Two interesting heterobimetallic compounds [MOS 3Cu 3(4-pic) 6]·Br (M=Mo, W) with cationic cluster: synthesis, structural characterization, non-linear response and large optical limiting properties

Abstract

Two heterobimetallic cluster compounds [MOS 3Cu 3(4-pic) 6]·Br (M=Mo, W) with cationic cluster skeleton and halide anion Br − synthesized by the reaction of (NH 4) 2MOS 3, CuBr and 4-picoline (4-pic) are presented. Their structures have been crystallographically determined and such nest-shaped cationic clusters, obtained for the first time, are interesting in comparison with the analogical nest-shaped clusters with a neutral skeleton or anionic skeleton. The non-linear optical (NLO) properties of these two clusters are investigated with an 8 ns pulsed laser at 532 nm. These two clusters exhibit large optical limiting abilities with limiting thresholds F th=0.18 J cm −2 ( 1) and F th=0.15 J cm −2 ( 2), respectively. Both compounds show strong third-order NLO absorption effects ( α 2-value of 1.6×10 −10 m W −1 ( 1), 2.8×10 −10 m W −1 ( 2)) and self-focusing performance ( n 2-value of 4.56×10 −11 esu ( 1), 4.62×10 −11 esu ( 2)) in 3.86×10 −4 mol dm −3 ( 1) and 8.89×10 −4 mol dm −3 ( 2) DMF solution separately. The corresponding effective NLO susceptibilities χ (3) are 5.4×10 −12 esu ( 1) and 5.5×10 −12 esu ( 2) while the corresponding hyperpolarizabilities ( γ ( 1) =2.51×10 −31 esu and γ ( 2) =1.03×10 −31 esu) are also reported.