Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, PR China.
Chemphyschem. 2010 Jan 18;11(1):229-35. doi: 10.1002/cphc.200900556.
A supramolecular dyad, BP-(amidinium-carboxylate)-NBD is constructed, in which benzophenone (BP) and norbornadiene (NBD) are connected via an amidinium-carboxylate salt bridge. The photophysical and photochemical properties of the assembled BP-(amidinium-carboxylate)-NBD dyad are examined. The phosphorescence of the BP chromophore is efficiently quenched by the NBD group in BP-(amidinium-carboxylate)-NBD via the salt bridge. Time-resolved spectroscopy measurements indicate that the lifetime of the BP triplet state in BP-(amidinium-carboxylate)-NBD is shortened due to the quenching by the NBD group. Selective excitation of the BP chromophore results in isomerization of the NBD group to quadricyclane (QC). All of these observations suggest that the triplet-triplet energy transfer occurs efficiently in the BP-(amidinium-carboxylate)-NBD salt bridge system. The triplet-triplet energy transfer process proceeds with efficiencies of approximately 0.87, 0.98 and the rate constants 1.8x10(3) s(-1), and 1.3x10(7) s(-1) at 77 K and room temperature, respectively. The mechanism for the triplet-triplet energy transfer is proposed to proceed via a "through-bond" electron exchange process, and the non-covalent bonds amidinium-carboxylate salt bridge can mediate the triplet-triplet energy transfer process effectively for photochemical conversion.
构建了一个超分子偶联物 BP-（脒基-羧酸酯）-NBD，其中苯甲酮（BP）和降冰片二烯（NBD）通过酰胺基-羧酸酯盐桥连接。研究了组装的 BP-（脒基-羧酸酯）-NBD 偶联物的光物理和光化学性质。BP-（脒基-羧酸酯）-NBD 中的 NBD 基团通过盐桥有效地猝灭 BP 发色团的磷光。时间分辨光谱测量表明，BP-（脒基-羧酸酯）-NBD 中 BP 三重态的寿命由于 NBD 基团的猝灭而缩短。BP 发色团的选择性激发导致 NBD 基团异构化为四环烷（QC）。所有这些观察结果表明，三重态-三重态能量转移在 BP-（脒基-羧酸酯）-NBD 盐桥体系中有效地发生。三重态-三重态能量转移过程的效率约为 0.87、0.98，在 77 K 和室温下的速率常数分别为 1.8x10(3) s(-1)和 1.3x10(7) s(-1)。提出三重态-三重态能量转移的机制是通过“键间”电子交换过程进行的，非共价键酰胺基-羧酸酯盐桥可以有效地介导三重态-三重态能量转移过程，用于光化学转化。
