Showing papers by "Sanjay Wategaonkar published in 2013"
TL;DR: Experimental evidence using VUV ionization-detected IR-predissociation spectroscopy (VUV-ID-IRPDS) for this weak hydrogen-bonding interaction in the H2 S dimer is presented and it is shown that the heteromolecular H 2 S-MeOH complex, for which both S−H⋅ⓂⓉⓁO and O−H ⓁⓊⓋⓓ
Abstract: The nature of the S−H⋅⋅⋅S hydrogen-bonding interaction in the H2 S dimer and its structure has been the focus of several theoretical studies. This is partly due to its structural similarity and close relationship with the well-studied water dimer and partly because it represents the simplest prototypical example of hydrogen bonding involving a sulfur atom. Although there is some IR data on the H2 S dimer and higher homomers from cold matrix experiments, there are no IR spectroscopic reports on S−H⋅⋅⋅S hydrogen bonding in the gas phase to-date. We present experimental evidence using VUV ionization-detected IR-predissociation spectroscopy (VUV-ID-IRPDS) for this weak hydrogen-bonding interaction in the H2 S dimer. The proton-donating S−H bond is found to be red-shifted by 31 cm(-1) . We were also able to observe and assign the symmetric (ν1 ) stretch of the acceptor and an unresolved feature owing to the free S−H of the donor and the antisymmetric (ν3 ) SH stretch of the acceptor. In addition we show that the heteromolecular H2 S-MeOH complex, for which both S−H⋅⋅⋅O and O−H⋅⋅⋅S interactions are possible, is S-H⋅⋅⋅O bound.
54 citations
TL;DR: The energy decomposition analysis showed that the dissociation energies and the red shifts in the O-H stretching frequencies follow a unified correlation if these two parameters were correlated with the sum of the charge transfer and the exchange component of the total binding energy.
Abstract: Hydrogen bonding interaction between the ROH hydrogen bond donor and sulfur atom as an acceptor has not been as well characterized as the O–H···O interaction. The strength of O–H···O interactions for a given donor has been well documented to scale linearly with the proton affinity (PA) of the H-bond acceptor. In this regard, O–H···O interactions conform to the acid–base formalism. The importance of such correlation is to be able to estimate molecular property of the complex from the known thermodynamic data of its constituents. In this work, we investigate the properties of O–H···S interaction in the complexes of the H-bond donor and sulfur containing acceptors of varying proton affinity. The hydrogen bonded complexes of p-Fluorophenol (FP) with four different sulfur containing acceptors and their oxygen analogues, namely H2O/H2S, MeOH/MeSH, Me2O/Me2S and tetrahydrofuran (THF)/tetrahydrothiophene (THT) were characterized in regard to its S1–S0 excitation spectra and the IR spectra. Two-color resonantly en...
43 citations
TL;DR: Spectroscopic investigations of hydrogen bonded complexes of CHF3 and CHCl3 with p-cresol and p-cyanophenol found that in the case of p- cresol the complexes were C-H···π bound in which the C- H stretch was blue-shifted.
Abstract: In this work, we present spectroscopic investigations of hydrogen bonded complexes of CHF3 and CHCl3 with p-cresol and p-cyanophenol. The systems were chosen as the potential candidates bound by C–H···Y type hydrogen bonds that are known to exhibit unconventional blue shifts in the C–H stretching frequency. The two phenol derivatives chosen offer multiple hydrogen bonding acceptor sites. They also differ from each other in regard to the electron-donating/withdrawing ability of the para substituents which could dictate the global minimum structure in each case. The complexes were formed using the supersonic jet expansion method and were investigated using a variant of the IR-UV double resonance technique, namely fluorescence depletion IR (FDIR) spectroscopy. It was found that in the case of p-cresol the complexes were C–H···π bound in which the C–H stretch was blue-shifted. In the case of p-cyanophenol the complexes were C–H···N bound. In its fluoroform complex the C–H frequency was blue-shifted by 27 cm–1...
30 citations
TL;DR: The present study combines both laser spectroscopy and ab initio calculations to investigate the intermolecular hydrogen bonding of complexes of the tyrosine side chain model chromophore compounds phenol (PH) and para-cresol with H2 O, MeOH, PH and pCR in the ground (S0 ) state as well as in the electronic excited (S1 ) state.
Abstract: The present study combines both laser spectroscopy and ab initio calculations to investigate the intermolecular OH···O hy- drogen bonding of complexes of the tyrosine side chain model chromophore compounds phenol (PH) and para-cresol (pCR) with H2O, MeOH, PH and pCR in the ground (S0) state as well as in the electronic excited (S1) state. All the experimental and computational findings suggest that the H-bond strength increases in the S1 state and irrespective of the hydrogen bond acceptor used, the dispersion energy contribution to the total interaction energy is about 10-15 % higher in the S1 state com- pared to that in the S0 state. The alkyl-substituted (methyl; + I effect) H-bond acceptor forms a significantly stronger H bond both in the S0 and the S1 state compared to H2O, whereas the aryl-substituted (phenyl; � R effect) H-bond donor shows a minute change in energy compared to H2O. The theoretical study emphasizes the significant role of the dispersive interac- tions in the case of the pCR and PH dimers, in particular the CH···O and the CH···p interactions between the donor and acceptor subunits in controlling the structure and the energet- ics of the aromatic dimers. The aromatic dimers do not follow the acid-base formalism, which states that the stronger the base, the more red-shifted is the XH stretching frequency, and consequently the stronger is the H-bond strength. This is due to the significant contribution of the dispersion interaction to the total binding energy of these compounds.
8 citations