Journal of Porphyrins and Phthalocyanines

A novel tetraazaporphyrinato and phthalocyaninato mixed heteroleptic double-decker sandwich rare-earth compound with photochromic and electrochromic features has been facilely synthesized by one-pot reaction using Eu(acac)₃·nH₂O, metal-free phthalocyanine H₂Pc′ (Pc′ = 2,3,9,10,16,17,23,24-octakis(decyloxy)phthalocyanine), and the photochromic precursor 1,2-dicyano-l,2-bis(2,3,5-trimethyl-3-thienyl)ethane as starting materials. The compound was well characterized by elemental analysis and various spectroscopic methods including UV-vis, IR, ¹H NMR, and mass spectroscopies. The electrochemical behavior of this compound was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods, which showed up to three one-electron oxidation and four one-electron reduction processes, demonstrating an electro-active compound for high-density information storage. The photochromic performance of the compound was detected by electronic absorption spectra, suggesting the compound to be a good candidate for non-destructive readout by means of UV-vis spectroscopy.

The synthesis of tetrasubstituted zinc phthalocyanines bearing quinolinoxy groups are reported for the first time. The new compounds have been characterized by elemental analysis, IR, MS and electronic spectroscopy. The photophysical properties, such as the electronic absorption spectra and fluorescence spectra, have also been investigated and discussed together with the influence of substituent position and organic solvents on these properties. The introduction of quinolinoxy group to the Pc ring was found to affect these photophysical properties to some extent.

The chiral mono-faced binaphthyl strapped porphyrins were synthesized and ¹H NMR characterized. Asymmetric epoxidation of olefins such as styrene derivatives and trimethylsilyl ethylene with iodosobenzene as oxidant was achieved by using the iron complex as catalyst in the presence of a nitrogen ligand. Enantiomeric excess (ee) of 80% and yield of 88% were measured for the epoxidation of styrene in the presence of 4-phenyl pyridine. The coordination capability of nitrogen ligands to catalysts measured by UV-vis spectrophotometric titrations evidence that the unstrapped face of the mono-faced catalyst is blocked by the nitrogen ligand coordination to the iron ion of the catalyst.

A series of mono-hydroxyl corrole bearing a fluorine (1), chlorine (2), bromine (3) and iodine (4) atom on its 10-phenyl group have been synthesized. Fluorescence spectroscopy shows that the halogen atom at meso-phenyl group of corroles exhibit significant heavy-atom effect on their photophysical properties. Fluorescence quantum yields and the lifetime of these corroles decrease with the increasing of the atomic weight of halogen atoms. The quenching of the fluorescence could be interpreted in terms of a heavy atom-induced increase in intersystem crossing from S₁ to T₁. The intersystem crossing rate constant of these corroles were also determined by transient fluorescence spectra.

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.

The UV-visible spectra and oxidation/reduction potentials for six octaethylporphyrins with first-row transition metal ions were measured in four non-aqueous solvents and then analyzed as a function of the Gutmann solvent parameters, donor number (DN) or acceptor number (AN). The utilized solvents were dichloromethane (CH₂Cl₂), N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and pyridine (py). The investigated porphyrins were (OEP)M, where OEP = the dianion of octaethylporphyrin and M = Co^II, Ni^II, Cu^II, Zn^II, Fe^IIICl or Mn^IIICl. UV-visible spectra upon solvent (S) binding to give (OEP)M(S) or [(OEP)M(S)₂]⁺Cl^- were monitored during a titration of the porphyrin in CH₂Cl₂ and formation constants (logβ_n, n = 1 or 2) for the ligand addition reactions were determined using standard equations. Five-coordinate (OEP)Co^II(S) and (OEP)Zn^II(S) are generated in CH₂Cl₂ solutions containing DMF, DMSO or py while six-coordinate [(OEP)Mn(S)₂]⁺Cl and [(OEP)Fe(S)₂]⁺Cl^- are formed under the same solution conditions. The magnitudes of the solvent binding constants are discussed in terms of both the solvent donor/acceptor properties and the electronegativity (EN) or stability index (SI) of the porphyrin central metal ion. A comparison between solvent binding constants measured in this study for (OEP)M and literature data for (TPP)M with the same central metal ions is presented.

Films with alternating layers containing anionic tetracarboxylic copper phthalocyanine [CuPc(COONa)₄] and cationic polydiallydimethylammonium chloride (PDDA) were fabricated by electrostatic self-assembled layer-by-layer (LBL) technique. The delicate structure of the film was characterized by a series of techniques. The third-order nonlinear optical properties of the film were measured by the Z-scan technique with laser duration of 4 ns and 21 ps at the wavelength of 532 nm. The film exhibited excellent nonlinear absorption and self-focusing effect. The second-order molecular hyperpolarizability γ value of the film was much larger than that of CuPc(COONa)₄ aqueous solution under the irradiation of whether ns or ps pulses. A series of damage experiments of the film for the intense laser pulses were conducted to prove the reliability of the experimental results under the conditions.

A novel industrial-scale trial for cyclohexane oxidation with air over metalloporphyrins as cytochrome P-450 monooxygenase model was reported. Upon addition of extremely low concentrations (1–5 ppm) of simple cobalt porphyrin to the commercial cyclohexane oxidation system, and decrease of the reaction temperature and pressure about 20 °C and 0.4 MPa respectively, the conversion rate of the cyclohexane oxidation increased from 4.8% to 7.1%, the yield of cyclohexanone raised from 77% to 87%, and a 70,000-ton cyclohexanone equipment set yielded an output of 125,000 tons cyclohexanone. Furthermore, a novel biological-chemical-cycle coupling mechanism was proposed to rationalize the aerobic oxidations of hydrocarbons catalyzed by the metalloporphyrins.

The phthalocyanine salt [ZnPc(NMe₃)₄]I₄ was synthesized from 4-nitrophthalonitrile using a three-step procedure. The interaction of [ZnPc(NMe₃)₄]⁴⁺ with calf thymus DNA (CT DNA) has been investigated by UV-vis and fluorescence spectrometric methods. [ZnPc(NMe₃)₄]⁴⁺ exists in a non-monomeric form, proposed to be a dimer, in phosphate buffer solution (pH 6.82). Spectral changes show that in the presence of high concentrations of CT DNA added to the solution, [ZnPc(NMe₃)₄]⁴⁺ is bound in a monomeric state with evidence suggesting it is located in a DNA groove. At lower concentrations of DNA there is evidence of stacking of non-monomeric [ZnPc(NMe₃)₄]⁴⁺ onto the DNA. Two intrinsic binding constants for the interaction of [ZnPc(NMe₃)₄]⁴⁺ with CT DNA, 1.33 × 10⁵ and 2.56 × 10⁴ M^-1 have been obtained. Electrostatic binding is shown to play an important role in the interaction of [ZnPc(NMe₃)₄]⁴⁺ with nucleic acids.