Charge density study of 2D two-electron multicentric bonded arrays of 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical anions

The main topic of the proposed research is study of study of two-electron multicentric (2e/mc) bonding between partially charged 7,7,8,8-tetracyanoquinodimethane (TCNQ) radical anions by X-ray charge density. In the studied systems, TCNQ radicals form ordered 2D arrays with long-range magnetic exchange interactions and conductivity extending in 2D. Fine details of the interaction, which determines bulk properties of these materials, can be studied by a combination of X-ray charge density, magnetic and electric measurements on single crystals (impedance spectroscopy, SQUID and EPR spectroscopy) and quantum chemical modelling (ab initio MP2 for isolated clusters, periodic DFT for crystal lattice). A series of salts of TCNQ with organic cations is studied. Some of interesting compounds have large unit cells, so diffraction to a high resolution (of 0.5 Å) can be achieved only using high-brilliance synchrotron radiation.