Hexamethylenetetramine – tridecanedioic acid (1/1): temperature-induced order – disorder structural phase transitions with phase co-existence

The cocrystal hexamethylenetetramine – tridecanedioic acid (1/1) (HMT – C13), C6H12N4 · C13H24O4, was investigated by single-crystal X-ray diffraction techniques at several temperatures during cooling and heating processes. Our results show the formation of two crystalline phases, separated by a large temperature phase co-existence between 290 and 340   K. Phase I, stable above 341   K, presents an orthorhombic structure described in the space group Bmmb, with one N4(CH2)6 · C13H22O4 adduct in its asymmetric unit. Phase II, stable below 290   K, presents a monoclinic symmetry described by the space group P21/c, with two N4(CH2)6 · C13H22O4 adducts in its asymmetric unit. The phase co-existence is observed both upon cooling and heating, and seems to be related to a complex domain-growth dynamic within the crystal.

Source: Acta Crystallographica Section C - May 9, 2022 Category: Chemistry Authors: Zapata, M.J.M. Oliveira, W.X.C. Pinheiro, C.B. Tags: cocrystal order – disorder phase transition crystal structure phase co-existence hexamethylenetetramine tridecanedioic acid research papers Source Type: research