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• 0   Introduction

  Organic-inorganic hybrid perovskite functional materials are a new type of crystal materials, in which the inorganic perovskite layer works as a skeleton and the organic molecular functional groups are connected to the inorganic perovskite layer through intermole-cular hydrogen bonds^[1-4]. The organic and inorganic components form a long-range ordered single crystal through the alternating stacking, in which the inorganic parts supply the hybrid structure with thermal stability and hardness as well as optical, electrical and magnetic properties^[5-8], and the organic materials offer the hybrids with softness, flexibility, and highly efficient luminescence^[9] and structural diversity^[10-13]. Over the past decade, organic-inorganic hybrid compounds have exhibited good development and application in the solar semiconductor batteries^[14], light-emitting diodes^[15], ferroelectric properties^[9] and other fields^[16-18].

  In organic-inorganic hybrid materials, the organic ligands not only play a role as the template^[19-21], but also the key to determining the properties of inorganic components^[22-24], such as in photoelectric field, the organic-inorganic hybrids constructed with organic amines and lead halide have shown good fluorescence performance^[25-27]. This is because the hybrid perovskite is a type of semiconductor quantum well structure, typi-cally with small band gap inorganic sheets (carrier) alternating with larger band gap organic layer^[28-30]. For example, the new reported 2D lead bromide perovskite (DMEN)PbBr₄ (DMEN=2-(dimethylamino)ethylamine) incorporating a bifunctional ammonium dication as template was found to have white-light, broad-band emission in the visible range^[25].

  In this article, an aromatic heterocycle organic template benzothiazole (btz) was selected to react with the main and transition metal halides MCl₂ (M=Pb²⁺, Cd²⁺, Co²⁺) in the concentrated HCl acid, and three inorganic-organic hybrid compounds: (btzH)[PbCl₃] (1), (btzH)₂[CdCl₄]·2H₂O (2) and (btzH)₂[CoCl₄]·2H₂O (3) were obtained. Herein, we reported the syntheses, characterizations and fluorescent properties of compounds 1, 2 and 3.

  1   Experimental

  1.1   Instrument and materials

  The starting materials PbCl₂, CdCl₂, CoCl₂·6H₂O, benzothiazole and the concentrated hydrochloric acid are commercially available and were used as received. FT-IR spectra were recorded using KBr pellets in the range of 4 000~400 cm^-1 on an ALPHA spectrometer. UV-Vis spectra were collected on a UV-Vis Curry 60 spectrophotometer. Powder X-ray diffraction (PXRD) patterns were collected on a glass sheet in the 2θ range of 5°~50° with a scan rate of 2°·min^-1 on a D8 ADVANCE diffractometer equipped with Cu Kα radiation (λ=0.154 18 nm, U=40 kV, I=40 mA) at 298 K. Thermo-gravimetry (TG) were carried out between 30 and 800 ℃ at a scan rate of 10 ℃·min^-1 in a N₂ atmosphere on a TGA Mettler-Toledo Gmbh thermo-gravimetric analyzer. Micro-analysis service was recorded on a Heraeus CHN-O-Rapid. Fluorescent spectra were carried on a Hitachi F-4600 spectrophotometer.

  1.2   Syntheses of compounds 1~3

  1.2.1   Synthesis of (btzH)[(PbCl₃)] (1)

  To a solution of PbCl₂ (0.20 g, 0.72 mmol) in concentrated HCl (18 mL, 47%) was added a solution of benzothiazole (0.20 g, 1.52 mmol) in concentrated HCl (18 mL, 47%). The mixed solution was heated to 80 ℃ and kept stirring for half hour. Cooling down the reaction to room temperature gave colorless needle crystals. Yield: 144 mg, 44% (based on PbI₂). Anal. Calcd. for C₇H₆NSCl₃Pb(%): C 18.69, H 1.34, N 3.11. Found(%): C 18.36, H 1.69, N 3.33. IR (KBr, cm^-1): 3 740(w), 3 440(s), 3 094(m), 3 046(w), 2 948(m), 2 865(m), 2 802(m), 2 742(m), 2 646(m), 1 852(m), 1 716(m), 1 596(m), 1 580(m), 1 458(m), 1 428(m), 1 271(m), 1 241(m), 952(s), 888(s), 800(w), 755(w), 721(m), 686(m), 554(w), 503(w), 423(w).

