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Two novel p-functionalized push-pull zinc porphyrins with amine or phenyl push-groups and cyclic imide or carboxylic esters pull-groups have been newly synthesized for light energy harvesting applications. The ethynylphenyl spacers extended the conjugation of the porphyrin [pi]-systems, as reflected by their red-shifted absorbance and fluorescence spectra. Computational studies performed at the B3LYP/6-31G* level indicated no steric hindrance between the porphyrin w-system and the substituents. The calculated HOMO and LUMO orbitals displayed significant delocalization in 1, where the electron density in the HOMO was localized over the push groups, whereas the LUMO was extended over the porphyrin [pi]- and pull-groups. On the other hand, 2 did not display significant orbital segregation, which is attributed to its weaker push-pull character. Electrochemical studies revealed smaller HOMO-LUMO gaps for the push-pull zinc porphyrins. As a consequence of the push-pull effects, reduction in fluorescence intensity and lifetime was observed. Femtosecond transient absorption spectral studies revealed successful formation of singlet excited state in both of the push-pull porphyrins. Donor-acceptor conjugates were subsequently built and characterized by coordinating an electron acceptor, [C.sub.60]Im, via metal-ligand axial coordination. Efficient photo-induced charge separation in both donor-acceptor conjugates was witnessed wherein the charge-separated states persisted tens of nanoseconds prior returning to the ground state. Key words: push-pull zinc porphyrin, fullerene, metal-ligand axial coordination, photoinduced electron transfer. Nous avons realise la premiere synthese de deux nouvelles porphyrines-zinc de type<< push-pull>>fonctionnalisees en positions p, dans lesquelles les groupes electrodonneurs sont des amines ou des groupes phenyl et les groupes electroattracteurs, un imide cyclique ou des esters carboxyliques, en vue d'applications de recuperation d'energie lumineuse. Les groupes ethynylphenyl tenaient lieu d'espaceurs servant a etendre les systemes de conjugaison [pi]des porphyrines, comme en temoigne le deplacement vers le rouge des spectres d'absorbance et de fluorescence de ces composes. Des etudes de modelisation realisees au niveau B3LYP/6-31G (*) n'ont pas revele d'encombrement sterique entre le systeme w des porphyrines et leur substituants. La modelisation des orbitales HOMO et LUMO du compose 1 a revele une delocalisation importante, la densite electronique de la HOMO etant localisee sur les groupes electrodonneurs, tandis que la LUMO s'etendait sur le systeme w de la porphyrine et les groupes electroattracteurs. Par contre, le compose 2 n'a pas presente de segregation orbitalaire marquee, ce qui s'explique par son caractere << push-pull >> plus faible. Des etudes electrochimiques menees sur les porphyrines-zinc de type << push-pull >> ont revele que leurs bandes interdites HOMO-LUMO etaient plus etroites. Les effets de type << push-pull >> se sont traduits par une reduction de l'intensite et de la duree de vie de la fluorescence. L'analyse des spectres d'absorption des especes transitoires a l'echelle de la femtoseconde a revele que les deux porphyrines de type<>donnaient lieu a la formation d'un etat excite singulet. Nous avons par la suite forme les conjugues donneur-accepteur par coordination axiale metal-ligand d'un accepteur d'electron, le [C.sub.60]Im, et nous les avons caracterises. Nous avons observe qu'une separation de charge photo-induite se produisait efficacement dans les deux conjugues donneur-accepteur, et que ces etats de separation de charge ont persiste des dizaines de nanosecondes avant de revenir a l'etat fondamental. [Traduit par la Redaction] Mots-cles: porphyrine zinc de type <>, fullerene, coordination axiale metal-ligand, transfert electronique photo-induit., Introduction Push-pull porphyrins have been of intense research interest in recent years owning to their exceptional performance in dyesensitized solar cells. (1-5) The important roles of the push (electrondonating) and [...]

