Dendritic phthalocyanines: synthesis, photophysical properties, and aggregation behavior

Photochemical and photophysical properties of tetracarboxylic acid phthalocyanines from glycolic and lactic acids in homogeneous and micro heterogeneous media

Glycolic acid and lactic acid substituted zinc phthalocyanines were studied concerning their photophysical and photochemical properties in eight organic solvents (homogeneous medium) and in aqueous media with the presence of CTAB and PVP 360 surfactants. Solvent effects were investigated according to several physical solvent parameters, including studies that used more than one parameter at a time, such as the E_T(30) scale and the Lippet-Mataga equation. Computational studies were realized and was found in good agreement with experimental data indicating J-type dimers' formation through hydrogen bonds, which may not affect the spectroscopic properties. Fluorescence lifetimes were recorded using a time-correlated single-photon counting setup (TCSPC) technique. The direct method (analyzing the phosphorescence decay curves of singlet oxygen at 1270 nm) was employed to study singlet oxygen quantum yields. Phthalocyanine macrocycle with lactic acid substituent showed better solvation arrangement than the glycolic derivative, which can be explained based on the presence of the methyl group bonded to the chain. The water solvation of Pc's in the presence of cationic surfactant (CTAB) and biocompatible polymer PVP 360 increses the importance of this study for appliance in photodynamic therapy (PDT).

Unusual cis-diprotonated forms and fluorescent aggregates of non-peripherally alkoxy-substituted metallophthalocyanines

Protonation and aggregation of two metallophthalocyanines (zinc and magnesium) non-peripherally substituted with 1,4,7-trioxanonyl moieties were studied by steady-state and time-resolved optical spectroscopy. Both compounds are easily protonated in organic solvents, but the central metal ion strongly affects the character of this process. In particular, the magnesium derivative forms the cis-diprotonated isomer observed for the first time in phthalocyanines, in contrast to its zinc counterpart which forms the typical trans-diprotonated isomer. In addition, studies performed on phthalocyanines substituted with n-butoxy groups at their non-peripheral positions indicated that the formation of the cis-diprotonated forms is a more common feature of alkoxy-substituted magnesium metallophthalocyanines, in contrast to derivatives with other metal ions. The cis-diprotonated forms of the magnesium derivatives are formed at much lower proton concentrations than the trans-diprotonated forms of their zinc counterparts. The cis-isomers were also found to have more advantageous photophysical properties for photoactive applications than the trans-isomers. Aggregation studies of the trioxanonyl phthalocyanines revealed that the magnesium derivative aggregates much more easily in non-coordinating solvents than its zinc counterpart. Both the derivatives form fluorescent aggregates, which is typically attributed to the presence of oxygen-to-metal intermolecular coordination preventing the formation of non-fluorescent face-to-face stacks. The results indicate that the oxygen-to-metal coordination plays a significant role in the studied systems and the stronger oxygen-coordination ability of magnesium ions compared to zinc ions may underlie the observed differences between the phthalocyanines metallated with these two ions.

Morpholinyl dendrimer phthalocyanine: synthesis, photophysical properties and photoinduced intramolecular electron transfer

The photophysical properties of a novel series of morpholinyl dendrimer phthalocyanines exhibited dependence on the number of morpholinyl groups and the central ion. The photoinduced electron transfer from the morpholinyl units to phthalocyanine ring was evidenced.

One-pot three-component Biginelli-type reaction to synthesize 3,4-dihydropyrimidine-2-(1H)-ones catalyzed by Co phthalocyanines: Synthesis, characterization, aggregation behavior and antibacterial activity

