Discrete Cuboidal 15- and 16-Membered Water Clusters in Brucine 3.86-Hydrate, Water Release and Its Consequences

Abstract

Up to now, three brucine hydrates are known, brucine di-, tetra-, and 5.25-hydrate. All of them were obtained from solutions containing the additive diethanolamine, adenosine, and urea, respectively. Studying the role of the additives on crystallization of the brucine hydrates, we obtained a new, kinetically favored brucine 3.86-hydrate. In crystals of brucine 3.86-hydrate, large 15- and 16-membered water clusters of cuboidal topology are encapsulated in cages formed between honeycomb-like brucine layers. Dehydration of the brucine hydrate leads to formation of the known anhydrous brucine, giving insight into a mechanism of the dehydration process, in which a shift of brucine ribbons in the honeycomb-like layers leads to an openining of channels and water release. A collapse of brucine layers after the water release results in formation of the common anhydrous brucine. The anhydrous brucine undergoes a phase transition at 249 K in the cooling mode and at 277 K in the heating mode. The phase transition is attributable to a huge shift of brucine corrugated layers in relation to each other. The phase transition for anhydrous brucine obtained by dehydration is accompanied by thermal effects one order larger than anhydrous brucine, obtained by crystallization from acetone solution.

Why Do Hydrates (Solvates) Form in Small Neutral Organic Molecules? Exploring the Crystal Form Landscapes of the Alkaloids Brucine and Strychnine

“…5 kJ mol –1 less stable than the global conformational energy minimum (see section 1.1 of the Supporting Information). So far, two anhydrous ( AH and AH LT ) and 20 solvate structures have been reported: four hydrates showing a different water:brucine ratio (2:1, 4:1, 3.86:1 and 5.25:1),55,58,59 and 16 solvates, including four mixed solvates 56,58,59,50,57…”

“…The low temperature anhydrate ( AH LT ) has been reported to be enantiotropically related to AH . The AH to AH LT transformation occurs upon cooling at −24 °C and the reversible AH LT to AH back transformation at 36 °C upon heating 55. Slurry experiments in organic solvents showed that the thermodynamic transition point between the polymorphic pair AH / AH LT is lower than 10 °C 37…”

“…The third hydrate, HyC (YOYZIX55), crystallizes in the form of thin long needles in the monoclinic space group C 2, with two brucine molecules in the asymmetric unit. HyC and the two anhydrate forms share sheets of the left-handed helical tapes (Figure 3).…”

“…Lattice parameters and space group of the same phase were reported in 1930 by Marwick (CSD-Refcode: ZZZUEE),49 followed by full structure determinations performed by Golver (ZZZUEE01),50 Mostad (ZZZUEE02),51 Messerschmidt (ZZZUEE03- ZZZUEE06),52 and Zharylgasina (ZZZUE07) 53. In contrast, brucine shows a rich solid form landscape: two anhydrates (MAJRIZ54 – a low temperature anhydrate AH LT and MAJRIZ0155– the commercially available AH ), twelve solvates with organic solvents (JIFWEB,56 JIFWIF, 56 JIFWOL,56 JIFWUR,56 PIGNUP,56 PIGPAX,56 PIGPEB,56 PIGPIF,56 PIGPOL,56 PIGPUR,56 PIGQAY56 and MAJROF54), four heterosolvates (‘mixed’ solvates) with water and organic solvent molecules (DAFFUL,50 MAJRUL,54 HIDGOS57 and HIDGUY57), and four hydrates ( HyA : dihydrate, CIKDOQ58; HyB : tetrahydrate, ZZZPRW01;59 HyC : 3.86-hydrate, YOYZIX55 ; a 5.25-hydrate: UCOJIG59). The HyC structure was published after we finished our experimental and computational work on this brucine phase.…”

Intermolecular Interactions in Functional Crystalline Materials: From Data to Knowledge

“…Such channels can be not only dehydrated but also substituted with other solvents [300,301]. The solid dehydration with prominent atomic movement traced with single-crystal or powder X-Ray diffraction can shed light on a more complex mechanism of water loss [302][303][304][305][306]. Various mobility of the water clusters incorporated within the pores and H-bonding waters that structure these pores was demonstrated in Refs.…”