A melamine piezomicrogravimetric (acoustic) chemosensor using a molecularly imprinted polymer (MIP) film has been devised and tested. The MAP films were prepared by electropolymerization of the melamine complexed by the functional monomer of the bis(bithiophene) derivative bearing an 18-crown-6 substituent 4. The structure of the MIP--melamine complex was visualized by the DFr B3LYP/3-21G(*) energy optimization calculations. The sensitivity and selectivity of the MIP film was improved by cross-linking the polymer with the bithianaphthene monomer 5 and the presence of the porogenic ionic liquid in the prepolymerization solution. After electropolymerization, the melamine template was extracted from the MIP film with an aqueous strong base solution. The measurements of UV--vis spectroscopy, X-ray photoelectron spectroscopy (XPS), DPV, and EIS as well as scanning electrochemical microscopy (SECM) imaging confirmed extraction of the melamine template from the MIP film and then rebinding of the melamine analyte while the film relative roughness and porosity was determined by atomic force microscopy (AFM) and scanning electron microscopy (SEM) imaging, respectively. The analytical as well as kinetic and thermodynamic parameters of the chemosensing were assessed under flow-injection analysis (FIA) conditions with piezoelectric microgravimetry (PM) detection. The linear concentration range for melamine detection was 5 nM to at least 1 mM with a limit of detection of ~5 nM. The chemosensor successfully discriminated the cyanuric acid, cyromazine, and ammeline interfering agents. 10.1021/ac9020352

A histamine piezoelectric (acoustic) sensor using a molecularly imprinted polymer (MIP) film has been devised and tested. The sensor comprises an electrodeposited MIP film as the recognition element and a 10 MHz AT-cut shear-thickness-mode bulk-acoustic-wave quartz crystal resonator with Pt film electrodes as the signal transducer. Preparation of the sensing film involved two consecutive electrochemical polymerizations, performed under cyclic voltammetric conditions, with the use of a supporting electrolyte of 0.1 M tetra-n-butylammonium perchlorate in acetonitrile. First, a poly(bithiophene) barrier film was deposited by electropolymerization on the Pt/quartz resonator to prevent histamine electro-oxidation and avoid possible contamination of the Pt electrode surface. Next, the histamine-templated MIP film was deposited by electropolymerization on top of this barrier film. For that purpose, two functional monomers of bis(bithiophene) derivatives, i.e., one bearing the 18-crown-6 and the other dioxoborinane substituent, were copolymerized in the presence of the histamine template. The consecutive growth of both these overlaid films was monitored with an electrochemical quartz crystal microbalance (EQCM). Subsequently, the histamine was extracted from MIP with 0.01 M NaOH for 12 h. The UV-vis and X-ray photoelectron spectroscopic measurements confirmed the completeness of the removal of the histamine template from the MIP film. The analytical performance of the chemosensor was assessed under flow injection analysis (FIA) conditions using the carrier 0.5 M HEPES buffer (pH = 7.5) solution and the piezoelectric microgravimetry detection at QCM. The negative peaks of resonant frequency linearly decreased with the increase of the histamine concentration in the range 10-100 mM for 150/[micro]L/min flow rate, and 100 [micro]L volume of the injected sample. The sensitivity of the chemosensor (0.33 Hz/mM) was more than twice as that of the chemosensor without the poly(bithiophene) barrier film (0.15 Hz/mM). The chemosensor performance was superior for selective histamine recognition if the poly(bithiophene) barrier film thickness exceeded 200 nm. The chemosensor discriminated histamine from functionally or structurally similar compounds, such as dopamine, tryptamine, and imidazole. Stability constants of the affinity complexes of MIP and analyte or the interfering agent were determined from kinetic studies. For the MIP--histamine complex, the stability constant thus evaluated was equal to 57.0 [M.sup.-1] being much higher than those for the MIP--tryptamine and MIP--dopamine complexes determined to be 10.7, and 6.4 [M.sup.-1], respectively. The concentration limit of detection was as low as 5 nM histamine if the carrier solution flow rate was as low as 35 [micro]L/min and the injection sample volume as large as 1 mL.

