Synthesis of 2,8,12,18-tetrabutyl-3,7,13,17-tetramethyl-5-{3-[11-(pyridin-4-yloxy)-3,6,9-trioxaundecyloxy]phenyl}-porphyrin and study on the effect of its molecular conformation on physicochemical properties

2,8,12,18-Tetrabutyl-3,7,13,17-tetramethyl-5-{3-[11-(pyridin-4-yloxy)-3,6,9-trioxaundecyloxy] phenyl}porphyrin was synthesized, and its complexation with zinc and potassium cations in the system toluene-methanol (5:1) was studied by spectrophotometric titration and ¹H NMR spectroscopy. Spatial preorganization of the meso-aryl substituent due to complex formation of potassium cation with the polyether fragment accelerates the reaction of zinc with the title compound approximately threefold. A probable scheme of the interaction was proposed, and formation constants of the corresponding complexes were determined.     

锌(Ⅱ)-12-正戊基-1,4,7,10-四氮杂环十三烷-11,13-二 酮-α-氨基酸三元配合 物的稳定性

合成了一种新的双氧四胺大环配体：12-正戊基-1,4,7,10-四氮杂环十三烷-11,13二酮(L)。采用pH电位法,在(25±0.1)℃,I=0.1mol·dm^-^3NaNO~3条件下,测定了锌(Ⅱ)与L的二元配合物及锌(Ⅱ)与L和六种α-氨基酸(AA=Gly,Ala,Val,Leu,Ile,Phe)形成的三元配合物的稳定常数。结合量子化学计算结果,讨论了在双氧四胺大环配体上引入疏水碳链形成具有双亲结构的配体后,与金属离子的配位能力的变化以及形成Zn(L)(AA)三元配合物稳定性变化规律。     

ROLE OF THE TRYPTOPHAN FLUORESCENT STATE IN THE ULTRAVIOLET-INDUCED INACTIVATION OF β-TRYPSIN*

Abstract— Stern-Volmer quenching constants for β-trypsin at pH 3 were determined for fluorescence quenching by histidine, acrylamide, and nitrate ion. A modified Stern-Volmer plot (Lehrer, 1971) was employed to show that all of the fluorescent tryptophanyl residues of β-trypsin were equally susceptible to quenching by acrylamide at pH 3 when the enzyme was either in its native conformation or denatured in 6 M guanidine hydrochloride (GuHCl). Fluorescence lifetime measurements indicated that acrylamide quenched β-trypsin fluorescence by a purely collisional mechanism. Solvation of tryptophanyl residues of the protein was maximal at 2.5 M GuHCl, as monitored by fluorescence emission wavelength.
Investigations of the ultraviolet-induced inactivation of β-trypsin at 295 nm were performed in the presence of acrylamide at pH 3. The quantum yields for enzyme inactivation and indole destruction (determined using the PDAB reagent) were unchanged upon depopulation of the fluorescent state by 65 per cent, whether the enzyme was in its native conformation or denatured by 6 M GuHCl. It is concluded that the fluorescent state of tryptophanyl residues of β-trypsin is not involved in enzyme inactivation or tryptophan destruction.     

Spectrophotometry Determination of Copper and Palladium Using Some 1,3,5-Triphenylformazans

A new rapid and accurate method for the spectrophotometric microdetermination of Cu(II) and Pd(II) using some 1,3,5-triphenylformazans (I) is given. The optimum conditions for the formation of the complexes are extensively investigated. The ligands form 1:1 and 1:2 (M:L) complexes with Cu and Pd ions, Beer's law is obeyed up to 3.8 and 6.5 ppm Cu and Pd respectively. The influence of foreign ions is investigated. The ligands were used successfully as indicators in spectrophotometric titration of Cu and Pd ions with EDTA and CDTA.     

Complex formation of dimeric cyclophane zinc diphenylporphyrinates with 1,4-diazabicyclo[2,2,2]octane and pyrazine

The formation of host-guest complexes between dimeric cyclophane zinc diphenylporphyrinates and bidentate ligands of different nature containing two nitrogen atoms has been studied by the spectrophotometric titration method and ¹H NMR spectroscopy in a toluene-methanol (2: 1) binary solvent. The complexation of these dimeric porphyrinates with 1,4-diazabicyclo[2,2,2]octane or pyrazine can lead to 1: 1 or 1: 2 complexes, depending on the metalloporphyrin-to-ligand molar ratio. The stability constants of the porphyrinate-ligand complexes and concentration ranges of their formation have been determined.     

