The preparation and characterisation of hetero- and homobimetallic complexes containing bridging naphthalene-1,8-dithiolato ligands

Homo- and heterobimetallic complexes of the form [(PPh(3))(2)(mu(2)-1,8-S(2)-nap){ML(n)}] (in which (1,8-S(2)-nap)=naphtho-1,8-dithiolate and {ML(n)}={PtCl(2)} (1), {PtClMe} (2), {PtClPh} (3), {PtMe(2)} (4), {PtIMe(3)} (5) and {Mo(CO)(4)} (6)) were obtained by the addition of [PtCl(2)(NCPh)(2)], [PtClMe(cod)] (cod=1,5-cyclooctadiene), [PtClPh(cod)], [PtMe(2)(cod)], [{PtIMe(3)}(4)] and [Mo(CO)(4)(nbd)] (nbd=norbornadiene), respectively, to [Pt(PPh(3))(2)(1,8-S(2)-nap)]. Synthesis of cationic complexes was achieved by the addition of one or two equivalents of a halide abstractor, Ag[BF(4)] or Ag[ClO(4)], to [{Pt(mu-Cl)(mu-eta(2):eta(1)-C(3)H(5))}(4)], [{Pd(mu-Cl)(eta(3)-C(3)H(5))}(2)], [{IrCl(mu-Cl)(eta(5)-C(5)Me(5))}(2)] (in which C(5)Me(5)=Cp*=1,2,3,4,5-pentamethylcyclopentadienyl), [{RhCl(mu-Cl)(eta(5)-C(5)Me(5))}(2)], [PtCl(2)(PMe(2)Ph)(2)] and [{Rh(mu-Cl)(cod)}(2)] to give the appropriate coordinatively unsaturated species that, upon treatment with [(PPh(3))(2)Pt(1,8-S(2)-nap)], gave complexes of the form [(PPh(3))(2)(mu(2)-1,8-S(2)-nap){ML(n)}][X] (in which {ML(n)}[X]={Pt(eta(3)-C(3)H(5))}[ClO(4)] (7), {Pd(eta(3)-C(3)H(5))}[ClO(4)] (8), {IrCl(eta(5)-C(5)Me(5))}[ClO(4)] (9), {RhCl(eta(5)-C(5)Me(5))}[BF(4)] (10), {Pt(PMe(2)Ph)(2)}[ClO(4)](2) (11), {Rh(cod)}[ClO(4)] (12); the carbonyl complex {Rh(CO)(2)}[ClO(4)] (13) was formed by bubbling gaseous CO through a solution of 12. In all cases the naphtho-1,8-dithiolate ligand acts as a bridge between two metal centres to give a four-membered PtMS(2) ring (M=transition metal). All compounds were characterised spectroscopically. The X-ray structures of 5, 6, 7, 8, 10 and 12 reveal a binuclear PtMS(2) core with PtM distances ranging from 2.9630(8)-3.438(1) A for 8 and 5, respectively. The napS(2) mean plane is tilted with respect to the PtP(2)S(2) coordination plane, with dihedral angles in the range 49.7-76.1 degrees and the degree of tilting being related to the PtM distance and the coordination number of M. The sum of the Pt(1)coordination plane/napS(2) angle, a, and the Pt(1)coordination plane/M(2)coordination plane angle, b, a+b, is close to 120 degrees in nearly all cases. This suggests that electronic effects play a significant role in these binuclear systems.     

Synthesis and characterization of Zr(IV) and Y(III) complexes with monocyclopentadienyl ligands containing an additional site tethered by a coordinating 2,6-pyridine bridge. X-ray crystal structures of the zirconium complexes

A new monocyclopentadienyl ligand containing an additional site tethered by a coordinating 2,6-pyridine unit has been prepared, rac-2-(1′-hydroxy-2′,2′-dimethylpropyl)-6-(1″,1″-dimethyl-cyclopentadienylmethyl) pyridine dilithium salt, LLi₂ (rac-4) that is analogous to the ligands present in CGC. After reacting the dilithium salt of the ligand with ZrCl₄ in a molar ratio of 1:1 in THF the complex LZrCl₂·THF (rac-5) was obtained which forms an insoluble oligomeric species after the loss of THF upon purification. From the mater liquor two crystalline species of the formula LHZrCl₃ (rac-6) and LH₂ZrCl₄·THF (rac-7) were isolated, whose X-ray crystal structures are reported. The reaction of LLi₂ with Y(OTf)₃ afforded the probably dimeric species [LYOTf]₂ (rac-8) from which the complex [LY(CH₂Si(CH₃)₃)]₂ (rac-9) was obtained after reaction with LiCH₂Si(CH₃)₃.     