The influence of solvent polarity and hydrogen bonding on the electronic absorption spectra of solvatochromic dyes is studied. Results demonstrate that the 4-oxocyclohexadienylidene porphyrinogens are capable of binding anionic species such as the halides and other more complex anions.

Zinc N-confused porphyrin (ZnNCP), a structural isomer of zinc tetraphenylporphyrin, were used to construct donor-acceptor dyads, as a donor and fullerene as an electron acceptor, with imidazole-appended fulleropyrrolidine and are characterized by optical absorption and emission, ESI-mass, NMR and electrochemical methods. Evidence of photoinduced charge separation from the singlet excited ZnNCP to the appended fullerene is established from time-resolved emission and nanosecond transient absorption studies.

The effect of K(super +)-induced dimerization of tetrakis(benzo-15-crown-5)porphyrin and its metal derivatives on the redox, optical, and ESR behavior is reported. Electrochemical HOMO-LUMO energy levels revealed destabilization of HOMO and stabilization of LUMO upon dimerization.

The structures and electrochemistry of N-benzylated meso-tetrakis (3,5-di-tert-butyl-4-oxo-cyclohexa-2,5-dienylidene) porphyrinogens are investigated. The electrochemical analyses emphasize the electron deficiency of the N-benzylated meso-tetra(oxo-cyclohexadienylidene) porphyrinogens and indicate that they can be considered as quinones conjugated via the unsaturated tetrapyrrolic macrocycle.

A supramolecular triad constructed via axially coordinating imidazole-appended fulleropyrrolidine was shown to be successful model of the photosynthetic antenna-reaction center complex. Efficient energy transfer successfully mimics the combined antenna-reaction center in the natural photosynthesis process.

Research has been conducted on molecular triads composed of ferrocene C (sub)60 and nitroaromatic entities. The synthesis and physicochemical characterization of these triads have been carried out, and the results are presented.

Research has been conducted on the oligosaccharides which contain beta-arabinofuranosyl residues. The synthesis of these oligosaccharides has been carried out and the results indicate that the key step in the target preparation is a low-temperature glycosylation reaction.

Research has been conducted on the free-base and zinc(II) porphyrins that bear multiple hydroquinone entities at the meso positions. Results indicate that these porphyrins bind quinones in solutions by a quinhydrone pairing mechanism.

A new technique for investigating proximity effects in porphyrin-fullerene dyads by using an axial ligand coordination controlled 'tail-on' and 'tail-off' binding mechanism has been developed. There is evidence of the presence of some through-space interactions between the singlet excited zinc porphyrin and C60 moiety in the 'tail-off' form.

Research has been conducted on the dimethyl azo(bisisobutyrate). The thermal decomposition of this compound in a solution that contains C (sub)60 has been investigated and the results are presented.

The reactions of C60 with azo(bisisobutyronitrile) (AIBN) were studied to gain an insight into the early stages of the polymerizations. The reductions of 1,4- and unidentified isomers by cyclic voltammetry were also examined while UIV-vis-NIR spectra of the mono- and dianions produced electrochemically were noted. Results provide evidence that a third isomer is more electron deficient than C60 as shown by positively shifted first and second redox potentials.

Noncovalently linked electron donor-acceptor complexes made up of zinc tetraphenylporphyrin or zinc octaethylporphycene as donor and pyridine appended C60, py-C60, as acceptor, have been synthesized by the axial coordination of zinc. Nuclear magnetic resonance spectroscopy reveals a 1:1 stoichiometric ratio between the donor-acceptor pair. The K values follow the oxidation potential of the zinc tetrapyrrole while the thermodynamic parameters indicate stable complexation. The efficient quenching of the excited zinc tetrapyrrole occurs when the C60 bearing pyridine is axially ligated.

