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A novel low-band-gap chromophore (5, 0.86 eV) having fluorene as a donor, benzobisihiadiazole (BBTD) as an acceptor, and pyrrole as a π-spacer was successfully designed and synthesized, to probe the effect of π-spacer on the band-gap level of the donor-π-acceptor-π-donor type of chromophores. Compared with the thiophene spacer analogue (in compound 3), the intramolecular hydrogen bonding between the pyrrole and the neighboring BBTD unit pushes the absorption maximum and fluorescence emission of chromophore 5 into the near-infrared spectral region with a red shift of 172 and 158 nm, respectively. The same red-shift phenomenon can also be realized by addition of Lewis acid (e.g., B[F.sub.3]) to the BBTD-containing chromophores with other spacers. Attempt of using low-band-gap chromophore 5 in bulk heterojunction (BHJ) solar cells was made, showing a non-optimized photovoltaic device with the power conversion efficiency of 0.01%. A precursor approach to introduction of the alkaline-labile BBTD acceptor into the polymer backbone has been demonstrated by successful synthesis of low-band-gap polymer P2. The same strategy can be in principle applied to the synthesis of a series of low-band-gap chromophores or polymers with strong acceptors. Key words: donor-π-acceptor-π-donor, chromophore, low band gap, bulk heterojunction (BHJ), precursor polymer. Afin de pouvoir etudier l'effet d'un espaceur π sur le niveau d'energie interbande des chromophores de type donneur-π-accepteur-π-donneur, on a developpe et synthetise un nouveau chromophore de basse energie interbande (5, 0,86 eV) comportant un fluorene comme donneur, un benzobisthiadiazole (BBTD) comme accepteur et un noyau pyrrole comme espaceur π. Par comparaison avec l'analogue comportant un espaceur thiophene (dans le compose 3), la liaison hydrogene intramoleculaire entre le pyrrole et l'unite adjacente BBTD deplace le maximum d'absorption et l'emission de fluorescence du chromophore 5 dans la region spectrale du proche infrarouge avec des deplacements vers le rouge de respectivement 172 et 158 nm. On peut observer le meme phenomene de deplacement vers le rouge par l'addition d'un acide de Lewis (tel le B[F.sub.3]) a des chromophores comportant du BBTD et d'autres espaceurs. On a essaye d'utiliser le chromophore 5 a faible energie interbande dans des cellules solaires a heterojonction globale (HJG); on a obtenu un dispositif non voltaique non optimise ayant une efficacite de conversion de pouvoir de 0,01 %. On a demontre l'applicabilite d'une autre approche a l'introduction de l'accepteur BBTD labile aux produits alcalins dans le squelette d'un polymere en effectuant avec succes la synthese du polymere P2 de faible energie interbande. En theorie, la meme strategie peut etre appliquee a la synthese d'une serie de chromophores ou de polymeres de faible energie interbande avec des accepteurs forts. Mots-cles: donneur-π-accepteur-π-donneur, chromophore, faible energie interbande, heterojonclion globale (HJG), polymere preeurseur., [Traduit par la Redaction] Introduction Research on low-band-gap organic materials (e.g.. chromophores and polymers), whose band-gap levels, defined as the difference between the highest occupied molecular orbital (HOMO) and the [...]

The biodistribution profiles in mice of two pyrrole-imidazole polyamides were determined by PET. Pyrrole-imidazole polyamides are a class of small molecules that can be programmed to bind a broad repertoire of DNA sequences, disrupt transcription factor-DNA interfaces, and modulate gene expression pathways in cell culture experiments. The [sup.18]F-radiolabeled polyamides were prepared by oxime ligation between 4-[[sup.18]F]-fluorobenzaldehyde and a hydroxylamine moiety at the polyamide C terminus. Small animal PET imaging of radiolabeled polyamides administered to mice revealed distinct differences in the biodistribution of a 5-ring [beta]-linked polyamide versus an 8-ring hairpin, which exhibited better overall bioavailability. In vivo imaging of pyrrole-imidazole polyamides by PET is a minimum first step toward the translation of polyamide-based gene regulation from cell culture to small animal studies. biodistribution | fluorine-18 | oxime | radiosynthesis

