A Semiconducting Cationic Square-Grid Network with Fe-III Centers Displaying Unusual Dynamic Behavior

The synthesis, structure and properties of a 2D Fe-III network material of composition [Fe(O-bipy)(2)Cl](TCNQ)(2) (O-bipy = 4,4'-bipyridyl N,N'-dioxide; TCNQ = 7,7,8,8-tetracyanoquinodimethane) are presented. The structure consists of a square grid in which square pyramidal Fe-III centers are linked to four equivalent centers through O-bipy ligands. Pairs of TCNQ radical anions are located within rectangular cavities of the 2D network. The apical position on each Fe center is occupied by a chloride ion. Magnetic studies are indicative of weak antiferromagnetic coupling. Electrical conductivity measurements reveal that the compound is a semiconductor and on the basis of DFT calculations it is proposed that electrical conduction occurs via charge hopping between interlayer TCNQ anions. Mossbauer spectra indicate a rare example of the Goldanskii-Karyagin effect and are suggestive of unusual dynamic processes.