Temperature-Dependent Structure–Energy Changes in Crystals of Compounds with Poly(hydroxymethyl) Grouping

Crystals of tris(hydroxymethyl)nitromethane (1) and tris(hydroxymethyl)aminomethane (2) were prepared and grown at room temperature. X-ray analysis was used to study the structure of crystals 1 and 2 at room temperature; the X-ray diffraction method was applied to investigate polycrystalline samples during a temperature rise up to the phase transition into the plastic phase. Phase transitions in separate crystals 1 and 2 were observed in a hot stage under an optical microscope. Calorimetric study of the crystal temperature behavior and the phase transition features including melting were carried out. By IR spectroscopy the temperature relations of the bonds of symmetric N–O stretching vibrations of nitro groups and stretching vibrations of OH groups redistribution in crystals of 1 were investigated. In crystals of 2 the behavior of stretching vibration bands of O–H groups was studied at room temperature. In the temperature interval including phase transition, data on structure–dynamic rearrangements in the crystal lattice of compounds 1 and 2 were obtained by the NMR pulse method in the solid phase using relaxational free induction decay of protons. The proton conductivity was found and its temperature parameters were determined for both compounds in the plastic state.