Pre-synthetic redox control of structure and properties in copper TTFtt coordination polymers

Abstract

Conductive coordination polymers (CPs) with sulfur-based ligands offer strong metal–ligand interactions and redox tunability, making them promising candidates for electronic applications. Tetrathiafulvalene-2,3,6,7-tetrathiolate (TTFtt) is a particularly attractive ligand. However, its strong metal–ligand covalency leads to rapid irreversible metal coordination, limiting control over structure and morphology. Here, we demonstrate structural control in Cu TTFtt CPs using a pre-synthetic redox control strategy. Two new copper-based CPs, CuTTFtt and Cu₂TTFtt, have been synthesized and thoroughly characterized from differentially oxidized TTFtt synthons. CuTTFtt forms a 1D chain, while Cu₂TTFtt adopts a 2D ribbon-like structure. Detailed spectroscopic studies confirm the structures of these materials as well as their ligand and metal oxidation states. Physical property measurements reveal that Cu₂TTFtt exhibits higher conductivity than CuTTFtt. Furthermore, Cu₂TTFtt also shows unusual diamagnetism which contrasts the paramagnetism observed in CuTTFtt and the related material NiTTFtt. Density functional theory (DFT) further elucidates the physical properties of these CPs and supports the observed conductivity trends. This study expands the structural landscape of TTFtt-based CPs and further establishes how redox-doping can tune CP structure and physical properties.