Joseph A. Hashmall

Gas phase and solid state X-ray photoelectron spectra of the substituted acetylenes (SF5)n C2 (CF3)2−n (n = 0, 1, 2): A comparison of the pentafluorosulfur and trifluoromethyl groups

Abstract The core level X-ray photoelectron spectra (XPS) of CF 3 CCCF 3 , CF 3 CCSF 5 and SF 5 CCSF 5 have been measured in the solid state. Gas phase spectra of CF 3 CCCF 3 and CF 3 CCSF 5 have also been obtained. The XPS data, interpreted with the point charge potential model and semiempirical MNDO (minimum neglect of differential overlap) molecular orbital calculations, indicate that the electron withdrawing effect of the −CF 3 group is greater than that of the −SF 5 group. Results further suggest that sulfur 3 d orbitals do not play a detectable role in the bonding or charge distribution in these molecules. Carbon 1 s linewidths of −CF 3 carbon atoms are found to be much narrower than those arising from the acetylenic carbon atoms. The narrower lines correlate with the much higher binding energy of the −CF 3 carbon atoms. Large shifts (nearly 1 eV) in heteroatom core level binding energy differences (for example, F 1 s — C 1 s ) between the gas phase and solid state data are observed. These shifts are attributed to solid state effects (Madelung potential, intermolecular bonding interactions, and/or extramolecular relaxation contributions). From these comparisons it is clear that solid state effects are not uniform in their influence on the photoionized sites in these molecules.

Useful chemical information obtained by use of common counterions as internal calibrants in X-ray photo-electron spectra of inorganic complex ions

Abstract It is shown that the accuracy and precision, and hence the value for bonding-structure studies, in relative binding energy measurements can be enhanced if a common counterion is employed. The differences in chemical shifts between the peaks for the atoms under consideration and for a common counterion in twenty-nine compounds are measured. This technique reduces charging effect errors, which otherwise often occur when non-conducting samples (e.g., salts) are measured relative to a traditional external calibrant. The improvements in accuracy and precision are demonstrated by using the cesium salt of twenty-nine heteropoly and isopoly anions in more than seventy-five different runs. Oxygen 1 s , tungsten 4 d , and molybdenum 3 d binding energies are measured relative to the cesium 3 d ionization potential. In this work the cesium counterion is assumed to be chemically invariant. For the relative binding energies that are studied, no dependence on the charge of the anion is observed. A linear relation seems to exist between the oxygen Is binding energies (measured relative to Cs) and the oxygen-to-tungsten ratio in five isopoly anions. This latter finding may serve as a useful aid in studies related to the synthesis of new compounds.

The application of gas phase and solid state X-ray photoelectron spectroscopy to the investigation of derivatives containing the repeating SN unit☆

Abstract Solid state X-ray photoelectron spectra of S 2 N 2 , S 4 N 4 , (SNBr 0.04 ) x , and (SNBr 0.25 ) x have been obtained and the gas phase spectrum of S 2 N 2 is also reported. Both the solid state and gas phase core level spectra, as well as MNDO and CHELEQ calculations, show that there is greater S → N charge transfer in S 4 N 4 than in S 2 N 2 . The solid state data indicate that the charge distributions in S 2 N 2 and (SN) x are the same. All of the data can be satisfactorily explained without recourse to N p π → S d π bonding. Bromination of an (SN) x film and single crystals results in complicated, broad N 1s and S 2p envelopes. Changes in the relative core level intensities on bromination suggest that the bromine resides largely between and/or on the (SN) x fibrils, rather than penetrating into the fibrils.

Method of rapidly optimizing bond lengths in all‐valence electron SCF‐MO calculations

A method for rapidly finding the bond lengths for which all‐valence electron SCF‐MO methods will give energy minima is presented. The necessary constants for application of this method to MINDO/2 calculations are given and its general utility tested. The results are in excellent agreement with the energies and bond lengths found from true geometry optimization, but require only a fraction of the time.