Molecular geometries and other properties of H2O⋯AgI and H3N⋯AgI as characterised by rotational spectroscopy and ab initio calculations

Abstract

The rotational spectra of HN⋯AgI and HO⋯AgI have been recorded between 6.5 and 18.5 GHz by chirped-pulse Fourier-transform microwave spectroscopy. The complexes were generated through laser vaporisation of a solid target of silver or silver iodide in the presence of an argon gas pulse containing a low concentration of the Lewis base. The gaseous sample subsequently undergoes supersonic expansion which results in cooling of rotational and vibrational motions such that weakly bound complexes can form within the expanding gas jet. Spectroscopic parameters have been determined for eight isotopologues of HN⋯AgI and six isotopologues of HO⋯AgI. Rotational constants, B; centrifugal distortion constants, D, D or Δ, Δ; and the nuclear quadrupole coupling constants, χ(I) and χ(I) - χ(I) are reported. HN⋯AgI is shown to adopt a geometry that has C symmetry. The geometry of HO⋯AgI is C at equilibrium but with a low barrier to inversion such that the vibrational wavefunction for the v = 0 state has C symmetry. Trends in the nuclear quadrupole coupling constant of the iodine nucleus, χ(I), of L⋯AgI complexes are examined, where L is varied across the series (L = Ar, HN, HO, HS, HP, or CO). The results of experiments are reported alongside those of ab initio calculations at the CCSD(T)(F12*)/AVXZ level (X = T, Q).

The microwave spectrum of the C2H2…AgI complex assigned and analysed using PGOPHER

“…While working alongside Colin Western at the University of Bristol, the authors learned to exploit PGOPHER to unlock difficult challenges in the assignment and fitting of broadband microwave spectra. This supported a series of publications [2] describing analyses of the rotational spectra of B…MX complexes where B is a typical Lewis base (eg NH 3 , H 2 O, C 2 H 4 , C 2 H 2 ), M is a coinage metal and X is a halogen atom. The present work will extend this programme by reporting on the assignment and analysis of the microwave spectrum of C 2 H 2 …AgI.…”

“…Carbon monoxide [3] and phosphine [28] each interact more strongly with the Ag− I sub-unit and cause a much greater change. The attachment of ethyne leads to a change that is intermediate between the extremes described above and comparable in magnitude to that caused by attachment [2] of NH 3 .…”

Decoding the Structure of Non-Proteinogenic Amino Acids: The Rotational Spectrum of Jet-Cooled Laser-Ablated Thioproline

“…The laser ablation nozzle consists of a standard solenoid valve with the nozzle adapted to a homemade extension cap as described elsewhere [ 38 ]. A solid rod of the sample was prepared by grinding the sample and mixing it with a small amount of Cu powder [ 57 ] which is pressed to form cylindrical rods of about 1 cm in diameter. The sample rod is held in a channel of appropriate dimensions perpendicular to a small cylinder tube coaxial with the nozzle through which the carrier gas expands (Ar at backing pressures of 2 bar).…”

Bifunctional Hydrogen Bonding of Imidazole with Water Explored by Rotational Spectroscopy and DFT Calculations

“…Both the laser vaporization source and the CP-FTMW spectrometer used by the present experiments have been described in detail elsewhere. − The focused pulse of a Nd:YAG laser (Photonics Solutions, Minilite II, 1064 nm, 43 mJ pulse –1 ) is used to vaporize a solid target of imidazole to generate the gaseous sample required by the spectroscopic experiments. When performing experiments on the parent isotopologues of imid···H 2 O and H 2 O···imid, a solid matrix of silver iodide (Fisher Scientific, 99%, ACROS Organics) was used while experiments performed on D 2 O/HDO-containing isotopologues employed a copper powder (Sigma-Aldrich, <75 μm, 99%) matrix.…”