Synthesis, Spectroscopic and Structural Properties of Heteropolynuclear Cyano-Bridged Complexes

Two novel cyano-bridged heteropolynuclear complexes, [Zn(mprd)₂Ni(μ-CN)₄]_n (1) and {[Cd(mprd)₂Ni(μ-CN)₄]·2H₂O}_n (2), (mprd = 4-methylpyrimidine), have been synthesized and characterized by FT-IR spectroscopy, Raman spectroscopy, thermal analyses (TG, DTG and DTA) and elemental analyses. The crystal structure of the 1 was determined by X-ray single crystal diffraction. The complex crystallizes in the monoclinic, space group C2/c. The crystal structure of 1 consists of a corrugated 2D network in which the Zn(II) and Ni(II) atoms are linked by cyanide groups. The Ni(II) atom is four coordinate with four carbon atoms in a square-planar geometry; and, the Zn(II) atom is six coordinate with four cyanide-nitrogen and two mprd-nitrogen atoms with a distorted octahedral geometry. The shifts of the cyano stretching vibration are evidence for the formation of cyano bridges. Vibration assignments are given for all the observed bands and the spectral features support the structure of the polymeric complexes.     

Square-planar nickel(II) complexes with a tridentate Schiff base and monodentate heterocycles: self-assembly to dimeric and one-dimensional array via hydrogen bonding

Two nickel(II) complexes having the general formula [Ni(bhac)L] with tridentate ONO-donor acetylacetone benzoylhydrazone (H₂bhac) and monodentate N-donor heterocycles (L=3,5-dimethylpyrazole (Hdmpz) and imidazole (Himdz)) are reported. The complexes were synthesized in ethanol media by reacting Ni(O₂CCH₃)₂·4H₂O, H₂bhac and L in 1:1:1 mole ratio and characterized by analytical, magnetic and spectroscopic methods. X-ray crystal structures of both complexes have been determined. In each complex, the metal ion is in square-planar N₂O₂ coordination geometry. In the solid state, a one-dimensional assembly of the [Ni(bhac)(Himdz)] molecules is formed via intermolecular hydrogen bonds between the imidazole N–H groups and the uncoordinated N-atoms of the deprotonated amide functionalities. On the other hand, two [Ni(bhac)(Hdmpz)] molecules are involved in a pair of complementary hydrogen bonds between the pyrazole N–H groups and the coordinated O-atoms of the deprotonated amide functionalities forming a dinuclear species.     

First macrocyclic oxamide Cu(II)–Co(II) complex: synthesis,crystal structure and magnetic properties

A oxamido-bridged binuclear complex, [Cu(L)Co(bpy)₂](ClO₄)₂·0.5C₂H₅OH·H₂O has been synthesized, and structurally and magnetically characterized, where L = 1,4,8,11- tetraazacyclotradecanne-2,3-dione and bpy = 2,2^′-bipyridine. In the complex, the copper atom from the macrocyclic oxamido-copper(II) precursor in a square-planar and cobalt atoms in a distorted octahedral environment is bridged by the oxamidate group, Cu⋯Co separation of 5.359 Å. The metal–metal separations are consistent with the sequence of decrease of the ion radius of the metal ion. The magnetic properties of the complex have been investigated. The χ_MT versus T plots is typical of antiferromagnetically coupled Cu(II)–Co(II).     

Spectroscopic and Thermal Studies of Mn(II), Fe(III), Cr(III) and Zn(II) Complexes Derived from the Ligand Resulted by the Reaction Between 4-Acetyl Pyridine and Thiosemicarbazide

