Allosteric regulation of organometallic catalysts could allow for greater control over reactions. We report an allosteric supramolecular structure in which a monometallic catalytic site has been buried in the middle layer of a triple-layer complex. Small molecules and elemental anions can open and close this complex and reversibly expose and conceal the catalytic center. The ring-opening polymerization of ε-caprolactone can be turned on by the in situ opening of the triple-layer complex and then completely turned off by reforming it through the abstraction of Cl(-), the allosteric effector agent, without appreciable loss of catalytic activity. This process can regulate the molecular weights of the resulting polymers.
Polycondensation via direct C–H arylation of thiophene
derivatives
gave thiophene- and bithiophene-based alternating copolymers in good
yields. The optimization of the reaction conditions was investigated
in terms of a catalytic system and reaction time. Under optimized
conditions, the polycondensation reaction of 3,3′,4,4′-tetramethylbithiophene
with 2,7-dibromo-9,9-dioctylfluorene gave poly[2,7-(9,9-dioctylfluorene)-alt-5,5′-(3,3′,4,4′-tetramethyl-2,2′-bithiophene)]
with a molecular weight of 31 800 in 91% yield. The polycondensation
reaction proceeded with 2 mol % of Pd(OAc)2 without the
addition of a phosphine ligand in a short reaction time (3 h). Six
kinds of π-conjugated polymers were synthesized by the polycondensation
reaction without the use of bifunctional organometallic reagents as
monomers.
Alternating conjugated polymers of ethylenedioxythiophene and fluorene are prepared using three different synthetic methods to investigate the effects of these synthetic methods on the purity, field‐effect transistor (FET) performance, and organic photovoltaic (OPV) performance of the polymer. In this study, microwave‐assisted direct arylation polycondensation is used to obtain a high‐purity, high‐molecular‐weight (147 kDa) polymer. This pure polymer exhibits a high FET hole mobility of 1.2 × 10−3 cm2 V−1 s−1 and high OPV performance with a power conversion efficiency of 4%, even though the polymer forms an amorphous film, which absorbs in a limited region of the spectrum.
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