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

Abstract

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.

End Functionalization of Polynorbornene with Platinum–Acetylide Complexes Utilizing a Cross-Metathesis Reaction

“…The UV–vis absorption spectrum of 4b was also simulated using B3LYP and M06 functionals, which predicted the λ max assignable to MLCT/LLCT of the Pt-complex chromophore at 410 and 430 nm, respectively (Figure S48), in good agreement with the observed value [430 nm; Figure b]. ωB97X-D seems to predict the λ max of Pt–acetylide complexes at wavelengths shorter than the observed values. , …”

“…ωB97X-D seems to predict the λ max of Pt−acetylide complexes at wavelengths shorter than the observed values. 54,55 The solution-state photoluminescence of poly(1a) and poly(1b) in CH 2 Cl 2 was examined by comparing with model compounds 4a and 4b in CH 2 Cl 2 , as well as mixtures of poly(1) + 4a and poly(1) + 4b in CH 2 Cl 2 . Consequently, poly(1a), 4a, and a mixture of poly(1a) + 4a only slightly luminesced (Figure S42) at room temperature in a manner similar to Ph−C�C− Pt(PBu 3 ) 2 −C�C−Ph.…”

Synthesis of Platinum-Containing Conjugated Polymers Bearing Chiral Phosphine Ligands. Study of Geometries and Intermolecular Interactions Leading to Aggregation

“…21 We have also synthesized geometrically cis-controlled Ptcontaining conjugated polymers from cis-Pt(bipyridine)Cl 2 monomers. 22,23 However, to our knowledge, no one has successfully synthesized geometrically cis-controlled [−C C−Pt(PR 3 ) 2 −CC−Ar−] n by the dehydrochlorination polymerization of cis-Pt(PR 3 ) 2 Cl 2 with H−CC−Ar−CC−H. Chiral phosphine ligands are widely used as metal complexes catalyzing asymmetric induction 24−29 and exhibiting biological activity.…”

“…On the other hand, geometrically cis-controlled Pt-containing conjugated oligomers and polymers have been synthesized from cis -(1,2-bis­(diphenylphosphino)­ethane)­dichloroplatinum­(II) [ cis -Pt­(PPh 2 –CH 2 CH 2 –PPh 2 )­Cl 2 ] , and cis -dichloroplatinum­(II) complex monomers bearing bipyridine ligands [ cis -Pt­(bipyridine)­Cl 2 ]. , We have synthesized geometrically cis-controlled Pt-containing conjugated polymers by the ligand exchange reaction of trans-geometrically controlled Pt-containing conjugated polymers with diphosphine ligands . We have also synthesized geometrically cis-controlled Pt-containing conjugated polymers from cis -Pt­(bipyridine)­Cl 2 monomers. , However, to our knowledge, no one has successfully synthesized geometrically cis-controlled [−CC–Pt­(PR 3 ) 2 –CC–Ar−] n by the dehydrochlorination polymerization of cis -Pt­(PR 3 ) 2 Cl 2 with H–CC–Ar–CC–H.…”

Control of Higher-Order Structures of Platinum-Containing Conjugated Polymers by Ligand Exchange Reactions: Chirality Transfer from Optically Active Ligands to Optically Inactive Polymers

“…Our group synthesized various platinum-containing photoluminescent poly­(aryleneethynylene)­s, whose conjugation length and emission wavelength were controlled by arylene units and phosphine ligands . We also synthesized platinum-containing poly­(aryleneethynylene)­s with regulated secondary structures, wherein the aggregated and folded structures were controlled by substituents, solvent, and temperature. − …”