  1.2.2   Synthesis of (btzH)₂[CdCl₄]·2H₂O (2)

  According to the similar procedure to synthesis of compound 1 based on CdCl₂ (0.359 g, 1.96 mmol) and benzothiazole (0.396 g, 2.93 mmol) in concen-trated HCl (18 mL, 47%) gave the light gray prismatic crystals of 2. Yield: 124 mg, 72%. Anal. Calcd. for C₁₄H₁₆N₂O₂S₂Cl₄Cd(%): C 29.89, H 2.87, N 4.98. Found(%): C 29.64, H 2.43, N 4.72. IR (KBr, cm^-1): 3 424(s), 3 102(m), 3 052(w), 2 963(m), 2 895(m), 2 813(m), 2 745(m), 2 359(s), 1 811(w), 1 603(w), 1 579(s), 1 461(s), 1 429(m), 1 244(s), 825(s), 761(w), 722(s), 566(w), 504(w), 413(w).

  1.2.3   Synthesis of (btzH)₂[CoCl₄]·2H₂O (3)

  According to the similar procedures to synthesis of compound 1 based on CoCl₂·6H₂O (0.50 g, 1.83 mmol) and benzothiazole (0.49 g, 3.63 mmol) in concentrated HCl (18 mL, 47%) gave the deep blue block crystals of 3. Yield: 400 mg, 43%. Anal. Calcd. for C₁₄H₁₆N₂O₂S₂Cl₄Co(%): C 33.03, H 3.17, N 5.50%. Found(%): C 33.47, H 3.31, N 5.13. IR (KBr, cm^-1): 3 738(w), 3 411(w), 3 076(w), 3 029(m), 2 946(m), 2 878(w), 2 809(w), 2 744(m), 2 658(m), 2 365(s), 1 833(w), 1 702(s), 1 626(s), 1 586(s), 1 460(m), 1 413(m), 1 294(s), 1 266(s), 1 244(s), 1 168(s), 1 046(s), 912(m), 822(s), 757(w), 721(m), 685(s), 538(w), 497(w), 418(s).

  1.3   X-ray crystallography

  In the crystallographic data collection of compounds 1~3, standard procedures were used for mounting the crystals on a Bruker SMART CCD diffractometer with graphite-monochromated Mo Kα radiation (λ=0.071 073 nm). The structures were solved by the direct methods routines in the SHELXS program and refined on F² in SHELXL^[31]. Non-hydrogen atoms were first refined isotropically followed by anisotropic refinement by full matrix least-squares calculations based on F² using SHELXL-97^[32]. All hydrogen atoms except that in water molecules were placed in idealized positions and treated as riding atoms. Hydrogen atoms in water molecules were first located in the difference Fourier maps then positioned geometrically and allowed to ride on their respective parent atoms. Details of the data collection and refinement are given in Table 1.

  Table 1.  Crystal data and structure refinement for compounds 1~3

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  Compound	1	2	3
  Formula	C7H6NSCl3Pb	C14H16N2O2S2Cl4Cd	C14H16N2O2S2Cl4Co
  Formula weight	449.75	562.64	509.16
  Crystal system	Triclinic	Triclinic	Monoclinic
  Space group	P1	P1	C2/c
  a/nm	0.425 31(16)	0.740 78(5)	1.159 2(5)
  b/nm	1.146 2(4)	0.772 47(5)	1.007 7(4)
  c/nm	1.288 7(5)	1.890 52(11)	1.798 5(7)
  α/(°)	64.830(7)	101.000 0(10)	90
  β/(°)	82.343(8)	96.678 0(10)	104.142(4)
  γ/(°)	84.459(8)	94.541 0(10)	90
  V/nm3	0.561 0(4)	1.049 02(12)	2.037 2(14)
  Z	2	2	4
  Dc/(g·cm-3)	2.653	1.781	1.660
  μ/mm-1	15.833	1.760	1.583
  F(000)	408	556	1 028
  θmax	25.00	36.57	27.88
  Total reflection	3 382	12 228	7 893
  Unique reflection	1911(Rint=0.0418)	8 205 (Rint=0.013 5)	2 248 (Rint=0.016 6)
  Completeness /%	97.0	99.3	98.6
  No. of variables	123	250	127
  GOF	1.090	1.072	1.041
  R1, wR2[I>2σ(I)]	0.033 3,0.086 7	0.037 6,0.084 4	0.022 9,0.058 5
  R1, wR2(all data)	0.034 0,0.087 5	0.048 7,0.092 7	0.027 5,0.061 1

  CCDC: 1571943, 1; 1571944, 2; 1571945, 3.

