melem

melem is a white or pale yellow powdery solid that is insoluble in common solvents (including acetone, chloroform, methanol, water, DMF, DMSO, etc.). It is chemically stable, with a thermal decomposition temperature exceeding 500 °C. However, it is prone to further condensation reactions at temperatures above 450 °C. It must be stored at room temperature (in a cool, dry place below 15 °C), protected from light and air, and kept in an inert gas atmosphere.

High absorption efficiency: melem possesses a 1,3-s-triazine (heptazine) core structure. This large conjugated structure confers it with a strong ability to absorb ultraviolet light. Compared to traditional triazine-based absorbers (such as UV-1577), melamine has a larger conjugated plane and, in theory, a higher molar extinction coefficient, meaning it has a greater capacity to absorb ultraviolet light.
Excellent thermal stability: The structure of melem is not destroyed until temperatures exceed 500°C. This sufficiently demonstrates that the heptazine ring itself possesses extremely high thermal stability.

1,3,4,6,7,9,9b-heptaazaphenalene-2,5,8-triamine can be used as organic synthesis intermediate and pharmaceutical intermediate, mainly used in laboratory research and development process and chemical production process.

ChEBI: Melem is a heptaazaphenalene.

As a structural unit rather than a simple additive: melem is incorporated directly into the main chain or network of polymeric materials via chemical bonding (polymerisation). The resulting material thus possesses both structural properties and UV-absorbing capabilities.[1]
For high-performance coatings or films: utilising its high absorption rate coupled with thermal stability, it can be formulated into specialised coatings for application onto substrates requiring extreme weather resistance (such as outdoor architectural structures and aerospace components).[2]

Not classified

Melem 4e was synthesized by heating cyanamide 5 (Fluka, ≥98%) or ammonium dicyanamide 6 (for preparation, see ref 24) or dicyandiamide 7 (Avocado, 99%) or melamine 1a (Fluka, purum, ≥99% (NT)). The commercial products were used as purchased: 80 mg of starting material (1.90 mmol of 5, 0.95 mmol of 6, 0.95 mmol of 7, or 0.63 mmol of 1a, respectively) was filled into a glass ampule (outer diameter, 16 mm; inner diameter, 12 mm). The ampule was sealed at a length of 120 mm and heated to 450 °C (heating rate: 1 °C min-1). After about 5 h at this temperature, the ampule was slowly (2 °C min-1) cooled to room temperature. After the ampule was opened, the typical smell of ammonia was detected. At the top of the ampule, colorless crystals were found which were identified by X-ray powder diffractometry as sublimated melamine. At the bottom, a white-beige powder containing melem was isolated. Melem C6N7(NH2)3. yield 60%. Anal. calcd for melem: H, 2.75; C, 33.03; N, 64.22. Found: H, 2.98; C, 32.62; N, 62.04.

melem consists solely of carbon, nitrogen and hydrogen, and is a molecular crystal. The molecules are primarily linked by hydrogen bonds, forming two layers of molecules with different orientations. In 2003, Wolfgang Schnick and colleagues determined the crystal structure of melamine, demonstrating that it is a stable intermediate in the formation of g-C3N4. Unlike g-C3N4, which exhibits amorphous characteristics, melamine possesses good crystallinity.

[1] Akinboye, A. J., Kim, K., Park, J., Kim, Y.-S., & Lee, J.-G. (2024). Contamination of ultraviolet absorbers in food: toxicity, analytical methods, occurrence and risk assessments. Food Science and Biotechnology, 33 8, 1805–1824. https://doi.org/10.1007/s10068-024-01566-4
[2] Naveed, M., Ali, S., Iqbal, J., Hussain, M. T., & Asgher, M. (2024). Combined computational and experimental study: Synthesis, DFT-calculated and experimental characterization and application of new s-triazine based fiber reactive UV absorbers. Journal of Molecular Structure, 1298, Article 136934. https://doi.org/10.1016/j.molstruc.2023.136934