Functionalized zinc(II) dithiocarbamate complexes: Synthesis,spectral and molecular structures of bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II) and (2,2′-bipyridine)bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II)

Two new zinc and dithiocarbamate integrated metal complexes such as bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II) (1) and (2,2′-bipyridine)bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II) (2) have been synthesized and their spectral investigations viz., FT-IR, ¹H and ¹³C NMR as well as single crystal X-ray diffraction studies have been accomplished. Single crystal X-ray analysis of the complex 1 reveals the presence of distorted trigonal bipyramidal and tetrahedral coordination geometry around the zinc. The dithiocarbamate motif acts as bidentate chelating and bidentate bridging ligands between the zinc ions furnishing centrosymmetric dimeric molecules. In the complex 2, the zinc is in a distorted octahedral environment with a ZnS₄N₂ chromophore. The supramolecular frameworks in the complexes 1 and 2 have been sustained by CH?S, CH?O and CH?π (ZnCS₂, and chelate) interactions. Computational studies on complexes 1 and 2 have been executed utilizing DFT-B3LYP/ LANL2DZ method. In both the cases, the HOMO-LUMO calculations imply the occurrence of effective charge transfer within the molecule. Further, the MEP analysis of 1 and 2 implies the negative potential sites are sulfur of NCS₂ and oxygen of OCH₃ and the positive potential sites are nitrogen of NCS₂ in both the complexes along with 2,2′-bipyridine for complex 2. The former sites are susceptible for electrophilic reactions while the latter for nucleophilic reactions.     

Cobalt(II) and nickel(II) complexes of N(4′) substituted 3- and 4-acetylpyridine thiosemicarbazones

Co^II and Ni^II complexes of N(4)-methyl and N(4)-ethyl thiosemicarbazones derived from 3- and 4-acetylpyridine have been prepared and characterized by microanalyses, magnetic susceptibility and molar conductivity measurements and by their electronic, i.r. and n.m.r. (in the case of Ni^II complexes) spectra.     

Mercury(II) complexes of pyrrolidinedithiocarbamate,crystal structure of bis{[μ2-(pyrrolidinedithiocarbamato-S,S ′)(pyrrolidinedithiocarbamato-S,S ′)mercury(II)]}

Mercury(II) complexes of pyrrolidinedithiocarbamate (PDTC) having the general formula [Hg(PDTC)X] (X = Cl^?, SCN^?, and CN^?) and [Hg(PDTC)₂] have been prepared and characterized by elemental analysis, IR, and NMR. The crystal structure of [Hg(PDTC)₂] has also been determined by X-ray crystallography, showing that the complex is a centrosymmetric dimer, [Hg₂(PDTC)₄] (bis[µ²-(pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)mercury(II)]) (1). The solid-state structure of 1 contains two crystallographically equivalent Hg(II) centers in a distorted tetrahedron.     

Synthesis,Infrared Spectroscopic,and Cyclic Voltammetric Studies on 1,10-Phenanthroline and 2,2′ -Bipyridine Adducts of Bis(4-morpholinecarbodithioato-S,S′)zinc(II) and Single-Crystal Structure Determination of (2,2′ -Bipyridine)bis(4-morpholinecarbodithioato-S,S′) zinc(II)

Abstract

(1,10-Phenanthroline)bis(4-morpholinecarbodithioato-S,S′)zinc(II), [Zn(mdtc)₂(1,10-phen)] ( 1 ) and (2,2′ -bipyridine)bis(4-morpholinecarbodithioato-S,S′) zinc(II), [Zn(mdtc)₂(bipy)] ( 2 ) adducts were prepared, and the crystal structure of 2 is reported. The Zn-S distances in 2 are longer than those in [Zn(dtc)₂](dtc = dithiocarbamate) complexes. The acceptance of an additional neutral ligand by the tetrahedral dithiocarbamato complex of zinc to form an octahedral adduct causes an increase in the Zn-S bond lengths and a consequent lowering of the S-Zn-S bite angle. The cyclic voltammetric study on the complexes shows an increase of electron density on the central metal ion in the adducts compared to Zn(mdtc)₂. The use of HMDE as a working electrode in the CV studies indicate the involvement of Hg in complex formation, which is otherwise absent with a platinum working electrode. The thioureide C-N distance of 1.330 ( 4 ) Å in compound 2 is in line with the ν _C?N observed at 1465 cm^?1.     

