Platinum(II) complexes with bidentate iminopyridine ligands: Synthesis,spectral characterization,properties and structural analysis

Four platinum(II) complexes, [PtCl₂L] (L = (4-fluorophenyl)pyridin-2-ylmethylene-amine, 1; (4-chlorophenyl)pyridin-2-ylmethyleneamine, 2; (4-bromophenyl)pyridin-2-ylmethyleneamine, 3 and (4-iodophenyl)pyridin-2-ylmethyleneamine, 4) have been synthesized and characterized by CHN analysis, IR and UV–Vis spectroscopy. The crystal structures of 1 and 2 were determined using single crystal X-ray diffraction. The coordination polyhedron about the platinum (II) center in the complexes is best described as distorted square planar. The complexes undergo stacking to form a zigzag Pt···Pt···Pt chain containing both short (3.57(7) Å in 1 and 3.62(8) Å in 2) and long (5.16(7) Å in 1 and 5.41(9) Å in 2) Pt···Pt separations through the crystal. The compounds absorb moderately in the visible region, owing to a charge-transfer-to-diimine electronic transition. The redox potentials are approximately insensitive to the substituents on the phenyl ring of the ligands.     

Covalent and ionic Cu(II) complexes with cyclam and substituted benzoato ligands: structural,thermal, redox and mesomorphic properties

A covalent mononuclear complex, [Cu(p–HOC₆H₄COO)₂(cyclam)] (1), and two ionic mononuclear complexes, [Cu(cyclam)(H₂O)₂](p–CH₃OC₆H₄COO)₂ (2) and [Cu(cyclam)(H₂O)₂](p–CH₃(CH₂)₁₅OC₆H₄COO)₂·H₂O (3), were formed from reaction of cyclam with [Cu₂(p–HOC₆H₄COO)₄(H₂O)₂], [Cu₂(p–CH₃OC₆H₄COO)₄(H₂O)₂] and [Cu₂(p-CH₃(CH₂)₁₅OC₆H₄COO)₄(H₂O)₂], respectively. These complexes were isolated as purple crystals with molecular structures showing distorted octahedral N₄O₂ geometry. Complexes 1 and 2 were irreversibly reduced to Cu(I) and oxidized to Cu(III), while 3 was redox inactive. Complex 2 reacted with N-(hexadecyl)isonicotinamide (L) to form [Cu(cyclam)(L)₂](p–CH₃OC₆H₄COO)₂ (4). These complexes were thermally stable (T_dec > 200 °C for 1–3 and 174 °C for 4). Complexes 3 and 4 behaved as ionic liquids (melting temperatures lower than 100 °C) and exhibited mesomorphism.     

Synthesis, structural characterization and thermal properties of three copper(II) complexes based on aryl hydrazide ligands

The thiosemicarbazide and hydrazide Cu(II) complexes, [Cu₃L₂¹(py)₄Cl₂] (1), [Cu(HL²)py] (2) and [Cu(HL³)py] (3), (H₂L¹ = 1-picolinoylthiosemicarbazide, H₃L² = N′-(2-hydroxybenzylidene)-3-hydroxy-2-naphthohydrazide, H₃L³ = 2-hydroxy-N′-((2-hydroxy-naphthalen-1-yl)methylene)benzohydrazide) have been prepared and characterized through physicochemical and spectroscopic methods as well as X-ray crystallography. Complex 1 has a centrosymmetric structure with –N–N– bridged Cu₃ skeleton. Neighboring molecules are linked into a 3D supermolecular framework by π–π stacking interactions, N–H···Cl and C–H···Cl hydrogen bonds. Complexes 2 and 3 have similar planar structures but different dimers formed by concomitant Cu···N and Cu···O interactions, respectively. Solvent accessible voids with a volume of 391 ?³ are included in the structure of complex 2, indicating that this complex is a potential host candidate. Thermogravimetric analysis shows that the three complexes are stable up to 100 °C.     

