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제117회 대한화학회 학술발표회, 총회 및 기기전시회 안내 Direct observation of bond formation in solution with femtosecond X-ray scattering

2016년 3월 23일 15시 56분 12초
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목 11시 : 02분
한국다우케미칼 우수논문상 수상자 구두발표
저자 및
김종구, 김경환, 왕기영, 김태우, 기호성, 조준범, 박성준, 김중한1, 유 룡2, 김정호3, 이효철*
한국과학기술원(KAIST) 화학과, Korea
1가톨릭대학교 화학과, Korea
2기초과학연구원 나노물질및화학반응연구단, Korea
3인하대학교 화학과, Korea
Every chemical reaction consists of a series of the making and breaking of atomic bonds and thus it is essential to elucidate detailed structural dynamics of the bond-making and breaking processes for complete understanding of chemical reactions. Especially, the ultrafast dynamics of bond-making process have not been thoroughly studied since bimolecular nature of the bond making makes it difficult for its initiation to be synchronized with laser excitation. In this study, we chose an appropriate molecular system, [Au(CN)2-]3, to scrutinize bond-making process in solution. In the ground state of [Au(CN)2-]3, three gold atoms are gathered by a non-covalent interatomic interaction called aurophilicity.1 Since the three gold atoms exist in a same solvent cage, covalent bond formations between adjacent gold atoms can be initiated by laser excitation without being limited by slow diffusion. We used femtosecond time-resolved X-ray solution scattering (TRXSS) to visualize the moment of the bond formation in the gold trimer complex with the atomic-level resolution. By making use of femtosecond X-ray pulses generated from an X-ray free electron laser (XFEL), time resolution of X-ray solution scattering experiment had been improved down to subpicosecond so that it was possible to keep track of ultrafast bond formation in the gold complex. Kinetic and structural analyses indicates that covalent bond formation and bent-to linear structural transition take place within 500 fs and subsequent bond contraction and tetramer formation occur with time constants of 1.6 ps and 3 ns, respectively.2

1) Wang, S. G. et al. Quasi-relativistic density functional study of aurophilic interactions. J. Am. Chem. Soc. 126, 1266–1276 (2004).
2) Kim, K. H. et al. Direct observation of bond formation in solution with femtosecond X-ray scattering. Nature 518, 385–389 (2015).