NMR spectrometric studies of complexation of [60]fullerene with series of meso-tetraphenylporphyrins

Extensive 1H NMR spectrometric studies have been done to gain information on the nature of molecular interactions of the supramolecular complexes of [60]fullerene with a series of meso-tetraphenylporphyrins, namely, meso-5,10,15,20-tetraphenylporphyrin (1), meso-5,10,15,20-tetra-2-bromophenyl-porphyrin (2) and meso-5,10,15,20-tetra-2-chlorophenyl-porphyrin (3) in toluene medium. [60]Fullerene has been shown to form 1:1 adducts with the above series of meso-tetraphenylporphyrins. Formation constants (K) for all the complexes have been determined from the systematic variation of the NMR chemical shifts of beta proton of the porphyrin in presence of [60]fullerene. It has been observed that 3 acts as a better donor in forming supramolecular complex with [60]fullerene.     

Supramolecular Architectures by Fullerene‐Bridged Bis(permethyl‐β‐cyclodextrin)s with Porphyrins

The Hirsch–Bingel reaction of bis{4‐methyl[1,2,3]triazolyl}malonic ester‐bridged bis(permethyl‐β‐cyclodextrin) 1 with C₆₀ has led to the formation of a new fullerene‐bridged bis(permethyl‐β‐cyclodextrin) 2 , which has been comprehensively characterized by NMR spectroscopy, MALDI‐MS, and elemental analysis. Taking advantage of the high affinity between 2 and 5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphyrin ( 3 ) or [5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphinato]zinc(II) ( 4 ), linear supramolecular architectures with a width of about 2 nm and a length ranging from hundreds of nanometers to micron dimension were conveniently constructed and fully investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Significantly, the photoinduced electron‐transfer (PET) process between porphyrin and C₆₀ moieties takes place within the 2 ? 3 and 2 ? 4 supramolecular architectures under light irradiation, leading to the highly efficient quenching of the porphyrin fluorescence. The PET process and the charge‐separated state were investigated by means of fluorescence spectroscopy, fluorescence decay, cyclic voltammetry, and nanosecond transient absorption measurements.     

烟酸-卟啉二元化合物的合成、表征及其电化学性质

通过亲核取代反应合成了3个新的烟酸-卟啉二元化合物, 并用红外光谱、紫外-可见光谱、核磁共振氢谱、元素分析和质谱对化合物的结构进行确认, 通过循环伏安法研究了其电化学性质.     

Synthesis and properties of ms- and β-substituted Pt(II) and Pt(IV) tetraphenylporphyrinates

The interaction of 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra-(4-chlorophenyl)porphyrin, 2-bromo-5,10,15,20-tetraphenylporphyrin, and 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin with platinum(II) chloride in boiling phenol has been studied. The corresponding platinum(II) porphyrinates have been synthesized; their subsequent treatment with bromine in chloroform resulted in platinum(IV) porphyrinates. The Pt(II) and Pt(IV)(Br)₂ porphyrinates have been identified by elemental analysis, electron absorption, IR, and ¹H NMR spectroscopy.     

Photophysical and electrochemical properties of meso-substituted thien-2-yl Zn(II) porphyrins

The influence of the thiophene ring on the ground and excited state properties of the porphyrin ring is investigated, when substituted at the meso-position. A series of mono-, di-, tri-, and tetra- meso-thien-2-yl porphyrins are studied and discussed with respect to the reference compounds zinc(II)-5,10,15,20-tetra(thien-2'-yl)porphyrin ( 1a) and zinc(II)-5,10,15,20-tetraphenylporphyrin (ZnTPP). The extended conjugated system zinc(II)-5-(5'-(5'-ethynyl-2'-thiophenecarboxaldehyde)thien-2'-yl)-10,15,20-triphenylporphyrin ( 4d) is also studied and shows enhanced charge transfer character due to the presence of the terminal aldehyde accepting group. A detailed analysis of ground and excited state UV-vis absorption, steady-state and time-resolved fluorescence, laser flash photolysis, and electrochemical data all point toward substantial electronic communication between the central Zn(II) porphyrin ring and the meso-thien-2-yl substituents, which is evident from excited state charge transfer character.     

