Three novel Cu6S6 cluster-based coordination compounds: synthesis, framework modulation and the sensing of small molecules and Fe3+ ions

摘要

Three novel Cu6S6 cluster-based coordination compounds formulated as [Cu-3(I)(mpymt)(3)](2) (1), {((Cu4Br4)-Br-I) [Cu-6(I)(mpymt)(6)]}(n) (2), and {((Cu6I6)-I-I)[Cu-6(I)(mpymt)(6)]}(n) (3) (Hmpymt = 4-methylpyrimidine-2-thione), have been synthesized under solvothermal conditions and characterized by elemental analysis, infrared (IR) spectroscopy, thermal gravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. Structural analysis reveals that compound 1 shows a distorted octahedral core of six copper atoms (Cu6S6) constructed from four alpha and two beta type NvC-SH parts from six mpymt-anions. Compound 2 displays an interesting 3D framework constructed from Cu6S6 and Cu4Br4 Cu(I) clusters simultaneously, interestingly, six mpymt-with a type NvC-SH parts are involved in the formation of Cu6S6. Compound 3 displays an infinite 1D framework constructed from Cu6S6 and Cu6I6 Cu(I) clusters, notably, four a and two beta type NvC-SH parts are involved in the formation of the Cu6S6 cluster, however, only mpymt-ligands containing a type NvC-SH parts form the bridged Cu6I6 cluster. The experimental results reveal that halogen ions finely modulate the structural features of compounds 1-3. The fluorescent properties of compounds 1-3 in the solid state and in various solvent emulsions were investigated in detail, the results of which indicate that compounds 1-3 are all highly sensitive naked eye colorimetric sensors for NB, 2-NT and Fe3+ (NB = nitrobenzene and 2-NT = 2-nitrotoluene).