X‐Ray determination of the effective charges on sulfur and phosphorus atoms in chemical compounds

Abstract

The dependencies of Ka non-empirical calculations with the ion charges. However, all the obtained relationships between the K a shifts and the atomic charges had two drawbacks: 1) they were untrue for the K a line

X‐Ray spectral determination of the effective charges on phosphorus, sulfur, and chlorine atoms in chemical compounds with a nonempirical charge scale

“…We think that this may be explained by the fact that the ratio between the AAK, value changing region and the experimental errors of AK, definition is one order of magnitude smaller for A = C1 than -0. 4 for A = S , P. Taking into consideration the errors of the CKa shift measurement, one can draw a conclusion that the qcl vs. AClK, dependences presented in Figures 2 and 3 are also satisfactory. Hence, the possibility of determining the effective charges on the different A atoms in single charge scales according to SCF ab initio calculations with three basis sets by using the experimental AK, shifts only has been achieved.…”

“…The other example of data obtained may be analysis of the dependence between the ionicities of the P = S and P-S bonds and central phosphorus atom K, line shifts. In our prior research [4], we investigated this dependence by using qs vs. ASK, relationships reported previously.…”

“…relationship between the experimental AK, shifts ( A = P, S , C1) and the effective A atom charges. The calculations of atomic charges were performed by the electronegativity equalization procedure [3,6] and by semiempirical quantum-chemical CNDO/S, CNDO/2, INDO, MIND0/3, and MNDO methods in the large series of model compounds [4,5]. By using all the previously mentioned semiempirical methods in the minimal basis set and CNDO/S in the extended basis set, we have found that the dependence was split into two linear relationships for the S and P atoms.…”

Geminal conjugation in disulfides

“…In organic disulfides, the n,-a" conjugation efficiency can be studied by X-ray fluorescence spectroscopy. This method offers possibilities to define both the effective charge on the sulfur atom (q,), which is proportional to the SK, line shift (ASK,) [58,59], and the HOMO bonding degree with the help of SK, spectra and internal standard technique [60,61] CH,CH=CH, (25), CH,Ph (14), and S , (26) have been investigated. The SK, spectra obtained are presented in Figure 4.…”

“…The SK, spectra were repeated 16-20 times and the SK, spectra 3-5 times and the results averaged by the technique described in reference [58].…”