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A series of peripherally substituted phthalocyanines (Pcs) with different central metals (Al, Ga and In) and axial chloride ligand were synthesized and their photophysical and optical limiting properties were investigated. The Q band absorption of the Pc shifts to longer wavelength with the central metals changing from Al to In, and the fluorescence quantum yields of S1 emission decrease remarkably from Al to In. Transient absorption spectra of the Pcs in THF were measured in determination of the photophysical parameters. The optical limiting properties were investigated by a nanosecond pulse laser at 532 nm. All of these compounds exhibit good optical limiting performance, and the optical limiting behaviors of solid solution in glass obtained by sol–gel technique are much better than that of liquid solution. Several factors which affect the optical limiting performance of the Pcs with different central metals and substituents are discussed.

Zn-tetrasulfophenylporphyin (ZnTSPP), stable colloidal TiO2 and a transparent microporous TiO2 electrode have been prepared. The interaction of ZnTSPP with colloidal TiO2 was studied by absorption and fluorescence spectroscopy, the apparent association constant for the association between ZnTSPP and TiO2 nanoparticles is about 1.6 × 104 M−1. ZnTSPP adsorbed on colloidal TiO2 can participate in the sensitization process by injecting electrons from its excited states into the conduction band of TiO2. Upon excitation of its absorption band, 90% of the fluorescence emission of ZnTSPP could be quenched by colloidal TiO2 and the maximum of incident photon to current efficiency is 51.3% at 427 nm with a 10 μm thick TiO2 film sensitised by ZnTSPP.

The cosensitization of a nanostructured TiO2 electrode with the spectral complementary dyes, tetrasulfonated gallium phthalocyanine (GaTsPc) and tetrasulfonated zinc porphyrin (ZnTsPP), is reported. For the liquid junction cell based on a nanostructured TiO2 electrode cosensitized with GaTsPc and ZnTsPP molecules, cosensitization extends the absorbance into the region 400–750 nm, resulting in an improvement of the light-harvesting efficiency and short-circuit photocurrent on illumination at 35.7 mW cm−2. The photocurrent response at 685 nm, corresponding to the absorbance of the GaTsPc monomer, is strongly enhanced, probably due to the decrease in the surface concentration of GaTsPc molecular dimers and the possible formation of an extended π system in GaTsPc/ZnTsPP heteroaggregates resulting from cosensitization of the electrode.

Absorption spectroscopy of tetrasulfonated Zn, Co, Ga, In, TiO and metal-free phthalocyanine on a transparent titanium dioxide film electrode, which is made up of interconnected particles and pores characterized by scanning electron microscopy, has been reported. The chemical modification of the TiO 2 microporous electrode with tetrasulfonated phthalocyanine (MTsPc) extends its absorbance into the visible region. The tetrasulfonated phthalocyanine mainly exists as the dimer on the TiO 2 microporous electrode. The photocurrent action spectroscopy shows that only the absorbance of the MTsPc monomer contributes to the photocurrent while that of the MTsPc dimer does not generate a photocurrent.

The alkali cation complexation of phthalocyanine substituted with four crown ether rings (H 2 CRPc) was studied by UV-visible absorption and fluorescence spectroscopy. Cation-induced aggregation of the crowned phthalocyanine occurred in solution. When the diameters of the cations (K + , Rb + ) slightly exceeded that of the crown ether ring, they acted cooperatively leading to the formation of a cofacial dimer. Smaller cations (Li + , Na + ), which could be encapsulated into the cavity of the crown ether voids, were unable to cause complete conversion to a cofacial dimer. Large Cs + ions induced sandwich-like aggregation in solution more rapidly. The monomer-dimer equilibrium formation constants for K + - and Rb + -induced aggregation were calculated to be of the order of 10 9 l 2 M −2 .

A new amphiphilic zinc phthalocyanine (AmZnPc), containing long alkyl chains covalently linked to the positively charged macroring with the counter-anion iodide as electron donor, was synthesized. Multilayers of AmZnPc mixed with hydrophobic porphyrin were successfully fabricated on CaF 2 plates. From Fourier-transform IR (FTIR) transmission and polarized transmission spectroscopic studies, it was found that the long alkyl chains of AmZnPc exhibit hexagonal subcell packing and are oriented nearly perpendicular to the AmZnPc macroring. The AmZnPc macroring is oriented almost parallel to the substrate surface, whereas the porphyrin is embedded in the cavity between the long alkyl chains of AmZnPc and is tilted somewhat from the substrate surface.

Intramolecular transfer processes in porphyrin—phthalocyanine heterodimers covalently linked by an oxygen atom (restricted conformation) and/or by a flexible chain of variable length were investigated. Fluorescence spectroscopy shows that singlet—singlet energy transfer from the porphyrin to the phthalocyanine moiety occurs. From fluorescence decay studies, it is concluded that the heterodimers exist in solution in different non-equilibrating conformations. The effects of the chain length and mutual orientation of the chromophore subunits in the heterodimers on the intramolecular energy and electron transfer efficiencies are discussed.

An amphiphilic zinc phthalocyanine (AmZnPc) containing long alkyl chains covalently attached to the positively charged macroring was synthesized. A monolayer of AmZnPc with equimolar meso-tetrakis-(4-tolyl)porphine (TTP) was spread on water from chloroform solution and transferred onto CaF 2 slides. Multilayers were also built up on these substrates. Surface pressure-area isotherms and UV—visible absorption spectra showed that the porphyrin molecules are arranged in the cavity between the long alkyl chains of AmZnPc in one layer of the Langmuir—Blodgett film. Polarized UV—visible spectroscopy indicated that there is no anisotropy in the layer plane and the AmZnPC macroring plane lies nearly parallel to the substrate surface.

Metal phthalocyanine photosensitized donor—acceptor systems for light energy conversion and for the design of photoelectrochemical molecular devices are presented. Fluorescence studies show that the fluorescence and lifetime of the phthalocyanine moiety are appreciably diminished by attached viologen, quinones and porphyrin. The quenching of the fluorescence of zinc phthalocyanine by linked viologen, giving rise to a long-lived charge separated state, was observed by nanosecond laser photolysis. The decrease in the fluorescence and lifetime induced by quinones was examined and the apparent electron transfer rate constants were calculated depending on the chain length and solvent polarity. When these linked compounds were incorporated into a lipid bilayer membrane (LBM) and/or coated on a transparent tin oxide electrode, and enhancement of the photoeffects was observed compared with non-linked compounds and can be explained in terms of intramolecular charge transfer processes.