title: Multiple hydrogen-bonded complexes based on 2-ureido-4[1H]-pyrimidinone: a theoretical study.
abstract: In the present work, the electronic structures and properties of a series of 2-ureido-4[1H]-pyrimidinone(UPy)-based monomers and dimers in various environments (vacuum, chloroform, and water) are studied by density functional theoretical methods. Most dimers prefer to form a DDAA-AADD (D, H-bond donor; A, H-bond acceptor) array in both vacuum and solvents. Topological analysis proved that intramolecular and intermolecular hydrogen bonds coexist in the dimers. Frequency and NBO calculations show that all the hydrogen bonds exhibit an obvious red shift in their stretching vibrational frequencies. Larger substituents at position 6 of the pyrimidinone ring with stronger electron-donating ability favor the total binding energy and free energy of dimerization. Calculations on the solvent effect show that dimerization is discouraged by the stronger polarity of the solvent. Further computations show that Dimer-1 may be formed in chloroform, but water molecules may interact with the donor or acceptor sites and hence disrupt the hydrogen bonds of Dimer-1.
authors.affiliation: Faculty of Chemistry, Institute of Functional Material Chemistry, Northeast Normal University, 130024 Changchun, Jilin, People's Republic of China.
authors.forename: Hao
authors.initials: H
authors.lastname: Sun
authors.forename: Hui Hui
authors.initials: HH
authors.lastname: Lee
authors.forename: Idriss
authors.initials: I
authors.lastname: Blakey
authors.forename: Bronwin
authors.initials: B
authors.lastname: Dargaville
authors.forename: Traian V
authors.initials: TV
authors.lastname: Chirila
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Whittaker
authors.forename: Sean C
authors.initials: SC
authors.lastname: Smith