The syntheses of amphiphilic antimony(V)-phthalocyanines and spectral investigation on their aggregation behaviors in aqueous and non-aqueous solutions

Syntheses of Water-Soluble Silver(II)-Phthalocyanines toward Optical Sensing for Thiol Detection

Water-soluble silver(II)-phthalocyanine complexes (AgPcs), tetrakis{4-(N-alkylpyridinium)thio}phthalocyaninato silver(II) tetrafluoroborate, [Ag(tRpySpc)](BF₄)₄, (R = Me and Et), have been synthesized for the first time by quaternization of pyridyl groups of tetrakis(4-pyridylthio)phthalocyaninato silver(II) by using Meerwein reagents and characterized by ESI-MS, elemental analyses, and optical absorption spectroscopy. Although they strongly aggregate in water, the presence of appropriate surfactants, such as polyethyleneglycol-monooleyl ether (n = approximately 50; PEG50) and sodium dodecyl sulfate, effectively disaggregates them to monomeric species. The spectral properties of the AgPcs and their aggregates in aqueous and nonaqueous solutions have been investigated by optical absorption, emission, and magnetic circular dichroism spectroscopy. These AgPcs rapidly react with thiols such as cysteine, glutathione, homocysteine, and sodium 2-sulfanylethanesulfonate (even on the order of 0.01 mM) in aqueous PEG50 solutions at room temperature to liberate the corresponding macrocyclic ligand, H₂Pc, but not with the other amino-acid analogs without sulfhydryl groups. The molar ratio of thiol to AgPc has been determined to be 1:1. Since AgPcs are essentially nonfluorescent at room temperature, while H₂Pcs emit intense red fluorescence, AgPcs can be a potent thiol-sensor toward bioimaging.

Solvent effects on molecular aggregation of highly water-soluble phthalocyanines

Molecular aggregation phenomena of a highly water-soluble, metal-free phthalocyanine, H[Formula: see text]Pc, and its copper complex, Cu(Pc); where Pc denotes tetrakis{(2[Formula: see text],6[Formula: see text]-dimethyl-4[Formula: see text]-sulfonic acid)phenoxy}phthalocyaninate) in water, ethanol, and their mixed solvent systems have been investigated by spectroscopic approach In both aqueous and ethanolic solutions, H[Formula: see text]Pc molecules aggregate in a slipped-cofacial manner, although very weakly in ethanol. On the other hand, Cu(Pc) molecules aggregate in a cofacial manner in water while aligning in a slipped-cofacial manner in ethanol. Magnetic circular dichroism spectroscopy was undertaken to investigate aggregation behaviors of Cu(Pc) in water and ethanol. Presence of 4-phenylpyridine in ethanol effectively inhibited aggregation of Cu(Pc) molecules, although little affected the spectra of the monomers. In a mixed solvent system, where water/ethanol [Formula: see text] 10/90 (v/v), Cu(Pc) is free from aggregation up to almost 10[Formula: see text] M. Driving forces of this molecular aggregation are discussed on the basis of [Formula: see text]–[Formula: see text] interaction and coordination chemistry involving copper ions.

Amphoteric phosphorous(V)-phthalocyanines as proton-driven switchable fluorescers toward deep-tissue bio-imaging

Spectral (optical absorption and emission) properties of three amphoteric phosphorous(V)-phthalocyanine derivatives, [P(Pc)(O)OH], where Pc=tetra(tert-butyl)phthalocyaninate (tbpc), tetrakis(2',6'-dimethylphenoxy)phthalocyaninate (tppc), and octakis(4'-tert-butylphenoxy)phthalocyaninate (obppc), have been investigated in ethanolic solutions. Spectral changes upon protonation/deprotonation (the reaction sites have been determined to be their axial ligands by magnetic circular dichroism study) are drastic and rapid. All the initial ([P(Pc)(O)OH]), protonated ([P(Pc)(OH)₂]⁺), and deprotonated ([P(Pc)(O)₂]^-) species are possessed with sufficient brightness (defined as the product of their molar extinction coefficient, ε (inM^-1cm^-1), and fluorescence quantum yield, Φ_F) in bio-imaging window (650-900nm). For example, spectral characteristics of the tbpc derivatives have been determined as follows: ε=1.65×10⁵ (absorption maximum 676nm) and Φ_F=0.80 (emission maximum 686nm) for [P(tbpc)(O)(OH)] while ε=1.45×10⁵ (697nm) and Φ_F=0.27 (714nm) for [P(tbpc)(OH)₂]⁺, and ε=2.25×10⁵ (662nm) and Φ_F=0.90 (667nm) for [P(tbpc)(O)₂]^-. Emission of tppc and obppc derivatives behave in essentially the same manner irrespective of nature of the peripheral substituents and hence Φ_F values are greater with increasing emission peak wavenumbers in line with the "energy gap law". These characteristics make these compounds promising candidates as chemical probes for deep-tissue bio-imaging.

