Synthesis,characterization and fluorescence spectra of mixed ligand Zn(II), Cd(II) and Hg(II) complexes with 1,10-phenanthroline-5,6-dione ligand

The novel mixed ligand complexes [M(bpy)(phen-dione)](PF₆)₂ (M?=?Zn(II), Cd(II) and Hg(II), bpy?=?2,2^′-bipyridine and phen-dione?=?1,10-phenanthroline-5,6-dione) have been synthesized and characterized by elemental analysis, IR, ¹H NMR and electronic absorption spectroscopies. The ν(C=O) of coordinated phen-dione in these complexes are very similar to the free phen-dione ligand showing that phen-dione is not coordinated to metal ion from its C=O sites. Absorption spectra of the complexes show two absorption bands for intraligand transitions. These absorption bands show dependence to the dielectric constant of solvent. These complexes exhibit an intensive fluorescence band around 535?nm in DMF when the excitation wavelength is 260?nm at room temperature. The fluorescence intensity of these complexes is larger than that of the free ligand.     

Synthesis,characterization, cyclic voltammetry and biological studies of Zn (II), Cd (II), Hg (II) and UO22+ complexes of thiosemicarbazone salt

Zn (II), Cd (II), Hg (II) and U (VI)O₂²⁺ complexes of water‐soluble thiosemicarbazone ligand (NaH₃PyTSC) have been prepared and characterized using various techniques. Fourier transform‐infrared (FT‐IR) demonstrated that NaH₃PyTSC ligand behaves as a binegative NOS tridentate in [Hg(H₂PyTSC)(H₂O)]₂ and [UO₂(H₂PyTSC)(H₂O)]₂ complexes via the deprotonated SH, (C=N)_az groups from one molecule and SO₃^? group from another molecule, while it behaves as a binegative NNSO tetradentate in [Cd(H₂PyTSC)(H₂O)₂]₂ complex through the deprotonated SH group, the SO₃^? group and the nitrogen of both the (C=N)_az and (C=N)_py. Finally, it behaves as a binegative OO bidentate in [Zn(H₂PyTSC)(H₂O)₂]₂·2H₂O complex by the deprotonated OH group from one molecule and SO₃^? group from another ligand molecule. The spectral data suggest a tetrahedral coordination around Hg (II) and Zn (II) ions, and an octahedral coordination around Cd (II) and U (VI)O₂²⁺ ions. The NaH₃PyTSC ligand exhibited maximum luminescent intensity at 501 nm, while Zn (II), Cd (II) and Hg (II) chelates show emission bands at 459, 458 and 358 nm, respectively. Two comparable methods were used to estimate various thermodynamic parameters. Cyclic voltammetry has been studied for Cd (II) complex in solution. Different biological applications of the isolated complexes have been estimated. It was found that [Cd(H₂PyTSC)(H₂O)₂]₂ showed the most effective antioxidant and anticancer activity.     

Antitumor Activity and Physicochemical Properties of New Thiosemicarbazide Derivative and Its Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) Complexes

A novel biologically active thiosemicarbazide derivative ligand L (N-[(phenylcarbamothioyl)amino]pyridine-3-carboxamide) and a series of its five metal(II) complexes, namely: [Co(L)Cl₂], [Ni(L)Cl₂(H₂O)], [Cu(L)Cl₂(H₂O)], [Zn(L)Cl₂] and [Cd(L)Cl₂(H₂O)] have been synthesized and thoroughly investigated. The physicochemical characterization of the newly obtained compounds has been performed using appropriate analytical techniques, such as ¹H and ^l3C nuclear magnetic resonance (NMR), inductively coupled plasma (ICP), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR) and magnetic measurements. In order to study the pharmacokinetic profile of the compounds, ADMET analysis was performed. The in vitro studies revealed that the synthesized compounds exhibit potent biological activity against A549 human cancer cell line.     

Zinc(II), Cadmium(II), and Mercury(II) Complexes of 2-Methyl-benzoselenazole

The following zinc(II), cadmium(II) and mercury(II) complexes of 2-methyl-benzoselenazole (L) have been prepared and studied by conductometric and i.r. methods: MLX₂ (M ? Cd, Hg, X ? Cl, Br, I), ML_1.5X₂ (M ? Zn, X ? ClO₄(4 H₂O); M ? Hg, X ? NO₃, ClO₄), ML₂X₂ (M ? Zn, X ? Cl, Br, I, NO₃; M ? Cd, X ? NO₃, ClO₄). The ligand is N-bonded. All the anions are coordinated.     