Synthesis and crystal structure of a dinuclear zinc(II)-dithiocarbamate complex,bis {[(μ 2-pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)zinc(II)]}

A new zinc(II) complex of pyrrolidinedithiocarbamate (PDTC), bis[(μ ²-pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)zinc(II)], [Zn₂(PDTC)₄] (1) has been prepared by reaction of ZnCl₂ with ammonium pyrrolidinedithiocarbamate in 1 : 1 and 1 : 2 ratio, respectively. The complex has been characterized by IR, NMR and X-ray crystallography. Compound 1 crystallizes in the triclinic space group P 1 in the form of a centrosymmetric dimer. The solid-state structure contains two crystallographically equivalent Zn⁺² centers in a tetrahedrally distorted ion sphere. A mixed-ligand complex, [Zn(PDTC)(MSC)]^? (MSC = mercaptosuccinate) was also prepared but the structure of the resulting complex was found to be the same as 1, suggesting that the thiolate ligand was replaced on addition of PDTC.     

trans-Bis(2-amino­pyridine-N)bis(O,O′-diiso­propyl di­thio­phosphato-S,S′)nickel(II)

In the title compound, [Ni(C₆H₁₄O₂PS₂)₂(C₅H₆N₂)₂], the coordination around the Ni atom, which lies on a crystallographic centre of symmetry, is octahedral with the S atoms from the di­thio­phosphate ligands occupying the equatorial positions, while the axial positions are occupied by the ring N atoms of the 2-amino­pyridine ligands. The mol­ecules form layers in the bc plane which are stacked in the direction of the a axis.     

Diaminodithioether complexes of nickel(II) and palladium(II): A unique case of dealkylation of S,S′-thioether

Summary Nickel(II) and palladium(II) complexes of the 1,3-di(o-aminophenylthio) propane (H₂L¹) and 1,2-di(o-aminophenylthio)xylene (H₂L²) ligands have been prepared and characterized. The hydrobromide salt of H₂L¹ gave a 12 ligand-metal complex of Pd^II, whereas free H₂L¹ formed the usual 1:1 species. The reaction of Na₂PdCl₄ with H₂L² resulted in S,S-dealkylation of the ligand and formation of a mononuclear complex of the corresponding thiol, i.e. 2-aminobenzenethiol. NiCl₂, NiBr₂ and Ni(ClO₄)₂ did not react directly with H₂L². Ni^II is a fairly hard ion and therefore does not coordinate to the soft thioether moiety in H₂L² in the absence of soft anions which symbiotically motivate Ni^II to act as a soft acceptor. It thus does not react with H₂L² in the presence of hard ions such as Cl^–, Br^- and ClO ₄ ^– , but, the in situ reaction of the constituents produced the tetrahedral Ni^II complex, contrary to earlier reports of similar types of octahedral species.     

Nitrogen-donor base adducts of bis(O,O′-di-isoamyldithiophosphato)nickel(II)

A series of Ni^II complexes with the O,O-di-isoamylester of dithiophosphoric acid and nitrogen-donor ligands of composition [Ni(i-Am₂dtp)₂(L)]; [dtp = O₂PS₂ ^–; L = 2,2-bipyridine (bpy); 1,10-phenanthroline (phen); 5-nitro-1,10-phenanthroline (nphen); 4,7-diphenyl-1,10-phenanthroline (baphen); 2,9-dimethyl-1,10-phenanthroline (neo), 2-aminomethylpyridine (amp), 2-(2-aminoethyl)pyridine (aep), 2,2-dipiridylamine (dpa), 1,2-diaminopropane (1,2-dap) or trans 1,2-diaminocyclohexane (dch)] have been prepared. The compounds have been characterized by elemental analyses (C,H,N,S), electronic and i.r. spectroscopy, magnetic and conductivity measurements and by cyclic voltammetry. The results show that all complexes behave as non-electrolytes in acetone. Electronic spectra and magnetic moments suggest a distorted cis-octahedral geometry around the Ni^II atom [_eff/_B <3.10, 3.40 >], except for [Ni(i-Am₂dtp)₂(aep)], where the measured temperature dependence of the magnetic susceptibility proved the tetrahedrally coordinated nickel [4.06 _eff/_B (298 K) – 3.20 _eff/_B (80 K)]. In the [Ni(i-Am₂dtp)₂(neo)] complex, the nickel atom is penta-coordinated. The X-ray crystal and molecular structure of [Ni(i-Am₂dtp)₂(1,2-dap)] has been determined.     

