Self-assembled macrocyclic molecular squares of Ni(II) derived from carbohydrazones and thiocarbohydrazones: Structural and magnetic studies

Four novel molecular square grids were achieved by self-assembly using the flexible ligands bis(di-2-pyridyl ketone) thiocarbohydrazone (H₂L¹), bis(quinoline-2-carbaldehyde) thiocarbohydrazone (H₂L²), bis(di-2-pyridyl ketone) carbohydrazone (H₂L³) and bis(2-benzoylpyridine) carbohydrazone (H₂L⁴). Three complexes were given a general formula of [Ni(HL)]₄[PF₆]₄ · nH₂O and one [Ni₂(HL²)L²]₂(PF₆)₂ · 7H₂O. The MALDI-MS spectra reveal the formation of tetranuclear molecular squares. The square grid of the Ni(II) centers in all the complexes were organized by deprotonated ligands. The complex [Ni(HL¹)]₄[PF₆]₄ · 11H₂O crystallized as [Ni(HL¹)]₄(PF₆)₄ · 0.5 CH₃CH₂OH · 2.8H₂O and X-ray study revealed octahedral geometries around the Ni(II) centers. Variable temperature magnetic studies suggest intramolecular antiferromagnetic coupling between the Ni(II) electrons by a super exchange mechanism through intervening sulfur/oxygen atoms.     

Structural and spectral studies of nickel(II) complexes with N(4),N(4)-(butane-1,4-diyl) thiosemicarbazones

Nickel(II) complexes of quinoline-2-carbaldehyde N(4),N(4)-(butane-1,4-diyl) thiosemicarbazone (HL¹) and 2-benzoylpyridine N(4),N(4)-(butane-1,4-diyl) thiosemicarbazone (HL²) have been synthesized and physico-chemically characterized by means of partial elemental analyses, molar conductance measurements, magnetic measurements, electronic and infrared spectral studies. Three complexes were given the formulae [Ni(HL¹)₂]Cl₂ (1), [Ni(HL²)L²]ClO₄ · 7H₂O (2) and [NiL²Cl] · 0.5H₂O (3). The structure of compound 1 has been solved by single crystal X-ray crystallography and is found to be distorted octahedral. Compound 2, when crystallized in DMSO solution, got deprotonated to form a new compound [Ni(L²)₂] (2a), with a distorted octahedral Ni(II) center. In compound 1, HL¹ coordinates to the metal in the thione form, while in compounds 2a and 3, HL² coordinates in its deprotonated thiolate form.     

Preparation and cytotoxic activity of nickel(II) complexes with 6-benzylaminopurine derivatives

Nickel(II) complexes with 6-benzylaminopurine (BAP) derivatives, namely 6-(3-chlorobenzylamino)purine (HL₁), 6-(4-chlorobenzylamino)purine (HL₂) and 6-(4-fluorobenzylamino)purine (HL₃), have been prepared and characterized by elemental analyses, i.r., u.v.–v.i.s., ES+ and FAB+ mass spectroscopy, magnetic susceptibility and conductivity measurements, and by thermal analysis. The complexes are: [Ni(L₁(H₂O)₂Cl] · H₂O, [Ni(L₁)(H₂O)-(NO₃)] · H₂O, [Ni(L₂)(H₂O)₂Cl], [Ni(L₂)(H₂O)₂(NO₃)] · H₂O, [Ni(HL₂)(H₂O)Cl₂] · EtOH and [Ni(L₃)(H₂O)₂Cl]. They have been tested in vitro for their possible cytotoxic activity against G-361 (human malignant melanoma), HOS (human osteogenic sarcoma), K-562 (human chronic myelogenous leukemia) and MCF-7 (human breast adenocarcinoma) cell lines.     

