Aquaoxobis(quinoline-2-carboxylato-N,O)vanadium(IV) ethanol hemisolvate

Abstract

The title compound, [VO(C10H6NO2)2(H2O)]2·C2H5OH, contains six‐coordinate VIV atoms. The central VIV atom in each of the two crystallographically independent mol­ecules has a distorted octahedral coordination geometry, involving O atoms of the oxo and aqua ligands, together with two O and two N atoms of two organic ligands.

The Equilibrium Between the Octahedral and Square Pyramidal Form and the Influence of an Axial Ligand on the Molecular Properties of VIVO Complexes: A Spectroscopic and DFT Study

“…[27] The tendency of this class of ligands (the derivatives of 6methylpicolinic acid) to coordinate an axial water trans to the V=O group, in contrast to acetylacetonate and maltolate, for example, [9,28] is interestingly confirmed by the solid species formed by 6-ethylpicolinic (6-etpicH) and 2-quinolinecarboxylic acids, the X-ray structures of which have been reported in the literature: both are octahedral with a water molecule axially coordinated at around 2.3 . [23,29] No particular solid-state effects, which may force the coordination of the solvent molecule in the sixth coordination position (these compounds precipitate from water or a water/ethanol mixture, respectively) seem to be operating.…”

“…Interestingly, for the (N,O) ligands, the two octahedral structures are formed by two picolinic derivatives, 6-ethylpicolinic and quinaldic acid. [23,29] The "additivity rule" can be successfully applied to all the pentacoordinated complexes. However, the presence of an axial ligand (charged or not) can change the A z value, which suggests that the statement that axial ligands do not contribute to the A z value must be revised.…”

trans-Diaquabis(isoquinoline-1-carboxylato-κ2N,O)zinc(II) dihydrate

“…The Zn atom lies on a centre of symmetry. The coordination mode of (I) strongly resembles that of the Co II and Ni II complexes (Okabe & Muranishi, 2002). The coordination bond length in the axial direction [Zn1ÐO1W 2.208 (2) A Ê ] is longer than those in the equatorial plane (Table 1).…”

“…These results indicate that the order of stability of these complexes corresponds to the well known Irving±Williams series, Co II < Ni II < Cu II > Zn II . In the crystal structure, the isoquinoline rings are stacked with respect to each other, with a mean separation distance of 3.392 (5) A Ê , in a manner similar to that in the Co II and Ni II complexes (Okabe & Muranishi, 2002). Hydrogen bonds are formed between the coordinated water, the carboxylate group and the uncoordinated water molecules ( Table 2).…”

“…Isoquinoline-1-carboxylic acid (IQCA) inhibits the copper enzyme, dopamine -hydroxylase (Townes et al, 1990). Previously, the crystal structures of the Cu II (Tomas et al, 1999), Sn IV (Smith et al, 1995), Co II and Ni II complexes (Okabe & Muranishi, 2002) of IQCA have been reported, establishing the coordination modes of the complexes. In this study, we sought to determine the structure of the Zn II complex (I), because Zn II has many important biological functions, for example as a catalytic ion in many enzymes such as alcohol dehydrogenase (Esposito et al, 2002), or a zinc ®nger motif in a ribosomal protein (Dresios et al, 2002) or an insulin-mimetic complex in metallopharmaceutical compounds (Sakurai et al, 2002).…”