New Symmetrical and Unsymmetrical Nickel-dithiolene Complexes Useful as Near-IR Dyes and Precursors of Sulfur-Rich Donors.

Abstract Novel symmetrical and unsymmetrical nickel dithiolene complexes based on a new ligand R2timdt (the -1 charged 1,3-dialkylimidazolidine-2,4,S-trithione) and dmit or mnt (dmit = 2-thioxo-1,3-dithiole-4,5-dithiolate; mnt = maleonitriledithiolate) useful as NIR-dyes and electrochromic materials in the 880-1400 nm region arc described here. The R2 timdt ligand, where N-electron donor atoms of the imidazoline ring are forced into co-planarity with the dithiolene ring, revealed to be valuable in shiftiig the low energy transition typical of this class of complexes in a region of remarkable interest for near-IR dyes, while stability was maintained. The symmetrical neutral complexes absorb very strongly at approximately 1000 nm, region of special interest for NIR-dyes in order to be used in Q-switching Neodymium lasers, which operate at 1064 nm. Moreover these complexes work as switchable NIR-dyes, since the absorption is shifted to approximately 1400 nm on reversible reduction. In the unsymmetrical nicke...