Low temperature polymorphism in 3-amino-1-propanol C. Cacela a,b , A. Baudot c , M.L. Duarte a , A.M. Matos-Beja d , M. Ramos Silva d , J.A. Paixa ˜o d , R. Fausto b, * a Departamento de Quı ´mica e Bioquı ´mica, CECUL, Faculdade de Cie ˆncias, Universidade de Lisboa, Portugal b Centro de Quı ´mica de Coimbra, Departamento de Quı ´mica, Universidade de Coimbra, Coimbra 3004-535, Portugal c Centre de Recherches sur les Tre ´s Basses Tempe ´ratures (CNRS),Grenoble, France d Centro de Estudos de Materiais por Difracc ¸a ˜o de Raios-X, Departamento de Fı ´sica, Universidade de Coimbra, Portugal Received 14 November 2002; revised 6 January 2003; accepted 6 January 2003 Abstract 3-Amino-1-propanol (3AP) was investigated by differential scanning calorimetry, and low temperature powder X-ray diffraction and Raman spectroscopy. Within the range of temperatures studied (2 150–25 8C), 3AP was found to be able to crystallize in two monotropic polymorphs. Fast cooling rates produce an amorphous state that, on heating, crystallizes into the metastable polymorph. At higher temperatures, this metastable crystalline phase converts into the stable crystal. Using intermediate cooling rates, 3AP crystallizes as the metastable polymorph, the solid l solid transition leading to conversion of this form into the stable polymorph occurring during the subsequent heating. Slower cooling rates enable formation of the stable crystal on cooling. The two crystalline polymorphs were structurally characterized by powder X-ray diffraction and Raman spectroscopy. It was concluded that different conformations are assumed by the individual molecules of 3AP in the two crystalline varieties, with the molecules assuming the all-trans configuration in the metastable crystalline state and having the heavy atom backbone trans but the NH 2 and OH groups gauche in the stable crystal. q 2003 Elsevier Science B.V. All rights reserved. Keywords: 3-Amino-1-propanol; X-ray diffraction and Raman spectroscopy; Differential Scanning Calorimetry 1. Introduction Simple amino-alcohols with short carbon chains can be used as ice crystallization inhibitors, thus having a potential application in cryobiology as cryoprotectant agents for vitrification of biological material [1]. In a series of previous publications [2–5], we report the results of a systematic study on the physicochemistry of four linear amino-alcohols— 2-amino-1-ethanol (2AE), R-2-amino-1-propanol (2AP), R-1-amino-2-propanol (1AP) and 3-amino-1- propanol (3AP)—in both the liquid and gaseous phases as well as isolated in low temperature inert gas matrixes. For the matrix-isolated molecules, as well as in the gaseous phase, the most populated conformational states of all the studied amino-alcohols were found to be folded structures bearing an intramolecular OH· · ·N hydrogen bond. In their more stable confor- mations all the studied molecules assume a gauche 0022-2860/03/$ - see front matter q 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0022-2860(03)00049-8 Journal of Molecular Structure 649 (2003) 143–153 www.elsevier.com/locate/molstruc * Corresponding author. Tel.: þ351-239-827-703; fax: þ 351- 239-852-080. E-mail address: rfausto@ci.uc.pt (R. Fausto).