Vacuum-ultraviolet (VUV) photolysis of methylphosphine (CH₃PH₂) isolated in a cryogenic argon matrix yields phosphaethene (CH₂=PH), methylphosphinidene (CH₃P), phosphaethyne (HCP), methane, and phosphorus monohydride (PH) as the primary photoproducts. Subsequent irradiation...

1-Arsabutadiyne (2-propynylidynearsine, HC3As), is efficiently produced by photolysis of propynylarsine isolated in solid argon. The observed infrared absorption spectra and predicted molecular parameters of HC3As and HC3P show significant similarities, but large differences compared to HC3N.

The photochemistry of phosphabut-1-yne, CH3CH2CP, was investigated by means of infrared spectroscopy assisted by theoretical (DFT) predictions. The UV-irradiated compound, isolated in a cryogenic argon matrix, undergoes isomerization and dissociation. Several isomers of phosphabutyne, in addition to phosphabutadiyne (HC3P), ethynylphosphinidene (HCCP), and phoshaethyne (HCP) are formed as the main photoproducts. Vibrational spectra of astrochemically relevant molecules HC3P and CH2CHCP (vinylphosphaethyne), have been detected and analyzed here for the first time.

Correction for 'Isomerisation of phosphabutyne and a photochemical route to phosphabutadiyne (HC3P), a phosphorus analogue of cyanoacetylene' by Arun-Libertsen Lawzer et al., Phys. Chem. Chem. Phys., 2025, https://doi.org/10.1039/d4cp04182h.

Isotopic (2H and 15N) labelling and IR absorption spectroscopy have been used to study UV-induced transformations of cyanoacetylene in cryogenic noble gas matrices. The results obtained indicate that all observed isomerization processes involve single, isolated molecules of the precursor. No photoproducts have been found that would imply the recombination of fragments originating from different molecules.

Until now, there has been very little experimental evidence for the existence of free arsinidenes and stibinidenes, apart from the hydrides, AsH and SbH. Here, we report on photogeneration of triplet ethynylarsinidene, HCCAs, and triplet ethynylstibinidene, HCCSb, from ethynylarsine and ethynylstibine, respectively, in solid argon matrices. The products were identified using infrared spectroscopy and the associated UV absorption spectra are interpreted with the aid of theoretical predictions.

Phosphorescence of C5N− was discovered following the ArF-laser (193 nm) photolysis of cyanodiacetylene (HC5N) isolated in cryogenic argon, krypton, and xenon matrices. This visible emission, with an origin around 460 nm, is vibrationally resolved, permitting the measurement of frequencies for eight ground-state fundamental vibrational modes, including the three known from previous IR absorption studies. Phosphorescence lifetime amounts to tens or even hundreds of ms depending on the matrix host; it is five times longer than in the case of HC5N.

Highly unsaturated chain molecules are interesting due to their potential application as nanowires and occurrence in interstellar space. Here, we focus on predicting the electronic spectra of polyynic nitriles HC2m+1N (m = 0–13) and dinitriles NC2n+2N (n = 0–14). The results of time-dependent density functional theory (TD-DFT) calculations are compared with the available gas-phase and noble gas matrix experimental data. We assessed the performance of fifteen functionals and five basis sets for reproducing (i) vibrationless electronic excitation energies and (ii) vibrational frequencies in the singlet excited states. We found that the basis sets of at least triple-ζ quality were necessary to describe the long molecules with alternate single and triple bonds. Vibrational frequency scaling factors are similar for the ground and excited states. The benchmarked spectroscopic parameters were shown to be acceptably reproduced with adequately chosen functionals, in particular ωB97X, CAM-B3LYP, B3LYP, B971, and B972. Select functionals were applied to study the electronic excitation of molecules up to HC27N and C30N2. It is demonstrated that optical excitation leads to a shift from the polyyne- to a cumulene-like electronic structure.

We report the first detection of phosphorescence from the phosphaethynyl radical. This rare instance of quartet-doublet emission, studied here in solid argon, is presumably promoted by efficient intersystem crossing from the originally photoexcited doublet (B 2 Σ + ) to the adjacent second quartet state, 1 4 Δ. Vibronic progressions were traced for the a 4 Σ + -X 2 Σ + and a 4 Σ + -A 2 П i systems from their origins up to (v′=0)→(v′′=5) and (v′=0)→(v′′=2) bands, respectively. The measured phosphorescence lifetime is 108 ± 3 ms.

While the archetypal free phosphinidene, H-P, has been studied for over a century, reports on uncomplexed, univalent phosphorus compounds are very sparse. Here we demonstrate production of HCCP in solid argon through the UV-induced rearrangement and subsequent dehydrogenation of phosphapropyne, CH3 CP. Migration of H atoms along the CCP backbone of CH3 CP resulted in production of the previously unobserved species 1-phosphapropadiene, CH2 =C=PH, followed by ethynylphosphine, HCCPH2 .

Electronic phosphorescence and infrared absorption spectra of methylcyanodiacetylene (CH3C5N) are revisited using matrix isolation in solid parahydrogen and neon. Band assignments previously found for Ar, Kr, Xe, and N2 low-temperature host media were updated, with certain ambiguous attributions being resolved. A combined analysis of both dispersed phosphorescence and phosphorescence excitation spectra observed in different environments provides a means to estimate the singlet-triplet separation for the gas-phase and pure solid compound, where phosphorescence could not be observed.