Copper(II)-methylmalonate complexes with unidentate N-donor ligands: Syntheses,structural characterization and magnetic properties

Two new methylmalonate-bridged copper(II) complexes with the formulas [Cu(3-Ipy)(Memal)(H₂O)] (1) and [Cu(2,4′-bpy)(Memal)(H₂O)] · 3H₂O (2) [Memal = methylmalonate dianion, 3-Ipy = 3-iodopyridine, 2,4′-bpy = 2,4′-bipyridine] have been synthesized and characterized by X-ray diffraction. Both compounds crystallize in the monoclinic space group P2₁/n and Z = 4, with unit cell parameters a = 8.5874(13) Å, b = 7.1738(14) Å, c = 19.093(5) Å, β = 99.509(15)° in 1 and a = 17.375(4) Å, b = 7.3305(14) Å, c = 14.247(3) Å, β = 111.409(15)° in 2. The structures of 1 and 2 consist of zigzag chains of anti-syn carboxylate-bridged copper(II) ions running along the b direction. The pyridine-like ligands occupy one equatorial position of the copper environment avoiding the formation of the sheet-like arrangement observed in previously reported Memal complexes. The chains are grouped together in hydrophilic layers through hydrogen bonds and the layers are pillared through the 3-Ipy (1) and 2,4′-bpy (2) ligands which are stacked through π–π interactions involving alternatively aromatic ligands from two adjacent chains. Magnetic susceptibility measurements of both compounds in the temperature range 2–290 K show the occurrence of intrachain ferromagnetic interactions between the copper(II) ions [J = +2.66(2) cm^?1 (1) and J = +2.62(2) cm^?1 (2)].     

Zinc(II) and mercury(II) complexes with Schiff bases: syntheses,spectral, and structural characterization

Schiff bases o-vanilidene-1-aminobenzene (HL¹) and o-vanilidene-2-methyl-1-aminobenzene (HL²) lead to the formation of mono- and bis-[(Cl)Zn(L¹)] (1), [(Cl)Zn(L²)] (2), [(Cl)Hg(L¹)] (3), [(Cl)Hg(L²)] (4), [Zn(L¹)₂] (5), [Zn(L²)₂] (6), [Hg(L¹)₂] (7), and [Hg(L²)₂] (8) complexes by reactions of zinc(II) and mercury(II) chlorides in different mole ratio(s). Complexes 1–8 have been characterized by elemental analyses (Zn, Hg, C, H, Cl, and N), melting point and spectral (IR, ¹H-NMR), PXRD, molar conductivity measurement, and TGA. Conductivity measurements suggest non-electrolytes. Structural compositions have been assigned by mass spectral studies. Four-coordinate geometry may be assigned to these complexes tentatively. Structural study reveals that in 1–4 two metal centers are held together by two bridged (μ₂-Cl) chlorides, whereas 5–8 contain two bidentate Schiff-base ligands around one metal-producing monomers.     

Three new thiocyanato-bridged complexes of cadmium(II): syntheses,X-ray crystal structures and thermal properties

Three new thiocyanato-bridged polymers of cadmium(II), [Cd(me₄dpt)(SCN)₂] _n (1) [me₄dpt = 3,3′-iminobis(N,N-dimethylpropylamine], [Cd(me₂tn)(SCN)₂] _n (2) (me₂tn = N,N′-dimethyl-1,3-propanediamine) and [{amphyH} {Cd(SCN)₃}] _n (3) (ampyH = 4-aminopyridinium cation), have been synthesized and their molecular structures determined through X-ray crystallography. In Complex 1 each square pyramidal mononuclear fragment is H-bonded (N ? H…S) to form a 1D supramolecular chain. Complex 2 is a 1D coordination polymer in which each distorted octahedral cadmium(II) ion is linked with the four bridging thiocyanates and one diamine. The structure of 3 reveals anionic [Cd(SCN)₃]^? zigzag chains arranged in an approximately hexagonal array with the 4-aminopyridinum cations occupying triangular channels. Each chain is H-bonded (N?H…N) to form a 2D supramolecular network. Upon heating, 1 and 2 melt and transform to transparent solid masses at ambient temperature over a few days. On scratching, these turn to a fine powder. This phenomenon is repeatable. Complex 3 upon heating loses a 4-aminopyridine molecule and transforms to [H][Cd(SCN)₃] at ??195°C.     

