Optical-limiting properties of neutral nickel dithiolenes

Abstract

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 ≈ 0.3 J/cm2, 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.