Silicon(IV) complexes of octaaryl-substituted porphyrazines and corrolazines: influence of macrocycle contraction on spectral-luminescence, acid-base, and redox properties.

The template cyclomerization of the iminoimide derivatives (obtained by the treatment of diarylfumarodinitriles with NH3 in methanol containing catalytic amounts of dissolved Na) in the presence of SiCl4 in pyridine leads to silicon(IV) octaarylporphyrazine complexes ((HO)2SiPzAr8, Ar = Ph, tBuPh) as a main reaction product. In the case of phenyl-substituted derivative, the formation of a distinctive Si(IV) complex as a byproduct was observed, which according to mass-spectroscopy measurement contains the macrocycle with five diphenylpyrrolic units. The treatment of bishydroxy complexes with tripropylchlorosilane in the presence of magnesium in pyridine leads to the formation of axially siloxylated porphyrazines (Pr3SiO)2SiPzAr8, followed by the reductive contraction of the macrocycle and formation of the corresponding corrolazine complexes (Pr3SiO)SiCzAr8. It is shown that the addition of acid (trifluoroacetic acid, TFA) facilitates the detachment of one siloxy group in (Pr3SiO)2SiPzAr8 and is essential for its Pz → Cz transformation. In the presence of TFA, only one meso-nitrogen is protonated in the porphyrazine complexes (Pr3SiO)2SiPzAr8 (stability constant of the protonated form pKs1 = -0.45 for Ar = Ph; pKs1 = 0.68 for Ar = tBuPh), while two consequent protonation stages are observed for the more basic corrolazine complex (Pr3SiO)SiCzPh8 (pKs1 = 0.93, pKs2 = 0.45). Both types of Si(IV) complexes are poorly fluorescent (ΦF < 0.07). The porphyrazine complexes have low ability to generate singlet oxygen (ΦΔ < 0.15), whereas the corrolazine derivative (Pr3SiO)SiCzPh8 is a very efficient photosensitizer (ΦΔ = 0.76).

Water-soluble sulfonated phosphorus(V) corrolazines and porphyrazines: the effect of macrocycle contraction and pyrazine ring fusion on spectral, acid-base and photophysical properties.

Novel water-soluble dihydroxophosphorus(V) complexes of sulphophenyl substituted porphyrazine (6), corrolazine (7) and its pyrazine fused derivative (8) were prepared and their spectral, acid-base and photophysical properties in aqueous solutions were studied. Due to the presence of eight SO3H groups, the compounds were fully monomeric (7 and 8) or only slightly aggregated (6) in water. Spectrophotometric titration revealed that the two stage deprotonation of axially bonded hydroxy groups can be achieved for porphyrazine 6 (pKa1 = 5.62, pKa2 = 9.13) and pyrazine fused corrolazine 8 (pKa1 = 6.5, pKa2 = 11.7), while only the first dissociation stage could be observed for corrolazine 7 (pKa1 = 9.94). The fluorescence emission of the corrolazines 7, 8 and especially porphyrazine 6 was low in water (ΦF = 0.086, 0.18, and 0.014, respectively) and completely quenched under basic conditions due to photoinduced electron transfer. In comparison with porphyrazine 6, the contraction of the macrocycle in the corrolazines 7 and 8 induced significant improvement of singlet oxygen production in water reaching values of ΦΔ = 0.56 and 0.43, respectively, which makes the corrolazines promising photosensitizers for photodynamic therapy. The observed evolution of the electronic absorption spectra and fluorescence quenching observed in a basic medium was explained using the model DFT calculations (cc-pvtz basis set) performed for the dihydroxophosphorus(V) complexes of unsubstituted porphyrazine and corrolazine and their mono- and doubly deprotonated forms.

Effects of solvation on the spin state of iron(III) in 2,8,12,18-tetrabutyl-3,7,13,17-tetramethyl-5,10-diazaporphyrinatoiron(III) chloride.

