Synthesis, Structure and Fluorescence Sensing Property of Manganese Metal-Organic Framework Based on 5-Aminonicotinic Acid.

A new three-dimension manganese(II) metal-organic framework [Mn2(5-ana)4 (H2O)]n (namely Mn-MOF) has been successfully constructed by the reaction of 5-aminonicotinic acid (5-Hana) and MnCl2 using solution method at room temperature. The structure and properties of Mn-MOF were characterized by X-ray single-crystal diffraction, X-ray powder diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis, ultraviolet-visible spectra and luminescent spectra. Structural analysis reveal that the as-synthesized complex crystallized in the monoclinic system and feature a binodal (2,8)-connected coordination network. The [Mn2(CO2)2 (H2O)] dimeric unit acts as 8-connected node and 5-ana-ligand acts as 2-connected node. Electrostatic potential (ESP) on molecular van der Waals surface analysis of 5-ana- ligand shows that the first reactive site exists in the surface close to the oxygen atoms of carboxyl group with the ESP global minimum of -143.37 kcal·mol-1. The second and third reactive sites exist in the nitrogen atoms of pyridine ring and amino, respectively. Mn-MOF displays good thermal stability at room temperature. Fluorescence spectroscopy measurement reveals that the complex shows emission maximum at 402 nm upon 256 nm light excitation. More importantly, Mn-MOF exhibits sensing selectivity for Fe3+ by fluorescence quenching with the quenching efficiency up to 98.71%, which makes it as a potential luminescent sensor for analyzing Fe3+ in aqueous solution. [ABSTRACT FROM AUTHOR]