New Zn(II)/M(I) (M = Na, K and Rb) metal-organic frameworks based on 5-methylisophthalic acid ligand: Syntheses, structures and fluorescent property

Reactions of Zn(NO₃)₂6H₂O and MNO ₃ (M = Na, K and Rb) with H₂mip (H2mip = 5-methylisophthalic acid) in DMF (DMF = N,N'-dimethylformamide) resulted in the formation of novel heterometallic metal-organic frameworks (Me ₂NH₂)[ZnM(mip)2] (1: M = Na; 2: M = K; 3: M = Rb, mip = 5-methylisophthalate dianion for 1∼3). These complexes belong to the monoclinic system, space group P2/c and have been fully characterized by satisfactory elemental analysis, FT-IR spectra, TGA and single-crystal X-ray diffraction. Single-crystal X-ray diffraction studies reveal that 1∼3 are 3D isomorphic structures based on a trinuclear unit {ZnM2( μ₂-COO) ₂ ( μ₃-COO)₂} and exhibit pcu topological net and blue fluorescence.