Assembly of new Mo/Cu/S clusters from [Et4N][Tp*MoS(S4)] and Cu(i) salts: syntheses, structures and third-order nonlinear optical properties

Reactions of [Et4N][Tp*MoS(S)4] (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) (1) with 3 equiv. of CuX (X = Cl, Br, I, CN) or [Cu(MeCN)4]ClO4 in CH2Cl2-MeCN or CH2Cl2-DMF afforded [Et4N]2[Tp*Mo(μ3-S)3(CuCl)3(μ3-Cl)] (2), [Et4N][Tp*Mo(μ3-S)3(CuX)3] (3: X = Br; 4: X = I), [Et4N][Tp*MoO(μ-S)2(CuX)] (5: X = I; 6: X = CN) and [Tp*Mo(μ3-S)3Cu3(μ3-S')]4 (7). Compounds 2-7 were characterized by elemental analysis, IR spectra, UV-vis spectra, (1)H NMR, electrospray ion mass spectra (ESI-MS) and X-ray crystallography. The cluster dianion of 2 has a complete cubane-like [Tp*Mo(μ3-S)3(CuCl)3(μ3-Cl)] structure while the anion of 3 or 4 consists of an incomplete cubane-like [Tp*Mo(μ3-S)3(CuX)3] structure. The anion of 5 or 6 has a binuclear structure, in which one [Tp*MoO(μ-S)2] moiety and one CuX unit are linked by a pair of μ-S atoms. The structure of 7 may be considered as a supercube whose eight corners are occupied by four incomplete cubane-like [Tp*Mo(μ3-S)3Cu3] fragments and four μ3-S' atoms. The third-order nonlinear optical (NLO) properties of 2-6 in DMF were investigated by femtosecond degenerate four-wave mixing (DFWM) technique with a 80 fs pulse width at 800 nm. Compounds 2-6 exhibited good NLO performances and their NLO responses were enhanced relative to that of 1.