Transition metal complexes of Mn(II), Fe(III), Cr(III) and Zn(II) metal ions with a general formulas [Mn(L)₂(Cl)₂]·4H₂O (I), [Fe(L)₂(Cl)₂]·Cl·6H₂O (II), [Cr(L)₂(Cl)₂]·Cl·6H₂O (III) and [Zn(L)₂(Cl)₂]·2H₂O (IV) where L = 4-acetylpyridine thiosemicarbazone, have been synthesized and interpreted using CHN elemental analysis, magnetic susceptibility measurements, molar conductance, thermal analysis and spectroscopic techniques; i.e., infrared, electronic UV/vis, ¹H-NMR and mass. The manganese(II), ferric(III), chromium(III) and zinc(II) complexes have octahedral geometry. The molar conductance measurements reveal that the Mn(II) and Zn(II) chelates are non-electrolytes but Fe(III) and Cr(III) have an electrolytic behavior. The IR spectra show that the 4-acetylpyridine thiosemicarbazone free ligand is coordinated to the metal(II) chlorides as a neutral bidentate ligand through both of the lone pair of electrons of the C=N azomethine group and C=S group. X-ray powder diffraction gives an impression that the resulting complexes are amorphous and different from the start materials. The thermogravimetric studies indicate that uncoordinated water molecules are lost in the first and second decomposition steps. The activation thermodynamic parameters E*, ΔH*, ΔS* and ΔG* are estimated from the differential thermogravimetric analysis (DTG) curves using Horowitz–Metzger (HM) and Coats–Redfern (CR) methods. The ligand and its complexes have been screened for antibacterial and antifungal activities against two bacteria; i.e., Escherichia coli (Gram −ve) and Bacillus subtilis (Gram +ve) and two fungi, i.e., tricoderma and penicillium activities).     

Stabilisation of Au and Au in the same complex molecule by a tridentate phosphinodithiolate ligand. Structures of [AuLCl] and [AuL2Au] (L = {PhP(C6H3S-2-SiMe3-3)2})

The reaction of the organometallic complex [Au^III(damp-C^I,N)Cl₂] (damp-C,N⁻ = dimethylaminomethylphenyl) with PhP(C₆H₃SH-2-SiMe₃-3) ₂, H₂L, results in cleavage of the AuC bond and the formation of [Au^IIILCl] and [Au^IL₂Au^III] complexes. The square coordination environment of gold in [AuLCl] is noticeably distorted (maximum deviation from planarity: 0.326(1) Å) by the steric requirements of the tridentate chelating ligand, but the oxidation state ‘+3’ of the metal is retained. [Au^IL₂Au^III] contains gold atoms in both square-planar (Au^III) and linear (Au^I) coordination environments. The square-planar Au^III is bound by two trans-chelated PS units, and the two remaining thiolate groups provide the linear coordination of Au^I. The Au-Au distance is 2.919(1) Å, indicative of a weak bonding interaction.     

DNA interaction and antimicrobial activity of novel tetradentate imino-oxalato mixed ligand metal complexes

Four novel DNA metalloinsertors having imino-oxalato mixed-ligands, of the composition [ML(ox)]Cl₂ (where M = Cu(II), Co(II), Ni(II) and Zn(II); ox = C₂O₄^2 − and L = N,N′-bis(4-chlorobenzylidene)benzene-1,2-diamine) were synthesized. They were fully characterized by microanalytical data, magnetic susceptibility values, molar conductivity measurements, UV–vis, IR, ¹H NMR, ¹³C NMR and EPR techniques. Their geometry was explored and found to have square-planar geometry. Electronic absorption spectroscopy, cyclic voltammetry and viscosity measurements indicate that these mixed-ligand complexes strongly bind to calf thymus DNA, presumably via an intercalation mechanism. Further, DNA cleavage efficacy of these complexes was investigated by gel electrophoresis. The complexes were found to promote the cleavage of pBR322 DNA in the presence of the reluctant, ascorbic acid. The ligand (L) and the mixed-ligand complexes were tested for their efficiency towards antimicrobial activity and their MIC data reveal that all the complexes have strong activity in comparison to the free ligand and standard drugs, ciprofloxacin and fluconazole.     

