title: Spectroscopic insights on imidazole substituted phthalocyanine photosensitizers: fluorescence properties, triplet state and singlet oxygen generation.
abstract: Imidazole substituted metal phthalocyanine (Pc) complexes were synthesized. UV-vis absorption, steady state and time-resolved fluorescence, as well as laser flash photolysis were used to measure the photophysical and photosensitizing properties. All the imidazole-phthalocyanine conjugates show high ΦT (quantum yield of excited triplet formation), high ΦΔ (singlet oxygen formation yield, >0.50) and good fluorescence properties (quantum yield Φf>0.20 and lifetime τf>3.0 ns). Compared to the unsubstituted Pc, both α- and β-imidazole substitutions result in the remarkable decrease in Φf and τf, but the α-substitution is stronger. The imidazole substitution, on the other hand, causes the increase of ΦT, τT, and ΦΔ values. Magnesium phthalocyanine (MgPc) is more susceptible to the substitution than zinc phthalocyanine (ZnPc). The mechanism responsible for the result is suggested based on the involvement of intramolecular photoinduced electron transfer. The high ΦΔ and appropriate fluorescence properties make the Pcs good candidate for PDT photosensitizers.
authors.affiliation: Institute of Applied Photochemistry, Hebei Normal University of Science and Technology, Qinhuangdao, Hebei Province 066004, China; MPC Technology, Hamilton, ON L8S 3H4, Canada. Electronic address: zhangxianfu@tsinghua.org.cn.
authors.forename: Xian-Fu
authors.initials: XF
authors.lastname: Zhang
authors.affiliation: Institute of Applied Photochemistry, Hebei Normal University of Science and Technology, Qinhuangdao, Hebei Province 066004, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Lin
authors.affiliation: Institute of Applied Photochemistry, Hebei Normal University of Science and Technology, Qinhuangdao, Hebei Province 066004, China.
authors.forename: Wenfeng
authors.initials: W
authors.lastname: Guo
authors.affiliation: Institute of Applied Photochemistry, Hebei Normal University of Science and Technology, Qinhuangdao, Hebei Province 066004, China.
authors.forename: Jingzhong
authors.initials: J
authors.lastname: Zhu
mesh_terms: D007093:Imidazoles / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D054833:Isoindoles; D017319:Photosensitizing Agents / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D007093:Imidazoles; D007211:Indoles; D054833:Isoindoles; D017319:Photosensitizing Agents; D026082:Singlet Oxygen; C029899:imidazole; C013647:phthalocyanine
keywords: Imidazole; Photodynamic therapy; Phthalocyanine; Singlet oxygen; Synthesis; Triplet state