New soluble, coplanar poly(naphthalene-2,6-diyl)-type π-conjugated polymer, poly(pyrimido[5,4-d]pyrimidine-2,6-diyl), with nitrogen atoms at all of the o-positions.: Synthesis, solid structure, optical properties, self-assembling phenomena, and redox behavior

New n-type pi-conjugated poly(pyrimido[5,4-d]pyrimidine-2,6-diyl)s with a poly(naphthalene-2,6-diyl)-type structure and alkylamino substituents were prepared by dehalogenative polycondensation using a zerovalent nickel complex in 90-98% yield. The polymer is considered to have a coplanar pi-conjugated main chain and a strong tendency to form a pi-stacked structure, as judged from its CPK molecular model, UV-vis data, photoluminescence data, and XRD data. The obtained polymers were soluble in organic solvents and a polymer with N-octylamino substituents showed a number-average molecular weight, M-n, of about 8000 in GPC analysis. Other polymers showed analogous Mn values. The LTV-vis spectra of the polymers gave a main absorption peak at about 450 nm, which was shifted by about 130 nm to a longer wavelength compared to those of corresponding monomeric compounds. The degree of the red shift was larger than those observed with other analogous poly(naphthalene-2,6-diyl)-type pi-conjugated polymers, and the large red shift was attributed to the coplanar structure of the polymer. UV-vis and photoluminescence data revealed a strong tendency for the polymer to form a self-assembled structure. Powder X-ray diffraction analysis indicated that the polymers took an end-to-end packing mode. Electrochemical reduction (or n-doping) of the polymers proceeded with an E., of about -2.3 V vs Ag+/Ag.