title: Novel Re(I) dendrimers: synthesis, characterization and theoretical studies.
abstract: Four novel diimine rhenium(I) carbonyl complexes with the formula [Re(CO)3(L)Br], where L = 2-(4-(9H-carbazol-9-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline (P1), 2-(4-(3,6-di-tert-butyl-9H-carbazol-9-yl)phenyl)-1H-imidazo-[4,5-f][1,10]phenanthroline (P2), 2-(4-(6-(9H-carbazol-9-yl)-9H-3,9-bicarbazol-9-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline (D1), and 2-(4-(3',6'-di-tert-butyl-6-(3,6-di-tert-butyl-9H-carbazol-9-yl)-9H-3,9-bicarbazol-9-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline (D2), have been successfully synthesized and fully characterized by 1H NMR, IR, and UV-Vis, etc. The luminescence quantum yields (LQYs) of the parent Re(I) complexes P1 and P2 are 0.13 and 0.16, respectively, which are much higher than the previously reported Re(I) dendrimers. The HOMOs and the LUMOs of P1 and P2 are calculated to be mainly composed of [d(Re) + pi(CO + Br)] and pi*(L) orbital, respectively. However, those of the Re(I) dendrimers D1 (LQY = 0.066) and D2 (LQY = 0.0048) are mainly localized on ligand L, indicating that the component of the metal-to-ligand charge-transfer d pi (Re) --> pi*(N-N) (MLCT) transitions in P1 and P2 should be more than those in D1 and D2. As a result, the higher LQYs of P1 and P2 are tentatively assigned to the disturbance of the MLCT transitions during the photoluminescence process.
authors.affiliation: State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, People's Republic of China.
authors.forename: Zhenjun
authors.initials: Z
authors.lastname: Si
authors.forename: Xiaona
authors.initials: X
authors.lastname: Li
authors.forename: Xiyan
authors.initials: X
authors.lastname: Li
authors.forename: Guohai
authors.initials: G
authors.lastname: Xu
authors.forename: Chenling
authors.initials: C
authors.lastname: Pan
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Guo
authors.forename: Hongjie
authors.initials: H
authors.lastname: Zhang
authors.forename: Liang
authors.initials: L
authors.lastname: Zhou