Chiral cyanide-bridged 1D Fe~Ⅲ-Mn~Ⅲ heterobimetallic chains: Synthesis, structures and magnetic properties

Two couples of enantiomerically pure chiral cyano-bridged heterobimetallic one-dimensional (1D) chain complexes: [Mn((R,R)-Salphen)Fe(Tp)(CN)3]n (1) and [Mn((S,S)-Salphen)Te(Tp)(CN)3]n (2) (Salphen = N,N’-1,2-diphenylethylenebis (salicylideneiminato) dianion, Tp = tris(pyrazolyl) hydroborate), [Mn((R,R)-Salphen)Fe(Tp*)(CN)3·2H2O]n (3) and [Mn((S,S)-Salphen)Fe(Tp*)(CN)3·2H2O]n (4) (Tp* = hydridotris (3,5-dimethylpyrazol-1-yl) borate), have been successfully synthesized by the reactions of MnIII schiff-base complexes with the tricyanometalate building block, [(LTp)Fe(CN)3]- (LTp = Tp or Tp*). All complexes are made up of neutral cyano-bridged zigzag double chains with (-Fe-C≡N-Mn-N≡C-)n as the repeating unit. Circular dichroism (CD) spectra confirm the enantiomeric nature of the optically active complexes. Magnetic studies demonstrate that ferromagnetic interactions are operative in these complexes. The ferromagnetic couplings become weak in the chains with the bending of the Mn-N≡C angles.     

Synthesis,spectroscopic studies and crystal structures of two new vanadium complexes of 2-benzoylpyridine containing hydrazone ligands

The reaction of VO(acac)₂ with 2-benzoylpyridine substituted aroylhydrazones is studied. Oxovanadium(IV) and (V) complexes are obtained, indicating the binding of ligands to the metal ion through the imine nitrogen, enolate oxygen and pyridyl nitrogen. The oxovanadium(IV) compound [VOL¹(OCH₃)] · 0.14H₂O (1a) gets oxidized to dioxovanadium(V) species [VO₂L¹] (1b) upon crystal formation. The crystal structures of the ligand and the two vanadium complexes are reported. Single crystal X-ray diffraction studies of the compound [VO(HL²)(μ₂-O)]₂ (2) revealed a centrosymmetric dimer.     

Substituted cyclopentadienylchromium(III) complexes containing neutral donor ligands. Synthesis, crystal structures and reactivity in ethylene polymerization

Lithium derivatives of substituted cyclopentadiene ligands reacted with CrCl₃(THF)₃ in THF solution to afford homodinuclear complexes of the type [{(η⁵-RCp)CrCl(μ-Cl) }₂] [R=SiMe₃ (1), CH₂C(Me)CH₂ (2)]. Complex 1 reacts with pyrazole (C₃H₄N₂) to yield the mononuclear half-sandwich complex [(η⁵-Me₃SiCp)CrCl₂(pyrazole)] (3). The similar complex [Cp*CrCl₂(pyrazole)] (4) was synthesised by reaction of [{Cp*CrCl(μ-Cl)}₂] with pyrazole. Complex 2 reacts with bidentate ligands to give binuclear complexes of the type [{(η⁵-CH₂C(Me)CH₂Cp)CrCl₂ }₂(μ-L-L)] [L-L=Ph₂PCH₂CH₂PPh₂ (5), trans-Ph₂P(O)CHCHP(O)Ph₂ (6)]. All complexes were structurally characterised by X-ray diffraction. After reaction with methylaluminoxane these complexes are active in the polymerization of ethylene. At 25 °C and 4 bar of ethylene, complex 3 yields polyethylene with a bimodal molecular weight distribution centred at 155,000 and 2000 g/mol. Complex 4 shows similar activity, yielding only the low molecular weight fraction. On the other hand, the binuclear complexes 5 and 6 under the same conditions were three times more active than mononuclear complexes. The melting point of the polymers indicates the formation of linear polyethylene.     

