Probing Charge Delocalization in Solid State Polychromophoric Cation Radicals Using X-ray Crystallography and DFT Calculations

Abstract

Assessing the charge delocalization in polychromophoric assemblies is a critical step toward designing novel charge transfer materials. Triptycene-based materials are particularly attractive, owing to their unique packing arrangement in the solid state. Here, we systematically probe, both experimentally (with X-ray crystallography) and theoretically (using Density Functional Theory, DFT), the extent of cationic charge (i.e., hole) delocalization in a set of triptycene derivatives with one, two, and three electron-rich 1,2-dimethoxybenzenoid (veratrole) rings. We demonstrate that the amount of charge at each veratrole can be deduced from experiment by analysis of the oxidation-induced bond length changes in comparison with a model compound containing one veratrole ring as a reference. In contrast, DFT calculations provide not only oxidation-induced structural reorganization, but also the charge distribution with the aid of natural population analysis. A comparative analysis shows that both experiment and t...