四苯基卟吩化合物的表面增强喇曼散射

自首次发现表面增强喇曼散射(SERS)并计算了其增强倍数后,现已发展成为一个十分活跃的研究领域,并先后采取金属电极、真空镀膜、银溶胶等方法达到增强的目的.本文采用化学还原镀银法研究了四苯基卟吩(简称TPP)系列化合物在银表面的SERS。TPP类化合物尽管边缘取代物有很大差别,但其中心核相似.某些TPP类化合物的共振喇曼谱和红外光谱已有过报导。本文讨论了TPP金属络合物与自由碱基TPP化合物在SERS中存在差别的原因,提出了TPP化合物在银表面的吸附态,探讨了SERS的增强机理。     

Reversible oxidation state change in germanium(tetraphenylporphyrin) induced by a dative ligand: aromatic GeII(TPP) and antiaromatic GeIV(TPP)(pyridine)2

Treatment of GeCl2(dioxane) with Li2(TPP)(OEt2)2 (TPP = tetraphenylporphyrin) in THF yields Ge(TPP), the first free Ge(II) porphyrin complex. In pyridine Ge(TPP) is converted to Ge(TPP)(py)2, an antiaromatic Ge(IV) complex, whereas in benzene the reaction is reversed, and pyridine dissociates from Ge(TPP)(py)2 to form Ge(TPP). That reversible reaction represents an unusual, if not unique, example of an oxidation-state change in a metal induced by coordination of a dative ligand. UV-vis and 1H NMR spectroscopy show that Ge(TPP) is an aromatic Ge(II) porphyrin complex, while the 1H NMR spectrum of Ge(TPP)(py)2 clearly indicates the presence of a strong paratropic ring current, characteristic of an antiaromatic compound. Both Ge(TPP) and Ge(TPP)(py)2 have been crystallographically characterized, and the antiaromaticity of Ge(TPP)(py)2 leads to alternating short and long C-C bonds along the 20-carbon periphery of its porphine ring system. Coordination of pyridine to Ge(TPP) greatly increases its reducing ability: the Ge(TPP)0/2+ redox potential is about +0.2 V, while the Ge(TPP)(py)2(0/+) redox potential is -1.24 V (both vs. ferrocene). The equilibrium constant of the reaction Ge(TPP) + 2 py = Ge(TPP)(py)2 in C6D6 is 22 M-2. The germanium complex of the more electron-withdrawing tetrakis[3,5-bis(trifluoromethyl)phenyl]porphyrin, Ge(TArFP), and its pyridine adduct Ge(TArFP)(py)2 were synthesized. The equilibrium constant of the reaction Ge(TArFP) + 2 py = Ge(TArFP)(py)2 in C6F6/C6D6 is 2.3 x 10(4) M-2. Density functional theory calculations are consistent with the experimental observation that M(TPP)(py)2 formation from M(TPP) and pyridine is most favorable for M=Si, borderline for Ge, and unfavorable for Sn.     

Direct determination of the complete set of iron normal modes in a porphyrin-imidazole model for carbonmonoxy-heme proteins: [Fe(TPP)(CO)(1-MeIm)

Detailed Fe vibrational spectra have been obtained for the heme model complex [Fe(TPP)(CO)(1-MeIm)] using a new, highly selective and quantitative technique, Nuclear Resonance Vibrational Spectroscopy (NRVS). This spectroscopy measures the complete vibrational density of states for iron atoms, from which normal modes can be calculated via refinement of the force constants. These data and mode assignments can reveal previously undetected vibrations and are useful for validating predictions based on optical spectroscopies and density functional theory, for example. Vibrational modes of the iron porphyrin-imidazole compound [Fe(TPP)(CO)(1-MeIm)] have been determined by refining normal mode calculations to NRVS data obtained at an X-ray synchrotron source. Iron dynamics of this compound, which serves as a useful model for the active site in the six-coordinate heme protein, carbonmonoxy-myoglobin, are discussed in relation to recently determined dynamics of a five-coordinate deoxy-myoglobin model, [Fe(TPP)(2-MeHIm)]. For the first time in a six-coordinate heme system, the iron-imidazole stretch mode has been observed, at 226 cm(-)(1). The heme in-plane modes with large contributions from the nu(42), nu(49), nu(50), and nu(53) modes of the core porphyrin are identified. In general, the iron modes can be attributed to coupling with the porphyrin core, the CO ligand, the imidazole ring, and/or the phenyl rings. Other significant findings are the observation that the porphyrin ring peripheral substituents are strongly coupled to the iron doming mode and that the Fe-C-O tilting and bending modes are related by a negative interaction force constant.     

