Two interesting heterobimetallic compounds [MOS3Cu3(4-pic)(6)]center dot Br (M = Mo, W) with cationic cluster: synthesis, structural characterization, non-linear response and large optical limiting properties

Two heterobimetallic cluster compounds [MOS3Cu3(4-pic)(6)]. Br (M = Mo, W) with cationic cluster skeleton and halide anion Br- synthesized by the reac tion of (NH4)(2)MOS3, CuBr and 4-picoline (4-pic) are presented. Their stru ctures have been crystallographically determined and such nest-shaped catio nic clusters, obtained for the first time, are interesting in comparison wi th the analogical nest-shaped clusters with a neutral skeleton or anionic s keleton. The non-linear optical (NLO) properties of these two clusters are investigated with an 8 ns pulsed laser at 532 nm. These two clusters exhibi t large optical limiting abilities with limiting thresholds F-th = 0.18 J c m(-2) (1) and F-th =0.15 J cm(-2) (2), respectively. Both compounds show st rong third-order NLO absorption effects (alpha (2)-value of 1.6 x 10(-10) m W-1 (1), 2.8 x 10(-10) m W-1 (2)) and self-focusing performance (n(2)-valu e of 4.56 x 10(-11) esu (1), 4.62 x 10(-11) esu (2)) in 3.86 x 10(-4) mol d m(-3) (1) and 8.89 x 10-4 mol dm(-3) (2) DMF solution separately. The corre sponding effective NLO susceptibilities chi ((3)) are 5.4 x 10(-12) esu (1) and 5.5 x 10(-12) esu (2) while the corresponding hyperpolarizabilities (g amma ((1)) = 2.51 x 10(-31) esu and gamma ((2)) = 1.03 x 10-31 esu) are als o reported. (C) 2000 Published by Elsevier Science B.V. All rights reserved .