The electrochemistry and spectroelectrochemistry of (TPPBrx)Co dissolved in CH2Cl2 with weakly coordinating tetra-n-butylammonium hexafluorophosphate (TBA)PF6 has been studied. TPPBrx is the dianion of beta-brominated-pyrrole tetraphenylporphyrin and x is from O to 8. The reaction of CO with singly oxidized ((TPPBrx)Co)(super +) has also been investigated. The increasing nonplanarity of (TPPBrx)Co macrocycle with increasing Br groups was also looked into to find out if it would affect the binding of CO by in situ generated ((TPPBrx)Co)(super +).

An experiment was conducted which related to research on oligosaccharides containing furanose moieties. The study was conducted as part of a program focused on the synthesis of furanose oligosaccharides and aimed to develop alternative routes to furanose monosaccharides that could be converted to suitable glycosylating agents. It will be demonstrated that acetylated pyranose glycals can be converted efficiently to furanose glycosyl donors and, in turn, oligosaccharides.

Several reports have considered the properties of nonplanar porphyrins incorporating bulky components at the beta-pyrrole positions of the porphyrin macrocycle. A new study considers the spectral and electrochemical properties of zinc(II) tetraphenylporphyrins have 0-8 bromo substituents at the beta-pyrrole positions of the macrocycle. Such data provides important information on substituent effects and can be compared to theoretical results.

The electrochemistry of eight nickel porphycenes reveals the substituent dependency of the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) separation of 2.25 V. The substituents are present on the pyrrole beta and/or the ethylenic carbons of the porphycene macrocycle. Moreover, substitutions at the ethylenic carbon have greater effect compared to those at pyrrole beta. The HOMO-LUMO energy gap value lowers as the conjugation of the porphycene ring is extended.

The (TPPBrx)FeCl, where TPPBrx = dianion of beta-brominated-pyrrole tetraphenylporphyrin and x = 0-8, is analyzed by electrochemistry and spectroelectrochemistry in PhCN with tetra-n-butylammonium perchlorate. Each compound exhibits two reversible to quasireversible one-electron oxidations at the conjugated porphyrin pi ring system. The deltaE1/2 between the two electrode reactions increases with the distortion of the molecules. The compounds also undergo three or four reductions, which consist of the electrogeneration of an iron(II), iron(I) and iron(I) pi anion radical.

Spectroscopic studies help characterize (5,10,15-Tri-X-Phenyl-2,3,7,8,12,13,17,18-octamethylcorrolato)cobalt(III) triphenylphosphine complexes (X-substituents), prepared by a new procedure. 1H NMR experiments help determine the activation parameters for interconversion between different atropisomers of o-Cl derivative. Electrochemical studies help analyze the redox characteristics of the complex, and nature of the phenyl ring substituent exerts significant influence on the redox behavior.

Cyclic voltammetric studies of((TpTP)MvL2)(+)Cl(-), where M = P or Sb, L = Cl- or OCH(sub 3)(super -) and TpTP = dianion of tetra-P-tolylporphyrin, help examine the effect of central metal ion and coordinated axial ligands on the redox potentials and stability of electro-reduced products. All species undergo two one-electron reductions and bis(methoxy)porphyrins are more stable than bis(chloro) derivatives. UV-visible and EPR studies help determine the site of electron transfer during electro- reduction.

Cyclic voltammetric studies help examine the redox properties of sigma-bonded metalloporphycenes, (EtioPc)M(C6H5) where M=Fe or In and EtioPc = dianion of 2,7,12,17-tetraethyl-3,6,13, 16-tetramethylporphycene in different mediums. (EtiOPc)Fe(C6H5) undergoes three one-electron oxidations generating an iron(IV) porphycene, an iron(IV)Pi cation radical and a dication respectively. Both sigma-bonded systems exhibit two one-electron reductions at the conjugated Pi ring system. Spectrochemical data and a comparative study with (EtiOPc)FeCl/and (EtioPC)In(C6H5) help assign electron transfer centers for oxidation and reduction of (EtioPc)Fe(C6H5).

