Synthesis and Characterization of Oxovanadium Complexes Featuring O- and N- Donor Environment

Vanadium is currently receiving considerable attention as a biologically important metal due to the existence of vanadoenzymes and medicinal importance. Discovery of a vanadium containing cofactor in bromoperoxidases and nitrogenases has evoked new interest in coordination chemistry of vanadium. Exploration of chemical and electrochemical reactivity of oxovanadium(V) complexes in general and vanadium(V) alkoxides in particular are of current interest. To extend these observations, I focus my interest on the synthesis and characterizations of new mononuclear oxovanadium complex featuring O-N-donor ligand in relation to the biological and catalytic activities. In this dissertation I report the synthesis, structure and full characterization of a new mononuclear square pyramidal monoalkoxo-bound monooxo-vanadium (V) complex VOL2S(OEt) (1) of 2-Hydroxyacetophenonehydrazone of 2-Hydroxybenzoylhydrazine Ligand. I also report the synthesis of several other Schiff’s bases and their respective oxovanadium complexes. Due to insufficient data and time limit I am unable to report the complete characterization of all these complexes (2-4)

A Mixed Heavier Si=Ge Analogue of a Vinyl Anion

The versatile reactivities of disilenides and digermenide, heavier analogues of vinyl anions, have significantly expanded the pool of silicon and germanium compounds with various unexpected structural motifs in the past two decades. We now report the synthesis and isolation of a cyclic heteronuclear vinyl anion analogue with a Si=Ge bond, potassium silagermenide as stable thf‐solvate and 18‐c‐6 solvate by the KC8 reduction of germylene or digermene precursors. Its suitability as synthon for the synthesis of functional silagermenes is proven by the reactions with chlorosilane and chlorophospane to yield the corresponding silyl‐ and phosphanyl‐silagermenes. X‐ray crystallographic analysis, UV/Vis spectroscopy and DFT calculations revealed a significant degree of π‐conjugation between N=C and Si=Ge double bonds in the title compound

Ein gemischtes, schwereres Si=Ge Analogon eines Vinylanions

Die vielseitigen Reaktivitten von Disileniden und Digermenid, schwereren Analoga von Vinylanionen, haben den Pool an Silicium- und Germaniumverbindungen in den letzten zwei Jahrzehnten mit verschiedensten unerwarteten Strukturmotiven erheblich erweitert. Wir berichten nun ber die Synthese eines cyclischen, heteronuklearen Vinylanionanalogons mit einer Si=Ge Bindung, dem Kaliumsilagermenid als stabiles THF- und 18-c-6-Solvat durch KC8 Reduktion von Germylen- oder Digermenvorlufern. Seine Eignung als Baustein fr die Synthese von funktionellen Silagermenen wird durch die jeweiligen Reaktionen mit Chlorsilan und Chlorphosphan unter Bildung der entsprechenden Silyl- und Phosphanylsilagermenen nachgewiesen. Rçntgenkristallographische Analyse, UV/Vis Spektroskopie und DFT Berechnungen zeigten einen erheblichen Grad an p-Konjugation zwischen N=C und Si=Ge Doppelbindungen in der Titelverbindung

A study of DNA/BSA interaction and catalytic potential of oxidovanadium(V) complexes with ONO donor ligands

