Indexed by:Journal Papers

Date of Publication:2015-11-01

Journal:DYES AND PIGMENTS

Included Journals:EI、SCIE、Scopus

Volume:122

Page Number:286-294

ISSN No.:0143-7208

Key Words:Aza-boron-dipyrromethene; Heavy atom effect; Ultrafast pump probe spectroscopy; Intersystem crossing; Two photon absorption; Z-scan technique

Abstract:New aza-boron-dipyrromethene compounds containing bromine atoms at various positions were designed and synthesized to enhance the triplet state population and two photon absorption properties for applications such as two-photon photodynamic therapy, triplet triplet annihilation up-conversion. Steady state fluorescence and ultrafast pump probe spectroscopy techniques revealed that only 2, 6 positions of aza-boron-dipyrromethene core contribute to triplet state population significantly. Density function theory calculations showed that when bromine atoms introduced to 2, 6 position of aza-boron-dipyrromethene core, singlet and triplet energy levels get closer therefore probability of intersystem crossing increases. Z-scan experiments at 800 nm wavelengths revealed considerably large (610 GM) two photon absorption cross section value with respect to literature for compounds showing intersystem crossing mechanism. The efficient intersystem crossing and enhanced two-photon absorption properties make the investigated aza-boron-dipyrromethene compounds good candidates for two-photon photodynamic therapy application. (C) 2015 Elsevier Ltd. All rights reserved.