INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
artículos
Título:
Complexation (cucurbit[6]uril-pyrene): thermodynamic and spectroscopic properties
Autor/es:
SUELDO OCCELLO, VALERIA N.; DE ROSSI, RITA H; VEGLIA, ALICIA V.
Revista:
JOURNAL OF LUMINESCENCE
Editorial:
ELSEVIER SCIENCE BV
Referencias:
Lugar: Amsterdam; Año: 2015 vol. 158 p. 435 - 440
ISSN:
0022-2313
Resumen:
Abstract: The influence of the macrocyclic compound cucurbit[6]uril (CB6) on the photophysical properties of the fluorophore pyrene (PYR) has been studied. Guest-host interaction was observed by UV-visible spectroscopy and spectrofluorimetry. The fluorescence of PYR was significantly increased in the presence of CB6. The binding equilibrium constants for the complex with 1:1 stoichiometry were determined in HCOOH 55 % (w/v). The values of the association constants, KA, and the fluorescence quantum yield ratios between the complexed and free substrate, f PYR-CB6/f PYR, at different temperatures were (3.1 +/- 0.9) 102 M-1 and (5.1 +/- 0.2), (3.6 +/- 0.5) 102 M-1 and (5.9 +/- 0.1), (4.8 +/- 0.7) 102 M-1 and (5.5 +/- 0.1) at 15.0 C, 25.0 C and 40.0 C, respectively. The enthalpic and entropic contributions to the complexation process were determined, yielding DS = (92 +/- 3) J mol-1 K-1 and DH = (13 +/- 1) kJ mol-1. From these results it can be concluded that the complex formation is mainly driven by the entropic term. The forces involved in the complexation are interpreted from the sign and magnitude of the thermodynamic parameters obtained. The interaction is also demonstrated in the solid state by differential scanning calorimetric (DSC) measurements.