The synthesis of a novel phthalonitrile derivative with pyridine-2-thiol and 2,4,6-trimethylphenylamine substituents functionalized groups and its peripherally tetrasubstituted cobalt phthalocyanine and cationic phthalocyanines complexes were reported. The aggregation investigations carried out in different concentrations indicate that Co Phthalocyanines compounds 3,4 do not have any aggregation behavior for the concentration range of 6×10(-4)-14×10(-6)M in DMSO. The ion binding properties of Co Phthalocyanines compounds 3,4 show the formation of stable complex with Co(2+). In addition 3,4-Dihydropyrimidin-2(1H)-one derivatives were synthesized by modified Biginelli cyclocondensation reaction catalyzed by MPc as Lewis base. The structures of the synthesized compounds have been successfully characterized by the spectroscopic methods (IR, (1)H NMR, (13C)NMR, UV-Vis, mass spectrometry, elemental analysis and NMR 2D). The influence of substrate/catalyst ratio, solvent was also investigated to find optimal reaction on this synthesis for getting the highest conversion. Different parameters were examined for finding optimal conditions of catalysis. In addition; the compounds 3-11 were investigated for antimicrobial activity. Most of them exhibited important antimicrobial activity.

Synthesis, spectral properties, cation-induced dimerization and photochemical stability of tetra-(15-crown-5)-phthalocyaninato indium(III)

The novel 2,3,9,10,16,17,23,24-tetra-(15-crown-5)phthalocyaninato indium(III) hydroxide [(15 C 5)4 Pc ] In ( OH )(I) was obtained by direct interaction of tetra-(15-crown-5)-phthalocyanine with indium acetylacetonate with 90% yield. The set of UV-vis, 1 H NMR and MALDI-TOF spectroscopy data allowed the unambiguous interpretation of complex structure. It was shown that the developed synthetic approach can be also used for synthesis of indium(III) 2,3,9,10,16,17,23,24-octabutoxyphthalocyanine [( BuO )8 Pc ] In ( OH )(II). Photophysical characteristics (fluorescence and singlet oxygen quantum yields) of I were established. The photochemical stability of I was compared with tetra-(15-crown-5)-phthalocyanine H 2[(15 C 5)4 Pc ] and aluminum(III) complex [(15 C 5)4 Pc ] Al ( OH ). It was found that cation-induced formation of cofacial dimers [2I × 4MX] ( M = K +, Rb +, X = CO 32-, OPic -, OPiv -, SO 42-, ClO 4-, Br -) resulted in significant enhancement of complex photostability.

Fully protected glycosylated zinc (II) phthalocyanine shows high uptake and photodynamic cytotoxicity in MCF-7 cancer cells

Phthalocyanine photosensitizers are effective in anticancer photodynamic therapy (PDT) but suffer from limited solubility, limited cellular uptake and limited selectivity for cancer cells. To improve these characteristics, we synthesized isopropylidene-protected and partially deprotected tetra β-glycosylated zinc (II) phthalocyanines and compared their uptake and accumulation kinetics, subcellular localization, in vitro photocytotoxicity and reactive oxygen species generation with those of disulfonated aluminum phthalocyanine. In MCF-7 cancer cells, one of the compounds, zinc phthalocyanine {4}, demonstrated 10-fold higher uptake, 5-fold greater PDT-induced cellular reactive oxygen species concentration and 2-fold greater phototoxicity than equimolar (9 μm) disulfonated aluminum phthalocyanine. Thus, isopropylidene-protected β-glycosylation of phthalocyanines provides a simple method of improving the efficacy of PDT.

New phthalocyanines containing bulky electron rich substituents

Metal-free and metallophthalocyanines with four 9-anthroyl groups bound through ethylthio ester bridges on the periphery have been prepared. The new compounds were characterized by elemental analyses, 1 H NMR, IR, mass and UV-vis spectral data. The electronic spectra exhibit an intense π-π* transition of 9-anthroyl identity together with characteristic Q and B bands of the phthalocyanine core. Effect of metal ions on intensity of fluorescence spectra of phthalocyanine derivatives substituted with 9-anthroyl groups was investigated. The energy transfer to the phthalocyanine core and radiative decays of the 9-anthroyl emission and phthalocyanine core were examined.

Photophysical properties of a water-soluble adjacently substituted bisnaphthalophthalocyanine

Spectral properties of a water soluble metal free tetracarboxyphenoxy bisnaphthalophthalocyanine (3) were studied in water and organic solvents. It was found that in protic solvents, complex 3 was highly aggregated. The surfactant, Triton X100, and bovine serum albumin (BSA) do not effect disaggregation while cetyl trimethylammonium chloride (CTAC) caused the molecule to disaggregate. The fluorescence quantum yields were higher in the presence of CTAC. Studying the interaction of BSA with complex 3 using fluorometry revealed that BSA is highly quenched by the latter. A 1:1 stoichiometric binding ratio between BSA and the Pc was found. Triplet quantum yields in water containing CTAC were higher than in organic solvents.

