Photoelectron spectroscopy substituent effects

Theoretical methods are surveyed, followed by data on molecular dimensions obtained from X-ray diffraction or microwave spectroscopy. The various types of NMR spectroscopic characteristics are then surveyed, including H, 13C and nitrogen NMR spectroscopy. This is followed by a discussion of UV and visible and then IR, mass and photoelectron spectroscopy. Each of the spectroscopic sections deals with both the various parent rings and the effect of substituents. 

The energy levels of the HOMO s are known from photoelectron spectroscopy, those of the LUMO s are estimated from electron affinities, substituent effects on charge transfer spectra, polarographic reduction potentials, and electron (tt—tt ) absorption spectraTypical values are suirunarized in Table 3. The energies of the HOMO S of substituted ethylenes are higher for +1 and —I substituents, but lower for -I substituents, in comparison with ethylene itself. The LUMO s appear to be generally lower for substituted ethylenes, but more so for —I" substituents. 

Gasteiger, J., Hutchings, M. G. New Empirical Models of Substituent Polaiisability and Their Application to Stablisation Effects in Positively Charged Species . Tetrahedron Lett. 1983,24, 2537-2540. Gasteiger, J., Hutchings, M. G. Quantification of Effective Polarisability. Applications to Studies of X-ray Photoelectron Spectroscopy and Alkylamine Protonation . J. Chem. Soc. Perkin Trans. 2, 1984, 559-564. 

Buchwalter, LP Silverman, BD Witt, L. X-ray photoelectron spectroscopy analysis of hexafluorodianhydride-oxydiamiline polyimide Substantiation for substituent effects on aromatic carbon Is binding energies. Journal of Vacuum Science and Technology A, 1987, 5, 226-230. 

MePhSNuc then undergoes further rapid reaction with a second mole of nucleophile. A correlation between the nucleophilic reactivity of a series of compounds containing the C=S group and the ionization potentials of the lone-pair electrons on the sulphur, as determined by photoelectron spectroscopy, has been reported. The effect of substituents on the reactivity of the thiophenoxide ion closely parallels the effect on their basicities. ... 

Coates M, Nyokong T (2013) X-ray photoelectron spectroscopy analysis of the effect of aUcyl-andarylthio substituents on manganese phthalocyanines for self-assembled monolayer formation on gold. Electrochem Common 31 104-107... 

Fundamental information on bonding is provided by photoelectron spectroscopy of thioanisoles and other alkyl aryl sulphides. Two conformers are predominant for these compounds, RSPh, and the proportion of the conformer with maximum overlap decreases through the series R = H, Me, Et, Pr or Bu. Related studies for sulphoxides provide correlation diagrams for the effects of substituents R in RS(0)R, as well as information on preferred conformations. An orienting survey of hexavalent sulphur functional groups, viz. alkyl, vinyl, and aryl sulphones, S -dialkyl sulphimides, sulphuryl halides, sulphoximides, and sulphurdi-imides, is available. ... 

Block et al.194 examined the effects of trimethylsilyl substitution on the first vertical ionization potentials by photoelectron and Penning ionization electron spectroscopy studies of a range of cyclic and noncyclic sulfides and ethers. It was shown that substitution of oxirane 218 with a trimethylsilyl substituent as in 219 lowered the ionization potential by 0.90 eV (20.8 kcal/mol), while similar substitution of dimethyl ether 220 in 221 lowered the ionization potential by 0.64 eV (14.8 kcal/mol). By comparison, the effects of silyl substitution on sulfur lone-pair ionization potentials was found to be smaller thus the ionization potential of dimethyl sulfide 222 is lowered by 0.37 eV upon trimethylsilyl substitution in 223, and the trimethylsilyl-substituted thiirane 225 is lowered by 0.59 eV relative to thiirane 224. The raising of the energy of the sulfur lone-pair electrons in the thiirane 225 is also apparent from its UV spectrum, where there is a bathochromic shift in the absorption maximum compared to the parent 224. 

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