Bis-isatin based polymers with tunable energy levels for organic field-effect transistor applications

Bis-isatin based monomers with elongated pi-conjugation have been synthesized. The main conjugation pathways of the new monomers included eighteen sp(2) hybridized carbons. The Z configuration of the double bond in the 3-(thiophen-2-ylmethylene)indolin-2-one moiety was assigned directly by crystal structure analysis. Single-crystal X-ray diffraction analysis also revealed that the extended planar structure in the monomer BTEI-C8 was facilitated by through-space intramolecular interactions. The planar structure and dipole interactions enabled close intermolecular packing of BTEI-C8 in the solid state. Two new pi-conjugated polymers were also synthesized, and their HOMO/LUMO energy levels can be adjusted by cyano substitutions on the vinyl linkers. The OFET devices based on the polymers showed p-type or ambipolar charge transport properties.