Complexing ability of dimeric zinc octaalkylporphyrinates with a poly(ethyleneoxy) bridge toward 1,4-diazabicyclo[2.2.2]octane and 1,4-diazine

The formation of “guest-host” complexes from dimeric zinc octaalkylporphyrinates with a poly(ethyleneoxy) bridge and various bidentate ligands containing two N atoms was studied by spectrophotometric titration and ¹H NMR spectroscopy in toluene-methanol (5: 1). The reactions of dimeric porphyrinates with 1,4-diazabicyclo[2.2.2]octane and 1,4-diazine gave 1: 1 or 1: 2 complexes, depending on the molar ratio of metal porphyrin and the ligand. The stability constants of the complexes obtained and the concentration ranges for their formation were determined.     

Spectrophotometric study of complex formations between 1-(2-pyridylazo)-2-naphthol (PAN) and some metal ions in organic solvents and the determination of thermodynamic parameters

The complexation reactions between Ni(2+), Co(2+) and Zn(2+) metal ions with PAN in methanol (MeOH), acetonitrile (AN) and dimethyl sulfoxide (DMSO) were studied using a spectrophotometric method. The stability constants of the resulting complexes were determined from computer fitting absorbance mole-ratio data. The results revealed that the stability constants of complexes are varying in order of Ni(2+)相似文献   

Complex formation of mono-and binuclear dimeric cyclophane zinc diphenylporphyrinates with pyridine

The formation of host-guest complexes between zinc diphenylporphyrinates of dimeric diphenylporphyrins and pyridine in toluene has been studied by the spectrophotometric titration method and ¹H NMR spectroscopy. The zinc porphyrinates with pyridine form “internal” or “external” 1: 1 or 1: 2 complexes, depending on the length of binding ether O(CH₂)_nO bridges (n = 2, 3) of the cyclophane dimers and the reactant concentration. The stability constants of the porphyrinate-ligand complexes and concentration ranges of their formation have been determined.     

pH-switched porphyrin receptor: I. Binding of iodide ions

The basic properties of 5,10,15,20-tetra(4-chlorophenyl)porphyrin in the acetonitrile-perchloric acid system at standard temperature were studied by spectrophotometric titration. The protonation of nitrogen atoms of the tetrapyrrole macrocycle was found to proceed in two steps to give mono- and diprotonated species. The corresponding ionization constants and concentration ranges were determined. Diprotonated porphyrin binds efficiently iodide ions; the stability constants of the 1: 1 and 1: 2 complexes thus formed were determined.     

THE TRIPLET EXCITED STATES OF BILIVERDIN AND BILIVERDIN DIMETHYL ESTER

Abstract— The triplet states of biliverdin and biliverdin dimethyl ester have been generated using pulse radiolysis excitation. Biliverdin triplet was formed by energy transfer from biphenyl triplet in acetone, absorbed throughout the wavelength range studied (380–1000 nm) and had a half-life of 11.7μs under the cpnditions chosen. Biliverdin dimethyl ester triplet was formed by energy transfer from biphenyl triplet in benzene, likewise absorbed throughout the wavelength range studied (360–1000 nm) and had a half-life of 6.7μs under the conditions used. Both biliverdin and biliverdin dimethyl ester efficiently quench anthracene, naphthacene, but not μ-carotene, triplet states. On the other hand. neither μ-carotene nor oxygen were found to quench the triplet states of biliverdin or biliverdin dimethyl ester. Estimates or limits for the rate constants of all these quenching reactions were obtained. These reactivities suggest that the triplet levels of both biliverdin and biliverdin dimethyl ester lie around 90 kJ mol^-1. The triplet energy transfer rate from bilirubin to biliverdin dimethyl ester in benzene was measured to be 1.9 × 10⁹ M^-1 s^-1. The singlet-triplet intersystem crossing efficiencies of both molecules were very low, limits of 0.004 and 0.001 being found for biliverdin and biliverdin dimethyl ester, respectively, using 347 nm laser excitation.     

Coordination properties of zinc 5,15-di(<Emphasis Type="Italic">ortho</Emphasis>-aminophenyl)octaalkylporphyrin in reactions with mono- an dibasic nitrogen bases

The coordination properties of zinc 5,15-di(ortho-aminophenyl)octaalkylporphyrin in reactions with mono- and dibasic nitrogen bases in benzene are studied by means of computational modeling and spectrophotometric titration. The stability of molecular zinc porphyrinate complexes in solution is estimated and their structure is determined. The correlation between the coordination properties of the compound under investigation and electronic and conformational factors of the macrocycle is established. The base nature is shown to affect the stability of zinc porphyrinate complexes. The correlations between the calculated σ bond energy of the zinc atom with the nitrogen atom of the base (E _b) and the equilibrium constant of the axial coordination reaction are obtained. It is demonstrated that the reaction is accompanied by an increase in steric hindrance and a change in the type of deformation of the porphyrin ligand.     

