DFT/TDDFT studies of the ancillary ligand effects on structures and photophysical properties of rhenium (I) tricarbonyl complexes with the imidazo[4,5-f]-1,10-phenanthroline ligand

Abstract

The seven rhenium (I) tricarbonyl complexes having a general formula fac-[ReBr(CO)3(R1,R2,R3-N^N)] (N^N = imidazo[4,5-f]-1,10-phenanthroline; R1 = tBu, R2 = R3 = H, 1; R1 = CCH, R2 = R3 = H, 2; R1 = tBu, R2 = CCH, R3 = H, 3; R1 = tBu, R2 = R3 = CCH, 4; R1 = tBu, R2 = CH3, R3 = H, 5; R1 = tBu, R2 = R3 = CH3, 6; R1 = tBu, R2 = OCH3, R3 = H, 7) have been investigated theoretically by density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The different substituted groups on N^N ligand induce changes on the electronic structures and photophysical properties for these complexes. It is found that the introduction of CC decreases the energy level of lowest unoccupied molecular orbital (LUMO) while the introduction of CH3 or OCH3 lead to increase the energy level of LUMO. The order of LUMO energy level rising is in line with the increasing of donating abilities of substituted groups; and the influence of R2 position is greater than that of R1 position on LUMO energy level. The lowest energy absorption bands have changes in the order of 7 < 6 < 5 < 1 < 2 < 3 < 4. These results of electronic affinity (EA), ionization potential (IP), and reorganization energy (λ) indicate that all of these complexes can be used as electron transporting materials. Moreover, the smallest difference between λelectron and λhole of 4 indicates that it is better to be used as an emitter in the organic light-emitting diodes. © 2015 Wiley Periodicals, Inc.