Synthesis, characterization, biological and thermal studies of Cu(II) complexes of salen and tetrahedrosalen ligands

A series of mononuclear salen type copper(II) complexes, [CuLⁿ] (n = 1–4), and their corresponding tetrahydrosalen complexes, [CuH₂Lⁿ] (n = 1,2) were prepared by the reaction of the N₂O₂ ligands with Cu(II) ion in ethanol, where H₂L¹ = N,N-bis(3,5-di-tert-butylsalicylidene)-2,2-dimethyle-1,3-diaminopropan, H₂L² = N,N-bis(3,5-di-tert-butylsalicylidene)-1,2-diaminopropane, H₂L³ = N,N-bis(4-methoxysalicylidene)-2,2-dimethyle-1,3-diaminopropan; H₂L⁴ = N,N-bis(4-methoxysalicylidene)-1,2-diaminopropane, H₂[H₂L¹] = N,N-bis(2-hydroxyl-3,5-di-tert-butylphenyl)-2,2-dimethyle-1,3-diaminopropan and H₂[H₂L²] = N,N-bis(2-hydroxyl-3,5-di-tert-butylphenyl)-1,2-diaminopropane. The prepared ligands and complexes were characterized by the combination of IR, UV-Vis, NMR (as far as possible), elemental and thermal analyses. All prepared compounds were also evaluated for their antibacterial (Escherichia coli and Staphylococcus aureus) and antifungal (Candida albicans) activities by the disc diffusion method. The compounds were found have no remarkable antimicrobial activities.     

Synthesis,structures and thermal properties of Cu(II) and Ni(II) complexes containing diethylenetriamine and nicotinate ligands

The syntheses and crystal structures of four new divalent transition metal complexes of the types [Cu₂(dien)₂(nic)](ClO₄)₃ · MeOH (nic = anion of nicotinic acid; dien = diethylenetriamine), 1; [Cu(dien)(nic)]₂(nic)₂, 2; [Cu(dien)(nic)]₂(BF₄)₂ · 2MeOH, 3 and [Ni(dien)(nic)(H₂O)]₄(NO₃)₄ · 2MeOH, 4, are reported, which were prepared by the reactions of diethylenetriamine and nicotinic acid with Cu(ClO₄)₂ · 6H₂O, Cu(OAc)₂ · H₂O, Cu(BF₄)₂ · 6H₂O and Ni(NO₃)₂ · 6H₂O in MeOH, respectively. These complexes were characterized by single-crystal X-ray diffraction method and elemental analyses. In the cation of complex 1, one nicotinate ligand bridges two Cu(II) metal centers through the pyridyl nitrogen atom and one of the carboxylate oxygen atoms. The cations of complexes 2 and 3 form the twelve-membered metallocycles, involving two Cu(II) ions that are bridged by two nicotinate ligands. The cation of complex 4 forms a tetranuclear cage with the four Ni(II) metal centers bridged by four nicotinate ligands and each Ni(II) metal center adopts the distorted octahedral geometry. Their thermal properties have been investigated by using differential scanning calorimetry (DSC) and thermogravimetric analyses (TGA).     

Synthesis and magnetic properties of new binuclear Cu(II) complexes with tridentate azomethine ligands

New binuclear copper complexes of tridentate azomethine ligands with various combinations of N, O, and S donor centers were prepared by various procedures, including template synthesis. The magnetochemical data obtained for the range 2-300 K suggest the occurrence of antiferromagnetic coupling in most of these chelates. The only exception is the complex containing N-tosyl and N-ethyl donor fragments, in which the ferromagnetic exchange is observed.     

