Optical-limiting properties of neutral nickel dithiolenes

We report the observation of optical-limiting effects in benzene solutions of two neutral nickel complexes with multi-sulfur 1,2 dithiolene ligands, [Ni(medt)(2)] 1 (medt = 5,6-dihydro-6-methyl-1,4-dithiin-2,3-dithiolate) and [Ni(phdt)(2)] 2 (phdt = 5,6-dihydro-5-phenyl-1,4-dithiin-2,3-dithiolate). The limiting effects were observed with nanosecond and picosecond laser pulses. The limiting thresholds of complexes 1 and 2 were approximate to 0.3J/cm(2), measured with the ps laser pulses at 532 nm. The linear absorption spectra of the two complexes indicated that their limiting response should cover the visible and near-infrared region (up to 900 nm). Both ps time-resolved pump-probe and Z-scan experiments revealed that the limiting effects should originate from excited-state absorption and refraction superconductors [16-20]. To our best knowledge, no investigations have been carried out on the optical-limiting properties of dithiolene complexes. Here we report the observation of optical-limiting effects in two neutral nickel complexes with multi-sulfur dithiolene ligands, [Ni(medt)(2)](medt = 5,6 dihydro-6-methyl-1,4-dithiin-2,3-dithiolate) 1 and [Ni(phdt)(2)] (phdt = 5,6-dihydro-5-phenyl-1,4-dithinn-2,3-dithiolate) 2. The observation has been carried out by ns and ps laser pulses at a wavelength of 532 nm. The mechanisms leading to the observed limiting effects have also been investigated