Electrospray ionization mass spectral 3nvestigations on multi-nuclear complexes of an azacryptand

The electrospray ionization (ES) mass spectrum of a trisodium azacryptate derived from a template reaction of sodium 2,6-diformyl-4-methylphenolate (sdmp) with 2,2′,2″-triaminoethylamine (tren) was investigated and compared with those by fast atom bombardment (FAB), atmospheric pressure chemical ionization (APCI) and electronic ionization (EI) methods. Dinuclear transition metal complexes of this hexaimine macrobicyclic ligand obtained by transmetallation were also studied by ES mass spectra. An [M₂L]⁺ species has been observed for divalent metal complexes, and an [MLH]⁺ species for a trivalent metal complex. The possible mechanism of the fragmentation process is discussed.     

Synthesis and spectral studies of gold(III) complexes with guanidine derivatives

New trivalent gold (d⁸ electronic configuration) halide complexes with guanidino–pyrimidines have been synthesized and delineated. The complexes have been identified and characterized by elemental analysis, u.v.–vis. electronic absorption spectra, i.r. oscillation spectra and by ¹H-n.m.r. and ¹³C-n.m.r. spectra. All substituted guanidine ligands in these chelates form part of a six-membered pseudo-heterocyclic ring where the nitrogen atoms of the guanidine group and the nitrogen atom of pyrimidine, piperidine or the morpholine heterocyclic ring bond to the metal.     

Template synthesis of metal complexes of 7,16-disubstituted dibenzo[b,i][l,4,8,11]tetraaza[14]annulenes from malonic aldehyde acetals

Metal complexes of 7,16-dialkyl- and 7,16-diphenyldibenzo[b,i][1,4,8,11]tetraaza [14]annulenes have been prepared by template condensation of o-phenylenediaraine with 2-alkyl- and 2-phenyl-1,1,3,3-tetraethoxypropanes, respectively, in the presence of divalent metals salts. The effects of substituents in the meso-position and of the metal ion on the nature of the electronic and vibrational spectra of these metal complexes are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 103–105, January, 1989.     

Structural and spectral studies of di-2-pyridyl ketone 3-piperidyl- and 3-hexamethyleneiminylthiosemicarbazone and their cobalt(II), nickel(II) and copper(II) complexes

Cobalt(II), nickel(II) and copper(II) complexes of di-2-pyridyl ketone 3-piperidyl- and 3-hexamethyleneiminyl-thiosemicarbazones (HDPypip and HDPyhexim, respectively) have been prepared and characterized by physical and spectral methods. Use of 1:2 thiosemicarbazone-to-metal chloride molar ratios in the preparation of the complexes has produced both mononuclear and polynuclear species for the three metal ions. Crystal structures of the HDPypip, HDPyhexim and [Ni(DPyhexim)Cl] have been determined and aid the assignments of the i.r., n.m.r., u.v.–vis. n.i.r. and e.s.r. spectra for the various complexes.     

Molecular modeling of the influence of complex formation on the conformation and electronic absorption spectra of crown-containing styryl dyes

The conformation and electronic absorption spectra of crown-containing styryl dyes and their complexes with metal salts have been calculated. The long-wave absorption bands have been assigned. It was shown that the observed large hypsochromic shift of the absorption spectra during the formation of complexes of the cis-form of the dyes under consideration with alkaline earth ions is due to a change in the conformation of the chromophore and the resultant approximate prohibition with respect to symmetry of the long-wave electronic transition.Institute of Chemical Physics, Russian Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 34, No. 2, pp. 39–45, March–April, 1993.     

EPR of copper(II) chloride complexes with diphosphine dioxides

Stepwise formation of copper(ll) chloride complexes with diphosphine dioxides has been studied using paramagnetic resonance. It was found that in complexes with a copper:ligand composition of 11 substituents have little effect on parameters of the anisotropic EPR spectra. The spectra of complexes with a metal:ligand composition of 12 are considerably more sensitive to the introduction of substituents; this is explained by sterically dependent differences in the structure of the complexes. The possibility of trisligand complexes being formed is evidently largely determined by the size of the groups on the phosphorus atoms.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 362–368, February, 1991.     

