Mononuclear and dinuclear Re(i) complexes incorporating 1-(2-pyridylazo)-2-naphthol: synthesis, structure, spectral, DFT and TDDFT studies

Abstract

The Re(I) complexes [Re(HPAN)(CO)₃Cl], 1, and [Re₂(PAN)₂(CO)₆]·C₆H₁₂, 2·C₆H₁₂, have been prepared by reacting [Re(CO)₅Cl] with HPAN. Here (PAN)⁻ is the deprotonated form of 1-(2-pyridylazo)-2-naphthol. A subsequent reaction of [Re(HPAN)(CO)₃(CF₃SO₃)] with a chelating diphosphine ligand generates [Re(PAN)(CO)(P–P)]·CH₂Cl₂, 3·CH₂Cl₂. The structures of the complexes are determined by X-ray crystallography. The molecular structures observed in the solid state are retained in the solution (¹H, ¹³C and ³¹P NMR and mass spectra). The photophysical and electrochemical properties are also investigated. The gas-phase geometry optimization and the electronic structures of [Re(HPAN)(CO)₃Cl], [Re₂(PAN)₂(CO)₆] and [Re(PAN)(CO)(P–P)] have been investigated with the framework of density functional theory. The absorption spectra of the complexes are calculated by time dependent density functional theory (TDDFT) using a conductor-like polarizable continuum model (CPCM). DFT calculation shows good agreement with the experimental ground state IR and NMR values. Excited state TDDFT calculations provide a better insight into the experimental luminescence spectra of all the complexes in solution.