Modeling the IR Spectra of Aqueous Metal Carboxylate Complexes: Correlation between Bonding Geometry and Stretching Mode Wavenumber Shifts

Abstract

A widely used principle is that shifts in the wavenumber of carboxylate stretching modes upon bonding with a metal center can be used to infer if the geometry of the bonding is monodentate or bidentate. We have tested this principle with ab initio modeling for aqueous metal carboxylate complexes and have shown that it does indeed hold. Modeling of the bonding of acetate and formate in aqueous solution to a range of cations was used to predict the infrared spectra of the metal-carboxylate complexes, and the wavenumbers of the symmetric and antisymmetric vibrational modes are reported. Furthermore, we have shown that these shifts in wavenumber occur primarily due to how bonding with the metal changes the carboxylate C-O bond lengths and O-C-O angle.

Molecular Vibrations of an Oxygen‐Evolving Complex and Its Synthetic Mimic

“…Therefore, as the asymmetry of the carboxylate group becomes larger,t he frequencies approach the C=Oa nd CÀOs tretching modes,r espectively,sot hat their frequency differencei ncreases. [43,44] The same clear correlation in value with d(CO) is observed for the natural complex( Ta ble3).…”

Negative‐Imaging of Citrate Layers on Gold Nanoparticles by Ligand‐Templated Metal Deposition: Revealing Surface Heterogeneity

“…In general, however, the bond energy of Au(I)‒X is larger than that of Au(0)‒X, and the binding energy of citrate carboxylate to the AuNP surface can be in the range of chemisorption owing to the positively charged low‐coordinated Au adatom . Therefore, it is the Au adatom that causes the strong citrate adsorption on AuNPs, with bond energy of Au‒carboxylate similar to the metal‒oxygen bond energies determined between metal cation and acetate (median energy range: 10‒25 kcal mol −1 ) …”

Structurally diverse coordination compounds of zinc as effective precursors of zinc oxide nanoparticles with various morphologies

“…The strongest bands in all spectra correspond to asymmetric and symmetric stretching vibrations of carboxylate groups ( ν as COO and ν s COO). The separation parameter Δ ν (difference between wavenumbers of ν as COO and ν s COO), which is commonly used to establish a functionality and denticity of carboxylate groups in coordination compounds, reflects appropriately the coordination behaviour of carboxylate anions in the studied compounds. In the spectra of compounds 3 – 5 , the two bands of ν as COO are observed, as a consequence of two different coordination modes of carboxylate anions in each of these compounds.…”