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- Title
Dynamic Properties of Molecular Tweezers with a Bis(2-hydroxyphenyl)pyrimidine Backbone.
- Authors
Tsuchido, Yoshitaka; Suzaki, Yuji; Ide , Tomohito; Osakada, Kohtaro
- Abstract
4,6-Bis(2-hydroxyphenyl)-2-alkylpyrimidines with two anthryl or 9-ethylnylanthryl substituents at the positions para to the OH groups prefer a U-shaped conformation supported by two intramolecular OH ⋅⋅⋅N hydrogen bonds in the solid state and in CDCl3 solution. The compound with a hexyl substituent on the pyrimidine group and two 9-ethynylanthryl arms at the hydroxyphenyl groups forms a 1:1 complex with 2,4,7-trinitrofluorenone. Its association constant Ka was estimated to be 2100 M−1 at 298 K, which is larger than those of other molecular tweezers ( Ka<1000 M−1). DFT calculations suggested that the complex adopts a stable conformation supported by intramolecular hydrogen bonds among the OH groups and the pyrimidine ring as well as by intermolecular π-π interaction between the anthryl groups and 2,4,7-trinitrofluorenone. Addition of nBu4NF to a solution of the molecular tweezers or their complexes causes the cleavage of one or two OH ⋅⋅⋅N hydrogen bonds, formation of new O ⋅⋅⋅HF hydrogen bonds, and changes in the molecular conformation. The resulting structure of the molecular tweezers contains nonparallel anthryl groups, which do not bind the guest molecule. Photochemical measurements on 4,6-bis(2-hydroxyphenyl)-2-methylpyrimidine with two anthryl substituents showed negligible luminescence (quantum yield ϕ<0.01), owing to photoinduced electron transfer of the molecule with a U-shaped structure. However, the O-hexylated compound exhibits emission from the anthryl groups with ϕ=0.39.
- Subjects
HYDROGEN bonding; SUPRAMOLECULAR chemistry; X-ray diffraction; MOLECULAR conformation; PYRIMIDINES; INTERMOLECULAR interactions
- Publication
Chemistry - A European Journal, 2014, Vol 20, Issue 16, p4762
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201304380