Isomeric triarylamine-ferrocene mixed-valence systems: Syntheses, structural-(spectro)electrochemical analysis, and theoretical calculations

Abstract

Six novel triarylamine (TAA)–ferrocenyl conjugates (1–6) were prepared and characterized using molecular spectroscopic and crystallographic methods. Different species with a corresponding valences of 1n+−6n+ (n = 0, 1) were investigated using cyclic voltammetry, UV–Vis–NIR spectroelectrochemistry, and quantum–chemical calculations. Electrochemical analysis of two groups of isomeric complexes (1–2) and complexes (3–6) revealed that the effective distance between redox–active ferrocenyl and TAA remarkably influenced the redox potential difference (ΔE). NIR peaked at 1142 and 1153 nm from singly oxidized complexes 1+ and 3+, thereby indicating that 1+ and 3+ were stable in CH2Cl2 solution and featured obvious IVCT characters. These findings were proved as NAr3 → Fc charge transfer by TDDFT predictions. Calculations of spin density distribution showed that the monocations 1+−6+ all exhibited remarkably identical charge distributions with dominant metal (Fc)-localized characteristics.