Dioxo-vanadium(v), oxo-rhenium(v) and dioxo-uranium(vi) complexes with a tridentate Schiff base ligand

Abstract

The complexation of a julolidine–quinoline based tridentate ligand with three oxo-metal ions, dioxo-vanadium(V), oxo-rhenium(V) and dioxo-uranium(VI), has been investigated with four new complexes being synthesised and structurally characterised. (VO₂L)·2/3H₂O (1) {HL (C₂₂H₂₁N₃O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} has a VO₂L neutral mononuclear structure with a five-fold coordinated vanadium metal centre in a distorted trigonal bipyramidal geometry. (ReOL₂)₂(ReCl₆)·7DMF (2) [DMF = dimethylformamide] exhibits a mixed valent rhenium complex with a (ReOL₂)⁺ cationic unit in a distorted octahedral metal coordination geometry, charge balanced with (ReCl₆)²⁻ anions. [(UO₂)L(H₂O)₂]₂·2(NO₃)·HL·4H₂O (3) and [(UO₂)L(CH₃OH)₂](NO₃)·CH₃OH (4) both have (UO₂L)⁺ cationic mononuclear structures with either coordinated water or methanol molecules in pentagonal bipyramidal coordination geometries for the uranium metal centres. Intra-/intermolecular interactions including hydrogen bonding and π–π interactions are common and have been discussed. In addition, optical absorption and photoluminescence properties have been investigated.