The photochemical dynamics of the pyrrole-pyridine hydrogen-bonded complex has been investigated with computational methods. In this system, a highly polar charge-transfer state of [sup.1][pi][[pi].sup.*] character drives the proton transfer from pyrrole to pyridine, leading to a conical intersection of [S.sub.1] and [S.sub.0] energy surfaces. A two-sheeted potential-energy surface including 39 in-plane nuclear degrees of freedom has been constructed on the basis of ab initio multiconfiguration electronic-structure data. The non-Born-Oppenheimer nuclear dynamics has been treated with time-dependent quantum wave-packet methods, including the two or three most relevant nuclear degrees of freedom. The effect of the numerous weakly coupled vibrational modes has been taken into account with reduced-density-matrix methods (multilevel Redfield theory). The results provide insight into the mechanisms of excited-state deactivation of hydrogen-bonded aromatic systems via the electron-driven proton-transfer process. This process is believed to be of relevance for the ultrafast excited-state deactivation of DNA base pairs and may contribute to the photostability of the molecular encoding of the genetic information. conical intersection | excited-state hydrogen transfer | nonadiabatic transition

Three new methods are described for preparing 2-substituted 3-furfurals starting from 3-furfural, 3-bromofuran and 3-vinylfurans. 3-Furyl imines have undergone the addition of organometallic reagents to provide furyl sulfonamides and 2-substituted 3-formyl pyrroles are formed under the oxidative rearrangement conditions.

An efficient synthesis of porphobilinogen by employing Mukaiyama aldol reaction between the regioselectively formed silyl enol ether and the acetal of methyl 5-azidolevulinate is reported.

The geometrical structure, stability, the basis set effects, and the linear and nonlinear optical properties of neutral pie-conjugated [C.sub.4][H.sub.4]N. are determined. Conjugation and stability of the neutral [C.sub.4][H.sub.4]N. reduced after a rise in the spin multiplicity.

We present a new strategy for the label-free electrochemical detection of DNA hybridization for detecting hepatitis C virus based on electrostatic modulation of the ion-exchange kinetics of a polypyrrole film deposited at microelectrodes. Synthetic single-stranded 18-mer HCV genotype-l-specific probe DNA has been immobilized at a 2,5-bis(2-thienyl)-N-(3-phosphoryl-n-alkyl)pyrrole film established by electropolymerization at the previously formed polypyrrole layer. HCV DNA sequences (244-mer) resulting from the reverse transcriptase-linked polymerase chain reaction amplification of the original viral RNA were monitored by affecting the ion-exchange properties of the polypyrrole film. The performance of this miniaturized DNA sensor system was studied in respect to selectivity, sensitivity, and reproducibility. The limit of detection was determined at 1.82 x [10.sup.-21] mol [L.sup.-1]. Control experiments were performed with cDNA from HCV genotypes 2a/c, 2b, and 3 and did not show any unspecific binding. Additionally, the influence of the spacer length of 2,5-bis(2-thienyl)-N-(3-phosphoryl-n-alkyl)pyrrole on the behavior of the DNA sensor was investigated. This biosensing scheme was finally extended to the electrochemical detection of DNA at submicrometer-sized DNA biosensors integrated into bifunctional atomic force scanning electrochemical microscopy probes. The 18-mer DNA target was again monitored by following the ion-exchange properties of the polypyrrole film. Control experiments were performed with 12-base pair mismatched sequences.

The investigation of the [Co.sub.2][(CO).sub.8]-catalyzed aza-Pauson-Khand-type reaction (PKTR) of alkynecardiimides and its application to the total synthesis of many hexahydropyrrolo[2,3-b]indole alkaloids are presented. A simple procedure is developed for preparing pyrrolo[2,3-b]indol-2-ones based on the [Co.sub.2][(CO).sub.8]-catalyzed aza-PKTR of alkynecardiimides and their conversion to the corresponding hexahydropyrrolo[2,3-b]indoleindoles alkaloids.

