Synthesis, structure and optical limiting effect of two new nickel complexes containing strongly bound geometrically fixed multi-sulfur 1,2-dithiolene ligands showing remarkable near-IR absorption

Two new nickel complexes containing strongly bound multi-sulfur 1,2-dithiol ene ligands, [NBu4][Ni(bddt)(2)] 1 and [Ni(bddt)(2)] 2 (bddt = 4a,5,6,7,8,8 a-hexahydro-1,4-benzodithiin-2,3-dithiolate), have been synthesized and cha racterized by electrochemical measurements, IR and UV-VIS-NIR spectroscopie s. The optical limiting properties of these nickel complexes have been dete rmined with 32 ps laser pulses of 532 nm wavelength. The limiting threshold s of 1 and 2 are ca. 0.6 and 0.7 J cm(-2), respectively, which are comparab le to that observed in C-60. Such results show that the nickel dithiolene c omplexes may be new candidates for optical limiting applications. In additi on, the neutral complex [Ni(bddt)(2)] 2, which shows remarkable absorption in the near-IR region (epsilon = 63 000 dm(3) mol(-1) cm(-1) at 1035 nm) an d is an excellent candidate as a near-IR dye for Q-switching neodymium lase rs, has been additionally characterized by X-ray diffraction.