Enantio-Recognition and Charge Transfer Complex Formation Involving Tetrathiafulvalene-Appended Chiral 1,2-Cyclohexane-Diamine: An Integrated Experimental and Theoretical Study

Abstract

In this work, we exploit the electronic features of tetrathiafulvalene (TTF) as a backbone in synthesizing chiral derivatives. The aim is to make use of TTF's well-known and unique redox and semiconducting properties in the fields of enantio-selective recognition and chiral charge transfer (CT) complex preparation, with the ultimate objective of obtaining devices with various potential applications, ranging from plasmonics to quantum computing. In particular, both cyclohexane-bis (TTF-amide)–based enantiomers 1-(S,S) and 1-(R,R), stable under an oxidation regime, have been selected, and under these conditions, the electrochemical enantiospecific response of the four possible systems, coming from the combination with L- and D-tartaric acid, respectively, was tested. The 1:tartaric acid adducts show lower oxidation potentials than the pristine 1, together with clear enantio-discrimination demonstrated by sizeable potential differences in the range of 29–46 mV between the diastereomeric adducts. Because the oxidation potential of 1 suggests the possibility of the formation of CT complexes, impedance and FT-IR spectra were recorded to confirm this hypothesis in the case of the CT complex 1:I₂. The experimental results obtained through the FT-IR analysis were also compared with the theoretical results deriving from the DFT-based calculations.