Synthesis and characterization of nickel(II) maltolate complexes containing ancillary bisphosphine ligands

Cationic nickel(II) complexes containing chelating O,O′-donor maltolate or ethyl maltolate ligands in conjunction with bidentate bisphosphine ligands Ph₂P(CH₂) _n PPh₂ were prepared by a one-pot reaction starting from nickel(II) acetate, bisphosphine, maltol (or ethyl maltol), and trimethylamine, and isolated as their tetraphenylborate salts. An X-ray structure determination of [Ni(maltolate)(Ph₂PCH₂CH₂PPh₂)]BPh₄ shows that the maltolate ligand binds asymmetrically to the (slightly distorted) square-planar nickel(II) center. The simplicity of the synthetic method was extended to the synthesis of the known platinum(II) maltolate complex [Pt(maltolate)(PPh₃)₂]BPh₄ which was obtained in high purity.     

Synthesis and crystal structures of Group 6 metal carbonyl complexes containing S-rich bis(pyrazol-1-yl)methane ligands

The reaction of 3(5)-methylthio-5(3)-phenylpyrazole with dibromomethane under phase-transfer catalytic conditions only affords a new ligand, bis(3-phenyl-5-methylthiopyrazol-1-yl)methane. However, the reaction of 3(5)-methylthio-5(3)-p-methoxyphenylpyrazole or 3(5)-methylthio-5(3)-tert-butylpyrazole with dibromomethane under the same conditions yields three isomers, respectively, indicating that the substituents significantly affect the steric and electronic properties of pyrazole ring during the formation of ligands. Treatment of these potential polydentate ligands with M(CO)₆ (M=Cr, Mo or W) under UV irradiation at room temperature affords (NN)M(CO)₄ derivatives, in which some complexes contain asymmetric substituted bis(pyrazol-1-yl)methane ligands. The X-ray crystal structure analyses indicate that the sulfur atoms in these complexes do not take part in the coordination to the metal centers, and S-rich bis(pyrazol-1-yl)methanes actually act as bidentate chelating ligands by two nitrogen atoms. It is also interesting that in order to reduce the repulsion of methyl groups with carbonyls, the methyl groups in these complexes are oriented away from the metal centers.     

Synthesis,characterization, and X-ray crystal structures of metal complexes with new Schiff-base ligands and their antibacterial activities

Two new potentially hexadentate Schiff bases, [H₂L¹] and [H₂L²], were prepared by condensation of 2-(3-(2-aminophenoxy)naphthalen-2-yloxy)benzenamine with 3,5-di-tert-butyl-2-hydroxy benzaldehyde and o-vanillin, respectively. Reaction of these ligands with cobalt(II) chloride, copper(II) perchlorate, and zinc(II) nitrate gave complexes ML. The ligands and their complexes have been characterized by a variety of physico-chemical techniques. The solid and solution state investigations show that the complexes are neutral. Molecular structures of [CuL¹], [CoL¹]?·?C₇H₈, and [ZnL²]?·?CH₃CN, which have been determined by single-crystal X-ray diffraction, indicate that [CuL¹] and [ZnL²]?·?CH₃CN display distorted square planar and distorted trigonal-bipyramidal geometry, respectively; the geometry around cobalt in [CoL¹]?·?C₇H₈ is almost exactly between trigonal bipyramidal and square pyramidal. The synthesized ligands and their complexes were screened for their antibacterial activities against eight bacterial strains and the ligands and complexes have antibacterial effects. The most effective ones are [CuL²] against Proteus vulgaris, Serratia marcescens, Staphylococcus subtilis, [H²L¹] against S. subtilis, and [H₂L²] against S. subtilis.     

Thio-azo proligands based on 5,6-derivatives-1,10-phenanthroline and their use for iron(II) complexes: Synthesis,characterization and crystal structures

The preparation and characterization of 5,6-substituted-1,10-phenanthrolines, phdtos = 5,6-bistosyl-1,10-phenanthroline (1) and phdbt = 5,6-dibenzyltiol-1,10-phenanthroline (2) are described. The synthesis of (1) was achieved in good yield via the corresponding dihydroxide and 2 was obtained by cross-coupling reaction of 5,6-dibromo-1,10-phenanthroline and benzylthiol mediated by a palladium catalytic system in refluxing toluene (120 °C). These phenanthroline derivatives were used as ligands to afford [Fe^II(phdtos)₃](PF₆)₂ (5) and [Fe^II(phdbt)₃](PF₆)₂ (6) complexes.     

