Synthesis, functionalization, characterization, and photophysical study of carbonyl-containing isocyano rhenium(I) diimine complexes

New classes of tunable rhenium(I) diimine luminophores with formula of [Re(CO)(CNR)₃(N-N)]PF₆ and [Re(CO)(L_x) - (CNC₆H₄Cl-4)₂(1,10-phenanthroline)]PF ₆, (R = C₆H₅, 4-BrC₆H₄, 4-ClC₆H₄, 4-MeOC₆H₄, 2,6- ⁱPr₂C₆H₃; N-N = 1,10-phenanthroline, 5,6-dibromo-1,10-phenanthroline, 4,4'-di-tert-butyl-2,2'-bipyridine; L _x = MeCN, pyridine and PPh₃) have been synthesized. Different synthetic routes including photo-ligand substitution and thermal carbonyl ligand substitution through the oxidative decarbonylation with trimethyl amine N-oxide, for the facial and meridional isomeric forms of [Re(CO)- (CNR)₃(N-N)]PF₆ were investigated. On the basis of these synthetic strategies, different ligand modification and functionalization of the rhenium(I) diimine luminophores with tailored excited state properties could be readily achieved. The structures of both facial and meridional conformations of [Re(CO)(CNR)₃(N-N)]PF₆ and the complex precursors fac-[Re(CO)₃(CNC₆H₃ ⁱPr-2,6)₃]OTf were determined by X-ray crystallography. These complexes display an orange to red ³MLLCT [dπ(Re) → π*(N-N)] phosphorescence at room temperature. Detailed photophysical investigations revealed that the physical, photophysical, electrochemical, and excited state properties can be fine-tuned and tailored through the modifications of the substituents on isocyanide or diimine ligands. © 2011 American Chemical Society.