Synthesis of cobalt(II), nickel(II) and copper(II) complexes with 2-(2-hydroxyphenyliminomethyl)-1-(4-methyl-phenylsulfonamido)benzene and crystal structures of {bis(methanol)[2-(2′-N-tosylaminophenyl)iminomethyl]phenolato}nickel(II) and {bis(2,2′-bipyridine)[2-(2′-N-tosylaminophenyl)iminomethyl]phenolato}copper(II)

Electrochemical oxidation of metal anodes (cobalt, copper and nickel) in acetonitrile solutions of 2-(2-hydroxyphenyliminomethyl)-1-(4-methyl-phenylsulfonamido)benzene (H₂L) gave [CoL], [CuL] and [NiL] complexes. When 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) was added to the electrolytic cell, the mixed complexes [MLL′] (M=Co, Cu, L′=bipy or M=Ni, L′=phen) were obtained. A binuclear compound of composition [Ni₂L₂(MeOH)₄] (1) was synthesized by reaction of the ligand H₂L and nickel(II) acetate in methanol. X-ray structure determination showed the compound to be binuclear, with each nickel atom coordinated to two nitrogen and two bridging phenol oxygen atoms of two dianionic ligands and two methanol molecules, in an octahedral environment. The crystal structure of [CuLbipy] (2) was determined by X-ray diffraction; with the copper atom in a distorted bipyramidal environment defined by the two bipyridine nitrogen atoms and by the phenolic oxygen and the nitrogen atoms of the dianionic ligand. The electronic and vibrational spectral data of the complexes are discussed and related to the structure.     

Structural variations of nickel complexes in NiS4 and NiS2PN coordination environments: spectral and single-crystal X-ray structural studies on bis(4-methylpiperidinecarbodithioato-S,S′)nickel(II) and (4-methylpiperidinecarbodithioato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

Abstract  

[Ni(4-mpipdtc)₂] and [Ni(4-mpipdtc)(PPh₃)(NCS)] (4-mpipdtc = 4-methylpiperidinecarbodithioate anion) have been characterized by electronic, IR, and NMR spectroscopy, single crystal X-ray analysis, and cyclic voltammetry. IR spectra of the complexes show the contribution of the thioureide form to the structures. ¹H NMR spectra show the deshielding of α-CH₂ protons on complexation. ¹³C NMR spectra shows interesting differences between the N¹³CS₂ carbon signals of the parent complex [Ni(4-mpipdtc)₂] and the mixed ligand complex [Ni(4-mpipdtc)(PPh₃)(NCS)]. The N¹³CS₂ carbon signal for [Ni(4-mpipdtc)(PPh₃)(NCS)] is observed at 204.85 ppm with an upfield shift of about 3.8 ppm compared with that found in [Ni(4-mpipdtc)₂] (201.06 ppm). The observed shielding in [Ni(4-mpipdtc)(PPh₃)(NCS)] indicates the effect of PPh₃ on the mesomeric drift of electron density toward nickel through the thioureide C–N bond. Single crystal X-ray analysis of [Ni(4-mpipdtc)₂] and [Ni(4-mpipdtc)(PPh₃)(NCS)] confirms the presence of four-coordinated nickel in a distorted square-planar arrangement with the NiS₄ and NiS₂PN chromophores, respectively. The C–N (thioureide) bond lengths of [Ni(4-mpipdtc)(PPh₃)(NCS)] are shorter than those found in [Ni(4-mpipdtc)₂], because of the presence of the π-acid (triphenylphosphine) in [Ni(4-mpipdtc)(PPh₃)(NCS)]. Significant asymmetry in Ni–S bond distances was observed in Ni(4-mpipdtc)(PPh₃)(NCS)] (2.162(2) and 2.211(2) ?). This observation clearly supports the less effective trans effect of SCN^– over PPh₃. The piperidine ring in the dithiocarbamate fragment is in the normal chair conformation.     

