ELECTRONIC-STRUCTURE AND OPTICAL-PROPERTIES OF ELECTROLUMINESCENT SPIRO-TYPE MOLECULES

The electronic structure and optical properties of the propeller-shape d spire molecules, enyl)-1,3,4-oxadiazoyl-2-yl)-9,9'-spirobifluorene, and 2,2',7,7'-tetrakis (biphenyl-3-yl)-9,9-spirobifluorene, have been studied by photoelectron spectroscopy, Raman spectroscopy, and spectro scopic ellipsometry. The experimental spectra are analyzed with the he lp of results from quantum-chemical calculations, The excellent agreem ent between experiment and theory allows for a detailed characterizati on of the frontier electronic structure and lowest-energy optical tran sitions in these novel compounds. It follows that most of the electron ic and optical properties of the these spiro-molecules can be deduced by consideration of a single branch; in this case a sexi-phenyl and PB D branch. In particular, although the branches in the spiro molecules are perpendicular to each other, there is considerable interaction at the spiro-center between the pi-electron systems of the two branches, indicating, among other things, that chemistry involving either branch is dependent on the other branch. (C) 1997 American Institute of Phys ics.