Energy and electron transfer in polyacetylene-linked zinc-porphyrin-[60]fullerene molecular wires

The synthesis and electrochemical and photophysical studies of a series of alkyne-linked zinc-porphyrin-[60]fullerene dyads are described. These dyads represent a new class of fully conjugated donor-acceptor systems. An alkynyl-fullerene synthon was synthesized by a nucleophilic addition reaction, and was then oxidatively coupled with a series of alkynyl tetra-aryl zinc-porphyrins with 1-3 alkyne units. Cyclic and differential pulse voltammetry studies confirmed that the porphyrin and fullerene are electronically coupled and that the degree of electronic interaction decreases with increasing length of the alkyne bridge. In toluene, energy transfer from the excited zinc-porphyrin singlet to the fullerene moiety occurs, affording fullerene triplet quantum yields of greater than 90 %. These dyads exhibit very rapid photoinduced electron transfer in tetrahydrofuran (THF) and benzonitrile (PhCN), which is consistent with normal Marcus behavior. Slower rates for charge recombination in THF versus PhCN clearly indicate that charge-recombination events are occurring in the Marcus inverted region. Exceptionally small attenuation factors (beta) of 0.06+/-0.005 A(-1) demonstrate that the triple bond is an effective mediator of electronic interaction in zinc-porphyrin-alkyne-fullerene molecular wires.     

Design, synthesis, and photophysical studies of a porphyrin-fullerene dyad with parachute topology; charge recombination in the marcus inverted region

As part of a continuing investigation of the topological control of intramolecular electron transfer (ET) in donor-acceptor systems, a symmetrical parachute-shaped octaethylporphyrin-fullerene dyad has been synthesized. A symmetrical strap, attached to ortho positions of phenyl groups at opposing meso positions of the porphyrin, was linked to [60]-fullerene in the final step of the synthesis. The dyad structures were confirmed by (1)H, (13)C, and (3)He NMR, and MALDI-TOF mass spectra. The free-base and Zn-containing dyads were subjected to extensive spectroscopic, electrochemical and photophysical studies. UV-vis spectra of the dyads are superimposable on the sum of the spectra of appropriate model systems, indicating that there is no significant ground-state electronic interaction between the component chromophores. Molecular modeling studies reveal that the lowest energy conformation of the dyad is not the C(2)(v)() symmetrical structure, but rather one in which the porphyrin moves over to the side of the fullerene sphere, bringing the two pi-systems into close proximity, which enhances van der Waals attractive forces. To account for the NMR data, it is proposed that the dyad is conformationally mobile at room temperature, with the porphyrin swinging back and forth from one side of the fullerene to the other. The extensive fluorescence quenching in both the free base and Zn dyads is associated with an extremely rapid photoinduced electron-transfer process, k(ET) approximately 10(11) s(-)(1), generating porphyrin radical cations and C(60) radical anions, detected by transient absorption spectroscopy. Back electron transfer (BET) is slower than charge separation by up to 2 orders of magnitude in these systems. The BET rate is slower in nonpolar than in polar solvents, indicating that BET occurs in the Marcus inverted region, where the rate decreases as the thermodynamic driving force for BET increases. Transient absorption and singlet molecular oxygen sensitization data show that fullerene triplets are formed only with the free base dyad in toluene, where triplet formation from the charge-separated state is competitive with decay to the ground state. The photophysical properties of the P-C(60) dyads with parachute topology are very similar to those of structurally related rigid pi-stacked P-C(60) dyads, with the exception that there is no detectable charge-transfer absorption in the parachute systems, attributed to their conformational flexibility. It is concluded that charge separation in these hybrid systems occurs through space in unsymmetrical conformations, where the center-to-center distance between the component pi-systems is minimized. Analysis of the BET data using Marcus theory gives reorganization energies for these systems between 0.6 and 0.8 eV and electronic coupling matrix elements between 4.8 and 5.6 cm(-)(1).     