Syntheses and crystal structures of (18-crown-6)bis(perchlorato-O,O′)strontium and (18-crown-6)bis(perchlorato-O,O′)barium

Two complexes, namely, (18-crown-6)bis(perchlorato-O,O′)strontium (I) and (18-crown-6)bis(perchlorato-O,O′)barium (II), are synthesized. Their crystal structures are determined by X-ray diffraction analysis. The structures of I (space group P2₁/c, a = 15.266 Å, b = 11.080 Å, c = 13.235 Å, β = 109.20°, Z = 4) and II (space group P2₁/n, a = 8.330 Å, b = 11.202 Å, c = 11.752 Å, β = 98.38°, Z = 2) are solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.077 (I) and 0.041 (II) against 3714 (I) and 2478 (II) independent reflections (CAD-4 diffractometer, λMoK _α radiation). Complex molecules [Sr(18C6)(ClO₄)₂] in the structure of I and [Ba(18C6)(ClO₄)₂] in II (in the inversion center)—are of the host-guest type. The Sr²⁺ or Ba²⁺ cation is localized in the center of a cavity of the 18-crown-6 ligand and coordinated by its all six O atoms. In compounds I and II, the coordination polyhedron of the Sr²⁺ and Ba²⁺ cations (coordination number 10) can be described as a distorted hexagonal bipyramid with two bifurcated vertices at two O atoms of two ClO ₄ ^? ligands, which are disordered in I and II and each of them has two orientations.     

Copper(II) and nickel(II) complexes with bis(azomethine)—a condensation product of 1-phenyl-3-methyl-4-formyl-5-mercaptopyrazole with 1,3-diaminopropan-2-ol

The copper(II) and nickel(II) complexes based on bis(azomethine), which is the condensation product of 1-phenyl-3-methyl-4-formyl-5-mercaptopyrazole with 1,3-diaminopropan-2-ol, are synthesized. Bis-azomethines can form both binuclear and mononuclear complexes in which the hydroxy group is not involved in coordination. The binuclear copper(II) complexes with the acetate and pyrazolate bridges exhibit an antiferromagnetic exchange, which strength is determined by the nature of the bridge (2J = ?154 and ?424 cm^?1, respectively). The structure parameters of the coordination spheres of the complexes are determined by X-ray absorption spectroscopy. The structure of the CHCl₃ solvate of the binuclear copper(II) complex with the pyrazolate bridge is solved by X-ray diffraction analysis (CIF file CCDC 964655).     

DNA-binding and photocleavage studies of metallofluorescein–porphyrin complexes of zinc(II) and copper(II)

The DNA-binding behaviors of the fluorescein?Cporphyrinatozinc(II) complex Zn(Fl-PPTPP) (Fl-PPTPP?=?5-(4-fluoresceinpropyloxy)phenyl-10,15,20-triphenylporphyrin) and fluorescein?Cporphyrinatocopper(II) complex Cu(Fl-PPTPP) with calf thymus DNA (CT-DNA) were investigated by UV?CVis absorption titrations, fluorescence spectra, viscosity measurements, thermal denaturation and circular dichroism. The results suggest that both complexes interact with CT-DNA by intercalation. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated. Both complexes exhibit significant DNA cleavage activity, and singlet oxygen may play an important role in these reactions.     

Synthesis and spectral studies on nitrogen donor adducts of bis(4-ethylpiperazinecarbodithioato-S,S′)M(II) (M = Zn,Cd) and use of adducts of cadmium dithiocarbamate for the preparation of cadmium sulfide

[M(4-epzdtc)₂(py)], [M(4-epzdtc)₂(1,10-phen)], and [M(4-epzdtc)₂(2,2′-bipy)] (where M?=?Zn(II), Cd(II); 4-epzdtc^??=?4-ethylpiperazinecarbodithioate) were synthesized and characterized by IR and NMR (¹H, ¹³C, HSQC and HMBC) spectra. A single-crystal X-ray analysis was carried out for [Zn(4-epzdtc)₂(py)]. The N¹³CS₂ chemical shifts of [M(4-epzdtc)₂] and its adducts follow the order: [M(4-epzdtc)₂] (ca 202?ppm)?<?[M(4-epzdtc)₂(py)] (ca 204?ppm)?<?[M(4-epzdtc)₂(N,N)] (N,N?=?1,10-phen, 2,2′-bipy) (ca 206?ppm), due to the change in coordination number. Single-crystal X-ray structural analysis of [Zn(4-epzdtc)₂(py)] showed that zinc is five-coordinate with four sulfurs from dithiocarbamate and one nitrogen from pyridine. This complex adopts a geometry intermediate between the tetragonal pyramid (C_4v) and trigonal bipyramid (D_3h). [Cd(4-epzdtc)₂] and its adducts were used as single source precursors for preparation of CdS. The as-prepared CdS was characterized by powder X-ray diffraction, UV-Vis absorption, and fluorescence spectroscopy. The UV-Vis absorption spectra of CdS particles indicate a blue shift in the absorption spectra due to the quantum size effect.     

