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Binuclear ZnPc complexes covalently bridged by catechol units have been synthesized and their absorption and photochemical properties examined. The complexes studied are 1,2-bis-2',9',16',23'-triphenoxyphthalocyaninatozinc benzene (6a), 1,2-bis-2'-9',16',23'-tri-4-carboxyphe-noxyphthalocyaninatozinc benzene (6b), 1,2-bis-2',9',16',23'-tri-4-nitrophenoxyphthalocyaninato- zinc benzene (6c) and 1,2-bis-2'-9',16',23'-tri-4-tert-butylphenoxyphthalocyaninatozinc benzene (6d). Larger intramolecular coupling was observed for 6b and 6c, containing the carboxyphenoxy and nitrophenoxy substituents, respectively, than for 6a and 6d. A single Q band peak was observed for the fluorescence spectra of 6b and 6c, whereas, 6a and 6d showed a split Q band. The absence of the high energy fluorescence peaks corresponding to absorbance peaks in the 640 nm region, suggests that the intramolecular coupling is broken by excitation for complexes 6b and 6c.

Adjacent binaphthalo-phthalocyanines tetra-substituted with phenoxy (4a), 4-carboxyphenoxy (4b) and 4-t-butylphenoxy (4c) groups, as well as the di-substituted 4-carboxyphenoxy (5b) have been synthesized and characterized. The photophysical and photochemical behavior of 4a-c, were compared with those of the corresponding di-substituted derivatives, (5a-c). The secondary substituents on the phenoxy ring have an influence on the aggregation of the molecules and hence on their photophysical properties. All of the complexes exhibit a relatively good conversion of energy from the triplet-excited state to the singlet oxygen. The less aggregated molecule (4c), has the highest singlet oxygen quantum yield. For all the molecules, fluorescence yields are low and they all have relatively shorter triplet lifetimes compared with the unsubstituted zinc phthalocyanine. Increasing the number of ring substituents on these rigid MPc complexes (from complexes 5 to 4) showed a general increase in the triplet state lifetimes and singlet oxygen quantum yields, and a decrease in stability.

The octacarboxyl gallium (GaPcC) and metal-free (H2PcC) phthalocyanines were prepared using the carboxyl as the peripheral substituent. The carboxylation improves the intracellular delivery of these two PcCs into KB and QGY cancer cells as compared to that of sulfonated aluminum phthalocyanines (AlPcS), a popularly used photosensitizer (PS). Moreover, GaPcC maintains high photoproduction of singlet oxygen. With a short incubation time of 3 hours, GaPcC accumulates sufficiently in both KB and QGY cells and improves photodynamic therapy (PDT) by effectively killing these cancer cells. AlPcS and H2PcC show much lower PDT effects under the same conditions, because AlPcS have a slow cellular uptake rate resulting in a low cellular amount and the ability of H2PcC to produce 1O2 is low. Carboxylation is a promising way to prepare water-soluble metal phthalocyanines (MPcCs) and facilitates the cellular uptake of MPcCs for PDT improvement.

Spinach ferredoxin has been studied electrochemically at a glassy carbon electrode (GCE) modified with cobalt(II) tetrasulfophthalocyanine ([Co(II)TSPc]4−). Anodic peak currents due to the oxidation of the cysteine component of ferredoxin were observed at 0.90 V (vs. Ag/AgCl) (pH 7.4, HEPES buffer). The magnitudes of the peak currents were dependent on pH. Catalytic oxidation of ferredoxin was also observed when the GCE was modified with cobalt(II) and oxomolybdenum(V) phthalocyanine [CoPc and OMo(OH)Pc, respectively], and with copper(II) tetrasulfophthalocyanine complexes ([Cu(II)TSPc]4−).

