Roger J. Suffolk

A photoelectron spectroscopic and theoretical study of the halogen and hydrogen thiocyanates and isothiocyanates

Abstract Photoelectron spectroscopic and ab initio theoretical studies of the halogen and hydrogen thiocyanates (XSCN; X = H, F, Cl, Br and I) and isothiocyanates (XNCS; X = H, F, Cl, Br and I) are reported. Spectroscopic evidence for the new molecule ISCN is given. The five lowest IPs of this molecule are 9.75, 11.48, 11.86, 11.98, and 12.79 eV. The seleno analogue, ISeCN has also been prepared and has a first IP of 9.79 eV. The theoretical section includes ab initio computation of molecular geometries, isomer energy differences and ionization potentials, mostly carried out at the SCF level using the polarized 6–31G** or larger basis sets. Electron correlation effects were estimated by second-order Moller-Plesset perturbation theory. The SCF geometries obtained are in good agreement with available experimental data with the exception of HNCS where the HNC bond angle differs by 10°. In all cases the experimentally known isomer is the one predicted to be thermodynamically more stable and the Koopmans theorem ionization potentials substantiate earlier work.

Photoelectron spectroscopic detection of vinyl alcohol, CH2CHOH: evidence for the syn and anti rotamers

Abstract Vinyl alcohol, CH 2 CHOH, has been produced by thermolysis of ethylene glycol, HOCH 2 CH 2 OH, and the photoelectron spectrum measured. The region of the first band shows evidence of an underlying, weaker, second component. This is to be expected if two rotameric forms ( syn - and ( anti -vinyl alcohol) are present. On this basis the first adiabatic ionisation energies are assigned as9.30eV ( syn ) and 9.17eV ( anti ). The band assignments are discussed with the aid of ab initio SCF calculations which indicate that the first band is due to excitation of an electron from the π molecular orbital which is essentially antibonding between the oxygen atom and the vinyl group.

Photoelectron spectra of the phospha-alkynes: 3,3-dimethyl-1-phosphabutyne ButCP and phenylphosphaethyne, PhCP

He(I) photoelectron spectra of the phospha-alkynes ButCP and PhCP have been obtained. The spectra have been assigned by comparison with spectra of related species and with the aid of ab initio SCF molecular orbital calculations. The first ionisation potentials are 9.61 and 8.68 eV for ButCP and PhCP respectively. These correspond to electron removal from orbitals with essentially π(CP) bonding character.

The ultraviolet photoelectron spectra of the chlorobenzenes and chloropyridines

Abstract The photoelectron spectra of the chlorobenzenes and chloropyridines have been measured, and a classification of the bands has been made on the basis of perturbations to the states of a six-membered ring by Cl and N. An atom-additive model is found to correlate the shifts of the π and n states of pyridine by Cl, but the correlation is not as good as for the shifts by F studied in an earlier paper.

The photoelectron spectra of the perfluorodiazines

Abstract The photoelectron spectra of the three isomeric tetrafluorodiazines have been measured and assigned. Independent support for the assignment is provided by published ESCA data.

Spectroscopic studies of thiazyl bromide, NSBr

Abstract The He(I) photoelectron and low resolution infrared spectra of thiazyl bromide have been recorded. A new route to this elusive molecule has been developed using thiazyl chloride as the precursor. The first ionisation energy of thiazyl bromide, predicted to arise from excitation of an essentially non-bonded electron localised mainly on the nitrogen and bromine atoms, occurs at 10.45 eV, in good agreement with ab initio SCF calculations. The gas phase Fourier transform infrared spectrum of the new molecule shows a strong band at 1311 cm −1 , the v 1 N-S stretching fundamental. Calculations have also been carried out on thiazyl fluoride and thiazyl chloride.

The He(I) and He(II) photoelectron spectra of bis (2,4,6-tri-t-butylphenyl)-diphosphene

Abstract Photoelectron spectra of the title compound have been obtained using various ionising radiations. The bands up to ∼10 eV have been assigned with the aid of molecular-orbital calculations.

UV photoelectron spectra of [RH2X2L4], (X = Cl, Br, I), (L = CO, PF3) and Ir2Cl2(PF3)4

Abstract He(I) photoelectron spectra of [Rh 2 Br 2 (CO) 4 ], [Rh 2 X 2 (PF 3 ) 4 ] (X = Br, I) and [Ir 2 Cl 2 (PF 3 ) 4 ] are presented and discussed in relation to those of Rh 2 Cl 2 L 4 ] (L = CO, PF 3 ). The He(I) spectrum of Rh 2 Cl 2 (PF 3 ) 4 ] confirms band assignments made from the He(I) spectrum. UV spectroscopic data for [M 2 Cl 2 (PF 3 ) 4 ] (M = Rh, Ir) are compared with other literature data for d 8 metal complexes

A study of the molecular and electronic structure of iron(II)and ruthenium(II) 1,3-di- and 1,2,4-tri-phospholyl sandwich compoundsby photoelectron spectroscopy and density functional theory

The synthesis and variable temperature 1H NMR spectrum of the new tetraphosphaferrocene [Fe(η5-P2C3Bu3t)2] are presented and the photoelectron spectra are reported for [Fe(η5-P3C2Bu2t)2] 1a, [Fe(η5-P2C3Bu3t)2] 2a, [Fe(η5-P2C3Bu3t)(η5-P3C2Bu2t)] 3a and [Ru(η5-P3C2Bu3t)2] 4a. Density functional calculations were used to optimise the geometry and calculate the ionization energies of the parent analogues. Good agreement was obtained with the experimental results, giving support to the theoretical modelling of these sandwich compounds. Analysis of their electronic structure showed that replacement of RC fragments by P atoms in the η5-ligated cyclopentadienyl rings increases their acceptor properties. Extensive σπ mixing makes the description of the orbitals complex. Some higher lying Pσ levels are found to have similar ionization energies to the d electrons.

The production and photoelectron spectrum of thiazyl iodide. NSI

Abstract The previously unknown molecule thiazyl iodide, NSI, has been prepared and studied by HeI photoelectron and low-resolution infrared spectroscopy. It has been produced by an on-line process using thiazyl chloride, NSCl, as precursor. The observed photoelectron spectrum has been rationalised using ab initio molecular-orbital calculations. The first ionisation energy is 10.06±0.05 eV, assigned to a largely non-bonding orbital with major components on nitrogen and iodine. Gas-phase infrared spectra yield a value for ν 1 of 1295 cm −1 .