Synthesis,Structure, and Properties of Nickel(II) and Cobalt(II) Coordination Compounds with Optically Active Diaminodioxime (H2L) Derived from 3-Carene. Molecular and Crystal Structures of the [Ni(H2L)(NO3)]NO3 and [Ni(HL)]ClO4 · H2O Complexes

Nickel(II) and cobalt(II) complexes with optically active diaminodioxime (H₂L, the derivative of 3-carene) of the compositions [Ni(H₂L)NO₃]NO₃ (I), Ni(H₂L)Cl₂ (II), [Ni(HL)]ClO₄ · H₂O (III), and Co(H₂L)Cl₂ (IV), were synthesized. According to X-ray diffraction data, the structures of the paramagnetic compound I and diamagnetic complex III are ionic. In the cation of I, the distorted NiN₄O₂ octahedron is formed by the N atoms of the tetradentate cyclic ligand (H₂L molecule) and by the O atoms of NO₃ ^–; anion functioning as bidentate cyclic ligands. In the cation of III, the NiN₄ coordination unit is a distorted square formed upon coordination of the tetradentate cyclic ligand, HL^–; anion. The data of magnetochemistry and UV-Vis, IR, and Raman spectroscopy suggest that paramagnetic complexes II and IV contain a distorted octahedral polyhedron MCl₂N₄ (M = Ni, Co).     

Nicke(II) complexes of half unit,symmetric and unsymmetric Schiff base ligands

Summary The template reaction of isonitrosoacetylacetone (Hina) witho-phenylenediamine (o-phenen) in the presence of (MeCO₂)₂Ni·4H₂O in EtOH yielded three types of nickel(II) complexes (depending on the molar ratio of the reactants) formulated as L¹Ni(O₂CMe)·2H₂O (1), (L¹)₂Ni (2), and L²Ni·H₂O (3). HL¹ and H₂L² are the half unit and symmetric Schiff base ligands obtained from the (11) and (21) condensation of (Hina) with (o-phenen) respectively. The (11) molar ratio reaction of (1) with either acetylacetone (Hacac) or (Hina) in CHCl₃ led to the formation of mixed ligand complexes L¹Ni(acac)·H₂O (4) and L¹Ni(ina)·H₂O (5) whereas a similar reaction with salicylaldehyde (Hsal) produced L³Ni (6); H₂L³ is the unsymmetric Schiff base formed by the (11) condensation of the amino group in (1) with (Hsal). Analytical, spectral and magnetic moment evidence are compatible with the suggested structures of the metal complexes.This paper is a summary of the M.Sc. thesis of S. M. Imam.     

Spectral and structural studies of nickel(II) complexes of salicylaldehyde 3-azacyclothiosemicarbazones

Mononuclear nickel(II) complexes with two ONS donor thiosemicarbazone ligands {salicylaldehyde 3-hexamethyleneiminyl thiosemicarbazone [H₂L¹] and salicylaldehyde 3-tetramethyleneiminyl thiosemicarbazone [H₂L²]} have been prepared and physico-chemically characterized. IR and electronic spectra of the complexes have been obtained. The thiosemicarbazones bind to the metal as dianionic ONS donor ligands in all the complexes except in [Ni(HL¹)₂] (1). In compound 1, the ligand is coordinated as a monoanionic (HL⁻) one. The magnetic susceptibility measurements indicate that all the complexes are mononuclear and are diamagnetic. The complexes were given the formulae [Ni(HL¹)₂] (1), [NiL¹py] (2), [NiL¹α-pic] (3), [NiL¹γ-pic] · H₂O (4), [NiL²py] (5) and [NiL²γ-pic] (6). The structures of compounds 2 and 3 have been solved by single crystal X-ray crystallography and were found to be distorted square planar in geometry with coordination of azomethine nitrogen, thiolato sulfur, phenolato oxygen and pyridyl nitrogen atoms.     

Oxidative Dehydrogenation of Cu(II) Complexes with N-Aryl-N-2-hydroxybenzyl- and N-Aryl-N-2-hydroxynaphthylmethyleneamine Derivatives