Cobalt (4) and iron (5) phenylthio-substituted phthalocyanines ( MPc ( SR )8) have been synthesized and characterized. Cyclic square wave voltammetry in dimethylformamide containing tetrabutylammonium perchlorate revealed five and six redox processes, respectively, for complexes 4 and 5. The complexes are easier to reduce compared to the corresponding unsubstituted MPc and to butylthio substituted derivatives. The first oxidation and reduction occurs on the metal for both complexes. Spectroelectrochemistry (in dimethylformamide containing tetrabutylammonium perchlorate) was employed to assign the cyclic voltammetry peaks, and gave spectra characteristic of Fe I Pc for reduction of 5 and Co I Pc for the reduction of 4. The spectrum of the former is particularly of importance since such species have not received much attention in the literature.

The synthesis of a phthalocyanine-porphyrin heteropentamer (zinc(II) tetra(5-phenoxy-10,15,20-triphenylporphyrin)) zinc(II) phthalocyanine, ( ZnPc -( ZnTPP )4), containing four units of zinc tetraphenylporphyrin linked to a central zinc phthalocyanine macrocycle via an ether linkage is reported. The photophysical parameters of the pentamer are reported in toluene and dimethyl sulfoxide ( DMSO ). The observed differences in the fluorescence behavior of the pentamer in the two solvents is explained in terms of emission from different states; charge transfer state in DMSO and locally excited state in toluene. The rate constants for fluorescence, intersystem crossing, internal conversion, and of charge and energy transfer are reported for the pentamer. Quantum yields for fluorescence, internal conversion, triplet state and of charge and energy transfer are also reported for the pentamer, ZnPc -( ZnTPP )4 and the mixture of ZnPc and ZnTPP . The latter two parameters are higher in the pentamer compared to a mixture containing ZnPc and ZnTPP .

The preparation of the thiol-derivatised iron(II) phthalocyanine (FePc) complex, 2,3,9,10,16,17,23,24-octabutylthiophthalocyaninatoiron(II), FePc(SC4H9)8, is described. Electrochemical data obtained by both cyclic voltammetry and Osteryoung square wave voltammetry in DMF showed four redox couples. Kinetics and equilibrium measurements for the interaction of cyanide with FePc(SC4H9)8 at 25.0 ± 0.5 °C in both DMSO and DMF are reported. Gradual spectroscopic changes were only observed for the formation of the dicyano complex, [(CN)2FePc(SC4H9)8]2−. This complex is formed with equilibrium constants, K, of (6.8 ± 0.8) × 102 dm3 mol−1 in DMF and (1.3 ± 0.2) × 103 dm3 mol−1 in DMSO. Pseudo-first-order rate constants, k4r, were also estimated to be (1.9 ± 0.1) × 10−2 and (8.2 ± 0.3) × 10−2 dm3 mol−1 s−1 in DMF and DMSO, respectively. These results agree with the weak electron-donating properties of the peripheral butylthio-substituents on the phthalocyanine ring and the O-bonded trans DMF.

The synthesis of thiol-derivatized cobalt phthalocyanine complex, 2,3,9,10,16,17,23,24-octa (butylthiophthalocyaninatocobalt(II) ( CoOBTPc ) is described. Cyclic voltammetric data of this complex in DMF showed five quasi-reversible and reversible, diffusion-controlled redox couples, comprising both the phthalocyanine ring and central metal redox processes. The CoOBTPc complex forms a self-assembled monolayer (SAM) on gold electrode. The investigation of the integrity of this SAM, using the established cyclic voltammetric methods in aqueous alkaline solutions, gave evidence about the formation of a stable and easily reproducible monolayer. However, due to its susceptibility to destruction via oxidative and reductive desorptions, its potential application as an electrochemical sensor in alkaline pH is limited to a potential window of between −0.20 and +0.55 V vs Ag / AgCl .

Photochemical and photophysical measurements were conducted on pentoxy and naphthaloxy appended zinc and magnesium phthalocyanines. We describe in this paper the synthesis as well as unexpected photodegradation behavior of naphthaloxy appended magnesium phthalocyanines. General trends are described for quantum yields of photodegradation, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds.

