Synthesis of 2-Aryl-5-styrylphospholes: Promising Candidates for the Phosphole-Based NLO Chromophores

2-Aryl-1-phenyl-5-styrylphospholes were prepared in good yields in a one-pot procedure from the
corresponding 1,9-diarylnona-8-ene-1,6-diynes and dichloro(phenyl)phosphine via intermediary titanacyclopentadienes. According to the UV−vis absorption and fluorescence spectra of this class of compounds,
the optical properties of the phosphole−vinylene-bridged π-conjugated system have been revealed to
depend strongly on the electronic character of the terminal functionalities. In particular, the polarizability
at the excited-state has been found to be considerably greater than that in the ground state. High molecular
hyperpolarizabilities obtained for the push−pull type of 2-aryl-5-styrylphospholes in the hyper-Rayleigh
scattering measurements demonstrate the potential utility of the stilbene-type phosphole derivatives as a
new class of second-order NLO chromophores.