Synthesis, spectral properties, crystal structures and antimicrobial effects of copper(II) pyridinecarboxylate adducts with chelating ligands

The reaction of an ethanolic solution of copper(II) pyridinecarboxylates CuX₂·nH₂O (where X is nicotinate (nic) (n=0) or isonicotinate (isonic) (n=4)) with ethylenediamine (en) in a molar ratio of 1:2 lead to the isolation of solid tetragonally distorted octahedral complexes of the type [Cu(en)₂(H₂O)₂]X₂·nH₂O (n=1 for nic; n=0 for isonic). The analogous reaction of CuX₂·nH₂O with diethylenetriamine (dien) in a molar ratio of 1:1 leads to the formation of square-pyramidal pentacoordinated complexes of the type [CuX(dien)(H₂O)]X. On the other hand, the reaction of equimolar quantities of copper(II) nitrate and dien with nicotinate anions (equimolar quantities of pyridinecarboxylic acid and NaOH) in ethanolic solutions gives a solid monomeric complex [Cu(nic)(NO₃)dien)(H₂O)]·H₂O in which the coordination polyhedron around the Cu(II) atom is a (4+1+1) distorted tetragonal bipyramid. Based on the molecular structure the electronic and IR spectra are discussed. Moreover, the results of the quantitative determination of antimicrobial activity of the isonic complexes [Cu(isonic)₂(H₂O)₄], [Cu(en)₂(H₂O)₂](isonic)₂, [Cu(isonic)(dien)(H₂O)](isonic), as well as isonicotinic acid, ethylenediamine and diethylenetriamine alone are discussed.     

Two Cd(II) complexes derived from mercapto-triazole ligands: syntheses,crystal structures,and luminescent properties

Two cadmium complexes, {[Cd(a-ptt)(ptt)]·H₂O} _n (1) and [Cd(a-Hmtt)₂(SO₄)H₂O]·CH₃OH (2), have been prepared based on 4-amino-3-(4-pyridine)-5-mercapto-1,2,4-triazole (a-Hptt) and 4-amino-3-methyl-5-mercapto-1,2,4-triazole (a-Hmtt), respectively. In 1, amino-triazole ligand a-Hptt can partly be deaminated and transformed into 3-(4-pyridine)-5-mercapto-triazole (Hptt) under hydrothermal conditions. X-ray diffraction analysis reveals that 1 exhibits an unusual 2-D lampshade-type layer structure in which the amino ligand a-ptt and the deamination ligand ptt display exo-tridentate bridging and bidentate bridging, respectively. Complex 2 is mononuclear and further assembled into a 3-D supramolecular architecture via non-covalent interactions. Complexes 1 and 2 were characterized by elemental analyses, IR, and thermogravimetric analyses. Furthermore, solid-state luminescent properties of 1 and 2 have also been investigated.     

Synthesis and properties of oligomers of iron-manganese carbonyl complexes with bridging disulfido ligands

The reactions of activated CpFeMn(CO)₇1a and Cp*FeMn(CO)₇1b, Cp=C₅Me₅ with thiirane yielded the new dimeric mixed metal disulfido complexes: [CpFeMn(CO)₅(μ₃-S₂)]₂ (2) and [Cp*FeMn(CO)₅(μ₃-S₂)]₂ (3). Compounds 2 and 3 both contain two triply bridging disulfido ligands. When heated at 40 °C, compound 2 was transformed into a trimeric compound Cp₃Fe₃Mn₃(CO)₁₅(μ₃-S₂)(μ₄-S₂)₂, 4. Compound 4 contains three disulfido ligands, each of which has a different bridging coordination mode in the six atom metal cluster. There are three inequivalent CpFe(CO)₂ groupings linked to a central Mn₃(S₂)₃ core by the disulfido ligands. In solution, compound 4 exhibits a dynamical intramolecular exchange process that interconverts two of the three CpFe(CO)₂ groups on the NMR timescale.     

Syntheses,structures and hydrolytic properties of copper(II) complexes of asymmetrically N-functionalised 1,4,7-triazacyclononane ligands

