2-Aminobenzimidazole peroxosolvate – the third H2O2 crystalline adduct stabilized with the maximum possible number of hydrogen bonds formed by one hydrogen peroxide molecule.

The crystal structures of cyclic dipeptide peroxosolvates provide valuable insight into the non-redox interaction of hydrogen peroxide with the peptide backbone.

Peroxosolvates of 2-aminonicotinic acid (I) and lidocaine N-oxide (II) including the largest insular hydrogen peroxide clusters were isolated and their crystal structures were determined by single-crystal X-ray diffraction. An unprecedented dodecameric hydrogen peroxide insular cluster was found in I. An unusual cross-like pentameric cluster was observed in the structure of II. The topology of the (H O ) assembly was never observed for small-molecule clusters. In I and II new double and triple cross-orientational disorders of H O were found. Cluster II is the first example of a peroxosolvate crystal structure containing H O molecules with a homoleptic hydrogen peroxide environment. In II, a hydrogen bond between an H O molecule and a peptide group -CONH⋅⋅⋅O H was observed for the first time.

Novel peroxosolvates of the non-proteinogenic amino acids sarcosine C3H7NO2·H2O2 (1) and phenylserine C9H11NO3·H2O2 (2) were prepared and their structures were determined by X-ray crystallography.

Energy/enthalpy of intermolecular hydrogen bonds (H-bonds) in crystals have been calculated in many papers. Most of the theoretical works used non-periodic models. Their applicability for describing intermolecular H-bonds in solids is not obvious since the crystal environment can strongly change H-bond geometry and energy in comparison with non-periodic models. Periodic DFT computations provide a reasonable description of a number of relevant properties of molecular crystals. However, these methods are quite cumbersome and time-consuming compared to non-periodic calculations. Here, we present a fast quantum approach for estimating the energy/enthalpy of intermolecular H-bonds in crystals. It has been tested on a family of crystalline peroxosolvates in which the H∙∙∙O bond set fills evenly (i.e., without significant gaps) the range of H∙∙∙O distances from ~1.5 to ~2.1 Å typical for strong, moderate, and weak H-bonds. Four of these two-component crystals (peroxosolvates of macrocyclic ethers and creatine) were obtained and structurally characterized for the first time. A critical comparison of the approaches for estimating the energy of intermolecular H-bonds in organic crystals is carried out, and various sources of errors are clarified.

The title compound, C6H11NO2·2H2O2, is the richest (by molar ratio) in hydrogen peroxide among the peroxosolvates of aliphatic α-amino acids. The asymmetric unit contains a zwitterionic pipecolinic acid molecule and two hydrogen peroxide molecules. The two crystallographically independent hydrogen peroxide molecules form a different number of hydrogen bonds: one forms two as donor and two as acceptor ([2,2] mode) and the other forms two as donor and one as acceptor ([2,1] mode). The latter hydrogen peroxide molecule forms infinite hydrogen-bonded hydroperoxo chains running along the c-axis direction, which is unusual for aliphatic α-amino acid peroxosolvates.

Base-mediated cyclization of (5-iodo-1,2,3-triazolyl)phenols was proposed as a new synthetic strategy for the in situ generation of diazoimines via electrocyclic ring opening of the fused heterocycle. Cu-catalyzed amination of the intermediate diazoalkanes was employed to develop an efficient cascade approach to functionalized benzoxazoles.

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