IR photodissociation spectroscopy of (OCS)n+ and (OCS)n− cluster ions: Similarity and dissimilarity in the structure of CO2, OCS, and CS2 cluster ions

Abstract

Infrared photodissociation (IRPD) spectra of (OCS)n(+) and (OCS)n(-) (n = 2-6) cluster ions are measured in the 1000-2300 cm(-1) region; these clusters show strong CO stretching vibrations in this region. For (OCS)2 +) and (OCS)2(-), we utilize the messenger technique by attaching an Ar atom to measure their IR spectra. The IRPD spectrum of (OCS)2 (+)Ar shows two bands at 2095 and 2120 cm(-1). On the basis of quantum chemical calculations, these bands are assigned to a C2 isomer of (OCS)2 (+), in which an intermolecular semi-covalent bond is formed between the sulfur ends of the two OCS components by the charge resonance interaction, and the positive charge is delocalized over the dimer. The (OCS)n(+) (n = 3-6) cluster ions show a few bands assignable to "solvent" OCS molecules in the 2000-2080 cm(-1) region, in addition to the bands due to the (OCS)2(+) ion core at ∼2090 and ∼2120 cm(-1), suggesting that the dimer ion core is kept in (OCS)3-6(+). For the (OCS)n(-) cluster anions, the IRPD spectra indicate the coexistence of a few isomers with an OCS(-) or (OCS)2(-) anion core over the cluster range of n = 2-6. The (OCS)2(-)Ar anion displays two strong bands at 1674 and 1994 cm(-1). These bands can be assigned to a Cs isomer with an OCS(-) anion core. For the n = 2-4 anions, this OCS(-) anion core form is dominant. In addition to the bands of the OCS(-) core isomer, we found another band at ∼1740 cm(-1), which can be assigned to isomers having an (OCS)2(-) ion core; this dimer core has C2 symmetry and (2)A electronic state. The IRPD spectra of the n = 3-6 anions show two IR bands at ∼1660 and ∼2020 cm(-1). The intensity of the latter component relative to that of the former one becomes stronger and stronger with increasing the size from n = 2 to 4, which corresponds to the increase of "solvent" OCS molecules attached to the OCS(-) ion core, but it suddenly decreases at n = 5 and 6. These IR spectral features of the n = 5 and 6 anions are ascribed to the formation of another (OCS)2(-) ion core having C2v symmetry with (2)B2 electronic state.

Vacuum Ultraviolet Photoionization Induced Proton Migration and Formation of a New C–N Bond in Pyridine Clusters Revealed by Infrared Spectroscopy and Mass Spectrometry

“…For group (i), the structure with the N··N bond is the most stable one. Similar structures have been reported for (H 2 S) n + , (CH 3 SH) n + , , and the trimethylamine dimer cation. − The calculated IP 0 of the N··N isomer at the ωb97XD/aug-cc-pVDZ level is 7.78 eV, which is 1.55 eV lower than the VUV energy (9.33 eV). Other weakly bound isomers are ∼1 eV higher in energy.…”

Noncovalent chalcogen and tetrel bonding interactions: Spectroscopic study of halide–carbonyl sulfide complexes

“…Collectively, these structures can be seen in Figure 5. Homogeneous carbonyl sulfide anion complexes have been studied both computationally and experimentally and found to feature a distinct carbonyl sulfide molecular anion dimer with the additional carbonyl sulfide solvating the dimer core 88–91 . In contrast to the homogeneous anion complexes, the halide anion retains the excess negative charge and as such, no carbonyl sulfide molecular dimer formation has been observed.…”

Correlation of the Charge Resonance Interaction with Cluster Conformations Probed by Electronic Spectroscopy of Dimer Radical Cations of CO2 and CS2 in a Cryogenic Ion Trap

“…In this bonding scheme, the total charge is distributed across the components. Because the formal bond order in this bonding mode is 0.5 (Scheme ), such bonds are often referred to as semi-covalent bonds or hemibonds. − Remarkably, the electronic transition from σ to σ* orbitals in this bonding scheme, known as the CR transition, leads to a prominent absorption band in the near-infrared–visible region (CR band). − Consequently, the spectroscopic characterizations have attracted considerable attention. − Particularly, when the corresponding electronic ground and excited states (Ψ ± ) are described as Ψ ± = [ψ(M A + )ψ(M B ) ± ψ(M A )ψ(M B + )]/(2 ± 2 S ) 1/2 , the CR transition energy ( E T ) is directly related to the binding energy between the component molecules in the dimer ions ( E B ), as illustrated in the following relationship (eq ): E normalT = 2 E normalB 1 − S Here, S represents the overlap integral between the constituent molecules.…”

“…Specifically, we herein focused on the radical cations of carbon dioxide and carbon disulfide dimers [(CX 2 ) 2 ] +• (X = O and S) as target clusters. They have been extensively examined for decades as prototypical examples of ions exhibiting the CR interaction. ,,,,,− The dimer ions serve as highly stable ion cores in larger clusters, [(CX 2 ) n ] +• ( n ≥ 3), as revealed by infrared photodissociation (IR-PD) spectroscopy. , With regard to electronic spectroscopy, the broad CR band of [(CO 2 ) 2 ] +• at 12 500–25 000 cm –1 has been reported under ambient temperature conditions. , This study aims to investigate how the CR interaction in [(CX 2 ) 2 ] +• appears under temperature-regulated conditions using near-infrared–visible photodissociation (NIR–vis-PD) spectroscopy. We will establish how the band profile evolves with temperature change and discuss the correlation with the cluster conformations as well as the CR interactions.…”