The first-principles discrete variational method local exchange (DV-X alpha ) technique has been employed to study electronic structure in the conductive polymer building blocks Si(Pc)(OH)//2 and HOSi(Pc)-OSi(Pc)OH (Pc equals phthalocyaninato). For the monomer, a 'four orbital' porphyrin-like pi electron structure is obtained, and excellent agreement between experimental and calculated optical spectral features is observed. The HOMO-HOMO splitting in the cofacial dimer (2t) can be related to the tight-binding conduction bandwidth in the corresponding polymer (4t). Favorable agreement is obtained between the DV-X alpha calculated splitting and that observed in dimer UPS measurements and polymer optical analyses.
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