A fresh look at participation of phosphorus atom in conjugation

GRAPHICAL ABSTRACT

ABSTRACT

The strength of conjugation between the lone pair on phosphorus atom and aryl, alkenyl and styryl moieties of several phosphines has been quantitatively characterized by the use of Raman intensities of the bands of the above-mentioned substituents. It is shown that conjugation in the phosphines produces an intensification of Raman bands and a simultaneous bathochromic shift of the electronic absorption spectra for all the phosphines, except of phenylphosphine PhPH₂, where the lone pair on P^III does not conjugate with phenyl moiety. Nevertheless, the lone pair is able to conjugation within more expanded aromatic π-systems, and the conjugational effects are strongly enhanced as π-system of arylphosphines expands.

KEYWORDS:

• Conjugation
• Raman spectra
• UV absorption spectra
• DFT calculations

Acknowledgments

The authors are indebted to all staff members of the Supercomputer Centre of the Kazan Scientific Centre of the Russian Academy of Sciences and especially to Dr. D. Chachkov for technical assistance in these computations.

Funding

This work was supported by the Russian Foundation for Basic Research (grant 14-03-00920 a).