Supramolecular complexes of carboxy-substituted zinc porphyrinates with triethylenediamine

α,α-and α,β-Atropoisomers of zinc 5,15-bis(2-carboxyphenyl)octaalkylporphyrinate were obtained, and their complex formation with triethylenediamine in toluene was studied. The α,α-atropoisomer is present in the solution as a supramolecular dimer and forms a 1:1 complex with the two-centered nitrogen-containing base. The complex formation of the undimerized α,β-atropoisomer with triethylenediamine can give 2:1 or 1:1 complexes, depending on the reagent ratio. The stability constants of the complexes and the concentration ranges of their formation were determined by means of spectrophotometric titration and ¹H NMR spectroscopy.     

Synthesis and design of supramolecular systems on the basis of tetrapyrrole macrocycles

Three new cyclophane-like calixarene-bis-porphyrins were synthesized, and their spectral properties were studied. Zinc complex of meso-(aminophenyl)-substituted calixarene-bis-porphyrin was found to form a stable 1:1 complex with dimethyl maleate in toluene. Its stability constant was determined by spectrophotometric titration.     

Thermodynamics of formation of urea complexes with manganese(II), nickel(II) and zinc(II) ions in N,N-dimethylformamide

The complexation of urea (ur) with manganese(II), nickel(II) and zinc(II) ions has been studied by titration calorimetry in N,N-dimethylformamide (DMF) containing 0.4M (C(2)H(5))(4) NBF(4) as a constant ionic medium at 25 degrees C. The calorimetric data were well explained in terms of the formation of [Mn(ur)](2+), [Mn(ur)(2)](2+) and [Mn(ur)(4)](2+) for manganese(II), [Ni(ur)](2+) for nickel(II) and [Zn(ur)](2+) and [Zn(ur)(2)](2+) for zinc(II), and their formation constants, reaction enthalpies and entropies were determined. The complexation of the nickel(II)-urea system in DMF has also been studied by means of spectrophotometric titration and electronic spectra of individual nickel(II) complexes were determined. On the basis of the stepwise thermodynamic quantities and the individual electronic spectra of the complexes, it is revealed that the [Mn(ur)](2+), [Mn(ur)(2)](2+), [Ni(ur)](2+), [Zn(ur)](2+) and [Zn(ur)(2)](2+) complexes have a six-coordinate octahedral structure, while the [Mn(ur)(4)](2+) complex has a four-coordinate tetrahedral structure.     

Synthesis of Two N,N′-bis(N,N-dialkylamide) Derivatives of Diethylenetriaminepentaacetic Acid and the Stabilities of Their Complexes with Gd3+, Ca2+, Cu2+, and Zn2+

Two bis(N,N-dialkylamide) derivatives of DTPA [(carboxymethyl)iminobis (ethylenenitrilo) tetraacetic acid], DTPA-BDMA = the bis(N,N-dimethylamide) and DTPA-BDEA = the bis(N,N-diethylamide) were synthesized. Their protonation constants were determined by potentiometric titration in 0.10 M Me₄NNO₃ and by NMR pH titration at 25.0 ± 0.1 °C. Stability and selectivity constants were measured to evaluate the possibility of using the corresponding gadolinium(III) complexes for magnetic resonance imaging contrast agents. The stability constants of gadolinium(III), copper(II), zinc(II), and calcium(II) complexes with DTPA-BDMA and DTPA-BDEA were investigated quantitatively by potentiometry. The stability constant for gadolinium(III) complexes is larger than those for Ca(II), Zn(II), and Cu(II) complexes. The selectivity constants and modified selectivity constants of the amides for Gd³⁺ over endogenously available metal ions were calculated. Effectiveness of these two ligands in binding divalent and trivalent metal ions in biological media is assessed by comparing pM values at physiological pH 7.4. Spin-lattice relaxivity values R₁ for Gd(III) complexes were also determined. The observed relaxivity values were found to decrease with increasing pH in the acid range below pH 4 and relaxivity values became invariant with respect to pH changes over the range of 4–10. ¹⁷O NMR shifts showed that the [Dy(DTPA-BDMA)] and [Dy(DTPA-BDEA)] complexes had one inner-sphere water molecule. Water proton spin-lattice relaxation rates for the [Gd(DTPA-BDMA)] and [Gd(DTPA-BDEA)] complexes were also consistent with one inner-sphere gadolinium(III) coordination position.     