The reactions of Cu²⁺, Co²⁺, and Ni²⁺ ions with N-phenyl-N-2-hydroxybenzyl- and N-phenyl-N-2-hydroxynaphthylmethyleneamine derivatives (HL ⁿ , n = 1–8) produced from the derivatives of aniline and aromatic -hydroxyaldehydes are studied. Among the ions studied, only Cu²⁺ forms stable complexes Cu(L ⁿ )₂ · 2H₂O. The structures of the synthesized compounds are studied by IR, UV, and EPR spectroscopies and differential thermal analysis. The magnetic moments of the Cu(L ⁿ )₂ · 2H₂O complexes are very small and range within 0.43–1.19 _B, depending on the ligand structure, which indicates a strong antiferromagnetic interaction between the Cu²⁺ ions. The temperature dependence of the magnetic susceptibility measured for the Cu(L³)₂ · 2H₂O complex (where HL³ is N-4-methoxyphenyl-N-2-hydroxybenzylamine) is closest to the theoretical curve calculated for the binuclear Cu(II) complexes connected by the intermolecular exchange interaction. The Cu(II) complexes with HL ⁿ are shown to undergo oxidative dehydrogenation to form the corresponding metal salicyl-aldiminates. This reaction can occur on heating in the absence of oxygen and is accompanied by the Cu²⁺ Cu⁺ transition.     

Copper(II) complexes of N(4)-substituted thiosemicarbazones derived from pyridine-2-carbaldehyde: Crystal structure of a binuclear complex

Ten copper(II) complexes {[CuL¹Cl] (1), [CuL¹NO₃]₂ (2), [CuL¹N₃]₂ · 2/3H₂O (3), [CuL¹]₂(ClO₄)₂ · 2H₂O (4), [CuL²Cl]₂ (5), [CuL²N₃] (6), [Cu(HL²)SO₄]₂ · 4H₂O (7), [Cu(HL²)₂] (ClO₄)₂ · 1/2EtOH (8), [CuL³Cl]₂ (9), [CuL³NCS] · 1/2H₂O (10)} of three NNS donor thiosemicarbazone ligands {pyridine-2-carbaldehyde-N(4)-p-methoxyphenyl thiosemicarbazone [HL¹], pyridine-2-carbaldehyde-N(4)-2-phenethyl thiosemicarbazone [HL²] and pyridine-2-carbaldehyde N(4)-(methyl), N(4)-(phenyl) thiosemicarbazone [HL³]} were synthesized and physico-chemically characterized. The crystal structure of compound 9 has been determined by X-ray diffraction studies and is found that the dimer consists of two square pyramidal Cu(II) centers linked by two chlorine atoms.     

Synthesis, spectral characterization and crystal structure of copper(II) complexes of 2-benzoylpyridine-N(4)-phenylsemicarbazone

An interesting series of nine new copper(II) complexes [Cu₂L₂(OAc)₂]·H₂O (1), [CuLNCS]·½H₂O (2), [CuLNO₃]·½H₂O (3), [Cu(HL)Cl₂]·H₂O (4), [Cu₂(HL)₂(SO₄)₂]·4H₂O (5), [CuLClO₄]·½H₂O (6), [CuLBr]·2H₂O (7), [CuL₂]·H₂O (8) and [CuLN₃]·CH₃OH (9) of 2-benzoylpyridine-N(4)-phenyl semicarbazone (HL) have been synthesized and physico-chemically characterized. The tridentate character of the semicarbazone is inferred from IR spectra. Based on the EPR studies, spin Hamiltonian and bonding parameters have been calculated. The g values, calculated for all the complexes in frozen DMF, indicate the presence of the unpaired electron in the d_x²-y² orbital. The structure of the compound, [Cu₂L₂(OAc)₂] (1a) has been resolved using single crystal X-ray diffraction studies. The crystal structure revealed monoclinic space group P2₁/n. The coordination geometry about the copper(II) in 1a is distorted square pyramidal with one pyridine nitrogen atom, the imino nitrogen, enolate oxygen and acetate oxygen in the basal plane, an acetate oxygen form adjacent moiety occupies the apical position, serving as a bridge to form a centrosymmetric dimeric structure.     

