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.     

A novel lutetium(III) acetate phthalocyanine directly substituted with N,N’-dimethylaminophenyl groups via CC bonds and its water-soluble derivative for photodynamic therapy

In this study, the novel 4-(N,N′-dimethylamino)phenyl substituted lutetium(III) acetate phthalocyanine (2) and its quaternized derivative (3) were synthesized via a Suzuki-Miyaura coupling reaction between tetrakis(iodo) lutetium(III)acetate phthalocyanine (1) and 4-(N,N-dimethylamino)phenylboronic acid, and subsequent quaternization using dimethyl sulfate, respectively. The obtained phthalocyanine 3 exhibited excellent solubility in water which is important for photodynamic therapy applications. Photophysical properties such as fluorescence quantum yield and fluorescence lifetime, and photochemical properties such as singlet oxygen generation and photostability were investigated to determine their suitability for photodynamic therapy. The lutetium(III) phthalocyanines, especially quaternized derivative 3, showed promising properties as potential photosensitizers for the treatment of cancer, producing higher singlet oxygen (Φ_Δ = 0.59) than motexafin lutetium (Φ_Δ = 0.31) which is a clinically used lutetium texaphyrin photosensitizer.     

State of the rare earth elements tetapyrazinoporphyrazinate complexes in protic media

Russian Journal of General Chemistry - The acid-base interactions of tetrapyrazinoporphyrazine erbium(III) and lutetium(III) complexes in the media based on acetic and trifluoroacetic acids were...     

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.     

Synthesis,crystal structure and activity for H2O2 disproportionation of a binuclear manganese(III) complex [(tol)Mn(bbml)2Mn(tol)](ClO4)2

The title binuclear Mn₂(III) complex was synthesized through the reaction of 2-[bis(2-benzimidazolylmethyl)amino]ethanol (Hbbml), Mn(DMSO)₆(ClO₄)₃ and o-toluic acid (Htol). X-ray structure analysis shows that the two Mn(III) atoms are bridged by the oxygen atoms of the two bbml ligands, forming a bis(μ-alkoxo)dimanganese core. Electrospray mass spectrometry (ES-MS) experiments shows that the complex cation may easily lose one or two tol⁻ ligands leaving an unoccupied coordination site, which would favor the coordination and activation of H₂O₂. Furthermore, its catalytic activity for the disproportionation of H₂O₂ and the effect of added heterocyclic base were also investigated. The complex has some similarities to manganese catalase in structure and activity.     

Thermal investigations of dehydration of lanthanide(iii) 5-nitroanthranilates

The 5-nitro-2-anthranilates of lanthanum(III), samarium(III), terbium(III), erbium(III) and lutetium(III) were obtained as hydrates having 2.5 mol of water molecules per 1 mol of compound. The compounds are isostructural. The processes of dehydration and rehydration were investigated. The first step of dehydration does not cause the change of crystal structure. The entire dehydration gives anhydrous compounds with different structure than the structure of hydrates. However, the dehydration of La, Sm, Tb and Er is reversible - the rehydration process gives the complexes having the same crystal structure as the initial compounds. Only the anhydrous lutetium complex under the influence of moisture does not give the starting compound. This revised version was published online in July 2006 with corrections to the Cover Date.     

Anti-hepatocellular carcinoma,antioxidant, anti-inflammation and antimicrobial investigation of some novel first and second transition metal complexes

New coordination compounds of some selected metal ions from the first and second transition metals series with a Schiff base were synthesized and characterized. The Schiff base is derived from 4-Aminoantipyrine and 3-(hydroxyimino) butan-2-one. The compounds were characterized by different analysis tools like; elemental analysis, mass spectra, Fourier transform infrared (FTIR) as well as electronic spectra, magnetic measurements, molar conductance and thermal analysis technique. All complexes were formed with 1:1 (metal: ligand) stoichiometry except Mn (II) where 1:2 (Mn: ligand) is formed. Schiff base ligand interacted as a tridentate ligand by using the nitrogen atoms of the imine and the oximato groups and the carbonyl oxygen atom as donor groups with all studied metal ions except copper (II) and manganese (II) where the carbonyl oxygen is not shared in the coordination. These complexes show various physicochemical properties. X-ray powder diffraction shows different crystal systems; Cd (II) complex: hexagonal, Cu (II) complex: orthorhombic; and [Ni (II), Mn (II), Rh (III) & Pd (II)] complexes: monoclinic. All compounds showed potent cytotoxicity against the growth of human liver cancer cell lines. The square planar Pd (II) complex was more active than those of octahedral geometries of all other synthesized complexes. Cd (II) complex has the highest microbial growth inhibition than the rest of the prepared complexes. The docking active sites interactions were evaluated using the selected proteins EGFR tyrosine kinase and protein crystal structure of GlcN-O-P synthase. in vitro antioxidant assay revealed potent free radical scavenging activity of the three synthesized Cu (II), Pd (II) and Rh (III) complexes that exceeded the standard ascorbic acid. Pd (II) complex shows the most significant inhibition denaturation percent.     

