Journal of Porphyrins and Phthalocyanines

In this study, the synthesis of a supramolecular hexaphthalocyaninato hexazinc(II) with hexylthio substituents is reported. Starting from 5,11,17,23-tetra-tert-butyl-25,27-dihydroxy-26,28-dimethoxycalix[4]arene, mononitro derivative of calix[4]arene 1 was obtained. Compound 1 was converted to phthalodinitrile derivative 2 by the reaction with 4-nitrophthalonitrile in dry dimethylsulfoxide by the method of nucleophilic substitution of an activated nitro group in an aromatic ring. The tetramerization of compound 2 with Zn(OAc)₂·2H₂O in 1-pentanol gave the novel ball-type binuclear zinc (II) phthalocyanine 3 which was reacted with unsymmetric zinc(II) phthalocyanine 4 to furnish a supramolecular assembly of a zinc(II) phthalocyanine of a ball type with four zinc(II) phthalocyanines through azo bridges, 5. Newly synthesized compounds were characterized by elemental analysis, UV-vis, IR, MALDI-TOF MS and ¹H NMR spectra. The electrochemical and spectroelectrochemical properties of 5 were also examined in nonaqueous media. The measurements showed the formation of various mixed-valence oxidation and reduction species, due to the strong intramolecular interactions between the Pc rings. Both DC and AC conductivity data were analyzed by the existing theory.

Spectral, photophysical, photochemical and bovine serum albumin binding studies on some gallium(III) derivatives - {1,(4)-(tetrapyridyloxyphthalocyaninato)gallium(III), (αGaPc); 2,(3)-(tetrapyridyloxyphthalocyaninato)gallium(III), (βGaPc); and their quaternized derivatives: QαGaPc and QβGaPc)} are hereby presented. β-Substituted complexes are more fluorescent, but show lower tendencies to undergo intersystem crossing than the α-substituted, as judged by their fluorescence and triplet quantum yield values. The quaternized derivatives (QGaPc) are water-soluble and non-aggregated, which makes them potential photosensitizers of choice for photodynamic therapy applications; these amphiphilic compounds also bind strongly to bovine serum albumin in 1:1 stoichiometries, and with binding constants (K_b) in the order of 10⁶ M⁻¹.

Three photosensitizers based on tris-(pentafluorophenyl)antimony corroles that differ in oxidation state and axial ligands, namely, (pyridine)Sb(III)-, (oxo)Sb(V)- and (difluoro)Sb(V) complexes, were studied by time-resolved electron paramagnetic resonance spectroscopy and laser flash photolysis. The magnetic and orientational parameters of the corroles oriented in a nematic liquid crystal as well as their triplet lifetimes in liquid toluene were determined and interpreted in terms of their structure and geometry. The negative zero-field splitting parameter D assigned to all studied corroles is explained by the asymmetric π-electron withdrawal effect caused by perfluorinated peripheral aryl groups, which force the triplet electron spins to align in head-to-tail configuration. The effect of the axial ligands on the photoexcited triplet state properties of the corroles is correlated with their different efficiency to perform photoassisted aerobic oxygenation of some organic molecules. This is explained by the dependence of the main parameters of the photoexcited complexes on the interaction between the central ion and corrole π-system. This interaction is strongly influenced by axial ligands coordination, affecting the macrocycle symmetry, planarity, and rigidity.

This work presents complete vibrational analysis of a chloride complex of Ni(II) 4,12-ditolyl-16,24-diphenyl-3-thiaporphyrin (SDTDPPNi(II)Cl) and its isotopic derivatives (⁶¹Ni(II), −d₆, and −d₁₀). Five-coordinate SDTDPPNi(II)Cl, SDTDPP⁶¹Ni(II)Cl, (SDTDPP-d₆)Ni(II)Cl, and (SDTDPP-d₁₀)Ni(II)Cl were investigated by Fourier-Transform infrared (FT-IR), resonance Raman (RR), and electronic absorption (UV-vis) methods. Because the methyl groups of tolyl rings at the para-position have negligible influence on geometry and vibrational spectra of SDTDPPNi(II)Cl, they can be treated as point groups. Thus, geometry optimization and vibrational frequencies were calculated for the 4,12,16,24-tetraphenyl-3-thiaporphyrin (STPPNi(II)Cl) model molecule and its isotopically labeled analogs using Gaussian'03. Moreover, charge distributions (General Atomic Polar Tensor – GAPT) and geometrical aromaticity indexes (Bird's I₅ and Harmonic Oscillator Model of Aromaticity – HOMA) were calculated. All theoretical calculations were performed at the B3LYP level with the LANL2DZ basis set. As is shown, the experimental FT-IR and RR spectra for each compound are reproduced well by the corresponding theoretical spectra.

The synthesis and spectroscopic characterization of two new substituted tetraphenyl-porphyrins with one or two benzo-9-crown-3 appended units are described.

Electron-deficient metallocomplexes of dodeca- and octanitroporphyrins produced by the introduction of 8 β-nitro substituents or 8 β-nitro and a meta-nitro substituent on each meso-aryl ring of Zn(II) and Ni(II) [meso-tetra-(2,6-dichlorophenyl)porphyrin] (Zn8, Ni8 and Zn12, Ni12, respectively) and their air-stable reduced species have been characterized by steady-state absorption and Soret-excited resonance Raman spectroscopies. One-electron reduced species of the metallocomplexes were produced by three different procedures (in deprotonated tetrahydrofuran in air ambient, in tetralhydrofuran with the addition of piperidine in air ambient, and in contact with a sodium mirror under vacuum) and demonstrated similar absorption and RR spectra. It is concluded on the basis of the RR spectra that the one-electron reduction products of the studied polynitrosubstituted metalloporphyrins are π–anion radicals in character.

The effects of weakly coordinating anions, BF₄, AsF₆ and SbF₆, as axial ligands on the formation and coordination chemistry of heme analogues have been examined. Three new five-coordinate and stable iron(III) heme analogues, OEPFeX, where OEP is the dianion of octaethylporphyrin and X = BF₄, AsF₆ and SbF₆, have been isolated. The compounds have been characterized by different spectroscopic methods as well as elemental analysis. ¹H NMR spectroscopy and magnetic moment measurements show that the OEPFeX are paramagnetic and iron is five-coordinate. In addition, monoimidazole ferric-porphyrin complex, OEPFe(Im)(SbF₆) has been prepared in solution, by starting with OEPFe(SbF₆). The electrochemical properties of OEPFeX (X = BF₄, AsF₆, SbF₆) have been studied by cyclic voltammetry and differential pulse polarography.