Synthesis,structural characterization,antimicrobial, DNA-binding,and photo-induced DNA cleavage activity of some bio-sensitive Schiff base copper(II) complexes

Schiff base mixed-ligand copper complexes [CuL¹(phen)Cl₂], [CuL¹(bipy)Cl₂], [Cu(L¹)₂Cl₂], [Cu(L²)₂Cl₂], [CuL²(bipy)Cl₂], and [CuL²(phen)Cl₂] (where L^1?=?4-[3,4-dimethoxy-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; L^2?=?4-[3-hydroxy-4-nitro-benzylidene]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazole-3-one; phen?=?1,10-phenanthroline; and bipy?=?2,2′-bipyridine) have been synthesized and characterized. Their DNA-binding properties have been studied by electronic absorption spectra, viscosity, and electrochemical measurements. The absorption spectral and viscosity results suggest that the copper(II) complexes bind to DNA via partial intercalation. The addition of DNA resulting in the decrease of the peak current of the copper(II) complexes indicates their interaction. Interaction between the complexes and DNA has also been investigated by submarine gel electrophoresis. The copper complexes cleave supercoiled pUC19 DNA to nicked and linear forms through hydroxyl radical and singlet oxygen in the presence of 3-mercaptopropionic acid as the reducing agent. These copper complexes promote the photocleavage of pUC19 DNA under irradiation at 360?nm. Mechanistic study reveals that singlet oxygen is likely to be the reactive species responsible for the cleavage of plasmid DNA by the synthesized complexes. The in vitro antimicrobial study indicates that the metal chelates have higher activity against the bacterial and fungal strains than the free ligands.     

Molecular modeling,spectral, and biological studies of 4-formylpyridine-4 N-(2-pyridyl) thiosemicarbazone (HFPTS) and its Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Cd(II), Hg(II), and UO2(II) complexes

The present work describes the preparation and characterization of some metal ion complexes derived from 4-formylpyridine-⁴ N-(2-pyridyl)thiosemicarbazone (HFPTS). The complexes have the formula; [Cd(HFPTS)₂H₂O]Cl₂, [CoCl₂(HPTS)]·H₂O, [Cu₂Cl₄(HPTS)]·H₂O, [Fe (HPTS)₂Cl₂]Cl·3H₂O, [Hg(HPTS)Cl₂]·4H₂O, [Mn(HPTS)Cl₂]·5H₂O, [Ni(HPTS)Cl₂]·2H₂O, [UO₂(FPTS)₂(H₂O)]·3H₂O. The complexes were characterized by elemental analysis, spectral (IR, ¹H-NMR and UV–Vis), thermal and magnetic moment measurements. The neutral bidentate coordination mode is major for the most investigated complexes. A mononegative bidentate for UO₂(II), and neutral tridentate for Cu(II). The tetrahedral arrangement is proposed for most investigated complexes. The biological investigation displays the toxic activity of Hg(II) and UO₂(II) complexes, whereas the ligand displays the lowest inhibition activity toward the most investigated microorganisms.     

Three multinuclear Co(II), Zn(II) and Cd(II) complexes based on a single-armed salamo-type bisoxime: syntheses,structural characterizations and fluorescent properties

Three multinuclear complexes, [Co(L)(OAc)Co(CH₃CH₂OH)₂]·H₂O, [Zn(L)(OAc)Zn(CH₃OH)], and [{Cd(L)(OAc)Cd(CH₃OH)}₂], containing a single-armed salamo-type bisoxime H₃L have been synthesized and characterized structurally. The Co(II) complex forms a dimeric unit by intermolecular hydrogen bond interactions of neighboring dimeric molecules. The Zn(II) complex also forms a dimeric unit by intermolecular hydrogen bond interactions. Interesting features of the crystal structure include O?O short contacts. Meanwhile, self-assembling infinite 1-D, 2-D, and 3-D supramolecular structures are formed by intermolecular hydrogen bond and C–H?π interactions. The Cd(II) complex forms an infinite 2-D supramolecular structure by intermolecular hydrogen bond interactions. The photophysical properties of the Co(II), Zn(II), and Cd(II) complexes have also been discussed.     

