Journal of Porphyrins and Phthalocyanines

Fullerene C₇₀ and covalently linked porphyrin (Fe^IIITPP)₂O dimers (TPP: tetraphenylporphyrin) form molecular complex {(Fe^IIITPP)₂O}·C₇₀ (1). Each C₇₀ molecule is sandwiched between two (Fe^IIITPP)₂O dimers and is surrounded by phenyl groups of four other porphyrin dimers. At 295 K, C₇₀ molecules freely rotate about the short axis of the molecule in the ab plane. As a result, the disordered C₇₀ molecules form spheroids flattened at the poles. The rotation of C₇₀ stops near 100 K, resulting in the transition from a tetragonal to a monoclinic unit cell with a four-fold increase in the unit cell volume. In monoclinic phase the C₇₀ molecules are located on the axis which coincides with the short axis of the molecule and passes through the midpoints of two oppositely located 6-6 bonds. Since this position has higher symmetry than the own symmetry of C₇₀, it results in statistic disorder of the C₇₀ molecules between two orientations. It was shown that multiple Van der Waals contacts with a concave Fe^IIITPP macrocycle which appear below 100 K, play an important role in the ordering of C₇₀.

The synthesis and spectroscopic studies of metalloporphyrin dimers having 1,3-butadiyne linker attached to the beta pyrrolic positions of the linked porphyrins are reported. Bromoethenyl metalloporphyrins were synthesized by zirconocene-promoted bromomethylenation of beta formyl metalloporphyrins. Bromoethenyl metalloporphyrins were dehydrohalogenated by potassium tert-butoxide to give beta ethynyl or 2-ethynyl metalloporphyrins. It is the first documented example of zirconocene-promoted bromomethylenation of beta formyl metalloporphyrins. Bromoethenyl metalloporphyrins were also synthesized by halo-Wittig route. 2-ethynyl metalloporphyrins were self dimerized to give metalloporphyrin dimers having 1,3-butadiyne linking bridge. FTIR, Raman spectroscopy, UV-visible, elemental analysis, ¹H NMR and mass spectrometry were used to characterize the compounds.

The interaction of nickel(II) complex of cationic porphyrins bearing five-membered rings, meso-tetrakis(1,2-dimethylpyrazolium-4-yl)porphyrinatonickel(II) (NiPzP), with synthetic polynucleotides poly(dG-dC)₂ and poly(dA-dT)₂ has been characterized by viscometric, visible absorption, CD and MCD spectroscopic, and melting temperature measurements. The nickel(II) complex NiPzP is intercalated into poly(dG-dC)₂ but outside bound to the major groove of poly(dA-dT)₂. The binding constants of NiPzP to poly(dG-dC)₂ and poly(dA-dT)₂ are in the order of 10⁶ M^-1 and comparable to those of other reported cationic metalloporphyrins. The binding process of NiPzP to poly(dG-dC)₂ and poly(dA-dT)₂ is endothermic and entropically driven.

We will present resonant two-photon ionization spectra for meso-tetraphenylporphyrin, H₂TPP, measured under isolated conditions. The polycrystalline compound was vaporized, in vacuo, using both thermal and laser desorption, and seeded into a supersonic expansion of an inert-carrier gas. The molecules remain largely intact in the gaseous phase. However, the two techniques for vaporizing H₂TPP give different internal temperatures for the isolated substrate, with greater vibrational cooling achieved using laser desorption. A comparison of the peak positions and intensities in the resonant two-photon ionization spectra of thermal- and laser-desorbed molecules provides an insight into the vibrational structure of the Q band. In particular, the greater contribution made by electronic transitions originating from higher vibrational levels in the ground state of H₂TPP is emphasized. We conclude that vibronic coupling in the ground electronic state plays an important role in a quantum-mechanical interpretation of the Q band.

