Synthesis and characterization of chiral polymer complexes incorporating polybinaphthyls, bipyridine, and Eu(III)

Abstract

Chiral conjugated polymers P-1 and P-2 were synthesized by the polymerization of (S)-3,3 0 -diiodo-2,2 0 -bisbutoxy-1,1 0 -binaphthyl and (S)-6,6 0 -dibromo-2,2 0bisbutoxy-1,1 0 -binaphthyl, respectively, with 5,5 0 -divinyl-2,2 0 -bipyridine through a Heck cross-coupling reaction. Chiral polymer complexes P-C-1 and P-C-2 were obtained by the bipyridine chelating coordination of P-1 and P-2 with Eu(TTA) 3 Á2H 2 O (where TTA is 2-thenoyltrifluoroacetonate). Polymers P-1 and P-2 and polymer complexes P-C-1 and P-C-2 exhibited intense circular dichroism signals, with negative and positive Cotton effects in their circular dichroism spectra. The chiral polymers showed strong green-blue fluorescence because of the efficient energy migration from the extended p-electronic structure of the conjugated polymer main to the chiral binaphthyl core. The chiral polymer complexes could have not only polymer fluorescence but also the characteristic fluorescence of Eu(III) ( 5 D 0 ? 7 F 2 ) at a different excited wavelength. These kinds of chiral polymer complexes incorporating polybinaphthyls, bipyridine, and Eu(III) moieties are expected to provide an understanding of the relationship between the structure and properties of chiral polymer complexes. Scheme 3. Synthesis procedures for P-1, P-2, P-C-1, and P-C-2. 654 CHENG ET AL.

A Fluorescent Chemosensor for Transition‐Metal Ions Based on Optically Active Polybinaphthyl and 2,2′‐Bipyridine

“…Syntheses and Features of the Monomers and Polymer 4-methylphenylboronic acid was synthesized according to the literature, [43][44][45] and 5,5 0 -divinyl-2,2 0 -bipyridine (M-1) was prepared as has been reported previously [38,46,47] (Scheme 1). R-M-2 was synthesized from (R)-BINOL by a six-step reaction (Scheme 2).…”

“…Instead of the Wittig method, the Heck synthetic route was used for the preparation of the chiral polymers because the Heck reaction directly produced the desired polymers in the trans configuration. [10,37,38,[65][66][67][68][69] The gel-permeation chromatography (GPC) result for the polymer shows a moderate molecular weight. The octoxy and 4-methylphenyl group substituents on binaphthyl rings as side-chains of the polymer can not only improve the solubility in common organic solvents, but also modify the electronic properties and conjugated structure of the chiral polymer.…”

“…Herein, 5,5 0 -divinyl-2,2 0 -bipyridine, as a conjugated molecular linker unit and recognition binding site of the fluorescent chemosensor was introduced into the mainchain backbone of chiral polybinaphthyls to maintain conjugation between bipyridine and naphthyl segments so that the electron-transporting properties of the polymer may be improved and the electron density may shift away via the vinylene bridge, which could also increase the stability of the resulting chiral polymer. [25,[37][38][39][40][41][42] This kind of chiral conjugated polymer has a strong green-blue fluorescence. Moreover, this neutral ligand bipyridine can directly coordinate with different transition-metal ions to form polymer complexes.…”

Polymers that Contain Ligated Metals in their Side Chain: Building a Foundation for Functional Materials in Opto‐Electronic Applications with an Emphasis on Lanthanide Ions

“…Vinylpyridine N-oxides, vinyl pyridines, acrylic acids, b-diketonates, Schiff bases, and other ligands have been explored. [42][43][44][45][46][47][48][49][50] Fraser built polymers that contained Eu III at the center of star block copolymers based on PCL and poly(DL-lactide). [53] Morphology and emission studies indicated that the metal center was localized to the microphase separated interface between the two dissimilar blocks.…”

“…[42][43][44][45][46][47][48][49][50] For example, lanthanide-doped materials find use in many modern devices including cathode ray tubes, projection televisions, fluorescent tubes, X-ray detectors, tunable UV and visible lasers, light-emitting diodes (LEDs), low-energy scintillators, amplifiers for optical communication, optical storage, fluoroimmunoassays, and light concentrators in photovoltaics devices. Unlike their transition metal relatives, which typically have broad emission bands, lanthanides ions emit from their f-f transitions, which are shielded from the coordination environment and are thus much less sensitive to vibrational coupling.…”