, y, z-{\script{1\over 2}}]$ .

Figure 2
Crystal packing of the title compound showing the O—H⋯O and C—H⋯N hydrogen bonds. For clarity, another symmetrical ligand coordinated with metal center has been omitted. Symmetry codes: (ii) x + $[{1\over 2}]$ , −y + 1, z − $[{1\over 2}]$ ; (iii) x − $[{1\over 2}]$ , −y + 1, z − $[{1\over 2}]$ ; (vii) x + $[{1\over 2}]$ , −y + 1, z + $[{1\over 2}]$ ; (viii) x − $[{1\over 2}]$ , −y + 1, z + $[{1\over 2}]$ ; (ix) x, y, z − 1; (x) x, y, z + 1.

Figure 3
(a) Crystal packing of the title compound showing the C—H⋯π and π–π interactions. For clarity, the second ligand at each metal centre has been omitted. Symmetry codes: (iv) x, y − $[{1\over 2}]$ , z − $[{1\over 2}]$ ; (v) −x + $[{3\over 2}]$ , y, z − $[{1\over 2}]$ ; (vi) −x + $[{3\over 2}]$ , y, z + $[{1\over 2}]$ . (b) View down [100].

4. Database survey

A search of the Cambridge Structural Database (CSD, version 5.41, August 2020; Groom et al., 2016 ) for metal complexes involving the N′-[1-(pyrazin-2-yl)ethylidene]benzohydrazide ligand resulted in seven related metal complexes with exactly the same ligand. These are the already discussed isomorphous Mn, Co, Ni, Cu and Zn [M^II(L)₂] complexes (CCDC refcodes: CIZJED for M = Mn, CIZGOK for M = Co, CIZGAW for M = Ni (Yang, Zhang et al., 2020), COYVUK for M = Cu and CIZFUP for M = Zn) (Yang et al., 2019). In all of these complexes, the ligand L acts as a tridentate chelating ligand to generate a distorted octahedral structure with a close to planar ligand. Several complexes of related ligands have been found to be also isomorphous to the above series, crystallizing in the same Aba2 space group. These are a Co and a Zn complex bearing the ligand N′-[1-(pyrazin-2-yl)ethylidene]benzohydrazide (L⁴, with one less hydroxyl group on benzene) (YELKUY, YELWUK; Tai et al., 2008 ) as well as four metal complexes involving the ligand 2-hydroxy-N′-[1-(pyridin-2-yl)ethylidene]benzohydrazide (L⁵, substituted pyrazine group with pyridine group) with M = Cu²⁺, Ni²⁺, Zn²⁺ and Fe²⁺ [ADEYAK (Dang et al., 2006a ); XENFEC (Dang et al., 2006b ); HIGPOD (Barbazán et al., 2007 ); RADDOR (Zhang et al., 2010)].

There are also complexes of ligands L⁴ and L⁵ that are not isomorphous to the title complex: complex Cu₂(L⁴)₂Cl₂ is binuclear, where each Cu centre has two μ-chlorine ligands along with a tridentate coordinated L⁴ molecule, giving rise to a distorted square-pyramidal coordination environment. It belongs to the triclinic P $[\overline{1}]$ space group (YELXAR; Tai et al., 2008). The cobalt complex [Co(L⁵)₂(ClO₄)]·0.25(CH₃OH) (IGAZAS; Shit et al., 2009 ) has a nearly ideal octahedral structure in the monoclinic P2₁/n space group, and the ligands have N—N and N—O bite angles of 81.70 to 83.11°. Cu(L⁵)Br (HIGPIX; Barbazán et al., 2007) and Cu(L⁵)(NO₃) (YILYEY; You et al., 2018) have roughly square-planar coordination geometries. [Sb(L⁵)Cl₂]·H₂O (YILYEY; Abboud et al., 2007 ) has a square-pyramidal coordination geometry in the monoclinic P2₁/n space group. Cu₂(L⁵)₂Cl₂ (NICYOP; Mondal et al., 2013 ) is a binuclear complex and each Cu centre has a square-pyramidal coordination geometry. It is isomorphic to Cu₂(L⁴)₂Cl₂. A Zn complex, Zn(L¹)₂·H₂O (XIYNUP; Tai et al., 2008) with the ligand L¹ with one more methyl group on pyrazine crystallizes in the monoclinic P2₁/n space group. The planarity of the ligand is decreased compared to the title complex, and the Zn ion exhibits a distorted octahedral geometry. Also reported are five similar compounds featuring the ligands L² and L³ with the hydroxyl group in the meta and para positions of the benzene ring, respectively. They crystallize as DMF solvates [M(L²)₂]·2(DMF) (DMF = dimethylformamide; M = Ni, Cu and Zn; CIZHIF, CIZGUQ and CIZJAZ) and [Cu(L³)₂]·2(DMF) (M = Ni and Cu; CIZHUR and COYWEV) (Yang et al., 2019; Yang, Zhang et al., 2020) in the orthorhombic Pbcn space group. They also feature distorted octahedral structures and the planarity of the ligands is decreased compared to the title compound. All the complexes with the [M(Ligand)₂] core are distorted octahedral, and all metal centres have a mer geometry. All ligands L, L¹, L², L³, L⁴ and L⁵ are tridentate chelating.

