Pyrrolyl Group Research Articles

Synthesis, Structure, Spectral, Electrochemical, and Theoretical Studies of Ru(II) Complexes of 3-Pyrrolyl BODIPY-Based Ligands.

3-Pyrrolyl BODIPY having an appended pyrrolyl group at the 3-position of BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) and its functionalized derivatives have been used as ligands to prepare one example of Ru(II) complex of pyrrolyl dipyrrin and three unique examples of bichromophoric BODIPY-Ru(II) complexes in good yields. The complexes were characterized by HR-MS, 1D and 2D NMR, X-ray analysis for two complexes, absorption, cyclic voltammetry, and DFT/TD-DFT techniques. The X-ray structure of the Ru(II) complex of pyrrolyl dipyrrin revealed that the geometry around the Ru(II) ion was pseudo-octahedral with an arene unit occupying three coordination sites in η6-fashion and two nitrogen atoms of the dipyrrin ring and one chloro group adopting the "three legs piano-stool" structure. The X-ray structure of the bichromophoric BODIPY-Ru(II) complex revealed that the BODIPY core was planar and the central B(III) was coordinated with two pyrrole nitrogens of the dipyrrin unit and two axial fluoride ions in a tetrahedral geometry, and Ru(II) was bonded to appended pyrrole "N" and "N" of benzimidazole substituent present at the α-position of appended pyrrole, one chloro group, and one arene ring in a pseudo-octahedral geometry. The spectral studies revealed that the electronic properties of the BODIPY unit in BODIPY-Ru(II) complexes were significantly altered, and electrochemical studies indicated that the BODIPY-Ru(II) complexes exhibit one oxidation corresponding to Ru(II) to Ru(III) and one reduction corresponding to the BODIPY unit. The DFT/TD-DFT studies corroborated the experimental observations.

In silico screening of ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate and some of its derivatives for their NLO activities using DFT.

The nonlinear optical (NLO) properties of ethyl 4-[(E)-(2-hydroxy-4-methoxyphenyl)methyleneamino]benzoate (EMAB) and some of its derivatives are investigated herein using the density functional theory (DFT) and time-dependent (TD)-DFT methods. The density functionals B3LYP, CAM-B3LYP, M06-2X and ωB97XD, and basis sets 6-31 + G**, 6-311 + + G** and Def2-TZVPP have been used. From the results, EMAB and its substituted derivatives studied are promising candidates for NLO materials. In all cases, the static first and second hyperpolarizabilities (31.7-86.5 × 10-30 and 84.4-273 × 10-36 electrostatic units (esu), respectively) and the frequency-dependent NLO properties are found to be significantly larger (about 43-103 and 28-76 times greater) than those of the NLO prototypical molecule, para-nitroaniline. Furthermore, the maximum absorption wavelengths of the molecules fall within the UV region of the electromagnetic spectrum. Relative to EMAB, the derivatives have shown improved transparency-nonlinearity trade-offs. Natural bond orbital (NBO) and density of states (DOS) analyses herein revealed effective charge transfer within the molecules studied, especially those with stronger electron donors than that in EMAB (methoxy group). Among the molecules studied, the derivative obtained by substituting EMAB's methoxy group with the pyrrolyl group was found to exhibit the best NLO properties. Conclusively, the NLO activities of EMAB can be significantly improved through the substitution of its methoxy group with stronger electron donors.

Enhancing the Photoelectric Properties of Zinc Porphyrin Dyes by Introducing Five-Membered Heterocyclic Rings into the Electron Donor: A Density Functional Theory and Time-Dependent Density Functional Theory Study.

