Use of Melem as a Nucleophilic Reagent to Form the Triphthalimide C₆N₇(phthal)₃—New Targets and Prospects

Abstract

Melem (1), as one of the most important representatives of the tri-s-triazine compounds, can be used as a nucleophilic reagent in reactions with phthalic acid derivatives. The synthesis of 2,5,8-triphthalimido-tri-s-triazine (C(6)N(7)(phthal)(3), 2) was investigated starting from phthalic anhydride or phthalic dichloride in various solvents, at different temperatures as well as in the solid state. NMR measurements (solution and solid state), IR spectroscopy and elemental analysis indicated the formation of a cyclic imide. Single-crystal structure analysis of a 1:1 adduct of 2 with nitromethane proved the molecular structure expected for a phthalimido-s-heptazine. DFT calculations were performed to obtain a better insight into the structural features of compound 2, especially the interaction of the carbonyl groups with the tri-s-triazine nitrogen atoms. The title compound 2 shows promising properties: it is thermally stable up to 500 °C in air and shows strong photoluminescence with a maximum emission at around 500 nm. The potential of the nucleophilic reaction of melem with other strong electrophiles provides new targets and prospects.

Arylthio‐ and Arylseleno‐Substituted s‐Heptazines

“…The spectra and the elemental analyses supported the assumption that threefold‐substituted products were obtained. All NMR signals for the C 6 N 7 units and the substituents were in the expected chemical shift ranges, as was typically reported for s ‐heptazine derivatives; the same holds true for the FTIR spectra (see the Supporting Information). Furthermore, we recorded the UV/Vis and fluorescence spectra of compounds 1 and 7 in CHCl 3 (Figure and see the Supporting Information, Figure S15).…”

“…The thermal stabilities of compounds 1 and 7 are below other known s ‐heptazine compounds, like C 6 N 7 (phthalimidyl) 3 (500 °C), alkalicyamelurates (≈500 °C), and potassium melonate . However, they demonstrated a higher thermal stability than melem‐derived iminophosphoranes; for example, the flame‐retardant material tris(2,5,8‐triphenoxyphosphinimino)‐ s ‐heptazine commenced decomposition at 270 °C.…”

“…For compound 1 , the UV/Vis spectrum showed two absorption bands at 302 ( ϵ =47 773 L mol −1 cm −1 ) and 321 nm ( ϵ =42 885 L mol −1 cm −1 ); furthermore, the solution showed a fluorescence at 552 nm upon irradiation at 288 nm. Most other reported s ‐heptazine compounds show fluorescence at lower wavelengths (C 6 N 7 (NH 2 ) 3 , 366 nm; C 6 N 7 Cl 3 , 468 nm; C 6 N 7 (phthalimidyl) 3 , 416 nm). As an example with a more red‐shifted emission peak, Li et al.…”

“…Furthermore, we recorded the UV/Vis and fluorescence spectra of compounds 1 and 7 in CHCl 3 (Figure and see the Supporting Information, Figure S15). Other selected molecular s ‐heptazine derivatives have been reported to show fluorescence in both the solution and solid state …”

Synthesis of Thiocyameluric Acid C6N7S3H3, Its Reaction to Alkali Metal Thiocyamelurates and Organic Tris(dithio)cyamelurates

“…Only very few molecular derivatives have directly been obtained from melem, these include triphthalimide C 6 N 7 (phthal) 3 , the triphosphinimono derivative C 6 N 7 (NPCl 3 ) 3 , the hydrazine derivative C 6 N 7 (NHNH 2 ) 3 and melemium salts such as [HC 6 N 7 (NH 2 ) 3 . ]ClO 4 ⋅H 2 O .…”