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High-resolution electron spectroscopy and structures of lithium-nucleobase (adenine, uracil, and thymine) complexes

机译:高分辨率电子光谱和锂-核碱基(腺嘌呤,尿嘧啶和胸腺嘧啶)配合物的结构

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Li complexes of adenine, uracil, and thymine were produced by laser vaporization of rods made of Li and nucleobase powders in a metal-cluster beam source and studied by pulsed-field-ionization zero-electron-kinetic-energy (ZEKE) spectroscopy and density functional theory calculations. The ZEKE measurements determined the adiabatic ionization energies of the three neutral complexes and frequencies of several vibrational modes for the metal-adenine and -uracil ions. The measured spectra were compared with spectral simulations to determine the preferred metal binding sites. For adenine, the most stable structure is formed by Li/Li+ bidentately binding to both the N7 atom of the imidazole ring and the NH2 group of the pyrimidine ring. For uracil and thymine, the ideal site for Li/Li+ coordination is the O4 atom. Although it has only a small effect on the geometries of uracil and thymine, lithium coordination forces the rotation of the NH2 group out of the adenine plane. The adiabatic ionization energies of the three complexes follow the trend of uracil (33910±5 cm−1)>thymine (33386±5 cm−1)>adenine (32240±5 cm−1), whereas their metal-ligand bond dissociation energies are about the same, (92–97) ±6 kJ mol−1. For all three complexes, the neutral bond energies are smaller than those of the corresponding ions due to a weaker electrostatic interaction and stronger electron repulsion. © 2010 American Institute of Physics Article Outline INTRODUCTION EXPERIMENTAL AND COMPUTATIONAL METHODS RESULTS AND DISCUSSION PIE spectra of Li-adenine, Li-thymine, and Li-uracil ZEKE spectrum and structure of Li-adenine ZEKE spectra and structures of Li-uracil and Li-thymine Ionization and bond dissociation energies of Li-adenine, Li-uracil, and Li-thymine CONCLUSIONS
机译:腺嘌呤,尿嘧啶和胸腺嘧啶的Li络合物是通过在金属簇束源中激光蒸发由Li和核碱基粉末制成的棒制成的,并通过脉冲场电离零电子动能(ZEKE)光谱和密度研究功能理论计算。 ZEKE测量确定了三个中性络合物的绝热电离能以及金属-腺嘌呤和-尿嘧啶离子的几种振动模式的频率。将测得的光谱与光谱模拟进行比较,以确定优选的金属结合位点。对于腺嘌呤,最稳定的结构是通过Li / Li + 与咪唑环的N7原子和嘧啶环的NH2 基团牢固地结合而形成的。对于尿嘧啶和胸腺嘧啶,Li / Li + 配位的理想位置是O4原子。尽管它对尿嘧啶和胸腺嘧啶的几何形状影响很小,但锂配位迫使NH2 基团旋转出腺嘌呤平面。三种配合物的绝热电离能遵循尿嘧啶(33910±5 cm-1)胸腺嘧啶(33386±5 cm-1)>腺嘌呤(32240±5 cm-1)的趋势。 sup>),而它们的金属-配体键解离能大致相同,为(92-97)±6 kJ mol-1 。对于所有三个络合物,由于较弱的静电相互作用和较强的电子排斥力,中性键能小于相应离子的能。 ©2010美国物理研究所文章大纲引言实验和计算方法结果与讨论Li-腺嘌呤,Li-胸腺嘧啶和Li-尿嘧啶ZEKE光谱的PIE光谱和Li-腺嘌呤ZEKE光谱的结构以及Li-尿嘧啶和Li-的结构腺嘌呤,尿嘧啶和胸腺嘧啶的胸腺嘧啶电离和键解离能

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