A temperature-induced order?disorder phase transition in a novel 4- substituted 4,2:60,400-terpyridine

JUAN GRANIFO; MARLEEN WESTERMEYER; MARICEL RIQUELME; SEBASTIAN SUAREZ; EMILIA HALAC; RICARDO BAGGIO

Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials

John Wiley and Sons Inc.

Lugar: New Jersey; Año: 2015

2052-5206

Crystals of -(isoquinolin-4-yl)-4,20:60,400-terpyridine (iqtp), C24H16N4, grownfrom an ethanol solution, undergo a reversible first-order, single-crystal tosingle-crystal phase transition at Tc in the range 273?275 K, from a disorderedhigher-temperature phase [form (I)] in the space group P21/c, with one singlemolecule in the asymmetric unit, to an ordered lower-temperature one [form(II)] in the space group P21/n, with two independent molecules. There is agroup?subgroup relationship linking (I)?(II), due to cell doubling and thedisappearance of a number of symmetry operations. In addition to X-raydiffraction, the transition has been monitored by Raman spectroscopy anddifferential scanning calorimetry [disclosing an enthalpy change of0.72 (6) kJ mol1 between 170 and 293 K are presented. The evolution of diffraction spots in the vicinity of the transition temperature shows the coexistence of both phases,confirming the first-order character of the transition. Structural details of both phases are analyzed and intermolecular interactions compared in order to investigate the mechanism of the phase transition. A three-dimensional Hirshfeld surface analysis was performed to corroborate the significant changes in the intermolecular features.