Mononuclear and binuclear lanthanide(III) complexes: syntheses,structural, photophysical and thermal properties

Six new Ln(III) complexes viz., [Gd(tptz)(SCN)₃(CH₃OH)₂OH₂]·CH₃OH (1), [Eu(tptz)(SCN)₃(CH₃OH)₂OH₂]·CH₃OH (2), [Tb(tptz)(SCN)₃(OH₂)₃]₄ (3), [Gd(tptz)(OBz)₂(μ-OBz)OH₂]₂·2H₂O (4), [OH₂(OBz)₂(tptz)Eu₁(μ-OBz)₂Eu₂(tptz)(OBz)₂OH₂]·CH₃OH·7H₂O (5), and {[Tb₁(tptz)(OBz)₂(μ-OBz)]₂·[Tb₂(tptz)(OBz)₃CH₃OH]₂}·2CH₃OH·4H₂O (6) (Ln = Gd, Eu, Tb; tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine; BzONa = sodium benzoate), have been synthesized and characterized by physicochemical methods including single-crystal X-ray crystallography. The X-ray studies demonstrate that 1–3 are mononuclear, whereas 4–6 are binuclear. The photophysical properties of 1–6 have been studied with ultraviolet absorption and emission spectral studies. Their thermal properties have been studied by thermogravimetric (TG) and derivative thermogravimetric analysis (DTG), demonstrating that the final product after decomposition was Ln₂O₃ for all these complexes.     

Co(II) and Ni(II) complexes with imidazole-containing ligands: Synthesis,structural characterization,and magnetic property

Hydrothermal reaction of Co(II) salt with 1,4-di(1-imidazolyl)benzene (L¹) and 4,4’-oxydiphthalic acid (H₄OA) yields a new complex [Co₃(HOA)₂(L¹)₄(H₂O)₄] (I). [Ni(L²)₂SO₄] · 0.5H₂O (II) can be obtained via the hydrothermal reaction of NiSO₄ · 6H₂O with 1,3-di(1H-imidazol-4-yl)benzene (L²). Complexes I and II have been characterized by single-crystal and powder X-ray diffraction (CIF files CCDC nos. 1019291 (I) and 1019292 (II)), IR, elemental, and thermogravimetric analyses. Complex I exhibits the uninodal six-connected 3D pcu framework structure of I with (4¹² · 6³) topology; Complex II consists of the uninodal four-connected 2D sql (4⁴ · 6²) networks. In addition, magnetic property of I was investigated.     

Mono-, di-, and oligonuclear complexes of Cu(II) ions and p-hydroquinone ligands: syntheses, electrochemical properties, and magnetic behavior

Four highly soluble square-planar Cu(II) and Ni(II) complexes of siloxy-salens (2SiCu, 2SiNi) and hydroxy-salens (2Cu, 2Ni) have been synthesized. An X-ray crystal structure analysis was performed on 2SiCu, 2SiNi, and 2Ni. The compounds have been investigated by cyclic voltammetry, UV-vis-NIR spectroelectrochemistry, and EPR spectroscopy. According to these results, the monooxidized species [2SiCu]+ and [2SiNi]+ are to be classified as Robin-Day class II and III systems, respectively. Magnetic measurements on the dinuclear (PMDTA)Cu(II) complex 1Cu2 x (PF6)2 with deprotonated 1,4-dihydroxy-2,5-bis(pyrazol-1-yl)-benzene (1) linker revealed antiferromagnetic coupling between the two Cu(II) ions thereby resulting in an isolated dimer compound. Coordination polymers [1Cu]n(H2O)(2n) of Cu(II) ions and bridging p-hydroquinone linkers were obtained from CuSO4 x 5 H2O and 1,4-dihydroxy-2,5-bis(pyrazol-1-yl)benzene. X-ray crystallography revealed linear chains running along the crystallographic a-direction and stacked along the b-axis. Within these chains, the Cu(II) ions are coordinated by two pyrazolyl nitrogen atoms and two p-hydroquinone oxygen atoms in a square-planar fashion.     

