Three Redox States of a Diradical Acceptor−Donor−Acceptor Triad: Gating the Magnetic Coupling and the Electron Delocalization

The diradical acceptor–donor–acceptor triad 1••, based on two polychlorotriphenylmethyl (PTM) radicals connected through a tetrathiafulvalene(TTF)–vinylene bridge, has been synthesized. The generation of the mixed-valence radical anion, 1•–, and triradical cation species, 1•••+, obtained upon electrochemical reduction and oxidation, respectively, was monitored by optical and ESR spectroscopy. Interestingly, the modification of electron delocalization and magnetic coupling was observed when the charged species were generated and the changes have been rationalized by theoretical calculations.This work was supported by the DGI grant (CTQ2013-40480- R), the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), and the Generalitat de Catalunya (grant 2014-SGR-17). ICMAB acknowledges support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496). M.S. is enrolled in the Material Science Ph.D. program of UAB and is grateful to MEC for a FPU predoctoral grant. S.V. and M.F. are thankful to the LabEx-Chemistry of Complex Systems for postdoctoral grants (ANR-10-LABX-0026CSC) and to the regional High-Performance Computing (HPC) center in Strasbourg for computational resources. We thank Amable Bernabé for the MALDI spectroscopy.Peer reviewe

Understanding the Influence of the Electronic Structure on the Crystal Structure of a TTF-PTM Radical Dyad

The understanding of the crystal structure of organic compounds, and its relationship to their physical properties, have become essential to design new advanced molecular materials. In this context, we present a computational study devoted to rationalize the different crystal packing displayed by two closely related organic systems based on the TTF-PTM dyad (TTF = tetrathiafulvalene, PTM = polychlorotriphenylmethane) with almost the same molecular structure but a different electronic one. The radical species (1), with an enhanced electronic donor–acceptor character, exhibits a herringbone packing, whereas the nonradical protonated analogue (2) is organized forming dimers. The stability of the possible polymorphs is analyzed in terms of the cohesion energy of the unit cell, intermolecular interactions between pairs, and molecular flexibility of the dyad molecules. It is observed that the higher electron delocalization in radical compound 1 has a direct influence on the geometry of the molecule, which seems to dictate its preferential crystal structure.This work was supported by the DGI grant (CTQ2013- 40480-R), the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), the EU ITN iSwitch 642196, the NANO2FUN Project No. 607721 and the Generalitat de Catalunya (grant 2014-SGR-17). ICMAB acknowledges support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV- 2015-0496). S.V. is thankful to the LabEx-Chemistry of Complex Systems for a post-doctoral grant (ANR-10-LABX-0026CSC) and to the regional High-Performance Computing (HPC) center in Strasbourg for computational resources. M.S. is enrolled in the Material Science Ph.D. program of UAB and is grateful to MEC for a FPU predoctoral grant.Peer reviewe