Acid–Basic Properties of Al(III), Ga(III), and In(III) Complexes with Octaphenyltetraazaporphine

Al(III), Ga(III), and In(III) complexes with octaphenyltetraazaporphine and halide axial ligands of the composition [(X)MTAP] (X = F, Cl, Br) and In(III) complexes with bidentate ligands of the composition [(Y)InTAP] (Y = nitrite (NO₂) and 2,3-naphthodiolate (NpO₂)) were synthesized. The acid–basic properties of the complexes were studied in the proton-donor media and the concentration stability constants of the acidic forms obtained at the first protonation stage were determined. The effect of the nature of a metal and extra ligand on the basic properties of meso-nitrogen atom in macrocyclic ligand was discussed.     

Manganese Complexes with Octaphenyltetraazaporphine: Acid–Base Interactions and Kinetic Stability in Proton-Donor Solvents

Complexes of manganese(III) and manganese(V) with octaphenyltetraazaporphine (H₂OPTAP) were synthesized. Acid–base interactions of these complexes in the CH₂Cl₂–CF₃COOH system and kinetics of their dissociation in concentrated sulfuric acid, as well as kinetics of octaphenyltetraazaporphine destruction in sulfuric acid solutions were studied by spectrophotometric methods. Acid–base interactions in CH₂Cl₂–CF₃COOH were shown to involve two macrocyclic meso-nitrogen atoms in succession. Concentration stability constants of the acid forms obtained pK ₁ = 0.29 ± 0.01 and pK ₂ = –0.62 ± 0.08 for (chlorine)manganese(III)octaphenyltetraazaporphine ((Cl)MnOPTAP); pK ₁ = 0.99 ± 0.02 and pK ₂ = – 0.70 ± 0.03 for (nitrido)manganese(V)octaphenyltetraazaporphine ((N)MnOPTAP). The rate of dissociation of the complexes in 94–98% H₂SO₄ does not depend on the acid concentration. The manganese(V) complex is three times as stable as the manganese(III) complex.     

Tetrakis(thiadiazolo)porphyrazines. 3. Acid-base Properties and Stability of Tetrakis-3,4-(1,2,5-thiadiazolo)porphyrazine in Sulfuric Acid Solutions

AM1 calculations gave the proton affinities of different types of donor sites in tetrakis-3,4-(1,2,5-thiadiazolo)porphyrazine, H₂{[SN₂)₄PA}, and protonation of the meso-nitrogen atoms was found to be favored. A spectrometric study showed that the basicity of the meso-nitrogen atoms of the porphyrazine macrocycle is strongly diminished and these atoms in CF₃CO₂H are involved in an incomplete acid-base interaction (ABI) to give acid solvates, while a complete ABI (protonation) is found only in the presence of sulfuric acid. The basicity constants of the meso-nitrogen atoms were determined spectrophotometrically in CF₃CO₂H-H₂SO₄. The kinetics of decomposition of the macrocyclic chromophore in concentrated sulfuric acid was studied and a possible mechanism for this process was proposed.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 278–287, February, 2005.     

Synthesis and spectroscopic study of tert-butyl-substituted benzoporpyrazines with fused 1,2,5-thiadiazole fragments

Cross cyclotetramerization of 1,2,5-thiadiazole-3,4-dicarbonitrile and 4-tert-butylphthalodinitrile in the presence of magnesium butoxide gave a mixture of symmetric and asymmetric porphyrazine magnesium(II) complexes. One of these, (2²⁽³⁾,7²⁽³⁾,12²⁽³⁾-tri-tert-butyltribenzo[b,g,l][1,2,5]thiadiazolo[3,4-q]-5,10,15,20-tetraazaporphyrinato)magnesium(II) (MgSBBB), was isolated by column chromatography and was treated with trifluoroacetic acid to obtain the corresponding free ligand (H₂SBBB). The effect of the mode of heteroring fusion on the electronic absorption spectra of tribenzoporphyrazines was studied.     

