The Research Of Functional Materials Based On Pyridinium Carboxylic Acid Ligands

Metal-organic frameworks(MOFs)are crystalline materials built from different function blocks.The different function blocks provide a unique opportunity to construct multifunctional MOF material.These are increasingly relying on sophisticated ligands that contain functional characteristics.Pyridinium carboxylic acid ligands as a functional ligand attracted wide interest in the past decades,because of its excellent performance such as redox-active,photochromism,free radicals and so on.In our work,six types of functional metal-organic materials have been constructed from pyridinium carboxylic acid ligands with metal salts.These functional metal-organic materials have been characteried with the aid of IR,UV,elemental analysis,EPR,TGA,X-ray single-crystal diffraction,luminescent spectroscopy,and magnetic susceptibility.The feature and innovation of our present work are described as follows:(1)The azide anion as an energy acceptor and an electron donor have been introduced into a metal-viologen compound to form a 2D layered viologen-based trifunctional material 1,which exhibits the rare discolored function of reversible photochromism and thermochromism.Interestingly,its fluorescence can be switched by visible light irradiation and heating in air.The multiple stimuli of color changes and stability of the coloured species of 1 can broaden their applications in some composite systems that require color switching performances of multiple stimuli.(2)Three Lanthanide-viologen multi-functional materials(2-Eu,2-Dy,2-Tb)were obtained from the disubstituted viologen ligands(L2)and Ln3+ metals.They are all exhibits reversible thermochromic phenomenon.The 2-Eu can exchanged with a variety of anions.The 2-Eu can identify SCN-,N3-,I-anions by naked eye and the detection limit of SCN-,N3-,I-anions can be reduced by combining fluorescence spectrometry.Besides that,the 2-Eu can capture 9 kinds of metal cations by dissolution-recrystallization in different metal salt solution.It is interesting that the compound 2-EuM which captured cationic have the similar cell parameters with 2-Eu.But the 2-EuM frameworks show twenty-sevenfold interpenetration of three-dimensional structures.The 2-EuCd-3 which captured Cd2+ ion exhibits the similar reversible thermochromic and fluorescence emission with 2-Eu.The variable temperature fluorescence data reveal that the 5D0?7F2 transion intensities of 2-EuCd-3 was reduced in accordance with the increase of the temperature.It means that the compound 2-EuCd-3 is suitable for luminescent solid thermometers.(3)Three thermally-induced magnetic materials(3-Cl,3-Br,3-NO3)were obtained from the disubstituted viologen ligands(L2)and different copper salts.The 3-Cl and 3-Br compunds exhibit reversible thermochromic phenomenon at different temperature.Temperature dependence of the magnetic susceptibility study of the compounds 3-C1,3-Br and 3-NO3 reveal that only 3-Cl and 3-Br ?MT value decrease and then increase at their thermochromic temperature.This phenomenons have not yet been reported.It opens a new opportunity for developing thermally-induced magnetism-controllable functional materials.(4)Two luminescent microporous materials 4 and 5 were constructed by using zwiterrionic carboxylic acid ligands.Compound 5 is a heterometal-organic one-dimensional chain-like compound.It exhibits fluorescence emission of Eu3+ ion and weak LMCT emission of Cd2+ ion.The energy transfer of ligand to metal ions can be switched by excitation light.Compound 4 and 5 both have good gas adsorption ability.Surprisingly,4 and 5 shows a remarkably adsorption of CO2 while they did not show any appreciable adsorption of N2 and H2 at 295K.It means that compound 4 and 5 could be useful for selectively capturing CO2.(5)Six 3D lanthanide-organic luminescent materials 6-Ln(Ln=Ce?Sm?Eu?Gd?Tb?Dy)are prepared by self-assembly of zwiterrionic carboxylic acid ligands,sulfur carboxylic acid ligands and lanthanide metal.Ethylene glycol can signicantly improve luminescent intensity of 6-Eu with remarkable enhancement effects.The powder samples of 6-Eu was dispersed into an aqueous solution containing different colorless metal ions,only Ag+ cations can signicantly quenched the emissions of 6-EU and this phenomenon is not disturbed by colorless metal ions.These results indicate the potential of 6-Eu for the sensing of Ag+ cations.