Multinuclear Magnetic Resonance Study of Zinc(II) and Cadmium(II) Complexing with Isothiocyanate

A study of zinc(II) and cadmium(II) complexes with isothiocyanate ion has been completed, using a low-temperature, multinuclear magnetic resonance technique that permits the observation of separate resonance signals for bound and free ligand, and Cd(II) metal ion. The Zn²⁺–NCS^– complexes were studied by ¹H, ¹³C, and ¹⁵N NMR spectroscopy. In the ¹H spectra, the intensity of the coordinated water signal, corresponding to a Zn(II) hydration number of six in the absence of NCS^–, decreases dramatically as this anion is added, indicating the complexing process involves more than a simple 1:1 ligand replacement. The ¹³C and ¹⁵N NMR spectra reveal signals for four species, most reasonably assigned to a series of tetrahedrally coordinated Zn²⁺–NCS^– complexes. In the Cd²⁺–NCS^– solution spectra, the ¹³C and ¹⁵N signals for four complexes also are observed and they are three line patterns, corresponding to a doublet from ¹¹³Cd J-coupling, and a dominant central peak, resulting from bonding to magnetically inactive Cd isotopes. The ¹¹³Cd spectra, showing signals for four complexes, correlate well in all respects with the ¹³C and ¹⁵N results, including coupling in specific cases. The spectral results for both metal ions reflect binding at the nitrogen atom of NCS^–, with the complexes changing from an octahedral to a tetrahedral configuration when doing so. Confirming evidence for these conclusions also was provided by several infrared measurements of these metal–ion systems.     

Transition metal (disubstituted phenylazo)-barbituric and thiobarbituric acid complexes

Summary Disubstituted phenylazo-barbituric and thiobarbituric acid complexes derived from Co^II, Ni^II and Cu^II salts have been prepared. Electronic spectra and magnetic susceptibility measurements prove that the cobalt and nickel complexes have high-spin octahedral and square planar configurations, respectively. The copper-barbituric complexes have distorted octahedral geometry with a possible Cu–Cu interaction, whereas the corresponding thiobarbiturate complexes have square pyramidal distorted octahedral and tetragonal geometries. The room temperature e.s.r. spectra of the copper complexes show anisotropy with axial symmetry in tetragonal geometry, ground state as a result of Cu–Cu interaction. This dimeric structure disappears in DMSO solution. The intradimer super-exchange interaction is temperature dependent indicating a change of the geometry. In some complexes, the azo group coordinates to the metal, in others it does not. The denticity of the ligands has been determined.     

Synthesis and relaxivity of polyamide paramagnetic metal complexes for magnetic resonance imaging

A new class of paramagnetic macromolecular magnetic resonance imaging contrast agents has been developed. Eight new polyamide ligands were synthesized by copolymerization of ethylenediaminetetraacetic acid dianhydride or diethylenetriaminepentaacetic acid dianhydride and diamine monomers. Their gadolinium(III), manganese(II) and iron(III) complexes were also synthesized. All polyamide ligands and metal complexes were characterized by ¹H nuclear magnetic resonance, infrared spectra and elemental analyses. Relaxivity studies showed that the polyamide paramagnetic metal complexes had obviously higher relaxation effectiveness as compared to corresponding simple monomeric paramagnetic metal complexes.     

Thermal stability of phosphorylated cellulose modified with various transition metals

Complexes of cellulose phosphate with transition metals such as chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, molybdenum, silver, cadmium and mercury have been characterized by reflectance UV-visible spectra. The thermal behaviour of cellulose and the metal complexes of cellulose phosphate in air has been studied by differential thermal analysis and thermogravimetry from ambient temperature to 750°C. From the resulting data, various thermodynamic parameters for different stages of thermal degradation can be obtained following the method of Broido. The activation energies for decomposition of cellulose and metal complexes of cellulose phosphatewere found to kJ mol⁻¹.Pyrolysis-mass spectrometric studies of metal complexes of cellulose phosphate using soft ionization modes such as field ionization and field desorption give very low abundances of volatile products in the spectra compared with the yields with untreated cellulose. The IR and reflectance UV-visible spectra of the pyrolysis residues of metal complexes of cellulose phosphate indicate that dehydration takes place and the metal complexes are stable up to 250°C. At higher temperatures, a compound containing carbonyl groups is formed. A mechanism for the thermal degradation of metal complexes of cellulose phosphate is proposed which explains the generation of reduced amounts of smoke.Scanning electron microscopic studies of cellulose phosphate and its transition metal complexes showed that the fibrillar sites have mostly reacted and throw light on the morphological changes of treated cellulose in the thermal degradation range. The observed effects are of interest with respect to the flame-proofing of cellulose.     