Novel aqueous soluble cobalt(II) phthalocyanines of tetracarboxyl-substituted: Synthesis and catalytic activity on oxidation of sodium diethyldithiocarbamate

Enhancement of the catalytic activity of phthalocyanine catalysts by immobilizing them on polymer matrix has been studied. It has been found that the immobilization of cobalt(II) phthalocyanines on polymers enhances their catalytic activity in the oxidation of sodium diethyldithiocarbamate by air oxygen under mild conditions.

Synthesis, spectral and electrochemical properties of a novel phosphorous(V)-phthalocyanine

A novel phosphorous(V)-phthalocyanine, [ P ( tppc )( OH )( O )], where tppc denotes tetrakis{(2′,6′-dimethyl)phenoxy}phthalocyaninate, has been synthesized and its spectral properties in non-aqueous and aqueous media have been investigated. This compound has been found free from aggregation in EtOH whereas forms J-aggregates in CH 2 Cl 2 and acetonitrile, suggesting the presence of chemical interaction between the axial ligand and the surrounding solvent molecules. The most intense absorption band (Q-band) appears at 683 nm in EtOH , however, reaction with CF 3 COOH has given rise to a large red shift of the Q-band without lowering of its C 4 symmetry (evidenced by magnetic circular dichroism spectroscopy), indicating protonation at the axial site. Its fluorescence quantum yield has been determined (0.49 in EtOH ) and has been found much higher than those of the known Sb V or As V derivatives by more than one order of magnitude. The first reduction potential has been determined by cyclic voltammetry (-1.09 V vs. ferrocenium+/ferrocene) in CH 2 Cl 2. It is noteworthy that the Q-band maximum wavelength and the first reduction potential values are normal for conventional phthalocyanines despite the presence of pnictogen(V) in the cavity of the macrocyclic ligand.

Dissociation of imino proton(s) of a highly water-soluble metal-free phthalocyanine and determination of its pKa value in water

Dissociation of imino proton(s) in the cavity of the macrocycle of a highly water-soluble, metal-free phthalocyanine ( H 2( H 4 tsppc ); where H 4 tsppc denotes tetrakis{(2′,6′-dimethyl-4′-sulfonic acid)phenoxy}phthalocyaninate) in ethanolic and aqueous solutions has spectrophotometrically been investigated. The spectral changes associated with reaction with NaOH have been found to involve one-proton transfer process in aqueous media while two-protons process in ethanolic media. The acid-dissociation constant of the first imino proton in water (in the presence of Triton X-100) has been determined to be 12.5 ± 0.2 (as pKa) at 25 °C. The doubly deprotonated species in EtOH has been easily converted to its corresponding cobalt(II) derivative by thermal reaction with anhydrous CoCl 2.

Spectral study on one-electron-oxidized di(phthalocyaninato)rare-earths(III)

Nine double-decker bis(phthalocyaninato)rare-earth(III) complexes, [M(pc)2] (green radical species; M = Sc, Y, La, Pr, Sm, Eu, Tb, Ho, Yb ) have been electrochemically and spectro-electrochemically investigated in CH2Cl2 . All of them show one oxidation and three reduction waves, which involve phthalocyanine macrocycles. Apart from the lanthanum derivative, the first oxidation and reduction potentials show linear cathodic shift with an increase in ionic radius of the central metal (ri), whereas the second and third reduction little depend on ri. Electrochemical oxidation (around the oxidation potential) and chemical oxidation produced the same red~orange species (depending on the central metal). Their optical absorption spectra show three characteristic bands in 400~600, 600~750, and 800~1200 nm in visible and near-infrared region and their peak positions (in cm-1) linearly depend on ri (except for La). Assignment of these bands has been done based on magnetic circular dichroism spectroscopy and the electrochemical data.