Isothermal titration calorimetry and 1H NMR studies on host-guest interaction of paeonol and two of its isomers with beta-cyclodextrin.
Thermodynamic parameters of inclusion complex of beta-cyclodextrin (beta-CD) with paeonol and two of its isomers in aqueous solution have been determined with nano-watt-order isothermal titration calorimetry (ITC) and the host-guest inclusion structure has been investigated by using 1H NMR spectra at 298.2 K. The analysis of thermodynamic data reveals that stoichiometry of beta-CD complex with paeonol (Pae) or acetovanillone (Ace) is 1:1 whereas the inclusion complex of beta-CD with 2-hydroxyl-5-methoxyacetophone (Hma) is in 1:1 coexistence with 2:1 stoichiometry. Further analysis indicates that formation of all the complexes is simultaneously driven by enthalpy and entropy, the inclusion complexation of Pae.beta-CD, Ace.beta-CD and Ham.beta-CD2 is predominantly driven by entropy while Ham.beta-CD by enthalpy. The 1H NMR spectra data provide clear evidence of the inclusion phenomena, which shows that the aromatic ring of the guest molecule insert itself into the torus from the narrow side of the cavity.
Sun
De-Zhi
DZ
College of Chemistry and Chemical Engineering, Liao Cheng University, Wenhua Road, Liaocheng, Shandong 252059, PR China. sundezhisdz@163.com
Li
Ling
L
Qiu
Xiao-Mei
XM
Liu
Feng
F
Yin
Bao-Lin
BL
D000098:Acetophenones / Q000737:chemistry*; D002151:Calorimetry; D004339:Drug Compounding; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D015394:Molecular Structure; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics; D017186:Titrimetry; D014867:Water / Q000737:chemistry; D047392:beta-Cyclodextrins / Q000737:chemistry*
D000098:Acetophenones; D012997:Solvents; D047392:beta-Cyclodextrins; D014867:Water; C013638:paeonol; C056165:acetovanillone; C031215:betadex