5. Synthesis and crystallization

The title complex and ligand were synthesized according to literature procedures (Yang, Zhang et al., 2020; Yang et al., 2019). The complex was obtained by mixing a solution of the aroylhydrazone (0.02 mmol) in methanol (2 mL) and a solution of Cd(NO₃)₂·4H₂O (0.01 mmol) in water (2 mL). After two weeks of static volatilization in a test tube at room temperature, clear light-yellow block-shaped crystals of Cd(L)₂ were obtained (5.6 mg, yield 90%) (calculated based on metal ions), m.p. > 543 K. IR (KBr): ν (cm⁻¹) = 1594 s, 1534 s, 1518 s, 1489 s, 1458 s, 1401 w, 1349 s, 1299 s, 1248 m, 1225 m, 1198 m, 1162 m, 1147 s, 1106 w, 1072 s, 1042 m, 1029 m, 910 w, 850 w, 833 w, 786 w, 764 m, 701 m, 662 w, 565 w, 541 w, 492 w, 419 w, 406 w.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3. All C-bound H atoms were placed in calculated positions (Csp²—H = 0.95 Å and Csp³—H = 0.98 Å) and were included in the refinement in a riding-model approximation, with U_iso(H) set to 1.2U_eq(Csp²) and 1.5U_eq(Csp³). The O-bound H atom was located based on a difference-Fourier map and its position was freely refined. It was assigned U_iso(H) = 1.5U_eq(O).

Table 3
Experimental details

Crystal data
Chemical formula	[Cd(C₁₃H₁₁N₄O₂)₂]
M_r	622.91
Crystal system, space group	Orthorhombic, Aba2
Temperature (K)	108
a, b, c (Å)	12.6654 (1), 17.63940 (18), 10.88800 (11)
V (Å³)	2432.49 (4)
Z	4
Radiation type	Cu Kα
μ (mm⁻¹)	7.64
Crystal size (mm)	0.12 × 0.10 × 0.08

Data collection
Diffractometer	Rigaku Oxford Diffraction XtaLAB Synergy R, DW system, HyPix
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2020 $[Rigaku OD (2020). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ )
T_min, T_max	0.519, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	36223, 2475, 2458
R_int	0.038
(sin θ/λ)_max (Å⁻¹)	0.630

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.026, 0.075, 1.20
No. of reflections	2475
No. of parameters	182
No. of restraints	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.72, −0.99
Absolute structure	Flack x determined using 1131 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 ).
Absolute structure parameter	−0.012 (4)
Computer programs: CrysAlis PRO (Rigaku OD, 2020 $[Rigaku OD (2020). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ ), SHELXS and SHELXP (Sheldrick, 2008 ), SHELXL (Sheldrick, 2015 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 2051612

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989021000657/zl5004sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989021000657/zl5004Isup2.hkl

checkCIF report

Computing details top

Data collection: CrysAlis PRO (Rigaku OD, 2020); cell refinement: CrysAlis PRO (Rigaku OD, 2020); data reduction: CrysAlis PRO (Rigaku OD, 2020); program(s) used to solve structure: SHELXS (Sheldrick, 2008); program(s) used to refine structure: SHELXL (Sheldrick, 2015); molecular graphics: SHELXP (Sheldrick, 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

