Molecular and electronic structure of a largely extended tetracyanoquinodimethane

We investigate the molecular structure and electronic properties of 15,15,16,16-tetracyano-6, 13-pentacenequinodimethane (TCPQ) using quantum-chemical methods. The molecule is predicted to be severely distorted from planarity adopting a butterfly-type structure. The analysis of the topology of the frontier orbitals justifies the decrease in the acceptor ability of extended TCNQs and assigns the first optical absorption observed for TCPQ to an intramolecular charge-transfer transition. Calculations on negatively charged TCPQ show that the molecule is planarized upon reduction.