Synthesis and spectroscopic analysis of tetraphenylporphyrinatoantimony(V) complexes linked to boron-dipyrrin chromophore on axial ligands

Tetraphenylporphyrinatoantimony(V) complexes, linked to boron-dipyrrin chromophores on axial ligands, were synthesized. The fluorescence spectra of 1a, 1b and 1c (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1a); 6-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]hexyloxo(methoxo)antimony(V) tetraphenylporphyrin bromide (1b); bis{3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo}antimony(V) tetraphenylporphyrin bromide (1c)) were analyzed under the excitations of N,N′-difluorobornyl-5-dipyrrinylphenyl (Bdpy) and tetraphenylporphyrinatoantimony(V) (Sb(TPP)) chromophores. Under the irradiation of Bdpy chromophore, the excitation energy was transferred from Bdpy chromophore to the Sb(TPP) moiety at 0.13–0.40 of the quantum yields, even in a polar solvent. On the other hand, the emission of Sb(TPP) chromophores was quenched by Bdpy chromophores at rate constants of 10⁸–10⁹ s⁻¹, independent of on the solvent polarity. Under the excitation of the Bdpy chromophore of 1d (3-[4-(N,N′-difluorobornyl-5-dipyrrinyl)phenyl]propoxo(phenyloxo)antimony(V) tetraphenylporphyrin bromide) involving both the Bdpy and the phenoxy chromophores on the axial ligands, the excited singlet state of the Sb(TPP) chromophore generated by the energy transfer from the Bdpy chromophore was quenched by the phenoxy ligand via non-radiative processes involving electron transfer. However, rapid back electron-transfer may occur because no absorption of the anion radical of Sb(TPP) was observed by nanosecond laser photolysis.     

Inhibition of thiamin diphosphate dependent enzymes by 3-deazathiamin diphosphate

3-Deazathiamin diphosphate (deazaTPP) and a second thiamin diphosphate (TPP) analogue having a benzene ring in place of the thiazolium ring have been synthesised. These compounds are both extremely potent inhibitors of pyruvate decarboxylase from Zymomonas mobilis; binding is competitive with TPP and is essentially irreversible even though no covalent linkage is formed. DeazaTPP binds approximately seven-fold faster than TPP and at least 25,000-fold more tightly (K(i) less than 14 pM). DeazaTPP is also a potent inhibitor of the E1 subunit of alpha-ketoglutarate dehydrogenase from E. coli and binds more than 70-fold faster than TPP. In this case slow reversal of the inhibition could be observed and a K(i) value of about 5 nM was calculated (ca. 500-fold tighter binding than TPP).     