Bis{2-hydroxy-N'-[1-(pyrazin-2-yl)ethylidene]benzohydrazidato}cadmium(II) top

Crystal data top

[Cd(C₁₃H₁₁N₄O₂)₂]	D_x = 1.701 Mg m⁻³
M_r = 622.91	Cu Kα radiation, λ = 1.54178 Å
Orthorhombic, Aba2	Cell parameters from 31744 reflections
a = 12.6654 (1) Å	θ = 2.5–76.5°
b = 17.63940 (18) Å	µ = 7.64 mm⁻¹
c = 10.88800 (11) Å	T = 108 K
V = 2432.49 (4) Å³	Block, clear light yellow
Z = 4	0.12 × 0.10 × 0.08 mm
F(000) = 1256

Data collection top

Rigaku Oxford Diffraction XtaLAB Synergy R, DW system, HyPix diffractometer	2475 independent reflections
Radiation source: Rotating-anode X-ray tube	2458 reflections with I > 2σ(I)
Detector resolution: 10.0000 pixels mm^-1	R_int = 0.038
ω scans	θ_max = 76.2°, θ_min = 5.0°
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2020)	h = −14→15
T_min = 0.519, T_max = 1.000	k = −21→22
36223 measured reflections	l = −13→13

Refinement top

Refinement on F²	Hydrogen site location: mixed
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F² > 2σ(F²)] = 0.026	w = 1/[σ²(F_o²) + (0.0473P)² + 1.8799P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.075	(Δ/σ)_max < 0.001
S = 1.20	Δρ_max = 0.72 e Å⁻³
2475 reflections	Δρ_min = −0.99 e Å⁻³
182 parameters	Extinction correction: SHELXL (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
1 restraint	Extinction coefficient: 0.00067 (9)
Primary atom site location: structure-invariant direct methods	Absolute structure: Flack x determined using 1131 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013).
Secondary atom site location: difference Fourier map	Absolute structure parameter: −0.012 (4)

