Lewis Acid−Base Interactions in Weakly Bound Formaldehyde Complexes with CO₂, HCN, and FCN:  Considerations on the Cooperative H-Bonding Effects

Abstract

Ab initio quantum chemistry calculations reveal that HCN and mainly FCN can form Lewis acid-base complexes with formaldehyde associated with cooperative H bonds, as first noticed by Wallen et al. (Blatchford, M. A.; Raveendran, P.; Wallen, S. L. J. Am. Chem. Soc. 2002, 124, 14818-14819) for CO2-philic materials under supercritical conditions. The present results, obtained with MP2(Full)/aug-cc-pVDZ calculations, show that the degeneracy of the nu(2) mode in free HCN or FCN is removed upon complexation in the same fashion as that of CO2. The splitting of these bands along with the electron structure analysis provides substantial evidence of the interaction of electron lone pairs of the carbonyl oxygen with the electron-deficient carbon atom of the cyanides. Also, this work investigates the role of H bonds acting as additional stabilizing interactions in the complexes by performing the energetic and geometric characterization.

Theoretical insights on electron donor–acceptor interactions involving carbon dioxide

“…Theoretical studies on model systems have been carried out to analyze the interactions of CO 2 with carbonyl compounds. [13][14][15][16][17][18][19][20][21][22][23][24][25] Former studies did confirm the existence of EDA complexes in which, as expected from simple chemical considerations, CO 2 play the role of the electron acceptor (i.e., it behaves as a Lewis acid). Recent work, however, has revealed the existence of other unconventional EDA structures.…”

Quantifying cooperative intermolecular interactions for improved carbon dioxide capture materials

“…The use of supercritical CO 2 as a "green solvent" for industrial processes has resulted in a number of recent experimental [17][18][19][20][21] and theoretical [18][19][20][21][22][23][24] investigations concerning the fundamental intermolecular interactions of CO 2 . For molecules containing carbonyl functional groups, CO 2 demonstrates simultaneous Lewis acid-Lewis base R 2 C=O· · ·CO 2 and hydrogen bonding interactions CH· · ·O=C=O.…”

“…For molecules containing carbonyl functional groups, CO 2 demonstrates simultaneous Lewis acid-Lewis base R 2 C=O· · ·CO 2 and hydrogen bonding interactions CH· · ·O=C=O. 17,20,21,24 These two simultaneous intermolecular interactions work cooperatively to strengthen the total interaction. 17 Similar cooperative intermolecular interactions have also been observed for CO 2 complexes with dimethyl ether and 1,2,dimethoxyethane [(CH 3 ) 2 O· · ·CO 2 and CH· · ·O=C=O], 19, 21 small fluorinated alkanes (RF· · ·CO 2 and CH· · ·O=C=O), 22 and various nitrogen containing Lewis bases (N· · ·CO 2 and CH· · ·O=C=O).…”

Surface‐enhanced Raman scattering properties of Lewis acid–base complexes ofp‐hydroxybenzoic andp‐mercaptobenzoic acids with CO2in the presence of silver

“…Hence, by comparing SERS spectra, obtained under normal and scCO 2 conditions, possible effects from the intermolecular interactions could be further understood. In the case of PHBA and PMBA, the presence of an available carboxylic group would be sufficient to interact with a CO 2 molecule, giving rise to the so‐called Lewis acid–base (LA–LB) interactions . In this sense, we propose that SERS/scCO 2 spectroscopy can be also employed to rationalize LA–LB complexations involving noble metals.…”