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Probing electronic structure of [Ru(L1)2]Z (z = 0, 1+ and 2+) (H2L1: a tridentate 2-aminophenol derivative) complexes in three ligand redox levels

Abstract

Aerobic reaction between [RuII(DMSO)4Cl2], a redox-active 2-aminophenol-based ligand (H2L1: 2-[2-(benzylthio)phenylamino]-4,6-di-tert-butylphenol) and Et3N in MeOH under refluxing conditions, afforded a purple complex [Ru(L1)2] (S = 0). Structural analysis reveals that the tridentate ligand coordinates in a mer conformation providing distorted octahedral RuN2O2S2 coordination. Cyclic voltammetry on 1 in CH2Cl2 reveals the accessibility of the monocation, dication and monoanion forms. Reddish purple monocation [Ru(L1)2](PF6)•CH2Cl2 ([1OX1](PF6)•CH2Cl2; S = 1/2) and green dication [Ru(L1)2](BF4)2•H2O ([1OX2](BF4)2•H2O; S = 0) have been isolated through chemical oxidation of 1 in CH2Cl2 by [FeIII(5-C5H5)2](PF6) and AgBF4, respectively. Structural analysis of the single crystals of the monocation and the dication with compositions [1OX1](PF6)•CH2Cl2•H2O (2) and [1OX2](BF4)2•1.7H2O (3), respectively, has been done. Metrical (metal-ligand and ligand backbone) parameters, values of metrical oxidation states of coordinated ligands, 1H NMR spectra of 1 and [1OX2](BF4)2•H2O, EPR spectra of [1OX1](PF6)•CH2Cl2, X-ray photoelectron and UV-VIS-NIR spectra of 1–3, spin population analysis from broken-symmetry (BS) density functional theory (DFT) calculations and quasi-restricted orbitals (QROs) analysis have allowed us to assign the electronic structure of the complexes. The complexes exhibit highly covalent metal-ligand interactions. The electronic states of 1, [1OX1]1+ and [1OX2]2+ are best described as [RuII{(LISQ)•−}2] ↔ [RuIII{(LAP)2−}{(LISQ)•−}] (S = 0), [RuIII{(LISQ)•−}2]1+ (S = 1/2) and [RuII{(LIBQ)0}2]2+ ↔ [RuIII{(LISQ)•−}{(LIBQ)0}]2+ (S = 0), respectively. Notably, all the redox processes are ligand-centred. Absorption spectral properties have been rationalized, based on time-dependent (TD)-DFT calculations. For 1, the appearance of IVCT band at 1100 nm supports its Class II-III (borderline) ligand-based mixed-valence character.

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Article information


Submitted
02 Sep 2020
Accepted
07 Oct 2020
First published
07 Oct 2020

Dalton Trans., 2020, Accepted Manuscript
Article type
Paper

Probing electronic structure of [Ru(L1)2]Z (z = 0, 1+ and 2+) (H2L1: a tridentate 2-aminophenol derivative) complexes in three ligand redox levels

A. Saha, A. Rajput, P. Gupta and R. Mukherjee, Dalton Trans., 2020, Accepted Manuscript , DOI: 10.1039/D0DT03074K

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