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
C1	0.6224 (3)	0.6694 (2)	0.9539 (4)	0.0255 (8)
C2	0.7242 (3)	0.6887 (2)	0.9964 (4)	0.0322 (9)
C3	0.7340 (5)	0.7364 (3)	1.0986 (5)	0.0422 (13)
H3	0.802253	0.749817	1.127537	0.051*
C4	0.6462 (5)	0.7642 (2)	1.1578 (4)	0.0439 (12)
H4	0.654329	0.795728	1.227906	0.053*
C5	0.5452 (5)	0.7465 (2)	1.1153 (4)	0.0399 (11)
H5	0.484590	0.766539	1.155165	0.048*
C6	0.5341 (4)	0.6995 (2)	1.0149 (4)	0.0316 (8)
H6	0.465320	0.687281	0.986326	0.038*
C7	0.6043 (3)	0.61456 (19)	0.8526 (3)	0.0220 (7)
C8	0.7448 (4)	0.5100 (2)	0.6398 (5)	0.0240 (9)
C9	0.7096 (3)	0.4582 (2)	0.5418 (4)	0.0247 (8)
C10	0.7783 (3)	0.4270 (2)	0.4540 (4)	0.0319 (9)
H10	0.851195	0.439329	0.458193	0.038*
C11	0.6425 (4)	0.3646 (2)	0.3636 (4)	0.0365 (10)
H11	0.616344	0.331030	0.302482	0.044*
C12	0.5728 (3)	0.3950 (2)	0.4482 (4)	0.0282 (8)
H12	0.500036	0.382194	0.443503	0.034*
C13	0.8597 (3)	0.5252 (3)	0.6647 (5)	0.0388 (11)
H13A	0.879522	0.502577	0.743598	0.058*
H13B	0.871828	0.580037	0.667603	0.058*
H13C	0.902554	0.502866	0.599080	0.058*
Cd1	0.500000	0.500000	0.68642 (13)	0.01811 (16)
N1	0.6931 (3)	0.58932 (17)	0.7964 (3)	0.0236 (6)
N2	0.6699 (2)	0.54015 (16)	0.7035 (3)	0.0211 (6)
N3	0.6056 (2)	0.44157 (17)	0.5356 (3)	0.0227 (6)
N4	0.7454 (4)	0.3809 (2)	0.3652 (4)	0.0398 (9)
O1	0.8136 (3)	0.66287 (19)	0.9425 (3)	0.0393 (7)
H1	0.796 (6)	0.631 (4)	0.880 (7)	0.059*
O2	0.5115 (2)	0.5951 (2)	0.8272 (4)	0.0271 (8)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.031 (2)	0.0204 (17)	0.0249 (18)	−0.0051 (13)	−0.0068 (15)	0.0044 (15)
C2	0.039 (2)	0.0289 (18)	0.0291 (19)	−0.0115 (17)	−0.0106 (18)	0.0059 (16)
C3	0.062 (3)	0.0319 (18)	0.032 (2)	−0.019 (2)	−0.020 (2)	0.004 (2)
C4	0.076 (4)	0.029 (2)	0.026 (2)	−0.015 (2)	−0.010 (2)	−0.0013 (17)
C5	0.064 (4)	0.025 (2)	0.030 (2)	−0.010 (2)	0.000 (2)	−0.0017 (18)
C6	0.041 (2)	0.0249 (19)	0.028 (2)	−0.0056 (19)	−0.003 (2)	−0.0002 (16)
C7	0.0221 (17)	0.0225 (16)	0.0214 (16)	−0.0039 (13)	−0.0030 (14)	0.0033 (14)
C8	0.014 (2)	0.0278 (18)	0.031 (2)	0.0012 (15)	0.0002 (18)	0.0100 (16)
C9	0.0225 (19)	0.0237 (16)	0.0279 (18)	0.0048 (13)	0.0074 (15)	0.0079 (14)
C10	0.030 (2)	0.0273 (18)	0.038 (2)	0.0084 (15)	0.0141 (17)	0.0076 (17)
C11	0.055 (3)	0.0276 (19)	0.027 (2)	0.0030 (19)	0.010 (2)	−0.0020 (16)
C12	0.033 (2)	0.0258 (17)	0.0261 (17)	−0.0022 (15)	0.0027 (16)	0.0024 (16)
C13	0.0136 (18)	0.045 (2)	0.058 (3)	−0.0028 (18)	0.0024 (19)	0.010 (3)
Cd1	0.0110 (2)	0.0243 (2)	0.0190 (2)	−0.00150 (9)	0.000	0.000
N1	0.0208 (15)	0.0243 (15)	0.0256 (15)	−0.0053 (12)	−0.0046 (12)	0.0016 (12)
N2	0.0155 (14)	0.0234 (12)	0.0243 (16)	−0.0022 (11)	0.0008 (12)	0.0048 (12)
N3	0.0207 (15)	0.0243 (14)	0.0230 (13)	0.0016 (11)	0.0039 (12)	0.0029 (12)
N4	0.049 (2)	0.0302 (17)	0.040 (2)	0.0100 (17)	0.0206 (18)	0.0047 (16)
O1	0.0320 (17)	0.0460 (17)	0.0399 (16)	−0.0136 (13)	−0.0121 (14)	0.0016 (15)
O2	0.0208 (14)	0.0311 (17)	0.0293 (18)	−0.0023 (10)	−0.0010 (11)	−0.0091 (15)

Geometric parameters (Å, º) top

C1—C6	1.405 (7)	C10—N4	1.330 (7)
C1—C2	1.412 (6)	C10—H10	0.9500
C1—C7	1.485 (5)	C11—N4	1.335 (7)
C2—O1	1.354 (6)	C11—C12	1.385 (6)
C2—C3	1.401 (7)	C11—H11	0.9500
C3—C4	1.375 (8)	C12—N3	1.324 (5)
C3—H3	0.9500	C12—H12	0.9500
C4—C5	1.396 (8)	C13—H13A	0.9800
C4—H4	0.9500	C13—H13B	0.9800
C5—C6	1.378 (6)	C13—H13C	0.9800
C5—H5	0.9500	Cd1—N2	2.273 (3)
C6—H6	0.9500	Cd1—N2ⁱ	2.273 (3)
C7—O2	1.255 (5)	Cd1—O2	2.277 (4)
C7—N1	1.355 (5)	Cd1—O2ⁱ	2.277 (4)
C8—N2	1.289 (6)	Cd1—N3ⁱ	2.356 (3)
C8—C9	1.475 (7)	Cd1—N3	2.356 (3)
C8—C13	1.504 (7)	N1—N2	1.365 (4)
C9—N3	1.351 (5)	O1—H1	0.90 (8)
C9—C10	1.405 (5)