Copper(II) complexes with pyrazolyl-substituted nitronyl and imino nitroxides

It was established that the reactions of pyrazol-3-yl-substituted nitronyl nitroxide (HL¹) and pyrazol-3-yl-substituted imino nitroxide (HL³) with Cu(II) acetate lead to self-assembly of the Cu₄(OH)₂(OAc)₄(DMF)₂(L¹)₂ tetranuclear and Cu₂(OAc)₂(H₂O)₂(L³)₂ dinuclear complexes, respectively. The reaction of Cu(II) acetate with 5-ethoxycarbonyl-pyrazol-3-yl-substituted nitronyl nitroxide (HL²) gave unexpected solid Cu₂(H₂O)₂(L⁶)₂ · 2DMF, in which L⁶ is a deprotonated 5-carboxy-pyrazol-3-yl-substituted nitronyl nitroxide, formed as a result of cleavage of an ester bond in the starting HL². A similar transformation of the paramagnetic ligand was observed in the reaction of Cu(II) acetate with 5-ethoxycarbonyl-pyrazol-3-yl-substituted imino nitroxide (HL⁴). It led to the formation of Cu₂(DMF)₂(L⁷)₂, where L⁷ is deprotonated 2-(5-carboxy-1H-pyrazol-3-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole 3-oxide. An X-ray diffraction study indicated that in Cu₄(OH)₂(OAc)₄(DMF)₂(L¹)₂ and Cu₂(OAc)₂(H₂O)₂(L³)₂, the L¹ and L³ paramagnetic ligands perform the bridging cyclic tridentate function, while in Cu₂(H₂O)₂(L⁶)₂ · 2DMF and Cu₂(DMF)₂(L⁷)₂, the paramagnetic L⁶ and diamagnetic L⁷ are bridging bicyclic tetradentate ligands. The magnetic behavior of complexes with coordinated nitronyl nitroxide – Cu₄(OH)₂(OAc)₄(DMF)₂(L¹)₂ and Cu₂(H₂O)₂(L⁶)₂ · 2DMF is dictated by the dominant antiferromagnetic exchange interactions, which is confirmed by quantum-chemical data. The magnetic susceptibility of Cu₂(OAc)₂(H₂O)₂(L³)₂ reflects the competition between the antiferromagnetic and ferromagnetic components, of which the latter is due to electron coupling in the Cu(II) ← N=C–N ? O exchange channels. EPR data confirm the results received from static magnetic measurements for multispin solids.     

Complex Formation of Rhenium (V) with Benzimidazole in Acidic Media

Rhenium(V) complexes of 1H-benzimidazole (L), isolated from acidic media: (HL)₂[ReOX₅]·(H₂O) _n and [ReOL _x X _y (H₂O) _z ](H₂O) _n (HL and L are protonated and deprotonated forms of benzimidazole; X = Cl^-, Br^-) were studied by means of IR spectroscopy, ¹H NMR spectroscopy, and thermal analysis.     

Crystal Structure of Monoprotonated Ni(II) Nitrilotriacetate Tetrahydrate

A Ni(II) complex of the composition Ni(HNta) · 4H₂O (I) was synthesized. Its structure was found to consist of neutral mononuclear [Ni(HNta)(H₂O)₃] complexes and crystallization water molecules. The Ni atom has octahedral surrounding and is coordinated to tridentate-chelate HNta^2– ligand through the N atom and O atoms of two deprotonated acetate groups and through the O atoms of three water molecules. The structure of I was compared with those of the Zn(HNta) · 4H₂O and Co(HNta) · 4H₂O complexes isostructural to I. Thermogravimetric method showed that the decomposition of compound I occurs through several successive stages of dehydration, deaquation, decarboxylation, and the formation of inorganic residue.     

Complexes of Some 3d-Metal Salts with N,N-Dimethylhydrazide of 4-Nitrobenzoic Acid

The [M(HL)₂(H₂O)₂]X₂ complexes were synthesized (M = Mn(II), Co(II), Ni(II), Cu(II), Zn; X = CH₃COO^–, Cl^–, BF₄ ^–) that incorporate bidentately coordinated molecules of N,N-dimethylhydrazide of 4-nitrobenzoic acid (HL). The latter molecules chelate the metal atom through the carbonyl O atom and the N atom of dimethylamino group. The square-planar complexes of Cu and Ni with deprotonated form of a ligand with composition ML₂ were also isolated. The synthesized complexes were studied by IR, electronic and EPR spectroscopies, and by cyclic voltammetry.     