The synthesis of novel μ-nitrido diiron phthalocyanine with electron-withdrawing substituents is reported: μ-nitrido tetra-methylsulfonylphthalocyanine (13), μ-nitrido tetra-ethylsulfonylphthalocyanine (14), μ-nitrido tetra-adamantylsulfonylphthalocyanine (15), μ-nitrido tetra-cyclohexylsulfonylphthalocyanine (16). These complexes were characterized by ESI-MS, UV-vis, FT-IR and EPR techniques. The state of these complexes depends on the size of the substituents. Complexes 13 and 14 bearing small methylsulfonyl and ethylsulfonyl substituents are cationic (PcFe^IVNFe^IVPc)⁺N₃^- complexes while complexes 15 and 16 with bulkier adamantylsulfonyl and cyclohexylsulfonyl substituents are formally neutral PcFe^IIINFe^IVPc complexes which can be represented as PcFe(+3.5)NFe(+3.5)Pc.

TPPMnOAc and four different kinds of manganese tetraphenylporphyrin acetates were synthesized using different numbers of methoxy substituents in various positions of the phenyl rings. These porphyrins were used as catalysts in the epoxidation of various alkenes with tetra-n-butylammonium hydrogen monopersulfate (n-Bu₄NHSO₅) as the oxidant and imidazole as the axial base. The following order of catalytic activity was obtained: TPPMnOAc ≥ T(2,3-OMeP)PMnOAc > T(4-OMeP)PMnOAc > T(3,4-OMeP)PMnOAc > T(2,4,6-OMeP)PMnOAc. By studying the UV-vis spectra in the reaction solution, the stability of the applied methoxy porphyrins and the effect of this factor on obtained yields were investigated. Lower catalytic activity in some of the methoxy porphyrins emphasized steric effects and special hydrogen bonding among the reaction elements. However, the stability of T(2,3-OMeP)PMnOAc under our reaction condition was considerable and high activity was observed. By adding small amounts of alcohol to the reaction solution, the effect of the solvent mixture was previewed and steps were taken to identify the active intermediate of the catalyst in these conditions.

The complex μ-oxo-bis[tetrakis(thiadiazole)porphyrazinato-aluminum(III)], [(TTDPzAl)₂O], has been obtained from the corresponding mononuclear Al(III) hydroxo-complex, [TTDPzAlOH], by refluxing a solution of this latter in α-chloronaphthalene or by heating the solid hydroxo species (250–300 °C) under vacuum (10^-2 mmHg). The complex, which appears as a stable species in air, shows a typical IR absorption at 983 cm^-1, assigned as ν_as(Al-O-Al). Contact with water determines disappearance of this absorption consequent to the formation of the related hydroxide. [(TTDPzAl)₂O], insoluble in most organic non-donor solvents, and very scarcely soluble in dimethylsulfoxide and dimethylformamide, shows some instability in pyridine, with probable breaking of the μ-oxo bridge and formation of the mononuclear hydroxide. Single crystals suitable for X-ray analysis were obtained by subliming [(TTDPzAl)₂O] under vacuum at 500 °C under a continuous N₂ flow. Crystal data for [(TTDPzAl)₂O], C₃₂Al₂N₃₂OS₈: a = 7.613(2) Å, b = 11.280(2) Å, c = 23.363(5) Å, β = 96.869(3)°, space group P2₁/c (n. 14), U = 1991.9(7) ų, Z = 2, R(F)^a = 0.0492, wR(F²) = 0.1024. The μ-oxo bridged complex has a central linear Al-O-Al bond system, with the Al(III) atoms displaced out of the respective N₄ square planar coordination sites by 0.441 Å and the two TTDPz planes lying in an eclipsed position, the overall structure of the complex approaching closely that of the related phthalocyaninato complex [(PcAl)₂O]. Intermolecular contacts, instead, are definitely different for the two species, the type found present in [(TTDPzAl)₂O] highly reminiscent of those of other previously reported "thiadiazoleporphyrazine" macrocycles, with the observed short inter-unit contacts between adjacent TTDPz macrocycles again determined by the presence in the TTDPz framework of the annulated peripheral (S, N)-containing heterocycles.

