Dynamic Self-Assembly of Charge-Transfer Nanofibers of Tetrathiafulvalene Derivatives with F4TCNQ

One-dimensional charge-transfer nanostructures were constructed by the supramolecular coassembly of amphiphilic (Amph-TTF) and hydrophobic (TDD-TTF) tetrathiafulvalene (TTF) donor derivatives with the acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ), in appropriate solvent composition mixtures. Microscopic analyses show that TDD-TTF retains its self-assembled fibrillar morphology even in the charge-transfer state, whereas Amph-TTF undergoes a spherical to nanorod transition upon coassembly. Time-dependent optical spectroscopy studies have shown a spontaneous change in molecular organization in TDD-TTF-based donor-acceptor costacks, which suggests a dynamic behavior, in contrast to the kinetically stable amphiphilic TTF assemblies. We have also tried to get an insight into the observed time-dependent change in molecular packing of these nanostructures through spectroscopic analyses by commenting on whether the TTF-TCNQ pair is cofacially arranged or present in the classical herringbone (orthogonal) fashion. Furthermore, our two-probe electrical measurements showed that these charge-transfer fibers are conducting. A supramolecular approach that yields 1D charge-transfer nanostructures of donor and acceptor molecules will be an alternative to existing crystalline substances with high conductivity and hence can be a viable tool for nanoelectronics.