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The direct current (dc) conductivities and organic field-effect transistor (OFET) characteristics of a class of octa-substituted liquid crystalline (discotic mesophase) phthalocyanines (Pcs) are discussed. These molecules self-organize into columnar aggregates with large coherence lengths (up to approximately 300 nm). Langmuir–Blodgett films of these molecules were horizontally transferred to either interdigitated microelectrodes (IME) or OFET substrates, so that current flow could be measured either parallel or perpendicular to the column axis. Twenty-eight bilayer films of these Pcs on the IME substrates showed anisotropies in dc conductivity up to 50:1, whereas similar Pc films showed anisotropies in field effect mobilities of approximately 10:1, for a variety of W/L ratios (source/drain dimensions and spacing). Field-effect mobilities of 1 to 5 × 10-6 cm2·V-1·s-1 were determined from OFET measurements, along the Pc column axis, whereas charge mobilities measured from the space charge limited current regime on the IME substrates were in the range of 10-4 cm2·V-1·s-1. Conductive tip atomic force microscopy measurements on the apprximately 500-nm length scale showed that the conductivity anisotropy can be as high as 1000:1 when the Pc columns are intimately contacted to an adjacent Au bond pad.

We report here the synthesis, characterization, and thin film formation of a polymerizable octa-substituted phthalocyanine (Pc) with styryl-terminated side chains, CuPc(OCH2CH2OCH2CHCHPh)8, 2,3,9,10,16,17,23,24-octakis(2-cinnamyloxyethoxy) phthalocyaninato copper(II) (1). We compare this Pc with a previously discussed phthalocyanine, also possessing styryl groups at the termini of the side chains, but with one alkoxy group in the side chain removed, CuPc(OCH2CH2CHCHPh)8 (2) (J. Am. Chem. Soc. 2001, 123, 3595). Both 1 and 2 are related to the octa-substituted phthalocyanine CuPc(OCH2CH2OBz)8, 2,3,9,10,16,17,23,24-octakis (2-benzyloxyethoxy) phthalocyaninato copper(II) (3), which has been shown to form highly coherent rodlike aggregates in Langmuir−Blodgett (LB) films, with excellent control of rod orientation (J. Am. Chem. Soc. 1999, 121, 8628; Langmuir 2001, 17, 7071). Irradiation of the styryl π−π* absorbance bands (254 nm) for horizontally transferred LB films of 1 and 2 results in stabilization of thei...

We present here a study of the effects of surface modification on the efficiency of transfer of ultrathin Langmuir−Blodgett films of rodlike aggregates of the phthalocyanine (Pc) (2,3,9,10,16,17,23,24-octakis((2-benzyloxy)ethoxy)phthalocyaninato)copper (1) to gold and silicon substrates. These surface modifications impact on (i) the molecular orientation of the individual Pcs within the rodlike aggregates, (ii) the coherence of the aggregates (providing for coherence lengths of some Pc rods of over 100 nm), and (iii) the optical anisotropy and the overall uniformity and lack of pinholes in Pc bilayer films, on the 100 μm distance scale. Methyl-terminated and phenyl-terminated surface modifiers were added to both Au and Si surfaces through thiol and silane chemistries, respectively. The phenyl-terminated modifier for Au surfaces, benzyloxyethanethiol, 2, mimics the side chain composition of Pc 1. Both methyl- and phenyl-terminated modifiers produced hydrophobic surfaces, as revealed by high water contact a...