Synthesis and Photocyclization of Conjugated Diselenophene Pyrrole-2,5-dione Based Monomers for Optoelectronics

Abstract

Imide-functionalized organic monomers and polymers are attractive in organic optoelectronic devices due to the strong electronwithdrawing ability of the carbonyl units. We report the synthesis of diselenophene−pyrrole-2,5-dione and diselenophene−phthalimide based homopolymers P1−P2 and their corresponding copolymers P3−P4. The effect of the chemical structure by having fused and nonfused diselenophene units, in the polymer backbone, on the physicochemical properties and device fabrication was investigated. The resulting homopolymers and copolymers exhibited small optical band gaps combined with the low-lying HOMO energy levels demonstrated their potential as semiconducting materials in organic field effect transistors. The morphological properties of the microstructure and packing characteristics of the polymer films were investigated by twodimensional grazing incidence wide-angle X-ray scattering (2D GIWAXS). The diffraction patterns of the as-cast and thermally annealed polymer films illustrate that by increasing the fused aromatic cycles in the polymer backbone has an effect on the polymer film crystallinity, which was confirmed by computational studies of the dihedral angle and bond lengths of the polymers.

Truncated conjugation in fused heterocycle-based conducting polymers: when greater planarity does not enhance conjugation

“…GIWAXS measurements previously published indicate that both as-cast polymer films were amorphous. 18 The similarity of the absorption maximum positions in both solution and film (Fig. S1 † ) – and the pronounced blue-shift compared to HPMI, even in solution – suggest an intrinsic origin to HPPI's larger optical band gap.…”

“…Both CPPI and CPMI are copolymers containing a benzodithiazole moiety in the monomer backbone, but still possess the same fused and unfused selenophene ring structures as HPPI and HPMI. 18 These two materials were fully characterised in similar fashion to HPPI and HPMI. As seen in Fig.…”

“…Establishing these relationships will be of upmost importance in the eld of organic electronics, for example explaining the low efficiency of HPPI transistors. 18 In addition, the rational elucidation of the large changes in electronic characteristics upon photochemical cyclisation reactions is of great interest in the eld of molecular photoswitches. [21][22][23]…”

“…1a ) for their use in organic transistors, where a fusing strategy was followed. 18 One polymer possesses two separate selenophene rings in its maleimide monomer unit (HPMI), whereas the selenophene rings are fused to create a rigid selenobenzene–maleimide moiety in the second polymer (HPPI) to induce greater backbone co-planarity. Intriguingly, the fused selenophene polymer (HPPI) led to a more blue-shifted absorbance than its unfused counterpart (HPMI), which is usually an indication of lower effective conjugation.…”

Organic memory devices and synaptic simulation based on indacenodithienothiophene (IDTT) copolymers with improved planarity

“…In the solution and in the solid state, all copolymers exhibited a main p-p* transition with two peaks due to strong intramolecular interactions. [27][28][29] The absorption maxima of the copolymers in solution are at 545 nm for P1, 548 nm for P2 and 610 nm for P3. In comparison, thin film absorption spectra of P1-P3 display a bathochromic red shift of 2, 15 and 22 nm for P1, P2 and P3, respectively.…”