Blue- and Red-Shifting Hydrogen Bonding: A Gas Phase FTIR and Ab Initio Study of RR ` CO center dot center dot center dot DCCI3 and RR ` S center dot center dot center dot DCCI3 Complexes

Behera, B and Das, Puspendu K (2018) Blue- and Red-Shifting Hydrogen Bonding: A Gas Phase FTIR and Ab Initio Study of RR ` CO center dot center dot center dot DCCI3 and RR ` S center dot center dot center dot DCCI3 Complexes. In: JOURNAL OF PHYSICAL CHEMISTRY A, 122 (18). pp. 4481-4489.

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Abstract

Blue-shifting H-bonded (C-D...O) complexes between CDCI3 and CH3HCO, (CH3)(2)CO3 and C2H5(CH3)CO, and red-shifting H-bonded (C-D...S) complexes between CDCI3 with (CH3)(2)S and (C2H5)(2)S have been identified by Fourier transform infrared spectroscopy in the gas phase at room temperature. With increasing partial pressure of the components, a new band appears in the C-D stretching region of the vibrational spectra. The intensity of this band decreases with an increase in temperature at constant pressure, which provides the basis for identification of the H-bonded bands in the spectrum. The C-D stretching frequency of CDCI3 is blue-shifted by +7.1, +4, and +3.2 cm(-1) upon complexation with CH3HCO, (CH3)(2)CO3 and C2H5(CH3)CO, respectively, and red-shifted by -14 and -19.2 cm(-1) upon complexation with (CH3)(2)S and (C2H5)(2)S, respectively. By using quantum chemical calculations at the MP2/6-311++G** level, we predict the geometry, electronic structural parameters, binding energy, and spectral shift of H bonded complexes between CDCI3 and two series of compounds named RCOR' (H2CO, CH3HCO, (CH3)(2)CO3 and C2H5(CH3)CO) and RSR' (H2S, CH3HS, (CH3)(2)S, and (C2H5)(2)S) series. The calculated and observed spectral shifts follow the same trends. With an increase in basicity of the H-bond acceptor, the C-D bond length increases, force constant decreases, and the frequency shifts to the red from the blue. The potential energy scans of the above complexes are done, which show that electrostatic attraction between electropositive D and electron-rich O/S causes bond elongation and red shift, and the electronic and nuclear repulsions lead to bond contraction and blue shifts. The dominance of the two opposing forces at the equilibrium geometry of the complex determines the nature of the shift, which changes both in magnitude and in direction with the basicity of the hydrogen-bond acceptor.

Item Type:	Journal Article
Publication:	JOURNAL OF PHYSICAL CHEMISTRY A
Publisher:	AMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Additional Information:	Copy right for this article belong toAMER CHEMICAL SOC, 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	05 Jun 2018 15:45
Last Modified:	05 Jun 2018 15:45
URI:	http://eprints.iisc.ac.in/id/eprint/59957

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