Department of Chemistry, The University of Burdwan, Golapbag, Burdwan, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2012 May;90:186-92. doi: 10.1016/j.saa.2012.01.031. Epub 2012 Jan 24.
The present paper highlights the UV-Vis and fluorescence spectroscopic studies on spontaneous non-covalent interaction between a designed monoporphyrin, namely, 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin (1) and fullerenes (C(60) and C(70)) in toluene medium. While UV-Vis studies reveal considerable amount of fullerene/1 interaction in ground state, steady state fluorescence study establishes remarkable quenching of fluorescence intensity of 1 in the presence of fullerenes C(60) and C(70). Stoichiometry of both the fullerene complexes of 1 is determined to be 1:1. The magnitude of average binding constant (K) values for C(70)/1 and C(60)/1 systems is estimated to be 8705 and 3440 dm(3) mol(-1), respectively, which also prove that moderate value of selectivity in binding between C(70) and C(60) complexes of 1 is resulted in our present work. The genetics of the photo-physical characteristics of fullerene/1 complexes get tremendous support from lifetime experiment, which signifies the importance of static quenching phenomenon for our presently investigated supramolecules. Life time experiment yields larger magnitude of charge separated rate constant for the fullerene/1 species in toluene. Theoretical calculations at molecular mechanics level evoke the single projection geometric structures for the C(60)/1 and C(70)/1 systems in vacuo which also proves that interaction between C(70) and 1 is governed by the dispersive forces associated with π-π interaction rather than electrostatic mechanism associated with charge transfer mechanism.
本文重点研究了在甲苯介质中设计的卟啉单体(即 2,3,7,8,12,13,17,18-八乙基-21H,23H-卟啉(1)与富勒烯(C(60)和 C(70))之间自发非共价相互作用的紫外可见和荧光光谱。虽然紫外可见研究表明在基态下存在大量的富勒烯/1 相互作用,但稳态荧光研究表明在富勒烯 C(60)和 C(70)存在下,1 的荧光强度显著猝灭。1 与两种富勒烯配合物的化学计量比均为 1:1。C(70)/1 和 C(60)/1 体系的平均结合常数(K)值的大小分别估计为 8705 和 3440 dm(3) mol(-1),这也证明了我们目前的工作中在 C(70)和 C(60)配合物之间存在中等程度的结合选择性。富勒烯/1 配合物的光物理特性的遗传得到寿命实验的极大支持,这表明静态猝灭现象对我们目前研究的超分子的重要性。寿命实验为我们在甲苯中的富勒烯/1 物种产生了更大的电荷分离速率常数。分子力学水平的理论计算唤起了 C(60)/1 和 C(70)/1 体系在真空中的单投影几何结构,这也证明了 C(70)与 1 之间的相互作用是由与π-π相互作用相关的分散力而不是与电荷转移机制相关的静电机制来控制的。