A density functional study of oxorhenium(V) complexes incorporating quinoline or isoquinoline carboxylic acids: structural, spectroscopic, and electronic properties

Density functional theory calculations have been performed for understanding factors responsible for the different stabilities of particular isomers of [ReOX(N-O)(2)], where N-O represents carboxylate ligand chelating to the oxorhenium core through N and O atoms. DFT/B3LYP calculations have been carried out for all possible potential isomers of [ReO(OMe)(2-qc)(2)] (1), [ReOCl(2-qc)(2)] (2), [ReO(OMe)(1-iqc)(2)] (3), and [ReOCl(1-iqc)(2)] (4). Interestingly, complex 1 shows a very rare example of trans [O=Re-OMe] conformation with two chelating N,O-donor ligands in the equatorial plane, whereas the others were found to be the most common structure of [ReOX(N-O)(2)] with cis-N,N arrangement and chloride or methoxy ligand cis to the Re=O moiety. A thorough study of the calculated structures clearly shows that molecular structure of complexes [ReOX(N-O)(2)] is predominantly governed by multiply bonded oxo ligand, but the isomeric preferences may be tuned by careful selection of N-O ligands.