Cobalt(II), nickel(II) and copper(II) complexes of syn-2-picolyl phenyl and syn-2-quinaldyl phenyl ketoximes

Summary The syn-2-picolyl phenyl ketoxime (HL₁) and the syn-2-quinaldyl phenyl ketoxime (HL₂) give [M(HL)LX], [M(HL)₂X₂] and [ML] solid complexes (M=Co, Ni and Cu; X=Cl^–, Br^– and NO ₃ ^– which have been characterized by elemental analysis, room temperature magnetic moments and electronic and i.r. spectral measurements.     

Transition metal complexes with thiosemicarbazide-based ligands,Part II,Synthesis and characterisation of nickel(II), cobalt(II), manganese(II) and zinc(II) complexes with the pentadentate ligand, 2,6-diacetylpyridine bis(S-methylisothiosemicarbazone)

Summary The reaction of warm alcoholic solutions of acetates of Co^II, Mn^II, Zn^II and Ni^II with 2, 6-diacetylpyridine andS-methylisothiosemicarbazide hydrogen iodide yielded the complexes: [Co(H₂L)I₂]·H₂O, [Mn(H₂L)(MeOH)₂]I₂, [Zn(H₂L)(MeOH)I]I and [Ni(HL)]I, (H₂L=the pentadentate pentaaza-ligand 2, 6-diacetylpyridine bis(S-methylisothiosemicarbazone)). The reaction of methanolic solutions of [Ni(HL)]I and NH₄NCS or LiOAc.2H₂O, give [Ni(HL)]NCS and NiL, respectively. For the complexes of Co^II, Mn^II and Zn^II, a pentagonal bipyramidal configuration is proposed, with H₂L in the equatorial plane and two unidentate ligands (I and/or MeOH) in the axial positions. The complexes [Ni(HL)]X (X=I or NCS) and NiL probably have monomeric five- and dimeric six-coordinate structures, respectively, in which only the chelate ligand is involved in coordination.     

Transition Metal Complexes with the Thiosemicarbazide-based ligands. XII. Complexes of nickel(II) with benzoylacetone S-methylisothiosemicarbazone and N(1)-2-butylidene-4-oxo-4-phenyl-N(4)-salicylidene-S-methylisothiosemicarbazide

A template synthesis procedure yielded [Ni(HL¹)NH₃]I, where HL¹ is the monoanion of the terdentate ONN benzoylacetone S-methylisothiosemicarbazone ligand. The reaction of this complex with an excess of NH₄NCS, pyridine, or hydrazine resulted in the complexes [Ni(HL¹)(NH₃)NCS] and [Ni(L¹)A] (A = Py, N₂H₄). The monoanionic form of the ligand is obtained by deprotonation of the enolic form of the benzoylacetone moiety, whereas the dianion is formed by additional deprotonation of the terminal NH₂ group. Finally, the reaction of [Ni(HL¹)NH₃]I with salicyladehyde produced the NiL² complex in which L² stands for the dianion of the ONNO ligand N(1)-2-butylidene-4-oxo-4-phenyl-N(4)-salicylidene-S-methylisothiosemicarbazide. All complexes are diamagnetic and have a square-planar configuration, except for [Ni(HL¹)(NH₃)NCS], for which te data of i.r. spectra suggest a square-pyramidal structure. The electronic absorption spectra of the ethanolic solutions of all complexes are characteristic of typical square-planar coordination of nickel(II).     

Tin(IV), titanium(IV) and hafnium(IV) complexes of some aromatic Schiff bases derived from 4-aminoantipyrine

Summary Tin(IV), titanium(IV) and hafnium(IV) chloride complexes of ligands such as salicylidene-4-aminoantipyrine (HL¹), 5-chlorosalicylidene-4-aminoantipyrine (HL²), 2,4-dihydroxybenzylidene-4-aminoantipyrine (HL³), 2-hydroxy-1-naphthylidene-4-aminoantipyrine (HL⁴) and 2-hydroxyacetophenonylidene-4-aminoantipyrine (HL⁵) have been prepared and characterized. The analytical data show that tin(IV) forms only 1:1 metal complexes when reacted with HL¹, HL³ and HL⁴, whereas it forms 1:1 and 1:2 metal complexes when reacted with HL², depending on the molar ratio. HL⁵ produces only the binuclear complex SnHL⁵Cl₄(H₂O)SnCl₄. Titanium(IV) gives only one type of complex of the general formula [Ti(HL)₂Cl₂]Cl₂-2H₂O, whilst hafnium(IV) gives HfHL³Cl₄-4H₂O and Hf(L⁵)₂Cl₂.     

