Reaction of crown ethers with five-membered heterocycles: 1H-imidazole-4,5-dicarbonitrile, 3-nitro-1,2,4-triazole, and 1H-tetrazole

Abstract

one proton at each of the two proton-donating atoms separated by one covalent bond, it was shown that uncharged crystalline supramolecular compounds can be obtained on account of the proton-donating characteristics of the aromatic heterocycles.An indispensable condition for the formation of crystalline supramolecular compounds [1, 2] of crown ethers with organic molecules is the presence in the latter of proton-donating centers with one of the atoms C, N, or O, particularly H 2 N-, H 2 NSO 2 -, H 2 NCS-, H 2 NHNCO-, H 2 C=, H 3 C-, H 3 CO-, and similar groups or water molecules [1-3], securing stabilization of the components of the supramolecular compound by hydrogen bonds. As a rule a pair of protons of the substituent takes part in bonding, and the stability of the compounds decreases in the following order: OH > NH 2 > CH 2 [4]. The crystalline supramolecular compounds of crown ethers with heterocycles are stabilized by hydrogen bonds either through one of the above-mentioned substituents in the heterocycle [5][6][7][8][9][10][11][12] or the cyclic ammonium group of the protonated heterocycle [13]. A single example of the formation of a crystalline supramolecular compound of the most effective [3,14] crown ether 1b with unsubstituted triazole is known [15].The aim of this work was to determine the possibility of synthesizing uncharged crystalline supramolecular compounds of various crown ethers with five-membered aromatic heterocycles, containing one proton at each of two adjacent proton-donating atoms separated by one covalent bond and securing stabilization of the supramolecular compound by analogy with the data in [15].It was established that the crystalline supramolecular compounds [1b·4]-7, [2·4]-8, [3·2(4)]-9, [1a·5]-10, [1b·2(5)]-11, [2·2(5)]-12, [3·2(5)]-13, and [3·2(6)]-14 respectively are formed during spontaneous evaporation of the solvents from solutions of the crown ethers 1-3 with the respective heterocycles 4-6.