In the present study, the activity of the new water-soluble cationic meso-tetra(4-N-oxyethylpyridyl)porphyrin and its Zn, Ag and Co metal derivatives as anti-tumor agents was explored. The tumor was induced by 7,12-dimethylbenz[a]antracene (DMBA) on rats of Wistar strain. The levels of DNA damage induced by porphyrins T4OEPyP, AgT4OEPyP, ZnT4OEPyP and CoT4OEPyP in tumor tissue were analyzed. Thermodynamic parameters of DNA were investigated by thermal melting method and differential scanning microcalorimetry to understand the differences in DNA structure of three types of rat: normal, dieseased with tumor, and treated by porphyrins. Agarose gel electrophoresis method was used to detect porphyrin-induced apoptosis or necroses. Based on the data obtained, we concluded that the investigated ZnTOEPyP and AgTOEPyP porphyrins have more anti-tumor activity than CoTOEPyP and TOEPyP.

The association behavior of tetrakis(N, N′, N″, N‴-tetramethyl tetra-2,3-pyridino)porphyrazine copper(II) ([Cu(II) 2,3-tmtppa]⁴⁺) was investigated in aqueous solutions at 25 °C and various ionic strengths using optical absorption and resonance light scattering (RLS) spectroscopies. The results show that ([Cu(II) 2,3-tmtppa]⁴⁺) does not have any affinity for aggregation due to increasing of salt concentration and exists as monomers even in homogeneous aqueous solutions of high ionic strengths (more than 1 M NaCl). Interaction of ([Cu(II) 2,3-tmtppa]⁴⁺) with calf thymus DNA has also been studied in 1 mM aqueous phosphate buffer of pH 7.0, by optical absorption and RLS spectroscopies, and thermal denaturation experiments. The appearance of hypochromicity of less than 10% and bathochromicity shift of Δλ ≤ 2 nm in UV-vis spectra of ([Cu(II) 2,3-tmtppa]⁴⁺), increasing of thermal melting point of DNA, and no change in RLS spectra of porphyrazine due to interaction with DNA, represent the minor outside groove binding mode without any stack aggregate formation. The thermodynamic of the binding of ([Cu(II) 2,3-tmtppa]⁴⁺)-DNA also has been studied. The binding constant (K) was obtained by analysis of the optical absorption spectra of the complex at various DNA concentrations using SQUAD software. The value of K was estimated to be 2.34 × 10⁵ ± 0.06 M^-1 at 25 °C. The thermodynamic parameters were calculated by van't Hoff equation. The enthalpy and entropy changes were 41.83 ± 3.28 kJ/mol and 242.08 ± 9.88 J/mol.K at 25 °C, respectively. The results indicate that the process is entropy-driven and suggest that hydrophobic interactions are the main driving forces for the complex formation. Increasing of the ionic strength due to addition of NaCl destabilized porphyrazine-DNA complexes, indicating the competition of Na⁺ ions with porphyrazine complexes for occupation of minor groove binding sites.

Sn(IV) porphyrins are highly desirable for various applications because of their stability, their preference for oxygen-donor ligands and because they possess properties which can be easily characterized using various spectroscopic techniques. The most established method for the preparation of the Sn(IV) porphyrins is refluxing the porphyrin with SnCl₂·2H₂O in pyridine as solvent. Although this method works efficiently, we found that the work-up results in a lot of unwanted materials and using large quantities of pyridine as solvent is not good under laboratory conditions. In this paper, we show that the Sn(IV) porphyrins can be prepared easily by treating porphyrin with SnCl₂·2H₂O in chloroform, dichloromethane and toluene as solvent containing 25–50% ethanol as co-solvent. The reaction works smoothly and involves simple work-up and straightforward chromatographic purification. The method works efficiently for meso and β-substituted porphyrins. The spectral and electrochemical properties of various Sn(IV) were studied and our studies showed that the properties are sensitive to the nature of substituent present at the meso-position.