Syntheses, characterization and non-linear optical properties of nickel complexes of multi-sulfur 1,2-dithioiene with strong near-IR absorption

A series of new nickel complexes with multi-sulfur 1,2-dithiolene ligands have been synthesized and characterized by electrochemical measurements, EPR, IR and UV–VIS spectroscopies. One of the typical structures for the neutral complex of [Ni(phdt)2]2(phdt = 5,6-dihydro-5-phenyl-l,4-dithiin-2,3-dithiolate) was obtained by X-ray structure determination. Electrical conductivities measured for compacted pellets range from 1.4 × 10–8 to 1.4 × 10–5 S cm–1. These complexes show intense absorptions in the near-IR region. The third-order non-linear optical susceptibilities, χ(3), for three of the complexes have been determined to be of the order of 10–11 esu.