A Series of Cr<Superscript>III</Superscript> Coordination Supramolecules: Synthesis,Structure and Study of Surface Electron Behaviors

Three chromium(III) coordination supramolecules, [CrQ₂(H₂O)Cl]·H₂O 1, [Cr(Pic)₂(phen)]·NO₃·2.5H₂O 2, [Cr(ATA)(phen)]·CH₃OH·3H₂O 3 (HQ = Quinoline 2-acid, HPic = Picolinic 2-acid, H₃ATA = Ammonia triacetic acid, phen = 1,10-Phenanthroline), have been synthesized solvothermally and characterized by single-crystal X-ray diffraction, IR spectra, UV-Vis absorption spectra and elemental analysis. The surface electron behavior of chromium complexes have been studied emphatically by surface photovoltage spectroscopy (SPS). Structural analyses indicate that the three complexes are all molecular complexes with the ligands of carboxylate groups; and, they are further connected into supramolecules by hydrogen bonds and π–π interactions. The results of SPS show that there are positive photovoltage response bands within 300–800 nm, which indicate that they all possess obvious photoelectric conversion properties. Energy-band theory for semiconductors and crystal field theory have been combined to analyze and assign the SPS bands. There are three types of band-to-band transitions in the SPS of the complexes; i.e., LMCT bands for Cl → Cr, O → Cr, N → Cr. The similarities and differences between the SPS and UV-Vis absorption spectra for the three complexes were compared and reasonably explained. There was a good correlation between the SPS and UV-Vis absorption spectra.     

Two Tartrate-Pillared Coordination Polymers: Hydrothermal Preparation, Crystal Structures, Spectroscopic and Thermal Analyses of {[M2(μ-C4H4O6)2(H2O)] · 3H2O}∞ (M = Mn, Cd)

Two novel three-dimensional coordination polymers, formulated as {[M₂(μ-C₄H₄O₆)₂(H₂O)] · 3H₂O}_∞ (M = Mn for 1 and Cd for 2), have been synthesized under hydrothermal reaction condition. Both complexes were characterized by elemental analysis and IR spectroscopy. Their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by TGA-DTA methods. Compound 1 crystallizes in the monoclinic space group, P2₁, while compound 2 crystallizes the orthorhombic space group, P2₁2₁2₁. The structures are self-assembled from bifunctional tartrate and water molecules. Tartrate ligands in 1 and 2 contribute to both covalent and hydrogen bonds. Polymeric chains of 1 and 2 are composed of M(II) ions bridged by tartrate ions in O,O′ fashion. The asymmetric units of coordination polymers contain two metal centers having different coordination environments.     

Metal(II) Nicotinamide Complexes Containing Succinato,Succinate and Succinic Acid: Synthesis,Crystal Structures,Magnetic, Thermal,Antimicrobial and Fluorescent Properties

Four novel divalent transitional metal succinates (suc) with nicotinamide (nia), {[M(μ-suc)(H₂O)₂(nia)₂]·2H₂O} _n [M = Mn (1), Ni (2)], [Cu(suc)(nia)₂] (3) and [Ni(H₂O)₄(nia)₂](suc)·(H₂suc) (4), have been synthesized and characterized by elemental analyses, IR and TG-DTA. X-ray analyses of 2 and 4 reveal that they crystallize in a triclinic space group P[`1]. P\bar{1}. Complex 2 is a 1-D coordination polymer, in which the metal(II) ions exhibit an octahedral geometry with two suc, two nia and two aqua ligands. The nia ligand is N-bonded, while the suc ligand bridges the metal centres through the carboxylate groups. 4 contains the [Ni(H₂O)₄(nia)₂]²⁺ complex cations, uncoordinated suc and H₂suc species, which are connected into a two-dimensional layered structure by the combination of N–H⋯O and OW–H⋯O hydrogen bonds. This is one of the scarce examples encountered in coordination chemistry, which contains uncoordinated suc and H₂suc at the same time. The spectroscopic and structural analysis, luminescent and magnetic properties and the antimicrobial activities of the synthesized complexes were investigated.     

Synthesis and spectroscopic characterization of N-substituted thiosemicarbazone complexes

Complexation between Co(II), Ni(II), and Cu(II) with some 3,4-hexanedione bis[N-substituted thiosemicarbazones] has been investigated. The ligands release the two hydrazine hydrogens during the complex formation and act as binegative tetradentate (N₂S₂) except [Cu(H₂Hx4M)Cl₂] and [Cu(H₂Hx4Et)Cl₂]2H₂O in which the ligands behave as neutral tetradentate. The magnetic moments and electronic spectra provide information about the geometry of the complexes, which is supported by calculating the ligand field parameters for the Co(II) complexes. Most Ni(II) complexes are diamagnetic, indicative of a square-planar structure. The bands observed in Nujol are shifted to higher energies in dimethylformamide (DMF) solution, suggesting a weak interaction with the solvent. The ESR spectra of the complexes in solid and DMF solution exhibit axial symmetric g-tensor parameters with g _|>g _⊥>2.0023. The molecular parameters of [Ni(Hx4M)] have been calculated theoretically by semiempirical PM3 method. Also, the electronic transitions were calculated theoretically and found approximately similar to those recorded experimentally.     