Dipyrrin‐Bis(N‐Confused Porphyrin) Conjugate: Synthesis,Synergetic Ligation and Chirality Sensing

A fully conjugated system 4 consisting of two 2‐aza‐21‐carbaporphyrin (NCP) subunits bridged by dipyrrin was synthesized by a highly selective condensation of 3‐pyrrole‐NCP 2 with aryl aldehydes. The free base 4 as well as its silver(III) complex 5 exhibited flexibility of the bridge allowing synergetic binding of Ag^I, thus leading to a mixed‐valence tetraporphyrinic assembly consisting of eight silver atoms which was characterized both in the solid state and in solution. Binding of chiral acid by 4 and 5 was shown by observation of an induced optical activity of the adducts.     

Inclusion complexes of trivalent lutetium cations with an acidic derivative of per(3,6-anhydro)-alpha-cyclodextrin

The cyclodextrin derivative (hexakis (2-O-carboxymethyl-3,6-anhydro)-alpha-cyclodextrin) forms mono- and bimetallic complexes with lutetium(III) in aqueous solution; the X-ray structure of the binuclear complex [Lu2(ACX)(H2O)2] is the first example of a lanthanide-cyclodextrin inclusion complex.     

Polyhapto-aromatic interactions in lead(II) coordination

In its crystalline form, the Pb(II) complex of 1,3-diphenylpropane-1,3-dionate (dibenzoylmethanide, DBM(-)) can be regarded as containing polymeric chains of centrosymmetric, dimeric Pb(2)(DBM)(4) units linked through hexahapto interactions of the Pb atoms with phenyl groups from adjacent units. Each Pb atom also appears to be involved in intraunit dihapto-aromatic interactions, thus attaining a total hapticity of thirteen. Comparison with the analogous Sn(II) compound indicates that the unusually high coordination number may reflect the capacity of Pb(II) to act as both a Lewis acid and a Lewis base.     

Two- and three-dimensional networks of gadolinium(III) with dicarboxylate ligands: synthesis, crystal structure, and magnetic properties

Four gadolinium(III) complexes with dicarboxylate ligands of formulas [Gd2(mal)3(H2O)5]n.2nH2O (1), [Gd2(mal)3(H2O)6]n (2), [NaGd(mal)(ox)(H2O)3]n (3), and [Gd2(ox)3(H2O)6]n.2.5nH2O (4) (mal = malonate; ox = oxalate) have been prepared, and their magnetic properties have been investigated as a function of the temperature. The structures of 1-3 have been determined by X-ray diffraction methods. The crystal structure of 4 was already known, and it is made of hexagonal layers of Gd atoms that are bridged by bis-bidentate oxalate. Compound 1 is isostructural with the europium(III) malonate complex [Eu2(mal)3(H2O)5]n.2nH2O,1 whose structure was reported elsewhere. The Gd atoms in 1 define a two-dimensional network where a terminal bidentate and bridging bidentate/bis-monodentate and tris-bidentate coordination modes of malonate occur. Compound 2 has a three-dimensional structure with a structural phase transition at 226 K, which involves a change of the space group from I2/a to Ia. Although its structure at room temperature was already known, that below 226 K was not. Pairs of Gd atoms with a double oxo-carboxylate bridge occur in both phases, and the main differences between both structures deal with the Gd environment and the H-bond pattern. 3 is also a three-dimensional compound, and it was obtained by reacting Gd(III) ions with malonic acid in a silica gel medium. Oxalic acid results as an oxidized product of the malonic acid, and single crystals of the heteroleptic complex were produced. The Gd atoms in 3 are connected through bis-bidentate oxalate and carboxylate-malonate bridges in the anti-anti and anti-syn coordination modes. Compounds 1 and 2 exhibit weak but significant ferromagnetic couplings between the Gd(III) ions through the single (1) and double (2) oxo-carboxylate bridges, whereas antiferromagnetic interactions across the bis-bidentate oxalate account for the overall antiferromagnetic behavior observed in 3 and 4.     