  2   Results and discussion

  2.1   Synthesis and characterization

  Compounds 1~3 were obtained by reactions of MX2 (M=Pb, Cd, Co) and btz with molar ratio of 1:2 in concentrated HCl solution. After heating and evaporation, the reactions led to the formation of colorless needle crystals of 1, light gray plate crystals of 2 and deep blue block crystals of 3 in moderate yields, respectively. Crystals were then filtered and washed with methanol and acetonitrile and dried in vacuo. The phase purities of a mass of 1~3 were verified using the powder X-ray diffraction (PXRD) patterns which matched very well with the simulated ones in terms of the single-crystal X-ray data as shown in Fig.S1.

  The TGA curves for compounds 1~3 were provided in Fig.S2. Complex 1 occurrs two weight loss steps between 180 and 750 ℃. The first weight loss, observed between 180 and 200 ℃, is ascribed to the decomposition of the btz ligand (30% loss). The second weight loss, occurring between 550 to 750 ℃, is attributed to the loss of halide anions or sublimation of newly formed PbCl₂ compound. While complex 2 is not stable, it firstly decomposes at 100 ℃ due to the loss of solvated water (6%). The second and third weight loss between 150 to 280 ℃ are ascribed to the loss of btz ligand (49%). The last weight loss began at 560 ℃ is corresponded to the loss of CdCl₂, which is consistent with its melting point at 568 ℃. The residue (1.5%) may belong to the high boiling impurities. The weight loss of compound 3 is somewhat familiar to complex 2, but the weight loss curve is not as clear as that in complex 2.

  In FT-IR spectra of compounds 1~3, the strong absorption bands at 1 580 and 1 596 cm^-1 for 1, 1 579 and 1 603 cm^-1 for 2, 1 586 and 1 626 cm^-1 for 3 are ascribed to the C=C and C=N stretching vibrations of aromatic rings. The middle absorptions at 3 094, 3 046 cm^-1 for 1, at 3 102, 3 052 cm^-1 for 2 and at 3 076, 3 029 cm^-1 for 3 are corresponded to the vibration of C-H bond in benzothiazole ring. The C-S stretching vibration in compounds 1~3 is about at 722 cm^-1. Due to the formation of hydrogen bond, the vibration of N-H in benzothiazole ring becomes very weak. The broad and strong bands at about 3 400 cm^-1 in compounds 2 and 3 indicate the presence of co-crystallized water molecules.

  2.2   Structure description

  Complex 1 crystallizes in the triclinic system with a space group of P1 and the asymmetric unit contains one (btzH)⁺ cation, one [PbCl₃]^- anion (Fig. 1a). Based on the connectivity of the chlorine atoms to the Pb atoms, there are three types of chlorine atoms: the terminal Cl(3), the double bridging Cl(1), and the triple-bridging Cl(2). The inorganic part of 1 is composed of [PbCl₆] octahedrons by sharing three edges along a axis direction to give 1D double-strand (Fig. 1b). The protonated (btzH)⁺ cations are connected to the double-strands by intermolecular hydrogen bond N-H…Cl along c axis direction (Table 4). In [PbCl₆] octahedron, the Pb-Cl bond lengths vary from 0.275 6(2) to 0.304 3(2) nm, and the maximum angle of Cl-Pb-Cl is at 174.53(6)°, revealing the octahedron was seriously distorted (Table 2).

  图1 (a) Asymmetric unit of 1 drawn with 30% thermal ellipsoids; (b) Protonated (btzH)⁺ cations connected to 1D double-strands by N-H…Cl hydrogen bonds Figure1. (a) Asymmetric unit of 1 drawn with 30% thermal ellipsoids; (b) Protonated (btzH)⁺ cations connected to 1D double-strands by N-H…Cl hydrogen bonds

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  Table 2.  Selected bond lengths (nm) and angles (°) for 1