2-吡唑啉类化合物发光机制的研究

本工作合成了新型的2-吡唑啉类化合物:1-3-二苯基-4-(p-硝基苄叉)-2-吡唑啉,研究了该化合物在室温及低温77K时的稳态光物理行为,结果表明:在标题化合物分子中存在着两种电荷转移机制,其一是从N1→N2→C3→苯基,其二是从N1→N2→C3→C4→P-硝基苄叉,光激发下,两种电荷转移机制相互竞争,且具有不同的发光构象。     

The NMR spectra of the porphyrins 16—zinc(II) meso-tetraphenylporphyrin (Zn TPP) as a diamagnetic shift reagent. A quantitative ring current model

The facile preparation of zinc(II) meso-tetraphenylporphyrin (Zn TPP) and derivatives from substituted benzaldehydes and pyrrole, combined with the calculation of ring current shifts in these molecules, provides a useful series of selective diamagnetic shift reagents. The porphyrin-ligand equilibrium is examined for some nitrogenous bases and the complexation shifts (δP values) are obtained in precisely the same manner as LIS. The parameterization of the double-dipole model of the porphyrin ring current is given, with the inclusion of the phenyl ring currents and free rotation about the substrate-Zn bond. Precise agreement with the porphyrin proton chemical shifts and the complexation shifts of the geometrically rigid substrates of pyridine, 4-picoline and quinuclidine is obtained. In contrast, the ¹³C complexation shifts in these molecules are subject to additional effects other than the ring current shift.     

Density functional theory studies on the Raman and IR spectra of meso-tetraphenylporphyrin diacid

The vibrational spectra of meso-tetraphenylporphyrin diacid (H4TPP2+) have been studied with the density functional theory. Raman and IR spectra of H4TPP2+ and its N-deuterated analogue (D4TPP2+) are measured and compared with the computational results. Complete assignments of observed IR and Raman bands were proposed on the bases of calculation results. The DFT calculations reproduce 140 observed fundamentals with the RMS 8.6 cm-1. The computational as well as the experimental results reveal that the saddle-distortion of porphyrin macrocycle for the diacid leads to a significant effect on its vibrational spectra. Especially, several out-of-plane skeletal modes, which were either unobserved or very weak in the Raman spectra of CuTPP and H2TPP, are activated in the Raman spectra of the diacids. In addition, enhancement for the Raman bands of phenyl CC stretching modes were observed and attributed to the conjugation effect of pi-systems of the phenyl and the porphyrinato macrocycles.     

An antiaromatic porphyrin complex: tetraphenylporphyrinato(silicon)(L)2 (L=THF or pyridine)

Treatment of Si(TPP)Cl2 (TPP = tetraphenylporphyrinato) with 2 equiv of Na/Hg in THF yields the reduced porphyrin complex, Si(TPP)(THF)2, in which the porphyrin ring system has an oxidation state of 4- and the complex is antiaromatic. Single-crystal X-ray diffraction reveals that Si(TPP)(THF)2 is highly ruffled and exhibits a unique C-C bond length alternation around its periphery. In addition, experimental 1H and 29Si NMR chemical shifts and NICS (nucleus-independent chemical shift) calculations on a model compound indicate a strong paratropic ring current in Si(TPP).     

Synthesis, Characterization and Weak Intramolecular Interactions of Porphyrins Bearing Nucleobases

5,10, 15-Triphenyl-20-{2- [α- (adenine-9 ) acetylamino]} phenyl porphyrin ( 1 ), 5,10, 15-triphenyl-20-{2-[α-(cytosine-1)acetylamino]} phenyl porphyrin (2), 5, 10, 15-triphenyl-20-{4-[α-(cytosine-1)ethoxy]} phenyl porphyrin (3) and their zinc complexes Zn-1, Zn-2 and Zn-3 have been prepared and characterized by ^1H NMR spectra, elemental analyses, electronic absorption spectra and mass spectra (FAB). Intramolecular π-π interactions and intramolecular metal-~ interaction for 1, 2, Zn-1,and Zn-2 have been investigated by several methods. ^1H NMR studies demonstrate that the porphyrin π-system in 1 and 2 is parallel to the adenine and the cytosine aromatic ring, respectively. The electronic absorption spectral properties of free porphyrin derivatives and their zinc complexes have been compared with those of H2TPP and ZnTPP. The results show that the UV-vis spectra of 1 and 2 are the same as that of H2TPP,whereas the spectra of their zinc complexes show 7 nm red shifts of the Soret bands compared to that of ZnTPP. The emission spectra of Zn-1 and Zn-2 are independent of excitation wavelength. From combination of the evidence of absorption and emission spectra it is suggested the existence of intramolecular metal-π interaction in Zn-1 and Zn-2. The results of conformational analysis agreed quite nicely with that of experiments, thus it was further to validate the experimental conclusions.     