Thermal behavior of 1,4-bis(4-trimellitimido-2-trifluoromethyl phenoxy)benzene (DIDA) solvated with polar organic solvents and properties of DIDA-based poly(amide-imide)s

Fluorinated diimide-dicarboxylic acid (DIDA, Code: IV), 1,4-bis(4-trimellitimido-2-trifluoromethylphenoxy) benzene, synthesized by reacting 1,4-bis(4-amino-2-trifluoromethyl phenoxy)benzene (I) with trimellitic anhydride in polar solvents (PSv), was found to crystallize easily in amide-type solvents, such as N-methyl-2-pyrrolidinone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), or 1,3-dimethyl-2-imidazolidinone (DMI) media, to form a series of stable crystalline solvates (III_(NMP), III_(DMAc), III_DMF), III_(DMI)) containing a certain quantity of crystalline solvent. The solvates III_(PSv) were characterized and proven by DSC, TGA, and X-ray analysis. The decomposition point temperature (T_d) was different with the type of polar solvents in III_(PSv). Elemental analysis and NMR showed that most of the III_(PSv) were formed from IV and polar solvents in the ratio of 1:2, and the solvation processes were found to be reversible. Furthermore, a series of soluble fluorinated poly(amide-imide)s (VI_a-h) were synthesized from reacting either the NMP-solvates III_(NMP) or dry/non-solvates IV with an equivalent amount of diamines by direct polycondensation using triphenyl phosphate and pyridine as condensing agents. Thermal and mechanical properties of the fluorinated VI_a-h were measured, and compared with counterparts of non-fluorinated PAI's (Code: VI′s). In comparison, the fluorinated VI_a-h poly(amide-imide)s exhibited better solubility, tensile, and thermal properties than the non-fluorinated VI′s.     

One-Dimensional Cobalt(II) and Zinc(II) Succinato Coordination Polymers with Nicotinamide: Synthesis, Structural, Spectroscopic, Fluorescent and Thermal Properties

Cobalt(II) and zinc(II) succinato (suc) coordination polymers with nicotinamide (nia), {[Co(μ-suc)(H₂O)₂(nia)₂] · 2H₂O} _n (1) and {[Zn(μ-suc)(H₂O)₂(nia)₂] · 2H₂O} _n (2) have been synthesized and characterized by elemental analyses, magnetic moments, IR and TG-DTA. Single-crystal X-ray analyses of 1 and 2 reveal that these complexes are isostructural and crystallize in triclinic space group Complexes 1 and 2 are 1-D coordination polymers, in which the metal(II) ions exhibit an octahedral geometry with two suc, two nia and two aqua ligands. The nia ligand is N-bonded, while the suc ligand bridges the metal centers through the carboxylate groups. The 1D chains are further assembled to form 3D networks by strong N–H···O and OW–H···O hydrogen bonds. IR spectra confirm the coordination modes of both suc and nia ligands, while TG-DTA data are in agreement with the crystal structures. Fluorescent analysis in the solid state shows that all complexes display intraligand (π–π*) emissions of nia.     

Sonochemical Synthesis of One-Dimensional Nano-structure of Three-Dimensional Cadmium(II) Coordination Polymer

Nano-wires and nano-rods of a new three-dimensional cadmium(II) coordination polymer, {[Cd₃(3-pyc)₄(NCS)₂(H₂O)₄]·2H₂O} _n (1); 3-Hpyc = 3-pyridinecarboxilic acid, were synthesized by a sonochemical method in two different concetrations. The morphology of the nano-structures depend strongly on reactants’ concentration. The new nano-structures were characterized by scanning electron microscopy, X-ray powder diffraction, elemental analyses and IR spectroscopy. Compound 1 was structurally characterized by single-crystal X-ray diffraction and is a three-dimensional polymer with two types of Cd(II) coordination environments.     

