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.

Spectral investigation of phthalocyanine complexes of high-valence silver and their aggregates.

Several novel silver(II) complexes ligating a tetra-substituted phthalocyaninate, [Ag(tbpc)] (where tbpc denotes tetra-tert-butylphthalocyaninate), [Ag(tppc)] (tppc = tetrakis(2,6-dimethylphenoxy)phthalocyaninate), [Ag(tObpc)] (tObpc = tetra-n-butoxyphthalocyaninate), and [Ag(tpySpc)] (tpySpc = tetrakis(4-pyridylthio)phthalocyaninate) have been synthesized and characterized by elemental analyses, MALDI-TOF MS, optical absorption, and magnetic circular dichroism (MCD) spectroscopy. Although all the compounds are well soluble in common organic solvents, concentration studies on their optical spectra in solutions have found that they are prone to strongly aggregate in a cofacial manner (i.e., H-aggregate). Silver(II) complexes, which are essentially non-fluorescent, are readily demetallated in the presence of appropriate reductant (e.g., I- or BH4-) to liberate the corresponding macrocyclic ligand, which emits intense red fluorescence. Chemical oxidation by using NOBF4 generates the corresponding silver(III) species.

Soft chromophore featured liquid porphyrins and their utilization toward liquid electret applications.

Optoelectronically active viscous liquids are ideal for fabricating foldable/stretchable electronics owing to their excellent deformability and predictable π-unit-based optoelectronic functions, which are independent of the device shape and geometry. Here we show, unprecedented 'liquid electret' devices that exhibit mechanoelectrical and electroacoustic functions, as well as stretchability, have been prepared using solvent-free liquid porphyrins. The fluidic nature of the free-base alkylated-tetraphenylporphyrins was controlled by attaching flexible and bulky branched alkyl chains at different positions. Furthermore, a subtle porphyrin ring distortion that originated from the bulkiness of alkyl chains was observed. Its consequences on the electronic perturbation of the porphyrin-unit were precisely elucidated by spectroscopic techniques and theoretical modelling. This molecular design allows shielding of the porphyrin unit by insulating alkyl chains, which facilitates its corona-charged state for a long period under ambient conditions.

Observation of the First Spin Crossover in an Iron(II) Complex with an S6 Coordination Environment: Tris[bis(N,N-diethylamino)carbeniumdithiocarboxylato]iron(II) Hexafluorophosphate.

For the first time, the spin-crossover (SCO) phenomenon has been observed in an FeII -S6 system in a tris(chelate)-type iron(II) complex with a zwitterionic sulfur donor bidentate, bis(N,N-diethylamino)carbeniumdithiocarboxylate (EtL), [FeII (EtL)3 ](PF6 )2 (1), as synthesized by the reaction of a precursor complex [FeII (CH3 CN)6 ](PF6 )2 with EtL. In the solid state, the high-spin (HS) d6 state at ambient temperature and the low-spin (LS) d6 state at temperatures lower than approximately 240 K were evidenced by magnetic measurements with SQUID and Mössbauer spectra in the temperature range 4-290 K. X-ray analyses of the crystals at various temperatures disclosed that the distorted trigonal prismatic coordination environments essentially do not change; however, contraction of Fe-S distances by approximately 10 % (0.22 Å), ordering of alkyl groups in EtL and PF6 - counteranions, and formation of significant intermolecular S⋅⋅⋅S interactions between adjacent molecules (average distances of 3.59 Å) take place during the transition from the HS to the LS state. A large decrease in the volume of the formula unit (78.1 Å3 ) might be responsible for the large activation barrier, thereby resulting in a slow phase transition upon cooling.

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, ΦF) 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 ΦF=0.80 (emission maximum 686nm) for [P(tbpc)(O)(OH)] while ε=1.45×105 (697nm) and ΦF=0.27 (714nm) for [P(tbpc)(OH)2]+, and ε=2.25×105 (662nm) and ΦF=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 ΦF 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.

The synthesis and spectral investigation of a novel highly water-soluble, aggregation-free antimony(V)-phthalocyanine absorbing light in optical therapeutical window.

A novel antimony-phthalocyanine, [Sb(H(3)tsppc)(OH)(2)], where H(3)tsppc denotes monodeprotonated tetrakis{(2',6'-dimethyl-4'-sulfonic acid)phenoxyl}phthalocyaninate, has been synthesized through sulfonation of [Sb(tppc)(OH)(2)](+) (tppc denotes tetrakis{(2',6'-dimethyl)phenoxyl}phthalocyaninate) in concentrated sulfuric acid. This compound is highly soluble in water (ca. 4 × 10(-2) M) without surfactant or alcohol. Moreover, it has been found free from aggregation in water up to almost 10(-4) M, unlike its copper and metal-free analogues, and show an intense optical absorption and emission band in optical therapeutical window (700-800 nm). The axial hydroxyl groups play a crucial role in disaggregation of the antimony derivative in water.

Synthesis, spectral, and electrochemical characterization of the first arsenic(V)-phthalocyanines.