Kinetic characteristics of the destruction of β,β-annelated porphyrazines in a nitrogen-containing base–dimethylsulfoxide system

The state of tetra(1,2,5-thiadiazolo)porphyrazine in a dimethyl sulfoxide medium is investigated. Relatively high stability is observed for the resulting proton-transfer complex, and a chemical structure is proposed for it. It is shown that the nature of the substituent in the porphyrazine macrocycle influences the kinetic parameters of the destruction of tetra(1,2,5-thiadiazolo)porphyrazine, tetra(5-tert-butylpyrazino) porphyrazine, octaethyltetrapyrazinoporphyrazine, and octaphenyltetrapyrazinoporphyrazine in a nitrogen-containing base–dimethylsulfoxide system. The effect the NH acidity of the porphyrazine macrocycle and the nature of the nitrogenous bases have on the reaction rate and activation parameters of the destruction of β,β-annelated porphyrazine proton-transfer complexes is established.     

ABAB homoleptic bis(phthalocyaninato)lutetium(III) complex: toward the real octupolar cube and giant quadratic hyperpolarizability

The concept of octupolar molecules has considerably enlarged the engineering of second-order nonlinear optical materials by giving access to 2D and 3D architectures. However, if the archetype of octupolar symmetry is a cube with alternating donor and acceptor groups at the corners, no translation of this ideal structure into a real molecule has been realized to date. This may be achieved by designing a bis(phthalocyaninato)lutetium(III) double-decker complex with a crosswise ABAB phthalocyanine bearing alternating electron-donor and electron-acceptor groups. In this communication, we present the first step toward this goal with the synthesis, crystal structure determination, and measurement of the molecular first-order hyperpolarizability β by harmonic light diffusion, of an original lutetium(III) sandwich complex displaying the required ABAB-type alternation for one face of the cube. This structure is characterized by an intense absorption in the near-IR due to an intervalence transition and exhibits the highest quadratic hyperpolarizability ever reported for an octupolar molecule, √<β(2)(HLS)> = 5750 × 10(-30) esu.     

Catalytic Oxidative Decarboxylation of Some Benzylcarboxylic Acid Derivatives by a New Iron(III) Schiff Base Complex

A quadridentate Schiff base ligand of N,N’-bis(2-hydroxy-α-methylbenzylidene)ethylenediamine (HMBEDA) and its new iron(III) complex were synthesized and identified by analytical, spectral data (1H NMR, 13C NMR FT-IR and UV-visible) and molar conductance. A rapid and efficient homogeneous oxidative decarboxylation of some benzylcarboxylic acid derivatives was carried out by a catalytic amount of iron(III) Schiff base complex in chloroform, using tetrabutylammonium periodate as a mild oxidant in good to excellent yields at room temperature.     

Extraction equilibria of rare earths by a new reagent (2-ethylhexyl-3-pentadecylphenyl) phosphoric acid

A new reagent (2-ethylhexyl-3-pentadecylphenyl) phosphoric acid (EPPA = HR) was synthesized from cardanol (I, 37300-39-5) and was used to investigate the extraction behaviour of lanthanum(III), europium(III) and lutetium(III) from hydrochloric acid solutions. The species extracted were found to be Ln(HR(2))(3) (where Ln = La(III) or Eu(III) or Lu(III)). The extraction behaviour of the above lanthanides has also been compared with yttrium and other rare earths. It was observed that the extraction increases with increase in atomic number of rare earths. In addition, the extraction efficiency of EPPA has also been compared with well known acidic organophosphorus extractants like di-2-ethylhexyl phosphoric acid (DEHPA), 2-ethylhexyl-mono-2-ethylhexyl phosphoric acid (EHEHPA).     