Investigation on DNA Binding and Photo-Cleavage Properties of Water-Soluble Porphyrin and Metalloporphyrins

A water-soluble porphyrin, tetrakis[4-(trimethylammonium)phenyl]porphyrin (TAPP), and its metal complexes with Zn(II), (ZnTAPP), have been synthesized and characterized by elemental analyses and u.v.-vis. spectra. The binding of the two complexes with calf thymus DNA has been investigated by absorption spectra, luminescence titrations, and viscosity measurements. The changes of the u.v.-vis. absorption spectra during the titration of these porphyrins with calf thymus DNA revealed a large bathochromic shift (upto 8–12 nm) and a hypochromicity of the porphyrins soret bands. The intensity of the fluorescence spectra of these porphyrins was enhanced. The cytotoxicity of the series of porphyrins TAPP and MTAPP [M = Zn(II), Cu(II), Fe(III), Co(III), Ni(II), Mn(III)] complexes was determined for Madin–Darby Canine Kindney (MDCK) cells and Vero cells with the method of cell culture, and were evaluated as anti-virus activity for influenza virus type A (H3N2), B and Herpes simplex virus type-1 (HSV-1, strain SM44), type-2 (HSV-2, strain 333) in vitro. Among the complexes evaluated, inhibited viral cytopathogenicity at lower concentrations that were found cytotoxic for the MDCK cells. Differences were observed in the 50% effective doses (based on inhibition of viral cytopathogenicity) of these complexes for a number of influenza viruses type A, B, and HSV-1, HSV-2 strains. It was found that CoTAPP displayed good inhibitory action against the virus in vitro.     

The infrared spectra (3500-140 cm−1) of the 2,2'-bipyridine, 2-aminomethylpyridine and ethylenediamine adducts and the sodium tris-compounds of cobalt(II), nickel(II) and zinc(II) acetylacetonates

Summary The M(acac)₂B and NaM(acac)₃ complexes (M = Coll, Ni^ll orZn^ll; acac=acetylacetonateanion; B=2,2=bipyridine, 2-aminomethylpyridine or ethylenediamine) have been prepared and their i.r. spectra determined over the 3500-140 cm^–1 range. Complete band assignments have been made on a comparative basis, with the effects of ligand substitution and metal ion substitution being considered. Bands in the i.r. spectra of the complexes which are associated with 2,2-bipyridine, 2-aminomethylpyridine and ethylenediamine arc in excellent agreement with values previously established for these ligand and metal-ligand vibrations, in related complexes. Band assignments for acetylacetonate anion and metal-acetylacetonate vibrations substantiate those made in certain of the previously published papers. The method of assignment adopted has allowed the complete assignment of bands in the i.r. spectra of the metal complexes.     

Structural and spectral studies of di-2-pyridyl ketone N(4)-methyl- and N(4)-dimethylthiosemicarbazone and their metal complexes

Cobalt(II), nickel(II) and copper(II) complexes of di-2-pyridyl ketone N(4)-methyl- and N(4)-dimethylthiosemicarbazone have been prepared and characterized by physical and spectral methods. Use of different ligand-to-metal chloride molar ratios in the preparation of the complexes has produced both mononuclear and polynuclear species for the three metal ions. Crystal structures of the uncomplexed di-2-pyridyl ketone N(4)-methylthiosemicarbazone and a nickel(II) complex, di-2-pyridyl ketone N(4)-dimethylthiosemicarbazone, have been determined and aid the assignments of the i.r., n.m.r., u.v.–vis.–n.i.r. and e.s.r. spectra.     

Electrochemical, catalytic and antimicrobial activities of N-functionalized cyclam based unsymmetrical dicompartmental binuclear nickel(II) complexes

Five binuclear nickel(II) complexes have been prepared by simple Schiff base condensation of the compound 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-l,4,8,11-tetraazacyclotetradecane (L) with appropriate aliphatic or aromatic diamine, nickel(II) perchlorate and triethylamine. All the complexes were characterized by elemental and spectral analysis. Positive ion FAB mass spectra show the presence of dinickel core in the complexes. The electronic spectra of the complexes show red shift in the d–d transition. Electrochemical studies of the complexes show two irreversible one electron reduction processes in the range of 0 to −1.4 V. The reduction potential of the complexes shifts towards anodically upon increasing chain length of the macrocyclic ring. All the nickel(II) complexes show two irreversible one electron oxidation waves in the range 0.4–1.6 V. The observed rate constant values for catalysis of the hydrolysis of 4-nitrophenyl phosphate are in the range of 1.36 × 10⁻²–9.14 × 10⁻² min⁻¹. The rate constant values for the complexes containing aliphatic diimines are found to be higher than the complexes containing aromatic diimines. Spectral, electrochemical and catalytic studies of the complexes were compared on the basis of increasing chain length of the imine compartment. All the complexes show higher antimicrobial activity than the ligand and metal salt.     