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  Pb(1)-Cl(1)	0.279 9(2)	Pb(1)-Cl(2)	0.304 3(2)	Pb(1)-Cl(3)	0.275 6(2)
  Pb(1)-Сl(2)ⅰ	0.289 1(3)	Pb(1)-Cl(1)ⅱ	0.293 7(2)	Pb(1)-Cl(2)ⅲ	0.297 2(3)
  Cl(2)ⅰ-Pb(1)-Cl(2)	81.50(7)	Cl(1)ⅱ-Pb(1)-Cl(2)ⅲ	83.43(7)	Cl(2)ⅲ-Pb(1)-Cl(2)	83.76(7)
  Cl(3)-Pb(1)-Cl(1)	86.63(7)	Cl(1)-Pb(1)-Cl(2)ⅰ	87.38(7)	Cl(1)-Pb(1)-Cl(2)	90.90(7)
  Cl(3)-Pb(1)-Cl(1)ⅱ	92.54(7)	Cl(1)-Pb(1)-Cl(2)ⅱ	92.90(7)	Cl(2)ⅰ-Pb(1)-Cl(2)ⅲ	92.99(7)
  Cl(3)-Pb(1)-Cl(2)ⅰ	93.16(7)	Cl(1)-Pb(1)-Cl(1)ⅱ	95.69(7)	Cl(3)-Pb(1)-Cl(2)ⅲ	98.79(6)
  Cl(1)-Pb(1)-Cl(2)ⅲ	174.53(6)	Cl(3)-Pb(1)-Cl(2)	174.23(6)
  Symmetry codes: ⅰ -x, -y+3, -z-1; ⅱ x+1, y, z; ⅲ -x+1, -y+3, -z-1.

  Table 4.  Hydrogen bonds for compounds 1, 2 and 3

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  D-H…A	d(D-H)/nm	d(H…A)/nm	d(D…A)/nm	∠DHA/(°)
  1
  N(1)-H(1)…Cl(3)ⅰ	0.076	0.245	0.310	145
  2
  O(2)-H(W1)…Cl(3)ⅱ	Pb079(5)	Pb242(5)	0.3l5 9(3)	l55(5)
  N(1)-H(1A)…O(2)	0.082(3)	0.190(3)	0.270 0(3)	168(3)
  N(2)-H(2)…O(1)ⅲ	0.091(3)	0.180(3)	0.271 0(4)	176(3)
  O(2)-H(W2)…Cl(4)ⅳ	0.085(5)	0.241(5)	0.319 9(3)	156(5)
  O(1)-H(W3)…Cl(3)	0.088(8)	0.248(8)	0.330 5(4)	157(6)
  O(1)-H(W4)…Cl(2)ⅱ	P0.074(7)	0.280(6)	0.336 1(4)	135(6)
  3
  N(1)-H(1)…O(1)	0.083 0	0.194 3	0.275 6	166.33
  O(1)-H(1)…Cl(2)ⅴ	0.076 7	0.252 7	0.320 5	148.32
  O(1)-H(2W)…Cl(1)	0.080 0	0.243 3	0.321 3	165.47
  Symmetry codes: ⅰ -x, 2-y, -z for 1; ⅱ x, -1+y, z; ⅲ 1-x, 1-y, 1-z; ⅳ 1+x, -1+y, z for 2; ⅴ 1/2+x, 1/2+y, z for 3.

  Complex 2 crystallizes in the triclinic system with a space group of P1 and the asymmetric unit contains two protonated (btzH)⁺ cations, one [CdCl₄]^2- anion and two solvated water molecules (Fig. 2a). The coordination geometry around the Cd(Ⅱ) atom adopts a slightly distorted tetrahedron with the Cd-Cl bond lengths varying from 0.244 34(7) to 0.245 39(6) nm, and the angles varying from 105.89(4)° to 114.25(3)°(Table 3). In the whole structure, two water molecules act as μ₂-connecting nods linking the [CdCl₄] tetrahedrons by two pairs of hydrogen bonds(O_water-H…Cl, Table 4) along a and b directions to form a 2D layer (Fig. 2b). At the same time, the cationic (btzH)⁺ suspends on the 2D layer using the other type of hydrogen bond(N-H…O_water) along c direction, (Table 4, Fig. 3c).