Rhodium(III) and Iridium(III) Complexes with Octaphenyltetraazaporphine: Synthesis and Study of Their Acid Forms in Proton-Donor Media

The Rh(III) and Ir(III) complexes with octaphenyltetraazaporphine (X)MOPTAP (M = Rh, X = HSO₄, OH; M = Ir, X = HSO₄) are synthesized and their specific acid–base interactions in the CF₃COOH–CH₂Cl₂ and H₂SO₄–CH₃COOH systems are studied. The quantitative characteristics of equilibria between the acid and basic forms are obtained. The stability constants K ₁ of the first acid forms, in which one of the meso-N atom is protonated, for hydrosulfate (HSO₄)MOPTAP complexes in the H₂SO₄–CH₃COOH mixture are equal to –0.54 (Rh) and 0.0057 (Ir). The Ir complexes have more basic meso-N atoms due to more strong -backbonding effect of coordination and, therefore, the second protonation stage (K ₂ = –4.25) could be also observed. In the CF₃COOH–CH₂Cl₂ mixture, the basic properties of the meso-N atoms are levelled out. For (HSO₄)RhOPTAP K ₁ = 1.35, while for (HSO₄)IrOPTAP K ₁ = 1.24 and K ₂ = 0.45.     

Molecular Structure,Thermodynamic and Spectral Characteristics of Metal-Free and Nickel Complex of Tetrakis(1,2,5-thiadiazolo)porphyrazine

The Knudsen effusion method with mass spectrometric control of the vapor composition was used to study the possibility of a congruent transition to the gas phase and to estimate the enthalpy of sublimation of metal-free tetrakis(1,2,5-thiadiazolo)porphyrazine and its nickel complex (H₂TTDPz and NiTTDPz, respectively). The geometrical and electronic structure of H₂TTDPz and NiTTDPz in ground and low-lying excited electronic states were determined by DFT calculations. The electronic structure of NiTTDPz was studied by the complete active space (CASSCF) method, following accounting dynamic correlation by multiconfigurational quasi-degenerate second-order perturbation theory (MCQDPT2). A geometrical structure of D_2h and D_4h symmetry was obtained for H₂TTDPz and NiTTDPz, respectively. According to data obtained by the MCQDPT2 method, the nickel complex possesses the ground state ¹A_1g, and the wave function of the ground state has the form of a single determinant. Electronic absorption and vibrational (IR and resonance Raman) spectra of H₂TTDPz and NiTTDPz were studied experimentally and simulated theoretically.     

Spectroscopy of acid-base interaction of tetraazaporphyrin complexes in nonaqueous solutions

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 52, No. 1, pp. 94–100, January, 1990.     

Acid-base interactions of benzoannelated porphyrazines in a dichloromethane-trifluoroacetic acid solution

Acid-base interactions of benzoannelated trifluoromethylphenylporphyrazines in a CH₂Cl₂-CF₃COOH medium were studied. The stability constants of the acid forms were determined and assumptions were made concerning their structure. It was shown that successive introduction of benzene rings into a porphyrazine molecule enhances the macrocycle basicity.     

Stability of tetra(tetramethylene)tetraazaporphine in sulfuric acid solutions

In sulfuric acid solutions tetra(tetramethylene)tetraazaparphine undergoes hydrolytic destruction. The reaction is first order in the porphyrin concentration and second order in the hydronium ion concentration.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 629–633, May, 1987.     

Synthesis and Properties of Tetrakis(4-bromophenyl)tetraazaporphyrin

Tetraphenyltetraazaporphyrin was reacted with bromine in trifluoroacetic acid to obtain tetrakis(4-bromophenyl)tetraazaporphyrin. The latter forms with pyridine and dimethyl sulfoxide proton-transfer complexes which differ from each other by the degree of proton transfer from the NH acid to base.