Synthesis and structure of the first clathrochelate iron(II) tris-dioximates with inherent nitrile substituent(s) and new dehalogenation--reduction reaction at a quasi-aromatic macrobicyclic framework

Monoribbed-substituted mono- and dicyano-functionalized iron(II) macrobicycles were obtained for the first time by the reaction of iron(II) diiodoclathrochelate precursor with copper(I) cyanide-triphenylphosphine complex under mild conditions. The target dinitrile clathrochelate is a minor product of this reaction, whereas the major product contains only one cyano group. The clathrochelates obtained were characterized using elemental analysis, (1)H and (13)C{(1)H} NMR, IR and UV-vis spectroscopy, MALDI-TOF spectrometry and X-ray diffraction crystallography. The geometry of their FeN(6)-coordination polyhedra is intermediate between a trigonal prism (TP) and a trigonal antiprism (TAP); the distortion angles, φ, are 22.6-24.7°. In the molecule of the precursor, the Fe-N distances are close, whereas in the mononitrile macrobicycles those for their functionalized chelate fragments are substantially smaller than the corresponding distances in the α-benzyldioximate moieties. The heights, h, of the TP-TAP coordination polyhedra and the average bite angles, α, (2.33 ? and 39°, respectively) are the same for the X-rayed clathrochelates. The UV-vis spectra indicate a dramatic redistribution of the electron density in the π-conjugated clathrochelate framework caused by functionalization with inherent nitrile substituents. The proposed mechanism of the dehalogenation-reduction reaction of iron(II) diiodoclathrochelate resulting in substitution of their iodine atoms by a cyano group and hydrogen atom includes the anion-radical hydrodehalogenation of this precursor with acetonitrile as a source of hydrogen atom. Then, the monomethinemonoiodine macrobicyclic product underwent a substitution with a cyano group only. The copper(I) cyanide-triphenylphosphine-acetonitrile system is proposed as a tool for the synthesis of nitrile derivatives of electron-withdrawing heterocycles starting from their halogen-containing precursors.     

Investigation of unsubstituted porphyrazine by proton NMR and the structure of porphyrazine ligands

The proton NMR spectra of unsubstituted porphyrazine (tetraazaporphine) and of its Zn complex in pyridine-D₅ and in CF₃COOD have been obtained for the first time. The observed strong deshielding of the pyrrole hydrogen atoms of these compounds compared with porphyrins indicates the existence of strong intramolecular hydrogen bonds with neighboring pyrrolenic nitrogen atoms. An unsymmetrical bridge structure is proposed for the reaction center of unsubstituted porphyrazine with significantly ionized N?H bonds. It is suggested that a symmetrical bridge structure almost completely ionized, may exist only in the presence of such strong electron-accepting substituents as halogen in the pyrrole rings of the porphyrazine macrocycle.     

Electronic structure and fluorescence of the Mg(II) complex of 1,4-diazepinotribenzoporphyrazine

Spectral and luminescent properties of a new phthalocyanine analog, the magnesium complex of diphenyl substituted mono(1,4-diazepino)tribenzoporphyrazine, have been studied at 293 and 77 K. The results have been explained on the basis of quantum-chemical calculations for both this molecule and its simpler analogs with respect to 6H/1H-isomerism of the 1,4-diazepine ring. The small difference between the ground-state energies for the 6H and 1H isomers makes tautomerism between them possible. It is shown that the electronic transitions with intramolecular charge transfer from the diazepine fragment to the macrocycle have relatively low energy, especially for the 1H isomers. These states can be of considerable importance for photophysical and photochemical processes. A comparison of the theoretical and experimental electronic absorption spectra has confirmed that the diazepine ring in the substituted Mg-diazepinoporphyrazine is present in the 6H-form. It is established that substitution of one benzene ring by a diazepine fragment leads to quenching of fluorescence, decreasing its quantum yield to 27% (for Mg-phthalocyanine 76%). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 3, pp. 365–375, May–June, 2009.     

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.     

