Rigidification of a macrocyclic tris-catecholate scaffold leads to electronic localisation of its mixed valent redox product

Abstract

The catecholate groups in [{Pt(L)}₃(μ₃-tctq)] (H₆tctq = 2,3,6,7,10,11-hexahydroxy-4b,8b,12b,12d-tetramethyltribenzotriquinacene; L = a diphosphine chelate) undergo sequential oxidation to their semiquinonate forms by voltammetry, with ΔE_1/2 = 160–170 mV. The monoradical [{Pt(dppb)}₃(μ₃-tctq˙)]⁺ is valence-localised, with no evidence for intervalence charge transfer in its near-IR spectrum. This contrasts with previously reported [{Pt(dppb)}₃(μ₃-ctc˙)]⁺ (H₆ctc = cyclotricatechylene), based on the same macrocyclic tris-dioxolene scaffold, which exhibits partly delocalised (class II) mixed valency.