The doubly deprotonated form L2- of indigo = H2L can bind two Ru(acac)2 complex fragments in the cis (1) and trans configuration (2), as evidenced from crystal structure anal. While the latter type of N,O; N',O' coordination has been obsd. earlier, for example, with Ru(bpy)22+, leading to two equiv. six-membered ring chelates, the cis arrangement in 1 is obsd. here for the first time in a dinuclear complex, producing one five-membered ring chelate with N,N' coordination and one seven-membered chelate with O,O' coordination. The different structures of the isomers result in differing electrochem. and spectroelectrochem. (EPR, UV-visible-NIR) responses for various accessible charge states 1n and 2n, n = -, 0, +, 2+. The assocd. electronic structures were analyzed by DFT (structures, spin d.) and TD-DFT calcns. (electronic transitions), revealing mainly metal-based redn. but largely indigo ligand-based oxidn. of both neutral precursors. on SciFinder(R)
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