Synthesis and properties of binuclear nitride-bridged iron octaphenyltetraazaporphyrin. E.p.r. studies of dioxygen adduct formation

Summary The synthesis and characterization are reported for (-nitrido)bis[(octaphenyltetraazaporphyrinato)iron] ([OPTAP)Fe]₂N). The [(OPTAP)Fe]₂N dimer is paramagnetic with one unpaired electron per dimer unit and shows a typical axially symmetric e.p.r. spectrum in non-polar solvents at liquid N₂ temperature (g=2.126, g=2.001), with well-resolved superhyper-fine splitting resulting from the -nitrido bridge (A ^N =2.48mT, A ^N =2.60mT).A pyridine monoadduct of [(OPTAP)Fe]₂N, formed in frozen glasses has been characterised by changes in e.p.r. spectra. Electronic spectra show no pyridine adduct formation at 298 K. Mössbauer parameters (IS=–0.042 mm/s, QS=1.769mm/s at 298K) are indicative of the predominant iron(IV) character in [(OPTAP)Fe]₂N.The pyridine monoadduct binds O₂ reversibly. The O₂ adduct was characterized by e.p.r. spectroscopy (g₁=2.062, g₂=2.007, g₃=2.000). O₂ titration as monitored by e.p.r. shows that the adduct stoichiometry is one O₂ per dimer. A spin-pairing model for O₂ binding accounts for the observed O₂-[(OPTAP)Fe]₂N interaction.     

Study of acid-base interactions of mono- and diazaporphyrin indium complexes with acetic and trifluoroacetic acids by <Superscript>1</Superscript>H NMR and electronic spectroscopy

Indium complex of 13,17-dibutyl-2,3,7,8,12,18-hexamethyl-5-azaporphyrin (Cl)InMAP was synthesized, and acid-base interactions of the meso-nitrogen atoms in (Cl)InMAP and its diaza analog (Cl)InDAP with acetic and trifluoroacetic acids were studied by ¹H NMR and electronic spectroscopy. Depending on the medium, the complexes and proton-donor species HA give rise to acid solvates >N(HA)_n which are converted to final acid-base interaction products, H-complexes >NH+A^–(HA)_m or ionic associates >NH⁺A^–(HA)_l , as the acidity of the medium rises. In acetic acid solution, the acid solvates derived from more basic (Cl)InMAP exist in equilibrium with the H-associates (pK _a1 = 4.45±0.03). From (Cl)InDAP, the corresponding H-associates are formed only in the presence of H₂SO₄ (pK _a1 = 2.10±0.03). In more polar media (solutions of trifluoroacetic acid in methylene chloride), ionic associates are formed, which involve one [(Cl)InMAP, pK ₁ = 2.46±0.02] or two meso-nitrogen atoms [(Cl)InDAP, pK ₁ = 2.11±0.03, pK ₂ = 0.41±0.04).Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 9, 2004, pp. 1546–1556.Original Russian Text Copyright © 2004 by Stuzhin, Ivanova, Migalova.This revised version was published online in April 2005 with a corrected cover date.     

The Kinetic Stability of Octaphenyltetrapyrazinoporphyrazine in the Nitrogen Base—Dimethylsulfoxide System

The state of octaphenyltetrapyrazinoporphyrazine in dimethylsulfoxide was studied. The proton transfer complex formed was found to be fairly stable; its structure was suggested. The complex was kinetically unstable in strongly basic media. The influence of the nature of cyclic and acyclic nitrogen bases on the rate and activation parameters of the destruction of the proton transfer octaphenyltetrapyrazinoporphyrazine complex was studied.     

Synthesis and spectral properties of 1,2,5-thiadiazolo-, 1,2,5-selenadiazolo-, and benzo-fused β-phenyl-substituted porphyrazines

Cross cyclotetramerization of trans-2,3-diphenylbutanedinitrile with 1,2,5-thia(selena)diazole-3,4-dicarbonitriles or phthalodinitrile in the presence of magnesium butoxide gave mixtures of Mg(II) porphyrazine complexes which were treated with trifluoroacetic acid to isolate unsymmetrical hexaphenyl-substituted 1,2,5-thia(selena)diazolo-and benzo-fused porphyrazines together with diphenyltribenzoporphyrazine. Their ¹H NMR and electronic absorption spectra (in the UV and visible regions) were recorded. The effect of benzene and heteroring fusion on the electronic and steric structure and spectral properties of porphyrazine derivatives was studied in terms of the molecular orbital perturbation theory and semiempirical quantum-chemical calculations (AM1, PM3, ZINDO/S, CNDO/S).