The state of 5,10,15,20-tetraphenyl-21H,23H-porphine rhenium(V) complexes in solutions of acids

The spectral properties (UV/Vis, IR, ¹H NMR) and stability of diverse forms of 5,10,15,20-tetraphenyl-21H,23H-porphine rhenium(V) complexes in neutral and protolytic solvents have been studied. Quantitative characteristics have been obtained for the reactions of formation and interconversion of the μ-oxo dimeric and monomeric rhenium(V) complex species in the benzene-AcOH system and dissociation at the coordination center of the H⁺-associated form of the monomeric rhenium(V) complex in mixed H₂O-H₂SO₄ solvents in a wide range of component concentrations. It has been shown that the stability of the coordination center of the rhenium(V) complexes sharply depends on the nature of a second acido ligand, in addition to the coordinated porphyrin.     

Coordination of 5,10,15,20-tetraphenyl-21H,23H-porphin by rhenium in various oxidation states

A method was developed for the synthesis of three rhenium complexes, (5,10,15,20-tetraphenyl-21H,23H-porphinato)(phenoxo)rhenium(III) (PhO)ReTPP, (5,10,15,20-tetraphenyl-21H,23H-porphi-nato)(chloro)rhenium(III) (Cl)ReTPP, and μ-oxo-bis[(oxo)-(5,10,15,20-tetraphenyl-21H,23H-porphi-nato)rhenium(V)] [O=ReTPP]₂O, by one reaction between porphyrin H₂TPP and H₂ReCl₆ in boiling phenol. In the complex formation reaction accompanied by the redox process, only the metal cation is involved in the transformation. Rhenium(IV) as chlororhenic acid dispropoportionates without participation of solvent or porphyrin to give Re(III) and Re(V) complexes. The chemical structures of the products were established by spectral and elemental analysis. Characteristics of the UV, Vis, IR, and ¹H NMR spectra, the chromatographic mobility, and stability of the complexes were determined.     

Synthesis, structure, and reactions of iridium(I) complexes with 5,10,15,20-tetraphenyl-21H,23H-porphine and 5,10,15,20-tetraphenyl-21H,23H-porphine dianion

One-step joint synthesis of two iridium porphyrin complexes, a donor-acceptor SAT (sitting a top) complex μ-(5,10,15,20-tetraphenylporphine)-bis-chloroiridium(I) and the covalent complex (5,10,15,20-tetraphenylporphinato)chloroiridium(III) by the reaction of free porphyrin and chloroiridic acid (H₃O)₂IrCl₆ in boiling phenol was studied. The structure of complexes was confirmed by spectroscopy (UV/Vis, IR, 1H NMR) and TLC. The iridium(III) SAT complex with the hydride ligand in the first coordination sphere, (acetato)hydrido(5,10,15,20-tetraphenylporphine)iridium(III), was obtained by oxidative addition reaction, which is quite rare for porphyrin complexes. The thermodynamic stability of the complexes to oxidants (aerated acids) was studied by spectrophotometric titration.     

Rhenium(I) tricarbonyl complexes of 5,10,15,20-tetraphenyl-21-thia and 21-oxaporphyrins

The hexa-coordinated rhenium(I) tricarbonyl complexes of 5,10,15,20-tetraphenyl-21-thiaporphyrin 1 and 5,10,15,20-tetraphenyl-21-oxaporphyrin 2 have been synthesized by thermal reaction of corresponding free base porphyrin with Re(2)(CO)(10). The compounds 1 and 2 are characterized by HR-MS mass, (1)H, and (13)C NMR, FTIR, UV-vis, and electrochemical techniques and the structures are determined by X-ray single crystal analysis. The X-ray analysis revealed different coordination behavior of Re(CO)(3) with 21-thiaporphyrin and 21-oxaporphyrin. Interestingly, the Re(CO)(3) coordinates to two of the three inner nitrogens and one sulfur instead of three inner nitrogens as generally expected to produce unique compound 1 whereas it coordinates to three inner nitrogens but not with furan oxygen to form compound 2. The 21-thiaporphyrin ring is more distorted in compound 1 compared to 21-oxaporphyrin ring in compound 2 on complexation with Re(CO)(3). The presence of three carbonyl groups in compounds 1 and 2 are verified by (13)C NMR and IR spectroscopy. The absorption spectra of compounds 1 and 2 showed ill-defined Q-bands along with broad Soret band and the extinction coefficients are much lower than their corresponding free base porphyrins. The compounds 1 and 2 showed two reversible porphyrin ring based reductions supporting their electron deficient nature. The compound 1 is very stable under protonation conditions, and the protonation occurs at the uncoordinated pyrrole ring whereas the compound 2 undergoes decomplexation under same conditions. Furthermore, compound 1 showed the fluxional behavior in coordination mode of binding in solution.     