C6—C1—C2	118.7 (4)	N3—C12—H12	119.4
C6—C1—C7	118.4 (4)	C11—C12—H12	119.4
C2—C1—C7	122.8 (4)	C8—C13—H13A	109.5
O1—C2—C3	118.2 (4)	C8—C13—H13B	109.5
O1—C2—C1	122.7 (4)	H13A—C13—H13B	109.5
C3—C2—C1	119.1 (5)	C8—C13—H13C	109.5
C4—C3—C2	121.0 (5)	H13A—C13—H13C	109.5
C4—C3—H3	119.5	H13B—C13—H13C	109.5
C2—C3—H3	119.5	N2—Cd1—N2ⁱ	170.63 (17)
C3—C4—C5	120.4 (4)	N2—Cd1—O2	69.83 (11)
C3—C4—H4	119.8	N2ⁱ—Cd1—O2	103.58 (11)
C5—C4—H4	119.8	N2—Cd1—O2ⁱ	103.58 (11)
C6—C5—C4	119.4 (5)	N2ⁱ—Cd1—O2ⁱ	69.83 (11)
C6—C5—H5	120.3	O2—Cd1—O2ⁱ	95.4 (2)
C4—C5—H5	120.3	N2—Cd1—N3ⁱ	117.27 (11)
C5—C6—C1	121.4 (5)	N2ⁱ—Cd1—N3ⁱ	69.86 (11)
C5—C6—H6	119.3	O2—Cd1—N3ⁱ	100.55 (13)
C1—C6—H6	119.3	O2ⁱ—Cd1—N3ⁱ	139.07 (10)
O2—C7—N1	126.0 (3)	N2—Cd1—N3	69.86 (11)
O2—C7—C1	119.0 (4)	N2ⁱ—Cd1—N3	117.27 (11)
N1—C7—C1	114.9 (3)	O2—Cd1—N3	139.07 (10)
N2—C8—C9	115.0 (4)	O2ⁱ—Cd1—N3	100.55 (13)
N2—C8—C13	122.8 (5)	N3ⁱ—Cd1—N3	91.59 (16)
C9—C8—C13	122.2 (4)	C7—N1—N2	111.4 (3)
N3—C9—C10	119.0 (4)	C8—N2—N1	120.2 (3)
N3—C9—C8	117.7 (4)	C8—N2—Cd1	121.6 (3)
C10—C9—C8	123.2 (4)	N1—N2—Cd1	117.5 (2)
N4—C10—C9	122.7 (4)	C12—N3—C9	118.5 (3)
N4—C10—H10	118.6	C12—N3—Cd1	126.5 (3)
C9—C10—H10	118.6	C9—N3—Cd1	115.1 (3)
N4—C11—C12	122.1 (4)	C10—N4—C11	116.5 (4)
N4—C11—H11	119.0	C2—O1—H1	109 (5)
C12—C11—H11	119.0	C7—O2—Cd1	114.1 (3)
N3—C12—C11	121.2 (4)