A series of new asymmetrically N-substituted derivatives of the 1,4,7-triazacyclononane (tacn) macrocycle have been prepared from the common precursor 1,4,7-triazatricyclo[5.2.1.0^4,10]decane: 1-ethyl-4-isopropyl-1,4,7-triazacyclononane (L1), 1-isopropyl-4-propyl-1,4,7-triazacyclononane (L2), 1-(3-aminopropyl)-4-benzyl-7-isopropyl-1,4,7-triazacyclononane (L3), 1-benzyl-4-isopropyl-1,4,7-triazacyclononane (L4) and 1,4-bis(3-aminopropyl)-7-isopropyl-1,4,7-triazacyclononane (L5). The corresponding monomeric copper(II) complexes were synthesised and were found to be of composition: [Cu(L1)Cl₂] · 1/2 H₂O (C1), [Cu(L4)Cl₂] · 4H₂O (C2), [Cu(L3)(MeCN)](ClO₄)₂ (C3), [Cu(L5)](ClO₄)₂ · MeCN · NaClO₄ (C4) and [Cu(L2)Cl₂] · 1/2 H₂O (C5). The X-ray crystal structures of each complex revealed a distorted square-pyramidal copper(II) geometry, with the nitrogen donors on the ligands occupying 3 (C1 and C2), 4 (C3) or 5 (C4) coordination sites on the Cu(II) centre. The metal complexes were tested for the ability to hydrolytically cleave phosphate esters at near physiological conditions, using the model phosphodiester, bis(p-nitrophenyl)phosphate (BNPP). The observed rate constants for BNPP cleavage followed the order k_C1 ≈ k_C2 > k_C5 ? k_C3 > k_C4, confirming that tacn-type Cu(II) complexes efficiently accelerate phosphate ester hydrolysis by being able to bind phosphate esters and also form the nucleophile necessary to carry out intramolecular cleavage. Complexes C1 and C2, featuring asymmetrically disubstituted ligands, exhibited rate constants of the same order of magnitude as those reported for the Cu(II) complexes of symmetrically tri-N-alkylated tacn ligands (k ∼ 1.5 × 10⁻⁵ s⁻¹).     

Synthesis and solid-state structural characterisation of Pt(II,IV) bromide complexes containing bidentate organothiomethylpyridine heteroleptic ligands

A convenient synthetic method for the preparation of organothiomethylpyridine ligands 2-(RSCH₂)C₅H₄N (R = Ph (L¹), Me (L²)), 2-MeS–6-Me-C₅H₃N (L³), and 2-MeS–4-Me-C₅H₃N (L⁴) via the initial lithiation of substituted 2-picolines followed by the nucleophilic reaction with a diorganyldisulfide is described. The complexes [PtBr₂L] (L = L¹–L⁴) have been prepared in good to high yields as yellow solids with low solubility in organic solvents. The solid state structures of the complexes have been determined, showing the spatial arrangement of the complexes to depend significantly upon varying substituents within the ligand. The complexes undergo oxidation by bromine to form the tetravalent complexes [PtBr₄(L)] (L = L¹–L⁴). The solid state structures of [PtBr₄(L²)] and [PtBr₄(L₄)] have been determined, and shown to be monomeric with the ligand chelating the platinum centre.     

Syntheses,crystal structures,and photoluminescence of two Cd(II) complexes with simple ligands

Two cadmium complexes, {[Cd₂(2,5-tda)₂(ip)₄]·4H₂O}_n (1) and {[Cd₂(4,4′-obb)₂(ip)₂·H₂O]·H₂O}_n (2) (2,5-tda?=?thiophene-2,5-dicarboxylic acid, 4,4′-obb?=?4,4′-oxybisbenzoic acid, ip?=?1H-imidazo[4,5-f][1, 10]-phenanthroline), were synthesized and characterized by IR, elemental analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. X-ray analysis revealed that 1 is a dinuclear complex with the 2,5-tda anion connecting two Cd ions in a μ₁-η¹:η⁰/μ₁-η¹:η⁰ coordination mode. Each dinuclear complex is further connected with neighboring complexes via hydrogen-bonding interactions. Compound 2 displays a 2-D layer structure with opened windows occupied by crystallographic water molecules. The layers are further packed via hydrogen-bonding interactions. Luminescent properties for 1 and 2 are also investigated in the solid state at room temperature.     