The chloroiron(III) complex of 2,8,12,18-tetrabutyl-3,7,13,17-tetramethyl-5,10-diazaporphyrin, [(Cl)FeMBDAP], was prepared and studied by X-ray crystallography and by solution (1)H NMR and UV-vis measurements. In the crystal structure of hemisolvate [(Cl)FeMBDAP] x 0.5CHCl(3), two nonequivalent [(Cl)FeMBDAP] units containing Fe1 and Fe2 are arranged in pi-dimers with considerable overlap on their concave sides. Axial chloride bonded to Fe2 is solvated by hydrogen bonding with CHCl(3). Parameters of the coordination pyramid have typical values for the spin-mixed (S = 3/2 / 5/2) Fe(III) complexes in the case of Fe1 and are characteristic for the pure intermediate-spin state for Fe2 (displacement from the (N(Pyr))(4) planes - 0.385 and 0.290 A and the average N(Pyr)-Fe bond lengths -1.992 and 1.954 A for Fe1 and Fe2, respectively). Effective magnetic moments in CHCl(3) and CH(2)Cl(2) capable of specific solvation of chloride by hydrogen bonding (4.5-4.6 micro(B) at 298 K) are indicative about mixed intermediate/high-spin state S = 3/2 / 5/2, with the S = 3/2 contribution increasing upon lowering of the temperature (4.02 micro(B) in CD(2)Cl(2) at 193 K). In nonsolvating CCl(4), C(6)D(6), and THF-d(8), the mu(eff) values are consistent with the predominantly high-spin state at ambient temperature (5.5-5.75 micro(B) at 298 K) and almost pure S = 5/2 state at low temperature (ca. 5.9 micro(B) in THF-d(8) below 270 K). Downfield isotropic shifts from 35 to 50 ppm are observed for alpha-alkyl protons and upfield shifts from -5 to -15 ppm for meso-CH protons, which is characteristic for the presence of the intermediate-spin state. The splitting of signals of the diastereotopic alpha-CH(2) protons is increased with growth of the S = 3/2 state contribution from 1.5 to 4 ppm in nonsolvating to 11 ppm in specifically solvating solvents at 298 K and further to 31 ppm at 193 K (in CD(2)Cl(2)). In the presence of DMSO addition and in methanol solution, the single CH(2) signal is observed at 25-28 ppm, and the meso-CH resonance is also shifted downfield to ca. 30 ppm, indicating the formation of six-coordinated complexes [(DMSO)(2)FeMBDAP](+) and [(MeOH)(2)FeMBDAP](+), the latter having the mu(eff) value of 4.92 micro(B) at 291 K is a spin-mixed species. The electron spin resonance spectra recorded at 77 K indicates that in frozen glasses in CD(2)Cl(2) and THF molecules in the high-spin state (g( perpendicular) approximately 6) and the predominantly intermediate-spin state (g( perpendicular) approximately 4.2-4.3) coexist together.

Tetrakis(1,2,5-thiadiazolo)porphyrazines. 9. Synthesis and spectral and theoretical studies of the lithium(i) complex and its unusual behaviour in aprotic solvents in the presence of acids.

The template cyclotetramerization of 1,2,5-thiadiazolo-3,4-dicarbonitrile in the presence of lithium n-butoxide in n-butanol leads to the Li(i) complex of tetrakis(1,2,5-thiadiazolo)porphyrazine. Various possible structures of dilithium and monolithium complexes have been considered by DFT/B3LYP molecular modelling using the cc-pvtz basis set, and their theoretical IR and UV-VIS spectra have been calculated. The experimental 7Li NMR, IR and UV-VIS spectra measurements show that the complex contains two inequivalent lithium atoms - one is coordinated to the macrocyclic dianion to form the anionic lithate complex [TTDPaLi]-, while the other forms the solvated countercation [Li(Solv)4]+. The lithate complex is stable in protic solvents, such as methanol, and is soluble in water to give aggregated solutions. Its demetallation occurs in the presence of acids (CH3COOH, CF3COOH, H2SO4). In aprotic solvents (DMF, DMSO), the acid-catalyzed formation of the [TTDPa]2- dianion is observed which is followed by the formation of the meso-protonated form {H[TTDPa]}- at higher acid concentrations. Both processes can be reversed by the addition of a lithium salt excess or neutralization of the acid. The fluorescence quantum yield for the lithate complex [TTDPaLi]- is much higher than that for the [TTDPa]2- dianion (0.34 and 0.01 in DMSO), and this can be used for detecting low concentrations of acids and Li+ in aprotic solvents (10-6-10-5 M). The first reversible reduction of the macrocycle in the anionic lithate complex (-0.94 V vs. SCE in DMSO) is ∼0.5 V more difficult than that in the complexes with divalent metals [TTDPaM] (M = MgII, ZnII, CuII).