Synthesis and photophysical properties of water-soluble dendrimers bearing a phthalocyanine core

Aggregation behaviors of phthalocyanine derivatives which have a dendritic structure were examined in an aqueous solution. We prepared the first- and second-generation dendrimers (WG1-PC and WG2-PC), having water-soluble substituents as a peripheral group, to be resolved in water. From spectroscopic measurement, WG2-PC acted in a monomeric manner, even in an aqueous solution, in contrast to WG1-PC, which exhibited spectra attributed to aggregation. This implies that a higher generation of water-soluble dendrimers can prevent a phthalocyanine core from forming an aggregation. The introduction of the second-generation dendrons to an aggregatable core may be effective to avoid self-aggregation and an undesirable deactivation process.

Synthesis and photobiological properties of novel silicon(IV) phthalocyanines axially modified by paracetamol and 4-hydroxyphenylacetamide

Two novel axial-disubstituted silicon(IV) phthalocyanines (compounds 1 and 2) have been prepared by introducing paracetamol (a common antipyretic analgesic) or its isomer 4-hydroxyphenylacetamide at the axial positions of silicon(IV) phthalocyanine, respectively. Their photophysical and biological properties have been examined. Both compounds are highly soluble and exhibit very similar absorption spectra in N, N-dimethylformamide, which is typical for non-aggregated phthalocyanines. Both compounds are photocytotoxic against HT29 human colon adenocarcinoma cells. Compound 2 shows a very high in vitro photodynamic activity, with the IC50 value down to 15 nM. In contrast, compound 1 exhibits a much lower in vitro photodynamic activity toward HT29 cells, which can be attributed to its higher aggregating trend in the biological medium and lower singlet oxygen quantum yield.

Electrochemical and in situ Spectroelectrochemical Properties of Phthalocyanines Bearing N-Benzyl-4-Phenyloxyacetamide Moieties

The general redox behaviour of phthalocyanines bearing N-benzyl-4-phenyloxyacetamide moieties (H2Pc, ZnPc, NiPc, CuPc, and CoPc) has been identified by cyclic voltammetry and differential pulse voltammetry on Pt in dimethylsulfoxide/tetrabutylammonium perchlorate. These measurements showed that the complexes indicate subsequent one-electron reduction and oxidation processes. Although the voltammetric measurements implied the association of the redox processes of some complexes with aggregation phenomenon, the complete evaluation of the aggregation effects by only these measurements was not possible. In situ UV-Vis spectroelectrochemical measurements enabled us to assign the ligand- and metal-based redox processes, and identify if the aggregation affects these processes. These measurements suggested that the redox processes of H2Pc, NiPc, and CuPc are coupled by aggregation phenomenon, while those of ZnPc and especially CoPc are not, probably due to the difference in their axial coordinating properties.

Synthesis, characterization, and photovoltaic properties of soluble TiOPc derivatives

We have synthesized soluble TiOPc derivatives containing alkoxy groups for use as additives in dye-sensitized solar cells (DSSCs). The DSSC devices containing these TiOPc derivatives exhibited short-circuit current densities of 8.49~10.04 mA/cm² and power conversion efficiencies of 2.73~3.62 % under AM 1.5 illumination and 100 mW/cm² irradiation.

Silicon-Phthalocyanine-Cored Fullerene Dendrimers: Synthesis and Prolonged Charge-Separated States with Dendrimer Generations

Silicon-phthalocyanine-cored fullerodendrimers with up to eight fullerene substituents (SiPc-n C(60); n=2, 4, and 8) have been synthesized. Photophysical properties of newly synthesized SiPc-n C(60) have been investigated by time-resolved fluorescence and transient absorption analysis with pulsed laser light. Laser photolysis measurements suggest the occurrence of a charge-separation process from (1)SiPc* to the C(60) subunits. The nanosecond transient absorption spectra in the near-IR region indicate that the lifetimes of the formed radical ion pairs are prolonged on the order of SiPc-8 C(60)>SiPc-4 C(60)>SiPc-2 C(60), which may be related to the electron migration among the C(60) subunits. The usefulness of SiPc-n C(60) as light-harvesting systems, evaluated as a ratio of the rates of charge recombination to those of charge separation, increases markedly with the dendrimer generation.