To fabricate highly efficient dye sensitizers for dye-sensitized solar cells, new zinc porphyrin dye sensitizers were designed based on one of the most efficient dyes, YD2-o-C8, by introducing electron-rich heterocyclic rings into the electron donor. Five potentially efficient dyes, Dye1–5, were obtained by replacing the phenyl group of the donor in YD2-o-C8 with pyrrolyl, furyl, and thienyl groups. The electronic structures, absorption spectra, intramolecular charge-transfer characteristics, and excited-state lifetimes of the designed dyes were investigated using the density functional theory and time-dependent density functional theory methods. All the designed dyes exhibit better photoelectric properties than those of YD2-o-C8. Compared with YD2-o-C8, the designed new dyes have smaller frontier molecular orbital energy gaps and obvious red-shifting absorption spectra in the Q band. The analyses of charge density difference plots and intramolecular charge-transfer characteristics indicated that the designed dyes can better promote intramolecular charge transfer and electron–hole separation. Among the five designed dyes, Dye1 with a pyrrolyl group exhibits the best performance. Dye3 and Dye5 with methyl-furyl and methyl-thienyl groups, respectively, exhibit the next best performance. Dye2 and Dye4 with furyl and thienyl groups, respectively, are the worst performers. The introduced methyl group can further improve the electron-donating ability of heterocyclic rings and promote the red shift of the Q bands and intramolecular charge transfer of dyes. The excited-state lifetimes of the new dyes were in the following order: YD2-o-C8 < Dye4 < Dye2 < Dye5 < Dye3 < Dye1, which shows their stronger abilities to inject electrons into semiconductor films.

Exploring Phosphine Electronic Effects on Molybdenum Complexes: A Combined Photoelectron Spectroscopy and Energy Decomposition Analysis Study.

In organometallic chemistry, especially in the catalysis area, accessing the finest tuning of a catalytic reaction pathway requires a detailed knowledge of the steric and electronic influences of the ligands bound to the metal center. Usually, the M-L bond between a ligand and metal is depicted by the Dewar-Chatt-Duncanson model involving two opposite interactions, σ-donor and π-acceptor effects of the ligand. The experimental evaluation of these effects is essential and complementary to in-depth theoretical approaches that are able to provide a detailed description of the M-L bond. In this work, we present a study of LMo(CO)5 complexes with L being various tertiary phosphine ligands by means of mass-selected high-resolution photoelectron spectroscopy (PES) performed with synchrotron radiation, DFT, and energy decomposition analyses (EDA) combined with the natural orbitals for chemical valence (NOCV) analysis. These methods enable a separated access of the σ-donor and π-acceptor effects of ligands by probing either the electronic configuration of the complex (PES) or the interaction of the ligand with the metal (EDA). Three series of PR3 ligands with various electronic influences are investigated: the strong donating alkyl substituents (PMe3, PEt3, and PiPr3), the intermediate PPhxMe(3-x) (x = 0-3) set, and the PPhxPyrl(3-x) set (x = 0-3 with Pyrl being the strong electron withdrawing pyrrolyl group C4H4N). For each complex, their adiabatic and vertical ionization energies (IEs) could be determined with a 0.03 eV precision. Experiment and theory show an excellent agreement, either for the IE determination or electronic effect analysis. The ability to interpret the spectra is shown to depend on the character of the ligand. "Innocent" ligands provide the spectra that are the most straightforward to analyze, whereas the "non-innocent" ligands (which are ionized prior to the metal center) render the analysis more difficult due to an increased number of molecular orbitals in the energy range considered. A very good linear correlation is finally found between the measured adiabatic ionization energies and the interaction energy term obtained by EDA for each of these two types of ligands, which opens interesting perspective for the prediction of ligand characters.

Structure-based design of 2,4-diaminopyrimidine derivatives bearing a pyrrolyl group as ALK and ROS1 inhibitors

Twenty-eight 2,4-diaminopyrimidine derivatives (9a–9n and 10a–10n) bearing a pyrrolyl moiety were designed and synthesized based on the co-crystal structure of ceritinib with ALKwt protein and compound 10d bearing sulfonamide (R1) and 4-methylpiperazinyl (R2) moiety was of great promising.

