Synthesis, crystal structure, electrochemistry and thermal analysis of an oxalato bridged Cr(III)-Pb(II) heterometallic coordination compound

Abstract

Oxalato bridged Cr(III)-Pb(II) compound of molecular formula [{Pb(phen)2}2Cr(ox)2(phen)] [Cr(ox)2(phen)](NO3)2 (1) [ox = oxalate anion, C2O42−, phen = 1,10-phenanthroline] has been synthesized and characterized by X-ray crystallography, FT-IR and fluorescence spectroscopy, electrochemical and thermal analysis. The single crystal diffraction analysis revealed that the asymmetric unit of complex 1comprises of a trinuclear cationic species [{Pb(phen)2}2Cr(ox)2(phen)]3+(where metals are bridged by oxalate anions in η4μ mode) counterbalanced by an anionic complex [Cr(ox)2(phen)]− and two nitrate anions. Chromium atoms exhibit a distorted octahedral environment in both fragments, while the six-coordinated lead atoms show an hemidirected coordination geometry that allows the formation of weaker Pb…ONO2 interactions (tetrel bonds). At room temperature complex 1 exhibits fluorescence at 365 and 383 nm in methanol (λex= 268 nm, Φ = 0.38). In addition, the complex is redox active and the cyclic voltammograms recorded at different scan rate showed that the irreversible peak corresponds to the Cr+3/Cr2+ couple. Thermogravimetric analysis indicates that the compound starts to decompose at 33.7 °C and collapses at ∼ 277 °C.