以共价键相连的卟啉-酞菁化合物分子内能量传递及光诱导电子转移

合成了叶啉与酞菁以共价键连接起来的双发色团分子。测定了它们的吸收光谱,荧光光谱,荧光寿命等。计算了分子内能量传递过程的效率(φ_EnT)及速率常数(κ_EnT)。结果表明:在稀溶液中,卟啉与酞菁等克分子混合时,观察不到分子间能量传递过程现象的发生;而双发色团分子的分子内能量传递过程则明显发生了,其效率(φ_EnT=13～70%)与速率常数(κ_EnT=1.2×10⁷～2.0×10⁸s^-1)取决于分子的结构类型。电子转移与能量传递过程与介质性质有关。在极性溶剂中有利于电子转移过程的进行,而不利于能量传递过程;在非极性溶剂中,则有利于能量传递过程的进行,而不利于电子转移。 选择性激发酞菁发色团,观测到了只有电子转移发生的过程,其电子转移效率达到38%。

INTRAMOLECULAR ENERGY TRANSFER AND PHOTOINDUCED ELECTRON TRANSFER IN A COVALENTLY LINKED PORPHYRIN-PHTHALOCYANINE

A covalently linked porphyrin-phthalocyanine heterodimer was synthesied, the absorption spectra, fluorescence spectra, fluorescence lifetime and redox potantials were determined. There is a considerable overlap between the fluorescence spectrum of porphyrin and the ground state absorption spectrum of phthalocyanine, indicating that energy transfer should be extremly efficient. The efficiency and rate constant of intramolecular energy transfer (lEnT) from porphyrin moiety to phthalocyaneine in each model was measured in polar and non-polar solvent. Neither fluorescence quenching by dipole-dipole interaction, nor quenching by collision occurs in dilute mixture of monomers (1/1 mixture of TTP & PC). In contrast, selective excitation at 420nm of the heterodimer, a decrease of the porphyrin fluorescence, concomitant with a slight increase of phthalocyanine fluorescence occurs, indicating IEnT reaction takes place. The efficiency and rate constant of IEnT depends on heterodimer.Selective excitation of the phthalocyanine chromophore in heterodimer, intramolecular electron transfer (IET) takes place only. The efficiency of IET is rather high (38%). IEnT and IET process takes place in competition with different solvent. IEnT process is a very efficient in non-polar solvent, but IET process is a very efficient in polar solvent.