Study of the Structural and the Spectral Characteristics of [C3N3(NH2)3]n (n = 1鈥?) Clusters

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• 作者：Zhenzhang Li ; Guanglei Chen ; Yuehua Xu ; Xianju Wang ; Zhoufei Wang
• 刊名：Journal of Physical Chemistry A
• 出版年：2013
• 出版时间：November 27, 2013
• 年：2013
• 卷：117
• 期：47
• 页码：12511-12518
• 全文大小：486K
• 年卷期：v.117,no.47(November 27, 2013)
• ISSN：1520-5215

文摘

Previous research has shown that interactions between melamine molecules within a cluster can give rise to the molecular self-assembly and that the spectral characteristic of melamine can be used to inspect melamine in a carrier. Although the structural and spectral characteristics of an isolated single melamine molecule and the molecular arrays on metal or semiconductor surfaces have been studied extensively, little is known about that of isolated multimolecular melamine clusters. In this work, density functional theory (DFT) calculations at the 蠅-B97XD/6-311++G(d,p) level were performed to study the structural and spectral characteristics of isolated melamine clusters [C₃N₃(NH₂)₃]_n (n = 1鈥?) in the ground state. The calculation shows that a ground-state single melamine molecule takes a quasi-planar structure. The C and N atoms of the molecule are in one plane, which we call the molecular plane, while the H atoms deviate slightly from the molecular plane. When melamine molecules gather to form a cluster, the intermolecular hydrogen bonds (IHBs) N鈥揌路路路N will arise, with the lengths of H路路路N in the range from 1.960 to 1.970 脜; the length of N鈥揌 will be elongated to 1.022 脜 from its original of 1.004 脜, the N鈥揌路路路N bond angles will be about 176掳, and the average single-bond binding energy will be approximately 鈭?.285 eV. In a multimolecular cluster, each melamine molecule still takes the quasi-planar structure. Each molecular plane in the cluster retains a planar structure, and some H atoms diverge more from their molecular planes. The molecular planes in a cluster are not coplanar, and the dihedral angle between the molecular planes of two neighboring melamine molecules ranges from 38 to 40掳. In addition, the theoretical study of the infrared (IR) spectrum and nuclear magnetic resonance (NMR) spectrum of [C₃N₃(NH₂)₃]_n (n = 1鈥?) was conducted. The results confirm the existence of IHBs in a multimolecular melamine cluster and reveal the symmetry of the electron cloud distribution in the melamine clusters. Experimental study of the IR for solid-state melamine and ¹³C NMR spectra for both solid- and liquid-state melamine samples were also carried out, in which the corresponding spectral characteristics of [C₃N₃(NH₂)₃]_n (n = 2鈥?) clusters deduced from theoretical study were observed. Findings of this study may serve as theoretical references for future identification and utilization of melamine clusters.