Synthesis and study of the structure of new 3d-metal coordination compounds with substituted 2-amino-4(5H)-ketothiophens

A series of new 3d-metal complexes based on 2-amino-3-(1-methylbenzimidazol-2-yl)-4(5H)-ketothiophen (HL¹) and 2-amino-3-(2-benzothiazolyl)-4(5H)-ketothiophen (HL²) were synthesized. Compounds of the general formulas [ML₂] and [M(HL¹)₂Cl₂] (where M = Co²⁺, Ni²⁺, Zn²⁺, Cu²⁺) were prepared by the reaction of the above mentioned ligands with the corresponding acetate (for [ML₂]) or chloride (for [M(HL¹)₂Cl₂]) salts in a methanol or a methanol–chloroform medium. The choice of the anion in the initial metal salt, as well as the selection of the ligand, is crucial for obtaining coordination compounds with a neutral or deprotonated form of the 2-amino-4(5H)-ketothiophens. Thus, in contrast to HL¹, complexes with the neutral form of HL² cannot be obtained under the same conditions. All the complexes were studied by spectroscopic methods and X-ray crystallography (for [CuL¹₂] · H₂O). The coordination polyhedron of the copper atom is formed by four nitrogen atoms from two ligand anions and the geometry of the coordination sphere is intermediate between tetrahedral and square-planar.     

Neptunium(VI) Chromate Complex with 1,2-Diammoniopropane {H3NCH2CH(NH3)CH3}[(NpO2)2(CrO4)3(H2O)] · 3H2O: Synthesis,Crystal Structure and Properties

New neptunium(VI) complex {H₃NCH₂CH(NH₃)CH₃}[(NpO₂)₂(CrO₄)₃(H₂O)] · 3H₂O is synthesized; its crystal structure is determined and IR and near-IR absorption spectra are recorded. The crystallographic data are: a = 10.805(2) Å, b = 11.238(2) Å, c = 17.615(8) Å, space group P2₁2₁2₁, Z = 4, V = 2139(1) ų, R = 0.051, wR(F ²) = 0.109. The crystal structure of the compound is built of the anionic layers of [(NpO₂)₂(CrO₄)₃(H₂O)]^2n– _n . The {H₃NCH₂CH(NH₃)CH₃}²⁺ cations and crystallization water molecules are arranged between the layers. Coordination polyhedron of two crystallographically independent Np atoms has the shape of a pentagonal bipyramid. The equatorial plane in one Np polyhedron is formed by the oxygen atoms of four chromate ions and water molecule and by the oxygen atoms of five chromate ions in the other one.     

Binuclear Copper(II) Complexes with (1R*,4S*)-1-N-Morpholino-n-menth-8-en-2-one E-oxime: Synthesis,Structure, and Magnetic Properties

Copper(II) complexes with (1R*,4S*)-1-N-morpholino-n-menth-8-en-4-one (HL), namely, [Cu₂(HL)₂Cl₄] (I) and [Cu₂(HL)LCl₃] · CH₃CN (II), were synthesized and characterized by X-ray diffraction analysis, magnetic susceptibility, and EPR methods. The complexes have binuclear structures. In compound I, the coordination polyhedron of CuCl₃N₂ is a square pyramid in planar Cu₂Cl₂ metal cycle; the exchange couplings of unpaired electrons of Cu(II) ions are weak. Complex II incorporates polyhedra of CuCl₂N₂ (flattened tetrahedron) and of CuCl₂N₂O (trigonal bipyramid). The Cu₂ClNO metal cycle is nonplanar with antiferromagnetic exchange coupling and exchange parameter –2J = 182 cm^–1. The EPR spectrum of compound I are analyzed.