  图2 (a) Asymmetric unit of 2 drawn with 30% thermal ellipsoids; (b) [CdCl₄] tetrahedrons connected with water molecules using hydrogen bonds O-H…Cl along a and b directions; (c) (btzH)⁺ cations connected to the 2D layers using hydrogen bond N-H…O along c direction Figure2. (a) Asymmetric unit of 2 drawn with 30% thermal ellipsoids; (b) [CdCl₄] tetrahedrons connected with water molecules using hydrogen bonds O-H…Cl along a and b directions; (c) (btzH)⁺ cations connected to the 2D layers using hydrogen bond N-H…O along c direction

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  Table 3.  Selected bond lengths (nm) and angles (°) for 2 and 3

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  2
  Cd(1)-Cl(1)	0.244 34(7)	Cd(1)-Cl(2)	0.245 07(7)	Cd(1)-Cl(3)	Pb247 53(7)
  Cd(1)-Cl(4)	0.245 39(6)
  Cl(1)-Cd(1)-Cl(2)	114.25(3)	Cl(1)-Cd(1)-Cl(4)	108.26(3)	Cl(2)-Cd(1)-Cl(4)	110.78(3)
  Cl(1)-Cd(1)-Cl(3)	105.28(3)	Cl(2)-Cd(1)-Cl(3)	108.77(3)	Cl(4)-Cd(1)-Cl(3)	109.29(3)
  3
  Co(1)-Cl(1)	0.227 75(7)	Co(1)-Cl(2)	0.226 04(7)
  Cl(2)-Co(1)-Cl(2)ⅰ	111.19(4)	Cl(2)-Co(1)-Cl(1)	109.91(3)	Cl(2)ⅰ-Co(1)-Cl(1)	108.87(3)
  Cl(1)-Co(1)-Cl(1)ⅰ	108.03(4)
  Symmetry codes: ⅰ -x+1, y, -z+1/2 for complex 3.

  图3 (a) Asymmetric unit of 3 drawn with 30% thermal ellipsoids; (b) [CoCl₄] tetrahedrons connected by water molecules using hydrogen bonds O-H…Cl along a and b directions to form 2D layer; (c) (btzH)⁺ cations suspended on the 2D layers using hydrogen bond N-H…O_water along c direction Figure3. (a) Asymmetric unit of 3 drawn with 30% thermal ellipsoids; (b) [CoCl₄] tetrahedrons connected by water molecules using hydrogen bonds O-H…Cl along a and b directions to form 2D layer; (c) (btzH)⁺ cations suspended on the 2D layers using hydrogen bond N-H…O_water along c direction

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  Complex 3 crystallizes in the monoclinic system with a space group of C2/c and the asymmetric unit contains one protonated (btzH)⁺ cations, half [CoCl₄]^2- anion and one solvated water molecules (Fig. 3a). As shown in Fig. 3b and 3c, the structure of compound 3 is very similar to that of complex 2, so the structure of compound 3 is not described in detail herein. To be noted, the Co-Cl bond lengths in complex 3 are shorter than the Cd-Cl bond lengths in complex 2 due to that the radius of Co²⁺ ion is smaller than that of Cd²⁺ (Table 3). But the average bond angle Cl-Co-Cl at 109.5° in tetrahedron [CoCl₄] is similar to that of Cl-Cd-Cl (109.44°) in [CdCl₄].

  2.3   Absorption and fluorescence

  As shown in Fig. 4, compounds 1~3 in the solid states showed the similar absorption wavelengths in the range of 200~300 nm. The absorption peaks at 260 and 300 nm both come from the π…π^* transition of btz ring which can be proved by the absorptions of free ligand btz in solution (Fig. 4, inset). Due to the strong absorption of organic part, the absorptions originated from inorganic parts [PbCl₆] in complex 1 and [CdCl₄] in complex 2 are not obvious. In 3, the tetrahedrally coordinated Co²⁺ ions show the obvious absorption band in the range of 600~750 nm which belong to the spin allowed d-d transitions of Co²⁺ ion. While in complex 2, the d-d transition is not found due to that the d orbits in Cd²⁺ ions are full.

  图4 UV-Vis spectra of compounds 1~3 in solid states Figure4. UV-Vis spectra of compounds 1~3 in solid states

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  The solid fluorescent spectra of compounds 1~3 were showed in Fig. 5. At the excitation wavelength of 320 nm, all compounds show the similar emissions at 393 nm. In order to clarify the fluorescence source of the compounds 1~3, we carried out the fluorescence test of free ligand btz in solution, but it was found that there was no fluorescence response in dichloromethane solution. According to the literatures, we know that benzothiazole has a large π-conjugated system, and many benzothiazole derivatives have exhibited good fluorescence properties^[33-35]. According to the above analysis, we still believe that the fluore-scence emission peaks of compounds 1~3 are derived from the π…π transition of the btz ring. This is because the benzothiazole is protonated and hydrogen-bonded to the chloride atoms in polyhedron, and its fluorescence performance turns from original quen-ching into enhancement.

