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

Two N , N ′-bis(3-pyridylmethyl)pyromellitic diimide (3-pmpmd) coordination polymers, namely{[Hg(3-pmpmd)I 2 ]·H 2 O)} n ( 1 ), {[Ni 2 (3-pmpmd) 3 (NO 3 ) 4 ]·2CH 3 OH} n ( 2 ), have been synthesized by reactions of 3-pmpmd with HgI 2 , Ni(NO 3 ) 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. Graphic abstract 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.