Understanding the crystalline formation of triazene N-oxides and the role of halogen π interactionsElectronic supplementary information (ESI) available: 759893, 1570873 and 1570875-1570877. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c7ce02015e

• Main Authors: Martins, Marcos A. P, Salbego, Paulo R. S, de Moraes, Guilherme A, Bender, Caroline R, Zambiazi, Priscilla J, Orlando, Tainára, Pagliari, Anderson B, Frizzo, Clarissa P, Hörner, Manfredo
• Format: Journal Article
• Published: 18.12.2017
• DOI: 10.1039/c7ce02015e

The crystallization of a series of 1-(4-halophenyl)-3-phenyltriazenide N 1-oxides ( 1-4 ) and 1-(phenyl)-3-phenyltriazenide N 1-oxide ( 5 ) was evaluated using the supramolecular cluster approach. This method is an efficient tool to assess the crystallization mechanism of compounds and, consequently, the steps involved in crystal formation. Compounds 1 and 4 show crystallization in two main steps while compounds 2 and 3 present three main steps, in which column formation occurs in the first step. The crystallization process for 5 occurs in 3 main steps, starting from a robust dimer formation (−16.82 kcal mol −1 ). Two new parameters - N CG % (topological and energetic contribution percentage) and NG/NC (energetic parameter/topological parameter ratio) - assisted in the interpretation of crystal growth. Compounds 1-4 showed N CG % = 50 in the first step while compound 5 reached only 50% of the contribution in the second step. The differences in N CG % were attributed to strong hydrogen bonds in the non-halogenated compound. The dominant parameter in each step of the crystallization process was indicated by the NG/NC parameter. The crystallization mechanism in all compounds was initially driven by an energetic process followed by a topological process. The existence of X π interactions was shown and was observed to be a consequence of a topological process and without any major contributions to crystal formation. Thermal analysis and UV-vis spectral data were also discussed regarding the properties of these compounds. Normalized parameters are presented to assist the interpretation of crystal mechanisms of a series of triazene N 1-oxides. The role of halogen π interactions is discussed.