Robust Lanthanoid Picolinate-Based Coordination Polymers for Luminescence and Sensing Applications.

Picolinate-based segmented dianionic ligands L12- (5-((4-carboxyphenyl)ethynyl)picolinate) and L22- (5,5'-(ethyne-1,2-diyl)dipicolinate) have been used in the synthesis of the highly robust and luminescent europium(III) coordination polymers [(CH3)2NH2][Eu(H2O)2(L1)2] (1) and [(CH3)2NH2][Eu(L2)2]·H2O·CH3COOH (2). Both 1 and 2 exhibit high selectivity for detection of nitroaromatic compounds since they act as quenchers of the Eu3+ emission. Stern-Volmer plots, using nitrobenzene as a quencher, yielded values of KSV = 150 M-1 and 160 M-1 for 1 and 2, respectively. Luminescence studies in the presence of different metal ions indicate a high selectivity for Fe3+ detection, with KSV values of 471 M-1 and 706 M-1 for 1 and 2, respectively. Both 1 and 2 possess extremely robust extended structures, leading to emissive properties that are stable in a wide pH range.