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

在晶体状态下，铑双核配合物[（RhCp^*）_2（μ-CH_2）_2（μ-O_2SSO_2）]（1）具有光响应性连二亚硫酸根基团（μ-O_2SO_2）和两个五甲基吡啶配体（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T型逆光致变色。通过逐步晶体结构分析，我们发现化合物1的光致变色反应是由510 nm光的吸收引发的（通过DFT计算指定的从σ（S-S）到σ^*（S-S）和σ^*（Rh-Rh）轨道的电荷转移带），包括两个重要过程：动力学控制的氧-原子转移以产生2的四种立体异构体，并在2的四种立体异构体之间进行手性控制的异构化以提供最稳定的异构体。虽然四种立体异构体产物的形成速率受动力学控制，且四种立体异构体产物的数量在一定范围内变化， ...更多信息 体系中的Cp ^* 艾德化是热力学控制的，这两个过程都受μ-O_2SSO_2或μ-O_2SOSO配体与Cp^* 配体形成的反应空腔之间的空间位阻调节。这两个过程的协同作用实现了一个有趣的立体特异性氧原子重排，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个晶体学独立的Cp^* 配体（平行和垂直排列）的旋转运动的影响。利用变温^13 C CP/MAS NMR和四极回波固体^2 H NMR光谱，在光照射前，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，而在光照射后，2中的活化能远低于1中的活化能（分别为20±2和8±1 kJ/mol）。2中平行Cp^* 的活化能的大幅度降低归因于分子应力通过立体定向氧原子重排的弛豫，这表明Cp^* 配体的旋转运动与光致变色耦合.此外，我们还发现了一种新的非手性光致变色连二亚硫酸根配合物[（RhCp^<Pro>）_2（μ-CH_2）（μ-O_2SSO_2）]（Cp^<Pro>=η^5-C_5 Me_4 n-Propyl）在手性晶体中的绝对不对称光致异构化.该配合物的空间群为P2_12_12_1，晶体中含有P和M的螺旋异构体。我们用类似于[（RhCp^*）_2（μ-CH_2）（μ-O_2SSO_2）]的方法对这些手性晶体进行了晶态光反应，得到了几乎定量的[RhCp^*<Pro>）_2（μ-CH_2）（μ-OSOSO_2）]。所得的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