The syntheses of many bis-cations with a simple primary ammonium cation attached via flexible linkers of varying length to a guanidiniocarbonyl pyrrole oxo anion binding site are described. The formation of the complex between bis-cation and N-acetyl phenyl alanine carboxylate is examined by fluorescence titrations and molecular mechanics.

N-acyl 3,4-disubstituted pyrroles are synthesized directly from hydrazine and an aldehyde via a Piloty-Robinson pyrrole synthesis. The free N-H pyrroles are accessed after the Piloty-Robinson reaction and they are used in the synthesis of octaethylprophyrin and octaethyltetraphenylporphyrin.

A study was conducted to systematically examine the mechanism of the solvent polarity dependence of the fluorescence ON/OFF threshold of the BODIPY (boron dipyrromethene) fluorophore and the role of photoinduced electron transfer (PeT). The findings revealed that polarity at the surface of albumin was found to be similar to that of acetone while the polarity of the internal membranes of HeLa cells was similar to that of dichloromethane.

The sequence-specific DNA alkylation by conjugates with an indole linker is examined in the absence or presence of partner Py-Im polyamine. The results have shown that alkylation has proceeded through heterodimer formations, indicating that this is a general way to expand the recognition sequence for DNA alkylation by N-methylpyrrole (Py)-N-methylimidazole (Im) polyamides and 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CBI) conjugates.

The enantiomerically pure bis-bidentate ligands of bis(pyrrol-2-ylmethyleneamine)cyclohexane are prepared from condensation of the pure R,R and S,S enantiomers of the 1,2-diaminecyclohexane spacer with 2 equiv of pyrrole-2-carbaldehyde. The analysis of circular dichroism (CD) spectra has revealed both intraligand and interligand chromophore couplings.

The synthesis of three new amido-imine-type hybrid macrocycles based on substituted pyrrole units showed them to act as effective receptors for oxoanions in the solid state and in acetonitrile solution. The acetonitrile solution using standard UV-vis spectroscopic titration methods indicated that the three new receptors display high affinities toward oxoanions with maximal association constants being on the order of [10.sup.7] [M.sup.-1].

Several pyrrolic and hydrogen-bonding ligands are incorporated into a benzene-based tripodal scaffold for the generation of a new series of receptors, which can be widely used for the molecular recognition of carbohydrates and monosaccharides. The study of the various geometric, functional and coordinative complementarity between the bonding groups and hydroxyls helps in analyzing the affinity of such products through a generalized binding receptor.

The synthesis and anion binding properties of B[F.sub.2] complexes of [beta]-tetraethyl-substituted Ketonesare described with and without electron-withdrawing ethoxycarbonyl moieties at pyrrole [alpha]-positions. The substituents at pyrrole rings of these acyclic anion receptors have played a main role in controlling not only the polarization of binding sites (NH and CH) but also the relative stabilities of the preorganized conformations and the degrees of sterical repulsion.

The synthesis and anion binding properties of B[F.sub.2] complexes of [beta]-tetraethyl-substituted dipyrrolyldiketones are described with and without electron-withdrawing ethoxycarbonyl moieties at pyrrole [alpha]-positions. The substituents at pyrrole rings of these acyclic anion receptors have played a main role in controlling not only the polarization of binding sites (NH and CH) but also the relative stabilities of the preorganized conformations and the degrees of sterical repulsion.

An efficient total synthesis of antibiotic (-)-codonopsinine is achieved from D-alanine as a chiral template. The vital steps of the method are modified Sharpless asymmetric dihydroxylation reaction and the highly stereoselective intramolecular acid-catalyzed amidocyclization.

Indazolium-3-amidates have undergone [3+2]-cycloadditions with activated triple bonds to spiro[indazole-3,3'-pyrroles]. Heternuclear single quantum coherence (HSQC), heteronuclear multiple bond correlation (HMBC), nuclear Overhauser enhancement spectroscopy (NOESY) and [super 1]H/[super 15]N correlations are used to examined the structures of the cycloadducts.

