title: Conformation-changing aggregation in hydroxyacetone: a combined low-temperature FTIR, jet, and crystallographic study.
abstract: Aggregation in hydroxyacetone (HA) is studied using low-temperature FTIR, supersonic jet expansion, and X-ray crystallographic (in situ cryocrystallization) techniques. Along with quantum chemical methods (MP2 and DFT), the experiments unravel the conformational preferences of HA upon aggregation to dimers and oligomers. The O-H···O═C intramolecular hydrogen bond present in the gas-phase monomer partially opens upon aggregation in supersonic expansions, giving rise to intermolecular cooperatively enhanced O-H···O-H hydrogen bonds in competition with isolated O-H···O═C hydrogen bonds. On the other hand, low-temperature IR studies on the neat solid and X-ray crystallographic data reveal that HA undergoes profound conformational changes upon crystallization, with the HOCC dihedral angle changing from ~0° in the gas phase to ~180° in the crystalline phase, hence giving rise to a completely new conformation. These conclusions are supported by theoretical calculations performed on the geometry derived from the crystalline phase.
authors.affiliation: Department of Chemistry, University of Coimbra, Coimbra, Rua Larga 3004-535, Portugal. asharma@qui.uc.pt
authors.forename: Archna
authors.initials: A
authors.lastname: Sharma
authors.forename: Igor
authors.initials: I
authors.lastname: Reva
authors.forename: Rui
authors.initials: R
authors.lastname: Fausto
authors.forename: Susanne
authors.initials: S
authors.lastname: Hesse
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Xue
authors.forename: Martin A
authors.initials: MA
authors.lastname: Suhm
authors.forename: Susanta K
authors.initials: SK
authors.lastname: Nayak
authors.forename: Ranganthan
authors.initials: R
authors.lastname: Sathishkumar
authors.forename: Rumpa
authors.initials: R
authors.lastname: Pal
authors.forename: Tayur N Guru
authors.initials: TN
authors.lastname: Row