Theoretical study of neutral and cationic complexes involving phenol

The structures of the van der Waals bonded complexes of phenol with one and two argon atoms have been determined using rotationally resolved electronic spectroscopy of the S(1)<--S(0) transition. The experimentally determined structural parameters were compared to the results of quantum chemical calculations that are capable of properly describing dispersive interactions in the clusters. It was found that both complexes have pi-bound configurations, with the phenol-Ar(2) complex adopting a symmetric (1mid R:1) structure. The distances of the argon atoms to the aromatic plane in the electronic ground state of the n=1 and n=2 clusters are 353 and 355 pm, respectively. Resonance-enhanced multiphoton ionization spectroscopy was used to measure intermolecular vibrational frequencies in the S(1) state and Franck-Condon simulations were performed to confirm the structure of the phenol-Ar(2) cluster. These were found to be in excellent agreement with the (1mid R:1) configuration.

Section: Introductionmentioning

confidence: 65%

The structure of phenol-Arn (n=1,2) clusters in their S and S1 states

Kalkman¹,

Brand²,

Vu³

et al. 2009

“…Intermolecular bonding for PhOH-Ar is in agreement with high level quantum chemical calculations. 19,43,44 Very recently, hole-burning spectra of PhOH-Ar and PhOH -Ar 2 showed that only one isomer is present in a molecular beam expansion. 45 The intermolecular vibrational structure in the cationic D 0 state of PhOH + -Ar obtained in ZEKE and MATI spectra was assigned assuming a -bound structure, and an accurate value for the dissociation energy of -bound PhOH + -Ar was derived as 535± 3 cm −1 .…”

Section: Introductionmentioning

confidence: 99%

IR signature of the photoionization-induced hydrophobic→hydrophilic site switching in phenol-Arn clusters

Ishiuchi

Sakai

Tsuchida

et al. 2007

139

IR spectra of phenol-Arn (PhOH-Arn) clusters with n=1 and 2 were measured in the neutral and cationic electronic ground states in order to determine the preferential intermolecular ligand binding motifs, hydrogen bonding (hydrophilic interaction) versus pi bonding (hydrophobic interaction). Analysis of the vibrational frequencies of the OH stretching motion, nuOH, observed in nanosecond IR spectra demonstrates that neutral PhOH-Ar and PhOH-Ar2 as well as cationic PhOH+-Ar have a pi-bound structure, in which the Ar atoms bind to the aromatic ring. In contrast, the PhOH+-Ar2 cluster cation is concluded to have a H-bound structure, in which one Ar atom is hydrogen-bonded to the OH group. This pi-->H binding site switching induced by ionization was directly monitored in real time by picosecond time-resolved IR spectroscopy. The pi-bound nuOH band is observed just after the ionization and disappears simultaneously with the appearance of the H-bound nuOH band. The analysis of the picosecond IR spectra demonstrates that (i) the pi-->H site switching is an elementary reaction with a time constant of approximately 7 ps, which is roughly independent of the available internal vibrational energy, (ii) the barrier for the isomerization reaction is rather low(<100 cm(-1)), (iii) both the position and the width of the H-bound nuOH band change with the delay time, and the time evolution of these spectral changes can be rationalized by intracluster vibrational energy redistribution occurring after the site switching. The observation of the ionization-induced switch from pi bonding to H bonding in the PhOH+-Ar2 cation corresponds to the first manifestation of an intermolecular isomerization reaction in a charged aggregate.

“…For example, the PW91k kinetic energy functional 11,12 employs the analytical form of the Perdew-Wang ͑PW91͒ exchange functional, 22 and the TW02 functional 14 and the PBE2, PBE3, and PBE4 functionals 9 utilize the form suggested by Becke. 23 These functionals have been shown to successfully describe weakly interacting systems and coordination compounds.…”

Section: Orbital-free Embedded Dftmentioning

confidence: 99%

“…4 This term, which is typically largest for cases in which the subsystem densities are strongly overlapping, 9 is a significant source of error in many e-DFT calculations, and it generally limits the method to applications in which the subsystem densities involve nonbonded or weakly interacting molecular groups. 4,9,10 Although encouraging progress towards the accurate calculation of the nonadditive kinetic energy contribution have been reported, 9,[11][12][13][14][15][16] more work in this direction is needed.…”

Section: Introductionmentioning

confidence: 99%

Exact nonadditive kinetic potentials for embedded density functional theory

Goodpaster

Ananth

Manby

et al. 2010

188

214

We describe an embedded density functional theory ͑DFT͒ protocol in which the nonadditive kinetic energy component of the embedding potential is treated exactly. At each iteration of the Kohn-Sham equations for constrained electron density, the Zhao-Morrison-Parr constrained search method for constructing Kohn-Sham orbitals is combined with the King-Handy expression for the exact kinetic potential. We use this formally exact embedding protocol to calculate ionization energies for a series of three-and four-electron atomic systems, and the results are compared to embedded DFT calculations that utilize the Thomas-Fermi ͑TF͒ and the Thomas-Fermi-von Weisacker approximations to the kinetic energy functional. These calculations illustrate the expected breakdown due to the TF approximation for the nonadditive kinetic potential, with errors of 30%-80% in the calculated ionization energies; by contrast, the exact protocol is found to be accurate and stable. To significantly improve the convergence of the new protocol, we introduce a density-based switching function to map between the exact nonadditive kinetic potential and the TF approximation in the region of the nuclear cusp, and we demonstrate that this approximation has little effect on the accuracy of the calculated ionization energies. Finally, we describe possible extensions of the exact protocol to perform accurate embedded DFT calculations in large systems with strongly overlapping subsystem densities.