Effect of salt concentrations on the displacement adsorption enthalpies of denatured protein folding at a moderately hydrophobic surface

Lead(II) complexes of reduced glutathione (GSH) of general composition [Pb(L)(X)]·H₂O (where L=GSH; X=Cl, NO₃, CH₃COO, NCS) have been synthesized and characterized by elemental analyses, infrared spectra and electronic spectra. Thermogravimetric (TG) and differential thermal analytical (DTA) studies have been carried out for these complexes. Infrared spectra indicate deprotonation and coordination of cysteinyl sulphur with metal ion. It indicates the presence of water molecule in the complexes that has been supported by TG/DTA. The thermal behaviour of complexes shows that water molecule is removed in first step-followed removal of anions and then decomposition of the ligand molecule in the subsequent steps. Thermal decomposition of all the complexes proceeds via first order kinetics. The thermodynamic activation parameters, such as E*, A, ΔH*, ΔS* and ΔG* have been calculated. The geometry of the metal complexes has been studied with the help of molecular modeling for energy minimization calculation.     

Transition metal(II) complexes of (E)-cinnamoylferrocene (S)-methylcarbodithioylhydrazone

A new organometallic ligand, (E)-cinnamoylferrocene (S)-methylcarbodithioylhydrazone (HCfmc) and six transition metal(II) complexes thereof M(Cfmc)2·nH2O (M=Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Hg2+; n=0–2) have been prepared and characterized by elemetal analyses, i.r., u.v., 1H-n.m.r. spectra, electrochemical properties, fluorescence spectra and molar conductances. The HCfmc ligand acts as a bidentate donor, coordinating to the metal ions via nitrogen and sulfur atoms with a trans-configuration.     

Homo- and hetero-nuclear chromium(III) complexes with natural ligands. Part 3. Chromium(III)/vanadium(IV) species isolated from the redox systems

Four new heteronuclear Cr^III/V^IV complexes have been isolated from the redox [Cr^III–V^v–L₁–L₂] systems (L₁ = glycine, glutaminic and nicotinic acids, L₂ = cysteine and glutathione). The complexes have been analysed by spectroscopic methods (diffuse reflectance u.v./vis., i.r.) and by FAB mass spectra. A significant bathochromic shift of the d–d Cr^III and V^IV transitions in heteronuclear complexes (d¹–d³) in comparison to the Cr^III homonuclear species (d³/d³) has been related to the interaction of two metal centres. Spectral analyses by the digital filter and band deconvolution methods are presented.     

meso‐Thiaporphyrinoids Revisited: Missing of Sulfur by Small Metals

Facile synthesis of meso‐aryl‐substituted 5,15‐dithiaporphyrins and 10‐thiacorroles has been achieved by sulfidation of α,α′‐dichlorodipyrrin metal complexes with sodium sulfide in DMF. Thiacorrole metal complexes exhibit distinct aromaticity due to 18 π‐conjugation including the lone pair on sulfur, whereas dithiaporphyrins are nonaromatic judging from ¹H NMR spectra, X‐ray analysis, and absorption spectra. We have found that Ni^II and Al^III dithiaporphyrin complexes undergo smooth thermal sulfur extrusion reaction to give the corresponding thiacorrole complexes, whereas free base, Zn^II, Pd^II, and Pt^II dithiaporphyrin complexes did not exhibit the similar reactivity. The DFT calculations have elucidated a reaction pathway involving an episulfide intermediate, which can explain the markedly different reactivity among dithiaporphyrin metal complexes.     

Palladium(II) and platinum(II),(IV) complexes of 2-aminopyrimidine derivatives

Palladium(II) and Platinum(II),(IV) complexes with 2-aminopyrimidine derivatives (L1)–(L3), prepared by reacting the corresponding metal halide with the ligand in the required stoichiometric ratio, were characterised by chemical analyses and physical measurements. The structures have been assigned on the basis of i.r. spectroscopy, electronic reflectance spectra and molar conductivities.     

Synthesis,magnetic and spectral studies of iron(III), cobalt(II,III), nickel(II), copper(II) and zinc(II) complexes of 4–formylantipyrine N(4)-antipyrinylthiosemicarbazone

4–Formylantipyrine N(4)-antipyrinylthiosemicarbazone and its metal complexes have been synthesized and characterized. Elemental analyses, molar conductivities, magnetic measurements and spectral (i.r., electronic, n.m.r., e.s.r.) studies have been used to characterize the complexes. The i.r. spectra show that the thiosemicarbazones behave as bidentate (NS) or tridentate ligands (ONS), either in the thione or thiolato form. Stereochemistries are proposed for the complexes on the basis of both spectral and magnetic studies.