Synthesis and Characterization of Polybinaphthyls Incorporating Chiral (R) or (S)-2,2′-Binaphthyl Entities by Heck Reaction

Abstract

ABSTRACT:Four chiral conjugated polymer-1 (P-1), polymer-2 (P-2), polymer-3 (P-3) and polymer-4 (P-4) were obtained by the polymerization of (S)-6,60 -dibromo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl ((S)-M-1) and (R)-6,6 0 -dibromo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl ((R)-M-1) with 1,4-divinyl-2,5-dibutoxybenzene (M-2) and 1,3,4-oxadiazole-2,5- 1-4 (R) or (S)-1,1 0 -binaphthol (BINOL) have often been used as the starting materials for obtaining chiral binaphthyl compounds. The 2,2 0 -hydroxyl groups of BINOL can be easily converted into other functional groups and the 3,3 0 -and 6,6 0 -positions of binaphthyl skeletal structure of BINOL can be selectively functionalized at the well-defined molecular level, leading to a variety of binaphthyl derivatives which can exhibit remarkably stable chiral configuration as well as high chiral induction in molecular recognition, 5-9 asymmetric processes.10-15 These rigid and sterically chiral polybinaphthyl polymers also represent a new generation of materials for applications in chiral sensors, polarized light emission and nonlinear optical materials. [16][17][18][19][20] Conjugated polymers with rigid -systems often possess poor solubility, which seriously inhibits full structural elucidations and property investigations. We choose M-2 and M-3 as the conjugated molecular bridge linkers. Oxadiazole derivatives have been widely used as electron transporting/hole blocking materials in LED devices and LED blends because oxadiazole unit has many excellent properties on the better chromophore, high thermal and oxidative stability, and the good charge injection and transporting building blocks. [21][22][23] In our paper, M-3, 1,3,4-oxadiazole-2,5-bis(4-vinylbenzene) is introduced into the chiral polymers main chain backbone to maintain conjugation between the oxadiazole and binaphthyl segments so that the electron transporting properties of the polymers may be improved. In addition, by introducing oxadiazole, an electron deficient moiety into the main chain, the electron density may shift away from the vinyl bond, which could increase the stability of the resulting chiral polymers. 24,25 To make soluble conjugated polymers, the alkyl groups substitutents on the phenyl and binaphthyl rings as side chain of the polymers can improve solubility in organic solvents and facile electro-optical sensors. Heck, Suzuki, Stille and Sonogashira reactions are the most important C-C coupling reactions in organic chemistry synthesis. Herein, we present preliminary results of synthesis and properties of four polymers based on the chiral unit 1,1 0 -binaphthyl structure. The four chiral polymers containing vinylene linkages between naphthyl and phenyl groups can reduce steric hindrance between backbone rings and groups, and also have a beneficial effect on delocalizable -electronic conjugation structure of polymers. These polymers are green-blue light emitting materials with very good fluorescence quantum efficiencies. EXPERIMENTAL General1 H, 13 C NMR spectra measurements (all in CDCl 3 ) were recorded...

Polybinaphthyls incorporating chiral 2,2′-binaphthyl and isoquinoline moieties by Sonogashira reaction

“…Pu synthesized a series of chiral conjugated polymers incorporating polybinaphthyls into the main chain and compared their UV absorption wavelengths of the polymers with their corresponding repeating units, and found that there is almost no extended conjugation across the 1,1 0 -bond of the binaphthyl units in the backbone of polybinaphthyl [9,40,41]. In this paper, a large red-shift in the electronic absorptions of the conjugated polymers can be attributed to the effective pep* conjugated segment of the linker conjugated unit M-1 and naphthyl group in the repeating unit of polybinaphthyls' main chain [14,15,42,43].…”

“…The [14,15] and that of the chiral center units (R)-and (S)-2,2 0 -bisbutoxy-1,1 0 -binaphthyl are þ57.8 and À57.2, but [a] D 25 of their conjugated polymers P-1, P-2, P-3 and P-4 are À788, þ822, À165 and þ148, respectively. The absolute values of the special rotation ([a] D 25 ) of the four polymers are larger than their corresponding monomers and the chiral center units (R)-or (S)-2,2 0 -bisbutoxy-1,1 0 -binaphthyl.…”

“…(R)-3,3 0 -Diiodo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl ((R)-M-2) and (S)-3,3 0 -diiodo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl ((S)-M-2) were synthesized according to literature [15]. (R)-6,6 0 -Dibromo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl ((R)-M-3), (S)-6,6 0 -dibromo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl ((S)-M-3) and (rac)-6,6 0 -dibromo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl (M-4) were synthesized according to literature[14].…”

Synthesis and Fluorescent Properties of Chiral Polymer Complexes Incorporating Bipyridine and Eu(III) or Gd(III)

“…41,42 Compared to the Wittig method, the Pd-catalyzed Heck polycondensation is relatively mild and gives an easy access to various monomers in the preparation of functionalized PPV. 10,27,[43][44][45] In this paper, a typical Heck reaction condition was applied to the polymerization. The C-C cross coupling process was easily carried out in DMF in the presence of a catalytic amount (5 mol%) of Pd(OAc) 2 with Et 3 N and triphenylphosphine (PPh 3 ) under a N 2 atmosphere.…”

Designed synthesis and chiroptical properties of regioregular poly(p-phenyleneethynylene-alter-m-phenyleneethynylene) bearing (−)-trans-myrtanoxyl side groups

“…The reported chiral conjugated polymers can be divided into two groups: (1) Main chain chiral conjugated polymers, mainly conjugated polymers containing chiral binaphthylene moieties [9][10][11][12][13][14];…”