Theoretical and X-ray studies on the cyclisation of 1-phenyl-5-(3-aryltriaz-1-en-1-yl)-1Hpyrazole- 4-carbonitriles and 2-amino-3-(3-aryltriaz-1-en-1-yl)maleonitriles: A comparison study

The present work investigates attempts to cyclise 1-phenyl-5-(3-aryltriaz-1-en-1-yl)-1H-pyrazole- 4-carbonitriles to the desired pyrazolo[3,4-d][1,2,3]triazinimine derivatives. The cyclisations were unfruitful, and a density functional theory study was performed. This revealed the 1-phenyl-5-(3-aryltriaz-1-en-1-yl)-1H-pyrazole-4-carbonitriles are more stable than the targeted pyrazolo[3,4-d][1,2,3]triazinimine derivatives, indicating that their cyclisation is thermodynamically disfavoured; the reactant 8c is more stable than the predicted six-membered ring products 9c by 5 kJ/mol. The effect of isomerisation of the methoxy-phenyl group in the self-assembly of 8c and 8d in the crystalline lattice was investigated. The intermolecular forces in solid state were analysed in the two structural isomers 8c and 8d using calculated HirshFeld surface; the analysis indicates that the intermolecular forces are stronger in 8c than 8d and hence 8c is denser than 8d by 0.071g/mL.