C6—C1—C2—O1	−179.3 (4)	C8—C9—C10—N4	−179.3 (4)
C7—C1—C2—O1	4.8 (6)	N4—C11—C12—N3	−0.4 (6)
C6—C1—C2—C3	0.8 (6)	O2—C7—N1—N2	1.7 (5)
C7—C1—C2—C3	−175.2 (4)	C1—C7—N1—N2	−179.1 (3)
O1—C2—C3—C4	−179.7 (4)	C9—C8—N2—N1	−179.8 (3)
C1—C2—C3—C4	0.2 (6)	C13—C8—N2—N1	1.4 (6)
C2—C3—C4—C5	−1.3 (7)	C9—C8—N2—Cd1	10.1 (5)
C3—C4—C5—C6	1.3 (6)	C13—C8—N2—Cd1	−168.8 (3)
C4—C5—C6—C1	−0.3 (6)	C7—N1—N2—C8	−179.7 (3)
C2—C1—C6—C5	−0.7 (6)	C7—N1—N2—Cd1	−9.2 (4)
C7—C1—C6—C5	175.4 (4)	C11—C12—N3—C9	−1.0 (6)
C6—C1—C7—O2	−2.2 (5)	C11—C12—N3—Cd1	179.4 (3)
C2—C1—C7—O2	173.7 (4)	C10—C9—N3—C12	1.5 (5)
C6—C1—C7—N1	178.6 (3)	C8—C9—N3—C12	−179.9 (3)
C2—C1—C7—N1	−5.5 (5)	C10—C9—N3—Cd1	−178.8 (3)
N2—C8—C9—N3	−6.2 (5)	C8—C9—N3—Cd1	−0.2 (4)
C13—C8—C9—N3	172.6 (4)	C9—C10—N4—C11	−0.6 (6)
N2—C8—C9—C10	172.3 (4)	C12—C11—N4—C10	1.2 (6)
C13—C8—C9—C10	−8.8 (6)	N1—C7—O2—Cd1	6.4 (5)
N3—C9—C10—N4	−0.8 (6)	C1—C7—O2—Cd1	−172.7 (3)

Symmetry code: (i) −x+1, −y+1, z.

Hydrogen-bond geometry (Å, º) top

Cg1 and Cg2 are the centroids of the C1–C6 and N3–N4/C9–C12 rings, respectively.

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···N4ⁱⁱ	0.95	2.47	3.349 (6)	154
C10—H10···O2ⁱⁱⁱ	0.95	2.55	3.283 (5)	134
C12—H12···O1^iv	0.95	2.49	3.439 (5)	174
O1—H1···N1	0.90 (8)	1.76 (8)	2.557 (4)	146 (7)
C13—H13A···Cg2^v	0.98	2.86	3.740 (6)	149
C13—H13B···Cg1^vi	0.98	2.71	3.592 (6)	150

Symmetry codes: (ii) −x+3/2, y+1/2, z+1; (iii) x+1/2, −y+1, z−1/2; (iv) x−1/2, −y+1, z−1/2; (v) −x+3/2, y, z+1/2; (vi) −x+3/2, y, z−1/2.

Comparative analysis of ion radius and the bond lengths and bond angles of coordination polyhedra (Å, °) top

	Mn²⁺	Co²⁺	Ni²⁺	Cu²⁺	Zn²⁺	Cd²⁺
Ion radius	0.83	0.745	0.69	0.73	0.74	0.95
M—N	2.283	2.151	2.114	2.192	2.215	2.356
M—N(mid)	2.193	2.050	1.994	1.979	2.074	2.273
M—O	2.148	2.102	2.097	2.130	2.125	2.278
N(mid)—M—N(mid)	174.46	172.30	173.86	173.64	173.97	170.63
N—M—O (within the same ligand)	142.08	148.53	153.95	151.98	148.84	139.07
O—M—O	99.76	102.86	95.26	97.43	98.87	95.39
N(mid)—M—O (within different ligands)	104.25	99.33	98.33	98.79	100.49	103.58
CSD refcode	CIZJED^a	CIZGOK^b	CIZGAW^c	COYVUK^d	CIZFUP^e	2051612^f

Notes: (a) Yang (2019); (b) Yang (2019); (c) Yang, Zhang et al. (2020); (d) Yang, Zhang et al. (2019); (e) Yang (2019); (f) reference? (year?).

Acknowledgements

The authors thank Guangzhou University and Zi-Zhou Wang for recording the X-ray crystallographic data for the crystals.

Funding information

Funding for this research was provided by: the National Natural Science Foundation of China (grant No. 41701349); GDAS' Project of Science and Technology Development (grant No. 2020GDASYL-20200103015); Nanyue Talent Fund (grant No. GDIMYET20180205).

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