钴卟啉的合成及其催化性能的研究

本文报导了钴5,15-二(对-取代苯基)八烷基卟啉的合成,并讨论了卟环上不同对苯取代基对叶琳与金属钴配位反应速度的影响规律:推电子基团使反应速度减慢,即 配位反应变的速率方程均为:(-d[H₂P])/dt=k表观[H₂P],取代基的影响效应符合Hammatt方程的线性关系。此外,不同取代基卟啉对中心金属钴催化性能的影响是:推电子基增加催化活性,即 。     

Complexation of Zn Arylporphyrinates with Leucine Methyl Ester

Extra coordination of L-leucine methyl ester with seventeen different Zn arylporphyrinates is studied by spectrophotometric titration and capability of Zn porphyrinates with the active OH groups to recognize LeiOCH₃ in toluene at 20°C is determined. The formation of associates of the composition amino acid ether–porphyrinate depending on the substituent positions in a macrocycle is studied by the ¹H NMR method. The most strong donor–acceptor bonds between Zn porphyrinate and LeiOCH₃ are observed in the case of pyridine-substituted porphyrins and porphyrins with phenyl rings containing electron-donor substituents in the m-position. The best recognizing capabilities with respect to leucine are shown by Zn porphyrinates with di- and tetra-4-OH-phenyl substitution in the meso-positions of a macrocycle.     

5,15-二(对-取代苯基)八烷基卟啉及其金属配合物的合成

本文报道了五种5,15-二(对-取代苯基)-2,8,12,18-四乙基-3,7,13,17-四甲基卟啉(Ⅱa—Ⅱe)和五种5,15-二(对-取代苯基)-2,3,7,8,12,13,17,18-八甲基卟啉(Ⅰa—Ⅰe)以及它们的铜、铁、镍金属配合物的合成。这些化合物的结构均经元素分析、UV、~1HNMR和MS鉴定。芳环上不同取代基对卟啉成环反应有一定影响,拉电子基团有利于反应。其顺序如下:NO_2>H>CH_3>OCH_3>N(CH_3)_2。     

Kinetics of the formation and dissociation of complexes of cobalt(II) with <Emphasis Type="Italic">meso</Emphasis>-Phenylocta(methyl)porphyrin derivatives in organic solvents

The influence of the deformation of the tetrapyrrole aromatic macrocycle and the electronic effects of substituents on the kinetic parameters in the formation and dissociation reactions of cobalt complexes of porphyrins are discussed on the basis of a study of the kinetics of the formation and dissociation of cobalt complexes with meso-phenyl octa(methyl)porphyrin derivatives: 5,10,15-triphehyl octa(methyl) porphyrin; 5,15-bis-(3′,5′-di-tert-butyl phenyl) octa(methyl)porphyrin; 5,10,15-tris-(3′,5′-di-tert-butyl phenyl) octa(methyl)porphyrin; and 5,10,15,20-tetrakis-(3′,5′-di-tert-butyl phenyl) octa(methyl)porphyrin in acetic acid and pyridine.     

Catalytic Activity of Tetraarylporphyrins in the Oxidation Reactions of Saturated Hydrocarbons

The oxidation of cyclic hydrocarbons by potassium peroxymonosulfate catalyzed by the iron and manganese complexes of tetra-(4-N-butylpyridinium)porphyrin, tetraphenylporphyrin, and mixed porphyrins containing phenyl and butylpyridyl substituents was studied in an aqueous acetonitrile medium. The test catalysts were dissolved in the reaction medium or adsorbed on layered aluminosilicates. It was found that the immobilization of metal complexes on layered aluminosilicates, as well as the bromination of porphyrins, decreased the activity of catalysts in a number of cases, although it improved their stability. The addition of pyridine in an equimolar amount with respect to metal complexes to the reaction mixture increased the activity of dissolved manganese complexes. An increase in the number of butylpyridyl meso-substituents in a porphyrin molecule improved the catalytic activity of a metal complex.     

Mechanism of cyclohexane oxidation by molecular oxygen in the biomimetic iron porphyrin system with proton and electron donors: I. A radical pathway

The formation of cyclohexyl hydroperoxide during cyclohexane oxidation by air oxygen in a biomimetic iron porphyrin system with proton (AcOH) and electron (Zn) donors and with or without an electron carrier (methylviologen (MV)) in an acetonitrile solution is detected by gas-liquid chromatography. The kinetics of C₆H₁₁OOH decomposition in this system catalyzed by iron porphyrins with various substituents in the phenyl rings is studied, and the rate constants of this process are determined. A kinetic scheme of cyclohexane oxidation is proposed. The contribution of the radical pathway to the reaction product formation is quantitatively estimated in the pseudo-steady-state approximation. For all iron porphyrins under investigation (FeTPP, FeTDCPP, and FeTpivPP), the fraction of the products formed via the radical pathway is smaller than 20%.     

