Synthesis of side-chain regioregular and main-chain alternating poly(bichalcogenophene)s and an ABC-type periodic poly(terchalcogenophene)

Three unsymmetrical diiodobichalcogenophenes SSeI2, STeI2, and SeTeI2 and a diiodoterchalcogenophene SSeTeI2 were prepared. Grignard metathesis of SSeI2, STeI2, SeTeI2, and SSeTeI2 occurred regioselectively at the lighter chalcogenophene site because of its relatively lower electron density and less steric bulk. Nickel-catalyzed Kumada catalyst-transfer polycondensation of these Mg species provided a new class of side-chain regioregular and main-chain AB-type alternating poly(bichalcogenophene)s—PSSe, PSTe, and PSeTe—through a chain-growth mechanism. The ring-walking of the Ni catalyst from the lighter to the heavier chalcogenophene facilitated subsequent oxidative addition, thereby suppressing the possibility of chain-transfer or chain-termination. More significantly, the Ni catalyst could walk over the distance of three rings (ca. 1 nm)—from a thiophene unit via a selenophene unit to a tellurophene unit—to form PSSeTe, the first ABC-type regioregular and periodic poly(terchalcogenophene) comprising three different types of 3-hexylchalcogenophenes.


S3
prepared form 20 mg/mL solutions in chloroform and were spin-coated on the ODTStreated silicon wafers. The gold source and drain electrodes (40 nm in thickness) were then deposited on the organic layer by vacuum evaporation through a shadow mask, affording a bottom-gate, top-contact device configuration. OFET measurement was carried out at room temperature under a nitrogen atmosphere using an Agilent Technologies 4156C instrument. The mobility calculation was based on the equation I ds (W/2L)μCi(Vg -Vt) 2 in the saturation regime, where I ds is the drain-source current, W is the channel width (1 mm), L is the channel length (100 mm), μ is the field-effect mobility, Ci is the capacitance per unit area of the dielectric layer, V g is the gate voltage, and V t is the threshold voltage.
The organic layer was collected and dried with MgSO 4 . After removal of the solvent under reduced pressure, the residue was purified by silica gel chromatography with hexane as the eluent to give a brown oil (

Procedure for M n versus Monomer Conversion Plot
To a solution of isopropylmagnesium chloride lithium chloride complex (

DFT Computation and Analysis
Computational details.
Quantum-chemical calculations were performed with the Gaussian09 suite employing the cam-B3LYP density functional in combination with the LANL2DZ(d,P) basis set for the chalcogens, phosphine, and iodine, the LANL2DZ basis set for nickel, and the 6-311G(d,p) basis set for the remaining atoms. Geometry optimizations were performed with tight SCF and convergence criteria and an ultrafine integration grid, applying the GEDIIS optimization algorithm. The nature of each stationary point was confirmed by a frequency analysis.