The hitherto elusive 1H-triphosphirene (c-HP3) and 2-triphosphenylidene (HP3) molecules were prepared in low-temperature matrices and detected isomer selectively through photoionization coupled with reflectron time-of-flight mass spectrometry (PI-ReTOF-MS). Our results reveal a thermodynamically preferred cyclic isomer (c-HP3) compared to the acyclic structure (HP3) in contrast to the isovalent HN3 system favoring hydrazoic acid (HN3) compared to 1H-triazirine (c-HN3). Theoretical computations suggest a ring strain energy of 1H-triphosphirene (c-HP3) of only 35 kJ mol–1, which is significantly lower than the tetrahedral phosphorus molecule (P4) of 74 kJ mol–1. This work provides a fundamental benchmark to understand the electronic structure and chemical bonding of cyclic molecules and offers an unconventional approach to preparing highly strained, still elusive molecules such as 1H-triazirine and tetrahedral tetranitrogen (N4) in the near future involving progressive nonequilibrium chemistries.
The tetrahedral 1,2,3-triphospha-4-azatricyclo [1.1.0.0 2,4 ] butane (P 3 N) molecule—an isovalent species of phosphorus (P 4 )—was prepared in low-temperature (5 K) phosphine-nitrogen ices and was identified in the gas phase through isomer-selective, tunable, soft photoionization reflectron time-of-flight mass spectrometry. Theoretical calculations reveal that the substitution of a single phosphorus atom by nitrogen in the P 4 molecule results in enhanced spherical aromaticity while simultaneously increasing the strain energy from 74 to 195 kJ mol −1 . In P 3 N, the P─P bond is shortened compared to those in P 4 by 3.6 pm, while the P─N─P bond angle of 73.0° is larger by 13.0° compared to the P─P─P bond angle of 60.0° in P 4 . The identification of tetrahedral P 3 N enhances our fundamental understanding of the chemical bonding, electronic structure, and stability of binary, interpnictide tetrahedral molecules and reveals a universal route to prepare ring strained cage molecules in extreme environments.
Kuiper Belt objects exhibit a wider color range than any other solar system population. The origin of this color diversity is unknown, but likely the result of the prolonged irradiation of organic materials by galactic cosmic rays (GCRs). Here, we combine ultrahigh-vacuum irradiation experiments with comprehensive spectroscopic analyses to examine the color evolution during GCR processing methane and acetylene under Kuiper Belt conditions. This study replicates the colors of a population of Kuiper Belt objects such as Makemake, Orcus, and Salacia. Aromatic structural units carrying up to three rings as in phenanthrene (C 14 H 10 ), phenalene (C 9 H 10 ), and acenaphthylene (C 12 H 8 ), of which some carry structural motives of DNA and RNA connected via unsaturated linkers, were found to play a key role in producing the reddish colors. These studies demonstrate the level of molecular complexity synthesized of GCR processing hydrocarbon and hint at the role played by irradiated ice in the early production of biological precursor molecules.
We report the formation of the cyclic methylphosphonic acid trimer [c-(CH 3 PO 2 ) 3 ] through condensation reactions during thermal processing of low-temperature methylphosphonic acid samples exploiting photoionization reflectron time-of-flight mass spectrometry (PIÀ ReTOFÀ MS) along with electronic structure calculations. Cyclic methylphosphonic acid trimers are formed in the solid state and detected together with its protonated species in the gas phase upon single photon ionization. Our studies provide an understanding of the preparation of phosphorus-bearing potentially prebiotic molecules and the fundamental knowledge of low-temperature phosphorus chemistry in extraterrestrial environments.
Amines—organic molecules carrying the –NH2 moiety—have been recognized as a vital intermediate in the formation of prebiotic molecules such as amino acids and nucleobases. Here we report the formation of vinylamine (C2H3NH2), which was recently detected toward G+0.693–0.027, in interstellar ice analogs composed of acetylene (C2H2) and ammonia (NH3) exposed to energetic electrons. Our experiments mimic cascades of secondary electrons in the tracks of galactic cosmic rays impinging on interstellar ice in molecular clouds. Tunable photoionization reflectron time-of-flight mass spectrometry (PI–Re-TOF–MS), along with isomer-specific assignments, reveals the production of vinylamine (C2H3NH2). Quantum chemical computations suggest that both a radical–radical recombination of the amino (NH2) with the vinyl (C2H3) radical and a one-step concerted route are feasible pathways to vinylamine (C2H3NH2). The results present the first documented route to form vinylamine in interstellar ice analogs. This unsaturated amine, which is isovalent to vinylalcohol (C2H3OH), could be a key precursor for the abiotic synthesis of prebiotic molecules such as amino acids and nucleobases, with implications for the origins-of-life theme.
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