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

Qiu Fang Chen, Xin Zhao, Quan Liu, Ji Dong Jia, Xiao Ting Qiu, Ying Lin Song, David James Young, Wen Hua Zhang, Jian Ping Lang

Research output: Contribution to journalArticle

Abstract

Six analogous two-dimensional (2D) [Tp∗WS3Cu3]-based (Tp∗ = hydridotris(3,5-dimethylpyrazol-1-yl)borate) networks, namely, {[(Tp∗WS3Cu3)2L3](μ3-N3)}n (2: L = 5-methyltetrazolate (Mtta); 3a: L = 5-ethyltetrazolate (Etta)) and {[(Tp∗WS3Cu3)2L3]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)nCN, 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(μ3-S)33-S′)Cu3]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)[Cu2(CN)4.5]}2·2PhCH2CN}n (8·2PhCH2CN), a unique 2D network that features {(Tp∗WS3Cu3)[Cu2(CN)5]}2 2-, {(Tp∗WS3Cu3)3[Cu3(CN)7]2[Cu(CN)3]}4-, and {(Tp∗WS3Cu3)[Cu4(CN)9]}2 6- ring subunits. Compounds 5-8 are soluble in DMF and exhibit a reverse saturable absorption and self-focusing third-order nonlinear optical (NLO) effect at 532 nm with hyperpolarizability γ values in the range of 4.43 × 10-30 to 5.40 × 10-30 esu, which are 400-500 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.

Original languageEnglish
Pages (from-to)5669-5679
Number of pages11
JournalInorganic Chemistry
Volume56
Issue number10
DOIs
Publication statusPublished - 15 May 2017
Externally publishedYes

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