Effect of water on zinc (II), cadmium (II) complexes with pyridylimidazole: Theoretical study of stability and electronic spectrum

The geometry structures of complexes such as [Zn(PIm)₂(H₂O)] and [Cd(PIm)₂(H₂O)₂] [PIm = (2‐(2′‐pyridyl) imidazole)] are optimized by density functional theory (DFT) B3LYP methods. On the basis of their stable structures, the stability of the coordinated water existing in the complexes is analyzed quantitatively in terms of the interaction between the central metal and the coordinated water. The interaction energy of the Zn pyridylimidazole complex increased obviously by considering the intermolecular hydrogen bond (O? H…N). The theoretical calculation well explained penta‐ and hexa‐coordinated conformation, respectively, in Zn and Cd pyridylimidazole complexes. The spectral properties of the Zn Cd complexes have been studied by time‐dependent density functional theory (TD‐DFT). The calculation results show that the coordinated waters in Cd complexes have little effect on their spectral properties. While the axially coordinated waters in Zn pyridylimidazole cause a red shift in the absorption wavelength and change the pattern of charge transfer as a result of the effect of polarization from intermolecular hydrogen bond. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Complexation of Zn(II), Cd(II) and Hg(II) with thiourea and selenourea: A 1H, 13C, 15N, 77Se and 113Cd solution and solid-state NMR study

Zinc(II), cadmium(II) and mercury(II) complexes of thiourea (TU) and selenourea (SeU) of general formula M(TU)₂Cl₂ or M(SeU)₂Cl₂ have been prepared. The complexes were characterized by elemental analysis and NMR (¹H, ¹³C, ¹⁵N, ⁷⁷Se and ¹¹³Cd) spectroscopy. A low-frequency shift of the C=S resonance of thiones in ¹³C NMR and high-frequency shifts of N–H resonances in ¹H and ¹⁵N NMR are consistent with sulfur or selenium coordination to the metal ions. The Se nucleus in Cd(SeU)₂Cl₂ in ⁷⁷Se NMR is deshielded by 87?ppm on coordination, relative to the free ligand. In comparison, the analogous Zn(II) and Hg(II) complexes show deshielding by 33 and 50?ppm, respectively, indicating that the orbital overlap of Se with Cd is better. Principal components of ⁷⁷Se and ¹¹³Cd shielding tensors were determined from solid-state NMR data.     

Zn(II), Cd(II) and Hg(II) complexes of 6-amino-1-methyl-5-nitrosouracil

The following Zn(II), Cd(II) and Hg(II) complexes of neutral and deprotonated 6-amino-1-methyl-5-nitroso-uracil (HL) were prepared and studied by u.v.-vis, ¹H-NMR and i.r. techniques: ZnL₂·4H₂O,ZnL₂(H₂O)₂·H₂O, CdCl₂(HL)₂·2H₂O and HgL₂·2H₂O. In Zn(II) and Hg(II) complexes, the ligand is coordinated in anionic nitroso-phenolic form, acting as a bidentate ligand through the nitrogen and oxygen atoms of the 5-nitroso and 6-oxide groups, respectively. In the cadmium complex, the ligand seems to be either N,O- or only N-bound to the metal ion, with chlorine bridging. From the data obtained, molecular structures are proposed for each complex.     

Zinc (II), cadmium (II) and mercury (II) complexes of 2-methyl-benzoxazole

The following zinc (II), cadmium (II) and mercury (II) complexes of 2-methyl-benzoxazole (L) have been prepared and studied by conductometric and i.r. methods: MLX₂ (MCd, XCl, Br; MHg, XCl), HgL_1.5X₂ (XBr, ClO₄), ML₂X₂ (MZn, XCl, Br, I, NO₃; MCd, Hg, XI, NO₃), ZnL₃(ClO₄)₂·2H₂O, CdL₃(ClO₄)₂·3H₂O. The frequency decrease of the ligand bands at 1614 and 1573 cm⁻¹ having a ν(CN) and the increase of the ligand band at 918 cm⁻¹ having a ν(CO) contribution indicate that in the complexes the ligand is N-bonded to the metal.     

