Synthesis and Function of Crystalline-state Photoresponsive Metal Complexes with Active S-S Bond

在结晶状态下，铑双核配合物[(RhCp^*)_2(μ-CH_2)_2(μ-O_2SSO_2)](1)与一个光响应二亚硫酸基（μ-O_2SSO_2）和两个五甲基环戊二烯基配体（Cp^*=η^5-C_5Me_5）相互转化为[(RhCp^*)_2(μ-CH_2)_2(μ-O_2SOSO)](2)时发生100%可逆的单分子型T逆光变色。利用分步晶体结构分析可以直接跟踪光致变色。在本研究中，我们发现1的光反应是由510 nm光的吸收(由DFT计算分配的σ(S-S)到σ^*（S-S)和σ^*(Rh-Rh)轨道的电荷转移带）引发的，并包括两个重要过程：动力学控制的氧原子转移产生4个2的立体异构体和热力学控制的4个2的立体异构体之间的异构化产生最稳定的异构体。虽然四种立体异构体的生成速率受动力学控制，而四种立体异构体的居位分布受热力学控制，但这两个过程都受μ-O_2SSO_2或μ-O_2SOSO配体与Cp^*配体形成的反应腔之间的位阻调节。这两个过程的合作实现了一个有趣的立体定向氧原子重排，在室温下光反应的最后阶段只产生一个2的立体异构体。我们还确定了氧原子重排对两种晶体学独立的Cp^*配体（平行排列和垂直排列）旋转运动的影响。利用变温^13C CP/MAS NMR和四极性回声固态^2H NMR谱，测定了1中平行和垂直CP ^*配体的旋转活化能分别为30±3和10±1 kJ/mol，光照射后2中平行和垂直CP ^*配体的旋转活化能远低于1（分别为20±2和8±1 kJ/mol）。平行Cp^*在2中的活化能的大幅下降是由于分子应力通过立体定向氧原子重排而松弛，这表明Cp^*配体的旋转运动与光致变色相耦合。此外，我们还发现了一种新的具有n-丙基基团的非手性光致变色二硫代配合物[(RhCp^<Pro>)_2(μ-CH_2)(μ-O_2SSO_2)] （Cp^<Pro>=η^5- c_5me_4n -丙基）在手性晶体中的绝对不对称光异构化。该配合物在P2_12_12_1空间群中结晶，得到了含有P和m螺旋异构体的晶体。我们将这些手性晶体用与[(RhCp^*)_2(μ-CH_2)（μ-O_2SSO_2）相似的方法进行了结晶态光反应，得到了[RhCp^<Pro>)_2(μ-CH_2)(μ-OSOSO_2)]几乎定量的结果。所得μ-OSOSO_2配合物的e.e值为95%。少

In the crystalline state, the rhodium dinuclear complex[(RhCp^*)_2(μ-CH_2)_2(μ-O_2SSO_2)] (1) with a photoresponsive dithionite group (μ-O_2SSO_2) and two pentamethylcyclopentadienyl ligands (Cp^*=η^5-C_5Me_5) undergoes a 100% reversible unimolecular type T inverse photochromism upon interconversion to [(RhCp^*)_2(μ-CH_2)_2(μ-O_2SOSO)] (2). The photochromism can be followed directly by using stepwise crystal structure analysis.In this study, we found that the photoreaction of 1 was triggered by absorption of the 510 nm light (charge transfer band from σ(S-S)to σ^*(S-S)and σ^*(Rh-Rh)orbitals assigned by DFT calculation) and included two important processes:kinetically controlled oxygen-atom transfer to produce four stereoisomers of 2 and thermodynamically controlled isomerization between the four stereoisomers of 2 to afford the most stable isomer. Although the formation rate of the four stereoisomer products was kinetically controlled and the population of the four stereoisomers produc … More ed in the system was thermodynamically controlled, both processes were regulated by the steric hindrance between the μ-O_2SSO_2 or μ-O_2SOSO ligand and the reaction cavity formed by the Cp^* ligands. The cooperation of both processes achieved an intriguing stereospecific oxygen-atom rearrangement to produce only one stereoisomer of 2 at the final stage of the photoreaction at room temperature.We also determined the effect of the oxygen-atom rearrangement on the rotational motion of the two crystallographibally independent Cp^* ligands (parallel and perpendicular arrangement). Using variable-temperature ^13C CP/MAS NMR and quadrupolar echo solid-state ^2H NMR spectroscopies, before photoirradiation, the activation energies for the rotation of the parallel and perpendicular Cp^* ligands in 1 were determined to be 30±3 and 10±1 kJ/mol, respectively, and after photoirradiation, in 2, they were much lower than those in 1 (20±2 and 8±1 kJ/mol, respectively). The large decrease in the activation energy for the parallel Cp^* in 2 is attributed to the relaxation of molecular stress via a stereospecific oxygen-atom rearrangement, which suggests that the rotational motion of the Cp^* ligands is coupled to the photochromism.Furthermore, we have found an absolute asymmetric photoisomerization of a new achiral photochromic dithionite complex having n-propyl moieties [(RhCp^<Pro>)_2(μ-CH_2)(μ-O_2SSO_2)] (Cp^<Pro>=η^5-C_5Me_4n-Propyl) in chiral crystals. This complex is crystallized in the space group of P2_12_12_1 and gives both crystals containing the helical isomers of P and M.We performed a crystalline-state photoreaction by using these chiral crystals in similar way to [(RhCp^*)_2(μ-CH_2)(μ-O_2SSO_2)] and obtained [RhCp^<Pro>)_2(μ-CH_2)(μ-OSOSO_2)] almost quantitatively. The obtained μ-OSOSO_2 complex has an e.e value of 95%. Less