Preparation and Photochemical Behavior of Organoruthenium Derivatives of Photochromic Dithienylethene (DTE): DTE−(RRuLm)n (RRuLm = (η6-C6H5)Ru(η5-C5Me5), (η6-C6H5)RuCl2(PPh3), (η5-C5Me4)Ru(CO)2; n = 1, 2)†

A series of organoruthenium complexes containing photochromic 1,2-di(2-methylthien-3-yl)-3,3,4,4,5,5-hexafluorocyclopentene fragments (DTE), DTE−(RRuLm)n (RRuLm = (η6-C6H5)Ru(η5-C5Me5) (I): n = 1 (3), 2 (4); (η6-C6H5)RuCl2(PPh3) (II): n = 1 (10), 2 (11); (η5-C5Me4)Ru(CO)2 (III): n = 1 (25), 2 (24); substituted at the 5-position of the thiophene ring), are prepared and characterized by 1H NMR and UV−vis spectroscopy, and molecular structures of the 1:2 adducts 4, 11, and 24 are determined by X-ray crystallography, which reveals the antiparallel conformation of the two thiophene rings suitable for photocyclization, causing the photochromism. It is revealed that the metalated DTE derivatives show photochromic behavior through the photochemical, electrocyclic conrotatory ring-closing and -opening processes in a manner analogous to the organic counterparts, but the efficiency of the photochromic processes is dependent on the attached metal fragments. The cationic Cp*Ru(η6-arene)-type (I) and neutral Cp*Ru(CO)2Cl-type complexes (III) show photochromic behavior (content of the closed isomers at the UV photostationary states: 25−88%), and subsequent visible light irradiation of the equilibrated mixtures reverts the process to afford the open forms quantitatively. The ring-closing and -opening processes are reversible and can be repeated without notable deterioration. As for the series of Ph derivatives of I (1, 3, and 4), metalation improves the efficiency of the ring-closing process. In contrast to these derivatives, no significant photochromic behavior is noted for the benzo-fused derivatives of I, and UV irradiation of II (10 and 11) causes irreversible dissociation of the arene ligand (DTE).本研究制备了一系列含有光致变色1,2-二(2-甲基噻吩-3-基)-3,3,4,4,5,5-六氟环戊烯片段（DTE）的有机钌配合物，其通式为DTE−(RRuLm)n，其中RRuLm分别为：(η⁶-C₆H₅)Ru(η⁵-C₅Me₅)（I型，n=1时对应产物3，n=2时对应产物4）；(η⁶-C₆H₅)RuCl₂(PPh₃)（II型，n=1时对应产物10，n=2时对应产物11）；(η⁵-C₅Me₄)Ru(CO)₂（III型，n=1时对应产物25，n=2时对应产物24），上述配合物均在噻吩环的5位发生取代。采用氢核磁共振（¹H NMR）谱与紫外-可见（UV−vis）分光光度法对所合成的配合物进行了表征，并通过X射线单晶衍射法（X-ray crystallography）确定了1:2加合物4、11与24的分子结构，结果显示两个噻吩环呈适配光环化反应的反平行构象，这正是该类配合物产生光致变色行为的根源。研究表明，金属化的DTE衍生物可通过光化学诱导的电环化顺旋闭环与开环过程展现光致变色行为，其机制与有机同类物类似，但光致变色过程的效率取决于所连接的金属片段。阳离子型五甲基环戊二烯基（Cp*）Ru(η⁶-芳烃)类配合物（I型）与中性Cp*Ru(CO)₂Cl类配合物（III型）均展现出光致变色行为，紫外光稳态下闭环异构体的占比为25%~88%；对平衡后的混合体系进行后续可见光辐照，可定量将其转化为开环形式。闭环与开环过程具有可逆性，可多次重复且无明显降解。针对I型的苯基衍生物系列（产物1、3与4），金属化提升了闭环过程的效率。与之形成对比的是，I型的苯并稠合衍生物未表现出明显的光致变色行为；而对II型配合物（产物10与11）进行紫外光辐照时，会导致芳烃配体（DTE）发生不可逆解离。