Interaction of Co(II), Ni(II), Cu(II), and Zn(II) with 12- and 14-membered macrocycles containing O2N2 donors

The 12- and 14-membered diazadioxo macrocyclic ligands, 1,2?:?7,8-diphenyl-6,9-diaza-3,12-dioxocyclododecane (L¹) and 1,2?:?8,9-diphenyl-7,10-diaza-3,14-dioxocyclotetradecane (L²), were synthesized by condensation between o-phenylenediamine, 1,2-dibromoethane/1,3-dibromopropane, and catechol. Metal complexes [ML¹Cl₂] and [ML²Cl₂] [M?=?Co(II), Ni(II), Cu(II), and Zn(II)] were prepared by interaction of L¹ or L² with metal(II) chlorides. The ligands and their complexes were characterized by elemental analyses, IR, ¹H, and ¹³C NMR, EPR, UV-Vis spectroscopy, magnetic susceptibility, conductivity measurements, and Electrospray ionization-mass spectral (ESI-MS) studies. The results of elemental analyses, ESI-MS, Job's method, and conductivity measurements confirmed the stoichiometry of ligands and their complexes while absorption bands and resonance peaks in IR and NMR spectra confirmed the formation of ligand framework around the metal ions. Stereochemistry was inferred from the UV-Vis, EPR, and magnetic moment studies.     

Zinc(II) and Cadmium(II) Metal Complexes with Bis(tetrazole) Ligands: Synthesis and Crystal Structures

Two new metal complexes [Zn( L¹ )]_n ( 1 ) and [Cd₃( L² )₂Cl₂(H2O)6]_n ( 2 ) (H₂ L¹ = 1,5‐bis(tetrazol‐5‐yl)‐3‐oxapentane, H₂ L² = bis(tetrazol‐5‐yl)methane) have been synthesized and characterized by elemental analysis, IR spectroscopy and single‐crystal X‐ray diffraction analysis. Complex 1 was a 2‐D sheet constructed by L¹ and Zn(II) center, further assembled to form a three‐dimensional (3‐D) supramolecular networks through weak hydrogen‐bonding interactions. In the complex 2 , there were two unequivalent Cd(II) centers, and some of ligands L² adopted chelate coordination mode, and others adopted bridge coordination mode linking the Cd1 center and simultaneously bridging the Cd2 center, the Cl^‐ anions adopted μ₂ bridging mode, ligands L² and the Cl^‐ anions linked the Cd(II) centers to form a 3‐D supramolecular networks.     

Synthesis, crystal structure, electrochemical and fluorescence studies of a novel Zn(II)-fluorophore, 1,10-phenanthroline-5,6-dione (phen-dione)

The crystal structure of 1,10-phenanthroline-5,6-dione ligand with Zn(II), tris(1,10-phenanthroline-5,6-dione)zinc(II) hexafluorophosphate, [Zn(phen-dione)₃](PF₆)₂, is reported. The complex was characterized by elemental analysis, IR, ¹H NMR, electronic absorption spectroscopies, cyclic voltammetry and X-ray crystallography. Yellow crystals of [Zn(phen-dione)₃](PF₆)₂ were formed by ether diffusion into an acetonitrile solution of the complex. The title complex crystallized in monoclinic crystal system (Z = 2) with space groups of P2 ₁, a = 12.0299(15) Å, b = 14.5306(19) Å, c = 13.1879(17) Å, β = 94.058(2)º and V = 2299.5(5) ų. The structure was refined by using 10048 independent reflections, with I > 2σ(I) to an R factor of 0.0490. Single-crystal structure showed that the coordination geometry around the Zn(II) was a distorted octahedron. The complex showed an intense fluorescence band at visible region (690 nm) in CH₃CN with an excitation wavelength of 310 nm at 25.0 ± 0.1 ºC. Cyclic voltammogram of the title complex showed two quasi-reversible reduction couples at negative potential, which were assigned to the consecutive reduction of phen-dione ligand to phen-semiquinonate and phen-diolate respectively by analogy to other phen-dione complexes at scan rate 200 mV s^-1.     

