卟啉多枝分子合成与分子内能量转移、双光子吸收性能研究

以三苯胺或硝基苯为端基, 合成了三个卟啉多枝分子: 5-(4-硝基苯甲酰氧基)苯基-10,15,20-三-(4-溴苯基)卟啉(TPP-NO₂)、5-(4-硝基苯甲酰氧基)苯基-10,15,20-三-(4-二苯胺基-1-苯乙烯基)苯基卟啉(TPP-X₃)和5,10,15,20-四-(4-二苯胺基-1-苯乙烯基)苯基卟啉(TPP-X₄), 进行了红外光谱、核磁共振光谱和质谱表征. 比较研究了分子“枝”、“核”不同键合方式与不同对称结构对分子的线性光谱、非线性光谱以及分子内能量转移行为的影响. 在钛宝石激光器(800 nm)和Nd∶YAG倍频光(532 nm)泵浦下, 样品溶液均发出卟啉环特有的红色荧光——前者系双光子吸收机制“上转换”荧光, 后者则为双光子吸收与分子内能量转移机制“下转换”荧光. 飞秒Z-scan技术测得样品双光子吸收截面最大可达130 GM, 与四苯基卟啉(TPP)同等测试条件下的双光子吸收截面相比增大了两个数量级.

Synthesis of Multibranched Porphyrins with Two-photon Absorption and Intramolecular Energy Transfer

Three new multibranched porphyrins: 5-(4-nitrobenzoxy)-phenyl-10,15,20-tris-(4-bromophenyl)-porphyrin (TPP-NO₂), 5-(4-nitrobenzoxy)-phenyl-10,15,20-tris-(4-N,N-diphenylamino-styryl)- phenyl-porphyrin (TPP-X₃) and 5,10,15,20-tetra-(4-N,N-diphenylamino-styryl)-phenyl-porphyrin (TPP-X₄) were synthesized and characterized by IR, ¹H NMR and MS measurements, respectively. Pumped by 800 nm and 532 nm laser pulses, respectively, the sample solution could emit strong up- and down-conversion fluorescence, wherein the former cound be interpreted by two-photon absorption (TPA) mechanism and the latter was attributed to two-photon absorption and intramolecular energy transfer. TPA cross-section was measured by femtosecond Z-scan technique at 800 nm Ti∶sapphire laser. It was found that TPA cross-section of multibranched porphyrins was enhanced by larger dipole moment difference between the ground- and the excited-state, that is, |Δμ_ge| value, and stronger conjugation effect, that is, π-π conjugation, between porphyrin “core” and branches linked to the porphyrin periphery.