Probing the Partial Activation of Water by Open-Shell Interactions, Cl(H₂O)_1–4

Abstract

The partial chemical activation of water by reactive radicals was examined computationally for small clusters of chlorine and water, Cl • (H 2 O) n=1−4 . Using an automated isomer-search procedure, dozens of unique, stable structures were computed. Among the resulting structural classes were intact, hydrated-chlorine isomers, as well as hydrogen-abstracted (HCl)(OH)(H 2 O) n−1 configurations. The latter showed increased stability as the degree of hydration increased, until n = 4, where a new class of structures was discovered with a chloride ion bound to an oxidized water network. The electronic structure of these three structural classes was investigated, and spectral signatures of this hydration-based evolution were connected to these electronic properties. An ancillary outcome of this detailed computational analysis, including coupled-cluster benchmarks, was the calibration of cost-effective quantum chemistry methods for future studies of these radical−water complexes.

Electronic Structure and Vibrational Signatures of the Delocalized Radical in Hydrated Clusters of Copper(“II”) Hydroxide CuOH+(H2O)0–2

“…This hemibonding-type configuration is surprisingly similar to configurations oberved in recently studied hydrated halogen-atom complexes. 60,61 Even with the correlation-related caveats discussed above, however, such an analysis yields a bit of a conundrum. These hemibonding interactions would be expected to be quite weak.…”

Stepwise Activation of Water by Open-Shell Interactions, Cl(H2O)n=4–8,17

“…Before proceeding to larger clusters, some aspects of the bonding at n = 4 that were not investigated in ref are first presented here. Shown in Figure are occupied molecular orbitals and their energy eigenvalues for isomers of each structural class ( 4A , 4D , and 4G ).…”

“…The isomer energies discussed in this section and those that follow have been computed with CCSD/aug-cc-pVDZ single points on BHHLYP/aug-cc-pVDZ structures. The previous analysis of smaller clusters demonstrated that the BHHLYP density functional performed particularly well for chlorine–water systems and often found conformers that other functionals neglected. The well-known problems of many density functionals when describing charge-transfer behavior nonetheless kept a healthy helping of skepticism simmering in the background of this investigation.…”

“…One of the ancillary aims of the previous study of smaller cluster sizes ( n = 1–4) was an assessment of the computational methodologies required to quantitatively describe this ion–radical interaction correctly. Equation-of-motion coupled-cluster methods − [up to EOM-IP-CC­(2,3)] were used to benchmark the interaction and isomer energies, and other, more commonly used coupled-cluster methods (such as CCSD , ) were also shown to perform well.…”

Photochemistry of Monohydrated Chloromethane: Formation of Free and Hydrated Cl– and CH3+ Ions from a Solvent-Shared Semi-Ion-Pair

“…Main geometrical parameters of the structures studied in this work, obtained at the CISD/MR-CISD level. Reference values are from: a ref ; b ref ; c ref ; d ref ; e ref ; f ref ; and g ref . For most of the structures, the aug-cc-pVTZ basis set has been used, while for Cl – (H 2 O) (the only exception) the d-aug-cc-pVTZ­(Cl)/aug-cc-pVTZ­(C,H,O) basis set has been used.…”