A novel pyridine containing self-assembling system: synthesis, characterization, X-ray crystal structure, 13C solid phase NMR and solution studies

Abstract

The synthesis of a novel pyridine containing self-assembling system, L, is reported. This system is prepared from the reaction between 2,6-pyridinedicarboxylic acid, [pydc.H2], and 2,6-pyridinediamine, [pyda], in the presence of Et3N in THF as solvent in 88% yield. Double proton transfer from diacid to diamine results in the formation of a self-assembling system consisting of dicationic and dianionic units connecting through H-bonding and ion-pairing simultaneously as shown in the X-ray crystal structure. L is recrystallized from H2O. The crystal system is monoclinic with space group P21/c. One of the carboxylate anions of dianion unit is connected to and directed toward two ammonium cations of dication unit while the other one interacts with neighboring pyridine CH. The characterization was performed using EI, CI, ES mass spectroscopy as well as 1H and 13C solution NMR and X-ray crystal. The solid phase NMR, as a tool for conformation and structure prediction, reveals that the two –CO2− functional groups are not equally involved in the self-assembling system. The 13C solid phase NMR data is in agreement with X-ray crystal structure.