Pressure and Laser-Induced Reactivity in Crystalline s-Triazine

Citroni, Mario; Fanetti, Samuele; Bini, Roberto

doi:10.1021/jp501350f

Cited by 18 publications

(38 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The IR spectrum of polymeric/graphitic C x N y H z is characterized by many overlapped peaks of comparable intensity between 900 and 1700 cm –1 , with the maximum of this intensity distribution peaked at about 1200 cm –1 . On the contrary, our spectra present three clear main peaks at 1330, 1450, and 1610 cm –1 , closely resembling the spectra predicted for triazine-based g-C 3 N 4 , and observed in the material recovered by the s -triazine reaction . However, the low nitrogen content of the starting material and the presence among the reaction products of amine cations more likely indicate the formation of a layered graphitic material containing a consistent amount of nitrogen atoms as impurities while maintaining a considerable order with short alkyl chains or hydrogen atoms terminating the sheets.…”

Section: Resultssupporting

confidence: 78%

Effect of Structural Anisotropy in High-Pressure Reaction of Aniline

et al. 2018

Self Cite

View full text Add to dashboard Cite

The pressure-induced reactivity of aromatic molecules in the crystal phase has been recently demonstrated to be a practicable route for the synthesis of crystalline nanothreads. The formation of these attracting materials is ascribed to stress anisotropy induced by uniaxial compression. In the case of aniline, the attainment of NH 2 -enriched carbon nanothreads above 30 GPa is related to the intrinsic crystal anisotropy due to the presence of strong directional H-bonds. Here, we have probed the reactivity of aniline crystal at lower pressure and higher temperature with the multifold purpose of testing the efficiency of H-bonds in ruling the crystal compressibility with increasing temperature; verifying the simple model based on the phonon assistance used in other cases to explain the crystal reactivity; and scaling down the synthesis of nanothreads. The reaction, monitored by infrared spectroscopy, is quantitative, but the product obtained is a hydrogenated graphitic carbon nitride. The simple model based on a reactivity driven by the lattice phonons is capable of accounting for the reactivity in the entire pressure range, whereas the difference in the products synthesized at pressures below and above 20 GPa is accounted for by the anisotropic compressibility of the unit cell due to the strong directional H-bonds. As a result, it is concluded that independent from the different products obtained, the high-pressure reactivity in aniline is always topochemical.

show abstract

Section: Resultssupporting

confidence: 78%

Effect of Structural Anisotropy in High-Pressure Reaction of Aniline

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…Particularly, the CH stretching vibrations involving sp 3 carbons (2790 cm −1 , 2882 cm −1 , 3014 cm −1 ) have weaker intensity than the products obtained from pressure-induced reaction recently. 41 …”

Section: Resultsmentioning

confidence: 99%

“…40 Recently, Fourier transform infrared (FTIR) spectra of s-triazine have been investigated up to 20.1 GPa with heating or laser irradiation. 41 Two products are generated with different concentration of N incorporated terminating groups in the range 3.5-5 GPa or above 8 GPa. However, Raman scattering data of s-triazine are available in very limited pressure range 0-4 GPa.…”

Section: Introductionmentioning

confidence: 99%

Effect of pressure on heterocyclic compounds: Pyrimidine and s-triazine

Xiong

et al. 2014

The Journal of Chemical Physics

View full text Add to dashboard Cite

We have examined the high-pressure behaviors of six-membered heterocyclic compounds of pyrimidine and s-triazine up to 26 and 26.5 GPa, respectively. Pyrimidine crystallizes in Pna2₁ symmetry (phase I) with the freezing pressure of 0.3 GPa, and transforms to another phase (phase II) at 1.1 GPa. Raman spectra of several compression-decompression cycles demonstrate there is a critical pressure of 15.5 GPa for pyrimidine. Pyrimidine returns back to its original liquid state as long as the highest pressure is below 15.1 GPa. Rupture of the aromatic ring is observed once pressure exceeds 15.5 GPa during a compression-decompression cycle, evidenced by the amorphous characteristics of the recovered sample. As for s-triazine, the phase transition from R-3c to C2/c is well reproduced at 0.6 GPa, in comparison with previous Raman data. Detailed Raman scattering experiments corroborate the critical pressure for s-triazine may locate at 14.5 GPa. That is, the compression is reversible below 14.3 GPa, whereas chemical reaction with ring opening is detected when the final pressure is above 14.5 GPa. During compression, the complete amorphization pressure for pyrimidine and s-triazine is identified as 22.4 and 15.2 GPa, respectively, based on disappearance of Raman lattice modes. Synchrotron X-ray diffraction patterns and Fourier transform infrared spectra of recovered samples indicate the products in two cases comprise of extended nitrogen-rich amorphous hydrogenated carbon (a-C:H:N).