The electrochemical properties of 14 structurally related pyrroloquinoline metabolites (compounds 1-14) isolated from marine sponges were studied in pH-varied experiments using cyclic and square wave voltammetry. In general both substitution patterns and pH were observed to influence the reduction potentials of these molecules.

Spectroscopic changes observed on addition of nitrite to solutions of cobalt(II) tetra-sulfophthalocyanine ([Co(II)TSPc]4-) in the presence of N− 3 or ClO− 4 are reported. There is spectroscopic evidence for the oxidation of [Co(II)TSPc]4- to a [Co(III)TSPc]3- species in the presence of nitrite ions. Equilibrium and kinetic studies for the interaction between [Co(II)TSPc]4- and NO− 2 are reported. The rate was found to be first order in both [Co(II)TSPc]4- and NO− 2. The rate constant for the forward reaction, k f=1.6 × 10−4 dm3mol−1s−1 was determined at 20°C for the interaction between nitrite ions and [Co(II)TSPc]4- in the presence of NO3 − or ClO4 − ions.

Chemical oxidation of the dichloromethane solutions of oxomolybdenum phthalocyanine (Mo(IV)OPc), using dilute solutions of bromine in dichloromethane or using ferric chloride results in the oxidation at the central metal ion, giving a Mo(V)OPc complex. Chemical oxidation is reversible in both the bromine and ferric chloride oxidized species. Oxidation of MoOPc is coupled to a reversible coordination of axial ligands to the oxidized species, with the possible formation of a six coordinate complex. Spectral data also reveal that the oxygen atom remains coordinated to the oxidized complex.

Cyclic voltammetry of tin(IV) diphthalocyanine (Pc2Sn) in dichloromethane containing TEAP shows two reduction couples at −0.56 and −0.89 versus saturated calomel electrode (SCE) and one oxidation couple at 0.35 V versus SCE; all were quasireversible one-electron couples. The oxidation couple corresponds to [Pc(−1)SnIVPc(−2)+/Pc(−2)SnIVPc(−2) and the reduction couples to Pc(−2)SnIVPc(−2)/[Pc(−3)SnIVPc(−2)]− and [Pc(−3)SnIVPc(−2)]−/[Pc(−3)SnIVPc(−3)]2−, respectively. The electronic absorption spectra of the various reduced or oxidized tin(IV) diphthalocyanine species are reported.

The synthesis, spectral and photophysical properties including fluorescence quenching of the following octa-substituted oxotitanium phthalocyanines are reported: 2,3,9,10,16,17,23,24-octaphenoxyphthalocyaninato titanium(IV) oxide, 2,3,9,10,16,17,23,24-[octakis(4-t-butylphenoxyphthalocyaninato)]titanium(IV) oxide, 2,3,9,10,16,17,23,24-{octakis[(4-benzyloxy)phenoxy]phthalocyaninato}titanium(IV) oxide and 2,3,9,10,16,17,23,24-octaphenylthiophthalocyaninato titanium(IV) oxide. The complexes are characterized by1H NMR, IR and UV-vis spectroscopies. Their photophysical properties are presented where moderate fluorescence quantum yields (0.14-0.19) and lifetimes were determined. Varied triplet quantum yields were obtained and the triplet lifetimes (40-100 μs) were short.

Diphthalocyanine complexes of Nd III , Eu III , Tm III and Lu III ( [Pc (−2) Nd III Pc (−2) ] − , [Pc (−2) Eu III Pc (−2) ] − , [Pc (−2) Tm III Pc (−2) ] − and [Pc (−2) Lu III Pc (−2) ] − , respectively) , undergo one or two-electron oxidation in the presence of thionyl chloride. The oxidation products depend on the concentration of the thionyl chloride. At low concentrations of SOCl 2 ( −4 mol dm −3 ) one-electron oxidation occurs only upon photolysis, giving the neutral lanthanide diphthalocyanine, Pc (−2) LnPc (−1) , complexes. The Pc (−2) LnPc (−1) species undergo one-electron photooxidation to the [Pc (−1) LnPc (−1) ] + in dichloromethane and in the presence of SOCl 2 . At large concentrations of SOCl 2 (>10 −2 mol dm −3 ) , two electron oxidation of the [Pc (−2) LnPc (−2) ] − species directly to [Pc (−1) LnPc (−1) ] + occurs.

