A structurally characterised redox pair involving an indigo radical: indigo based redox activity in complexes with one or two [Ru(bpy)(2)] fragments

作者：Chatterjee Madhumita; Mondal Prasenjit; Beyer Katharina; Paretzki Alexa; Kaim Wolfgang^*; Lahiri Goutam Kumar^*

来源：Dalton Transactions, 2017, 46(15): 5091-5102.

DOI：10.1039/c7dt00055c

The reaction between indigo, H(2)Ind, and {Ru(bpy)(2)(EtOH)(2)}(2+) in EtOH/NaOH produced the compounds [Ru(bpy)(2)(mu-Ind)]ClO4 [1] ClO4, rac-{[Ru(bpy)(2)](2)(mu-Ind)}(ClO4)(2) [2](ClO4)(2), and meso-{[Ru(bpy)(2)](2)(mu-Ind)}(ClO4)(3) [2](ClO4)(3), which were structurally characterised, the latter as the first stable, isolable radical complex of indigo. The redox pair 2(2+)/2(3+) showed little structural difference, as confirmed using DFT calculations. The redox series 1(n) and 2(n) were investigated using voltammetry and spectroelectrochemistry (EPR, UV-vis-NIR). Remarkably, the EPR results for 1, 1(2+), 2(+) and 2(3+) revealed mostly ligand based spin in ruthenium(II) complexes of the indigo-derived radical ligands HInd(center dot 2-), HInd(center dot), Ind(center dot 3-) and Ind(center dot-), in agreement with the DFT calculated spin densities. The dominance of the frontier orbitals by the metalstabilised indigo chromophore was also confirmed via the TD-DFT based assignment of near-infrared absorptions as intra-indigo or ligand-to-ligand charge transfer transitions.

• 出版日期2017-4-21