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Hexamethylenetetramine-tridecanedioic acid (1/1): temperature-induced order-disorder structural phase transitions
Maximiliano Jesús Moreno Zapata1, Willian Xerxes Coelho Oliveira2, Carlos Basílio Pinheiro1
1Departamento de Física - Laboratório de Cristalografia, Universidade Federal de Minas Gerais, Av. Antônio Carlos, 6627 Belo Horizonte, Minas Gerais/Brazil, 31270-901, Brazil.
Abstract:
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.
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