Phthalocyanine thin films preparation

Tanabe, H. and K. Ohno (1987). Electrocatalysis of metal phthalocyanine thin film prepared by the plasma-assisted deposition on a glassy carbon in the reduction of carbon dioxide. Electrochim. Acta, 32(7), 1121-1124. 

Harima, Y. and K. Yamashita (1989). Electrochemical characterization of phthalocyanine thin films prepared by the electrolytic micelle disruption method. J. Phys. Chem. 93, 4184-4188. 

A common route to phthalocyanine sheet polymers involves the condensation of 1,2,4,5-tetra-cyanobenzene with a metal salt, Scheme 4.1. Unfortunately, the sheet polymer is contaminated with polyisoindolenine and triazine linkages, which reduce its planarity and conductivity. Since these polymers are generally insoluble and not sublimable, it is difficult to remove the defects or impurities. Wohrle has developed an improved route to 2 (M = Cu11) by employing lithium pentanolate to reduce the density of defects in the resulting polymers.23 Improved approaches for thin-film preparation were also explored. 

Figure 5. O Is XPS spectra of Pb phthalocyanine thin films after different treatments. a as preparation imder UHV(ultra-high-vacuum) conditions, b afler exposure of UHV-prepared films to air, c afler the air-exposed filmes in SOOmbar O2 at 423K[7].

Polymeric metal-containing (Cu, Mg, Zn, and Ni) and metal-free phthalocyanine thin films were prepared from the gas phase by low-temperature plasma polymerization [115, 116]. The plasma-polymerized CuPc (pp-CuPc) obtained was a glossy greenish thin film with a thickness of 60-300 nm. The film was smooth and even, and was soluble neither in pyridine nor in concentrated sulfuric acid, both of which are good solvents for monomeric CuPc. 

Thin films of phthalocyanine compounds in general, and those prepared by the LB method in particular, display novel electrical properties (Baker, 1985). The LB technique for depositing mono- and multilayer coatings with well-controlled thickness and morphology offers excellent compatibility with microelectronic technology. Such films have recently been reviewed for their potential applications. The combination of LB supramolecular films with small dimensionally comparable... 

Monolayer Films of Phthalocyanine Derivatives. A series of organic derivatives of phthalocyanines were prepared that have two important characteristics of materials to be deposited by the Langmuir-Blodgett technique (1) they are soluble in volatile organic solvents, and (2) they form monomolecular films on the surface of water. Further study of deposited films of these phthalocyanine derivatives will be necessary in order to determine the exact orientations on the surface, but regardless of their orientations, they offer interesting possibilities for construction of thin films of ordered arrays of molecules on the surface of gas sensors. 

A large class of coordination compounds, metal chelates, is represented in relation to microwave treatment by a relatively small number of reported data, mainly p-diketonates. Thus, volatile copper) II) acetylacetonate was used for the preparation of copper thin films in Ar — H2 atmosphere at ambient temperature by microwave plasma-enhanced chemical vapor deposition (CVD) [735a]. The formed pure copper films with a resistance of 2 3 pS2 cm were deposited on Si substrates. It is noted that oxygen atoms were never detected in the deposited material since Cu — O intramolecular bonds are totally broken by microwave plasma-assisted decomposition of the copper complex. Another acetylacetonate, Zr(acac)4, was prepared from its hydrate Zr(acac)4 10H2O by microwave dehydration of the latter [726]. It is shown [704] that microwave treatment is an effective dehydration technique for various compounds and materials. Use of microwave irradiation in the synthesis of some transition metal phthalocyanines is reported in Sec. 5.1.1. Their relatives - porphyrins - were also obtained in this way [735b]. 

M = Tb, Lu) into organic thin-film transistors by LB technique and reported their field effect mobility, which represented the first report for p-type OFETs based on bis(phthalocyaninato) rare earth complexes prepared via LB method [88], Due to the highly ordered molecular arrangement of M(Pc)[Pc(OC8Hi7)g] (M = Tb, Lu) in LB films and the appropriate HOMO energy level of these double-deckers relative to the Au source-drain electrodes, the OFETs reported in that work exhibited higher hole transfer mobility of 1.7 x 10-3 cm2 V-1 s-1 in comparison with those fabricated from monomeric phthalocyanine LB films. 

