π-Conjugated poly(pyrimido[5,4-d]pyrimidine-2,6-diyl)s with two different alkylamino groups: Synthesis, chemical properties, and structure

New π-conjugated pyrimidopyrimidine polymers with two different alkylamino groups at C4 and C8 positions, PPympym(4-NH-n-C 8 H 17 -8-NHR) (R=n-C 4 H 9 , n-C 6 H 13 , n-C 12 H 25 , and n-C 16 H 33 ), were prepared by dehalogenation polycondensation using nickel zerovalent complex in high yield. The obtained polymers were partly soluble in organic solvents such as chloroform. A chloroform soluble part of PPympym(4-NH-n-C 8 H 17 -8-NH-n-C 16 H 33 ) showed a number-average molecular weight of about 3,000 in GPC analysis. UV-vis spectra of the polymers in CHCl 3 showed a π-π* absorption peak at about 450 nm, and the peak position shifted by 30 nm to a longer wavelength in film. The polymers showed photoluminescence both in solution and in film. Cast films of the polymers were electrochemically reduced at about -2.3 V vs. Ag + /Ag. XRD patterns of the polymers revealed the polymers took an end-to-end packed structure.