Mass-Analyzed Threshold Ionization of the trans-1-Naphthol−Water Complex: Assignment of Vibrational Modes, Ionization Energy, and Binding Energy

Cation Vibrations of 1-Methylnaphthalene and 2-Methylnaphthalene through Mass-Analyzed Threshold Ionization Spectroscopy

Vibrationally resolved cation spectra of 1-methylnaphthalene (1MN) and 2-methylnaphthalene (2MN) were obtained using the two-color resonant two-photon mass-analyzed threshold ionization (MATI) spectroscopy. MATI spectra were obtained through ionization via several intermediate vibronic levels. Due to hindrance effect, no spectral features related to methyl torsion were observed in the MATI spectra of 1MN. By contrast, most of the in-plane ring deformation vibrations of the 2MN cation were found to couple with methyl torsion because of its small internal rotational barrier. These experimental findings were well supported by our theoretical calculations.

Mimicking anesthetic-receptor interactions in jets: the propofol-isopropanol cluster

The interaction of the general anesthetic propofol with an individual residue of threonine in the membrane receptors has been modeled in the gas phase by examining the adduct of propofol with the isopropanol side-chain. We determined the structural preferences of the cluster using a combination of mass-resolved laser spectroscopy and quantum mechanical calculations. The first electronic transition of propofol-isopropanol was recorded with vibrational resolution using resonant two-photon ionization (R2PI) and ion dip IR spectroscopy. The spectra obtained were compared with density-functional calculations (DFT) using the M06-2X functional in order to obtain the cluster's structure. Three isomers have been detected. The results suggest that propofol acts as a Brønsted acid, donating a proton to the isopropanol molecule in a conformation that resembles that of propofol-water, but displaced towards the aromatic ring, due to the interaction with the aliphatic side of isopropanol. The higher affinity of propofol for isopropanol compared to water may correlate with the biological role of propofol at the protein binding site. On the other hand, propofol shows a similar affinity for isopropanol and phenol, which could explain the mobility that propofol experiences inside the GABAA cavity.

Microsolvation effects on the π*←π electronic transitions in simple aromatic chromophores: The role of the Slater-type Gaussian orbitals in the complete active space self-consistent field approach

One of the most studied feature of aromatic molecular clusters in the gas phase is the shift of the pi*<--pi electronic transitions between the bare aromatic chromophore and its clusters. In the present ab initio complete active space self-consistent field study the coupling of the basis set superposition error and counterpoise procedure and a combination of Pople- and Slater-type Gaussian basis sets has been proven to reproduce quantitatively the gas-phase experimental shifts. The quantal results are here analyzed with respect to the electrostatic and polarization forces and electron density differences, and connected with the sign of the shifts of the electronic transitions.