Regioselective grignard metathesis reaction of 2,5‐dibromo‐3‐(6′‐hexylpyridine‐2′‐yl)thiophene and kumada coupling polymerization

Abstract

2,5‐Dibromo‐3‐(6′‐hexylpyridine‐2′‐yl)thiophene (DBPyTh) was synthesized by the Suzuki coupling reaction between two aromatic compounds followed by the bromination. The Grignard metathesis reaction of DBPyTh with isopropylmagnesium chloride proceeded in 85% conversion and the regioselective halogen–metal exchange at the 2‐position was confirmed. Namely, 5‐bromo‐2‐chloromagnesio‐3‐(6′‐hexylpyridine‐2′‐yl)thiophene and 2‐bromo‐5‐chloromagnesio‐3‐(6′‐hexylpyridine‐2′‐yl)thiophene were generated in 90:10 molar ratio. Subsequently, the Kumada coupling polymerization was carried out using 1,3‐bis(diphenylphosphinopropane)nickel(II) dichloride to obtain poly(3‐(6′‐hexylpyridine‐2′‐yl)thiophene) (PolyPyTh). The polymer molecular weight could be roughly controlled by the catalyst concentration and the molecular weight distribution ranged from 1.25 to 1.80. The gas chromatograph analysis indicated that 5‐bromo‐2‐chloromagnesio‐3‐(6′‐hexylpyridine‐2′‐yl)thiophene was preferentially polymerized in 90% conversion and the percentage of the head‐to‐tail content (regioregularity) was calculated to be 96%. The matrix‐assisted laser desorption/ionization time‐of‐fright mass spectrum indicated that both polymer chain ends were substituted with the hydrogen atom. The absorption maxima of polymer in CHCl3 and thin film were observed at 447 and 457 nm, respectively, which were blue‐shifted compared with poly(3‐(4′‐octylphenyl)thiophene). From the CV measurement of the polymer thin film, highest occupied molecular orbital (HOMO) (−5.31 eV) and lowest unoccupied molecular orbital (LUMO) (−3.76 eV) energy levels were calculated from the oxidation and reduction onset potentials, respectively, and the electrochemical band gap energy was determined to be 1.62 eV. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Effectiveness of alternating mammography and magnetic resonance imaging for screening women with deleterious BRCA mutations at high risk of breast cancer

“…Although electrochemical polymerization55 and many other polymerization methods, such as in‐situ polymerization,2 Stille coupling reaction,56, 57 transition metal‐mediated oxidative dispersion polymerization,58 Kumada coupling polymerization,59 ring‐opening metathesis polymerization,60 and so forth, have been developed to prepare polythiophenes including PEDOT and its analogs, chemical oxidative polymerization is still the most important and irreplaceable way for large‐scale industrial applications until now. Therefore, herein, chemical oxidative polymerization of EDTT with oxidants was performed in different solvents.…”

Synthesis and characterization of polythiophene derivatives with nitrogen heterocycles on the side chain

“…The absorption maxima of poly M1 in solution (441 nm) and film (461 nm) states blue‐shifted as compared with those of poly(3‐hexylthiophene) having the peak maxima at 450 nm and 549 nm, respectively. The shift width from solution to film (20 nm) was remarkably small in the case of poly M1 ; however, this value was larger than that observed for poly M0 with the similar H–T content (10 nm) . The absorption maximum of poly M3 in solution (451 nm) and film (477 nm) states red‐shifted and those of poly M2 (475 nm and 521 nm, respectively) were observed at the longest wavelength region although these polymers have lower H–T content than poly M1 .…”

“…10(d) In the solution processed all‐polymer solar cell with the bilayer system using POPT and poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐(1‐cyanovinylene)phenylene] (CN‐PPV), the peak efficiency of 2% was achieved due to the increased short circuit current. We have recently explored a synthetic method to obtain regioregular poly(3‐(6′‐hexylpyridine‐2′‐yl)thiophene), poly M0 , having the pyridine ring at the side chain . The key point for success was the regioselective GRIM reaction using the intramolecular chelate coordination of the pyridine nitrogen to the magnesium center.…”

Aggregation of polythiophene homopolymer and block copolymer in solution utilizing the characteristics of pyridine at the side chain

“…The reaction occurred at the 2‐position in the 86% selectivity to give 5‐bromo‐2‐chloromagnesio‐3‐(5′‐hexylpyridine‐2′‐yl)thiophene. Subsequently, the Kumada coupling polymerization was carried out using Ni(dppp)Cl 2 (3 mol %) for 2 h to obtain a homopolymer ( P3PT ) having the number‐averaged molecular weight of 13,900 . Although 5‐bromo‐2‐chloromagnesio‐3‐(5′‐hexylpyridine‐2′‐yl)thiophene has the bulky substituent at the ortho position relative to the chloromagnesio group and is regarded as the reverse monomer, the polymerization smoothly proceeded at the refluxing temperature probably due to the chelation effect of the pyridine nitrogen .…”