Crystallization of Two 1-D Coordination Polymers Building by 5-Sulfoisophthalic Acid and Lanthanide Ions by Partial Hydrolysis of Collagen

This paper intends to show how to use collagen to assist in obtaining single crystals of small molecules of two one-dimensional coordination polymers built by 5-sulfoisophthalic acid and lanthanide ions. The crystals were grown at room temperature and crystalline forms appeared into viscous solution exhibiting well-shaped faces and large volumes with small amount of samples. The use of collagen in the system prevents the formation of precipitate, an advantage when compared to many crystals obtained in pure solution. The samples, Nd(5SIS)·(DMF)2·5H2O (1) and [La(5sis)·8H2O] (2), have been prepared and characterized by single-crystal X-ray diffraction and vibrational spectroscopic (Raman and FT-IR) analyses. The results have shown that the compounds belong to the monoclinic system and it is stabilized by a complex hydrogen bonds network. Coordination environment of metals tend to have more ionic character in their bonds. The advantages and limitations of the use of collagen in small molecule crystallization have also been discussed.