Formation, spectral, electrochemical, and photochemical behavior of zinc N-confused porphyrin coordinated to imidazole functionalized fullerene dyads

Donor-acceptor dyads were constructed using zinc N-confused porphyrin (ZnNCP), a structural isomer of zinc tetraphenylporphyrin, as a donor, and fullerene as an electron acceptor. Two derivatives, pyridine-coordinated zinc N-confused porphyrin (Py:ZnNCP) and the zinc N-confused porphyrin dimer (ZnNCP-dimer) were utilized to form the dyads with an imidazole-appended fulleropyrrolidine (C60Im). These porphyrin isomers formed well-defined 1:1 supramolecular dyads (C60Im:ZnNCP) via axial coordination. The dyads were characterized by optical absorption and emission, ESI-mass, 1H NMR, and electrochemical methods. The binding constant, K, was found to be 2.8 x 10(4) M(-1) for C60Im:ZnNCP. The geometric and electronic structure of C60Im:ZnNCP were probed by using DFT B3LYP/3-21G methods. The HOMO was found to be on the ZnNCP entity, while the LUMO was primarily on the fullerene entity. The electrochemical properties of C60Im:ZnNCP was probed using cyclic voltammetry in o-dichlorobenzene, 0.1 n-Bu4NClO4. The Py:ZnNCP was found to be easier to oxidize by over 340 mV compared to Py:ZnTPP. Upon dyad formation via axial coordination, the first oxidation revealed an anodic shift of nearly 90 mV. Evidence of photoinduced charge separation from the singlet excited ZnNCP to the appended fullerene was established from time-resolved emission and nanosecond transient absorption studies.     

Photophysical investigations on non-covalently linked fullerene/tetraarylporphyrin supramolecular complexes

The host-guest interactions of various tetraarylporphyrins (TP), viz., 5,10,15,20-tetraphenyl-21H,23H-porphyrin (1), 5,10,15,20-tetrakis(octadecyloxyphenyl)-21H,23H-porphyrin (2) and 5,10,15,20-tetrakis(dodecyloxyphenyl)-21H,23H-porphyrin (3) with C60 and C70 have been studied by 1H NMR, UV-vis and fluorescence spectroscopic techniques in toluene medium. All the fullerene/porphyrin complexes are found to be stable with 1:1 stoichiometry. Binding constants (K) of all the fullerene/porphyrin complexes have been determined by fluorescence quenching experiment. The trend in K values revealed that the presence of long chain n-alkyl group in tetraarylporphyrin effectively and remarkably increases the selectivity ratio of C70 over C60. Theoretical calculations have extended a good support in interpreting the stability difference between various fullerene/TP complexes.     

Porphyrin–Fullerene Dyad Based on Indium(III) Complex. Donor–Acceptor Complex Formation Equilibrium

Formation kinetics and spectral properties of the donor–acceptor complexes of (5,10,15,20- tetra(2-methoxyphenyl)porphinato)chloroindium(III) with 2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin- 2-yl)methylpyrrolidinyl[3′,4′:1,2][60]fullerene were studied. The formation of the donor–acceptor dyad [(Py₃F)InTPP(2-OCH₃)₄]⁺Cl^– occurs as a two-step reaction, including fast reversible coordination of the fullerene base molecule and slow irreversible displacement of the axial chloride ion to the second coordination sphere. Quantitative characteristics for the reaction rate and equilibrium were obtained. The reaction products were identified by IR and ¹H NMR spectroscopy. The most important electron optical and stability parameters of the porphyrin–fullerene dyads with inner- and outer-sphere chloride ions were determined. These results are important for studies of the photophysics of porphyrin–fullerene dyads and development of photoconverters based on them.     

