Synthesis of rigid pi-conjugated mono-, bis-, tris-, and tetrakis(terpyridine)s: influence of the degree and pattern of substitution on the photophysical properties

A series of rigid pi-conjugated mono-, bis-, tris-, and tetrakis(terpyridine)s 3-8 was synthesized in high yields by means of Horner-Wadsworth-Emmons (HWE) reactions between benzyl phosphonates 1 and an aldehyde-functionalized terpyridine deriv. 2. The photophys. properties of the materials in soln. and in the solid state depend strongly both on the nos. of terpyridine moieties attached to the central Ph cores and on the geometries of the compds. The photophys. behavior of the ortho-substituted compds. 5 and 8 indicated significant changes in the geometries, together with major extensions of the effective pi-conjugated systems upon excitation. Bright green emission with high quantum yields was obsd. for the tetrakis(terpyridine) deriv. 8. [on SciFinder (R)]