Interaction of 4-hydroxybiphenyl with cyclodextrins: effect of complex structure on spectroscopic and photophysical properties.
The structures, spectroscopic and photophysical properties of the inclusion complexes between 4-OH-biphenyl and cyclodextrins (CD) in water were studied theoretically and experimentally. The complex structures were predicted using a dynamic Monte Carlo procedure including solvation effects and analyzed via computed and experimentally determined circular dichroism. The interpretation of the induced circular dichroism spectra indicated the formation of stable 2:2 complexes between the probe and alpha-CD, while 1:1 structures account for the circular dichroism induced by beta- and gamma-CD. Fluorescence emission quantum yields and lifetimes, measured as a function of the CD concentration, confirmed the formation of this higher order complex with alpha-CD. Prototropic equilibration in the singlet excited state was found to be depressed in 2:2 complexes due to the hydrophobic environment of the OH groups, while it remained unperturbed in 1:1 complexes, where the substituent is exposed to the aqueous environment. Triplet-triplet absorption and triplet quenching data supported this interpretation. The photophysical properties of both the 1:1 and the 2:2 complexes are characterized by a significant reduction of the nonradiative decay rates.
Bortolus
P
P
Istituto di Fotochimica e Radiazioni d'Alta Energia, CNR Area della Ricerca, Bologna, Italy. monti@frae.bo.cnr.it
Marconi
G
G
Monti
S
S
Mayer
B
B
Köhler
G
G
Grabner
G
G
D001713:Biphenyl Compounds / Q000737:chemistry*; D002942:Circular Dichroism; D003912:Dextrins / Q000737:chemistry*; D008958:Models, Molecular; D009010:Monte Carlo Method; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D013696:Temperature
D001713:Biphenyl Compounds; D003912:Dextrins; C019046:4-phenylphenol