We performed M06‐L and X3LYP density functional theory calculations to characterize gas‐phase structures of [Pb·Pro‐H]⁺, [Ba·Pro‐H]⁺, and [Pt·Pro‐H]⁺ complex isomers. Two distinct isomeric structure types, namely the A‐ and H‐type are investigated for each complex for multiplicities of 1, 3, and 5; the lowest‐energy isomers of [Pb·Pro‐H]⁺ and [Ba·Pro‐H]⁺ are singlet A‐types, whereas the lowest‐energy isomer of [Pt·Pro‐H]⁺ is a singlet H‐type. Vibrational bands of each isomer are assigned based on harmonic frequency analysis over the 800–4000 cm⁻¹ range, and signature modes predicted in the spectral region below 3200 cm⁻¹ are suggested for comparison with vibrational spectroscopy results so that isomer assignments can be made. Our study provides a more direct approach for structure elucidations of the [M·Pro‐H]⁺ complexes than a previous study, which reports Boltzmann population analysis based on systematic calculations to predict the most abundant isomer of the [Pb·Pro‐H]⁺ complex.

中文翻译：

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气相中[M∙Pro‐H] +（M = Pb，Ba或Pt）配合物的密度泛函理论计算研究

我们进行了M06‐L和X3LYP密度泛函理论计算，以表征[Pb·Pro‐H] ⁺，[Ba·Pro‐H] ⁺和[Pt·Pro‐H] ⁺复杂异构体的气相结构。针对1、3、5和5的多重性，针对每种复合物研究了两种不同的异构结构类型，即A-和H-类型；[Pb·Pro‐H] ⁺和[Ba·Pro‐H] ⁺的最低能量异构体是单重态A-类型，而[Pt·Pro‐H] ⁺的最低能量异构体是单重态H-类型。根据800-4000 cm ^-1范围内的谐波频率分析，分配每个异构体的振动带，并在3200 cm ^-1以下的光谱区域中预测特征模式建议将其与振动光谱结果进行比较，以便进行异构体分配。与以前的研究相比，我们的研究为[ M ·Pro-H] ⁺配合物的结构解析提供了更直接的方法，该研究报告了基于系统计算来预测[Pb·Pro-H]最丰富异构体的玻耳兹曼种群分析。⁺复杂。