Synthesis and characterization of polyamides containing imidazole: intramolecular hydrogen bonding and constitutional isomerism

Abstract

Polyamides derived from l-methyl-4,5-imidazoledicarboxylic acid and aliphatic diamines such as hexamethylenediamine, neopentylenediamine, and ethylenediamine are synthesized and characterized.The polymers have inherent viscosities up to 0.56 dL/g, are amorphous, have good thermal stability, and are soluble in a wide range of solvents. The amide proton of the carboxamide at the 5-position of the imidazole intramolecularly hydrogen bonds to the carbonyl oxygen at the 4-position. There is little or no evidence of intermolecular hydrogen bonding occurring in the polyamides. The nonsymmetric diacid creates constitutional isomerism in the polymers. This isomerism can be detected at various levels, by NMR spectroscopy, in the polyamides depending on the diamine portion and the solvent used.

Synthesis of Symmetric Bis(imidazole-4,5-dicarboxamides) Substituted with Amino Acids

“…The conformational behavior of bis-I45DCs having N-methyl imidazole rings has been described, 21 and we expect the bis-I45DCs in this study to be similar. We note that many of the bis-I45DCs show evidence of multiple conformations in both their 1 H and 13 C NMR spectra at room temperature.…”

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

“…Fig. 14 shows a selection of Rasmussen’s 4,5-dicyanoimidazole derivatives, such as vinazene 73 [ 29 , 81 ], push–pull amines and betaines 74 – 78 [ 82 – 87 ], alkoxy derivatives 79 , 80 [ 88 ], biimidazoles 81 [ 89 – 92 ], and triimidazoles 82 [ 93 – 94 ], as well as fullerenes [ 95 ] and polymers [ 96 – 99 ].…”

“…Variously 4,5-dicyanoimidazole-functionalized polymers were mainly investigated by Rasmussen et al [ 29 , 81 , 86 – 88 96 – 99 ]. However, these systems were not intended as nonlinear optical polymers.…”

Intramolecular Hydrogen Bond Strength and pKa Determination of N,N‘-Disubstituted Imidazole-4,5-dicarboxamides

“…Earlier work has shown that the I45DCs form a robust seven-membered intramolecular hydrogen bond in the solid state, along with a relatively small number of different intermolecular aggregation motifs . The solution conformation of I45DCs and other closely related analogues such as ring alkylated I45DCs has been previously reported. − The torsional potential of the substituent amide bond of a ring alkylated I45DC was estimated to be worth 20 kcal/mol, a value that reflects the strength of this intramolecular hydrogen bond . Despite this interest in the intramolecular hydrogen-bonded conformation, no empirical determination of the hydrogen bond strength has ever been reported.…”