Evaluation of two novel macrocycles containing pyridine-2,6-dicarboxamide unit as cationic fluorescent sensor

Two new amidic macrocycles, L1 and L2 were synthesized by the condensation reaction of 4-chloro- and pyridine-2,6-dicarbonylchloride with 1,2-bis(2-aminoethoxy)ethane and 1-(2-aminoethyl)piperazine, respectively. The compounds have been fully identified by single-crystal X-ray diffraction. These substances were found to exhibit fluorescence property and remarkable solvatofluorochromism in various organic solvents (Delta(lambda EM) = 139 and 141 nm for L1 and L2, respectively). Also, the compounds were tested as fluorescent sensor toward a number of metals and noticeable fluorescence was indicated for them in the presence of Pb2+. Subsequent experiments evaluated the ability of the compounds to detect Pb2+ in PC12 (adrenal pheochromocytoma) cells. The cytotoxicity of the compounds was measured via MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) method. Cell uptake and biosensing capability were evaluated by treating PC12 cells with mentioned compounds and after that with lead(II) nitrate. Obtained results of MTT experiment and fluorescent images revealed that both compounds at about 0.01 mu M possess zero cytotoxicity and have acceptable capability for detecting Pb2+ in tested cells. (C) 2019 Elsevier Ltd. All rights reserved.