show abstract

“…Additionally, this increase in hydrogen bonding stability (and by extension, covalent character) seems to overrule or direct other steric and electronic interactions that would otherwise exhibit more control over compressional behavior and reactivity. This is especially apparent when comparing against non-hydrogen bonded molecular crystals; for instance, although s-triazine shares the same fundamental aromatic ring system as melamine, its behavior is controlled by π interactions, resulting in susceptibility to electronic modification with pressure and increased reactivity [53,65,66], ultimately becoming irreversibly amorphous at 15.2 GPa. Similarly, benzene amorphizes into extended polyaromatic compounds at 23 GPa.…”

Section: Discussionmentioning

confidence: 99%

Evolution of Interatomic and Intermolecular Interactions and Polymorphism of Melamine at High Pressure

2018

View full text Add to dashboard Cite

Melamine (C 3 H 6 N 6 ; 1,3,5-triazine-2,4,6-triamine) is an aromatic substituted s-triazine, with carbon and nitrogen atoms forming the ring body, and amino groups bonded to each carbon. Melamine is widely used to produce laminate products, adhesives, and flame retardants, but is also similar chemically and structurally to many energetic materials, including TATB (2,4,6-triamino-1,3,5trinitrobenzene) and RDX (1,3,3,. Additionally, melamine may be a precursor in the synthesis of superhard carbon-nitrides, such as β-C 3 N 4 . In the crystalline state melamine forms corrugated sheets of individual molecules, which are stacked on top of one another, and linked by intra-and inter-plane N-H hydrogen bonds. Several previous high-pressure X-ray diffraction and Raman spectroscopy studies have claimed that melamine undergoes two or more phase transformations below 25 GPa. Our results show no indication of previously reported low pressure polymorphism up to approximately 30 GPa. High-pressure crystal structure refinements demonstrate that the individual molecular units of melamine are remarkably rigid, and their geometry changes very little despite volume decrease by almost a factor of two at 30 GPa and major re-arrangements of the intermolecular interactions, as seen through the Hirshfeld surface analysis. A symmetry change from monoclinic to triclinic, indicated by both dramatic changes in diffraction pattern, as well as discontinuities in the vibration mode behavior, was observed above approximately 36 GPa in helium and 30 GPa in neon pressure media. Examination of the hydrogen bonding behavior in melamine's structure will allow its improved utilization as a chemical feedstock and analog for related energetic compounds. Crystals 2018, 8, 265 2 of 20stacked on top of one another. When used as a salt or mixed with resins, melamine is an effective fire retardant, in part due to the release of flame-smothering nitrogen gas when burned [2]. When combined with formaldehyde, melamine forms a very durable thermosetting plastic used in a broad variety of kitchenware and household goods [3]. Despite its stability and flame-retardant properties, melamine is also very closely related, both structurally and chemically, to the widely used molecular explosives RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), TATB (2,4,6-triamino-1,3,5-trinitrobenzene), and to 2,4,6-trinitro-1,3,5-triazine, a hypothetical new explosive [4] which has not yet been successfully synthesized [5,6]. As a curiously stable cousin of these explosives, melamine is a worthwhile target of investigation in the search for new energetic materials with enhanced safety and stability while maintaining sufficient explosive potential [7].The primary motivation for studying the high-pressure behavior of melamine ultimately stems from its intermediate position between energetic species and ultra-hard materials; for instance, melamine may be a functional precursor for synthesis of a hypothetical β-C 3 N 4 phase, with a β-Si 3 N 4 structure, predicted to be a super-hard materia...

show abstract

Pressure and Laser-Induced Reactivity in Crystalline s-Triazine

Cited by 18 publications

References 42 publications

Effect of Structural Anisotropy in High-Pressure Reaction of Aniline

Effect of Structural Anisotropy in High-Pressure Reaction of Aniline

Effect of pressure on heterocyclic compounds: Pyrimidine and s-triazine

Evolution of Interatomic and Intermolecular Interactions and Polymorphism of Melamine at High Pressure

Contact Info

Product

Resources

About