A general synthetic method fro pyrroquinolizidines (3,4,5,5a,6,7,8-heptahydropyrrolo[2,1,5-de]-quinozilines) by munchnone 1,3-dipolar cycloaddition is described. This method was used in the synthesis of an unnatural pyrroloqunilizidine homologue of myrmicarin 215B.

A new method for synthesis of N-protected staurosporinones is described. These staurosporinones are useful for the synthesis of indolo[2,3-a]pyrrolo[3,4-c]carbazole alkaloids and related compounds.

Broadband dielectric measurements of poly(vinyl pyrrolidone) (PVP)-monohydroxyl alcohol mixtures of various normal alcohols are made in the frequency range of 20 Hz to 20 GHz at 25 degree Celsius. The results have shown that the relaxation time of the local chain motion of PVP increases with PVP concentration and solvent viscosity.

The synthesis of several [pi]-electron-donating monopyrrolotetrathiafulvalene (MPTTF) derivatives which are conceptually divided into three classes containing none, one, or two triethylene glycol (TEG) substituents, is reported. The results have revealed that the strength of the binding between MPTTF derivatives and [CBPQT.sup.4+] is directly correlated to the [pi]-electron donating properties of the MPTTF derivatives.

The nucleophilic addition of sodium azide to 1,2-allenyl esters has produced vinyl azides with very good regio- and stereoselectivities. A new method is developed for the synthesis of pyrroles from 1-allylic allenyl esters through a series of consecutive transformations.

The 2-trimethylsilylethanesulfonyl (SES) protecting group is compared to the tosyl (Ts) group while preparing a nitrogen-containing five-membered ring obtained by the aza-Baylis-Hillman/alkylation/RCM route. The SES-protected pyrrolines are hydrogenated to yield pyrrolidines with an excellent diastereoselectivity and free amine pyrrolidines are obtained by HF-mediated deprotection of the SES group.

An efficient copper-catalyzed double alkenylation of amides with (1Z,3Z)-1,4-diiodo-1,3-dienes is described. The reactions have produced di- or trisubstituted N-acylpyrroles in excellent yields by using Cul as the catalyst, [Cs.sub.2]C[O.sub.3] as the base and rac-trans-N,N'-dimethyl-cyclohexane-1,2-diamine as the ligand.

A phosphine-free palladium-catalyzed method is described for direct C-arylation of free (N-H)-indoles and pyrroles with iodo- and bromoarene donors. This procedure has provided a rapid entry to a wide range of C-arylated (N-H)-indoles including derivatives of tryptamine.

A new pyrrole-based tetraphosphorus ligand, capable of forming multiple chelating modes, is prepared and applied in the regioselective isomerization-hydroformylation of internal olefins. Results of the experiment clearly indicate that tetraphosphorus ligand has an enhanced ability to coordinate to metal and thus afforded better regioselectivity in isomerization-hydroformylation compared with the corresponding bisphosphorus ligand.

The fast intramolecular charge transfer (ICT) accompanied by dual fluorescence from a locally excited (LE) and an ICT state-taking place with N-phenylpyrrole (PP) in the solvent n-propyl cyanide (PrCN) is investigated. The results have shown that the ICT reaction of PP in the investigated alkyl cyanides has a late transition state with a charge distribution similar to that of the ICT state.

The sensor platform of zinpyr 4 (ZP4) through pyrrole-for-pyridyl substitution is modified and the effects of this variation on both photophysical and metal-binding properties are evaluated. The utility of aniline-based ZP probes for select biological imaging applications are investigated.

The studies, relating to the straightforward electrosynthesis of novel polycarboxylated conducting polyCbz-films from one carboxylated Cbz-containing building block as new electro-oxidizabel peripheral species, are reported. The postpolymerization covalent grafting of biomolecules onto these fabricated conducting surfaces should pave the way for the development of numerous applications in the biosensing field.

