학술논문
금속 이온과 배위 결합한 아마이드 결합의 회전 장벽 변화 연구 / Investigation of the change in the Rotational Barrier around Metal Ion Coordinated Amide Bond
Document Type
Dissertation/ Thesis
Author
Source
Subject
Language
Korean
Abstract
합성된 시료는 금속 이온과 결합 전과 후, 아마이드 결합의 회전 장벽 변화를 측정하기 위해 온도 변화에 따른 NMR실험과 컴퓨터를 이용하여 양자 화학 계산을 하였다. 합성된 시료는 tert-butyl 2,2',2''-(10-(2-(diethylamino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetate(DO3A-AA)이다. 온도 변화에 따른 NMR실험으로 coalescence temperature(TC)분석을 하여 아마이드 결합의 회전 장벽을 계산하였고 금속 이온과 배위 결합한 시료의 회전 장벽은 결합 전보다 증가하였다. 컴퓨터를 이용한 이론적인 계산을 통해 깁스에너지와 결합길이를 측정하였다. 이러한 실험의 결과로 아마이드 산소와 질소의 비공유 전자쌍이 결합에 참여하면서 C-N 결합의 이중 결합 세기가 증가한 것을 확인하였다.
The rotational barrier about the C-N bonds in the complex of 1,4,7,10-Tetraazacyclododecane-1,4,7-triacetic acid, 10-[2-(diethylamino)-2-oxoethyl]-,1,4,7-tris(1,1-dimethylethyl) ester with metal ion was investigated by Variable Temperature(VT) NMR spectroscopy and computational calculations with the GAUSSIAN 09W. From the VT-NMR experiment, rotational barriers about the C-N bond have been determined with Gibbs energy by the line-shape and Coalescence Temperature(TC) analyses. On the other hand, from the computational calculations, as the condition of 6-311G(d) and GENECP basis set with the charge of metal ion and singlet spin, the Gibbs energy was calculated by using the density functional theory(DFT)-B3LYP method.When the analyte forms the metal complex, the lone pair electrons of nitrogens in cyclododecane ring, ester oxygens and amide oxygen make coordinate bonds with metal ion. Consequently, we could observe the changes in the chemical shift about CH3 peak of N-CH2-CH3 groups in 1H NMR spectra of various temperature before and after the complexation with metal ion. It seems that the amide nitrogen donates more electrons to C-N bond when the electrons of the amide oxygen participate in the coordinate bond of metal complex, which means that the double bond character of C-N bond becomes stronger and increases the rotational barrier around C-N bond. This can be verified from the NMR experiments and computational calculations.
The rotational barrier about the C-N bonds in the complex of 1,4,7,10-Tetraazacyclododecane-1,4,7-triacetic acid, 10-[2-(diethylamino)-2-oxoethyl]-,1,4,7-tris(1,1-dimethylethyl) ester with metal ion was investigated by Variable Temperature(VT) NMR spectroscopy and computational calculations with the GAUSSIAN 09W. From the VT-NMR experiment, rotational barriers about the C-N bond have been determined with Gibbs energy by the line-shape and Coalescence Temperature(TC) analyses. On the other hand, from the computational calculations, as the condition of 6-311G(d) and GENECP basis set with the charge of metal ion and singlet spin, the Gibbs energy was calculated by using the density functional theory(DFT)-B3LYP method.When the analyte forms the metal complex, the lone pair electrons of nitrogens in cyclododecane ring, ester oxygens and amide oxygen make coordinate bonds with metal ion. Consequently, we could observe the changes in the chemical shift about CH3 peak of N-CH2-CH3 groups in 1H NMR spectra of various temperature before and after the complexation with metal ion. It seems that the amide nitrogen donates more electrons to C-N bond when the electrons of the amide oxygen participate in the coordinate bond of metal complex, which means that the double bond character of C-N bond becomes stronger and increases the rotational barrier around C-N bond. This can be verified from the NMR experiments and computational calculations.