Pyrolysis of prominent precursor compounds for the synthesis of carbon nitride type materials (e.g., melamine, thiourea) have been studied in detail. Molecular adducts containing monoprotonated melamium C(6)N(11)H(10)(+) and melaminium HC(3)N(3)(NH(2))(3)(+) ions, respectively, have been identified as intermediates. The adduct C(6)N(11)H(10)Cl·0.5NH(4)Cl was obtained by the reaction of melamine C(3)N(3)(NH(2))(3) with NH(4)Cl at 450 °C. During the pyrolysis of thiourea, guanidinium thiocyanate was initially formed and subsequently the melamium thiocyanate melamine adduct C(6)N(11)H(10)SCN·2C(3)N(3)(NH(2))(3) was isolated at 300 °C. A second melaminium thiocyanate melamine adduct with the formula HC(3)N(3)(NH(2))(3)SCN·2C(3)N(3)(NH(2))(3) represents an intermediary reaction product that is best accessible at low pressures. The crystal structures of the compounds were solved by single-crystal XRD. Unequivocal proton localization at the C(6)N(11)H(10)(+) ion was established. A typical intramolecular and interannular hydrogen bridge and other characteristic hydrogen-bonding motifs were identified. Additionally, the adducts were investigated by solid-state NMR spectroscopy. Our study provides detailed insight into the thermal condensation of thiourea by identifying and characterizing key intermediates involved in the condensation process leading to carbon nitride type materials. Furthermore, factors promoting the formation of melamium adduct phases over melem are discussed.

The new heptazine based compounds Sr[H2C6N7O3]2·4H2O and Sr[HC6N7(NCN)3]·7H2O have been synthesized by metathesis reactions in aqueous solution. Crystal structures were studied by single‐crystal X‐ray diffraction and Rietveld refinement. Strontium cyamelurate tetrahydrate exhibits distorted zigzag strands embedding Sr2+ ions surrounded by crystal water molecules (Fdd2, a = 1194.0(17), b = 6358.14(97), c = 602.73(89) pm, Z = 8, GOF = 1.034, Rp = 0.033, wRp = 0.042, RB = 0.84). Strontium melonate heptahydrate crystallizes in a layer‐like structure characteristic for heptazine‐based compounds (P$\bar{1}$, a = 660.76(13), b = 1080.7(2), c = 1353.8(3) pm, α = 101.67(3), β = 101.40(3), γ = 94.60(3)°, Z = 2, R1 = 0.032, wR2 = 0.072). Additionally, the thermal behavior has been studied by DTA/TG measurements and FTIR spectroscopy data are presented.

In this contribution, we report on novel functionalized triazines, which represent new precursors for C/N/(H) compounds or suitable building blocks for carbon-based functional networks. Our results provide insights into the structural properties of molecular carbon nitride materials and their design principles. Tris(1-propynyl)-1,3,5-triazine (C3 N3 (C3 H3 )3 ) and tris(1-butynyl)-1,3,5-triazine (C3 N3 (C4 H5 )3 ) were prepared by substitution reactions of cyanuric chloride (C3 N3 Cl3 ) with prop-1-yne and but-1-yne. The crystal structure of tris(1-propynyl)-1,3,5-triazine was solved in the orthorhombic space group Pbcn (Z=4, a=1500.06 (14), b=991.48(10), c=754.42(6) pm, V=1122.03(18)×10(6)  pm(3) ), whereas tris(1-butynyl)-1,3,5-triazine crystallized in the triclinic space group P-1 (Z=6, a=1068.36(12), b=1208.68(12), c=1599.38(16) pm, α=86.67(3), β=86.890(4), γ=86.890(4)°, V=1997.7(4)×10(6)  pm(3) ). For both structures, planar triazine units and layerlike packing of the molecules were observed. Tris(1-propynyl)-1,3,5-triazine is built up from hydrogen-bonded zig-zag strands, whereas tris(1-butynyl)-1,3,5-triazine shows parallel layered arrangements. Both compounds were investigated by NMR spectroscopy, IR spectroscopy, and differential thermal analysis/thermogravimetric analysis, which provided insights into their structural, chemical, and thermal properties. In addition, tris(1-propynyl)-1,3,5-triazine was pyrolyzed and a new polymeric triazine-based compound containing mesitylene units was obtained. Its structural features and properties are discussed in detail.