Eight most stable structures of propofol·(H2O)3 as calculated at the M06-2X/6-311++G(d,p) level. Relative energies in kJ/mol.
Two-color REMPI spectra of propofol·(H2O)n, n = 0–3 obtained in a supersonic expansion of propofol/water in 2 bars of He and with the probe laser tuned at 27 972 cm−1. The zoom also offers a comparison between the spectra of propofol·(H2O)3 obtained using He and Ne. Disappearance of some features is observed, probably due to population transfer between isomers.
Comparison between propofol·(H2O)3 2-color REMPI spectrum and the hole-burning traces obtained tuning the probe laser at 36 195 (*) and 36 255 cm−1 (**), respectively. Two isomers are detected in the expansion.
Comparison between the experimental IR/UV traces obtained for the two detected propofol·(H2O)3 conformers and the predicted spectra for some representative structures. Comparison with the complete set of calculated structures can be found in Fig. S3 of the supplementary material.10 A correction factor of 0.938 was employed to account for the anharmonicity.
Comparison between the experimental IR/UV traces obtained for the two detected propofol·(H2O)3 in ground and excited electronic states. The calculated spectra for the structures s1, s2, and s3 in their first excited electronic state are also included. CIS/6-31G(d,p) calculation level was employed in the excited state calculation. Also, a correction factor of 0.88 was used to account for the anharmonicity.
(Lower panel) Electronic ground state potential energy curve obtained using the calculated structure s2 as starting point and rotating the isopropyl group on the right in 30º steps, while the rest of the coordinates are relaxed. (Upper panel) A more detailed scan around the global minimum was performed, rotating the same isopropyl group in 10° steps. Two shallow minima separated by a very small barrier are found. Calculations performed at B3LYP/6-311++G(d,p) level. The blue lines represent a spline fit, added as an eye guide.
(Lower panel) Reaction coordinate scan from structure s2 to s1 in the electronic ground state, calculated at M06-2X/6-311++G(d,p) level. A true transition state was located. (Upper panel) Estimation of the same reaction path in the first excited electronic state, built running a single point TD-DFT calculation on each structure of the S0 path. The blue lines represent a spline fit, added as an eye guide.
Comparison between the calculated structures of propofol·(H2O)3 s2 and phenol·(H2O)3 at M06-2X/6-311++G(d,p). The atoms of phenol·(H2O)3 are shown as white spheres.
Band origins and frequencies (cm−1) of the observed OH stretching vibrations of propofol·(H2O)3 and phenol·(H2O)3.
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