Biosynthesis of coral settlement cue tetrabromopyrrole in marine bacteria by a uniquely adapted brominase–thioesterase enzyme pair

Halogenated pyrroles (halopyrroles) are common chemical moieties found in bioactive bacterial natural products. The halopyrrole moieties of mono- and dihalopyrrole-containing compounds arise from a conserved mechanism in which a proline-derived pyrrolyl group bound to a carrier protein is first halogenated and then elaborated by peptidic or polyketide extensions. This paradigm is broken during the marine pseudoalteromonad bacterial biosynthesis of the coral larval settlement cue tetrabromopyrrole (1), which arises from the substitution of the proline-derived carboxylate by a bromine atom. To understand the molecular basis for decarboxylative bromination in the biosynthesis of 1, we sequenced two Pseudoalteromonas genomes and identified a conserved four-gene locus encoding the enzymes involved in its complete biosynthesis. Through total in vitro reconstitution of the biosynthesis of 1 using purified enzymes and biochemical interrogation of individual biochemical steps, we show that all four bromine atoms in 1 are installed by the action of a single flavin-dependent halogenase: Bmp2. Tetrabromination of the pyrrole induces a thioesterase-mediated offloading reaction from the carrier protein and activates the biosynthetic intermediate for decarboxylation. Insights into the tetrabrominating activity of Bmp2 were obtained from the high-resolution crystal structure of the halogenase contrasted against structurally homologous halogenase Mpy16 that forms only a dihalogenated pyrrole in marinopyrrole biosynthesis. Structure-guided mutagenesis of the proposed substrate-binding pocket of Bmp2 led to a reduction in the degree of halogenation catalyzed. Our study provides a biogenetic basis for the biosynthesis of 1 and sets a firm foundation for querying the biosynthetic potential for the production of 1 in marine (meta)genomes.

Adsorption of Pyrrole on the Si(111)-7×7 Surface: Effect of Substrate Temperature

Adsorption of pyrrole on the Si(111)-7×7 surface was investigated using scanning tunneling microscopy (STM). Template-induced molecular corral structure was observed at room temperature though the N-H bond cleavage. At the substrate temperature of 130 °C, the pyrrolyl adsorbates were observed by STM with reserving the 7×7 substrate. However, the self-assembly of the molecular corral structure was disarranged at 130 °C. Then, pyrrolyl group was decomposed or desorbed from the surface at the substrate temperature of 200 °C. The defect-induced attachment of pyrrole was also observed.

Photochemistry and DNA-affinity of some stilbene and distyrylbenzene analogues containing pyridinium and imidazolium iodides

The relaxation properties of the excited states of some trans-1,2-diarylethene analogues (where one aryl group is a methylpyridinium or dimethylimidazolinium group and the other one is a π-excessive furyl or pyrrolyl group) and two all-trans-distyrylbenzene analogues (where the central ring is a methylpyridinium group and the side rings are furyl or methylpyrrolyl groups) have been investigated in buffered (pH 7) aqueous solutions. The compounds of the diarylethene series generally undergo efficient trans → cis photoisomerization while the yield of the radiative deactivation is very small at room temperature. The corresponding distyrylbenzenes display small yields of radiative/reactive pathways and mainly deactivate by internal conversion. The solvent effect on the spectral behaviour indicates the occurring of intramolecular charge transfer (“push–pull” compounds) which can induce interesting non-linear optical properties. Some experiments on the interactions with DNA, which might affect the cell metabolism, showed a modest binding affinity for the compounds with one ethenic bond and two aromatic rings. The complexation constant increases substantially in compounds with two ethenic bonds (three aromatic rings) and in the halogen-substituted compounds. The formation of ligand–DNA complexes affects only slightly the competition of the radiative/reactive relaxation from the lowest excited singlet state.

ChemInform Abstract: Formation and Reactivity of 1-Pyrrolyl-2,2,2-trifluoroethyl Cations.

