Synthesis, Characterization, and Photophysical and Emission Solvatochromic Study of Rhenium(I) Tetra(isocyano) Diimine Complexes

A new series of rhenium(I) tetra(isocyano) diimine complexes ([Re(CNR)₄(N–N)]⁺, where R = 4-IC₆H₄, 4-BrC₆H₄, 4-Br-2,6-Me₂C₆H₂, 2,4,6-Cl₃C₆H₂, 2,4,6-Br₃C₆H₂, 2,4-Cl₂-6-MeOC₆H₂ and N–N = bpy, (MeO)₂bpy, ^tBu₂bpy, phen, 1-methyl-2-(2′-pyridyl)imidazole) with various isocyanide and diimine ligands of diverse electronic and steric natures has been synthesized and characterized. The X-ray crystal structures of four of the target complexes were also determined. These complexes were found to show orange to red MLCT (dπ(Re) → π*(N–N)) phosphorescence. Given the submicrosecond solution emission lifetime, nanosecond transient absorption spectroscopic studies have been performed. The emission solvatochromic behavior and the electrochemical properties of these complexes and their structural correlation have also been reported.