Synthesis and spectral characterization of zinc(II) and cadmium(II) complexes of acetone-N(4)-phenylsemicarbazone: Crystal structures of acetone-N(4)-phenylsemicarbazone and a cadmium(II) complex

Seven Zn(II) and Cd(II) complexes of ON donor acetone-N(4)-phenylsemicarbazone (HL) have been synthesized and physico-chemically characterized by partial elemental analyses, molar conductance measurements, infrared, electronic and ¹H NMR spectral studies. The semicarbazone binds the metal as a neutral bidentate ligand in all the complexes. The crystal structures of acetone-N(4)-phenylsemicarbazone and [Cd(HL)₂Cl₂] have been determined by X-ray diffraction studies. The coordination geometry around cadmium(II) in the complex [Cd(HL)₂Cl₂] is distorted octahedral.     

New homoleptic metal complexes of Schiff bases derived from 2,4-di-p-tolyl-3-azabicyclo[3.3.1]nonan-9-one

New bidentate Schiff-base ligands 2-(2,4-di-p-tolyl-3-azabicyclo[3.3.1]nonan-9-ylidene)hydrazinecarbothioamide HL¹ and 2-(2,4-di-p-tolyl-3-azabicyclo[3.3.1]nonan-9-ylidene)hydrazinecarboxamide HL² were synthesized from the condensation of 2,4-di-p-tolyl-3-azabicyclo[3.3.1]nonan-9-one with thiosemicarbazide and semicarbazide, respectively. Homoleptic complexes of these ligands, of general formula K[Cr(L ⁿ )₂Cl₂], K₂[Mn(L ⁿ )₂Cl₂], K₂[Fe(L¹)₂Cl₂] and [M(L ⁿ )₂] (where M = Co(II), Ni(II) Cu(II), Zn(II), Cd(II), and Hg(II) ions; n = 1 or 2) are reported. The mode of bonding and overall geometry of the complexes were determined through IR, UV-Vis, NMR and mass spectral studies, magnetic moment measurements, elemental analysis, metal content, and conductance. These studies revealed octahedral geometry for Cr(III), Mn(II), and Fe(II) complexes, square planar for Cu(II), Co(II), and Ni(II) complexes and tetrahedral for Zn(II), Cd(II), and Hg(II) complexes.     

Hg(II), Tl(III), Cu(I), and Pd(II) Complexes with 2,2'-Diphenyl-4,4'-Bithiazole (DPBTZ), Syntheses and X-Ray Crystal Structure of [Hg(DPBTZ)(SCN)2]

Reaction of the ligand 2,2′-diphenyl-4,4′-bithiazole (DPBTZ) with Hg(SCN)₂, Tl(NO₃)₃, CuCl, and PdCl₂ gives complexes with stoichiometry [Hg(DPBTZ)(SCN)₂], [Tl(DPBTZ)(NO₃)₃], [Cu(DPBTZ)(H₂O)Cl]_, and [Pd(DPBTZ)Cl₂]. The new complexes were characterized by elemental analyses and infrared spectroscopy. The crystal structure of [Hg(DPBTZ)(SCN)₂] determined by X-ray crystallography. The Hg atom in the title monomeric complex, (2,2′-diphenyl-4,4′-bithiazole)mercury(II)bisthiocyanate, [Hg(C₁₈H₁₂N₂S₂)(SCN)₂], is four-coordinate having an irregular tetrahedral geometry composed of two S atoms of thiocyanate ions [Hg-S 2.4025(15) and 2.4073(15) Å] and two N atoms of 2,2′-diphenyl-4,4′-bithiazole ligand [Hg-N 2.411(4) and 2.459(4) Å]. The bond angle S(3)-Hg(1)-S(4) of 147.46(5)° has the greatest derivation from ideal tetrahedral geometry. Intermolecular interaction between Hg(1) and two S atoms of two neighboring molecules, 3.9318(15) and 3.9640(18) Å, make the Hg(1) distort from a tetrahedron to a disordered octahedron. The attempts for preparation complexes of Tl(I), Pb(II), Bi(III), Cd(II) ions with 2,2′-diphenyl-4,4′-bithiazole ligand were not successful and also the attempts for preparation complexes of 4,4′,5,5′-tetraphenyl-2,2′-bithizole ligand with Cu(II), Ni(II), Co(II), Co(III), Mn(II), Mn(III), Fe(II), Fe(III), Cr(III), Zn(II), Tl(III), Pb(II), Hg(II), Cu(I), Pd(II) were not successful. This point can be regarded as the initial electron withdrawing of phenyl rings and also their spatial steric effects.     

