title: Structural diversity in imidazolidinone organocatalysts: a synchrotron and computational study.
abstract: (S)-1-(Methylaminocarbonyl)-3-phenylpropanaminium chloride (S2 x HCl), C10H15N2O+ x Cl-, crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a single formula unit per asymmetric unit. (5R/S)-5-benzyl-2,2,3-trimethyl-4-oxoimidazolidin-1-ium chloride (R3 and S3), C13H19N2O+ x Cl-, crystallize in the same space group as S2 x HCl but contain three symmetry-independent formula units. (R/S)-5-benzyl-2,2,3-trimethyl-4-oxoimidazolidin-1-ium chloride monohydrate (R4 and S4), C13H19N2O+ x Cl- x H2O, crystallize in the space group P2(1) with a single formula unit per asymmetric unit. Calculations at the B3LYP/6-31G(d,p) and B3LYP/6-311G(d,p) levels of the conformational energies of the cation in R3, S3, R4 and S4 indicate that the ideal gas-phase global energy minimum conformation is not observed in the solid state. Rather, the effects of hydrogen-bonding and van der Waals interactions in the crystal structure cause the molecules to adopt higher-energy conformations, which correspond to local minima in the molecular potential energy surface.
authors.affiliation: School of Pharmacy, University of Nottingham, University Park, Nottingham NG7 2RD, England. jonathan.burley@nottingham.ac.uk
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Burley
authors.forename: Ryan
authors.initials: R
authors.lastname: Gilmour
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Prior
authors.forename: Graeme M
authors.initials: GM
authors.lastname: Day
mesh_terms: D002712:Chlorides / Q000737:chemistry*; D003460:Crystallization; D048289:Imidazolidines / Q000737:chemistry*; D008968:Molecular Conformation; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry; D017356:Synchrotrons
chemical_list: C527973:1-(methylaminocarbonyl)-3-phenylpropanaminium; C527974:5-benzyl-2,2,3-trimethyl-4-oxoimidazolidin-1-ium; D002712:Chlorides; D048289:Imidazolidines; D010649:Phenylalanine