Effect of substituents on ionization potentials of phosphorus compounds. Conjugation in radical cations

Abstract

The first vertical ionization potentials (I) of phosphorus compounds P(Xi)3, OP(Xi)3, SP(Xi)3, (4-XC6H4)3P, and P≡CX are related to the inductive, resonance, and polarizability parameters of inorganic, organic, and organometallic substituents X by dependences of the type I = I H + aΣσI + bΣσR + + cΣσα, where I H is the I value for X = H. The I values are also affected by hyperconjugation. The ratio of the contributions of the resonance (bΣσR +) and polarizability (cΣσα) effects to the I value is determined by the degree of delocalization of the unpaired electron and the positive charge in the radical cations formed upon ionization of neutral molecules. The σR + resonance parameters of organosilicon, organogermanium, and organotin substituents bound to the P ·+ radical cation center were calculated for the first time.