1-(1-Methyl-2-pyrrolyl)-2,2,2-trifluoroethyl p-nitrobenzoate (3) reacts by carbocation formation with an m value for the dependence of rate on the solvent polarity parameter YOTs of 0.56, and a rate 41 times slower than (1-methyl-2-pyrrolyl)methyl p-nitrobenzoate. The products from 3 include significant amounts of material derived from solvent attack at the 5-position of the pyrrole ring. The results indicate a high degree of charge delocalization by the strongly donating pyrrolyl group, resulting in a low k(H)/k(CF3) rate ratio and nucleophilic attack on the ring. 1,1, l-Trifluoro-2-(1-methyl-2-pyrrolyl)propan-2-ol (10) reacted with CF3CO2H via a tertiary carbocation, which led to dimeric products resulting from electrophilic substitution on the pyrrole ring. Keywords: pyrrole, trifluoromethyl substituents, carbocations.

Highly Regioselective and Active Rh–2,2′-Bis(dipyrrolylphosphinooxy)-1,1′-(±)-binaphthyl Catalyst for Hydroformylation of 2-Octene

Abstract Rhodium catalyst bearing 2,2′-bis(dipyrrolyphosphinooxy)-1,1′-(±)-binaphthyl (ligand 1) shows high regioselectivity and activity for the hydroformylation of 2-octene. The introduction of a pyrrolyl group in the ligand greatly improves the yield of the linear aldehyde. The regioselectivity is up to 97.5% under mild conditions (100 °C, 0.7 MPa H2/CO).

Synthesis of Methanes Having Four Different Carbon Substituents Utilizing Indium‐Catalyzed Cleavage of Carbon–Pyrrolyl Bonds

AbstractA pyrrolyl group bound to an sp3 carbon atom in gem‐dipyrrolylalkanes was found to be successfully replaced by a certain range of carbon nucleophiles in the presence of an indium catalyst. The reaction can also be performed efficiently as a three‐component assembly of alkynes, pyrroles, and carbon nucleophiles in one batch. The strategy is highly useful to synthesize methanes having four different carbon substituents. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2009)

ピロール系化学吸着単分子膜を介したポリピロール薄膜による銅イオンの固定

A technique of immobilizing copper ions through a polypyrrole thin film that is covalently bonded to a substrate surface through a chemically adsorbed monolayer containing pyrrolyl group (PNN-CAM) was studied. Contact angle, Fourier transform infrared (FT-IR), UV-visible, and film thickness measurements were done to characterize the PNN-CAM and the polypyrrole thin film. The water contact angles on the slide glass changed from 4.5° to 67.0° by preparing the PNN-CAM. In the FT-IR spectrum for the slide glass covered with the PNN-CAM, strong bands attributable to the νasCH2 vibrations and νsCH2 appeared respectively at 2925 cm−1 and 2850 cm−1. These results indicate that PNN-CAM was prepared on the slide glass. In the subtracted UV-visible spectra before and after oxidative polymerization, a strong absorption band appearing at approximately 230 nm was assigned to the conjugated bonds of the polypyrrole groups. The result indicates that a polypyrrole thin film was prepared on the PNN-CAM. Measurements of the PNN-CAM and polypyrrole thin film using an automatic ellipsometer showed the respective thicknesses to be ca. 1.7 nm and ca. 2.1 nm. X-ray photoelectron spectroscopy (XPS) was also applied to confirm the immobilization of copper ions on the silicon substrate. Cu(2p) peak was observed from the silicon substrate covered with polypyrrole thin film after ultrasonic cleaning and wiping with wet cotton cloth. The result demonstrates the formation of the complex between the copper ions and the nitrogen atoms of the pyrrolyl groups.

Synthesis and Electrochemical Properties of Poly(vinyl carboxy ethyl ether)-g-poly(pyrrole) Copolymer

A novel conducting graft copolymer (PVCEE-g-PPy) of poly(vinyl carboxy ethyl ether) (PVCEE) and polypyrrole (PPy) was prepared by electrochemical polymerization of pyrrole using a precursor, poly(vinyl pyrrolyl propanone ether) (PVPPE). For synthesis of the graft copolymer, PVCEE was first synthesized by reacting poly(vinyl alcohol) with 3-chloro propionic acid. The precursor PVPPE for PVCEE-g-PPy was then synthesized from PVCEE. The chemical structures of PVCEE and PVPPE were confirmed by FT-IR spectroscopy and 1H-NMR. Electrochemical properties of the novel conducting graft copolymer were compared with those of the PVCEE/PPy composite using cyclic voltammetry (CV) and chronoamperometry (CA). It was confirmed that the pyrrolyl group of the precursor polymer can act as the nuclei for the graft polymerization of pyrrole into PVPPE.