An analysis of Fe(III) mu-oxo porphycene dimers reveals that they are stable under nine different cyclic voltammetric time scale-based oxidation states. Thin-cell layer-based reduction yields two stable reduced ((Pc)Fe)2O forms. Spectral data reveal that the dimer reduction occurs at the conjugated pi-ring system.

Spectroelectrochemical and electrochemical methods reduced flurophenyl sigma-bonded iron(III) porphyrins, resulting in OH- and RH. The porphyrins involved in the process are (P)Fe(C6F4H) and (P)Fe(C6F5). The unreduced (P)Fe(R) has an axial flurophenyl ligand that is displaced by OH-, inducing a chain reaction that enables total conversion of the sigma-bonded porphyrin to monomeric (P)FeOH. Substoichiometric quantities of OCH3- or F-, when added to (P)Fe(R), yields identical Fe(III) prophyrin products.

Two new complexes, (eta2-acetylene)- and bis(amine)titanium(II) porphyrin, are synthesized and their properties are determined. The titanium(II) formalism reveals certain characteristics and interaction chemistry that resemble the spectroscopic and magnetic characteristics and the interaction chemistry of the complexes. Powerful ligands that allow the addition of pi contribute to the constancy of the titanium core, which is rich in electrons. The interactions occurring with diazo reagents and phosphine chalcogenides reveal the powerful attenuating ability of titanium(II).

Three one-electron oxidations and a varying number of one-electron attenuations influence cobalt tetraphenylporphyrins which have six, seven or eight Br substituents in beta-pyrrole locations. A reversible complex is formed when the first part of oxidation occurs and another reversible complex participates in the first process of attenuation. Both processes take place under similar situations and predictably happen at potentials which are cathodically moved. Cyclic voltammetric and spectroelectrochemical time scales reveal the stability of both compounds.

The spectral and electrochemical properties of ortho- and meta-substituted zinc(II) porphyrin derivatives reveal a stable pentacoordinate complex for the ortho derivative. The complex features a bound pyridine which cannot undergo a chemical reaction as the porphyrin undergoes electrochemical oxidation. Moreover, a tail-on and tail-off binding mechanism is depicted for the meta derivative, which is controlled by temperature. The meta derivative also yields pyrrole beta-substituted isoporphyrin by further chemical processes during electrochemical oxidation.

The hybrid types of (7,6)- and (6,5)-enriched single walled carbon nanotubes (SWNTs) were utilized to study the photoinduced electron transfer in self-assembled single-walled carbon nanotube (SWNT)/zinc porphyrin (ZnP) hybrids. The rates of charge separation were found to be slightly higher for (7,6)-SWNT-derived hybrids compared to those of the (6,5)-SWNT-derived hybrids.

The article explains synthesis, as well as the characterization of a series of condensed oligopyrazine analogues of acenes, the pyrazinacenes. These compounds are shown to be widely used in the organic thin film transistors.

A supramolecular oligochromophoric system possessing exclusive binding sites for both a guest electron acceptor and an anionic cofactor species is developed to demonstrate the anion-binding-induced stabilization of the charge-separated (CS) state. An increase in reorganizational energy of electron transfer combined with the decrease in charge recombination driving force caused by anion binding resulted in an increase in the lifetime of the CS state.

Self-assembly methods are used for constructing a biomimetic bacterial photosynthetic reaction center complex and examining the photoinduced electron transfer originating in the supramolecular donor-acceptor conjugate. The analysis of the kinetic data in light of the Marcus theory of electron theory has shown that small reorganization energy of the relatively rigid phthalocyanine is responsible for slower charge-recombination process.

