Synthesis and crystal structure of two coordination polymers based on N,N′-bis(3-pyridylmethyl)pyromellitic diimide and fluorescence thiocyanate sensing

Abstract

Two N,N′-bis(3-pyridylmethyl)pyromellitic diimide (3-pmpmd) coordination polymers, namely{[Hg(3-pmpmd)I2]·H2O)}n (1), {[Ni2(3-pmpmd)3 (NO3)4]·2CH3OH}n (2), have been synthesized by reactions of 3-pmpmd with HgI2, Ni(NO3)2, respectively. Both complexes have been characterized by elemental analyses, powder X-ray diffraction, thermogravimetric analyses, IR spectroscopy, and single-crystal X-ray diffraction. In complex 1, the 3-pmpmd ligand adopts Zt-mode conformation, resulting in a typical 1D zigzag chain arranged in a parallel array; in complex 2, the 3-pmpmd ligand adopts Zt-mode and Uc-mode (two conformations), and complex 2 is a 2D (6, 3) network containing 1D quadrangle channels to accommodate the methanol molecules. The structural diversity in both complexes is attributed to the different conformations adopted by the 3-pmpmd ligand. Complex 2 showed remarkably enhanced fluorescence intensity at 340 nm upon the addition of 2 equiv of SCN− anion (NaSCN) with respect to complex 2, which is highly promising for fluorescence sensing of the SCN− anion. The methanol adsorption of complex 2 exhibited a dynamic adsorption property. Two 1D and 2D N,N′-bis(3-pyridylmethyl)pyromellitic diimide (3-pmpmd) coordination polymers have been synthesized; the conformations of 3-pmpmd ligand affects their structural diversity. The enhanced fluorescence intensity sensor for SCN− anion of complex 2 was investigated, which is highly promising for fluorescence sensing SCN− anion.