title: Switching of the triplet excited state of styryl 2,6-diiodo-bodipy and its application in acid-activatable singlet oxygen photosensitizing.
abstract: IodoBodipy-styrylBodipy dyads triplet photosensitizers were prepared (B-1 and B-2) which contain acid-responsive moiety. Both compounds show broadband visible light absorption, due to the resonance energy transfer (RET) between the two different visible light-harvesting Bodipy units. The photophysical properties of the dyads were studied with steady-state and nanosecond time-resolved transient absorption spectroscopy. The production of triplet excited state is switched ON or OFF by protonation/deprotonation of the amino group in the dyads. In the neutral form, the excited state is short-lived (<10 ns) and no singlet oxygen ((1)O2) photosensitizing was observed. Upon protonation, a long-lived triplet excited state was observed (τT = 3.1 μs) and the (1)O2 quantum yield (ΦΔ) is up to 73.8%. The energy levels of the components of the dyads were changed upon protonation and this energy level tuning exerts significant influence on the triplet state property of the dyad. Acid-activated shuffling of the localization of the triplet excited state between two components of a dyad was observed. Furthermore, we observed a rare example that a chromophore giving shorter absorption wavelength is acting as the singlet energy acceptor in RET. The experimental results were rationalized by density functional theory (DFT) and time-dependent DFT (TDDFT) calculations.
authors.affiliation: State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology , Dalian 116024, China.
authors.forename: Ling
authors.initials: L
authors.lastname: Huang
authors.forename: Wenbo
authors.initials: W
authors.lastname: Yang
authors.forename: Jianzhang
authors.initials: J
authors.lastname: Zhao
mesh_terms: D001896:Boron Compounds / Q000737:chemistry*; D007454:Iodides / Q000737:chemistry*; D008027:Light; D015394:Molecular Structure; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000737:chemistry; D011789:Quantum Theory; D026082:Singlet Oxygen / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013343:Styrenes / Q000737:chemistry*
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D007454:Iodides; D017319:Photosensitizing Agents; D013343:Styrenes; D026082:Singlet Oxygen