Ruthenium(II) complexes of 2-(2′-pyridyl)naphthoimidazole: synthesis,characterization and DNA-binding studies

The perchlorate salts of two new ruthenium(II) complexes incorporating 2-(2′-pyridyl)naphthoimidazole are synthesized in good yield. Complexes [Ru(phen)₂(PYNI)]²⁺ (phen = 1,10-phenanthroline) 1 and [Ru(dmp)₂(PYNI)]²⁺ (dmp = 2,9-dimethyl-1,10-phenanthroline, PYNI = 2-(2′-pyridyl)naphthoimidazole) 2 are fully characterized by elemental analysis, FAB-MS, ES-MS, ¹H NMR and cyclic voltammetric methods. The DNA-binding behavior of the complexes have been studied by spectroscopic titration, viscosity measurements and thermal denaturation. Absorption titration and thermal denaturation studies reveal that these complexes are moderately strong binders of calf-thymus DNA (CT-DNA), with their binding constants spanning the range (2.73–5.35) × 10⁴ M^?1. The experimental results show that 1 interacts with calf thymus DNA (CT-DNA) by intercalative mode, while 2 binds to CT-DNA by partial intercalation.     

Synthesis and spectral studies of copper(II), nickel(II) and cobalt(II) complexes of 2-hydroxy-ω-4-X-cinnamoyl acetophenones and their pyridine adducts

Summary Complexes of the type M(HXCA)₂·nH₂O (M = Cu^II, Ni^II or Co^II; HXCA = 2-hydroxy--4-X-cinnamoyl acetophenone; X = H, Cl, Me or OMe; n = 0 or 2) have been synthesized, and characterized by elemental analysis, i.r., electronic, ¹H-n.m.r. and e.s.r. spectroscopies, and magnetic susceptibility measurements. The spectral data indicate that the ligand coordinates through both carbonyl and enolic oxygens. The anhydrous Cu^II complexes are monomeric and square planar, while the Ni^II and Co^II analogues possess polymeric high-spin octahedral structures. The diaquates and dipyridinates of Co^II and Ni^II have monomeric high-spin octahedral geometries.     

Syntheses and structures of nickel(II) and copper(II) complexes with biacetyl bis(benzoylhydrazone): one-dimensional self-assembly via π–π interaction and hydrogen bonding

Reactions of Ni(O₂CCH₃)₂·4H₂O and Cu(O₂CCH₃)₂·H₂O with biacetyl bis(benzoylhydrazone) (H₂babh) in alcoholic media afford mononuclear nickel(II) and copper(II) complexes of general formula [M(babh)]. The complexes have been characterized by microanalysis (C, H, N), magnetic susceptibility, and various spectroscopic measurements. X-ray structures of both complexes have been determined. The metal centre in [Ni(babh)] is in square-planar N₂O₂ environment provided by the tetradentate babh²⁻. On the other hand, [Cu(babh)] crystallizes as distorted square-pyramidal [Cu(babh)(CH₃OH)] from methanol. Here the tetradentate babh²⁻ constitutes the N₂O₂ square-base and the O-coordinating methanol occupies the apical site. In the crystal lattice, the molecules of [Ni(babh)] form a one-dimensional π-stacked structure. The [Cu(babh)(CH₃OH)] molecules also form a one-dimensional structure with alternating long and short Cu···Cu distances via intermolecular O–H···N hydrogen bonding and π–π interaction.     

Spectroscopic characterization and crystal structure of cis-Bis(N-(2-benzoyl)-N′,N′-diphenylthioureato-k 2O,S)nickel(II)

The title compound [Ni(C₂₀H₁₅N₂OS)₂] is prepared by the reaction of metal acetate with the corresponding acylthiourea derivative. The complex is characterized by elemental analysis, IR, ¹H and ¹³C NMR, and its structure is determined by single crystal X-ray diffraction. The Ni(II) ion is coordinated by the S and O atoms of two N-benzoyl-N??,N??-diphenylthiourea ligands in a slightly distorted square-planar coordination geometry. The two O and two S atoms are mutually cis to each other. The substance crystallizes triclinic (P-1 space group) with cell dimensions a = 10.7262(9) ?, b = 12.938(3) ?, c = 14.2085(12) ?, ?? = 74.650(4)°, ?? = 78.398(4)°, ?? = 68.200(5)°, and two formula units in the unit cell. The structure is very close to the related N-(2-furoyl) Ni complex reported previously.