  图5 Emission spectra of compounds 1~3 in the solid states Figure5. Emission spectra of compounds 1~3 in the solid states

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  3   Conclusions

  Three organic-inorganic hybrid compounds were isolated by reactions of btz with MCl₂ (M=Pb²⁺, Cd²⁺, Co²⁺) in concentrated HCl aqueous solution. The single X-ray diffraction investigation demonstrated that the inorganic part in complex 1 is a 1D two stranded chain, and those in compounds 2 and 3 are the [MCl₄] (M=Cd, Co) tetrahedrons, which are both linked with the solvated water molecules by the hydrogen bond. Fluorescent spectra reveal that compounds 1~3 show the similar emission peaks at 393 nm, which are ascribed to the π…π transition of the protonated btz ring.

  Supporting information is available at http://www.wjhxxb.cn

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  Figure 1  (a) Asymmetric unit of 1 drawn with 30% thermal ellipsoids; (b) Protonated (btzH)⁺ cations connected to 1D double-strands by N-H…Cl hydrogen bonds

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  Figure 2  (a) Asymmetric unit of 2 drawn with 30% thermal ellipsoids; (b) [CdCl₄] tetrahedrons connected with water molecules using hydrogen bonds O-H…Cl along a and b directions; (c) (btzH)⁺ cations connected to the 2D layers using hydrogen bond N-H…O along c direction

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  Figure 3  (a) Asymmetric unit of 3 drawn with 30% thermal ellipsoids; (b) [CoCl₄] tetrahedrons connected by water molecules using hydrogen bonds O-H…Cl along a and b directions to form 2D layer; (c) (btzH)⁺ cations suspended on the 2D layers using hydrogen bond N-H…O_water along c direction

  Symmetry codes: ^ⅰ -x+1, y, -z+1/2

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  Figure 4  UV-Vis spectra of compounds 1~3 in solid states

  Inset: free btz in solution

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  Figure 5  Emission spectra of compounds 1~3 in the solid states

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  Table 1.  Crystal data and structure refinement for compounds 1~3

  Compound	1	2	3
  Formula	C7H6NSCl3Pb	C14H16N2O2S2Cl4Cd	C14H16N2O2S2Cl4Co
  Formula weight	449.75	562.64	509.16
  Crystal system	Triclinic	Triclinic	Monoclinic
  Space group	P1	P1	C2/c
  a/nm	0.425 31(16)	0.740 78(5)	1.159 2(5)
  b/nm	1.146 2(4)	0.772 47(5)	1.007 7(4)
  c/nm	1.288 7(5)	1.890 52(11)	1.798 5(7)
  α/(°)	64.830(7)	101.000 0(10)	90
  β/(°)	82.343(8)	96.678 0(10)	104.142(4)
  γ/(°)	84.459(8)	94.541 0(10)	90
  V/nm3	0.561 0(4)	1.049 02(12)	2.037 2(14)
  Z	2	2	4
  Dc/(g·cm-3)	2.653	1.781	1.660
  μ/mm-1	15.833	1.760	1.583
  F(000)	408	556	1 028
  θmax	25.00	36.57	27.88
  Total reflection	3 382	12 228	7 893
  Unique reflection	1911(Rint=0.0418)	8 205 (Rint=0.013 5)	2 248 (Rint=0.016 6)
  Completeness /%	97.0	99.3	98.6
  No. of variables	123	250	127
  GOF	1.090	1.072	1.041
  R1, wR2[I>2σ(I)]	0.033 3,0.086 7	0.037 6,0.084 4	0.022 9,0.058 5
  R1, wR2(all data)	0.034 0,0.087 5	0.048 7,0.092 7	0.027 5,0.061 1

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  Table 2.  Selected bond lengths (nm) and angles (°) for 1

