Tuning the optoelectronic and charge transport properties of 2,5-di(pyrimidin-5-yl)thieno[3,2-b]thiophene by oligocene end cores substitution

With the focus on tuning the charge transport and optoelectronic properties, various new derivatives were designed by substituting the oligocene moieties at end cores of 2,5-di(pyrimidin-5-yl)thieno[3,2-b]thiophene (Comp. 1). The end core substitution effect of benzene, naphthalene, anthracene, tetracene, pentacene and hexacene on Comp. 1 was comprehensively studied on the structure-property relationship, electro-optical properties, ionization potential (IP), electron affinity (EA) and hole/electron reorganization energies (lambda(h)/lambda(e)). The injection barrier was reduced by introducing the oligocene units at end cores. The substitution of anthracene, tetracene, pentacene and hexacene at end cores of Comp. 1 significantly minimized the polarization resulting smaller lambda(h) (Comp.1c - Comp.1f) than the referenced compound, i.e., pentacene. The smaller lambda(h) values are illuminating that newly designed derivatives might be superior/analogous to pentacene, i.e., frequently used hole transport material. The fluorescence spectra, dipole moment, IP, EA and lambda(h) values showed that targeted molecules would be not only good for organic light emitters but also efficient for organic semiconductors and photovoltaic devices.