Three peroxomorphic H2O2 adducts of antibiotic furacin: the first cases of 2D hydrogen-bonded peroxide layers and concerted flip-flop hydrogen disorder of peroxide species.

Abstract

Crystallization of antimicrobial compound furacin (nitrofurazone) from 96%, 50%, and 20% hydrogen peroxide (HP) led to three novel solvates C6H6N4O4•H2O2, C6H6N4O4•1.5(H2O2), and C6H6N4O4•3.5(H2O2), respectively. Surprisingly, more rich in hydrogen peroxide solvatomorphs were obtained from more diluted H2O2 solutions. The stability of compounds decreased with increase of peroxide content. These compounds represent the rare example of solvatomorphism (peroxomorphism) among crystalline hydrogen peroxide adducts. The structures of all adducts were determined by X-ray crystallography. All of them contain 1:1 chelating supramolecular synthon with strong unusual bifurcate donor hydrogen bond HOOH…(O2N, furane). Compound C6H6N4O4•3.5(H2O2) is the first example of the structure containing 2D hydrogen-bonded layers built exclusively from peroxide molecules. In its crystal, concerted flip-flop proton disorder of HP molecules was observed for the first time.