Oxidation of benzyl alcohol by novel peripherally and non-peripherally modular C2-symmetric diol substituted cobalt (II) phthalocyanines

In this study, a modular ligand structure was designed by altering the binding position of the phenyl group at backbone of hydrobenzoin. A series of regio isomeric substituted phthalonitriles derived from this modular C₂-symmetric ligand was synthesized and characterized. Then, eight cobalt (II) phthalocyanines (CoPc) were obtained from the reaction of phthalonitrile derivatives with cobalt (II) chloride. The catalytic activities of synthesized cobalt (II) phthalocyanines were tested for benzyl alcohol oxidation in acetonitrile using tert-butylhydroperoxide as the oxygen source and in the presence of N-bromosuccinimide as an additive at 80 °C for 5 hr of the reaction. In this sense, the effect of substrate to catalyst ratio and oxidant to catalyst ratio have been studied in detail for getting the highest benzaldehyde selectivity (up to 83%). The effect of structural design of substituents at peripheral or non-peripheral positions of phthalocyanine skeleton on the catalytic activity performance of cobalt (II) phthalocyanines in benzyl alcohol oxidation was also clarified. All newly synthesized compounds are characterized by FT-IR, ¹H NMR, IR, UV–Vis and MALDI-TOF MS spectral data.     

Basicity of para-substituted tetraphenylporphyrins studied by two-phase spectropotentiometric titration

The basicity constants of a series of para-substituted tetraphenylporphyrins have been determined by two-phase spectrophotometric titration with pH monitoring in the chloroform-aqueous electrolyte solution system; the pH ranges of prevailing of the dication and the neutral forms of the porphyrins have been estimated. With introducing the donor substituents at the para-position of phenyl fragments of porphyrins, the compound basicity increases. Ionization constant of the pyrrole nitrogen atoms depends on the donor-acceptor properties of the substituents according to the Hammett equation. Basing on the derived dependence, theoretical basicity constants of the para-substituted porphyrins bearing strongly donor groups have been predicted.     

Proton NMR Studies of the Electronic Effect of Substituents at the Azomethine Carbon of N,N′-Bisethylene (Salicylideniminato) Cobalt (II) Complex

The proton paramagnetic shifts of low spin N,N′-ethylenebis(salicylideniminato)cobalt(II) and its derivatives were studied to understand the effect of substituents at the azomethine carbon on the electronic structure of the Schiff-base cobalt complexes. Analysis of the ¹H paramagnetic shifts of H and CH₃ bonded to the azomethine carbon reveals that spin delocalization through a interaction is responsible for the contact contribution to the paramagnetic shift. When the phenyl group is bonded to the azomethine carbon, the plane of the phenyl group is perpendicular to the plane of the complex and the phenyl group makes a negligible contact contribution to the paramagnetic shift.     

四苯基钴卟啉化合物催化过亚硝酸根分解的研究

利用紫外-可见分光光度计在乙醇介质中研究了合成的4种对位取代四苯基钴卟啉对过亚硝酸根分解的催化作用. 首次发现钴卟啉可以催化ONOO^－分解, 且对位带吸电子基团的钴卟啉比对位带供电子基团的钴卟啉催化活性高. TPPCoCl, T(p-CH₃)PPCoCl, T(p-OCH₃)PPCoCl和T(p-Cl)PPCoCl在乙醇中的k_cat分别为1.69×10², 1.52×10², 1.43×10²和1.20×10³ mol^－1•L•s^－1. 动力学曲线和时间分辨谱证明这些钴卟啉是通过形成中间体催化过亚硝酸根分解的.     

