Combinatorial Vibration-Mode Assignment for the FTIR Spectrum of Crystalline Melamine: A Strategic Approach toward Theoretical IR Vibrational Calculations of Triazine-Based Compounds

Abstract

Although polymeric graphitic carbon nitride (g-C3N4) has been widely studied as metal-free photocatalyst, the description of its structure still remains a great challenge. Fourier transform infrared (FTIR) spectroscopy can provide complementary structural information. In this paper, we reconsider the representative crystalline melamine and develop a strategic approach to theoretically calculate the IR vibrations of this triazine-based nitrogen-rich system. IR calculations were based on three different models: a single molecule, a 4-molecule unit cell, and a 32-molecule cluster, respectively. By this comparative study the contribution of the intermolecular weak interactions were elucidated in detail. An accurate and visualized description on the experimental FTIR spectrum has been further presented by a combinatorial vibration-mode assignment based on the calculated potential energy distribution of the 32-molecule cluster. The theoretical approach reported in this study opens the way to the facile and accurate assignment for IR vibrational modes of other complex triazine-based compounds, such as g-C3N4.

Reduced Oxygenated g‐C3N4 with Abundant Nitrogen Vacancies for Visible‐Light Photocatalytic Applications

“…[3] Some crystalline phases of carbonn itride, such as b-C 3 N 4 and cubic-C 3 N 4 ,a re wellknown fort heir hardness and low stretchability,w hereas g-C 3 N 4 has exhibited great potential for applicationi nt he fields of photocatalysis [4] and bioimaging. [5] g-C 3 N 4 has ag ood conjugate lamellar structure, similart ot hat of graphene; [6] furthermore, it possessest he energy band structure of as emiconductor, [7] and its molecular skeleton structure [8] is able to undergo variouschemical modifications. g-C 3 N 4 is ar apidly developed photocatalytic material that is widely used for air cleaning, [9] organic pollutant degradation, [10] and hydrogen production [11] owing to its low costs, high chemical stability, [4a] and proper band structure.…”

Li–Ion‐Conducting Pillar‐Like Graphitic Carbon Nitrides as Novel Anodes for Li–Ion Batteries

“…The sharp absorption bands at 1474 and 1642 cm −1 indicates the stretching of the C=N connectivity. The absorption bands at 1248, 1322, 1415 and 1570 cm −1 in T‐gCN is attributed to the C−N stretching vibration modes,, which have a much lower intensity in T‐gCNP. The absorbance in the 3000–3500 cm −1 region following K 2 Cr 2 O 7 treatment is indicative of the appearance of –COOH stretching.…”

Investigation on the Stability of Derivative Melam from Melamine Pyrolysis under High Pressure

“…The FTIR spectra of melamine, melam [ 20 ], LTDP, and the sample obtained at 5 GPa and at different temperatures are shown in Figure 3 . The detailed FTIR data of melam [ 20 ], melamine [ 38 ], and the samples are listed in Table 1 . The following characteristic vibrations in the FTIR spectrum are given on the basis of the molecular structure of melam [ 20 , 22 ]: The band around 808 cm −1 can be attributed to the bend vibration mode of the sextant ring; the absorption bands at 1250 cm −1 are the NH 2 shearing vibration modes; the peaks around 1340 cm −1 can be inferred for the C−N stretching modes; the absorption region between 1400 and 1700 cm −1 can be assigned to the coupling vibrations between NH 2 shearing and C=N stretching modes, thus providing evidence for the structure of the triazine ring to be retained; and the peaks found between 3100 and 3500 cm −1 verify the presence of NH or NH 2 groups.…”