Suspensions of polyacetylene were prepared as burrs or fibers (46) by using a vanadium catalyst. When the solvent was removed, films of polyacetylene were formed with densities greater than that prepared by the Shirakawa method. These suspensions were mixed with various fillers to yield composite materials. Coatings were prepared by similar techniques. Blends of polypyrrole, polyacetylene, and phthalocyanines with thermoplastics were prepared (47) by using the compounding techniques typically used to disperse colorants and stabilizers in conventional thermoplastics. Materials with useful antistatic properties were obtained with conductivities from 10" to 10" S/cm. The blends were transparent and had colors characteristic of the conducting polymer. For example, plaques containing frans-polyacetylene had the characteristic violet color exhibited by thin films of solid trans-polyacetylene. 

Michaelis, E., Nonomura, K Schlettwein, D., Yoshida, T., Minoura, H., and Wehrle, D. (2004) Hybrid thin films of ZnO with porphyrins and phthalocyanines prepared by one-step electrodeposition. J. Porph. Phthalocyanin., 8,1366-1375. 

Polymeric phthalocyanines such as 31 exhibit good thermal stability under inert gas up to -500 °C and under oxidative conditions up to -350 °C [59]. One way to enhance the electrical conductivity is by enlarging the conjugated n-electron system in the two-dimensional plane of the polymeric phthalocyanines. Compressed powders of polymer 31 exhibit intrinsic conductivities in the order of 10 -10 S cm [55,56,100,101]. The conductivity increases to 10 -10 S cm for thin films of 31 prepared by the reaction of a Cu-film with tetracyanobenzene as described before [89]. 

One can also mention the case of composites-based conducting polymers electrodeposited and characterized on anodes of platinum- or carbon black- filled polypropylene from a stirred electrolyte with dispersed copper phthalocyanine. The electrolytic solution contained, besides the solvent (water or acetonitrile), the monomer (pyrrole or thiophene) and a supporting electrolyte. Patterned thin films were obtained from phthalocyanine derivatives, as reported in the case of (2,3,9,10,16,17,23,24-oktakis((2-benzyloxy)ethoxy)phthalocyaninato) copper . Such films were prepared by means of capillary flow of chloroform solutions into micrometer-dimension hydrophobic/hydrophilic channels initially created by a combination of microcontact printing of octadecylmercaptan (Cig-SH) layers on gold electrodes. These latter gave birth to a hydrophobic channel bottom while oxidative electropolymerization of w-aminophenol (at pH 4) led to hydrophilic channel walls. 

Film preparation plays a crucial role in determining the photoelectrochemical properties of phthalocyanine electrodes. Since the coupling of individual chromophores strongly depends on their relative orientation, the position of the absorption maximum and its width shows a clear dependence on the structure of thin films. Also the charge transport within phthalocyanine films, a fundamental necessity for the films to work as electrodes, depends upon the overlap of the frontier orbital wave functions. Beyond the microscopic structure of films also the morphology of films plays an important role. In the case of crystalline films, the orientation of crystallites relative to the electrode surface will be relevant because of anisotropies in optical absorption and charge transport. The size of the observed photocurrent directly depends on the real electrode surface area accessible by the electrolyte and this leads to a strong dependence on the porosity of the films. 

Sheng-Gao et prepared novel asymmetrically substituted metal-free phthalocyanine, nitro-ferf-butylphthalocyanine, which resulted suitable for fabrication as a thin film using the LB technique. 

Besides their potential applicability as NLO materials noncentrosymmetri-cal phthalocyanines with different substituents on adjacent pairs of isoindole units promise intriguing new aspects in phthalocyanine chemistry polymeric phthalocyanines without crosslinking could lead to linear polymers, controlled binding of the phthalocyanine ring to a substrate could improve the synthesis of novel catalysts [188] and the preparation of highly ordered thin films should be possible [189]. 

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