We report a comprehensive ab initio investigation of the conformers of dehydrogenated glycine radicals using the STO‐3G, 3‐21G, and aug‐cc‐pVDZ (aVDZ) basis sets and the UHF and UMP2 (H2N‐CH‐COOH and HN‐CH2‐COOH) as well as MCSCF and MRCI (H2N‐CH2‐COO) methods via two different conformational search strategies generating initial structures for optimizations by (a) removing H atoms from glycine conformers and (b) scanning torsional angles describing internal rotation along the CC, CN, and CO (except for H2N‐CH2‐COO) bonds of the radicals. We find four H2N‐CH‐COOH {InCH, IInCH, IIInCH, IVnCH} and seven HN‐CH2‐COOH {IpNH, IIpNH, IIInNH, IVpNH VnNH, VIpNH, VIIpNH} conformers with classical(adiabatic) relative energies of {0.00(0.00), 1.57(1.55), 5.25(5.03), 9.85(9.72)} and {0.00(0.00), 0.78(1.06), 1.93(2.08), 3.34(3.16), 3.39(3.29), 5.00(4.86), 9.27(8.87)} kcal/mol, respectively, obtained with UCCSD(T)‐F12b/aug‐cc‐pVTZ(+UCCSD(T)‐F12b/aVDZ ZPE correction) and four H2N‐CH2‐COO {IpCOO, IInCOO, IIIpCOO, IVnCOO} conformers with MRCI‐F12+Q/aVDZ(+MRCI/aVDZ ZPE correction) energies of {0.00(0.00), 1.65(1.64), 1.78(1.75), 2.21(2.21)} kcal/mol, where n and p denote C1 and Cs symmetry. The MRCI‐F12+Q[UCCSD(T)‐F12b] InCH → IpNH and InCH → IpCOO classical(adiabatic) isomerization energies are 18.51(17.32)[21.20(20.01)] and 31.88(31.66) kcal/mol, respectively.

中文翻译：

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脱氢甘氨酸异构体的构象物

我们报告了使用 STO-3G、3-21G 和 aug-cc-pVDZ (aVDZ) 基组以及 UHF 和 UMP2（H2N-CH-COOH 和 HN-CH2 -COOH) 以及 MCSCF 和 MRCI (H2N-CH2-COO) 方法通过两种不同的构象搜索策略生成用于优化的初始结构 (a) 从甘氨酸构象异构体中去除 H 原子和 (b) 扫描描述内旋转的扭转角沿自由基的 CC、CN 和 CO（H2N-CH2-COO 除外）键。我们发现了四种 H2N-CH-COOH {InCH, IInCH, IIInCH, IVnCH} 和七个 HN-CH2-COOH {IpNH, IIpNH, IIInNH, IVpNH VnNH, VIpNH, VIIpNH} 构象异构体，经典（绝热）相对能量为 {0.00( 0.00), 1.57(1.55), 5.25(5.03), 9.85(9.72)} 和 {0.00(0.00), 0.78(1.06), 1.93(2.08), 3.34(3.16), 3.56,4(3.8),4(4) 9. 分别用 UCCSD(T)-F12b/aug-cc-pVTZ(+UCCSD(T)-F12b/aVDZ ZPE 校正) 和四种 H2N-CH2-COO {IpCOO, IInCOO, IIIpCOO, IVnCOO} 构象异构体，MRCI-F12+Q/aVDZ(+MRCI/aVDZ ZPE 校正) 能量为 {0.00(0.00), 1.65(1.64), 1.78(1.75), 2.21(2.21,} kcal/mol和 p 表示 C1 和 Cs 对称性。MRCI-F12+Q[UCCSD(T)-F12b] InCH → IpNH 和 InCH → IpCOO 经典（绝热）异构化能分别为 18.51(17.32)[21.20(20.01)] 和 31.88(31.66) kcal/mol