A study shows that the reaction of alkene-tethered [alpha]-ketocarboxylic acid derivative with monosubstituted hydrazines allows highly substituted cis-cyclopentapyrazolidine ring system to be constructed rapidly. These cyclocondensations can be realized optimally either under thermal conditions or in the presence of protic acids or Lewis acids.

The acidity constants p[K.sub.a] of 11 bases (amines, anilines, pyridines, pyrrolidines, and iminophosphoranes) is determined in tetrahydrofuran by potentiometry, complemented by conductometric measurements. A scale of absolute acidity in tetrahydrofuran is established from the p[K.sub.a] values obtained, which has allowed calculation of the absolute p[K.sub.a] values of 77 bases from literature relative p[K.sub.a] data.

The mechanisms of the photochemical isomerization reactions are investigated by using a model of 2-cyanopyrrole and 2-cyano-5-methylpyrrole with CASSCF and MP2-CAS methods and the 6-31 1(d,p) basis set. The analysis has shown that the conical intersections play a crucial role in the photoisomerization reactions of cyanopyrroles.

A new and efficient enantioselective synthesis of N-alkyl-3-pyrrolines wherein N-Boc deprotection and [AgNo.sub.3]-promoted cyclization take place between the enantioenriched propargyl mesylates or perfluorobenzoates and the alpha alkylcuprates, is presented. This method is amenable for the synthesis of a wide variety of racemic 3-pyrrolines, which are synthetically and biologically very useful and also serve as inhibitors of a very important compound, namely monoamine oxidase. (MAO).

The reaction of azomethine ylides (AMY) with alkenes is presented as a powerful method for the syntheses of substituted and stereoisomerically pure pyrrolidines. The synthesis of highly substituted pyrrolidines ins in optically pure form via asymmetric [3+2]-cycloaddition of azomethine ylides, which allows simultaneous construction of up to four stereocenters is increasingly becoming an important strategy, in view of their forming integral part of numerous biologically active alkaloids and pharmaceuticals.

This paper describes a novel technique to produce polypyrrole-based nanoelectrodes for electrochemical detection purpose. The fabrication process relies on the creation of patterned nanotemplates i.e., nanometric gold spots surrounded by an electrically insulating material (Si[O.sub.x]). From these templates, polypyrrole nanopillars are grown by classical electrochemical methods. Atomic force microscopy demonstrates that polypyrrole grows selectively inside the gold nanotemplates. The electrochemical characterization by cyclic voltammetry showed a sigmoidal-shaped voltammogram characterizing the typical nanoelectrode array behavior.

The preparation of the Beta-fluorinated derivative of the 1,3-dipyrrolyl-1,3-propanedione B[F.sub.2] complex from 3,4-difluoropyrrole and malonyl chloride, followed by treatment with B[F.sub.3].O[Et.sub.2] is presented. Results show that, despite the simple, acyclic, and neutral structure, the Beta-fluorinated derivative exhibits efficient 1:1 binding for anions in C[H.sub.2][Cl.sub.2] using the bridging CH and pyrrole NH as interaction sites.

As an alternative to the usual commercial reference and quasi-reference electrodes (QREs), we propose metal (Pt, stainless steel) coated with partially oxidized polypyrrole as a QRE. The electrode is easily fabricated by cyclic voltammetry (CV) with the metal electrode in an acetonitrile or C[H.sub.2][Cl.sub.2] solution of 10 mM pyrrole containing 0.1 M [Bu.sub.4]NP[F.sub.6]. These QREs were more stable than the widely used metal (e.g., Ag, Pt) wire QRE as demonstrated by testing in several aqueous and organic media, with the stability checked by CV with ferrocenemethanol as the redox species. The results obtained demonstrate good stability of these QREs over a period of 1 day and relatively reproducible potential in a given solvent and supporting electrolyte. This electrode has the advantage that it does not contaminate the test solution with ions or solvent from a usual liquid electrolyte (e.g., the KCl in an Ag/AgCl). It is also simple to fabricate very small electrodes for use in nanocells, e.g., in scanning tunneling and electrochemical microscopy.