The study of DNA/BSA interaction and the catalytic potential of four mononuclear oxidoalkoxido vanadium(V) [VVO(L¹⁻⁴)OEt] (1–4) and one dinuclear oxidoalkoxido mixed-ligand vanadium(V) [{VO(L²)OEt} ₂ (Q)]{Q = 4,4′-bipyridine}(5) complexes, with tridentate binegative aroylazine ligands are reported [where H₂L¹ = anthranylhydrazone of 2- hydroxy-1- napthaldehyde, H₂L² = salicylhydrazone of 2-hydroxy-1- napthaldehyde, H₂L³ = benzoylhydrazone of 2-hydroxy-1- acetonaphthone, H₂L⁴ = anthranylhydrazone of 2-hydroxy-1- acetonaphthone]. All the complexes are characterized by elemental analysis as well as various spectroscopic techniques. Single crystal X-ray diffraction crystallography of 2 reveals that the metal centre is in distorted square pyramidal geometry with O₄N coordination spheres, whereas 5 exhibits a distorted octahedral geometry around the metal center. In addition, all the complexes (1–5) show moderate DNA binding propensity which is investigated using UV-vis absorption titration, circular dichroism, thermal denaturation and fluorescence spectral studies. The experimental results show that the complexes effectively interact with CT-DNA through both minor and major groove binding modes, with binding constants ranging from 10⁴ −10⁵ M⁻¹. Among 1–5, complexes 3 and 4 show higher binding affinity towards CT-DNA than others and at the same time also exhibit negative ΔTm values of about ∼1.5 and 1.0 °C which resembles the properties shown by cisplatin. All complexes show moderate photo-induced cleavage of pUC19 supercoiled plasmid DNA with complex 3 showing the highest photo induced DNA cleavage activity of ∼48%. In coherence with the DNA interaction studies, 3 and 4 also exhibit good binding affinity towards BSA in the range of 10¹⁰ −10¹¹ M⁻¹, which is also supported by their ability to quench the tryptophan fluorescence emission spectra of BSA. All the complexes show remarkable photo-induced BSA cleavage activity (>90%) at a complex concentration of 50 μM. The catalytic potential of 1–5 is also tested for the oxidative bromination of styrene, salicylaldehyde and oxidation of methyl phenyl sulphide. All the reactions show a high percentage of conversion (>90%) with a high turnover frequency (TOF). Particularly, in the oxidative bromination of styrene the percentage of conversion and TOF vary from 96–98% and 8000–19 600 (h⁻¹) respectively, which signifies the potential of these oxidovanadium(V) complexes to stimulate research for the synthesis of a better catalyst

Synthesis and spectroscopic properties of cobalt(III) complexes of some aroyl hydrazones: x-ray crystal structures of one cobalt(III) complex and two aroyl hydrazone ligands

Cobalt(III) complexes of diacetyl monooxime benzoyl hydrazone (dmoBH(2)) and diacetyl monooxime isonicotinoyl hydrazone (dmoInH(2)) have been synthesized and characterized by elemental analyses and spectroscopic methods. The X-ray crystal structures of the two hydrazone ligands, as well as that of the cobalt(III) complex [Co(III)(dmoInH)(2)]Cl center dot 2H(2)O, are also reported. It is found that in the cobalt(III) complexes the Co(III) ion is hexa-coordinated, the hydrazone ligands behaving as mono-anionic tridentate O,N,N donors. In the [Co(III)(dmoInH) (2)]Cl center dot 2H(2)O complex, the amide and the oxime hydrogens are deprotonated for both the ligands, while the isonicotine nitrogens are protonated. In the [Co(III)(d-moBH)(2)] Cl complex, only the amide nitrogens are deprotonated. It is shown that the additional hydrogen bonding capability of the isonicotine nitrogen results in different conformation and supramolecular structure for dmoInH(2), compared to dmoBH(2), in the solid state. Comparing the structure of the [CoIII(dmoInH)(2)]Cl center dot 2H(2)O with that of the Zn(II) complex of the same ligand, reported earlier, it is seen that the metal ion has a profound influence on the supramolecular structure, due to change in geometrical dispositions of the chelate rings

Synthesis of Backbone <i>P</i>‑Functionalized Imidazol-2-ylidene Complexes: <i>En Route</i> to Novel Functional Ionic Liquids

