Infrared photodissociation spectroscopic and theoretical study of H_nC₄O⁺ (n = 1, 2) cation clusters in the gas phase

Abstract

The carbon chain cations H_nC₄O⁺ (n = 1, 2) were generated via pulsed laser vaporisation of a graphite target in supersonic expansions of helium seeded with carbon monoxide and acetylene. The infrared spectra were measured via mass-selected infrared photodissociation spectroscopy of their CO-tagged complexes [H_nC₄O·CO]⁺ (n = 1, 2). Their geometric and electronic structures were determined by gas-phase infrared photodissociation spectra combined with theoretical calculations. The results show that the H_nC₄O⁺ (n = 1, 2) core cations are linear carbon chain derivatives which are terminated with hydrogen/dihydrogen and oxygen atoms. The HC₄O⁺ cation has ³Σ⁻ electronic ground state with cumulene-like carbon chain structure, while H₂C₄O⁺ cation has ²B₁ electronic ground state with polyyne-like carbon chain structure. The CH and CH₂ terminal groups have different influence on the type of carbon-carbon bonds in the carbon chain derivatives, due to the sp and sp² hybridisation property.

The carbon chain cations H_nC₄O⁺ (n = 1, 2) are studied by gas-phase infrared photodissociation spectra of CO-tagged complexes [H_nC₄O·CO]⁺ (n = 1, 2) combined with theoretical calculations. Studies show that the structures of the H_nC₄O⁺ (n = 1, 2) core cations are linear carbon chain derivatives which are terminated with hydrogen/dihydrogen and oxygen atoms. The spectrum of [HC₄O·CO]⁺ shows two bands above 3000 cm⁻¹, suggesting possible isomers.

GRAPHICAL ABSTRACT

KEYWORDS:

• Carbon chain cation
• infrared photodissociation spectroscopy
• theoretical calculation
• cumulene-like carbon chain
• polyyne-like carbon chain

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

^a The linear CO tagged complex of HC₄O⁺.

^b The T-shape CO tagged complex of HC₄O⁺.

^c The T-shape CO tagged complex of H₂C₄O⁺.

^d The H-bonded CO tagged complex of H₂C₄O⁺.

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [grant numbers 21603037, 21688102, 21973016, 91545122, 11974108], the Fundamental Research Funds for the Central Universities [grant numbers JB2015RCY03, JB2019MS052] supported by the fund of North China Electric Power University and the National Key Research and Development Program of China [grant number 2016YFA0202401].