Spectroscopic and theoretical insights on fullerene-octaethylporphyrin self assembled non-covalent conjugates studied in solution

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• 作者：Partha Mukherjee ; Sumanta Bhattacharya ; ^{sum_9974@rediffmail.com}
• 关键词：Fullerenes ; Octaethylporphyrin free base ; UV&ndash ; Vis and fluorescence spectroscopic investigations ; Binding constants ; Quantum mechanical calculations
• 刊名：Spectrochimica Acta Part A ; Molecular and Biomolecular Spectroscopy
• 出版年：2012
• 期刊代码：99_13861425
• 类别：ch
• 出版时间：May, 2012
• 卷：90
• 期：Complete
• 页码：186-192
• 文件大小：756 K

摘要

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 (C₆₀ and C₇₀) 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 C₆₀ and C₇₀. Stoichiometry of both the fullerene complexes of 1 is determined to be 1:1. The magnitude of average binding constant (K) values for C₇₀/1 and C₆₀/1 systems is estimated to be 8705 and 3440 dm³ mol^鈭?, respectively, which also prove that moderate value of selectivity in binding between C₇₀ and C₆₀ 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 C₆₀/1 and C₇₀/1 systems in vacuo which also proves that interaction between C₇₀ and 1 is governed by the dispersive forces associated with 蟺-蟺 interaction rather than electrostatic mechanism associated with charge transfer mechanism.