Isostructural rubidium and caesium 4-(3,5-dinitropyrazol-4-yl)-3,5-dinitropyrazolates: crystal engineering with polynitro energetic species

Abstract

In the structures of the title salts, poly[[μ4-4-(3,5-dinitropyrazol-4-yl)-3,5-dinitropyrazol-1-ido]rubidium], [Rb(C6HN8O8)] n , (1), and its isostructural caesium analogue [Cs(C6HN8O8) n , (2), two independent cations M1 and M2 (M = Rb, Cs) are situated on a crystallographic twofold axis and on a center of inversion, respectively. Mutual intermolecular hydrogen bonding between the conjugate 3,5-dinitopyrazole NH-donor and 3,5-dinitropyrazole N-acceptor sites of the anions [N...N = 2.785 (2) Å for (1) and 2.832 (3) Å for (2)] governs the self-assembly of the translation-related anions in a predictable fashion. Such one-component modular construction of the organic subtopology supports the utility of the crystal-engineering approach towards designing the structures of polynitro energetic materials. The anionic chains are further linked by multiple ion–dipole interactions involving the 12-coordinate cations bonded to two pyrazole N-atoms [Rb—N = 3.1285 (16), 3.2261 (16) Å; Cs—N = 3.369 (2), 3.401 (2) Å] and all of the eight nitro O-atoms [Rb—O = 2.8543 (15)–3.6985 (16) Å; Cs—O = 3.071 (2)–3.811 (2) Å]. The resulting ionic networks follow the CsCl topological archetype, with either metal or organic ions residing in an environment of eight counter-ions. Weak lone pair–π-hole interactions [pyrazole-N atoms to NO2 groups; N...N = 2.990 (3)–3.198 (3) Å] are also relevant to the packing. The Hirshfeld surfaces and percentage two-dimensional fingerprint plots for (1) and (2) are described.

catena-Poly[[bis(diaqualithium)]-μ4-3,3′,5,5′-tetranitro-4,4′-bipyrazole-1,1′-diido]: a new moisture-insensitive alkali-metal energetic salt with a well-defined network structure

“…The geometric parameters of the {TNBPz} 2À dianion are consistent with the data for neutral H 2 (TNBPz) (Domasevitch et al, 2019) or singly charged species {H(TNBPz)} À (Domasevitch & Ponomarova, 2021). The ion adopts a twisted conformation with two pyrazole rings rotated by 54.48 (4) (Fig.…”

“…It may be postulated that the accessibility of aqua hydrogen-bond donors does not disrupt the main anionanion interactions, but rather governs elimination of less favorable nitro OÁ Á ÁO contacts. The total contributions of the C(N)Á Á ÁC(N,O) contacts in the title structure and in the very similar unsolvated Rb{H(TNBPz)} (Domasevitch & Ponomarova, 2021) are nearly identical (33.4% and 31.9%, respectively), while the impact of hydrogen bonding is best illustrated by the pronounced contraction of the OÁ Á ÁO fraction (37.4% to 11.2% in the present case). Moreover, the asymmetry of the OÁ Á ÁO plot is contrary to the patterns for the OÁ Á ÁN/NÁ Á ÁO and OÁ Á ÁC/CÁ Á ÁO contacts.…”

“…1). Although this twist is larger than 42.99 (8) for Rb{H(TNBPz)} (Domasevitch & Ponomarova, 2021), it is still unusually small, as may be compared with the even less 658…”

“…In this case, the interplanar [49.96 (10) ] and slippage angles [13.98 (15) , with respect to the centroid of the pyrazole ring] are slightly larger. This non-covalent bonding is clearly traced in every structure adopted by H 2 (TNBPz) [with very short mutual nitro contacts down to NÁ Á ÁO = 2.9115 (15) A ˚; Domasevitch et al, 2019] and its anions (Domasevitch & Ponomarova, 2021) and in fact it may be regarded as a prominent feature for the crystal chemistry of such systems. These close interactions of shape-complementary twisted molecules contribute to the relatively high packing index of 75.8%, which is at the top of the 65-75% range expected for organic solids (Dunitz, 1995).…”

“…In the present work, we address this problem with a crystal-engineering approach. The recently introduced bifunctional tecton 3,3 0 ,5,5 0 -tetranitro-4,4 0 -bipyrazole [H 2 (TNBPz)] readily affords a range of salts with alkali metal ions (Domasevitch & Ponomarova, 2021) and nitrogen bases (Gospodinov et al, 2020) and supports either coordination or hydrogen-bonded arrays in a very predictable fashion. One can anticipate that the doubled nitropyrazolate functionality could grant the connection of the Li + ions and generation of a relatively robust polymer, whereas the extended molecular framework of {TNBPz} 2À is particularly beneficial for the dense anionanion interactions because of a larger contribution of dispersion forces.…”