Directly Connected AzaBODIPY鈥揃ODIPY Dyad: Synthesis, Crystal Structure, and Ground- and Excited-State Interactions

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• 作者：Sunit Kumar ; Habtom B. Gobeze ; Tamal Chatterjee ; Francis D鈥橲ouza ; Mangalampalli Ravikanth
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：July 30, 2015
• 年：2015
• 卷：119
• 期：30
• 页码：8338-8348
• 全文大小：631K
• ISSN：1520-5215

文摘

Directly connected, strongly interacting sensitizer donor鈥揳cceptor dyads mimic light-induced photochemical events of photosynthesis. Here, we devised a dyad composed of BF₂-chelated dipyrromethene (BODIPY) directly linked to BF₂-chelated tetraarylazadipyrromethene (azaBODIPY) through the 尾-pyrrole position of azaBODIPY. Structural integrity of the dyad was arrived from two-dimensional NMR spectral studies, while single-crystal X-ray structure of the dyad provided the relative orientation of the two macrocycles to be 鈭?2掳. Because of direct linking of the two entities, ultrafast energy transfer from the ¹BODIPY* to azaBODIPY was witnessed. A good agreement between the theoretically estimated F枚rster energy transfer rate and experimentally determined rate was observed, and this rate was found to be higher than that reported for BODIPY鈥揳zaBODIPY analogues connected with spacer units. In agreement with the free-energy calculations, the product of energy transfer, ¹azaBODIPY* revealed additional photochemical events such as electron transfer leading to the creation of BODIPY^鈥?鈥揳zaBODIPY^{鈥⑩€?/sup> radical ion pair, more so in polar benzonitrile than in nonpolar toluene, as evidenced by femtosecond transient spectroscopic studies. Additionally, the spectral, electrochemical, and photochemical studies of the precursor compound azaBODIPY鈥揹ipyrromethane also revealed occurrence of excited-state events. In this case, electron transfer from the 1azaBODIPY* to dipyrromethane (DPM) yielded DPM鈥?鈥揳zaBODIPY鈥⑩€?/sup> charge-separated state. The study described here stresses the role of close association of the donor and acceptor entities to promote ultrafast photochemical events, applicable of building fast-response optoelectronic and energy-harvesting devices.}