Tetrakis(thiadiazole)porphyrazines. 4. Direct template synthesis, structure, general physicochemical behavior, and redox properties of Al(III), Ga(III), and In(III) complexes.

Monometallic derivatives of tetrakis(1,2,5-thiadiazole)porphyrazine, [TTDPzH2], with main group tervalent metal ions having the formulae [TTDPzMX] (TTDPz = tetrakis(1,2,5-thiadiazole)porphyrazinato dianion; M = Al(III), X = Cl-, Br-, OH-; M = Ga(III), X = Cl-, OH-; M = In(III), X = AcO-) were prepared and investigated by single-crystal X-ray analysis and IR and UV-vis spectroscopy as well as cyclic voltammetry and spectroelectrochemistry. The complexes [TTDPzMX] (M = Al(III), X = Cl-, Br-; M = Ga(III), X = Cl-) were obtained by direct autocyclotetramerization of the precursor 3,4-dicyano-1,2,5-thiadiazole in hot quinoline in the presence of MX3 salts (M = Al(III), Ga(III); X = Cl-, Br-) and were hydrolized to form the corresponding hydroxide derivatives, [TTDPzMOH]. The In(III) complex, [TTDPzIn(OAc)], was obtained from the free-base macrocycle [TTDPzH2] with In(OH)(OAc)2 in CH3COOH. A single-crystal X-ray study was made at 173 K on the two isostructural species [TTDPzMCl] (M = Al(III), Ga(III)), which have space group P, with a = 12.470(14), b = 12.464(13), and c = 13.947(12) angstroms, alpha = 70.72(3), beta = 79.76(3), and gamma = 90.06(3) degrees, V = 2009.3(3) angstroms3, and Z = 4 for [TTDPzAlCl] and a = 12.429(3), b = 12.430(3), and c = 13.851(3) angstroms, alpha = 70.663(6), beta = 79.788(8), and gamma = 89.991(9) degrees, V = 1983.3(7) angstroms3, and Z = 4 for [TTDPzGaCl]. Square pyramidal coordination exists about the M(III) centers, with Cl- occupying the apical position (Al-Cl = 2.171(5) and Ga-Cl = 2.193(1) angstroms). Al(III) and Ga(III) are located at distances of 0.416(6) and 0.444(2) angstroms from the center of the N4 system. The molecular packing consists of stacked double layers with internal and external average interlayer distances of 3.2 and 3.3 angstroms, respectively. IR spectra show nu(Al-Cl) at 345 cm(-1) for [TTDPzAlCl], nu(Al-Br) at 330 cm(-1) for [TTDPzAlBr], and nu(Ga-Cl) at 382 cm(-1) for [TTDPzGaCl]. The UV-vis spectra in weakly basic (pyridine, DMF, DMSO) and acidic solvents (CF3COOH, H2SO4) show the typical intense pi --> pi transition bands in the Soret (300-400 nm) and Q-band regions (640-660 nm), the bands evidencing some dependence on the nature of the solvent, particularly in acidic solutions. Cyclic voltammetry, differential pulse voltammetry, and thin-layer spectroelectrochemical measurements in pyridine and dimethylformamide of the species [TTDPzMX] indicate reversible first and second one-electron reductions, whereas additional ill-defined reductions are observed at more negative potentials. The examined species are much easier to reduce than their phthalocyanine or porphyrin analogues as a result of the remarkable electron-attracting properties of the TTDPz macrocycle which contains annulated strongly electron-deficient thiadiazole rings.