From structural properties of the EuIII complex with ethylenediaminetetra(methylenephosphonic acid) (H8EDTMP) towards biomedical applications

Crystals of Eu(III) with ethylenediaminetetra(methylenephosphonic acid) (H(8)EDTMP) and with ethylenediaminetetraacetic acid (H(4)EDTA) have been synthesized in the same experimental conditions and their X-ray analyses have been performed. The EDTMP ligand wraps the Eu(III) ion in a fashion similar to its carboxylic analogue, EDTA, i.e. coordinating through two nitrogen atoms and four oxygen atoms in such a way that only one oxygen atom from each phosphonate group is bonded to the central ion. The coordination sphere is completed by two oxygen atoms of the bidentate carbonate anion in the case of the Eu(III)-EDTMP complex, whereas the inner sphere of the Eu(III)-EDTA crystal is completed by three water molecules. Spectroscopic studies (UV-Vis and (31)P NMR spectra) of Eu(III)-EDTMP solutions at controlled pH showed that the replacement of inner sphere water molecules and/or OH hydroxy groups by a carbonate anion in the Eu(III)-EDTMP complex at physiological pH results in the formation of [Eu(EDTMP)(CO(3))](7-) species which is thermodynamically stable and kinetically inert. The affinity of the carbonate anion towards the Eu(III)-EDTMP species was studied by analysis of f-f intensities and luminescence decay rates. The dissociation constant of the Eu(III)-EDTMP-carbonate complex was found to be approximately 43 mM. The presented results may be helpful in understanding the role played by the (153)Sm(III)-EDTMP complex known as Quadramet in the seeking of metastatic tissue in bones as well as possibly giving some premises for future ligand design of these types of complexes with lanthanide radionuclides.     

A dinuclear oxygen-bridged Schiff base iron(III) complex derived from <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-bis(4-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine

The μ-oxo-bridged Fe(III) dimer complex [{Fe(4-MeOL1)}₂(μ-O)]?HOCH₃, (H₂-4-MeOL1 = N,N′-bis(4-methoxy-2-hydroxybenzylidene)-2,2-dimethylpropane-1,3-diamine), 1 is synthesized and characterized by single crystal X-ray diffraction. Complex 1 contains a [{Fe(4-MeOL1)}2(μ-O)] dimeric unit with a methanol solvent molecule of crystallization. Each Fe(III) ion has a distorted square-pyramidal coordination geometry. In the basal plane, the Fe(III) atom is coordinated by two N and two O atoms of the Schiff base ligand. The apical position is occupied by a bridging O^2– ion, linking another Fe(III) ion in the complex. There are intermolecular C–H…O and C–H…π interactions among the dinuclear complexes.     

Acid-base and spectroelectrochemical properties of doubly N-confused porphyrins

The cis-doubly N-confused porphyrin, H2N2CP, containing two adjacent confused pyrrole rings has been investigated from the point of view of its acid-base and electrochemical behavior in dichloromethane. This novel porphyrin isomer can form two metal-carbon bonds in the central core, stabilizing metal ions in unusually high oxidation states. Furthermore, the two outside N-pyrrole atoms remain available for acid-base and specific solvent interactions. Protonation of the pyrrole N atoms proceeds according to two successive steps, while only a single deprotonation step has been observed in the presence of bases. Similarly, in the case of the silver and copper complexes the protonation and deprotonation of the outer pyrrole rings have been detected, confirming the structure of the metalated species as M(III)-HN2CP. The electrochemical reduction of the metal ions (III/II redox process) and oxidation of the macrocycle ring have been detected respectively at -0.9 and 1.4 V based on spectroelectrochemical measurements in conjunction with the acid/base equilibrium studies. Additional waves observed around -0.5 and 1.3 V have been assigned to redox processes involving water molecules associated with the doubly N-confused porphyrins.     

A new chromium (III) complex containing N-(2-pyridylmethyl)-2-pyrazinecarboxamide, (NPyPzCa): Synthesis,molecular and crystal structure and theoretical electron density analysis

The chromium (III) complex [Cr(NPyPzCa)Cl₂(H₂O)].(CH₃)₂O (1) (NPyPzCa stands for N-(2-pyridylmethyl)-2-pyrazinecarboxamide) has been synthesized and characterized by single crystal X-ray diffraction. The Cr(III) atom exhibits an octahedral geometry due to the coordination of three donor atoms from carboxamide ligand, two chlorine atoms and one water molecule. There is O–H?O hydrogen bonds and also π–π interactions between adjacent pyridine and ?pyrazine rings that seem to be effective in the stabilization of the crystal packing. The ?topological and energetic properties of the electron density distribution of all the metal–ligand ?bonding interactions in this complex have also been calculated and studied at ? several DFT levels. According to the results, metal–ligand bonding interactions belong (from the topological and energetic point of view) to new interactions that represent a mix of closed-shell (ionic) and shared (covalent) characters.