Zinc(II), cadmium(II) and mercury(II) complexes of neutral and deprotonated 4,6-dimethylpyrimidine-2(1H)-thione

The following zinc(II), cadmium(II) and mercury(II) complexes of neutral and deprotonated 4,6-dimethylpyrimidine-2(1H)-thione (HL) have been prepared and studied by conductometric and i.r. methods: [M(HL)₂X₂] (M  Zn, Cd, Hg; X  Cl, Br, I), [M(HL)₃]A₂·2H₂O (M  Zn, Cd; A  ClO₄ and M  Hg; A  ClO₄, BF₄, CF₃COO), M(HL)₂(CF₃COO)₂(M  Zn, Cd), ZnL₂·HL and ML₂ (M  Cd, Hg). In most of the complexes the ligand is N,S-bonded to the metal ion, the metal-nitrogen bond being stronger than the metal-sulphur one; only in the cadmium chloride and bromide complexes the ligand seems to be only N-bonded to the metal, with bridging halide ions. Most of the complexes seem to have a distorted six-coordination while to the neutral HgL₂ complex a tetrahedral [N,S]₂ coordination may be assigned.     

Structural and Coordinative Variability in Zinc(II), Cadmium(II), and Mercury(II) Complexes of 2‐Pyridineformamide 3‐Hexamethyleneiminylthiosemicarbazone

Sodium in dry methanol reduces 2‐cyanopyridine in the presence of 3‐hexamethyleneiminylthiosemicarbazide and produces 2‐pyridineformamide 3‐hexamethyleneiminylthiosemicarbazone, HAmhexim ( 1 ). Complexes with zinc(II ), cadmium(II ) and mercury(II ) have been prepared and characterized by spectroscopic techniques. In addition, the crystal structures of HAmhexim ( 1 ), [Zn(Amhexim)(OAc)]₂μ·μDMSO ( 2 ), [Cd(HAmhexim)Cl₂]μ·μDMSO ( 7 ), [Cd(Amhexim)₂] ( 8 ), [Cd(HAmhexim)Br₂]μ·μDMSO ( 9 ), [Cd(HAmhexim)I₂]μ·μEtOH ( 10 ), [Hg(HAmhexim)Cl₂]μ·μDMSO ( 11 ), [Hg(Amhexim)Br]₂ ( 13 ), [Hg₃(HAmhexim)(Amhexim)Br₅]μ·μH₂O ( 14 ) and [Hg(Amhexim)I]₂ ( 15 ) have been determined. Coordination of the anionic and neutral thiosemicarbazone ligand occurs through the pyridine nitrogen atom, imine nitrogen atom, and thiolato or thione sulfur atom. In [Zn(Amhexim)(OAc)]₂ one of the bridging acetato ligands has monodentate coordination and the other bridges in a bidentate manner. [Cd(Amhexim)₂] is a 6‐coordinate species while the other cadmium complexes are 5‐coordinate. In [Hg(Amhexim)Br]₂ and [Hg(Amhexim)I]₂ the thiolato sulfur atoms act as bridges between the Hg atoms to form dimeric compounds and [Hg₃(HAmhexim)(Amhexim)Br₅]μ·μH₂O is a trinuclear complex with three different centers — two metallic centers have a 5‐coordination and the another one has 4‐coordination. In addition, [Hg(HAmhexim)Cl₂]μ·μDMSO and [Hg₃(HAmhexim)(Amhexim)Br₅]μ·μH₂O shown a supramolecular one‐dimensional hydrogen‐bonded self‐assembling.     

Complexes of 1-methyl-4-mercaptopiperidine with zinc(II), cadmium(II) and mercury(II) halides

The preparation of a series of complexes formed by 1-methyl-4-mercaptopiperidine (AH) and divalent zinc, cadmium and mercury halides is reported together with some spectral and physical properties. The results of a crystallographic study allows to establish the structure of those of formula [M₂(AH)₂X₄]H₂O (M = Zn, Cd, Hg; X = Br, I) consisting of dimers and involving tetrahedral environment with sulphur-bridges for the metal atoms. Polymeric structures are proposed for the complexes of formulae Cd(AH)Cl₂ and Hg₂Cl₄(AH).