An aryl-fused redox-active tetrathiafulvalene with enhanced mixed-valence and radical-cation dimer stabilities
Schroder, Hendrik V. and Witte, Felix and Gaedke, Marius and Sobottka, Sebastian and Suntrup, Lisa and Hupatz, Henrik and Valkonen, Arto and Paulus, Beate and Rissanen, Kari and Sarkar, Biprajit and Schalley, Christoph A. – 2018
Molecular recognition of stable organic radicals is a relatively novel, but important structural binding motif in supramolecular chemistry. Here, we report on a redox-switchable veratrole-fused tetrathiafulvalene derivative VTTF which is ideally suited for this purpose and for the incorporation into stimuli-responsive systems. As revealed by electrochemistry, UV/Vis measurements, X-ray analysis, and electrocrystallisation, VTTF can be reversibly oxidised to the corresponding radical-cation or dication which shows optoelectronic and structural propterties similar to tetrathiafulvalene and tetrakis(methylthio)tetrathiafulvalene. However, theoretical calculations, variable temperature EPR, and NIR spectroscopy indicate that the dispersion-driven binding in the mixed-valence dimer (VTTF2)[radical dot]+ (KMV = 69 M-1 in CH2Cl2) and the radical-cation dimer (VTTF[radical dot]+)2 (KRC = 38 M-1 in CH3CN) is significantly enhanced by the additional veratrole [small pi]-surface in comparison to pristine tetrathiafulvalene.