The incorporation of C_(60) in cavities of 5,10,15,20-tetra-4-oxy(2-stearic acid)phenyl porphyrin in LB film

The structure and properties of mixed monolayer or LB film of 5,10,15,20-tetra-4-oxy(2-stearic acid)phenyl porphyrin/C60 were studied. A isotherms and small angle X-ray diffraction (SAXD) results show that C60 molecules were incorporated into the cavities of por-phyrin molecules in mixed monolayer and LB film . UV-vis spectra of mixed LB films show that the absorption intensity of porphyrin varied compared with pure porphyrin film, probably arising from the interactions between C60 and porphyrin ring. C60 molecules in mixed systems are well-dispersed. The TPP(CO2H)/C60 mixed LB film is a kind of two-dimensional host-guest system.     

The doubly oxidized, antiaromatic tetraphenylporphyrin complex [Li(TPP)][BF4

[reaction: see text] Oxidation of dilithium tetraphenylporphyrin, Li(2)(TPP), yields the doubly oxidized porphyrin complex [Li(TPP)][BF(4)]. Free TPP appears to be unstable. The crystal structure of [Li(TPP)][BF(4)] reveals that the 16-atom C-N inner ring of the porphyrin consists of alternating single and double bonds. NMR spectroscopy and nucleus-independent chemical shift (NICS) calculations, in addition to the distortion from planarity observed in the crystal structure, indicate that the 16 pi-electron inner C-N ring of the porphyrin is antiaromatic.     

Effects of different light irradiations on structure and optical properties of methoxy-substituted tetraphenylporphyrins

UV lamp, filtered halogen lamp (at 425 nm) and Green laser (532 nm) experiments on a series of meso-substituted tetra phenyl porphyrin, TPP, bearing methoxy peripheral groups together with a metal derivate of 3,4 dimethoxy TPP were lead to different protonation and aggregation structures. Properties of irradiated porphyrins were investigated using their absorption and emission spectra in dichloromethane solution. The results show that the optical properties of the TPP derivates depend on light irradiation source, which shows the tuning of the absorption and emission spectra of the TPP derivates. From the dynamic light scattering measurements, the size distribution of samples was estimated about 5–15 nm in solvent after irradiation. Atomic force microscopy images of deposited porphyrins on the glass surface were shown average particle size between 10 and 30 nm. Particularly, self-assembly of the porphyrin derivates was also observed when green laser was used. We suggest that the irradiation source plays an important role in the controlling of size and morphology of products, and we propose a self-organization model to explain the formation of the porphyrin nanostructures.     

Facile Synthesis and Enhanced Nonlinear Optical Properties of Porphyrin‐Functionalized Multi‐Walled Carbon Nanotubes

