A Semiconducting Organic Radical Cationic Host-Guest Complex

Abstract

The self-assembly and solid-state semiconducting properties of single crystals of a trisradical tricationic complex composed of the diradical dicationic cyclobis(paraquat-p-phenylene) (CBPQT(2(center dot+))) ring and methyl viologen radical cation (MV center dot+) are reported. An organic field effect transistor incorporating single crystals of the CBPQT(2(center dot+))CMV(center dot+) complex was constructed using lithographic techniques on a silicon substrate and shown to exhibit p-type semiconductivity with a mobility of 0.05 cm(2) V-1 s(-1). The morphology of the crystals on the silicon substrate was characterized using scanning electron microscopy which revealed that the complexes self-assemble Into "molecular wires" observable by the naked-eye as millimeter long crystalline needles. The nature of the recognition Processes driving this self assembly radical radical interactions between. bipyridinium radical cations (BIPY center dot+), was further investigated by resonance Raman spectroscopy in conjunction with theoretical investigations of the vibrational modes, and was supported by X-ray structural analyses of the complex and its free components in both their radical cationic and dicationic redox states. These spectroscopic investigations demonstrate that the bond order of the BIPY center dot+ radical cationic units of host and guest components is not changed upon complexation, an observation which relates to its conductivity in the solid-state. We envision the modularity inherent in this kind of host guest complexation could be harnessed to construct a library of custom-made electronic organic materials tailored to fit the specific needs of a given electronic application.