Synthesis of Platinum-Containing Conjugated Polymers Bearing Optically Active Amide Groups: A Mechanistic Study of Chiral Aggregation

Chirally regulated π-conjugated polymers containing platinum (Pt) complex moieties have great potential as chiroptically functional materials. In this study, novel platinum-containing conjugated polymers, poly­(1a-2) and poly­(1b-2), were synthesized by the dehydrochlorination coupling polymerization of dichloro­(4,4′-tert-butyl-2,2′-bipyridyl)­platinum (1a) and dichloro­(4,4′-dinonyl-2,2′-bipyridyl)­platinum (1b) with N-[3,5-bis­(4-ethynylphenylethynyl)­benzoyl]-l-alanine dodecylamide (2), and their chiral secondary structures in solutions were investigated. Poly­(1a-2) exhibited bisignate circular dichroism (CD) signals assignable to the main chain chromophore (300–450 nm) in dimethylformamide (DMF)/MeOH = 50/50 (v/v). The presence of particles of Z-average = 30 nm was confirmed in this solution. These results indicated that poly­(1a-2) formed chirally regulated aggregates. Single-crystal X-ray analysis of the model compound and density functional theory (DFT) calculations were carried out to examine the mode of aggregation of the polymers.