The Structure and Spectroscopy of Cyanate and Bicarbonate Ions. Astrophysical Implications

Abstract

Cyanate and bicarbonate are two ions that play active roles in many fields of physics and chemistry, including biological sciences and astrochemistry. We present here a comprehensive study of these species covering a range of phases and methodologies. We have performed theoretical calculations on the isolated ions and their hydrates with one to four water molecules, and in clusters with 15 water molecules. The predicted infrared spectra are compared with observed spectra from experiments where liquid droplets of their solutions are frozen at 14 K on a substrate, to mimic some astrophysical conditions. Crystals of cyanate and bicarbonate sodium and potassium salts are also studied experimental and theoretically. As well, the spontaneous decomposition of cyanate into bicarbonate is documented from the spectra of an aged solution. Finally, the possible astrophysical observation of bicarbonate in watercontaining particles is discussed.

JWST Observations of Young protoStars (JOYS+): Detecting icy complex organic molecules and ions

“…In addition to COMs, ions such as OCN − (cyanate ion), HCOO − and NH + 4 have been proposed to be present in interstellar ices mostly as part of salts produced by acid-base reactions (e.g., Geballe 1984;Grim & Greenberg 1987;Schutte et al 1999;Schutte & Khanna 2003;Gálvez et al 2010;Maté et al 2012;Moreno et al 2013;Bergner et al 2016;Kruczkiewicz et al 2021). The presence of OCN − in ice mantles can be considered a secure detection based on comprehensive laboratory experiments and extensive analysis toward several protostars (e.g., Geballe 1984;van Broekhuizen et al 2004) and toward background stars (McClure et al 2023), and the good correlation between gas-phase abundances of HNCO and OCN − ice (Öberg et al 2009a).…”

Photoelectron Spectroscopy and Theoretical Study on Monosolvated Cyanate Analogue Clusters ECX–·Sol (ECX– = NCSe–, AsCSe–, and AsCS–; Sol = H2O, CH3CN)

“…Specifically, for the NCSe – ·H 2 O case, calculations point to the existence of two isomers, whose energies are very close to each other. Similar to previously reported results for NCO – ·H 2 O and NCS – ·H 2 O, the lowest energy structure (Iso I) is characterized by water forming one hydrogen bond (HB) with the N-terminal of NCSe – . The calculated VDE and SO splitting (3.762 eV and 1671 cm –1 ) suggest that it is Iso I that gives rise to the main experimental peak at 3.70 eV with an SO splitting of 1653 cm –1 (Table ).…”

“…Gas-phase ion spectroscopy coupled with high-level quantum chemical computations has been demonstrated as an ideal technique to obtain the geometric and electronic structure information for microsolvated clusters and to provide a molecular-level understanding of solute–solvent and solvent–solvent interactions. − The method has been shown to provide a sensitive probe of subtle solvation differences between different yet overall similar solutes, such as CN – · n H 2 O, , NCO – · n H 2 O, and NCS – · n H 2 O. , It also allows one to examine different solvation behaviors with different solvent molecules, e.g., water (H 2 O) versus acetonitrile (CH 3 CN), two common but very different solvents with their respective solvation binding motifs driven by the formation of hydrogen bonding in H 2 O , and charge–dipole interaction in CH 3 CN. − , …”

“…Herein, we present a joint effort of NIPES and theoretical calculations on three newly synthesized heavier cyanate analogues NCSe – , AsCS – , and AsCSe – solvated by one H 2 O or CH 3 CN molecule with the aim of obtaining (1) different solvation behaviors compared to their well-studied NCO – and NCS – analogs, , (2) different solvation binding motifs between H 2 O and CH 3 CN, and (3) similarity and distinctions of solvation among themselves. Such a study is expected to provide a detailed comparison of their solvation properties by varying the solute and solvent to explore the possible binding motifs between these heavier ECX – anions and solvents as well as different solvent effects for the same solute.…”

“…26,38 It also allows one to examine different solvation behaviors with different solvent molecules, e.g., water (H 2 O) versus acetonitrile (CH 3 CN), two common but very different solvents with their respective solvation binding motifs driven by the formation of hydrogen bonding in H 2 O 28,31 and charge−dipole interaction in CH 3 CN. [29][30][31]45 Herein, we present a joint effort of NIPES and theoretical calculations on three newly synthesized heavier cyanate analogues NCSe − , AsCS − , and AsCSe − solvated by one H 2 O or CH 3 CN molecule with the aim of obtaining (1) different solvation behaviors compared to their well-studied NCO − and NCS − analogs, 38,44 (2) different solvation binding motifs between H 2 O and CH 3 CN, and (3) similarity and distinctions of solvation among themselves. Such a study is expected to provide a detailed comparison of their solvation properties by varying the solute and solvent to explore the possible binding motifs between these heavier ECX − anions and solvents as well as different solvent effects for the same solute.…”