The first arsenic(V)-phthalocyanines, [As(tbpc)X(2)](+), where tbpc denotes tetra(tert-butyl)phthalocyaninate, C(48)H(48)N(8)(2-) and X = F, Cl, and Br) have been prepared through an appropriate oxidative addition process to a highly soluble arsenic(III) derivative, [As(tbpc)](+). Among them, [As(tbpc)F(2)](+) has been isolated as PF(6)(-) salt. Unlike conventional metal derivatives of phthalocyanines, they show a significantly red-shifted (by >1000 cm(-1)) Q-band and facile reduction of the macrocyclic ligand (redox potentials for [As(tbpc)F(2)](+) have been determined by cyclic voltammetry; 1.13 V vs ferricinium(+)/ferrocene (tbpc(-/2-)), -0.45 V (tbpc(2-/3-)), and -0.90 V (tbpc(3-/4-)), of which the values are anodically shifted by about 1 V) as compared to those of conventional phthalocyanines. Although the anomaly in their spectral and electrochemical properties is similar to that of the known antimony analogues, the arsenic-phthalocyanines have been found less stable.

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

Three amphiphilic antimony(V)-phthalocyanines have been synthesized by treating [Sb(R(4)Pc)(OH)(2)](+) salts in concentrated H(2)SO(4) and isolated as zwitter ions, [Sb(R(4)Pc)(SO(4)H)(SO(4))], where R(4)Pc denotes tetra-substituted phthalocyaninate; R(4)Pc=pc (R=H), tbpc (R=(t)Bu), and tObpc (R=O(n)Bu). Their solubility (R=tbpc>pc >>tObpc in H(2)O (much improved by the presence of surfactant or alcohol) while tbpc>tObpc >>pc in CH(2)Cl(2)) and aggregation behaviors are highly sensitive to the nature of the peripheral substituents. The pc and tbpc derivatives form well-behaved J-aggregates in aqueous media in the presence of surfactant or alcohol.

Synthesis and properties of a highly soluble dihydoxo(tetra-tert-butylphthalocyaninato)antimony(V) complex as a precursor toward water-soluble phthalocyanines.

The title complex cation, [Sb(tbpc)(OH)(2)](+) (where tbpc denotes tetra(tert-butyl)phthalocyaninate, C(48)H(48)N(8)(2-)), has been prepared by oxidizing [Sb(tbpc)]I(3) with tert-butyl perbenzoate in CH(2)Cl(2), CHCl(3), o-dichlorobenzene and also without solvent in the range of 20-80 degrees C. This species has been isolated as I(3)(-) salt and characterized by elemental analysis, ESI-MS, FT-IR, optical absorption and emission, and magnetic circular dichroism spectroscopy. This compound is quite well soluble in common polar organic solvents (e.g., CH(2)Cl(2), acetonitrile, acetone) without detectable aggregation at least up to ca. 10(-4)M while much less soluble (e.g., benzene, chloronaphthalene) or insoluble (hexane) in non-polar solvents. Although this compound is insoluble in water, it makes hydrophilic colloids in acetone-water mixtures. The most intense absorption band (Q-band) in a specific solvent red-shifts with an increase in the refractive index of the solvent. However, considerable deviation of the Q-band positions in donor-solvents from linear correlation between the positions and Onsager's solvent polarity function suggests that there are significant specific chemical interactions between the axial hydroxyl groups and the surrounding donor molecules. The low fluorescence quantum yield (ca. 0.01) for [Sb(tbpc)(OH)(2)](+) suggests that the singlet excited state of this species is considerably quenched by the presence of antimony ion in the chromophore.

Spectral properties of a novel antimony(III)-phthalocyanine complex that behaves like J-aggregates in non-aqueous media.

An unusual red-shift of phthalocyanine Q-band upon aggregation in non-aqueous media has been observed for antimony(III) derivative and has been studied by using optical absorption and magnetic circular dichroism spectroscopy.

An Adjacent Dibenzotetraazaporphyrin: A Structural Intermediate between Tetraazaporphyrin and Phthalocyanine.

An adjacent dibenzotetraazaporphyrin, in which two benzene units are fused to the adjacent pyrrole rings of tetraazaporphyrin skeleton, has been synthesized as a copper complex for the first time and characterized by electronic absorption and magnetic circular dichroism spectroscopy, by cyclic voltammetry and spectroelectrochemistry using an optically transparent thin layer electrochemical cell. The results were compared with those of tetraazaporphyrin and phthalocyanine analogues. The title compound shows intermediate characteristics between those of normal tetraazaporphyrins and phthalocyanines; the Q-band shifts to the red and becomes more intense while the Soret band broadens with increasing the size of the pi-system. With the expansion of the pi-system, the first reduction potential does not change significantly, while the first oxidation potential shifts negatively, indicating that the LUMO level remains almost constant while the HOMO level destabilizes significantly. These spectroscopic properties and redox potentials were reproduced by molecular orbital calculations within the framework of the Pariser-Parr-Pople approximation. Thermogravimetry analysis suggests that the skeleton of the adjacent dibenzotetraazaporphyrin complex decomposes at about 95 degrees lower than that of the tetra-tert-butylated phthalocyanine analogue.