Hydrogen Bond vs pi-stacking interactions in the p-aminophenol...p-cresol dimer: an experimental an theoretical study

M. C. CAPELLO; F. J. HERNÁNDEZ; M. BROQUIER; C. DEDONDER-LARDEUX; C. JOUVET; G. A. PINO *

PHYSICAL CHEMISTRY CHEMICAL PHYSICS

ROYAL SOC CHEMISTRY

Lugar: CAMBRIDGE; Año: 2016 vol. 18 p. 31260 - 31260

1463-9076

he gas phase structure and excited state lifetime of the p-aminophenol p-cresol heterodimer havebeen investigated by REMPI and LIF spectroscopy with nanosecond laser pulses and pump?probe experiments with picosecond laser pulses as a model system to study the competition between p?p and H-bonding interactions in aromatic dimers. The excitation is a broad and unstructured band. The excited state of the heterodimer is long lived (2.5 0.5) ns with a very broad fluorescence spectrum red-shifted by 4000 cm1 with respect to the excitation spectrum. Calculations at the MP2/RI-CC2 and DFT-oB97X-D levels indicate that hydrogen-bonded (HB) and p-stacked isomers are almost isoenergetic in the ground state while in the excited state only the p-stacked isomer exists. This suggests that the HB isomer cannot be excited due to negligible Franck?Condon factors and therefore the excitation spectrum is associated with the p-stacked isomer that reaches vibrationally excited states in the S1 state