Tungsten(VI)-Copper(I)-Sulfur Cluster-Supported Metal-Organic Frameworks Bridged by in Situ Click-Formed Tetrazolate Ligands

Six analogous two-dimensional (2D) [Tp*WS3Cu3]-based (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) networks, namely, {[(Tp*WS3Cu3)(2)L-3](mu(3)-N-3)}(n) (2: L = 5-methyltetrazolate (Mtta); 3a: L = 5-ethyltetrazolate (Etta)) and {[(Tp*WS3Cu3)(2)L-3]BF4}(n) (3b: L = Etta; 4: L = 5-propyltetrazolate (Ptta); 5: L = 5-butyltetrazolate (Btta); 6: L = 5-pentyltetrazolate (Petta)) were synthesized by reactions of [Et4N][Tp*WS3] (1), [Cu(CH3CN)(4)]BF4, NaN3, and NH4BF4 in different nitrile solvents (CH3(CH2)(n)CN, n = 0, 1, 2, 3, and 4) under solvothermal conditions. In the structures of 2-6, each alkyl tetrazolate L as a bridging ligand was generated in situ from the click reaction between azide and nitrile. These 2D (6,3) networks support two types of voids wherein the pendant alkyl groups are accommodated. A tetrahedron cage-like cluster [Tp*W(mu(3)-S)(3)(mu(3)-S')Cu-3](4) (7) was also formed in some of the above reactions and can be readily separated by solvent extraction. The proportion of 7 increased with the elongation of the alkyl chains and finally became the exclusive product when heptylnitrile was employed. Further use of CuCN as a surrogate for [Cu(CH3CN)(4)]BF4 with the aim of introducing additional CN bridges into the network led us to isolate a tetrazolate-free compound, {[Et4N]{(Tp*WS3Cu3)[Cu-2(CN)(4.5)]}(2)2PhCH(2)CN}n (82PhCH(2)CN), a unique 2D network that features {(Tp*WS3Cu3)[Cu-2(CN)(5)]}(2)(2), {(Tp*WS3Cu3)(3)[Cu-3(CN)(7)](2)[Cu(CN)(3)]}(4), and {(Tp*WS3Cu3)[Cu-4(CN)(9)]}(2)(6) ring subunits. Compounds 58 are soluble in DMF and exhibit a reverse saturable absorption and self-focusing third-order nonlinear optical (NLO) effect at 532 nm with hyperpolarizability ? values in the range of 4.43 x 10(30) to 5.40 x 10(30) esu, which are 400500 times larger than that of their precursor 1. The results provide an interesting insight into the synergetic synthetic strategy related to the assembly of the [Tp*WS3Cu3](2+) cluster core, the click formation of the tetrazolate ligands, and the construction of the [Tp*WS3Cu3](2+) cluster-based 2D networks.