Light-controlled ion switching:: Direct observation of the complete nanosecond release and microsecond recapture cycle of an azacrown-substituted [(bpy)Re(CO)3L]+ complex
Light-controlled ion switching:: Direct observation of the complete nanosecond release and microsecond recapture cycle of an azacrown-substituted [(bpy)Re(CO)3L]+ complex
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DOI：
10.1021/jp0469214
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发表时间：
2004-10-21
影响因子：
2.9
通讯作者：
Moore, JN
中科院分区：
文献类型：
--
作者：
Lewis, JD;Perutz, RN;Moore, JN
[(bpy)Re(CO)(3)L](+) 络合物（bpy = 2,2'-联吡啶），其中 L 包含氮杂冠醚（MacQueen, D. B.; Schanze, K. S. J. Am. Chem. Soc. 1991, 113, 6108），如所观察到的，充当与氮杂冠结合的碱金属和碱土金属阳离子的可逆光控开关直接通过时间分辨紫外可见分光光度法。激发金属络合形式 [(bpy)Re(CO)(3)L](+)-Mn+ 的金属到配体电荷转移 (MLCT) 状态，导致 Mn+ = Li+、Na+、Ca2+ 和 Ba2+ 在纳秒时间尺度上释放阳离子。 Li+和Na+的释放速度比Ca2+和Ba2+的释放速度快；相比之下，Mg2+则不会被释放。衰变至基态后，[(bpy)Re(CO)(3)L](+) 在微秒时间尺度上重新捕获金属阳离子以恢复起始热平衡。对于Li+和Na+，观察到多步重结合机制，其中阳离子最初附着在氮杂冠氮原子上，然后结合到氮杂冠环内的平衡位置。阳离子释放和重新捕获循环中的激发态和其他中间体已被直接实时观察，并且它们的衰变速率常数已被确定为阳离子特性的函数，从而能够为这种通用分子设计开发通用的光控阳离子切换机制。
A [(bpy)Re(CO)(3)L](+) complex (bpy = 2,2'-bipyridine) in which L contains an azacrown ether (MacQueen, D. B.; Schanze, K. S. J. Am. Chem. Soc. 1991, 113, 6108) acts as a reversible light-controlled switch of alkali and alkaline earth metal cations bound to the azacrown, as observed directly by time-resolved UV-vis spectroscopy. Excitation to the metal-to-ligand charge-transfer (MLCT) state of the metal-complexed form, [(bpy)Re(CO)(3)L](+)-Mn+, results in cation release on the nanosecond time scale for Mn+ = Li+, Na+, Ca2+, and Ba2+. with Li+ and Na+ being released more rapidly than Ca2+ and Ba2+; by contrast, Mg2+ is not released. After decay to the ground state, [(bpy)Re(CO)(3)L](+) recaptures metal cations on the microsecond time scale to restore the starting, thermal equilibrium. A multistep rebinding mechanism is observed for Li+ and Na+, in which the cation attaches initially to the azacrown nitrogen atom before binding to the equilibrium position within the azacrown ring. The excited states and other intermediates in the cation release-and-recapture cycle have been observed directly in real time, and their decay rate constants have been determined as a function of cation identity, enabling a generalized light-controlled cation-switching mechanism to be developed for this generic molecular design.