Pre-steady state reactivity of 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin iron(III) chloride with hydrogen peroxide

A stopped-flow study has shown that tetrakis(pentafluoro-phenyl)porphyrin iron(III) chloride reacts rapidly (<3 ms) with hydrogen peroxide to form a Fe(III)-H(2)O(2) complex where log K = 2.39. This subsequently undergoes rapid intramolecular conversion (k = 4.4 s(-1)) to an iron(IV) intermediate, which in turn reacts with hydrogen peroxide (k' = 54.3 M(-1) s(-1)) to reform the original Fe(III)-H(2)O(2) complex.     

Ligand substitution reaction at a binuclear organoplatinum(II) complex

The ligand substitution reactions of the N-donor ligand in the binuclear dimethylplatinum(II) complex of formula cis,cis-[Me₂Pt(μ-NN)(μ-dppm)PtMe₂], 1, in which dppm = bis(diphenylphosphino)methane and NN = phthalazine, by different nucleophilic phosphorous-donors L, L = P(O-ⁱPr)₃ or PPh₃ and L₂ = dppm, to form the dinuclear complexes 2, cis,cis-[Me₂LPt(μ-dppm)PtLMe₂] and cis,cis-[Me₂Pt(μ-dppm)₂PtMe₂], respectively, are studied. Complex 1 has a MLCT band in the visible region which was used to easily follow the kinetics of its ligand substitution reactions. These reactions which involve diplatinum(II) complex 1 containing cis Pt-C bonds, proceeded by the normal associative mechanism. In associative reactions of the present work, as expected, the rate of the reactions was depended on the concentration and the nature of the entering group. The nucleophilicity of PPh₃ is stronger than P(O-ⁱPr)₃ on the basis of its stronger σ-donor ability and its lower solvation and is responsible for the observed 3-fold increase of its rate as compared to that of P(O-ⁱPr)₃. Also, the solvation energy involved is suggested to be responsible for the observation of higher rates in benzene than in acetone. The ΔH^‡/ΔS^‡ compensation plot gives a straight line which suggests the operation of the same mechanism for all entering nucleophiles.     

Investigation of ground- and excited-state photophysical properties of 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphyrin with ruthenium outlying complexes

The present work employs a set of complementary techniques to investigate the influence of outlying Ru(II) groups on the ground- and excited-state photophysical properties of free-base tetrapyridyl porphyrin (H(2)TPyP). Single pulse and pulse train Z-scan techniques used in association with laser flash photolysis, absorbance and fluorescence spectroscopy, and fluorescence decay measurements, allowed us to conclude that the presence of outlying Ru(II) groups causes significant changes on both electronic structure and vibrational properties of porphyrin. Such modifications take place mainly due to the activation of nonradiative decay channels responsible for the emission quenching, as well as by favoring some vibrational modes in the light absorption process. It is also observed that, differently from what happens when the Ru(II) is placed at the center of the macrocycle, the peripheral groups cause an increase of the intersystem crossing processes, probably due to the structural distortion of the ring that implies a worse spin-orbit coupling, responsible for the intersystem crossing mechanism.     

配合物Zn(II)-BPHA的^1H NMR谱

测定了各pD值下BPHA[BPHA是N,N'-bis(2-aminoethyl)-1,3-propanediaminehexaaceticacid的简称,中文名称为二胺乙基丙二胺六乙酸]和Zn^2^+-BPHA的^1HNMR谱。BPHA两端羧甲基上亚甲基质子的化学位移δ~a和中间羧甲基上亚甲基质子的化学位移δ~b随pD值交替变化。Zn^2^+-BPHA的^1HNMR谱有3种情况:pD<6,对应Zn(II)-H~2BPHA^4^-,有一特征尖峰,显示自由-NH^+(CH~2COO^-)~2残基存在;pD=6-9,对应Zn(II)-HBPHA^5^-,该峰消失,显示4个胺基全部配位;pD>9,对应Zn(II)-BPHA^6^-,该峰再次出现,1个N(CH~2COO^-)~2脱离配位体系。在3种形态的配合物中,Zn-N键都是非活性的,Zn-O键在后两种形态配合物中是非活性的。     

Structure and stability of H+ associates of (5,10,15,20-tetraphenylporphinato)silver(II) in trifluoroacetic acid

Direct experimental confirmation of the formation of ion-molecular associates of (5,10,15,20-tetraphenyl-21H,23H-porphinato)silver(II) (AgTPP) with solvent protons in CF₃COOH is obtained by means of 1H NMR spectroscopy. Their structure and spectral properties, as well as the kinetics of dissociation on metal-nitrogen bonds, depending on the concentration of CF₃COOH (89–100%) and temperature (298–328 K), are studied It is shown that AgTPP acts as a C-base during the formation of H+ associates, the coordination centers of which have a high stability.     