The photophysical and photochemical properties and quenching (by 1,4-benzoquinone) of metallophthalocyanine sulfonates of aluminium ( AlPcSmix), zinc ( ZnPcSmix), silicon ( SiPcSmix), germanium ( GePcSmix) and tin ( SnPcSmix) are presented. The quantum yield values of fluorescence (ΦF), triplet state (ΦT), singlet oxygen (ΦΔ) and photodegradation (Φd) were determined and the observed trends in their variation among the complexes discussed in terms of aggregation and the heavy atom effect. 1,4-benzoquinone effectively quenched the fluorescence of the complexes. Quenching analyses gave positive deviations from Stern-Volmer behavior, suggesting the existence of static quenching in addition to dynamic quenching. The static and dynamic components of the quenching were separated using a modified Stern-Volmer equation and the “sphere of action quenching model”. The quenching constant was found to be a function of the radius of the central metal ion.

Photolysis, using a visible radiation, of diphthalocyanine complexes of Nd III , Dy III and Lu III ([Pc(−2)Nd III Pc(−2)] − , [Pc(−2)Dy III Pc(−2)] − and [Pc(−2)Lu III Pc(−2)] − , respectively) in the presence of pentachlorophenol (PCP) or SO 2 results in the one-electron oxidation of the diphthalocyanine species to Pc(−1)Nd III Pc(−2), Pc(−1)Dy III Pc(−2) and Pc(−2)Lu III Pc(−2), respectively. The PCP is reductively dechlorinated to tetra- and trichlorophenols. The quantum yields for the photosensitization reactions are of the order 10 −4 .

In this review, we report on the newly developed area of research devoted to the formation of self-assembled monolayers of metallophthalocyanines by focusing on some significant examples dedicated to electroanalytical applications. We also summarize recent examples on the use of electropolymerized metallophthalocyanine films in electroanalysis. In both cases, activation and detection of thiols are the main targeted applications.

The photochemistry and photophysics of six axially substituted silicon phthalocyanines are reported and show the importance of the axial groups in the photochemistry of these compounds. The fluorescence quantum yields are especially affected by the axial ligand. A very good correlation was found for the experimentally determined fluorescence lifetimes and the theoretically determined lifetimes using the Strickler-Berg equation for the unaggregated molecules.

Modification of carbon electrodes with first row transition metal phthalocyanines results in the lowering of the potentials needed for water electrolysis in basic media, by 600 to 700 mV when compared to unmodified carbon electrodes. Nickel(II), cobalt(II) and iron(II) phthalocyanines show higher catalytic activity than zinc(II), manganese(II), copper(II) and metal free phthalocyanines.

The purpose of this review is to compile preclinical and clinical results on phthalocyanines (Pcs) as photosensitizers (PS) for Photodynamic Therapy (PDT) and contrast agents for fluorescence imaging. Indeed, Pcs are excellent candidates in these fields due to their strong absorbance in the NIR region and high chemical and photo-stability. In particular, this is mostly relevant for their in vivo activation in deeper tissular regions. However, most Pcs present two major limitations, i.e., a strong tendency to aggregate and a low water-solubility. In order to overcome these issues, both chemical tuning and pharmaceutical formulation combined with tumor targeting strategies were applied. These aspects will be developed in this review for the most extensively studied Pcs during the last 25 years, i.e., aluminium-, zinc- and silicon-based Pcs.

