Structure, spectroscopy, and dynamics of the phenol-(water)2 cluster at low and high temperatures (original) (raw)
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Aqueous solutions are complex due to hydrogen bonding (HBing). While gas-phase clusters could provide clues on the solution behavior, most neutral clusters were studied at cryogenic temperatures. Recent results of Shimamori and Fujii provide the first IR spectrum of warm phenol-(H 2 O) 2 clusters. To understand the temperature (T) effect, we have revisited the structure and spectroscopy of phenol-(H 2 O) 2 at all T. While older quantum chemistry work concluded that the cyclic isomers are the most stable, the inclusion of dispersion interactions reveals that they are nearly isoenergetic with isomers forming π-HBs with the phenyl ring. Whereas the OH-stretch bands were previously assigned to purely local modes, we show that at low T they involve a concerted component. We have calculated the (static) anharmonic IR spectra for all low-lying isomers, showing that at the MP2 level, one can single out one isomer (udu) as accounting for the low-T spectrum to 3 cm 1 accuracy. Yet no isomer can explain the substantial blueshift of the phenyl-OH band at elevated temperatures. We describe the temperature effect using ab initio molecular dynamics with a density functional and basis-set (B3LYP-D3/aug-cc-pVTZ) that provide a realistic description of OH· · · O vs. OH· · · π HBing. From the dipole moment autocorrelation function, we obtain good description for both low-and high-T spectra. Trajectory visualization suggests that the ring structure remains mostly intact even at high T, with intermittent switching between OH· · · O and OH· · · π HBing and lengthening of all 3 HBs. The phenyl-OH blueshift is thus attributed to strengthening of its OH bond. A model for three beads on a ring suggests that this shift is partly offset by the elimination of coupling to the other OH bonds in the ring, whereas for the two water molecules these two effects nearly cancel. Published by AIP Publishing. https://doi.org/10.1063/1.5006055
High resolution UV spectroscopy of phenol and the hydrogen bonded phenol-water cluster
The Journal of Chemical Physics, 1996
The S 1 ←S 0 0 0 0 transitions of phenol and the hydrogen bonded phenol͑H 2 O͒ 1 cluster have been studied by high resolution fluorescence excitation spectroscopy. All lines in the monomer spectrum are split by 56Ϯ4 MHz due to the internal rotation of the ϪOH group about the a axis. The barrier for this internal motion is determined in the ground and excited states; V 2 Љ ϭ 1215 cm Ϫ1 , and V 2 Јϭ4710 cm Ϫ1 . The rotational constants for the monomer in the ground state are in agreement with those reported in microwave studies. The excited state rotational constants were found to be AЈϭ5313.7 MHz, BЈϭ2620.5 MHz, and CЈϭ1756.08 MHz. The region of the redshifted 0 0 0 transition of phenol͑H 2 O͒ 1 shows two distinct bands which are 0.85 cm Ϫ1 apart. Their splitting arises from a torsional motion which interchanges the two equivalent H atoms in the H 2 O moiety of the cluster. This assignment was confirmed by spin statistical considerations. Both bands could be fit to rigid rotor Hamiltonians. Due to the interaction between the overall rotation of the entire cluster and the internal rotation, both bands have different rotational constants. They show that V 2 Ј Ͻ V 2 Љ , and that the internal rotation axis is nearly parallel to the a-axis of the cluster. If it is assumed that the structure of the rotor part does not change upon electronic excitation, the internal motion becomes simply a rotation of the water molecule around its symmetry axis. Assuming this motion, barriers of 180 and 130 cm Ϫ1 could be estimated for the S 0 and S 1 states, respectively. The analysis of the rotational constants of the cluster yielded an O-O distance of the hydrogen bond of 2.93 Å in the ground state and 2.89 Å in the electronically excited state. In the equilibrium structure of the cluster, the plane containing phenol bisects the plane of the water molecule.
Chemical Physics, 1998
Ž. Phenol H O clusters have been studied in the electronic ground state by dispersed fluorescence spectroscopy and in the 2 n Ž. electronically excited state by means of two-color resonant two-photon ionization R2PI , spectral hole burning and rotationally resolved laser-induced fluorescence. Resonant spectra up to a cluster size of n s 12 have been obtained by two-color R2PI under 'soft' ionization conditions. The analysis of spectral shifts and of the intermolecular vibrations in both Ž. electronic states is used to assign structures for these bi-, tri-and partially tetracoordinated hydrogen bonded systems, which may be comparable to H-bond-deficient water structures at the surface of liquid water and ice.