Thermally latent polyaddition and curing of Di‐ and tri‐functional hemiacetal esters with diepoxide by salen‐zinc complex with tunable catalytic activity and model and networking reactions

Salen‐zinc complexes (Zn/ 1 _R ) thermal‐latently catalyzed the polyaddition of a diepoxide ( 2 ) with a difunctional hemiacetal ester ( 3 ), which proceeded at moderate temperatures (100–150 °C) for curing of mixtures containing monomers and initiators. The catalytic activities of Zn/ 1 _R depended on the Lewis acidities of the complexes controlled by the electronic character of the salen ligands. For example, Zn/ 1 _3,5‐Cl bearing four electron‐withdrawing chlorine atoms initiated the polyaddition at the lowest temperature (100 °C), and Zn/ 1 _OMe bearing two electron‐donating methoxy groups initiated the polyaddition at 120 °C. The Lewis acidities of the complexes were evaluated by NMR and IR spectroscopies and computational calculation. The polyadditions with the salen‐zinc complexes proceeded quantitatively at 150 °C, and the use of a tri‐functional hemiacetal ester ( 7 ) with 2 afforded the corresponding networked polymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1427–1439, 2008     

Effect of halogenation features on the stability of Zinc(II) complexes with monoiodo- and dibromodipyrromethenes

The complex formation of zinc(II) acetate with monoiodo- and dibromo-substituted dipyrromethenes in DMF at 298.15 K were studied by means of spectrophotometric titration. It was found that the process involves consecutive formation of heteroligand [ZnLOAc] and homoligand [ZnL₂] complexes. The thermodynamic stability of halogenated zinc(II) dipyrrolylmethenates [ZnL₂] was studied.     

A molecular receptor based on the 2,3,7,8,12,13,17,18-octaethyl-21,23-dimethylporphyrin for detection of fluoride ions: Synthesis, spectral and complexation properties

2,3,7,8,12,13,17,18-Octaethyl-21-methylporphyrin and 2,3,7,8,12,13,17,18-octaethyl-22,23-dimethylporphyrin monotriflate based on the former were synthesized. Basic and complexing properties of these compounds were studied by the method of spectrophotometric titration in acetonitrile-perchloric acid and acetonitrile-tetrabutylammonium fluoride systems at 298 K. It was established that in the system of acetonitrile-perchloric acid the cationic forms of 2,3,7,8,12,13,17,18-octaethyl-21-methylporphyrin do not form complexes with fluoride ions, whereas 2,3,7, 8,12,13,17,18-octaethyl-22,23-dimethylporphyrin monotriflate forms complexes of 1:1 composition with the fluoride ions. The protonation constant of 2,3,7,8,12,13,17,18-octaethyl-21-methylporphyrin and the stability constant of the complex of 2,3,7,8,12,13,17,18-octaethyl-22,23-dimethylporphyrin with fluoride ions in acetonitrile at the standard temperature were determined.     

Substituted 2,2′‐Bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyl Complexes of Zinc

The condensation reaction of 2,2′‐diamino‐4,4′‐dimethyl‐6,6'‐dibromo‐1,1′‐biphenyl with 2‐hydroxybenzaldehyde as well as 5‐methoxy‐, 4‐methoxy‐, and 3‐methoxy‐2‐hydroxybenzaldehyde yields 2,2′‐bis(salicylideneamino)‐4,4′‐dimethyl‐6,6′‐dibromo‐1,1′‐biphenyl ( 1a ) as well as the 5‐, 4‐, and 3‐methoxy‐substituted derivatives 1b , 1c , and 1d , respectively. Deprotonation of substituted 2,2′‐bis(salicylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyls with diethylzinc yields the corresponding substituted zinc 2,2′‐bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyls ( 2 ) or zinc 2,2′‐bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐6,6′‐dibromo‐1,1′‐biphenyls ( 3 ). Recrystallization from a mixture of CH₂Cl₂ and methanol can lead to the formation of methanol adducts. The methanol ligands can either bind as Lewis base to the central zinc atom or as Lewis acid via a weak O–H ··· O hydrogen bridge to a phenoxide moiety. Methanol‐free complexes precipitate as dimers with central Zn₂O₂ rings.     

pH-switchable porphyrin receptor for binding halide ions

Main properties of 5,10,15,20-tetra(4-chlorophenyl)porphyrin in the acetonitrile-perchloric acid system were studied by the method of spectrophotometric titration at standard temperature. The protonation of nitrogen atoms of the tetrapyrrole macrocycle was shown to occur in two steps, through the formation of mono- and diprotonated forms. The corresponding ionization constants and concentration intervals were determined. The diprotonated form of porphyrin was shown to bind effectively iodide, bromide and chloride ions, the stability constants of the complexes of 1:1 and 1:2 composition were determined.