Bis[4-(methylthio)phenylmethyleneaminophenyl] disulfide, 2-[4-(methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole,and its nickel(II) and cobalt(II) complexes: Synthesis,adsorption on gold surface and electrochemical characterization

2-[4-(Methylthio)phenyl]-2,3-dihydro-1,3-benzothiazole (1) and bis[4-(methylthio)phenylmethylene-aminophenyl] disulfide (2) were synthesized. Novel coordination compounds of Ni(II) and Co(II) with 2-[4-(methylthio)phenylmethyleneamino]thiophenol, M(1)₂ (M=Co (3); M=Ni (4)), were prepared by reacting 1 with M(OAc)₂·6H₂O or MCl₂·6H₂O in EtOH solution. The structure of 2 was proved by X-ray crystallography. Electrochemical behavior of 1–4 in CH₃CN solution and at the surface of a gold electrode was studied by cyclic voltammetry. The modification of the electrode by ligand 1 and its complexes with Ni²⁺ and Co²⁺ is described in detail. Two procedures were used to obtain a self-assembled monolayer of a metal complex on the gold surface: the adsorption of prepared coordination compound 3 or 4 on the electrode and the initial modification of the electrode with ligand 1 followed by the formation of a coordination complex between the ligand adsorbed on the electrode and a metal salt occurring in solution. On the basis of the electrochemical data, it was found that the structure of complexes formed on the surface differs from that of the complexes produced in solution.     

Syntheses, Characterization and Crystal Structures of 1D and 2D Organotin Polymers Containing 3-Methyladipic Acid Ligand

Four new organotin (IV) complexes of two types [(R₂Sn)₂(C₇H₁₀O₄)(μ₃-O)] _n (R = Me: 1; nBu: 2; and {(R₃Sn)₂[C₅H₁₀(COO)₂]} _n (R = Me: 3; nBu: 4) have been synthesized by the reaction of 3-methyladipic acid with the corresponding R₃SnCl (R = Me, nBu) under two different experimental conditions. All the complexes were characterized by elemental analysis, FT-IR, and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy. Except for 2, all of the complexes were also characterized by X-ray crystallography. The structural analyzes show that complex 1 is a 1D infinite chain polymer and forms a 2D organotin framework through intermolecular C–H···O interactions and weak Sn···O interactions. Complexes 3 and 4 are 2D network polymers in which 3-methyladipic acid acts as a tetra dentate ligand coordinated to the trialkyltin (IV) ion.     

Rigid and Flexible Lanthanide Complexes with an Infinite Ln–O–Ln Framework: Synthesis,Structure and Properties

Abstract  

A series of new lanthanide coordination polymers, Ln(pydc)(Hglu) (Ln = Nd(1), Pr(2); H₂glu = glutaric acid; 2,5-H₂pydc = 2,5-pyridine dicarboxylic acid), have been synthesized hydrothermally from the self-assembly of the lanthanide ions (Ln³⁺) with rigid 2,5-pyridine dicarboxylic acid and flexible glutaric acid. They were characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Structural analyses reveal that both of the complexes were crystallized in monoclinic space group P2₁/c and have intricate 3D net-structures, which contain an infinite 1D Ln–O–Ln chain structure. In addition, the phase purities of the bulk samples were identified by X-ray powder diffraction. The thermogravimetric analysis of 1 is discussed in detail.     

Syntheses, Structures, and Luminescent Properties of Two Novel Coordination Polymers with Mixed Ligands

