Crystal packing of cubane and its nitryl-derivatives: a case of the discrete dependence of packing densities on substituent quantities. Issue 19 (28th April 2017)

• Record Type: Journal Article
• Authors: He, Xudong; Wei, Xianfeng; Ma, Yu; Lu, Zhipeng; Zhang, Chaoyang
• Is Part Of: CrystEngComm. Volume 19:Issue 19(2017)
• Page Start: 2644
• Page End: 2652
• Publication Date: 2017-04-28
• Subjects: Crystals -- Periodicals; Crystal growth -- Periodicals; Crystallography -- Periodicals; Cristaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Cristallographie -- Périodiques; 548
• DOI: 10.1039/c7ce00489c
• Languages: English
• ISSNs: 1466-8033

Abstract

Abstract : The variation of the dominance of H⋯H, H⋯O, and OO interactions results in a discrete dependence of packing densities and substituent (nitro group) amounts. Abstract : The dependence of discrete crystal density ( d c ) of a series of cubane and its nitro derivatives on the nitro group amount was understood via analogically analyzing their crystal packing. It was found that d c does not successively increase with the increase in the hydrogen atoms replacement by nitro groups because the intermolecular interactions that strongly influence the crystal packing vary from H⋯H to H⋯O and O⋯O interactions, with weak to strong and weak strength, respectively. The relatively low d c of octanitrocubane (less than that of 1, 2, 3, 4, 5, 6, 8-heptanitrocubane) is thought to be clearly due to the replacement of all the hydrogen atoms by nitro groups, rendering O⋯O interactions to be completely predominant and unfavorable for closer packing, i.e., they have a lower packing coefficient. This deduction from the crystal packing of a series of analogues of nitrocubane derivatives to understand the observed d c can be seen as a prototype to understand the crystal packing and provide a foundation for designing new CHNO explosives, in which H⋯O and O⋯O interactions are usually prevalent. Moreover, it was proposed that a specific quantity of hydrogen atoms is usually indispensable to achieve a high d c value for CHNO energetic crystals.