Two multi‐walled carbon nanotube (MWCNT)‐based nanohybrids, MWCNT–ZnTPP and MWCNT–TPP (TPP=5‐[4‐{2‐(4‐formylphenoxy)‐ ethyloxy}phenyl]‐10,15,20‐triphenylporphyrin, ZnTPP=5‐[4‐{(4‐formylphenyl)ethynyl}phenyl]‐10,15,20‐triphenylporphinatozinc(II)), were prepared directly from pristine MWCNTs through 1,3‐dipolar cycloaddition reactions. Covalent attachment of the porphyrins to the surfaces of the MWCNTs was confirmed by Fourier transform infrared spectroscopy, ultraviolet/visible absorption, fluorescence, Raman, and X‐ray photoelectron spectroscopy, elemental analysis, transmission electron microscopy, and thermogravimetric analysis. Attachment of the porphyrin moieties to the surface of the MWCNTs significantly improves the solubility and ease of processing of these MWCNT–porphyrin composite materials. Z‐scan studies reveal that these MWCNT–porphyrin nanohybrids exhibit enhanced nonlinear optical properties under both nanosecond and picosecond laser pulses at λ=532 nm in comparison with free MWCNTs and the free porphyrin chromophores, whereas superior optical limiting performance was displayed by MWCNT–porphyrin composite materials rather than MWCNTs/ZnTPP and MWCNTs/TPP blends, which is consistent with a remarkable accumulation effect as a result of the covalent linkage between the porphyrin and the MWCNTs.     

Phosphine-oxazoline ligands with an axial-unfixed biphenyl backbone: the effects of the substituent at oxazoline ring and P phenyl ring on Pd-catalyzed asymmetric allylic alkylation

A novel kind of chiral phosphine-oxazoline ligands 3 with an axial-unfixed biphenyl backbone bearing different substituent on oxazoline ring and P phenyl ring was prepared. These ligands exist as a mixture of two diastereomers in equilibrium in solution. Upon coordinated to Pd(II), however, only one of the two possible kinds of diastereomer complexes with different axial chirality was formed. These compounds as chiral ligands were applied in Pd-catalyzed asymmetric allylic alkylation with high reaction activity and enantioselectivity. Meanwhile, the asymmetric catalytic behavior was affected obviously by the substituent at oxazoline ring and P phenyl ring. The best result, up to 92.3% ee and 99% yield, was obtained with the ligand 3c having two phenyl groups on P and a phenyl group on oxazoline ring in this asymmetric catalysis reaction.     

Probing riboswitch-ligand interactions using thiamine pyrophosphate analogues

The Escherichia coli thiM riboswitch forms specific contacts with its natural ligand, thiamine pyrophosphate (TPP or thiamine diphosphate), allowing it to generate not only nanomolar binding affinity, but also a high degree of discrimination against similar small molecules. A range of synthetic TPP analogues have been used to probe each of the riboswitch-ligand interactions. The results show that the pyrimidine-sensing helix of thiM is exquisitely tuned to select for TPP by recognising the H-bonding donor and acceptors around its aminopyrimidine ring and also by forming π-stacking interactions that may be sensitive to the electronics of the ring. The central thiazolium ring of TPP appears to be more important for ligand recognition than previously thought. It may contribute to binding via long-range electrostatic interactions and/or by exerting an electron withdrawing effect on the pyrimidine ring, allowing its presence to be sensed indirectly and thereby allowing discrimination between thiamine (and its phosphate esters) and other aminopyrimidines found in vivo. The pyrophosphate moiety is essential for submicromolar binding affinity, but unexpectedly, it does not appear to be strictly necessary for modulation of gene expression.     

Intermolecular and intracomplex photoinduced electron transfer from planar and nonplanar metalloporphyrins to p-quinones

