Unraveling the protonation site of oxazole and solvation with hydrophobic ligands by infrared photodissociation spectroscopy
| dc.contributor.author | Chatterjee, Kuntal | |
| dc.contributor.author | Dopfer, Otto | |
| dc.date.accessioned | 2019-08-19T13:57:08Z | |
| dc.date.available | 2019-08-19T13:57:08Z | |
| dc.date.issued | 2019-01-19 | |
| dc.description.abstract | Protonation and solvation of heterocyclic aromatic building blocks control the structure and function of many biological macromolecules. Herein the infrared photodissociation (IRPD) spectra of protonated oxazole (H+Ox) microsolvated by nonpolar and quadrupolar ligands, H+Ox-Ln with L = Ar (n = 1–2) and L = N2 (n = 1–4), are analyzed by density functional theory calculations at the dispersion-corrected B3LYP-D3/aug-cc-pVTZ level to determine the preferred protonation and ligand binding sites. Cold H+Ox-Ln clusters are generated in an electron impact cluster ion source. Protonation of Ox occurs exclusively at the N atom of the heterocyclic ring, in agreement with the thermochemical predictions. The analysis of the systematic shifts of the NH stretch frequency in the IRPD spectra of H+Ox-Ln provides a clear picture of the sequential cluster growth and the type and strength of various competing ligand binding motifs. The most stable structures observed for the H+Ox-L dimers (n = 1) exhibit a linear NH⋯L hydrogen bond (H-bond), while π-bonded isomers with L attached to the aromatic ring are local minima on the potential and thus occur at a lower abundance. From the spectra of the H+Ox-L(π) isomers, the free NH frequency of bare H+Ox is extrapolated as νNH = 3444 ± 3 cm−1. The observed H+Ox-L2 clusters with L = N2 feature both bifurcated NH⋯L2 (2H isomer) and linear NH⋯L H-bonding motifs (H/π isomer), while for L = Ar only the linear H-bond is observed. No H+Ox-L2(2π) isomers are detected, confirming that H-bonding to the NH group is more stable than π-bonding to the ring. The most stable H+Ox-(N2)n clusters with n = 3–4 have 2H/(n − 2)π structures, in which the stable 2H core ion is further solvated by (n − 2) π-bonded ligands. Upon N-protonation, the aromatic C–H bonds of the Ox ring get slightly stronger, as revealed by higher CH stretch frequencies and strongly increased IR intensities. | en |
| dc.description.sponsorship | TU Berlin, Open-Access-Mittel - 2019 | en |
| dc.identifier.eissn | 1463-9084 | |
| dc.identifier.issn | 1463-9076 | |
| dc.identifier.uri | https://depositonce.tu-berlin.de/handle/11303/9812 | |
| dc.identifier.uri | http://dx.doi.org/10.14279/depositonce-8834 | |
| dc.language.iso | en | en |
| dc.relation.ispartof | 10.14279/depositonce-10571 | en |
| dc.rights.uri | https://creativecommons.org/licenses/by/3.0/ | en |
| dc.subject.ddc | 540 Chemie und zugeordnete Wissenschaften | de |
| dc.subject.other | heterocyclic aromatic building block | en |
| dc.subject.other | nonpolar ligand | en |
| dc.subject.other | quadrupolar ligand | en |
| dc.subject.other | IRPD | en |
| dc.title | Unraveling the protonation site of oxazole and solvation with hydrophobic ligands by infrared photodissociation spectroscopy | en |
| dc.type | Article | en |
| dc.type.version | publishedVersion | en |
| dcterms.bibliographicCitation.doi | 10.1039/C9CP02787D | en |
| dcterms.bibliographicCitation.issue | 27 | en |
| dcterms.bibliographicCitation.journaltitle | Physical Chemistry Chemical Physics | en |
| dcterms.bibliographicCitation.originalpublishername | Royal Society of Chemistry | en |
| dcterms.bibliographicCitation.originalpublisherplace | London | en |
| dcterms.bibliographicCitation.pageend | 15166 | en |
| dcterms.bibliographicCitation.pagestart | 15157 | en |
| dcterms.bibliographicCitation.volume | 21 | en |
| tub.accessrights.dnb | free | en |
| tub.affiliation | Fak. 2 Mathematik und Naturwissenschaften::Inst. Optik und Atomare Physik::FG Lasermolekülspektroskopie und Umweltphysik | de |
| tub.affiliation.faculty | Fak. 2 Mathematik und Naturwissenschaften | de |
| tub.affiliation.group | FG Lasermolekülspektroskopie und Umweltphysik | de |
| tub.affiliation.institute | Inst. Optik und Atomare Physik | de |
| tub.publisher.universityorinstitution | Technische Universität Berlin | en |