Two novel anion cluster compounds with a planar 'open' structure [Et4N](2)[MS4Cu4(SCN)(4)(2-pic)(4)] (M = W, Mo; 2-pic=2-methylpyridine): synthesis, structural characterization, nonlinear response and large optical limiting properties

摘要

The title compounds [Et4N](2)[MS4Cu4(SCN)(4)(2-pic)(4)] (M = W 1, Mo 2) have been synthesized by the reaction of (Et4N)(2)MS4, Cu(SCN) and 2-picoline (2-pic, 2-methylpyridine). Single crystal X-ray diffraction data show that the anion clusters [MS4Cu4(SCN)(4)(2-pic)(4)](2-) have the planar 'open' structure with four Cu atoms in three kinds of coordination modes. Nonlinear optical properties of these two clusters are investigated with a 8 ns pulsed laser at 532 nm. The two clusters exhibit large optical limiting performance, with limiting threshold values of 0.3 J cm(-2) for 1, 0.5 J cm(-2) for 2, and self-defocusing effects, effective nonlinear refractive index n(2) = -6.84 x 10(-12) esu (esu = 7.162 x 10(13) m(5) v(-2)) 1 and n(2) = -8.48 x 10(-12) esu 2 respectively. Both compounds show reverse saturable absorption: alpha(2) = 3.1 x 10(-6) m W-1 for 1 and alpha(2) = 3.2 x 10(-6) m W-1 for 2 in 6.98 x 10(-4) mol dm(-3) and 7.44 x 10(-4) mol dm(-3) DMF solution respectively. The corresponding effective NLO susceptibilities chi((3)) are 6.5 x 10(-8) esu 1 and 8.9 x 10(-8) esu 2 while the corresponding hyperpolarizabilities (gamma((1)) = 9.42 x 10(-32) esu and gamma((2)) = 1.29 x 10(-31) esu) are also reported. [References: 46]