Theoretical investigation of gas-phase molecular complex formation between 2-hydroxy thiophenol and a water molecule (original) (raw)
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Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 2007
The Raman (3700-100 cm −1 ) and infrared (4000-400 cm −1 ) spectra of solid 2-aminophenol (2AP) have been recorded. The internal rotation of both OH and NH 2 moieties produce ten conformers with either C s or C 1 symmetry. However, the calculated energies as well as the imaginary vibrational frequencies reduce rotational isomerism to five isomers. The molecular geometry has been optimized without any constraints using RHF, MP2 and B3LYP levels of theory at 6-31G(d), 6-311+G(d) and 6-31++G(d,p) basis sets. All calculations predict 1 (cis; OH is directed towards NH 2 ) to be the most stable conformation except RHF/6-31++G(d,p) basis set. The 1 (cis) isomer is found to be more stable than 8 (trans; OH is away from the NH 2 moiety and the NH bonds are out-of-plane) by 1.7 kcal/mol (598 cm −1 ) as obtained from MP2/6-31G(d) calculations. Aided by experimental and theoretical vibrational spectra, cis and trans 2AP are coexist in solution but cis isomer is more likely present in the crystalline state. Aided by MP2 and B3LYP frequency calculations, molecular force fields, simulated vibrational spectra utilizing 6-31G(d) basis set as well as normal coordinate analysis, complete vibrational assignments for HOC 6 H 4 NH 2 and DOC 6 H 4 ND 2 have been proposed. Furthermore, we carried out potential surface scan, to determine the barriers to internal rotations of NH 2 and OH groups. All results are reported herein and compared with similar molecules when appropriate.
Theoretical investigation for the hydrogen bond interaction in THF–water complex
Chemical Physics Letters, 2004
Ab initio and density functional theory (DFT) calculation for the hydrogen bond interaction between tetrahydrofuran (THF) and water is carried out using different basis sets. The role of basis set size, inclusion of diffuse functions, polarization function, electron correlation and hybrid functionals are also investigated. The binding energy for the hydrogen-bonded THF-water complex is found to be 13.65 kcal mol À1 at MP2/6-311+G** level of theory. Moreover, the dipole-dipole interaction between THF and water is also investigated for different basis sets and level of theories.
The Journal of Physical Chemistry, 1994
A theoretical study of the hydrogen peroxidewater (HPW) complex is presented. We analyze the ab initio quantum-mechanical calculations at the HartreeFock (HF), Msller-Plesset (MP2, MP4) levels of theory. Linear, cyclic, and transition estate structures were determined. Correction for the basis set superposition error (BSSE) was taken into account by applying thecounterpoise procedure. The 6-31G** and 6-3 11G(3d,2p) basis sets with and without diffuse functions were employed. A study of the topology of the charge density for the cyclic structures 2 and 3 was performed. Computational Methods Ab initio self-consistent field (SCF) calculations have been carried out with the GAUSSIAN90,3S GAUSSIAN92,36 and SPARTAN3' series of programs on an SGI 4D/320GTXb and Convex 240 computers. Theoretical backgrounds of the methodology are shown elsewhere.38~~~ The 6-31G**40 and 6-31 1G-(3 d , 2~)~l basis sets were used, augmented by diffuse functions. These sets have proved to be useful in describing the hydrogen bond, as Feller42 pointed out in the water dimer study. The notation used throughout this work was described previously39b (Le., MP2/6-31G*//HF/3-21G designates an MP2 calculation with the 6-3 lG* basis set, using a molecular geometry optimized at the H F level with the 3-21G basis set). Correction for the electron correlation was taken into account at the MP2 and MP4-(SDTQ) levels, including all the electrons in the calculation. Full geometry optimization was performed in all the calculations. Symmetry restrictions (C2) were imposed for structures I and 4. Results Ab initio calculations at the H F and M~rller-Plesset (MP) levels predict five stationary points on the PES for the HPW complex, structures: 1-5 (see Figure 1) with different sets. Tables 2 and 3 show the energies of the system studied at the HF and MP2 levels respectively for structures 1-5. The energies for water and hydrogen peroxide monomers at the two basis sets considered
Ab initio calculations on phenol–water
Chemical Physics Letters, 2001
The structures of the three phenol-water minima are optimized with MP2 and the interaction-optimized DZPi basis set. Single point calculations are carried out using the slightly larger ESPB basis set, which contains a set of (s,p) bond functions at the midpoint of the hydrogen-bond. The binding energies and hydrogen-bond distances are corrected for basis set superposition error. For all minima, our binding energies D e are larger than the previous theoretical estimates. Despite this, our best estimate of the binding energy D 0 for the global minimum, 21.08 kJ/mol, is about 2 kJ/mol smaller than the experimental values (23:45 AE 0:48 and 22:92 AE 0:36 kJ/mol). Ó
Journal of Chemical Theory and Computation, 2010