Study on the inclusion behavior between meso-tetrakis[4-(3-pyridiniumpropoxy)phenyl]prophyrin tetrakisbromide and beta-cyclodextrin derivatives in aqueous solution

The interaction of a cationic water-soluble porphyrin, 5,10,15,20-tetrakis[4-(3-pyridiniumpropoxy)phenyl]prophyrin tetrakisbromide (TPPOC3Py), with beta-CD and HP-beta-CD in aqueous solution has been studied by UV-vis, 1H NMR, 2D-NOESY and MALDI-TOF MS, and it reveals that a stable 1:1 inclusion complex between TPPOC3Py and HP-beta-CD or beta-CD has formed, in which one of the meso substituents of porphyrin ring has deeply penetrated through the cavity of HP-beta-CD from secondary face. The inclusion constants of the complexes of TPPOC3Py-beta-CD and TPPOC3Py-HP-beta-CD are (1.6+/-0.2)x10(3) M-1 and (8.9+/-0.4)x10(4) M-1, respectively.     

Holmium porphyrin compound liquid crystals: Synthesis and properties

5,10,15,20-Tetra-[(p-alkoxy-m-ethyloxy)phenyl]porphyrin and [5-(p-alkoxy)phenyl-10,15,20-tri-phenyl]porphyrin and their holmium(III) complexes are reported. They display a hexagonal columnar discotic columnar (Col_h) liquid crystal phase and were studied by cyclic voltammetry, surface photovoltage spectroscopy (SPS), electric-field-induced surface photovoltage spectroscopy (EFISPS) and luminescence spectroscopy. Within the accessible potential window, all these compounds exhibit two one-electron reversible redox reactions. Quantum yields of Q band are in the region 0.0045–0.21 at room temperature. The SPS and EFISPS reveal that all the compounds are p-type semiconductors and exhibit photovoltaic response due to π–π^* electron transitions.     

New porphyrin-polyoxometalate hybrid materials: synthesis, characterization and investigation of catalytic activity in acetylation reactions

New hybrid complexes based on covalent interaction between 5,10,15,20-tetrakis(4-aminophenyl)porphyrinatozinc(ii) and 5,10,15,20-tetrakis(4-aminophenyl)porphyrinatotin(iv) chloride, and a Lindqvist-type polyoxometalate, Mo(6)O(19)(2-), were prepared. These new porphyrin-polyoxometalate hybrid materials were characterized by (1)H NMR, FT IR and UV-Vis spectroscopic methods and cyclic voltammetry. These spectro- and electrochemical studies provided several spectral data for synthesis of these compounds. Cyclic voltammetry showed the influence of the polyoxometalate on the redox process of the porphyrin ring. The catalytic activity of tin(iv)porphyrin-hexamolybdate hybrid material was investigated in the acetylation of alcohols and phenols with acetic anhydride. The reusability of this catalyst was also investigated.     

Lanthanide Complexes with Acetylacetonate and 5,10,15,20-Tetra[para-(4-chlorobenzoyloxy)phenyl]porphyrin

The lanthanide complexes of acetylacetonate and5 ,1 0 ,1 5 ,2 0 - tetra[para- (chlorobenzoy-loxy) phenyl] porphyrin having a general formula Ln[(cbop) 4 p] acac(where Ln=Tb,Ho,Er,Tm;cbop=(4- chlorobenzoyloxy) phenyl;Hacac=acetylacetone;p=porphyrin) wereprepared and characterized.The structure of the complexs was proposed.Metalloporphyrins have been providing an active research field since the beginning of thiscentury because of their involvementin various chemical and biological processes.T…     

