Electronic and optical properties of new synthesized TTF-based azine derivatives – Experimental and theoretical study

• Two electroactive azine ligands were prepared.
• Occurrence of an intramolecular charge transfer (ICT) band between the donor and acceptor fragments.
• The intermolecular interaction in crystal structure does not affect the HOMO and LUMO orbitals present in isolated molecule.

The synthesis and detailed characterization of two tetrathiafulvalene-appended azine derivatives, namely 2-([2,2′-bi(1,3-dithiolylidene)]-4-yl)-6-((2,4-dimethylphenyl)hydrazono) methyl)pyridine (L1) and 5-([2,2′-bi(1,3-dithiolylidene)]-4-yl)-2-((2,4-dimethylphenyl)hydrazono) methyl)pyridine (L2) are described. The crystal structure of ligand L2 indicates that the mentioned molecule is completely planar with the presence of a strong intramolecular N1H1⋯N3 hydrogen bonding. The quantum chemical calculations show that the intermolecular interaction in crystal structure does not affect the HOMO and LUMO orbitals present in isolated molecule. The optical properties of these ligands indicate the presence of intramolecular charge transfer band in the case of ligand L2 while the electrochemical behavior of the two compounds indicates that they are valuable candidates for the construction of crystalline radical cation salts.