Synthesis,characterization, and antioxidant activities of three Cu(II) complexes with Schiff-base ligands

Cu(II) complexes of three bis(pyrrol-2-yl-methyleneamine) ligands were synthesized and characterized by elemental analyses, mass spectra, and IR spectra. X-ray diffraction analysis shows that [CuL³]₂ is a dinuclear complex with an extremely distorted square-planar geometry. Furthermore, the antioxidant activities of the compounds have been investigated. The electrochemical properties of the Cu(II) complexes have also been studied by cyclic voltammetry. The Cu(II) complexes show similar superoxide dismutase (SOD) activity compared with that of the native Cu, Zn-SOD.     

Synthesis and characterization of Cu(I) and Cu(II) complexes containing ketiminate ligands

A series of Cu(I) and Cu(II) complexes containing substituted ketiminate ligands was synthesized. Reaction of CuCl₂ with 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] in toluene generated dark green solid of Cu[OC(Me)CHC(Me)N(Ar)]₂ (1). Similarly, Cu(I) complex, {Cu[OC(Me)CHC(Me)N(Ar)]Li[OC(Me)CHC(Me)N(Ar)]}₂ (2) was synthesized by reacting 2 equiv. of Li[OC(Me)CHC(Me)N(Ar)] with CuCl in toluene at room temperature for 12 h. While the reaction of CuCl with Li[OC(Me)CHC(Me)N(Ar)] in the presence of triphenylphosphine in THF solution at room temperature, a three-coordinated Cu[OC(Me)CHC(Me)N(Ar)](PPh₃) (3) can be isolated in high yield. Replacing the PPh₃ of 3 with N-heterocarbene (NHC) generates Cu[OC(Me)CHC(Me)N(Ar)](NHC) (4) in low yield. Complexes 2, 3, and 4 were characterized by ¹H and ¹³C NMR spectroscopies and all molecules were structurally characterized by X-ray diffractometry. Two coordination modes of ketiminate ligands were found in the molecular structure of 2, one of which is copper-coordinated terminal ketiminates and the other is lithium-copper-coordinated bridging ketiminates.     

Synthesis and structural characterization of nickel(II) hexaazamacrotetracyclic complexes with phthalate ligands

Highly crosslinked polymeric networks formed by cyclodextrins (CD) have recently been shown to be highly versatile nanosponge systems, being for instance very efficient both for drug delivery and for pollutants removal. Here we report some molecular simulation results for dry and hydrated CD nanosponge models aimed to study their swelling behavior. We also report simulation results about the water mobility in these systems in terms of the calculated diffusion coefficient of “free” and of “bound” water molecules confined within the nanosponge cavities. Furthermore, we also suggest the presence of surface-constrained water molecules temporarily bound to the network surface but eventually set free in the bulk.     

Polydentate Schiff-base ligands and their Cd(II) and Cu(II) metal complexes: synthesis,characterization, biological activity and electrochemical properties

Synthesis, characterization, microbiological activity and electrochemical properties of the Schiff-base ligands A¹–A⁵ and their Cd(II) and Cu(II) metal complexes are reported. The ligands and their complexes have been characterized by elemental analysis, FT–IR, UV–Vis, ¹H- and ¹³C-NMR, mass spectra, magnetic susceptibility and conductance measurements. In the complexes, all the ligands are bidentate, the oxygen in the ortho position and azomethine nitrogen atoms of the ligands coordinate to the metal ions. The keto-enol tautomeric forms of the Schiff-base ligands A¹–A⁵ have been investigated in polar and non-polar organic solvents. Antimicrobial activity of the ligands and metal complexes were tested using the disc diffusion method and the chosen strains include Bacillus megaterium and Candida tropicalis. The electrochemical properties of the ligands A¹–A⁵ and their Cu(II) metal complexes have been investigated at different scan rates (100–500?mV?s^?1) in DMSO.     

