From trans-[(η5-C5Me5)2Mo2S2(μ-S)2] to [(η5-C5Me5)2Mo2(μ3-S)4(CuMeCN)2]2+ to [(η5-C5Me5)2Mo2(μ3-S)4Cu2]-based polymeric and dimeric clusters: syntheses, structures and enhanced third-order non-linear optical performances

Abstract

Reactions of trans-[(η⁵-C₅Me₅)₂Mo₂S₂(μ-S)₂] (1) with 2 equiv. of [Cu(MeCN)₄]X (X = PF₆⁻, ClO₄⁻) produced two acetonitrile-coordinated cubane-like cationic clusters [(η⁵-C₅Me₅)₂Mo₂(μ₃-S)₄Cu₂(MeCN)₂]X₂ (X = PF₆⁻ (2), ClO₄⁻ (3)). Treatment of 2 or 3 with 4,4′-bipyridine (4,4′-bipy) or trans-1,2-bis(4-pyridyl)ethylene) (bpee) afforded two polymeric clusters {[(η⁵-C₅Me₅)₂Mo₂(μ₃-S)₄Cu₂(L)]X₂}_n (4: L = 4,4′-bipy, X = PF₆⁻; 5: L = bpee, X = ClO₄⁻), while analogous reactions of 2 or 3 with 1,2-bis(4-pyridyl)ethane (bpea), 1,2-bis(diphenylphosphine)ethane (dppe), or 1,4-bis-(diphenylphosphine)butane) (dppb) formed three dimeric clusters [(η⁵-C₅Me₅)₂Mo₂(μ₃-S)₄Cu₂(L)]₂X₄ (6: L = bpea; X = PF₆⁻; 7: L = dppe, X = ClO₄⁻; 8: L = dppb, X = ClO₄⁻). Clusters 2–8 consist of a cubane-like [(η⁵-C₅Me₅)₂Mo₂(μ₃-S)₄Cu₂] core with each Cu being coordinated by one labile MeCN molecule (2, 3) or by bridging dipyridyl or diphosphino ligands (4–8). 4 or 5 has a 1D zigzag chain structure while 6–8 contain cyclic dimeric structures. The third-order non-linear optical (NLO) properties of 2–8 in MeCN were investigated by Z-scan technique at 532 nm. These compounds showed strong third-order NLO absorption effects and self-defocusing properties, and their NLO performances were remarkably enhanced relative to those of 1.