The rate constants of intermolecular photoinduced electron transfer from triplet excited states of metalloporphyrins to a series of p-benzoquinone derivatives in benzonitrile were determined to examine the effects of the driving force, the metal, and the conformational distortion of the porphyrin ring on the reorganization energies (λ) of electron transfer by laser flash photolysis. The λ values were evaluated from the determined rate constants on the basis of the Marcus theory of electron transfer. The λ values of planar metalloporphyrins, [Al(TPP)(PhCOO)] and [Zn(TPP)] (TPP(2-)=tetraphenylporphyrin dianion), are approximately the same, but they are 0.27 eV smaller than those of the corresponding nonplanar (saddle-distorted) metalloporphyrins [Al(DPP)(PhCOO)] and [Zn(DPP)] (DPP(2-)=dodecaphenylporphyrin dianion) when they are compared for the same driving force of photoinduced electron transfer. The axial ligand PhCOO(-) of [Al(TPP)](+) and [Al(DPP)](+) was replaced by anthraquinone-2-carboxylate (AqCOO(-)) to afford the electron donor-acceptor complexes [Al(TPP)(AqCOO)] and [Al(DPP)(AqCOO)], respectively. The X-ray crystal structure of [Al(TPP)(AqCOO)] revealed strong coordination of AqCOO(-) to the Al(3+) ion of [Al(TPP)](+) and the existence of π-π interactions between AqCOO(-) and the porphyrin ring. In the case of the saddle-distorted [Al(DPP)(AqCOO)], however, the AqCOO(-) moiety is nearly perpendicular to the porphyrin ring. The photodynamics of intracomplex photoinduced electron transfer from the singlet excited state of [Al(TPP)](+) and [Al(DPP)](+) to the AqCOO(-) moiety were also examined in comparison with the intermolecular photoinduced electron-transfer reactions, and the determined rate constants were evaluated in light of the Marcus theory of electron transfer to reveal that the electron transfer is adiabatic in each case.     

Stereochemistry of Substitution of the α-Dimethylamino Group by Dialkylzinc in Chiral Benzylferrocene

The stereochemistry of the substitution of the α-dimethylamino group by dimethylzinc in the presence of acetyl chloride in the chiral benzylferrocene backbone was examined. The reaction with the benzylferrocene bearing an o-bromo substituent at both ferrocene and the phenyl ring proceeded with inversion of configuration, while the reaction with the benzylferrocene bearing an o-bromo substituent at either ferrocene or the phenyl ring proceeded with retention of configuration.     

Comparative Raman spectroscopy study of sulfonate-substituted triphenylphosphines

A comparative Raman spectroscopy study of triphenylphosphine (TPP), monosulfonated triphenylphosphine (TPPMS) and trisulfonated triphenylphosphine (TPPTS) is reported. The characteristic modes for each molecule were evidenced and we suggest assignments for the majority of the modes. A detailed study of the phenyl breathing mode (around 1000 cm⁻¹) shows that in the case of TPP, the three rings are nonequivalent, whereas for TPPTS, the sulfonate substituant seems to contribute to stabilise the molecule structure so as the rings are equivalent. The TPPMS spectrum is a medium case between the extreme cases of TPP and TPPTS and presents the characteristics of the two previous spectra.     

An ab initio investigation of the interactions involving the aromatic group of the set of fluorinated N-(4-sulfamylbenzoyl)benzylamine inhibitors and human carbonic anhydrase II

In this work we investigate the interactions that occur between the aromatic portion of the set of fluorinated N-(4-sulfamylbenzoyl)benzylamine (SBB) inhibitors and two residues of Human Carbonic Anhydrase II (HCAII), namely Phe-131 and Pro-202. Calculations were carried out at the MP2/aug-cc-pVDZ level of theory and the counterpoise scheme of Boys and Bernardi was employed to account for the basis set superposition error. The most striking result obtained here is that the SBB phenyl ring interacts at least as strongly with the proline pyrrolidine ring as with the phenylalanine phenyl ring, which is surprising because aromatic-aromatic interactions have long been thought to be particularly favorable in protein and protein-ligand structure. Comparison of the MP2 binding energies to those obtained with the Hartree-Fock method indicates that the attraction between the proline pyrrolidine ring and the SBB phenyl ring is largely attributable to dispersion forces. These favorable interactions between pyrrolidine and phenyl rings may have important implications in protein structure because there is potential for proline residues to interact with phenylalanine residues in a fashion analogous to that seen here. A preliminary protein data bank search indicates that the proline-phenylalanine contacts are about 40% as common as those between two phenylalanines. It is also found here that the number and pattern of fluorine substituents on the SBB phenyl ring is much less important in determining the SBB-HCAII binding energy than the relative geometric configuration of the interacting pairs.