Design And Theoretical Studies On Properties Of Silicon-bridged Acene π-conjugated Molecules

The special structure of silicon-bridged acene containing ladder π-conjugatedmolecules makes them achieve unique photoelectric properties, so they are promisingto be used in the field of organic electroluminescent materials widely.In this paper, the photoelectric properties could be tuned by the rigid planarstructures of acene and the special orbital interaction between silicon atom and acene.Based on this, seventeen silicon-bridged acene containing π-conjugated molecules aredesigned, fifteen of which have not been reported and the synthetic routes are alsodesigned.Quantum chemistry calculation methods awarded the Nobel Prize in1998has abig advantage in the study of new type of functional molecules, a large number ofstudies have shown that research results on material structure and peroperties with thismethod is reliable and can improve the efficiency of study.The theoretical studies on the designed molecules are proformed by B3LYP/6-31G(d) with Gaussian03software，including geometrical structure of ground state,frontier molecular orbit, energy gap, ionization potential, electron affinity,reorganization energy and absorption spectra.The skeleton structures of Silicon-bridged acene containing π-conjugatedmolecules are studied, and found that among which, dibenzosilafluorene (molecule6)has the minimum vertical ionization potential, adiabatic ionization potential andhole extraction potential, and the maximum vertical electron affinity, adiabaticelectron affinity and electron extraction potential. So it maybe has strong hole andelectron injecting ability and stronger than pentacene. Dinaphthosilole (molecule8)has the minimum hole and electron reorganization energy, smaller than the typicalhole transport material TPD[0.29eV] and electron transport material Alq3[0.276eV].Their difference is minimum, only0.025eV, would become a kind of promisingbipolar transporting material.On the skeleton of dibenzosilafluorene and dinaphthosilole screened, differentsubstituents on their performance are studied. Among different substituteddibenzosilafluorenes (6a~6g) and different substituted dinaphthosiloles (8a~8f), t heirhole and electron reorganization energy are smaller than TPD and Alq3except molecule6b. Molecule6a and8f have the lowest energy gap, respectively3.8096and3.5103eV, their stability are better than pentacene. The hole reorganization energy ofmolecule6f and8f is the smallest, respectively0.2053and0.2091eV. The electronreorganization energy of molecule6d and8a is the smallest, respectively0.2162and0.2002eV. The hole and electron reorganization energy of molecule6c and8d are thesmallest of their kinds, respectively0.0043and0.0025eV, would become a betterbipolar transporting material. Ionization potential of molecule6d and8f for about6.01eV is the smallest, smaller than pentacene’s6.59eV reported in the literature, sothey maybe have stronger hole injecting ability than pentacene. Electron affinity ofmolecule6b and8f for about0.90eV is the biggest, bigger than pentacene’s-1.4eVreported in the literature, so they maybe have stronger electron injecting ability thanpentacene. These results provide theoretical guidance for research on the novelorganic photoelectric materials, improve the efficiency of research and reduce thecost.