One-dimensional uranium(VI) coordination polymers with pyridinecarboxylate ligands

A method to produce picolinate ligand in situ under hydrothermal conditions has been used to synthesize four uranyl hydroxyl, oxo- and oxohydroxyl picolinato complexes. (UO2)(OH)(Pic) (1) (HPic = picolinic acid) contains 7-fold coordinated uranyl hydroxyl dimers linked through 2-bridging Pic ligands forming a one-dimensional (1D) polymer. (NH4)[(UO2)(3)(O)(2)(OH)(Pic)(2)] (2) consists of 7-fold coordinated uranyl oxohydroxyl trinuclear units linked through both mu(2)- and mu(3)-Pic ligands forming a 1D polymer. (NH4)(UO2)(2)(O)(2)(Pic)] (3) is constructed with 7-fold coordinated uranyl oxo-dinuclear units linked through oxo- and mu(3)-Pic ligands forming a 1D polymer. (NH4)[(UO2)(4)(O)(2)(OH)(2)(Pic)(2)(INT)]center dot H2O (4) (HINT = isonicotinic acid) is made of 7-fold coordinated uranyl oxohydroxyl tetranuclear units linked through both Pic and INT ligands forming a 1D polymer. All four polymers are thermal robust to 350 degrees C. Raman spectroscopy confirmed the presence of uranyl ion and Pic ligand. In addition, red enhanced fluorescence emissions have been observed for both 1 and 4. The synthesis method, with the advantage of controlling uranyl hydrolysis and generating ligand in situ, provides a more reliable way to make new coordination polymers of carboxylate ligands with various uranyl hydrolysis species. Crown Copyright (C) 2016 Published by Elsevier Ltd. All rights reserved.