Poly(1,10-phenanthroline-3,8-diyl) and its derivatives. Preparation, optical and electrochemical properties, solid structure, and their metal complexes

pi-Conjugated poly(1,10-phenanthroline-3,8-diyl), PPhen, and its 5,6-dialkoxy derivatives, PPhen(5,6-OR)s, have been synthesized by using an organometallic polycondensation with a zerovalent nickel complex. They had average molecular weights of 4300-6800. PPhen had a stiff structure, as revealed by a light scattering method, and exhibited a strong dichroism in UV-vis absorption and photoluminescence. PPhen(5,6-OR)s formed an end-to-end packing assembly assisted by the side chain crystallization of the OR groups. PPhen and PPhen(5,6-OR)s were susceptible to chemical and electrochemical reduction, and the reduced state showed certain stability toward oxygen in air. The pi-conjugated polymers underwent quantitative complex formation with [Ru(bpy)(2)](2+). Introduction of two more imine nitrogens in the repeating unit of PPhen enhanced much the electron accepting property of PPhen, and n-doping of the obtained polymer took place at E-pc of -1.38 V vs Ag+/Ag.