title: Towards an understanding of the propensity for crystalline hydrate formation by molecular compounds.
abstract: Hydrates are technologically important and ubiquitous yet they remain a poorly understood and understudied class of molecular crystals. In this work, we attempt to rationalize propensity towards hydrate formation through crystallization studies of molecules that lack strong hydrogen-bond donor groups. A Cambridge Structural Database (CSD) survey indicates that the statistical occurrence of hydrates in 124 molecules that contain five- and six-memberedN-heterocyclic aromatic moieties is 18.5%. However, hydrate screening experiments on a library of 11N-heterocyclic aromatic compounds with at least two acceptor moieties and no competing hydrogen-bond donors or acceptors reveals that over 70% of this group form hydrates, suggesting that extrapolation from CSD statistics might, at least in some cases, be deceiving. Slurrying in water and exposure to humidity were found to be the most effective discovery methods. Electrostatic potential maps and/or analysis of the crystal packing in anhydrate structures was used to rationalize why certain molecules did not readily form hydrates.
authors.affiliation: Department of Chemical Sciences, Bernal Institute, University of Limerick , Co. Limerick, Ireland.
authors.forename: Alankriti
authors.initials: A
authors.lastname: Bajpai
authors.affiliation: Department of Chemical Sciences, Bernal Institute, University of Limerick , Co. Limerick, Ireland.
authors.forename: Hayley S
authors.initials: HS
authors.lastname: Scott
authors.affiliation: Department of Chemistry, CHE 205, University of South Florida , 4202 East Fowler Avenue, Tampa, Florida 33620, USA.
authors.forename: Tony
authors.initials: T
authors.lastname: Pham
authors.affiliation: Department of Chemical Sciences, Bernal Institute, University of Limerick , Co. Limerick, Ireland.
authors.forename: Kai-Jie
authors.initials: KJ
authors.lastname: Chen
authors.affiliation: Department of Chemistry, CHE 205, University of South Florida , 4202 East Fowler Avenue, Tampa, Florida 33620, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Space
authors.affiliation: Department of Chemical Sciences, Bernal Institute, University of Limerick , Co. Limerick, Ireland.
authors.forename: Matteo
authors.initials: M
authors.lastname: Lusi
authors.affiliation: Department of Chemical Sciences, Bernal Institute, University of Limerick , Co. Limerick, Ireland.
authors.forename: Miranda L
authors.initials: ML
authors.lastname: Perry
authors.affiliation: Department of Chemical Sciences, Bernal Institute, University of Limerick , Co. Limerick, Ireland.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zaworotko
keywords: CSD survey; N-heterocyclic aromatic compounds; electrostatic potential; hydrate screening experiments; hydrogen bonding; molecular hydrates