Novel Modified Pyrrole Monomers, 1: Synthesis and Characterization

Different 1-substituted-(pyrrole alkyl)phosphonic acid derivatives have been designed as adhesion promoters to graft polypyrrole layers on several substrates. These compounds contain two reactive, terminal moieties: the phosphonic acid group as anchor to the oxide surface and the pyrrolyl group, which functions as starting unit for surface polymerisation. Both groups are connected by an alkyl spacer ranging from 4 to 12 methylene units. The short- and long-chain derivatives were synthesized for the first time to study their self-assembling properties and their effectiveness to be used as an adhesion promoter for grafting covalently bound polypyrrole layers on oxide substrates. Surfactant-like properties of the long chain derivatives and their behaviour in water for pyrrole polymerization were also investigated, as will be discussed in future papers. In this first paper of the series, the synthesis and characterization of the monomers are presented. The structure of the molecules was proven by 1H-NMR, 31P-NMR and FT-IR spectroscopy. Thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) revealed that the stability of the compound depended on their chain length: the longer the alkyl chain, the more stable the monomer. On the other hand, reactivity decreased with increasing chain length, as proven by cyclic voltammetry measurements (CV).

Application of a Chemically Adsorbed Monolayer and Polypyrrole Thin Film for Increasing the Adhesion Force between the Resin Substrate and the Plated Copper Layer

AbstractA chemically adsorbed monolayer containing pyrrolyl group (Pyrrolyl-CAM) was prepared between a plated copper layer and a resin substrate for increasing the adhesion force without roughening a surface of the resin substrate. Although it was not enough to increase the adhesion force between the resin substrate and the copper layer by using only Pyrrolyl-CAM, the sufficient adhesion force was obtained by preparing a polypyrrole thin film between Pyrrolyl-CAM and the copper layer.Pyrrolyl-CAM and the polypyrrole thin film on the substrate were evaluated by an automat-ic contact angle meter and auger electron spectroscopy in order to analyze the condition of the films between the resin substrate and the copper layer.The peel strength test was carried out in order to evaluate the adhesion force. The best ad-hesion force was 0.98 [N/mm], and the target value of 0.60 [N/mm] was sufficiently achieved.

金属スルホナート触媒による不飽和炭化水素および複素芳香族化合物の活性化を利用した炭素‐炭素結合形成反応に関する研究

Lewis acids have been used as a mediator or a catalyst so far mainly for activation of heteroatom-containing compounds like carbonyl compounds, imines and alkyl halides. In contrast, we have been focusing on developing new carbon-carbon bond forming reactions utilizing activation of hydrocarbons by a metal sulfonate catalyst. In this context, we found that arenes as well as heterocyclic arenes add to alkynes in the presence of indium triflate [In (OTf)3, Tf=SO2CF3] as a catalyst. These findings are followed by development of facile synthesis of aryl-and heteroarylannulated [a] carbazoles by the reaction of propargyl ethers with 2-aryl-and 2-heteroarylindoles. In addition to the above reactions, metal triflates catalyzed dimerization of vinylarenes with the aid of a palladium catalyst (activation of C = C), nucleophilic substitution using a pyrrolyl group as a carbon leaving group (activation of C-C) and oxidative coupling between lactams and heterocyclic arenes (activation of C-H).

Crystal Structure of a Pyrrolyl-Substituted 4-Trifluoromethylcoumarin

Crystal Structure of 7-(1H-pyrrol-1-yl)-4-trifluoromethyl-2H-1-benzopyran-2-one has been determined by X-ray diffraction. The crystal, C14H8NO2F3, belongs to space group P21/n with cell dimensions of a = 10.201(6)A, b = 8.481(8)A, c = 13.864(8)A, β = 109.75(2)°. The final R value is 0.041 for 2602 reflections (I > 2.00 σ(I)). The coumarin and the pyrrole moieties are almost coplanar. The dihedral angle between the least-squares planes of the aromatic ring and the pyrrolyl group is 6.98(4)°.

