A detailed investigation of light-harvesting efficiency of blue color emitting divergent iridium dendrimers with peripheral phenylcarbazole units

作者：Cho Yang Jin; Wee Kyung Ryang; Son Ho Jin; Cho Dae Won^*; Kang Sang Ook

来源：Physical Chemistry Chemical Physics, 2014, 16(10): 4510-4521.

DOI：10.1039/c3cp53797h

The increase in phosphorescence efficiency was estimated by the energy transfer mechanism for divergent iridium dendrimers with peripheral phenylcarbazole units. A series of Ir-core/phenylcarbazole-end dendrons of the type, Ir(dfppy)(2)(pic-Cz(n)) (Gn, n = 0, 1, 2, and 3), was synthesized, where dfppy, pic, and Cz(n) (n = 2, 4, and 8) are 2-(4,6-difluorophenyl)pyridine, picolinate substituted with Cz(n) at the 3-position, and 4-(9-carbazolyl)phenyldendrons connected with 3,5-di(methyleneoxy)benzyloxy branches, respectively. Selective excitation of the Cz(n) units of G1-G3 resulted in >90% quenching of the Cz fluorescence accompanied by the growth of phosphorescence from the Ir(dfppy) 2(pic) core as a consequence of energy transfer from the excited-singlet Cz(n) chromophore to the core. The rate constants of energy transfer were determined by steady-state and transient spectroscopic measurements to be 4.32 x 10(9) s(-1) (G1), 2.37 x 10(9) s(-1) (G2), and 1.46 x 10(9) s(-1) (G3), which were in good agreement with those calculated using the Forster model. The phosphorescence enhancements were 157 (G1), 213 (G2), and 264% (G3) when compared to the phosphorescence of the core Ir(dfppy)(2)(pic-Ph-2) (G0), in which pic-Ph-2 is 3-(3,5-dibenzyloxybenzyl) picolinate.

• 出版日期2014