title: An unprecedented photochromic system with cis-oriented dithienyl-dithiolenes supported by metal chelation.
abstract: 4,5-Bis(2-methyl-5-phenylthiophen-3-yl)-1,3-dithiol-2-one (L1o) was elaborately designed to afford dithienyl-dithiolene as a new photochromic ligand. We describe herein the preparation and characterization of unprecedented photochromic dithienyl-dithiolene complexes with cis-orientation of dithienylethene (DTE) stabilized by metal chelation instead of conventional cyclopentene. The treatment of L1o with sodium methoxide in methanol afforded a disodium salt of dithiolate dianion, which reacts with M(dppe)Cl2(dppe = 1,2-bis(diphenylphosphino)ethane, M = Ni, Pd) to give neutral compounds M(dppe)(dithiolate) as established by X-ray crystallography. The reaction of L1o with NiCl2in the presence of sodium methoxide allows the isolation of an anionic nickel(ii) bis(dithienyl-dithiolene) complex with photochemical inertness. In contrast, the corresponding reaction with ZnCl2afforded a dianionic zinc(ii) complex chelated by two dianionic dithienyl-dithiolenes, which displays stepwise photocyclization upon irradiation with UV light at 312 nm as demonstrated experimentally and theoretically. Only when dithienyl-dithiolene behaves as a dicationic ligand instead of neutral or monoanionic species, it is possible to achieve reversible photochromism in the corresponding metal complexes.
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China. czn@fjirsm.ac.cn and Key Laboratory of Pesticide & Chemical Biology, College of Chemistry, Central China Normal University, Wuhan 430079, China. chshliu@mail.ccnu.edu.cn.
authors.forename: Jiang
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China. czn@fjirsm.ac.cn.
authors.forename: Lin-Xi
authors.initials: LX
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China. czn@fjirsm.ac.cn.
authors.forename: Jin-Yun
authors.initials: JY
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China. czn@fjirsm.ac.cn.
authors.forename: Jin-Xiang
authors.initials: JX
authors.lastname: Chen
authors.affiliation: Key Laboratory of Pesticide & Chemical Biology, College of Chemistry, Central China Normal University, Wuhan 430079, China. chshliu@mail.ccnu.edu.cn.
authors.forename: Sheng-Hua
authors.initials: SH
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, China. czn@fjirsm.ac.cn.
authors.forename: Zhong-Ning
authors.identifier: http://orcid.org/0000-0003-3589-3745
authors.initials: ZN
authors.lastname: Chen