Inclusion complexes of a bichromophoric diester containing anthracene and naphthalene groups with alpha- and beta-cyclodextrins: thermodynamics and molecular mechanics.
Fluorescence and molecular mechanics have been used to study the inclusion complexes of the (9-anthryl)-COO-(CH2)2-OOC-(2-naphthyl) bichromophoric compound with alpha- and beta-cyclodextrins. Emission spectra upon excitation of the naphthalene group denote the presence of non-radiative energy transfer from naphthalene to anthracene, which is influenced by the type of CD. Naphthalene emission also shows two peaks whose ratio of intensities R is sensitive to the medium polarity. The stoichiometry, the formation constants and the changes of enthalpy and entropy upon inclusion of complexes formed were obtained from the change of R with CD concentration and temperature. Both complexes, in agreement with Job's plots, show 1:1 stoichiometry. Quenching, fluorescence depolarization and the analysis of R when all the guests are complexed permit us to explain the possible location of CDs in the complexes formed. Molecular mechanics calculations were also employed to study the formation of 1:1 complexes with both alpha- and betaCDs. The study was mainly performed in the presence of water as a solvent. Results seem to explain the stoichiometries and geometry for both complexes.
Serna
Leticia
L
Departamento de Química Física, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain.
Di Marino
Antonio
A
Mendicuti
Francisco
F
D000873:Anthracenes / Q000737:chemistry*; D004952:Esters / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D008962:Models, Theoretical; D008968:Molecular Conformation; D009281:Naphthalenes / Q000737:chemistry*; D012984:Software; D012997:Solvents; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013053:Spectrophotometry / Q000379:methods*; D013816:Thermodynamics; D047391:alpha-Cyclodextrins / Q000737:chemistry*; D047392:beta-Cyclodextrins / Q000737:chemistry*
D000873:Anthracenes; D004952:Esters; D009281:Naphthalenes; D012997:Solvents; D047391:alpha-Cyclodextrins; D047392:beta-Cyclodextrins