Spectroscopic properties of a self-assembled zinc porphyrin tetramer I. Steady state optical spectroscopy

被引:25
作者
Yatskou, MM [1 ]
Koehorst, RBM [1 ]
Donker, H [1 ]
Schaafsma, TJ [1 ]
机构
[1] Univ Wageningen & Res Ctr, Dept Agrotechnol & Food Sci, Mol Phys Lab, NL-6703 HA Wageningen, Netherlands
关键词
D O I
10.1021/jp010410p
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Aggregation of zinc mono-(4-pyridyl)-triphenylporphyrin (ZnPyP) in toluene and polystyrene/toluene mixtures has been investigated by steady-state optical spectroscopy. The Q-band absorption spectra, as well as the fluorescence spectra, show a temperature-dependent red shift as a result of ligation of the porphyrin zinc center. The smallest aggregate that can account for the optical spectra and their concentration dependence is a symmetrical tetramer in which each zinc atom is ligated to a pyridyl substituent of a neighboring porphyrin molecule. The Soret band shows a splitting, which can be explained by applying simple exciton theory to the tetramer. The equilibrium constant and thermodynamic parameters for the monomer-tetramer equilibrium have been determined as K = (6.2 +/- 0.8) x 10(13) M-3, triangleH = -40 +/- 2 kCalM(-1), triangleS = 150 +/- 10 CalK(-1)M(-1), in agreement with tetramer formation.
引用
收藏
页码:11425 / 11431
页数:7
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