四(4－N-吡啶基)卟啉衍生物的合成及表征

阳离子卟啉配体;配合物;还原电位;四(4－N-吡啶基)卟啉衍生物的合成及表征     

Interaction of water-soluble cationic porphyrin with anionic surfactant

The interaction of a cationic water-soluble porphyrin, 5,10,15,20-tetrakis [4-(3-pyridiniumpropoxy)phenyl]porphyrin tetrakisbromide (TPPOC3Py), with anionic surfactant, sodium dodecyl sulfate (SDS), in aqueous solution has been studied by means of UV-vis, (1)H NMR, fluorescence, circular dichroism (CD) spectra and dynamic laser light scattering (DLLS), and it reveals that TPPOC3Py forms porphyrin-surfactant complexes (aggregates), including ordered structures J- and H-aggregates, induced by association with surfactant monomers below the SDS critical micelle concentration (cmc), and forms micellized monomer upon the cmc, respectively. The position of TPPOC3Py in the micelle is determined, which is not in the micelle core instead of intercalated among the SDS chains, most likely with the pyridinium group extending into the polar headgroup region of the micelle.     

Spectrophotometric study of the charge transfer complexation of some porphyrin derivatives as electron donors with tetracyanoethylene

Charge transfer complexes (CTC) of 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetra(4-tolyl)porphyrin (TTP), 5,10,15,20-tetra(4-methoxyphenyl)porphyrin (TMP), Zn-5,10,15,20-tetraphenylporphyrin (Zn-TPP), and Zn-5,10,15,20-tetra(4-tolyl)porphyrin (Zn-TTP) with tetracyanoethylene (TCNE) have been studied at various temperatures in CH(2)Cl(2) and CCl(4). The data are discussed in terms of equilibrium constant (K(CT)), molar extinction coefficient (varepsilon(CT)), thermodynamic standard reaction quantities (DeltaG degrees , DeltaH degrees and DeltaS degrees ), oscillator strength (f), and transition dipole moment (mu). The spectrum obtained for TPP/TCNE, TTP/TCNE, and TMP/TCNE systems shows two main absorption bands at 475 and 690nm, which are not due to the absorption of any of the reactants. These bands are characteristic of an intermolecular charge transfer involving the overlap of the lowest unoccupied molecular orbital (LUMO) of the acceptor with the highest occupied molecular orbital (HOMO) of the donor. The results reveal that the interaction between the donors and acceptor is due to pi-pi(*) transitions by the formation of radical ion pairs. The stoichiometry of the complexes was found to be 1:1 ratio by the Job and straight line methods between donors and acceptor with the maximum absorption bands at wavelengths of 475 and 690nm. The observed data show salvation effects on the spectral and thermodynamics properties of CTC. The ionization potential of the donors and the dissociation energy of the CTC were also determined and are found to be constant.     

Cellular uptake and photocytotoxicity of glycoconjugated chlorins in HeLa cells

Eight 5,10,15,20-tetrakis[3- or 4-(beta-D-glycopyranosyloxy)phenyl]chlorins were synthesized by means of the Whitlock method with diimide reduction and purified by reversed-phase thin layer chromatography (RP-TLC). All compounds were characterized by (1)H NMR spectroscopy, electron-spray ionization time-of-flight mass spectrometry (ESI-TOF MS), and UV-Vis spectroscopy. ESI-TOF MS could detect the 2H difference in molecular weight between a glycoconjugated chlorin and its corresponding porphyrin (i.e., 5,10,15,20-tetrakis[3- or 4-(beta-D-glycopyranosyloxy)phenyl]porphyrin). The cellular uptake of the eight chlorins was evaluated in HeLa cells. All glycoconjugated chlorins showed higher cellular uptake than tetraphenylporphyrin tetrasulfonic acid (TPPS), and 5,10,15,20-tetrakis[3-(beta-D-xylopyranosyloxy)phenyl]chlorin showed 50-fold higher uptake than TPPS. The photocytotoxicity of 5,10,15,20-tetrakis[3-(beta-D-glucopyranosyloxy)phenyl]chlorin, 5,10,15,20-tetrakis[3-(beta-D-xylopyranosyloxy)phenyl]chlorin and TPPS towards HeLa cells was examined at the concentration of 2x10(-7) M (mol/dm(3)). These photosensitizers had no cytotoxicity in the dark, but their photocytotoxicity decreased in the order of 5,10,15,20-tetrakis[3-(beta-D-glucopyranosyloxy)phenyl]chlorin>5,10,15,20-tetrakis[3-(beta-D-xylopyranosyloxy)phenyl]chlorin>TPPS. The results indicate that the photocytotoxicity is not related simply to cellular uptake.     