Journal of Physical Chemistry A, 2000
Three rotational isomers of 3-methoxyphenol‚water have been identified using resonance-enhanced multiphoton ionization (REMPI) and hole-burning and zero electron kinetic energy (ZEKE) photoelectron spectroscopies with the aid of ab initio and density functional theory calculations. The S 1 band origins of the isomers were measured as 35 822, 35 834, and 36 019 (1 cm-1 and the adiabatic ionization energies as 61 049, 61 801, and 62 120 (5 cm-1 for isomers IV, I, and III, respectively. The frequencies of the intermolecular vibrations and the S 1 0 0 and ionization energy red shifts reveal that the water molecule hydrogen bonds more weakly to 3-methoxyphenol than to phenol. We discuss the spectral characteristics of the rotational isomers by considering the perturbation of the 3-methoxyphenol‚H 2 O intermolecular hydrogen bond by the-OCH 3 group.
Phenol O-H bond dissociation energy in water clusters
We are reporting ab initio and density functional theory (DFT) calculations for the phenol O-H bond dissociation energy in the gas phase and in phenol-water clusters. We have tested a series of recently proposed functionals and verified that DFT systematically underestimates the O-H bond dissociation energy of phenol. However, O-H bond dissociation energies in water clusters are in reasonable agreement with experimental data for phenol in solution. We. have evaluated electronic difference densities in phenol-water, phenoxy-water, and water, and we are suggesting that the representation of this quantity gives an interesting picture of the electronic density rearrangement induced by hydrogen bond interactions in phenol-water clusters.
Molecular Dynamics Studies on Phenol-Water Clusters
2004
Architectures of the molecules and their behavior in the clustered system are important for various consequence functions in the realistic environment. In order to gain detailed knowledge of the phenol–water clusters, 1–nano second (ns) the molecular dynamic (MD) simulation has been performed. The various structural parameters have been obtained from the MD trajectories. MD simulation reveals the presence of well–defined hydrogen–bonded network of water molecules around the phenol molecule and their dynamics. The existence of cooperativity in the hydrogen bonding and high dynamics nature of hydrogen–bonded network are evident from the present study. The calculated mutual diffusion coefficient is in close agreement with the experimental value of the phenol–water system.
Computational Chemistry
It is experimentally well established that the phenolic systems such as phenol and diphenols undergo strong hydrogen bonding interaction with water molecule. But, the possible mode hydrogen bonding in phenol-water systems may be of different types. Although, the experimental methods are not always well enough to give the proper hydrogen bonding conformations in the phenol-water complexes. The hydrogen bonding ability in phenol-water systems can directly be influenced by changing the interacting sites in the given molecular systems, which could be investigated by theoretical studies. Generally, in phenol-water system, the hydrogen bonding is taking place through −OH group of phenol with water molecule, and this kind of interactions between phenol-water and diphenol-water complexes have been extensively investigated in electronic ground state by Quantum Mechanical MP4 calculations. It is also very important to study the stability of different phenol-water complexes and to find out the proper phenol-water complexes with minimized interaction energy. This study will also be helpful for understanding the effect of hydrogen bonding interaction in a better way on other aromatic systems.
Computational Study of Hydrogen Bonding in Substituted Phenol-Acetonitrile-Water Clusters
Journal of the Chinese Chemical Society, 2008
The calculations for a water-acetonitrile-substituted phenols system and the comparison with the experimental parameters will be given. Here we study change in the nature of the interactions into the system with donor and acceptor electron substituents on the phenolic ring, the structures, relative energies and harmonic frequencies. The conformers showed a significant difference in the OH and CN band shift depending on the type of the hydrogen bond formed and the position of the substituent on the phenolic ring. The cyclical hydrogen bonds between water-acetonitrile and substituted phenol OH are important evidence of the relative stability in the system under study.
Computational Study of Hydrogen Bonding in Phenol-acetonitrile-water Clusters
Bulletin- Korean Chemical Society
Calculations are presented for phenol − acetonitrile -(water) n (n = 1-3) clusters. We examine the nature of interactions in the mixed clusters by calculating and comparing the structures, relative energies and harmonic frequencies of isomers with different type of hydrogen bonding. The conformers exhibit quite different patterns in the shifts of the CN and OH stretching frequencies, depending on the type of hydrogen bonding. Cyclic hydrogen bonding among the water molecule(s), acetonitrile and phenolic OH proves very important in determining the relative stability. It is also shown that acetonitrile tends to bind to the OH group of phenol in low energy conformers.