RETRACTED: Electronically Weakly Coupled 4,4'-Divinylazoarylenes-Bridged Diruthenium Complexes Featuring Two Ru(PiPr3)2Cl(CO) Entities

Abstract

We report here on novel four 4,4'-divinylazoarylenes-bridged diruthenium complexes featuring two Ru(PiPr3)2Cl(CO) entities with a general formula of [{Ru(PiPr3)2Cl(CO)}2(μ-{CH=CH-Ar}2-N=N-4,4')]; Ar = C6H4; [1azo], C6H3-2-Me; [2azo], C6H3-(Me)2-2,6; [3azo], and C6H2-(iPr)2-2,6; [4azo]. Those five-coordinated, square-pyramidal, 16-valence electrons (VEs) type-complexes [1azo]-[4azo] were successfully synthesized by stereo-and regiospecific insertion of the Ru-H bond of the hydrido substrate RuH(PiPr3)2Cl(CO) into the two terminal acetylenic bonds of the corresponding 4,4'-diethynylated azoarylenes [L1]-[L4]. They were routinely characterized in their neutral state by traditional IR, UV/Vis and NMR spectroscopic techniques, and in their two-closely accessible oxidized states by IR, UV/Vis/NIR spectroelectrochemistry along with electrochemical techniques as well as by (TD)-DFT calculations. Detailed electrochemical studies on these complexes and IR, UV/Vis/NIR spectro(electro)scopic characterization of their oxidized forms along with (TD)-DFT calculations revealed to massive 4,4'-divinylazobenzene linker contributions to the two redox processes in addition to noteworthy negligible electronic interaction “communication” between the two remote redox-active end-groups, rendering them as unique weakly coupled borderline class II / I MV systems in accordance to the Robin and Day classification. Incorporating the four bulky iPr substituents into the ortho-positions of the 4,4'-divinylazobenzene linker results to a significant decrease in the tendency of the co-planarity of the bridge.