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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Characterization of the Conformational Probability of N-Acetyl-Phenylalanyl-NH_2 by RHF,DFT,and MP2 Computation and AIM Analyses,Confirmed by Jet-Cooled Infrared Data
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Characterization of the Conformational Probability of N-Acetyl-Phenylalanyl-NH_2 by RHF,DFT,and MP2 Computation and AIM Analyses,Confirmed by Jet-Cooled Infrared Data

机译：喷射冷却的红外数据证实了RHF，DFT，MP2计算和AIM分析对N-乙酰基-苯丙氨酰基-NH_2构象概率的表征

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Computational and experimental determinations were carried out in parallel on the conformational probability of N-Acetyl-Phenylalanine-NH_2(NAPA).Ab initio computations were completed at the BLYP/6-31 lG(df,p),B3LYP/6-31G(d),B3LYP/6-31G(d,p),and B3LYP/6-31+G(d)levels of theory,labeled L/61fp,B/6,B/6p,and B/6+,respectively.Three experimentally identified conformers were compared with theoretical data,confirming their identities as the beta_L~(anti),gamma_L~(gauche+),andgamma_L~(gauche-)(BACKBONE~(S1DECHAIN))conformers.Evidence comes from matching experimental and theoretical data for all three constituent N-H stretches of NAPA,with a DELTA_(Experimental-Theoretical)= ~1- 3 cm~(-1),~0-5 cm~(-1),and ~l- 6 cm~(-1),at the L/61fp and B/6+ levels,respectively.Corrected-ZPE relative energies were computed to be 0.14,0.00,0.26 and 0.00,0.67,0.57(kcal*mol~(-1))for the beta_L~(anti),gamma_L~(gauche+),and gamma_L~(gauche-)-conformers,respectively,at the L/61fp and B/6+ levels,respectively.The MP2/6-31+G(d)level of theory was subsequently found to give similar relative energies.Characterization of the intramolecular interactions responsible for red and blue shifting of the N-H stretches showed the existence of the following intramolecular interactions:C=O[i]...HN_[i],(Ar_[i]-C_gamma...HN_[i+1],(Ar_[i]-C_delta-H...O=C_[i-1] for beta_L~(anti);C=O_[i-1]...HN_[i+1],(Ar_[i])-C_gamma...HN_[i+1],(Ar_[i])-C-H...O=C_[i] for gamma_L~(gauche+);and C=O_[i-1] -HN_[i+1] for gamma_L~(gauche-)/Each of these interactions were further investigated and subsequently characterized by orbital population and Atoms-In-Molecules(AIM)analyses,with the identity of overlap and bond critical points(BCP)serving as 'scoring criteria',respectively.Experimental and theoretical carbonyl stretches were also compared and showed good agreement,adding further strength to the synergy between experiment and theory.
机译：同时对N-乙酰基-苯丙氨酸-NH_2（NAPA）的构象概率进行计算和实验测定。从头算在BLYP / 6-31 lG（df，p），B3LYP / 6-31G（ d），B3LYP / 6-31G（d，p）和B3LYP / 6-31 + G（d）的理论水平，分别标记为L / 61fp，B / 6，B / 6p和B / 6 +。将三个实验确定的构象异构体与理论数据进行比较，确认它们的身份为beta_L〜（反），gamma_L〜（gauche +）和gamma_L〜（gauche-）（BACKBONE〜（S1DECHAIN））构象异构体。对于NAPA的所有三个组成部分NH延伸，DELTA_（实验理论）=〜1-3 cm〜（-1），〜0-5 cm〜（-1）和〜l-6 cm〜（-1 ），分别在L / 61fp和B / 6 +水平上计算.β_L〜的校正ZPE相对能量为0.14,0.00,0.26和0.00,0.67,0.57（kcal * mol〜（-1））。 （anti），gamma_L〜（gauche +）和gamma_L〜（gauche-）构象分别在L / 61fp和B / 6 +水平上。MP2/随后发现6-31 + G（d）的理论能级提供相似的相对能量。负责NH延伸的红色和蓝色移动的分子内相互作用的特征表明存在以下分子内相互作用：C = O [i] ... HN_ [i]，（Ar_ [i] -C_gamma ... HN_ [i + 1]，（Ar_ [i] -C_delta-H ... O = C_ [i-1] for beta_L〜（anti ）; C = O_ [i-1] ... HN_ [i + 1]，（Ar_ [i]）-C_gamma ... HN_ [i + 1]，（Ar_ [i]）-CH ... O对于gamma_L〜（gauche +）= C_ [i];对于gamma_L〜（gauche-）C = O_ [i-1] -HN_ [i + 1] /进一步研究这些相互作用中的每一个，然后通过轨道人口和分子内原子（AIM）分析以重叠和键临界点（BCP）的身份分别作为“得分标准”。实验和理论上的羰基拉伸也进行了比较，并显示出良好的一致性，进一步增强了协同作用在实验和理论之间。

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