The effect of group-substitution on structures and photophysical properties of rhenium(I) tricarbonyl complexes with pyridyltetrazole ligand: A DFT/TDDFT study

A series of rhenium(I) tricarbonyl complexes having a general formula fac-[Re (CO)3(L)(R-NˆN)] (L = Br; N∧N = tert-butylated pyridyltetrazole; R = H, 1; NO2, 2; CN, 3; OCH3, 4; CH3, 5) have been investigated theoretically by density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The calculated results reveal that introductions of different groups on R position of NˆN ligand can induce changes on electronic structures, photophysical properties and emission quantum yield for these complexes. When the electron-withdrawing groups (NO2 and CN) are introduced in complex 2 and 3, the lowest energy absorption and emission bands are red-shifted compared with that of 1. On the contrary, the introduction of electron-donating group (OCH3 and CH3) in complex 4 and 5 cause corresponding blue-shifted. For these complexes, the stronger electron-donating ability of introduced group on NˆN ligand is, the larger blue-shifted of the lowest energy absorption and emission bands is. The solvent effect on absorption and emission spectrum indicates that the lowest-energy absorption and emission bands have both red shifts with the decrease of solvent polarity. The electronic affinity (EA), ionization potential (IP) and reorganization energy (λ) results show that complex 4 may be suitable to be used as an emitter in organic light-emitting diodes OLEDs. Meanwhile the emission quantum yield of complex 4 is possibly higher than other complexes.