Pressure-Induced Conductivity in a Neutral Non-planar Spin-localized Radical

M. Souto, H. B. Cui, M. Peña-Álvarez, V. G. Baonza, H. O. Jeschke, M. Tomic, R. Valentí, D. Blasi, I. Ratera, C. Rovira, J. Veciana

J. Am. Chem. Soc., 2016, 138 (36), pp 11517–11525
DOI: 10.1021/jacs.6b02888

There is a growing interest in the development of single-component molecular conductors based on neutral organic radicals that are mainly formed by delocalized planar radicals, such as phenalenyl or thiazolyl radicals. However, there are no examples of systems based on non-planar and spin-localized C-centered radicals exhibiting electrical conductivity due to their large Coulomb energy (U) repulsion and narrow electronic bandwidth (W) that give rise to a Mott insulator behavior. Here we present a new type of non-planar neutral radical conductor attained by linking a tetrathiafulvalene (TTF) donor unit to a neutral polychlorotriphenylmethyl radical (PTM) with the important feature that the TTF unit enhances the overlap between the radical molecules as a consequence of short intermolecular S•••S interactions. This system becomes semiconducting upon the application of high pressure thanks to increased electronic bandwidth and charge reorganization opening the way to develop a new family of neutral radical conductors.