A Schiff-base porphyrin complex with double intramolecular hydrogen bonds

We have designed a porphyrin with a Schiff-base substituent as a model to study intramolecular hydrogen-bonding. The corresponding complex [Zn(SATPP)(CH₃OH)] has been synthesized and characterized by X-ray crystallography, ¹H NMR, and UV-Vis spectroscopy. The structure shows that there are three phenyl groups and one salicylideneaminophenyl group at the meso positions of the porphyrin, and the phenol oxygen is involved in double hydrogen bonds, one within the salicylideneaminophenyl and the other between coordinated methanol and phenol oxygen. ¹H NMR spectra suggest that the binding of methanol to zinc is an equilibrium process in solution and the equilibrium constant has been determined by UV-Vis measurements. The intramolecular hydrogen bond stabilizes the structure, and the binding affinity increases 10 times over the corresponding TPP (TPP, dianion of meso-5,10,15,20-tetraphenylporphyrin).     

Synthesis and characterization of transition metal complexes of dimeric N-confused porphyrin linked by an o-xylene fragment

Insertion of nickel(II), zinc, cadmium, or silver(III) into both macrocyclic crevices of 2,2'-o-xylene-bis(5,10,15,20-tetrakis(p-tolyl)-2-aza-21-carbaporphyrin) results in homometallic dimeric complexes which were isolated and characterized by NMR, UV-vis, mass spectrometry, and cyclic voltammetry. The 1H NMR study of these systems at low temperatures (203-233 K) allowed determination of most stable conformers with respect to a rotational freedom around the xylene bridge. An unfolded conformation for the dicationic bis(silver(III)) complex was determined on the basis of 2D nuclear Overhauser effect spectrometry experimentation. A mixture of nonequally populated diastereomers is observed for bis(zinc) and bis(cadmium) complexes due to a possibility of two different orientations of the apical anionic ligands with respect to the bridge. In a reaction of 5,10,15,20-tetrakis(p-tolyl)-2-aza-21-carbaporphyrinato nickel(II) with 2-(o-bromoxylene)-5,10,15,20-tetrakis(p-tolyl)-2-aza-21-carbaporphyrin in the presence of a proton scavenger, two isomeric bis(N-confused porphyrin) complexes with one subunit "empty" and the other metalated by nickel(II) were obtained. In the product 10, the o-xylene links external nitrogens of the subunits while product 11 consists of the xylene bridge between external nitrogen of the nonmetalated subunit and internal carbon of the fragment containing a nickel(II) ion. The products were characterized by mass spectrometry, UV-vis, NMR, and, in the case of complex 11, also by X-ray crystallographic analysis (space group P1, a =17.007(3), b = 18.130(3), c = 18.797(2) A, alpha = 105.856(13) degrees, beta = 107.447(13) degrees, gamma = 98.818(15) degrees, V = 5141.1(15) A3, Z = 2). Insertion of zinc or silver(III) into an empty crevice of 10 resulted in heterometallic zinc-nickel(II) or silver(III)-nickel(II) complexes 12 or 13, respectively, which were characterized by NMR, UV-vis, and cyclic voltammetry. The subunits in the bis(porphyrin) systems retain spectroscopic and redox properties typical for monomeric complexes.