Two novel metal–organic coordination polymers {[Pb₂(MIP)₂(BDC)₂]·H₂O} _n 1 and [Cd(MIP)(NDC)] _n 2 [MIP = 2-(3-methoxyphenyl)-1H-imidazo [4,5-f] [1, 10] phenanthroline, BDC = terephthalic acid, NDC = naphthalene-1,4-dicarboxylic acid] were obtained from hydrothermal reaction and characterized by elemental analysis, thermogravimetric (TG) analysis, infrared spectrum (IR) and single-crystal X-ray diffraction. The coordination polymers crystallize in triclinic, space group P-1 with a = 1.0335(2), b = 1.4224(3), c = 1.8156(4) nm, β = 106.088(3)° for complex 1 and the complex 2 crystallizes in monoclinic, space group P2(1)/n with a = 1.2562(8), b = 1.4800(9), c = 1.3723(8) nm, β = 97.257(1)°, respectively. The metal ions Pb(II) are located in [:PbN2O4] pentagonal bipyramidal geometry in complex 1. The metal ions Cd(II) in complex 2 act as distorted octahedral geometry, being surrounded by four carboxylate oxygen atoms from three NDC ligands and two donor nitrogen atoms from one MIP molecule. Moreover, there are hydrogen bonds in the two complexes, and it is noteworthy that the existence of hydrogen bonds and π–π interactions reinforce the structural stability of the title complexes, which have been proved by TG analysis. The luminescent properties for the ligand MIP, NDC and complex 2 are also discussed in detail.     

Seven Coordinated Metal Complexes derived from (3-Carboxymethoxy-Naphthalen-2-yloxy)-Acetic Acid and Coordination Polymers

A design principle for seven coordinated metal carboxylate complexes and coordination polymers of Mn(II), Cd(II) and Na(I) derived from (3-carboxymethoxy-naphthalen-2-yloxy)-acetic acid (LH2) is presented. The complexes/coordination polymer [Mn(L)(H₂O)₃]·3H₂O (1), [{Cd(L)(H₂O)₂}·H₂O]_n (2); [Cd(L)(py)₃]·3H₂O (3) have metal ions in pentagonal bipyramid environments (py = pyridine). The coordination polymer [{Cd(L)(H₂O)₂}·H₂O]_n (2) may be considered to be the self-assembly of hexacoordinated [Cd(L)(H₂O)₂] units; it reacts with pyridine to form mono-nuclear complex 3. Depending on the reaction conditions, Ni-coordination polymers of L adopt different compositions. From the reaction carried out with NiCl₂ and NaOH in quinoline and water, a hetero bimetallic coordination polymer; namely, [[NaL(H₂O)]₂Ni(H₂O)₄]_n (4) is obtained. A similar reaction in pyridine-water solvent led to [{Ni(L)(py)₃}.py]_n (5). The coordination polymer 5 has pyridine in its interstices held by C–H···π interactions.     

Synthesis and Characterization of Tripodal Oxy-Schiff base (2,4,6-Tris(4-Carboxymethylenephenylimino-4′-formylphenoxy)-1,3,5-triazine) and the Thermal and Magnetic Properties of its Fe(III)/Cr(III) Complexes

Eight new trinuclear Fe(III)/Cr(III) complexes involving tetradentate (N₂O₂) and pentadentate (N₃O₂) Schiff bases of (salenH₂), (salophenH₂), (saldetaH₂) and (salpyrH₂) with 2,4,6-tris(4-carboxymethylenephenylimino-4′-formylphenoxy)-1,3,5-triazine were synthesized. The structure of ligand and complexes were identified using elemental and thermal analysis, magnetic susceptibility, and LC–MS, ICP-AES, ¹H NMR and FT-IR spectral data. All complexes are tripodal–trinuclear. The complexes are low-spin (S = 1/2) distorted octahedral salen- or salophen-capped Fe(III), high-spin (S = 5/2) distorted octahedral saldeta- or salpyr-capped Fe(III) and distorted octahedral (S = 3/2) salen-, salophen-, saldeta- or salpyr-capped Cr(III).     

Crystal structure and chirality of adenosine-5′-diphosphate coordination complex

The first neutral coordination complex of adenosine-5′-diphosphate (ADP) with transition metal Cu(II) ion, [Cu(phen)(H₂ADP)(NO₃)]·H₂O (ADP–Cu) (ADP = adenosine-5′-diphosphate, phen = 1, 10-phenanthroline monohydrate) has been synthesized and investigated by X-ray single-crystal diffraction method. Based on its crystal structure and supramolecular assembly analysis, the molecular and supramolecular chirality of ADP–Cu was studied comprehensively by liquid- and solid-state circular dichroism (CD) spectroscopy. It is the first example of the study about the chirality and supramolecular chirality for polyphosphate nucleotide coordination complex.