Coordination Chemistry Research Laboratory, Department of Chemistry, DDU Gorakhpur University, Gorakhpur 273 009, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2012 Jun;91:365-9. doi: 10.1016/j.saa.2012.02.017. Epub 2012 Feb 10.
A new method to synthesize some mononuclear ternary oxovanadium(IV) complexes of the general formula [VO(β-dike)(SB)] (where Hβ-dike=acetylacetone; benzoylacetone or dibenzoylmethane, HSB=Schiff bases) has been explored by stepwise substitutions of acetylacetonate ion of VO(acac)(2) with Schiff bases. The substituted acetylacetone could be fractionated out with p-xylene as an azeotrope. The complexes were characterized by elemental analyses, molecular weight determinations, spectral (electronic, infrared, (1)H NMR, EPR and powder XRD) studies, magnetic susceptibility measurements and cyclic voltammetry. Molar conductance measurements indicated the complexes to be non-electrolytes in nitrobenzene. Bidentate chelating nature of β-diketones and Schiff base anions in the complexes was established by infrared and NMR spectra. Molecular weight determinations confirmed mononuclear nature of the complexes. The EPR spectra illustrated coupling of the unpaired electron with (51)V nucleus (I=7/2). Cyclic voltammograms of all the complexes displayed two-step oxidation processes. The oxidation peak potential corresponded to the quasireversible one-electron oxidation process of the metal center, yielding V(V) species. Transmission electron microscopy (TEM) indicated spherical particles of ∼200 nm diameter. The synthesized complexes are mixed-ligand complexes showing a considerable hydrolytic stability in which vanadium is having coordination number 5. A square pyramidal geometry around vanadium has been assigned in all the complexes.
一种新的方法被探索来合成一些单核三元氧钒(IV)配合物，通式为[VO(β-二酮)(SB)]（其中 Hβ-二酮=乙酰丙酮；苯甲酰丙酮或二苯甲酰甲烷，HSB=席夫碱），通过逐步取代 VO(acac)(2)中的乙酰丙酮离子与席夫碱。取代的乙酰丙酮可以用对二甲苯作为共沸剂分馏出来。配合物通过元素分析、分子量测定、光谱（电子、红外、（1）H NMR、EPR 和粉末 XRD）研究、磁化率测量和循环伏安法进行了表征。摩尔电导率测量表明，配合物在硝基苯中是非电解质。红外和 NMR 光谱证实了β-二酮和席夫碱阴离子在配合物中的双齿螯合性质。分子量测定证实了配合物的单核性质。EPR 光谱表明，未配对电子与（51）V 核（I=7/2）发生耦合。所有配合物的循环伏安图都显示了两步氧化过程。氧化峰电位对应于金属中心的准可逆单电子氧化过程，生成 V(V)物种。透射电子显微镜（TEM）表明直径约为 200nm 的球形颗粒。所合成的配合物是混合配体配合物，在其中钒具有配位数 5，并具有相当的水解稳定性。在所有配合物中，都赋予了钒的四方锥几何形状。