1-Alkyl-3-methyl-4-diphenylphosphoryl-imidazolium hydrogensulfate (<b>4a</b>,<b>b</b>) (<b>a</b>: R¹ = R² = Me; <b>b</b>: R¹ = ^<i>i</i>Pr, R² = Me) and 1-alkyl-3-methyl-4,5-bis­(diphenylphosphoryl)­imidazolium hydrogensulfate (<b>6a,c</b>) (<b>c</b>: R¹ = ^<i>n</i>Bu, R² = Me) were obtained selectively and in good yields by oxidative desulfurization of 1-alkyl-3-methyl-4-diphenylphosphino-imidazole-2-thiones (<b>2a</b>,<b>b</b>) and 1-<i>n</i>-butyl-3-methyl-4,5-bis­(diphenylphosphoryl)­imidazole-2-thione (<b>3c</b>) or 1,3-dimethyl-4-diphenylthiophosphoryl-5-diphenylphosphino-imidazole-2-thione (<b>5a</b>), respectively, with hydrogen peroxide. Synthesis of phosphoryl functionalized imidazol-2-ylidene complexes of group VI metal pentacarbonyls (<b>7a</b>–<b>9a</b>) and (<b>10b</b>–<b>12b</b>) and bis­(phosphoryl) functionalized imidazol-2-ylidene complexes of group VI metal pentacarbonyls (<b>13c</b>–<b>15c</b>) and (<b>16a</b>) with low steric demand (methyl, isopropyl, <i>n</i>-butyl) at both <i>N</i>-centers was achieved through deprotonation of imidazolium salts (<b>4a</b>,<b>b</b>) and (<b>6a</b>,<b>c</b>), respectively,having HSO₄^– as a counterionwith potassium <i>tert</i>-butoxide followed by rapid addition of metal pentacarbonyl acetonitrile complexes [M­(CO)₅(CH₃CN)] (M = Cr, Mo, W). The products were unambiguously characterized by elemental analyses, spectroscopic and spectrometric methods, and in addition, by single-crystal X-ray structure studies in the cases of <b>4b</b>, <b>8a</b>, <b>15c</b>, and <b>16a</b>; the latter two reveal imidazole ring bond distance alternation in contrast to <b>8a</b>

Inorganic-Salt-Free Reduction in Main-Group Chemistry: Synthesis of a Dibismuthene and a Distibene

A dibromobismuthine and a dibromostibine that bear 4-<i>t</i>Bu-2,6-[CH­(SiMe₃)₂]₂-C₆H₂ (Tbb) groups were reduced with 2,3,5,6-tetramethyl-1,4-bis­(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene to afford the corresponding stable dibismuthene (TbbBiBiTbb) and the distibene (TbbSbSbTbb), respectively. The only byproducts obtained were easily removable tetramethylpyrazine and bromotrimethylsilane. Importantly, inorganic salts were not generated in this reduction: i.e., this is a unique inorganic-salt-free method for the synthesis of compounds with multiple bonds between heavier main-group elements

Inorganic-Salt-Free Reduction in Main-Group Chemistry: Synthesis of a Dibismuthene and a Distibene

A dibromobismuthine and a dibromostibine that bear 4-<i>t</i>Bu-2,6-[CH­(SiMe₃)₂]₂-C₆H₂ (Tbb) groups were reduced with 2,3,5,6-tetramethyl-1,4-bis­(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene to afford the corresponding stable dibismuthene (TbbBiBiTbb) and the distibene (TbbSbSbTbb), respectively. The only byproducts obtained were easily removable tetramethylpyrazine and bromotrimethylsilane. Importantly, inorganic salts were not generated in this reduction: i.e., this is a unique inorganic-salt-free method for the synthesis of compounds with multiple bonds between heavier main-group elements

Inorganic-Salt-Free Reduction in Main-Group Chemistry: Synthesis of a Dibismuthene and a Distibene

A dibromobismuthine and a dibromostibine that bear 4-<i>t</i>Bu-2,6-[CH­(SiMe₃)₂]₂-C₆H₂ (Tbb) groups were reduced with 2,3,5,6-tetramethyl-1,4-bis­(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene to afford the corresponding stable dibismuthene (TbbBiBiTbb) and the distibene (TbbSbSbTbb), respectively. The only byproducts obtained were easily removable tetramethylpyrazine and bromotrimethylsilane. Importantly, inorganic salts were not generated in this reduction: i.e., this is a unique inorganic-salt-free method for the synthesis of compounds with multiple bonds between heavier main-group elements