Here we present the results of a joint spectroscopic and quantum chemical study on the photochemistry of 3-iodo-2-propynenitrile (iodocyanoacetylene, IC3N). Vacuum-UV photolysis of the compound isolated in solid argon was explored. Calculations, carried out at the DFT and/or coupled-cluster level of theory, provided essential data concerning the thermodynamic stabilities, vibrational and electronic energy levels, ionization potentials, and electron affinities of IC3N-stoichiometry isomers and ions. The photochemical formation of thus far unknown species IC2NC and ICNC2 has been evidenced by the experiment and rationalized based on a detailed theoretical approach, involving the excited-state potential energy surfaces.

Cyanopolyyne molecules, HC9N and HC11N, were isolated in solutions and UV, IR, and resonance Raman spectra were measured for the study of their electronic and vibrational properties. Strong signals were observed both in the IR and resonance Raman spectra for the stretching vibrational mode of the sp-hybridized linear carbon chain in the electronic ground state, i.e., sigma(4) at 2141 cm(-1) for HC9N and sigma(6) at 2105 cm(-1) for HC11N. Trapped in cryogenic solid acetonitrile matrix hosts at 20 K, transitions in phosphorescence, (a) over tilde (3)Sigma(+) -> (X) over tilde (1)Sigma(+), were observed for HC9N at 582.3 nm (0-0) and longer wavelengths and for HC11N at 643.7 nm (0-0) and longer wavelengths. Electronic transitions in the UV, (1)Sigma(+) <- (X) over tilde (1)Sigma(+), were elucidated by phosphorescence excitation mapping to observe asymmetric patterns with sharp emission-absorption features explainable by Shpolsky effects. For HC9N, three distinct trapping sites were discernible in solid acetonitrile, while the phosphorescence spectra were blurred in solid n-hexane. The observed phosphorescence lifetime of HC9N was longer than that of HC11N, comparable to the trend reported for the series of cyanopolyyne molecules in solid krypton matrix hosts. (C) 2020 Elsevier B.V. All rights reserved.

As demonstrated in recent years, polyynic nitriles may photochemically arise from smaller unsaturated chain species in an apparently rigid environment of a cryogenic rare gas matrix. Here I summarize the highlights of respective research that has advanced the spectroscopic description of R–(C≡C)n–C≡N molecules (R = H, CN or CH3).

Cyanopropyne, CH3-C[triple bond, length as m-dash]C-CN, is a simple molecule whose photochemistry is still unexplored. Here we investigate the UV photolysis of this astrophysically significant nitrile trapped in solid argon. The FTIR study was assisted with 15N-isotopic substitution data and with DFT-level computations including the analyses of ground- and excited-state potential energy surfaces. Cyanopropyne was found to decay mainly via a two-step isomerization process. Infrared absorption spectra evolved to show signals from allenyl cyanide, CH2[double bond, length as m-dash]C[double bond, length as m-dash]CH-CN, which then further convert into propargyl cyanide, H-C[triple bond, length as m-dash]C-CH2-CN. Some evidence for the presence of allenyl isocyanide, propargyl isocyanide, 3-cyanocyclopropene, and 1,2,3-butatrien-1-imine under particular experimental conditions was also observed. Although cyano/isocyano interconversion has been observed during photolysis of other closely related species in solid argon matrices, including H-C[triple bond, length as m-dash]C-CN, no evidence could be found for production of 1-isocyano-1-propyne, CH3-C[triple bond, length as m-dash]C-NC for these experiments.

The rodlike 1,8-dicyano-octa-1,3,5,7-tetrayne (NC10N) molecule was synthesized with UV-assisted coupling of rare-gas matrix-isolated cyanobutadiyne (HC5N) molecules. Detection of NC10N molecule was possible due to its strong orange-red (origin at 618 nm) electronic luminescence. Excitation spectra of this emission (ã 3Σu+-X̃ 1Σg+ phosphorescence) gave access to studying the fully allowed H̃ 1Σu+-X̃ 1Σg+ UV system of NC10N. The identification of observed spectral features was assisted with quantum chemical computations. Certain regularities shaping the electronic spectroscopy of NC2 nN molecules have been discussed.

This paper reports on UV-stimulated synthesis of methylcyanotriacetylene carried out in cryogenic rare gas matrixes via coupling of smaller precursors: propyne and cyanodiacetylene. The detection was possible due to the strong visible ã 3A' → X̃ 1A1 phosphorescence of CH3C7N, discovered in the course of this work. The ensuing measurements of electronic spectroscopy revealed the formally forbidden B̃ 1E-X̃ 1A1 system, as well as the allowed one Ẽ 1A1-X̃ 1A1, with origins at approximately 3.32 and 5.4 eV, respectively. It was also possible to revisit the spectroscopic characterization of cyanotriacetylene, HC7N, formed in parallel to the title photoproduct. Spectral assignments were assisted with a density functional theory study.

HC9N is a molecule of astrochemical interest. In this study, it was produced in cryogenic Ar and Kr matrices from UV-photolyzed diacetylene/cyanodiacetylene mixtures. Its strong phosphorescence was discovered and served for the identification of the compound. Vibrationally resolved phosphorescence excitation spectra gave insight into excited singlet electronic states. Two electronic systems were observed around 26 000-34 000 cm-1 and 35 000-50 000 cm-1. Energies of the second excited singlet and the lowest triplet state were derived from analysis of these systems. Vibrational and electronic spectroscopic features were assigned with the assistance of density functional theory calculations. Some trends concerning the electronic spectroscopy of HC2n+1N family molecules are presented.