Infrared characterization of the HCOOH···CO2 complexes in solid argon: stabilization of the higher-energy conformer of formic acid.

The complexes of formic acid (HCOOH, FA) with carbon dioxide are studied by infrared spectroscopy in an argon matrix. Two trans-FA···CO(2) and one cis-FA···CO(2) complexes are experimentally identified while the calculations at the MP2(full)/6-311++G(2d,2p) level of theory predict one more minimum for the cis-FA···CO(2) complex. The complex of the higher-energy conformer cis-FA with CO(2) is prepared by vibrational excitation of the ground-state trans-FA conformer combined with thermal annealing.

Dimers of the higher-energy conformer of formic acid: experimental observation.

We report on the first experimental observation of formic acid dimers composed of two molecules of the higher-energy cis conformer. The cis-cis formic acid dimers are prepared in an argon matrix by selective vibrational excitation of the ground state trans conformer (deuterated form HCOOD) combined with thermal annealing of the matrix at about 30 K. Five cis-cis formic acid dimers are predicted by ab initio calculations (interaction energies from -16.

Conformation resolved induced infrared activity: trans- and cis-formic acid isolated in solid molecular hydrogen.

We report combined experimental and theoretical studies of infrared absorptions induced in solid molecular hydrogen by different conformers of formic acid (HCOOH, FA). FTIR spectra recorded in the H(2) fundamental region (4120-4160 cm(-1)) reveal a number of relatively strong trans-FA induced Q-branch absorptions that are assigned by studying both FA-doped parahydrogen (pH(2)) and normal hydrogen (nH(2)) samples. The induced H(2) absorptions are also studied for HCOOD doped nH(2) crystals for both the trans and cis conformers that show resolvable differences.

Experimental and computational study of crystalline formic acid composed of the higher-energy conformer.

Crystalline formic acid (FA) is studied experimentally and by first-principles simulations in order to identify a bulk solid structure composed of the higher-energy (cis) conformer. In the experiments, deuterated FA (HCOOD) was deposited in a Ne matrix and transformed to the cis conformer by vibrational excitation of the ground state (trans) form. Evaporation of the Ne host above 13 K prepared FA in a bulk solid state mainly composed of cis-FA.

Interaction of formic acid with nitrogen: stabilization of the higher-energy conformer.

Conformational change is an important concept in chemistry and physics. In the present work, we study conformations of formic acid (HCOOH, FA) and report the preparation and identification of the complex of the higher-energy conformer cis-FA with N(2) in an argon matrix. The cis-FA···N(2) complex was synthesized by combining annealing and vibrational excitation of the ground-state trans-FA in a FA/N(2)/Ar matrix.

Matrix isolation and ab initio study of trans-trans and trans-cis dimers of formic acid.

Six trans-trans and five trans-cis dimeric structures of formic acid (HCOOH) are revealed by ab initio calculations. Four trans-trans and two trans-cis dimers are identified in the IR absorption spectra in argon matrices. The trans-cis dimers are obtained by narrow-band IR excitation of the vibrational transitions of the trans-trans dimers.

Conformation-dependent chemical reaction of formic acid with an oxygen atom.

Conformation dictates many physical and chemical properties of molecules. The importance of conformation in the selectivity and function of biologically active molecules is widely accepted. However, clear examples of conformation-dependent bimolecular chemical reactions are lacking.

Spectroscopic study of cis-to-trans tunneling reaction of HCOOD in rare gas matrices.

The higher energy conformer (cis) of HCOOD is prepared by vibrational excitation of the trans form. The cis conformer decays back to the conformational ground state (trans) via tunneling of deuterium. The tunneling process in HCOOD in rare gas matrices is extremely slow (in scale of weeks).

High-energy conformer of formic acid in solid hydrogen: conformational change promoted by host excitation.

Conformers of formic acid (FA) are studied by IR spectroscopy in solid hydrogen. The higher-energy cis-FA conformer is prepared by vibrational excitation of the ground-state trans-FA conformer. The quantum yield of the trans to cis conformational process in solid hydrogen appears about two orders of magnitude smaller than in solid argon, which is explained by efficient coupling of the vibrationally excited trans form with the host vibrations deactivating the conformational change.

Photochemical synthesis of H2O2 from the H2O...O(3P) van der Waals complex: experimental observations in solid krypton and theoretical modeling.

Productive photochemical synthesis of hydrogen peroxide, H(2)O(2), from the H(2)O...

High-energy conformer of formic acid in solid neon: giant difference between the proton tunneling rates of cis monomer and trans-cis dimer.

We study the conformational reorganization of formic acid (FA) in solid neon and report the higher-energy cis-FA monomer and one form of the trans-cis FA dimers. They were prepared by selective vibrational excitation of the trans-FA monomer and trans-trans dimer. The proton tunneling decay of cis-FA monomer is surprisingly very fast in solid neon, two orders of magnitude faster than in solid argon.

Hydrogen bonding between formic acid and water: complete stabilization of the intrinsically unstable conformer.

We studied hydrogen bonding between formic acid (FA) and water in solid argon and identified the first water complex with the higher-energy conformer cis-FA. In sharp contrast to cis-FA monomer, cis-FA interacting with water is very stable at low temperatures, which was explained by strong O-H..

cis-trans formic acid dimer: experimental observation and improved stability against proton tunneling.

We prepared the first cis-trans dimer of formic acid and measured its vibrational spectrum in a low-temperature Ar matrix. This preparation was done by selective vibrational excitation of the trans-trans noncyclic dimer. It was found that the stability of the cis-trans dimer against proton tunneling is strongly improved compared to the monomer, especially at elevated temperatures (>30 K).