posted on 2003-07-11, 00:00authored byCarrie L. Donley, Wei Xia, Britt A. Minch, Rebecca A. P. Zangmeister, Anthony S. Drager, Kenneth Nebesny, David F. O'Brien, Neal R. Armstrong
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; Langmuir2001, 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 their rodlike
aggregates, through formation of cyclobutane links between adjacent side chains. Compound 1 shows a
maximum 75% conversion of styryl groups versus ca. 55% conversion in 2. Polymerized thin films of 1 are
insoluble in common solvents, and “ribbonlike” features can be lithographically produced with widths of
8 microns and heights of ca. 20 nm, maintaining control over the orientation of the Pc rods in the patterned
features. Long-range order in both the as-deposited, annealed, and polymerized thin films was confirmed
by atomic force microscopy and X-ray reflectometry, and small differences in the orientation of individual
Pc's, between films of 1 and 3, were determined by transmission and reflectance Fourier transform infrared
spectroscopy. Higher dark and photoconductivities and higher electrical anisotropies were observed in
films of 1, after annealing and polymerization, versus those seen for films of 3.