Ab initio study of the substituent effects on the relative stability of the E and Z conformers of phenyl esters. Stereoelectronic effects on the reactivity of the carbonyl group

Equilibria between the Z (tau1= 0 degrees) and E (tau1= 180 degrees) conformers of p-substituted phenyl acetates 4 and trifluoroacetates 5 (X = OMe, Me, H, Cl, CN, NO2) were studied by ab initio calculations at the HF/6-31G* and MP2/6-31G* levels of theory. The preference for the Z conformer, DeltaE(HF), was calculated to be 5.36 kcal mol(-1) and 7.50 kcal mol(-1) for phenyl acetate and phenyl trifluoroacetate (i.e., with X = H), respectively. The increasing electron-withdrawing ability of the phenyl substituent X increases the preference of the Z conformer. An excellent correlation with a negative slope was observed for both series between DeltaE of the E-Z equilibrium and the Hammett sigma constant. By using an appropriate isodesmic reaction, it was shown that electron-withdrawing substituents decrease the stability of both conformers, but the effect is higher with the E conformer. Electron-withdrawing phenyl substituents decrease the delocalization of the lone pair of the ether oxygen to the C=O antibonding orbital (nO--> pi*C=O) in both the E and Z forms and in both series studied; this effect is higher in the E conformer than in the Z conformer. The nO --> pi*C=O electron donation has a minimum value with tau1= 90 degrees and a maximum value with tau1= 0 degrees (the Z conformer), the value with tau1= 180 degrees (the E conformer) being between these two values, obviously due to steric hindrance. The effects of the phenyl substituents on the reactivity of the esters studied are discussed in terms of molecular orbital interactions. ED/EW substituents adjust the availability of the pi*C=O antibonding orbital to interact with the lone pair orbital of the attacking nucleophile and therefore affect the reactivity: EW substituents increase and ED substituents decrease it. Excellent correlations were observed between the rate coefficients of nucleophilic acyl substitutions and pi*C=O occupancies of the ester series 4 and 5.     

Conformational flexibility of metalloporphyrins studied by density-functional calculations

Reliable energetic data on the conformational flexibility of organic molecules are important ingredients to better understand the adsorption of such molecules on solid surfaces. Herein, the conformational flexibility of the phenyl substituents in metallo tetraphenyl porphyrins (M-TPP, M = Zn, Co) and metallo tert-butyl tetraphenyl porphyrins (M-TTBPP, M = Zn, Co) has been studied in detail for the first time using density-functional methods. For each molecule, a relaxed two-dimensional potential energy surface scan has been calculated for the two angles describing the rotation and the out-of-plane bending of the phenyl substituents. The results quantify that the molecules are rather flexible close to the energetic minimum while more extreme twisting or tilting of the phenyl substituents results in high-energy deformations of the porphyrin core from planarity due to steric repulsions of adjacent hydrogen atoms.     

Synthesis and Characterization of Push-Pull Porphyrins

A series of “push-pull” porphyrins with 4-nitrophenyl and 4-aminophenyl substituents were synthesized and separated by flash column chromatographic techniques. They were fully characterized by elemental analysis, FAB-MS, FTIR, UV-visible, and ¹H NMR spectroscopies. The unsymmetrical π-electron distribution of the porphyrins caused by the donor (amino) and acceptor (nitro) substituents were investigated by ¹H NMR technique. The pyrrole-H resonance positions can be correlated to the Hammett σ constants of the substituents. Although with strong donor and acceptor substituents, UV-visible spectra show the push-pull porphyrins have rather weak solvatochromism and hence limited intramolecular charge-transfer character.     

Reactivity of triarylphosphine peroxyl radical cations generated through the reaction of triarylphosphine radical cations with oxygen

One-electron oxidation of triarylphosphines (Ar3P, Ar = phenyl and substituted phenyl) in benzonitrile (PhCN) has been studied using pulse radiolysis technique. One-electron oxidation of Ar3P occurred to yield the radical cation (Ar3P*+) which showed an intense absorption with a peak at 360-370 nm together with a broad band at 500-600 nm. The addition of molecular oxygen (O2) to the phosphorus atom of Ar3P*+ took place at the second-order rate constant of 10(7)-10(9) dm(3) mol(-1) s(-1) to yield the peroxyl triarylphosphinyl radical cation (Ar3P+OO*). It is found that the electron-releasing substituents on the para position of the phenyl ring of Ar3P influence the rate constants of the reaction of Ar3P*+ with O2 and that o-methyl substituents on the phenyl ring influence the reactivity of Ar3P+OO*.     

Kinetics of Complexation of meso-Diphenyl-Substituted Alkylporphyrins with Zinc Acetate in Acetonitrile

Kinetics of interaction of diphenyl-substituted porphyrins and their derivatives with substituents in the phenyl fragments with zinc acetate in acetonitrile solution is studied. The effect of the solvent on the rate of coordination is shown. Kinetic parameters of complexation are calculated.     

