Studies on photo-driven logic molecular devices with fast response

1.四吡啶并吩嗪桥联的Ru（II）-Os（III）混合价络合物经光辐照后，发现Ru（II）部分的MLCT态电子转移到Os（III）部分，时间常数为20 ps，效率很高。所得产物态Ru（III）-Os（II）混合价态的寿命大于100 ns。由于在该配合物中观察到的两个伪稳态Ru（II）-Os（III）和Ru（III）-Os（II）分别可以被视为逻辑态“0”和“1”，因此我们认为该配合物可以作为具有非常快响应（~ 100 GHz）的光驱动触发器分子。然而，“1”状态的照射，即，Ru（III）-Os（II）不能有效地形成“0”态。该分子的量子力学计算表明，两个MLCT态，即，（^3CT）Ru（II）-Os（III）和Ru（III）-（^3CT）Os（II）之间的相互作用非常强，以至于两个MLCT态之间的势垒不足以使它们局域化. DNA分子探针的光开关机理为了阐明作为一种优良的DNA探针的Ru（II）dppz（dppz= dipridophenazine）的光开关机理，测量了各种dppz衍生物的Ru（II）的发光性质。发现两个MLCT态的溶剂化能相差仅100 meV就可以实现发射峰能量的转换。这种急剧的开关主要是负责两个MLCT状态（1065毫电子伏）之间的异常弱的电子相互作用。

1. Charge-transfer type logic devices based on mixed-valence complexesWhen Ru(II)-Os(III) mixed-valence complex bridged with tetrapyridophenazine was photoirradiated, it was observed that electron transfer from MLCT state of Ru(II) moiety to Os(III) moiety occurs with time constant of 20 ps and with high efficiency (Ф〜1). The lifetime of the resultant product state, Ru(III)-Os(II) mixed-valence isomer state, was longer than 100 ns. Since two pseudo-stable states, Ru(II)-Os(III) and Ru(III)-Os(II), observed in this complex can be regarded as logical state, '0' and '1', respectively, we thought that this complex would work as photo-driving flip-flop molecule with very fast response (〜100GHz). However, the irradiation of '1' state, i.e., Ru(III)-Os(II), did not give '0' state, efficiently. The quantum mechanical calculation of this molecule indicated that two MLCT states, i.e., (^3CT)Ru(II)-Os(III) and Ru(III)-(^3CT)Os(II), so strongly interact each other that the barrier between the two MLCT states was not high enough to allow them to be localized.2. The mechanism of light-switching of DNA molecular probeTo clarify the mechanism of light-switching in Ru(II) dppz (dppz=dipyridophenazine) which is known to be an excellent DNA probe, the emission properties were measured for Ru(II) of various dppz derivatives. It is found out that only 100meV difference in solvation energy for between two MLCT states can switch the emission peak energy. Such sharp switching is mainly responsible for the unusually weak electronic interaction between two MLCT states (〜65 meV).