  Pb(1)-Cl(1)	0.279 9(2)	Pb(1)-Cl(2)	0.304 3(2)	Pb(1)-Cl(3)	0.275 6(2)
  Pb(1)-Сl(2)ⅰ	0.289 1(3)	Pb(1)-Cl(1)ⅱ	0.293 7(2)	Pb(1)-Cl(2)ⅲ	0.297 2(3)
  Cl(2)ⅰ-Pb(1)-Cl(2)	81.50(7)	Cl(1)ⅱ-Pb(1)-Cl(2)ⅲ	83.43(7)	Cl(2)ⅲ-Pb(1)-Cl(2)	83.76(7)
  Cl(3)-Pb(1)-Cl(1)	86.63(7)	Cl(1)-Pb(1)-Cl(2)ⅰ	87.38(7)	Cl(1)-Pb(1)-Cl(2)	90.90(7)
  Cl(3)-Pb(1)-Cl(1)ⅱ	92.54(7)	Cl(1)-Pb(1)-Cl(2)ⅱ	92.90(7)	Cl(2)ⅰ-Pb(1)-Cl(2)ⅲ	92.99(7)
  Cl(3)-Pb(1)-Cl(2)ⅰ	93.16(7)	Cl(1)-Pb(1)-Cl(1)ⅱ	95.69(7)	Cl(3)-Pb(1)-Cl(2)ⅲ	98.79(6)
  Cl(1)-Pb(1)-Cl(2)ⅲ	174.53(6)	Cl(3)-Pb(1)-Cl(2)	174.23(6)
  Symmetry codes: ⅰ -x, -y+3, -z-1; ⅱ x+1, y, z; ⅲ -x+1, -y+3, -z-1.

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  Table 4.  Hydrogen bonds for compounds 1, 2 and 3

  D-H…A	d(D-H)/nm	d(H…A)/nm	d(D…A)/nm	∠DHA/(°)
  1
  N(1)-H(1)…Cl(3)ⅰ	0.076	0.245	0.310	145
  2
  O(2)-H(W1)…Cl(3)ⅱ	Pb079(5)	Pb242(5)	0.3l5 9(3)	l55(5)
  N(1)-H(1A)…O(2)	0.082(3)	0.190(3)	0.270 0(3)	168(3)
  N(2)-H(2)…O(1)ⅲ	0.091(3)	0.180(3)	0.271 0(4)	176(3)
  O(2)-H(W2)…Cl(4)ⅳ	0.085(5)	0.241(5)	0.319 9(3)	156(5)
  O(1)-H(W3)…Cl(3)	0.088(8)	0.248(8)	0.330 5(4)	157(6)
  O(1)-H(W4)…Cl(2)ⅱ	P0.074(7)	0.280(6)	0.336 1(4)	135(6)
  3
  N(1)-H(1)…O(1)	0.083 0	0.194 3	0.275 6	166.33
  O(1)-H(1)…Cl(2)ⅴ	0.076 7	0.252 7	0.320 5	148.32
  O(1)-H(2W)…Cl(1)	0.080 0	0.243 3	0.321 3	165.47
  Symmetry codes: ⅰ -x, 2-y, -z for 1; ⅱ x, -1+y, z; ⅲ 1-x, 1-y, 1-z; ⅳ 1+x, -1+y, z for 2; ⅴ 1/2+x, 1/2+y, z for 3.

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  Table 3.  Selected bond lengths (nm) and angles (°) for 2 and 3

  2
  Cd(1)-Cl(1)	0.244 34(7)	Cd(1)-Cl(2)	0.245 07(7)	Cd(1)-Cl(3)	Pb247 53(7)
  Cd(1)-Cl(4)	0.245 39(6)
  Cl(1)-Cd(1)-Cl(2)	114.25(3)	Cl(1)-Cd(1)-Cl(4)	108.26(3)	Cl(2)-Cd(1)-Cl(4)	110.78(3)
  Cl(1)-Cd(1)-Cl(3)	105.28(3)	Cl(2)-Cd(1)-Cl(3)	108.77(3)	Cl(4)-Cd(1)-Cl(3)	109.29(3)
  3
  Co(1)-Cl(1)	0.227 75(7)	Co(1)-Cl(2)	0.226 04(7)
  Cl(2)-Co(1)-Cl(2)ⅰ	111.19(4)	Cl(2)-Co(1)-Cl(1)	109.91(3)	Cl(2)ⅰ-Co(1)-Cl(1)	108.87(3)
  Cl(1)-Co(1)-Cl(1)ⅰ	108.03(4)
  Symmetry codes: ⅰ -x+1, y, -z+1/2 for complex 3.

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