Strongly Phosphorescent Neutral Rhenium(I) Isocyanoborato Complexes: Synthesis, Characterization, and Photophysical, Electrochemical, and Computational Studies

A new series of neutral isocyanoborato rhenium(I) diimine complexes [Re(CO)3(N^N)(CNBR3)], where N^N=bpy, 4,4′‐Me2bpy, phen, 4,7‐Me2phen, 2,9‐Me2phen, 3,4,7,8‐Me4phen; R=C6F5, C6H5, Cl, 4‐ClC6H4, 3,5‐(CF3)2C6H3, with various isocyanoborate and diimine ligands of diverse electronic and steric nature have been synthesized and characterized. The X‐ray crystal structures of six complexes have also been determined. These complexes displayed intense bluish green to yellow phosphorescence at room temperature in dichloromethane solution. The photophysical and electrochemical properties of these complexes had been investigated. To elucidate the electronic structures and transitions of these complexes, DFT and TD‐DFT calculations have been performed, which revealed that the lowest‐energy electronic transition associated with these complexes originates from a mixture of MLCT [dπ(Re)→π*(N^N)] and LLCT [π(CNBR3)→π*(N^N)] transitions. Isocyanoborato rhenium(I) diimine complexes have been synthesized and characterized. These highly phosphorescent species have quantum yields of up to 0.67 and emission colors that are readily tunable from bluish green to yellow (λ=481–554 nm). Photophysical, electrochemical, and computational studies have been carried out to provide insights into the design of neutral phosphorescent materials from these complexes.