Conformational aspects of polymorphs and phases of 2-propyl-1H-benzimidazole

IUCrJ

Aretxabaleta, X.M.¹  Zuiga, F.J.²  Quesada-Moreno, M.M.³  de la Pinta, N.⁴  Breczewski, T.⁵  Avils-Moreno, J.R.⁶  Cruz-Cabeza, A.J.⁷ 

[1] Departamento Fsica Aplicada II, Facultad de Ciencia y Tecnologa, Universidad del Pas Vasco, Apartado 644, Bilbao E-48080, Spain;Departamento Fsica Materia Condensada, Facultad de Ciencia y Tecnologa, Universidad del Pas Vasco, Apartado 644, Bilbao E-48080, Spain;Departamento Qumica Orgnica y Bio-Orgnica, Facultad de Ciencias, Universidad Nacional de Educacin a Distancia (UNED), Senda del Rey 9, Madrid E-28040, Spain;Departamento de Qumica Fsica y Analtica, Universidad de Jan, Campus Las Lagunillas, Jan E-23071, Spain;Departamento de Sistemas Fsicos, Qumicos y Naturales, Universidad Pablo de Olavide, Sevilla E-41704, Spain;Instituto de Qumica Mdica, Centro de Qumica Orgnica Manuel Lora-Tamayo, CSIC, Juan de la Cierva 3, Madrid E-28006, Spain;School of Chemical Engineering and Analytical Sciences, The University of Manchester, The Mill, Sackville Street, Manchester M13 9PL, UK

关键词: MOLECULAR CRYSTALS;    POLYMORPHISM;    PHASE TRANSITIONS;    CONFORMATIONAL CHANGES;    ENERGY MINIMIZATION;   

DOI  :  10.1107/S2052252518011685

学科分类：数学（综合）

来源: International Union of Crystallography

【 摘 要 】

This paper reports on the polymorphism of 2-propyl-1H-benzimidazole (2PrBzIm) induced by temperature change. Upon heating, an irreversible reconstructive-type phase transition at T = 384 K from the ordered form I (P212121) to a new polymorph, form IIHT (Pcam), was observed. The structural transformation between forms I and II involves significant changes in the crystal packing, as well as a key conformational variation around the propyl chain of the molecule. After the first irreversible phase transition, the IIHT form undergoes two further (reversible) phase transitions upon cooling at 361 K (IIRT) and 181 K (IILT). All three phases (forms IIHT, IIRT and IILT) have almost identical crystal packing and, given the reversibility of the conversions as a function of temperature, they are referred to as form II temperature phases. They differ, however, with respect to conformational variations around the propyl chain of 2PrBzIm. Energy calculations of the gas-phase conformational energy landscape of this compound about its flexible bonds allowed us to classify the observed conformational variations of all forms into changes and adjustments of conformers. This reveals that forms I and II are related by conformational change, and that two of the form II phases (HT and RT) are related by conformational adjustment, whilst the other two (RT and LT) are related by conformational change. We introduce the term `conformational phases' for different crystal phases with almost identical packing but showing changes in conformation.

【 授权许可】

CC BY