The effect of cooperative hydrogen bonding on the OH stretching-band shift for water clusters studied by matrix-isolation infrared spectroscopy and density functional theory

Abstract

Infrared spectra of the water clusters have been measured in the N2 + O2 matrix. The aggregation process of water in the matrix has been monitored by annealing the deposited samples up to 40 K and UV irradiation. The monomer, dimer, cyclic trimer and cyclic pentamer are found as water clusters in the matrix. For the hexamer, several structures such as chair, cage, prism, bag 1 and/or book 1 are likely to exist. By UV irradiation, the cyclic pentamer is predominantly formed from the monomer and dimer. On the other hand, by annealing the deposited sample, several hexamers are formed. The theoretical calculation for water clusters has revealed that the formation of one hydrogen bonding in a hydrogen-bonded chain cooperatively enhances or diminishes the strength of another hydrogen bond. Both proton donor (D) and acceptor (A) participating in a hydrogen-bonding pair DA are capable of forming hydrogen bonding with the other water molecules; D can additionally accept two protons and donate one proton, and A can additionally donate two protons and accept one proton. We have proposed the classification of hydrogen-bonding patterns considering the cooperativity, denoting as d'a'DAd''a'', where d and a are integers indicating the number of proton donors and acceptors to D (the single prime) and A (the double prime), respectively. Then, a magnitude given by MOH = -d' + a' + d'' - a'' has been introduced, which is very useful for connecting the hydrogen-bonding patterns to their OH wavenumbers. As a result, it is revealed that the OH stretching bands of water clusters are characterized by eight indicators (free and MOH = -2, -1, 0, 1, 2, 3 and 4). The classification proposed here is applicable to the OH band analysis for the hydrogen-bonded water and alcohols in a condensed phase.

Two-dimensional infrared spectroscopy of isotope-diluted ice Ih

“…The spectral narrowing reflects the much smaller variability of local structural motives around the OH or OD chromophore in the crystalline phase, despite the existence of proton disorder. Furthermore, the shift to lower frequencies indicates an average stronger hydrogen bonding environment, 57 which occurs already by cooling liquid water to lower temperatures. 36 In contrary, the librationbend combination mode of the H 2 O [ Fig.…”

Substrate-induced cooperative effects in water adsorption from density functional calculations

“…The calculated energy range of the stretching of O-H bonds for the free-standing dimer ͑3500-3800 cm −1 ͒ is in good agreement with that found in the experiments. 21,46 As expected, the stretching mode of the donating O-H covalent bond ͑between atoms 2 and 3 in Fig. 4͒ has the lowest frequency, reflecting the weakening of this FIG.…”

“…This shows that, in addition to the binding with the metal, the fact that the molecule forms more than one H bond also tends to increase the stability of the whole H-bonded network as already observed for free-standing water clusters. 21,24 An interesting point to consider is that the weakening of the covalent O-H bonds for the adsorbed water dimer and other buckled structures on the oxidized Ru substrate, associated with the formation of strong H bonds, may have consequences for the chemistry of water. For example, a reduction in the energy barriers for partial dissociation can be expected in some of these structures.…”

“…17 Cooperative effects are also quite strong in small water clusters. 11,[18][19][20][21][22][23][24] The key ingredient to understand these cooperative effects is the polarization induced in each water molecule by the presence of their neighbors. This polarization has its major effect on the lone pairs of the oxygen atoms, which are the electrons involved in the formation of hydrogen bonds.…”

Simulating Energy Relaxation in Pump–Probe Vibrational Spectroscopy of Hydrogen-Bonded Liquids

“…The corresponding molecular transitions probed during the excitation and relaxation processes involve excited states, where the stretching mode is coupled with lower frequency modes via hydrogen bonding, causing spectral diffusion and nontrivial changes in spectral line shapes and width. [7][8][9][10] Furthermore, polarized infrared spectroscopy makes it possible to study the rotational dynamics of such molecules. [11][12][13] To obtain the underlying molecular-level details of pump probe experiments, vibrational relaxation dynamics has been extensively investigated in computer simulations and several approaches have been proposed.…”