Syntheses,Crystal Structures and Thermal Behaviour of Novel L-Alanine Halogenide Compounds

摘要

Two new L-alanine compounds(alanine alaninium triiodide(1),s.g.P2_12_12_1,a=8.366(2)A,b=8.912(2)A,c=41.889(8)A and alanine SrCl2 3H2O(2),s.g.P2_1,a=8.540(2)A,b=7.167(1)A,c=8.769(2)A,beta=95.02(3)°)have been prepared and characterised by X-ray single crystal analysis.The crystal structure of(1)features the presence of two independent molecules of alanine,alaninium and triiodide,respectively,in the asymmetric unit,with a very strong hydrogen bond between the carboxylate groups of alanine and alaninium.Compound(2)is composed of infinite zig-zag chains of[SrO7Cl]-polyhedra,with alanine molecules and chloride ions in the interstices.By the study of the thermal behaviour of(1)via thermogravimetry and temperature resolved X-ray powder diffraction it was found that the compound is stable up to approx.363 K and that the thermal expansion along c is only about 1/3 compared to a and b.