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Computational study of hydrogen-bonded complexes of HOCO with acids: HOCO⋯HCOOH, HOCO⋯H2SO4, and HOCO⋯H2CO3
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10.1063/1.4742817
/content/aip/journal/jcp/137/6/10.1063/1.4742817
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/6/10.1063/1.4742817

Figures

Image of FIG. 1.
FIG. 1.

Optimized structures of H-bonded HOCO⋯HCOOH, HOCO⋯H2SO4, and HOCO⋯H2CO3 complexes predicted at the B3LYP/6-311++G(2d,2p) level of theory. Hydrogen bonds are indicated by dotted lines. Here, cH: cis-HOCO; tH: trans-HOCO; FA: formic acid; SA: sulfuric acid; CA: carbonic acid.

Image of FIG. 2.
FIG. 2.

Zero-point-corrected relative energy diagram for the inter-conversion of trans-HOCO (tH) to cis-HOCO (cH) within the 1:1 H-bonded complex involving formic acid (FA). The calculations have been performed at the B3LYP/6-31+G(d,p) level of theory. Visualizations of optimized TS1, TS2, and non-planar tH⋯FA geometries are also given.

Image of FIG. 3.
FIG. 3.

The B3LYP/6-311++G(2d,2p) level of theory computed infrared spectra in the OH stretching region of the HOCO⋯HCOOH complexes including both cis- and trans-HOCO isomers. For comparison with the monomers, the computed spectra of isolated cis-HOCO (cH), trans-HOCO (tH), and formic acid (FA) are also included. Frequencies and intensities of the OH vibrations in the H-bonded complexes and monomers, computed using the harmonic approximation, are listed in Table III.

Image of FIG. 4.
FIG. 4.

The B3LYP/6-311++G(2d,2p) level of theory computed infrared spectra in the OH stretching region of the HOCO⋯H2SO4 complexes including both cis- and trans-HOCO isomers. For comparison with the monomers, the computed spectra of isolated cis-HOCO (cH), trans-HOCO (tH), and sulphuric acid (SA) are also included. Frequencies and intensities of the OH vibrations in the H-bonded complexes and monomers, computed using the harmonic approximation, are listed in Table III.

Image of FIG. 5.
FIG. 5.

The B3LYP/6-311++G(2d,2p) level of theory computed infrared spectra in the OH stretching region of the HOCO⋯H2CO3 complexes including both cis- and trans-HOCO isomers. For comparison with the monomers, the computed spectra of isolated cis-HOCO (cH), trans-HOCO (tH), and carbonic acid (CA) are also included. Frequencies and intensities of the OH vibrations in the H-bonded complexes and monomers, computed using the harmonic approximation, are listed in Table III.

Image of FIG. 6.
FIG. 6.

Visualization of the OH stretching normal modes, with their harmonic frequency and descriptions, for the various HOCO complexes predicted at the B3LYP/6-311++G(2d,2p) level of theory. Intensities and identification of the moiety within the complex that is mostly involved in each vibration is given in Table III and the corresponding H-atom displacements indicated by the length of the arrows. [IP: In-Phase; OOP: Out-of-Phase.]

Image of FIG. 7.
FIG. 7.

A plot of the net intensity enhancement for the OH stretching vibrations upon H-bond formation in the HOCO⋯acid complex versus the zero-point-corrected binding energies of the complex computed at the B3LYP/6-311++G(2d,2p) level of theory. The net intensity enhancement has been obtained by summing the total OH intensities associated with both the free and H-bonded OH vibrations in the complex, and subtracting from this the total intensities of the free OH groups in the monomer units forming the complex. As an example, in case of the cis-HOCO⋯H2CO3 (cH⋯CA) complex, its total OH intensity arising from its IP, OOP, and free OH stretching modes is 2552 km/mol since from Table III we have: (114.6 + 1362.5 +1074.9) = 2552. Similarly, the total combined OH intensity of the isolated cH and CA monomers is 230.9 km/mol since from Table III we have: (18.4 + 15.3 + 197.2 = 230.9). Therefore, the resultant net intensity enhancement upon cH⋯CA complex formation is estimated to be 2321.1 km/mol (2552.0 − 230.9 = 2321.1). The six points plotted correspond to the net OH stretching mode enhancements calculated for the six complexes shown in Fig. 1.

Tables

Generic image for table
Table I.

Binding energies (kcal/mol) of the doubly hydrogen-bonded HOCO⋯Acid complexes predicted at various levels of theory. All energies are corrected for ZPE.

Generic image for table
Table II.

Hydrogen bond distances (Å) for the HOCO⋯Acid complexes.

Generic image for table
Table III.

Harmonic OH stretching vibrations of HOCO⋯Acid complexes and monomer units predicted at the QCISD, (MP2), and [B3LYP] levels of theory with the 6-311++G (2d,2p) basis set. Their frequencies (cm−1), intensities (km/mol), descriptions (in-phase or out-of-phase), and moiety in the complex primarily involved in the vibration are given.

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2012-08-14
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Computational study of hydrogen-bonded complexes of HOCO with acids: HOCO⋯HCOOH, HOCO⋯H2SO4, and HOCO⋯H2CO3
http://aip.metastore.ingenta.com/content/aip/journal/jcp/137/6/10.1063/1.4742817
10.1063/1.4742817
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