Kinetic analysis of the phenyl-shift reaction in β-O-4 lignin model compounds: a computational study

The phenyl-shift reaction for the β-radical of phenethyl phenyl ether (PhCH(2)C?HOPh, β-PPE) is an integral step in the pyrolysis of PPE, which is a model compound for the β-O-4 linkage in lignin. We investigated the influence of natural occurring substituents (hydroxy, methoxy) on the reaction rate by calculating relative rate constants using density functional theory in combination with transition state theory, including anharmonic correction for low-frequency modes. The phenyl-shift reaction proceeds through an oxaspiro[2.5]octadienyl radical intermediate and the overall rate constants were computed invoking the steady-state approximation (its validity was confirmed). Substituents on the phenethyl ring have only little influence on the rate constants. If a methoxy substituent is located in the para position of the phenyl ring adjacent to the ether oxygen, the energies of the intermediate and second transition state are lowered, but the overall rate constant is not significantly altered. This is a consequence of the dominating first transition from reactant to intermediate in the overall rate constant. In contrast, o- and di-o-methoxy substituents significantly accelerate the phenyl-migration rate compared to β-PPE.     

系列水溶性磺酸卟啉的制备、表征及催化性能

改进磺化路线制备了5种取代基及取代位置不同的水溶性磺酸卟啉,利用氢核磁共振波谱(1H NMR)、傅里叶变换红外光谱(FTIR)、紫外-可见吸收光谱(UV-Vis)及质谱(MS)等手段对产物进行表征及性质研究.将该系列卟啉作为光催化剂,用于催化氧化1,5-萘二酚的反应,主催化产物为5-羟基-1,4-萘二醌,转化率为78%~95%.实验发现,磺酸基团在苯环上的位置以及取代基的数目、电子效应及立体位阻效应均会对催化结果产生影响,其中磺酸根的位置至关重要.动力学研究结果表明该催化氧化过程为一级反应.探讨了该反应的反应机理.     

Kinetic Studies of Donor–Acceptor Cyclopropanes: The Influence of Structural and Electronic Properties on the Reactivity

The kinetics of (3+2) cycloaddition reactions of 18 different donor–acceptor cyclopropanes with the same aldehyde were studied by in situ NMR spectroscopy. Increasing the electron density of the donor residue accelerates the reaction by a factor of up to 50 compared to the standard system (donor group=phenyl), whereas electron‐withdrawing substituents slow down the reaction by a factor up to 660. This behavior is in agreement with the Hammett substituent parameter σ. The obtained rate constants from the (3+2) cycloadditions correlate well with data from additionally studied (3+n) cycloadditions with a nitrone (n=3) and an isobenzofuran (n=4). A comparison of the kinetic data with the bond lengths in the cyclopropane (obtained by X‐ray diffraction and computation), or the ¹H and ¹³C NMR shifts, revealed no correlation. However, the computed relaxed force constants of donor–acceptor cyclopropanes proved to be a good indicator for the reactivity of the three‐membered ring.     

Kinetic study on the alkaline hydrolysis of 1-aryl-2-phenyl-2-imidazolines. Basicity-rate of hydrolysis and structure relationships

Rate constants (k_obs) of hydrolysis in boiling alkaline ethanolic solution for six 1-aryl-2-phenyl-2-imidazolines were determined. The influence of substituents in the phenyl group at N-1 upon rate of hydrolysis was studied. When the imidazoline ring is considered to be a substituent of the benzene ring at N-1, a good correlation with the Hammett equation is found. It was observed that reaction rates were enhanced by electron-releasing phenyl substituents of N-1 and reduced by electron-withdrawing groups, providing a change in the mechanism of the reaction in the first case that was not observed in the second. Agreement with the Hammett equation allowed comparison between experimental and “calculated” rate constants which are nearly equal. An equation relating the rate constants with the ionization constants of imidazolinium ions is given.     

Acid–base and coordination properties of <Emphasis Type="Italic">Meso</Emphasis>-substituted porphyrins in nonaqueous solutions

Acid–base and coordination properties of alkyl and aryl meso-substituted porphyrins are studied spectrophotometrically in nonaqueous solutions. It is found that the nature of the substituent greatly affects the basicity of ligands for porphyrins characterized by a flat structure of macrocycle. The electronic effects of substituents have a much weaker influence on the kinetics of complexing. These effects could be due to the opposite orientation of some factors: an increase in the basicity and stability of the N–H bonds of porphyrin reaction centers. Dissociation constants pK _b of the cationic forms of meso-substituted derivatives of porphyrin are measured. The values of pK _b are in good agreement with classic concepts of the nature of substituents, particularly those indirectly included in the macrocycle through phenyl buffer rings.