Two series of 2.5-dipyridyl and 2.5-dithienylphosphole derivatives containi
ng sigma (3)- or sigma (4)-P atoms were prepared. and their optical (UV/Vis
absorption, fluorescence spectra) and electrochemical properties were syst
ematically evaluated. These physical properties depend mainly on the nature
s of the 2.5-substituents and of the phosphorus moiety, and they revealed t
hat these compounds contain extended pi- conjugated systems. Structure -pro
perty relationships were established on the basis of these experimental dat
a and ab initio calculations on the parent molecules. The limited aromatic
character and low-lying LUMO of the phosphole ring appear to be crucial for
achieving a highly delocalised pi system. Electrooxidation of 2,5-dithieny
lphosphole derivatives affords electroactive films with low optical band ga
ps. As observed for the corresponding monomers, the optical and electrochem
ical properties of the polymers can be varied over a wide range by modifyin
g the nature of the phosphorus moiety.