Solvothermal syntheses and crystal structures of new Cu(II) complexes with phenylsuccinic acid

Five new Cu(II) complexes [Cu(psa)(phen)] · 3H₂O (1), [Cu(psa)(2bpy)] · 0.5H₂O (2), [Cu(psa)(2bpy)(H₂O)] · 3H₂O (3), [Cu(psa)(4bpy)] · H₂O (4), and [Cu(psa)_0.5(N₃)(2bpy)] (5) (H₂psa = phenylsuccinic acid, phen = 1,10-phenanthroline, 2bpy = 2,2′-bipyridine, and 4bpy = 4,4′-bipyridine) were obtained under solvothermal conditions and characterized by single-crystal X-ray diffraction. Complexes 2 and 3 were formed by one-pot reaction. In complex 2, Cu(II) ion is four-coordinated and locates at a slightly distorted square center. In complex 3, the coordinated water molecule occupies the axial site of Cu(II) ion forming a tetragonal pyramid geometry. Complexes 1 and 3 are of 1D chain structures, and extended into 2D supramolecular network by hydrogen bonds. Complex 2 is of zipper structure, and further assembled into 2D supramolecular network by hydrogen bonds and π–π stacking interactions. Complex 4 is a 3D CdSO₄-like structure with twofold interpenetration, while complex 5 is a dinuclear compound. The different structures of complexes 1–5 can be attributed to using the auxiliary ligands, indicating an important role of the auxiliary ligands in assembly and structure of the title complexes.     

Mono- and dinuclear Zn(II) complexes of Schiff-base ligands: syntheses,characterization and studies of photoluminescence

Six Schiff-bases HL¹-HL⁴, L⁵ and L⁶ [HL¹ = 2,6-bis[1-(2-aminoethyl)pyrolidine-iminomethyl]-4-methyl-phenol, HL² = 2,6-bis[1-(2-aminoethyl)piperidine-iminomethyl]-4-methyl-phenol, HL³ = N-{1-(2-aminoethyl)pyrolidine}salicylideneimine, HL⁴ = N-{1-(2-aminoethyl)piperidine}salicylideneimine, L⁵ = 2-benzoyl pyridine-N-{1-(2-aminoethyl)pyrolidine}, L⁶ = 2-benzoylpyridine-N-{1-(2-aminoethyl)piperidine}] have been synthesized and characterized. Zn(II) complexes of those ligands have been prepared by conventional sequential route as well as by template synthesis. The same complexes are obtained from the two routes as evident from routine physicochemical characterizations. All the Schiff-bases exhibit photoluminescence originating from intraligand (π–π*) transitions. Metal mediated fluorescence enhancement is observed on complexation of HL¹-HL⁴ with Zn(II), whereas metal mediated fluorescence quenching occurs in Zn(II) complexes of L⁵ and L⁶.     

Mononuclear and binuclear sandwich copper(II) complexes with poly(pyrazolyl)borate ligands: syntheses, structures and properties

A series of Cu(II) complexes Cu(2)[micro-pz](2)[HB(pz)(3)](2) (1), Cu[H(2)B(pz)(2)](2) (2), Cu[HB(pz)(3)](2) (3), Cu[HB(pz(Me2))(3)](2) (4), Cu[B(pz)(4)](2) (5) (pz=pyrazole), have been synthesized and characterized by elemental analysis, IR, UV-vis, X-ray diffraction, thermal analysis and theoretical analysis. The IR spectra give the Cu-N vibration modes at 322, 366, 344, 387, and 380 cm(-1) in complexes 1-5, respectively. The UV spectra show all the complexes have same UV absorption at 232 nm; there is another band at 332 nm for complexes 1, 2 and 4, while for complexes 3 and 5, the bands are at 272 and 308 nm, respectively. Complex 1 has a binuclear structure in which two pyrazole ligands bridge two Cu-Tp units. In 2-5, the Cu(II) centers are coordinated with dihydrobis(pyrazolyl)borate (Bp), hydrotris(pyrazolyl)borate (Tp), hydrotris(3,5-Me2pyrazolyl)borate (Tp'), tetrakis(pyrazolyl)borate (Tkp) respectively to form a mononuclear structure. The results of thermal analysis for complexes 1-5 are discussed too.