The electron donor ability of M[Q.sub.n] (M = Al or Zn for n = 3 or 2) complexes covalently connected to a well-known electron acceptor, fullerene, is studied by functionalizing fullerene with 8-hydroxyquiniline at different ligand positions. The novel features of this class of donor-acceptor conjugates have included faster charge recombination when compared to charge separation and decay of the charge-separated state to populate the low-lying fullerene triplet state in competition with direct charge recombination to the ground state.

Several free-energy calculations are conducted to explain the formation and the properties of the covalently linked free-base corrole-fullerene dyads. These dyads are shown to lead to the formation of several long-lived charge-separated states in the nonpolar solvents.

The crystal structures of many dinuclear complexes of manganese and the decomposition and analysis of the nanostructured products derived from them are described. The dinuclear manganese complexes have decomposed to nanostructured oxide materials, which might be isolated in bulk as lamellar-structured particles or microspheres or deposited on substrates.

Supramolecular nanohybrids composed of single-wall carbon nanotubes (SWNTs) as an electron donor and fullerene as an electron acceptor are constructed. These nanohybrids are used to reduce hexyl-viologen dication and a sacrificial electron donor in an electron-poling experiment.

A new, efficient technique for the introduction of oxygen isotopes into carbohydrates is presented. The synthesis of a series of 17O-enriched mono- and disaccharides demonstrates its general applicability. Oxygen chemical shift data for the glycans have also been derived and recorded at room temperature in acquisition times of less than 10 min. Results indicate that the new method could be useful in probing oligosaccharide conformation at biologically relevant temperatures.

A novel procedure for the preparation of noncovalently linked donor-acceptor complexes via pairing of hydroquinone-quinone species is described. The procedure has been applied in the synthesis of the hydroquinone-appended porphyrin, (5,10,15-triphenyl-20- 2,5-dihydroxyphenyl porphyrinato)zinc(II). The complex was prepared by condensing pyrrole, 2,5-dihydroxybenzaldehyde and benzaldehyde in propionic acid, followed by zinc insertion. The complex was characterized by 1H NMR spectroscopy and electrochemical analysis.

Electrochemical investigations on the beta-substituted-pyrrole tetraphenylporphyrins help analyze the influences of porphyrin ring distortion and inductive effect of the substituted halogen groups on the beta pyrrole positions on redox potentials. Substitution up to 2 halogen groups increases the oxidation potential, beyond which the potential starts decreasing. Ring distortion and the ease of oxidation increase with increase in the number of halogen groups beyond 2.

A nonaqueous medium is used to reveal three reversible one-electron oxidations which influence a Ni(II) porphyrin or porphyrene to form (P)Ni and (OEPc) Ni. A Pi cation radical and dication are produced in a systematic method to coordinate with the primary two oxidations. A Ni(II/III) interaction is observed at half-wave potentials during the third oxidation. The Fe(II) and CO(II) complexes show metal-centered oxidations with TPP, OEPc or ORTPP macrocycles, with half-wave potentials that are compared to the Ni(II) porphyrins.

The simplest dialkylated derivative of C60, (CH3)2C60 (1), is synthesized in a perferential manner. Electrochemical control of the charge, n, on C(sub 60)(super n-), produced before methylation, was used to attain the selectivity. A primarily dimethylated product 1 and free iodide in solution result from the addition of methyl iodide to a solution of C(sub 60)(super 2-), produced by controlled potential bulk electroreduction of C60 in an aprotic solvent.

A series of fluorinated dodecaphenylporphyrins have been synthesized and used as model compounds in studying electronic effects in nonplanar porphyrins. 1H and 19F nuclear magnetic resonance spectroscopy was used in studying the chloroiron(III) complexes of the compounds at 300 and 283 MHz, respectively. Results show that the chloroiron(III) complexes undergo anodic shifts upon fluorination with the first oxidation potential increasing by +720 mV. The site of reduction for the iron complexes depends upon the solvent and if the macrocycle is fluorinated.