New N-pyrazole, P-phosphinite hybrid ligands and corresponding Rh(I) complexes: X-ray crystal structures of complexes with [Rh, N, P-phosphinite, Cl, (CO)] core

Two new N-pyrazole, P-phosphinite hybrid ligands 3-(3,5-dimethyl-1H-pyrazol-1-yl)propyldiphenylphosphinite (L³) and 2-(3,5-diphenyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L⁴) are presented. The reactivity of these ligands and two other ligands reported in the literature (3,5-dimethyl-1H-pyrazol-1-yl)methyldiphenylphosphinite (L¹) and 2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyldiphenylphosphinite (L²) towards [RhCl(CO)₂]₂ (1) have been studied and complexes [RhCl(CO)L] (L = L² (2), L³ (3) and L⁴ (4)) have been obtained. For L¹ only decomposition products have been achieved. All complexes were fully characterised by analytical and spectroscopic methods and the resolution of the crystalline structure of complexes 2 and 3 by single-crystal X-ray diffraction are also presented. In these complexes, the ligands are coordinated via κ²(N,P) to Rh(I), forming metallocycles of seven (2 and 4) or eight (3) members and finish its coordination with a carbonyl monoxide and a trans-chlorine to phosphorus atom. In both complexes, weak intermolecular interactions are present. NMR studies of complexes 2-4 show the chain N-(CH₂)_x-O becomes rigid and the protons diastereotopic.     

Synthesis,spectral characterization,properties and structures of copper(I) complexes containing novel bidentate iminopyridine ligands

Four new ligands, (4-methyl-phenyl)-pyridin-2-ylmethylene-amine (A), (2,3-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (B), (2,4-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (C) and (2,5-dimethyl-phenyl)-pyridin-2-ylmethylene-amine (D), and their corresponding copper(I) complexes, [Cu(A)₂]ClO₄ (1a), [Cu(B)₂]ClO₄ (1b), [Cu(C)₂]ClO₄ (1c), [Cu(D)₂]ClO₄ (1d), [Cu(A)(PPh₃)₂]ClO₄ (2a), [Cu(B)(PPh₃)₂]ClO₄ (2b), [Cu(C)(PPh₃)₂]ClO₄ (2c) and [Cu(D)(PPh₃)₂]ClO₄ (2d), have been synthesized and characterized by CHN analyses, ¹H and ¹³C NMR, IR and UV–Vis spectroscopy. The crystal structures of [Cu(B)₂]ClO₄ (1b), [Cu(C)₂]ClO₄ (1c) and [Cu(A)(PPh₃)₂]ClO₄ · 1/2CH₃CN (2a) were determined from single crystal X-ray diffraction. The coordination polyhedron about the copper(I) center in the three complexes is best described as a distorted tetrahedron. A quasireversible redox behavior is observed for the complexes.     

Syntheses, characterization, X-ray crystal structures and emission properties of five oxovanadium(V) complexes with pyridyl/pyrimidyl-pyrazole derived ditopic ligands

Four oxovanadium(V) complexes of heterocycle based ditopic ligands PyPzOAP (N-[amino(pyridin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid), PyPzOAPz (N-[amino(pyrazin-2-yl)methylidene]-5-methyl-1-(pyridin-2-yl)-1H-pyrazole-3-carbohydrazonic acid), PymPzOAP (N-[amino(pyridin-2-yl)methylidene]-1-(4,6-dimethylpyrimidin-2-yl)-5-methyl-1H-pyrazole-3-carbohydrazonic acid) and PyPzCAP (5-methyl-1-(pyridin-2-yl)-N′-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide) and a binuclear (di-μ-oxo) oxovanadium(V) complex of the ligand PymPzCAP (1-(4,6-dimethylpyrimidin-2-yl)-5-methyl-N′-[1-(pyridin-2-yl)ethylidene]-1H-pyrazole-3-carbohydrazide) have been investigated. The ligands act as uninegative NNO tridentates donors for the VO₂⁺ ion exhibiting their monotopicity. The ligands show varying emission properties due to the presence of fluophoric groups like 1-(2-pyridyl)pyrazole or 1-(2-pyrimidyl)pyrazole. The vanadium(V) complexes show fluorescence quenching with respect to the used ligands to a varying extent. The complexes were characterized by UV-Vis, IR, cyclic voltammetry and X-ray crystallography.     

Synthesis and crystal structure of nickel(II) complexes with bis(5-methyl-2-thiophenemethyl)(2-pyridylmethyl)amine

A series of nickel(II) complexes having the (Me-Tp)₂PMA ligand ((Me-Tp)₂PMA = bis(5-methyl-2-thiophenemethyl)(2-pyridylmethyl)amine) with nitrates (1), chlorides (2), and perchlorates (3) as anions were synthesized and isolated. All these complexes were successfully characterized by physicochemical methods including X-ray crystallographic analysis. In complex 1, the ligand binds in a bidentate N₂ fashion, whereas in the cases of 2 and 3 the ligand binds in the tridentate N₂S form. The coordination geometry around the nickel(II) atoms in these complexes is distorted octahedral.