The strengths of noncovalent interactions are generally very sensitive to a number of geometric parameters. Among the most important of these parameters is the separation between the interacting moieties (in the case of an intermolecular interaction, this would be the intermolecular separation). Most works seeking to characterize the properties of intermolecular interactions are mainly concerned with binding energies obtained at the potential energy minimum (as determined at some particular level of theory). In this work, in order to extend our understanding of these types of noncovalent interactions, we investigate the distance dependence of several types of intermolecular interactions, these are hydrogen bonds, stacking interactions, dispersion interactions, and X-H · · · π interactions. There are several methods that have traditionally been used to treat noncovalent interactions as well as many new methods that have emerged within the past three or four years. Here we obtain reference data using estimated CCSD(T) values at the complete basis set limit (using the CBS(T) method); potential energy curves are also produced using several other methods thought to be accurate for intermolecular interactions, these are MP2/cc-pVTZ, MP2/aug-cc-pVDZ, MP2/6-31G*(0.25), SCS(MI)-MP2/cc-pVTZ, estimated MP2.5/CBS, DFT-SAPT/ aug-cc-pVTZ, DFT/M06-2X/6-311+G(2df,2p), and DFT-D/TPSS/6-311++G(3df,3pd). The basis set superposition error is systematically considered throughout the study. It is found that the MP2.5 and DFT-SAPT methods, which are both quite computationally intensive, produce potential energy curves that are in very good agreement to those of the reference method. Among the MP2 techniques, which can be said to be of medium computational expense, the best results are obtained with MP2/cc-pVTZ and SCS(MI)-MP2/cc-pVTZ. DFT-D/TPSS/6-311++G(3df,3pd) is the DFT-based method that can be said to give the most well-balanced description of intermolecular interactions.
Journal of Chemical Sciences, 2014
The intramolecular hydrogen bonding (IHB) in a series of 3-, 4-and 5-substituted 2hydroxybenzophenone (HBP) is studied using density functional theory calculations. All calculations are performed at the B3LYP level, using 6-311++G** basis set. To understand the substitution effects on the nature of IHB and the electronic structure of the chelated ring system, the vibrational frequencies, 1 H chemical shift, topological parameters, natural bond orders and natural charges over atoms involved in the chelated ring of HBP and its derivatives were calculated. The Wiberg bond indices and the natural charges over atoms involved in the chelated ring have been computed using the natural bond orbital (NBO) analysis. The computations were further complemented with an atoms-in-molecules (AIM) topological analysis to characterize the nature of the IHB in the considered molecules. Several correlations between geometrical parameters, 1 H NMR chemical shift and topological parameters with the IHB strength are obtained.
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.
High-Level ab Initio Calculations on the Intramolecular Hydrogen Bond in Thiomalonaldehyde
Journal of Physical Chemistry A, 1997
High-level ab initio calculations, in the framework of the G2(MP2) theory, have been carried out on the different tautomers of thiomalonaldehyde (TMA). These calculations are compared with those obtained using density functional theory methods, namely B3LYP, with extended basis sets. In general the enethiol tautomers of TMA are 5-10 kcal/mol more stable than the corresponding enol analogues, with the only exception being the Z-enol (E1) and the Z-enethiol (T1) hydrogen-bonded species, which are the global minima of both series. At the G2(MP2) level both tautomers are nearly degenerate, the enethiol T1 being 0.2 kcal/mol more stable than the enol E1. Electron correlation effects stabilize preferentially the enol form, while the ZPE corrections go in the opposite direction, due essentially to the differences between S-H and O-H stretching frequencies. As a consequence, when the hydrogen atom involved in the intramolecular hydrogen bond (IHB) of both tautomers is replaced by deuterium, the stability order is reversed and E1 is predicted to be more stable than T1. An analysis of these IHBs in terms of the topological characteristics of the electron charge density and of the shifts of the S-H and O-H vibrational frequencies reveals that the HB in E1 is much stronger than in T1. The existence of this IHB results in an increase of the electron delocalization which enhances the stability of tautomer E1. At the G2(MP2) level two open-chain rotamers, namely T4 and T7, are predicted to be within an energy gap smaller than 0.5 kcal/mol with respect to the global minimum. The use of continuum and discrete-continuum models indicates that both open-chain enethiols and enols are significantly stabilized by solute-solvent interactions, and they should predominate in aqueous solution. B3LYP/6-311+G(3df,2p) relative stabilities are in excellent agreement with G2(MP2) values.
Journal of Molecular Structure: THEOCHEM, 1999
Structures, dimerization energies, and vibrational spectra of two isomeric water-methanol dimers were computed with a high level of ab initio and DFT methods. The computed dimerization energies are very similar (ϳ 4 kcal mol Ϫ1), with slight energy preference for the HOH … O(H)CH 3 dimer over the CH 3 OH … OH 2 dimer. The fitting of the computed IR spectra for both isomers to the experimentally observed frequencies was used to unequivocally prove the existence of the HOH … O(H)CH 3 dimer in the gas phase.