水溶液中稀土离子与甘氨酸、丝氨酸、天冬氨酸作用的^(13)C NMR研究

^(13)C NMR STUDY OF INTERACTION BETWEEN LANTHANIDE IONS AND GLYSINE,SERINE AND ASPARTIC ACID IN AQUEOUS SOLUTION

测定了酸性水溶液中甘氨酸、丝氨酸和天冬氨酸稀土络合物(Ln=La、Pr、Nd、Eu、Tb、Dy、Ho、Er、Tm和Yb)的^(13)C诱导位移。对位移试剂的分析指出,三种氨基酸通过α-羧基以双齿形式配位于稀土,配位键长为0.23nm～0.25nm,天冬氨酸的y-羧基也是配位基团。由本文与文献中已报道的各种氨基酸稀土络合物的^(13)C诱导位移的系统分析表明,配体^(13)C超精细偶合常数A值和结构因子G值有如下规律:(1)│A(C_0)│<│A(C_α)│;A(C_0)为正,A(C_α)为负;(2)│G(C_0)│>│G(C_α)│;配体碳核的G均为负值。

13C shifts of amino acids, Gly、Ser and Asp,induced by lanthanide ions,La3+ 、 Pr3+、Nd3+、Eu3+、Tb3+、Dy3+、 Ho3+、Er3+、Tm3+ and Yb3+, were measured in acidic aqueous solution. An analysis of 13C lanthanide-induced shifts (LISs) indicates that these three amino acids are bidentately coordinated to Ln through their α-carboxyl groups with Ln-0 bond length of 0.23nm ~0.25nm. γ-carboxyl group is also involved in coordination for aspartic acid. By systematically analyzing 13C LISs in this paper and previously reported for various α-amino acid-Ln complexes, the following general conclusions are drawn about hyperfine coupling constant A and geometric factor G for ligand carbon nuclei: (l)|A(C0)|<|A(Ca)| with a positive sign for A(C0) and a negative one for A (Ca); (2) G values are negative for all ligand carbon nuclei with |G(C0)|>|G(Ca)|.