Synthesis,Crystal Structure and Spectroscopic Properties of Zn(II) with N-carbamylglutamate Ligand

Zn C6H8N2O5.H2O(NCGZn) has been synthesized, and its functional groups present in the title compound were confirmed by elemental analysis, TG and IR spectral studies. Meanwhile, the crystal of NCGZn was obtained by slow evaporation of a saturated aqueous solution at room temperature and confirmed by single-crystal X-ray diffraction analysis. It crystallizes in triclinic, space group P21 with a = 5.03220(1), b = 13.3747(4), c = 12.9944(4), β = 92.987(2)°, V = 873.39(4)3, Z = 2, C12H20N4O12Zn2, Mr = 543.10, Dc = 2.065 g/cm3, F(000) = 552, μ(Mo Ka) = 2.826 mm-1, R= 0.0422 and w R = 0.1142. In NCGZn, Zn1 and the symmetry formed Zn1 ions are connected by five atoms from four NCG-2H anions and a water molecule. A NCG ligand has two carboxylate groups, one connecting a Zn ion, and the other bridgiong two Zn ions. The NCG ligand bridges four Zn ions through the amino group and two carboxylate groups with a water molecule to yield a 3D coordination polymer structure with hydrogen bonds.     

An NMR study of the complexes of Zn(II) and Cd(II) ions with tris(dimethylamino)phosphine sulphide: Ligand exchange kinetics

The preparation of the complex species [Cd(TDPS)₄](ClO₄)₂ and [Zn(TDPS)₄](ClO₄)₂ (TDPS = tris(dimethylamino)phosphine sulphide)     

β -Cyclodextrin-Mediated Regioselective Hydrolysis of 5,10,15,20-tetrakis[2,4-bis(pivaloyloxy)phenyl]-21H,23H -porphine

The four peripheral ester moieties of the title compound 5 are regioselectively hydrolyzed under mild conditions in the presence of β -cyclodextrin ( 10 ), providing a new entry to tetraphenylporphyrin derivatives with differently substituted Ph groups in the meso-positions. UV, ¹H-NMR and mass spectroscopy of the inclusion complex 9 of 2,6-O-dimethyl-β-cyclodextrin ( 12 ) and 5 indicate a stoichiometry of 2:1 for 10/5 . Moreover, calculations confirm NOE experiments consistent with the fact that the cyclodextrins 10 and 12 approach the Ph groups of the porphyrin with the small opening of the cavity (primary face).     

Isotope exchange reaction in uranous-uranyl-sulphuric acid system Catalytic effect of Fe(II) on the exchange reaction

Our previous paper reported the effect of acidity and temperature on uranous-uranil isotope exchange reaction in sulphuric acid solution.¹ It was found that the half-life of the isotope reactiont _1/2 is around 10 seconds, when the acidity and the temperature of the reaction system are reasonably selected. However, when the uranium isotopes are enriched by ion exchange the single separation factor could be 1.001. Thus, the half-life,t _1/2 is less than one second for potential industrial application.     

Spectrophotometric study of Cd(II), Pb(II), Hg(II) and Zn(II) complexes with 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin

The reaction of 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin (TCPP) with Cd(II), Pb(II), Hg(II) and Zn(II) was studied spectrophotometrically and kinetics, equilibrium constants as well as photodecomposition of complexes were determined. It was verified that these metal ions with large radius accelerate the incorporation reaction of zinc into TCPP. On the basis of the mechanism and kinetics of this reaction, a sensitive method for the spectrophotometric determination of trace amounts of Zn(II) has been developed. The molar absorptivity of examined Zn-TCPP complex and Sandell's sensitivity at 423 nm were 3.5×10⁵ M⁻¹ cm⁻¹ and 18.3 ng cm⁻². The detection limit for the recommended procedure was 1.4×10⁻⁹ M (0.9 ng ml⁻¹) and precision in range 20-100 ng ml⁻¹ not exceeds 2.7% RSD. The proposed method applied for zinc determination in natural waters and nutritional supplement was compared with AAS results and declared value.     

Kinetics of metal exchange reaction of Cu(II)-poly(vinyl alcohol) complex with Ca(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid in aqueous solution

The kinetics of the metal exchange reaction between the Cu(II)-poly(vinyl alcohol) complex (Cu(II)-PVA) and Ca(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid (Ca(II)-EDTA) were studied by mixing both solutions in a spectrophotometer at pH 9.7–11.0, at μ = 0.10(KNO₃) and at 25°C. The reaction is initiated by the formation of unstable Cu(II)-H-PVA by the attack of H⁺ to Cu(II)-PVA, and while both ligand exchange and metal exchange steps occur, the latter may be rate-determining. The kinetic expression of this reaction was determined as -d[Cu(II)-PVA]/dt = k[Cu(II)-PVA] [H⁺] [PVA]/[Ca(II)-EDTA], where k = k₁ + k′₂[H⁺], k₁ = 3.85 × 10⁻² sec⁻¹, k₂ = k′₂ · K^−H_Cu(II)-H-PVA 9.59 × 10⁵ 1 mol⁻¹ sec⁻¹.     

Comparing a mononuclear Zn(II) complex with hydrogen bond donors with a dinuclear Zn(II) complex for catalysing phosphate ester cleavage

Introducing ligand based hydrogen bond donors to increase the activity of a mononuclear Zn(II) complex for catalysing phosphate ester cleavage can be a more effective strategy than making the dinuclear analogue.