Studies on the catalytic reduction of nitrite on carbon electrodes modified with Co(II) tetra-2,3-pyridinoporphyrazine (CoTppa, 1), N,N′,N′′,N′′′-tetramethyltetra-2,3-pyridinoporphyrazine ([CoTm-2,3-tppa]4+, 2) and Co(II) N,N′,N′′,N′′′-tetramethyltetra-3,4-pyridinoporphyrazine ([CoTm-3,4-tppa]4+, 3) are reported. There is a close correspondence between the proximity of the methyl groups to the porphyrazine ring and the catalytic activity of the porphyrazine complexes. Bulk electrolysis gave ammonia and hydroxylamine as some of the products. The catalytic activity of the cationic complex, 3, towards the detection of low concentrations of nitrite (

A series of cyclopentadienylnickel(II) organochalcogenides containing different phosphines have been prepared by either reacting [CpNi( μ -SC 6 H 4 X-4)] 2 (Cp # = η 5 -C 5 H 5 ,(Cp), η 5 -C 5 H 5 Me, (Cp′); X=Cl, Br) with phosphines or Cp # Ni(PR 3 )Br with HSC 6 H 4 X-4 and Et 3 N or NaSeC 6 H 4 Cl-4. The complexes that were isolated have the general formula CpNi(PR 3 )(EC 6 H 4 X-4) {E=S, X=Cl, R=Ph ( 1a ), Bu ( 2a ), OPh ( 3a ), OEt ( 4a ), OMe ( 5a ); X=Br, R=Bu ( 6a ), Ph ( 7a )}. In addition to spectroscopic characterisation, the complexes CpNi(PBu 3 )(SC 6 H 4 Cl-4) ( 2a ) and Cp'Ni(PPh 3 )(SeC 6 H 4 Cl-4) ( 9a ) were subjected to single-crystal X-ray diffraction studies. While the solution and solid state structures of CpNi(PBu 3 )(SC 6 H 4 Cl-4) were found to be the same, that of Cp'Ni(PPh 3 )(SeC 6 H 4 Cl-4) were different. The orientation of the methyl group of 9a in the solid state is almost trans to the phosphine, but solution NMR data indicate that the methyl substituent on the cyclopentadienyl ligand is cis to the phosphorus. All the complexes, 1a – 9a , were found to react reversibly with SO 2 to form SO 2 adducts and the reversibility could be monitored by visible and 1 H-NMR spectroscopy. Electrochemical studies show that 2a and 6a have reversible couples whereas 1a and 7a are only quasi-reversible. The PBu 3 complexes are easier to oxidise as compared with the PPh 3 analogues.

Kinetics for the interaction of cobalt(II) tetrasulfophthalocyanine ([Co II TSPc] 4− , Pc(−2) = phthalocyanine dianion) with the amino acids, histidine and cysteine, in pH 7.2 phosphate buffer were studied. The rates were found to be first order in both the [Co II TSPc] 4− and the amino acid. The formation of the [Co III TSPc] 3− species in the presence of histidine occurred with a rate constant of 0.16 dm 3 mol − s −1 , whereas the formation of the [Co I TSPc] 5− species in the presence of cysteine gave a rate constant of 2.2 dm 3 mol −1 .

Cyclic voltammetry and spectroelectrochemistry studies are reported for the tetramethyl- tetrapyridinoporphyrazine complexes N,N′,N″,N‴-tetramethyltetra-2,3-pyridinoporphyrazine palladium(II) (1a), N,N′,N″,N‴-tetramethyltetra-3,4-pyridinoporphyrazine palladium(II) (1b), N,N′,N″,N‴-tetramethyltetra-2,3-pyridinoporphyrazine platinum(II) (2a) and N,N′,N″,N‴-tetramethyltetra-3,4-pyridinoporphyrazine platinum(II) (2b). Cyclic voltammetry on Pt disc electrodes showed two reductions. The first reduction was assigned to one-electron transfer to the ring with the formation of a monoanion species. All the tetramethyltetrapyridinoporphyrazine complexes are readily reduced to the monoanion species in the presence of histidine or cysteine. The rate constants for the interaction of complexes 1a, 1b, 2a and 2b with histidine and cysteine range from ~2 × 10−3 to 0.26 dm 3 mol −1 s −1.