Conglomerate crystallization behavior of racemic [Co(N4)(aminoacidato)] 2+ complexes

• Published in: Crystal engineering Vol. 4; no. 2; pp. 141 - 157
• Main Authors: Hu, Xiaopeng, Cai, Jiwen, Chen, Caihong, Chen, Xiao-Ming, Liang-Nian Ji
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.06.2001
• Subjects: Amino acid; Cobalt(iii); Conglomerate crystallization; Triethylenetetramine; Tris(2-aminoethyl)amine; Cobalt(iii); Amino acid; Tris(2-aminoethyl)amine; Conglomerate crystallization; Triethylenetetramine
• ISSN: 1463-0184
• DOI: 10.1016/S1463-0184(01)00004-1

Crystal structures, absolute configurations, and crystalline packing features of nine complexes, namely, cis- α-Λ-(RR)( δλδ)-[Co(trien)(D-histidinato)](ClO 4) 2·2H 2O 1, cis- β 1-Δ-(RR)( λδδ)- [Co(trien)(L-asparaginato)](ClO 4) 2 2, cis- β 2-Λ(SS)( λλδ)-[Co(trien)(L-valinato)](ClO 4) 2·H 2O 3, cis- β 2-Δ-(RR)( δδλ)[Co(trien)(D-methioninato)](ClO 4) 2 and its enantiomer 4, trans(N,t-N)-[Co(tren)(DL-leucinato)]X 2, (X=ClO 4 − 5, BF 4 − 6, PF 6 − 7), and trans(N,t-N)-[Co(tren)(DL- methioninato)]X 2 (X=Br − 8, Cl −(BF 4 −) 9) (trien=triethylenetetramine, tren=tris(2-aminoethyl)amine), have been determined. All compounds were prepared from racemic DL-amino acid. 1– 3 crystallize as conglomerates. 5– 7 are isomorphous and crystallize as the so-called conglomeratic solids. While 4, 8 and 9 undergo racemic crystallization. In 1– 7, the carboxylic oxygen of the amino acid forms double hydrogen bonds with the amino hydrogen atoms of N4 and/or amino acidato of an adjacent cation. By these hydrogen bonds, cations having the same chirality are linked together into helical string. In the isomorphous 8 and 9, the cation containing L-methionine interacts with a cation containing D-methioninine, through hydrogen bonds, to form a racemic pair, and no spiral string arrangements are observed.