Preparation and in vitro photodynamic activities of novel axially substituted silicon (IV) phthalocyanines and their bovine serum albumin conjugates

Two novel axially substituted phthalocyanines, namely bis(4-(4-acetylpiperazine)phenoxy)phthalocyaninatosilicon (IV) (1) and its N-methylated derivative 2, have been synthesized. The dicationic phthalocyanine 2 is non-aggregated in water and exhibits good photophysical properties. The non-covalent BSA conjugates of these compounds have also been prepared. Compound 2 and the conjugate 2-BSA show extremely high photodynamic activities toward B16 melanoma cancer cell lines. The corresponding 50% growth-inhibitory (IC50) ratios are 33 and 38 nM, respectively.

Octasubstituted Metal-Free Phthalocyanine as Core of Phosphorus Dendrimers: A Probe for the Properties of the Internal Structure

The synthesis of a new family of phosphorus dendrimers built from an octasubstituted metal-free phthalocyanine core is described up to generation 5. This core is used as a sensor and a probe for analyzing the properties of the internal structure and the influence of each structural part (core, branches, surface) upon the whole structure. UV-visible spectra show both a hyperchromic and bathochromic effect on the Q-bands with increasing generation, indicating that the chromophore is more isolated, and that the dendritic shell mimics a highly polar solvent. There is no evidence for aggregation, except for generation 0, showing again the isolation of the core. However, the dendritic shell is permeable to aqueous acids and bases, as demonstrated by the reversible splitting of the Q-band in an acidic medium (neutral form of the phthalocyanine) and the single Q-band in a basic medium (dianionic form), even for generation 4. The fluorescence quantum yield for the neutral form increases with increasing generation. The dianionic form of generation 0 is poorly fluorescent, whereas generations 3 and 4 (G3 and G4) exhibit better fluorescence. The cores of G3 and G4 are highly sensitive optical sensors for H3O+ and OH-. These experiments are carried out in THF/water mixtures, and the influence of water on the structure has been checked. The hydrodynamic radius of generation 4 is measured by NMR diffusion (pulse gradient spin-echo) experiments. R(H) varies from 35.4 A at 4 mol % of water to 32.5 A at 64 mol % of water in THF, indicating the hydrophobic nature of these dendrimers.

Optically nonlinear energy transfer in light-harvesting dendrimers

Dendrimeric polymers are the subject of intense research activity geared towards their implementation in nanodevice applications such as energy harvesting systems, organic light-emitting diodes, photosensitizers, low-threshold lasers, and quantum logic elements, etc. A recent development in this area has been the construction of dendrimers specifically designed to exhibit novel forms of optical nonlinearity, exploiting the unique properties of these materials at high levels of photon flux. Starting from a thorough treatment of the underlying theory based on the principles of molecular quantum electrodynamics, it is possible to identify and characterize several optically nonlinear mechanisms for directed energy transfer and energy pooling in multichromophore dendrimers. Such mechanisms fall into two classes: first, those where two-photon absorption by individual donors is followed by transfer of the net energy to an acceptor; second, those where the excitation of two electronically distinct but neighboring donor groups is followed by a collective migration of their energy to a suitable acceptor. Each transfer process is subject to minor dissipative losses. In this paper we describe in detail the balance of factors and the constraints that determines the favored mechanism, which include the excitation statistics, structure of the energy levels, laser coherence factors, chromophore selection rules and architecture, possibilities for the formation of delocalized excitons, spectral overlap, and the overall distribution of donors and acceptors. Furthermore, it transpires that quantum interference between different mechanisms can play an important role. Thus, as the relative importance of each mechanism determines the relevant nanophotonic characteristics, the results reported here afford the means for optimizing highly efficient light-harvesting dendrimer devices.