Granifo Juan, Westermeyer Marleen, Riquelme Maricel, Gaviño Rubén, Suárez Sebastián, Halac Emilia B, Baggio Ricardo
Departamento de Ciencias Químicas y Recursos Naturales, Facultad de Ingeniería y Ciencias, Universidad de La Frontera, Casilla 54-D, Temuco, Chile.
Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, Circuito Exterior Coyoacán, 04510 México, Mexico.
Acta Crystallogr B Struct Sci Cryst Eng Mater. 2015 Dec 1;71(Pt 6):805-13. doi: 10.1107/S205252061501937X.
Crystals of 4'-(isoquinolin-4-yl)-4,2':6',4''-terpyridine (iqtp), C24H16N4, grown from an ethanol solution, undergo a reversible first-order single-crystal to single-crystal phase transition at Tc in the range 273-275 K, from a disordered higher-temperature phase [form (I)] in the space group P21/c, with one single molecule in the asymmetric unit, to an ordered lower-temperature one [form (II)] in the space group P21/n, with two independent molecules in the asymmetric unit. There is a group-subgroup relationship linking (I)-(II), due to cell doubling and the disappearance of a number of symmetry operations. In addition to X-ray diffraction, the transition has been monitored by Raman spectroscopy and differential scanning calorimetry, the latter disclosing an enthalpy change of 0.72 (6) kJ mol(-1). Variations of the unit-cell parameters with temperature 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.
从乙醇溶液中生长出的4'-(异喹啉-4-基)-4,2':6',4''-三联吡啶（iqtp）晶体，化学式为C24H16N4，在273 - 275K范围内的Tc温度下经历了可逆的一级单晶到单晶相变，从空间群为P21/c的无序高温相[晶型（I）]转变为空间群为P21/n的有序低温相[晶型（II）]，前者不对称单元中有一个单分子，后者不对称单元中有两个独立分子。由于晶胞加倍和一些对称操作的消失，存在一种连接（I） - （II）的群 - 子群关系。除了X射线衍射外，还通过拉曼光谱和差示扫描量热法监测了该转变，差示扫描量热法显示焓变为0.72（6）kJ mol(-1)。给出了170至293K之间晶胞参数随温度的变化。转变温度附近衍射斑点的演变表明两个相共存，证实了转变的一级特征。分析了两个相的结构细节并比较了分子间相互作用，以研究相变机制。进行了三维 Hirshfeld 表面分析以证实分子间特征的显著变化。