The interaction of calixpyrrole with several chloride salts is analyzed in the solid state by X-ray crystallography as well as in solution by isothermal titration calorimetry (ITC) and [.sup.1.H] NMR spectroscopic titrations. A strong dependence is observed on the countercation in the case of dichloromethane, where the affinity constants for the interaction with chloride were ranging from [10.sup.2]-[10.sup.4] [M.sup.-1].

The synthesis, DNA alkylating activity and antitumor activity of pyrrole (Py)-imidazole (Im) hairpin polyamide 1-(chloromethyl)-5-hydroxy-1,2-dihydro-3H-benz[e]indole (seco-CB) conjugates, which contain indole linkers and target C-rich and G-rich strands in double-strand telomere repeat sequences are reported. The analysis has shown that the conjugates have potential as antitumor drugs capable of targeting telomere repeat sequence.

Dynamic resolution is studied as a method for asymmetric synthesis of 2-substituted pyrrolidines and the influence of a wide selection of different ligands and extension from N-alkyl to N-allylic derivatives that is cleaved and provides a method to access the N-unsubstituted pyrrolidine products is reported. The resolution of N-(2,3-dimethylbut-enyl)-2-lithiopyrrolidne happens by a dynamic thermodynamic resolution and the products can be converted easily to N-unsubstituted derivatives.

The operation mechanism of dipyridyldiketopyrrolopyrrole (DPPP)-based [H.sub.2] sensor is investigated in order to understand the electric-field-assisted dissociation of [H.sub.2] in the presence of Pd or Pt, as well as the carrier generation and carrier determination. The electron conduction is confirmed by the Seebeck effect and the doping is characterized by an instantaneous one, since the doping depends on the ambient [H.sub.2] concentration.

Fabry-Perot fringes are observed in the absorption spectra of hydrogen-bonded layer-by-layer (LBL) films of poly(vinyl pyrrolidone) (PVPON) and ploy(acrylic acid) (PAA), which are obtained from the interferences between beams transmitted and partially reflected at the highly smooth film-air interface and film-quartz interface. The PVPON/PAA films are eroded by long-term annealing in water or diluted HCl by monitoring the movement of the Fabry-Perot fringes and the erosion rate is found to decrease with a decrease in the pH of the media and an increase in the molecular weight of the polymers.

Pyrrole-imidazole (Py-Im) polyamides containing stereospecifically [alpha]-amino- or [alpha]-hydroxyl-substituted [gamma]-aminobutyric acid as a 5-TG-3 recognition element are synthesized by machine-assisted Fmoc solid-phase synthesis. Surface plasmon resonance (SPR) assays and molecular modeling studies collectively suggest that the (S)-[alpha]-hydroxyl-[gamma]-aminobutyric acid [gammaSO] may act as a 5-TG-3 recognition unit.

Several newly synthesized inhibitors of a reaction intermediate of porphobilinogen synthase (PBGS) are used to study its structural and kinetic properties, which helps in the analysis of the active site and catalytic mechanism of Pseudomonas aeruginosa (Pa)PBGS. The analysis provides an insight in the direct involvement of magnesium ions in the binding of PBGSs, though the succession of chemical transformations involved in the enzyme-catalyzed mechanism is not yet clear.

Five Glu 192 mutants of PCP-0SH (where PSCP= pyrrolidone carboxyl peptidases) from Pyrococcus furiosus were constructed and their thermal and pH-induced unfolding and crystals structures were compared in order to explain the role of the buried glutamic acid in stabilizing pyrrolidone carboxyl peptidases (PCP) from hyperthermophiles. The results showed that completely buried Glu 192 contributes to the stabilization of PCP-0SH because of the formation of strong intramolecular hydrogen bonds and these hydrogen bonds contribute more to the conformational stability of proteins.

The intramolecular aminomercuration reaction of sugar-derived beta-hydroxy-gama-alkenylamines has to undergo 5-endo-trig cyclization in high yield. The sugar-substituted pyrrolidines obtained are elaborated to the synthesis of polyhydroxylated indolizidine alkaloids having promising glycoside inhibitory activities.