Synthesis and properties of 5-pyrrolyl-cytidine and uridine derivatives

New 5-modified pyrimidine derivatives that were expected to form Hoogsteen-type triplexes have been synthesized, 5-pyrrolyl-2'-O-methylcytosine was designed as a protonated cytosine mimic to realize pH-independent triplex formation with the complementary G-C Watson-Crick base pair by inducing the imino tautomer of cytosine. 5-Pyrrolyl-2'-O-methyluridine was also synthesized to enhance the stacking effect for stabilization of triplexes. For the deprotection of the DMTr group in the phosphoramidite method, EtSi3H was added as the scavenger of the dimethoxytrityl-cation to avoid side-reactions on the pyrrolyl group. The triplex forming ability of TFOs containing modified nucleosides was evaluated by Tm experiments under various conditions.

Oxidative Addition and Reductive Elimination Reactions oftrans-[Ir(PPh3)2(CO)(NC4H4)] andtrans,cis-[Ir(PPh3)2(H)2(CO)(NC4H4)], Including N−H Bond-Forming Reductive Elimination of Pyrrole

The complex trans-(PPh3)2(CO)Ir(NC4H4) (1) has been synthesized and is an analogue of metal−aryl complexes, but with a nitrogen of the heteroaromatic group covalently bonded to the transition metal. Compound 1 readily undergoes initial reaction with a variety of substrates at the metal center rather than at the pyrrolyl nitrogen, allowing for the study of reactions between the pyrrolyl group and accompanying covalent ligands. These reactions ultimately produce N-substituted pyrroles, X-NC4H4 (X = C(O)CH3, C(O)C6H4CH3, H, SnMe3, SiMe3, SiEt3, Bcat). Compound 1 undergoes oxidative addition of H2 to form the stable Ir(III) product (PPh3)2(CO)Ir(H)2(NC4H4) (2). When pure 2 is heated, it undergoes simple elimination of H2 to regenerate 1; however, if 2 is heated for longer times under H2 in the presence of PPh3, it undergoes reductive elimination of pyrrole and forms (PPh3)3(CO)Ir(H). Qualitative analysis of the mechanism of this reaction suggests that it occurs by either direct reductive elimination from the ...

Di- tert -butyl(N-pyrrolyl)phosphane,-sulfide, and-selenide, studied by multinuclear magnetic resonance

Di-tert-butyl(N-pyrrolyl)phosphane (1),-sulfide (2) and-selenide (3) were studied by 1H, 13C, 15N, 31P and 77Se NMR spectroscopy in solution. Restricted rotation about the P–N bond was observed for 1 (ΔG≠C≈58.5 kJ/mol) and 2, 3 (ΔG≠C≈45 kJ/mol) by 1H and 13C NMR at variable temperature. The fairly high pyrrolyl rotation barrier in 1 is ascribed to the expected steric effects exerted by the tert-butyl groups and to repulsion between the lone pairs of electrons at the phosphorus and nitrogen atoms. These repulsive forces are reduced in 2 or 3, or in di-tert-butyl(phenyl) phosphane (ΔG≠C≈44 kJ/mol). Signs of coupling constants nJ(31P, 13C) and n+1J(31P, 1H) (n=2, 3) were determined by two-dimensional (2D) 13C/1H heteronuclear shift correlations. The preferred orientation of the pyrrolyl group in 1 is evident from the coupling constants 2J(31P, 13C(2))=+35.4 Hz and 2J(31P, 13C(5))=−9.3 Hz, typical of C(2) in syn and C(5) in anti position with respect to the assumed axis of the phosphorus lone pair. Hahn-echo extended (HEED) polarization transfer pulse sequences served for measuring 1J(31P, 15N) and isotope induced chemical shifts 1Δ15/14N(31P) from 31P NMR spectra.