Pincer compounds containing a central pyrrole linked through methylene groups in the 2,5-positions to two N-imidazole, N-pyrazole and N-1,2,4-triazole heterocyles have been prepared via a common quaternary amine precursor. Alkylation of the imidazole groups using methyl iodide or benzyl bromide gave imidazolium compounds. The methylated iodide salt was characterised crystallographically, showing significant pyrrole I center dot center dot center dot HN, imidazolium I center dot center dot center dot HC and imidazolium I center dot center dot center dot(sp(2)-C) interactions leading to a U-shaped conformation of the cationic pincer compound. The alkylated cations which were investigated as precursors to pyrrole-carbene pincer ligands, but all attempts to either coordinate palladium or deprotonate using silver oxide led to cleavage of the heterocycles from the central pyrrole. The result was the formation of palladium and silver complexes containing 3-N-methylimidazole (3-N-MeIm) or 3-N-benzylimidazole (3-N-BzIm) ligands: (3-N-MeIm)PdI2, (3-N-MeIm)PdCl2 and [(3-N-MeIm)(2)Ag]I, with the (3-N-MeIm)PdI2 complex characterised by crystallography. Pyrazole, 3,5-dimethylpyrazole and 1,2,4-triazole pincer compounds were prepared, the latter characterised by a molecular structure determination. The pyrazole and 1,2,4-triazole pincers coordinate directly to palladium through the deprotonated central pyrrolyl and neutral N-donors on the flanking heterocycles. (C) 2014 Elsevier B. V. All rights reserved.

AbstractTreatment of the nitrone (I) with Grignard reagents or organolithium compounds results in efficient and stereoselective formation of trans‐2‐substituted 3‐piperidinols such as (IV).

This report presents photophysical properties of self-assembled porphyrin-fullerene complexes as solar harvesting dyes. We study the lifetimes of photoinduced charge-separated states with time-resolved spectroscopy in various structural modifications.

The coordinatively unsaturated tri-p-tolylgermyl complex RuCl(Ge[p-tolyl](3))(CO)(PPh3)(2) (1) is obtained in good yield through the reaction between HGe(p-tolyl)(3) and RuCl(Ph)(CO)(PPh3)(2). On treatment of 1 with 1 equiv of NaS2CNR2' (R' = Et, Me), the chloride ligand is displaced and the corresponding coordinatively saturated complexes Ru(kappa(2)-S2CNR2')(Ge[p-tolyl](3))(CO)(PPh3)(2) (2a, R' = Et; 2b, R' = Me) are formed. One of the PPh3 ligands in 2a is labile and undergoes substitution readily on addition of CO to give the cis-dicarbonyl complex Ru(kappa(2)-S2CNEt2)(Ge[p-tolyl](3))(CO)(2)(PPh3) (3). On addition of NaS2CNMe2 to 2b, a PPh3 ligand is displaced by one sulfur atom while the other sulfur atom displaces one of the p-tolyl groups on germanium to give Ru(kappa(2)(Ge,S)-Ge[p-tolyl](2)S2CNMe2)(kappa(2)-S2CNMe2)(CO)(PPh3) (4). Complex 4 is also formed on addition of excess NaS2CNMe2 to 1. Treatment of 1 with pyridine and ethanol under ambient conditions also results in cleavage of one of the germyl p-tolyl groups, and the product formed is the coordinatively unsaturated, ethoxy-substituted germyl complex RuCl(Ge[OEt][p-tolyl](2))(CO)(PPh3)(2) (5). The ethoxy group in 5 is labile, and on contact with n-propanol in solution, alkoxy group exchange slowly occurs to give RuCl(Ge[(OPr)-Pr-n][p-tolyl](2))(CO)(PPh3)(2) (6). This reaction is reversible, and treatment of 6 with ethanol returns S. In a related reaction, treatment of 5 with water gives the hydroxy-germyl analogue RuCl(Ge[OH][p-tolyl](2))(CO)(PPh3)(2) (7). The single-crystal X-ray structures of 1, 2a, 3, and 4 are presented.

Previous studies have identified the 3,6-dialkyl-4-hydroxy-pyran-2-one marine microbial metabolites pseudopyronines A and B to be modest growth inhibitors of Mycobacterium tuberculosis and a range of tropical diseases including Plasmodium falciparum and Leishmania donovani. In an effort to expand the structure–activity relationship of this compound class towards infectious diseases, a library of natural product and natural product-like 4-methoxy-6-styryl-pyran-2-ones and a subset of catalytically reduced examples were synthesized. In addition, the photochemical reactivity of several of the 4-methoxy-6-styryl-pyran-2-ones were investigated yielding head-to-head and head-to-tail cyclobutane dimers as well as examples of asymmetric aniba-dimer A-type dimers. All compounds were evaluated for cytotoxicity and activity against M. tuberculosis, P. falciparum, L. donovani, Trypanosoma brucei rhodesiense and Trypanosoma cruzi. Of the styryl-pyranones, natural product 3 and non-natural styrene and naphthalene substituted examples 13, 18, 21, 22 and 23 exhibited antimalarial activity (IC50 <10 μM) with selectivity indices (SI) >10. Δ7 Dihydro analogues were typically less active or lacked selectivity. Head-to-head and head-to-tail photodimers 5 and 34 exhibited moderate IC50s of 2.3 to 17 μM towards several of the parasitic organisms, while the aniba-dimer-type asymmetric dimers 31 and 33 were identified as being moderately active towards P. falciparum (IC50 1.5 and 1.7 μM) with good selectivity (SI ∼80). The 4-tert-butyl aniba-dimer A analogue 33 also exhibited activity towards L. donovani (IC50 4.5 μM), suggesting further elaboration of this latter scaffold could lead to the identification of new leads for the dual treatment of malaria and leishmaniasis.

Nucleophilic addition of Grignard reagents and organolithium species to a 3-silyloxy-3,4,5,6-tetrahydropyridine N-oxide provides trans-2,3-disubstituted N-hydroxypiperidines exclusively. The application of this methodology to the preparation of a diversity of useful trans-2-substituted-3-hydroxypiperidines, a concise synthesis of (+)-swainsonine, and an enantiopure 1-substituted quinolizidine of utility in target-directed synthesis is reported.

A novel high power, broad bandwidth (450-1750nm) probe laser has been successfully constructed and characterized for transient absorption spectroscopy. Supercontinuum pulses are generated using a nanosecond pulsed Q-switched Nd:YAG laser (1064nm, 7 ns, 20 Hz) in 15m photonic crystal fibers. High spectral quality and stable output power have been reported using this technique. The supercontinuum saturates at pulse powers of 100μW (5 μJ/pulse; 700 W pulse power).

World Scientific Series on Carbon NanoscienceHandbook of Carbon Nano Materials, pp. 375-390 (2011) No AccessPorphyrin-Fullerene Supramolecular ChemistryPeter D. W. Boyd, Ali Hosseini, John D. van Paauwe, and Christopher A. ReedPeter D. W. BoydDepartment of Chemistry, The University of Auckland, Private Bag 92019, Auckland 1142, New ZealandCorresponding author., Ali HosseiniDepartment of Chemistry, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand, John D. van PaauweDepartment of Chemistry, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand, and Christopher A. ReedDepartment of Chemistry, University of California, Riverside Riverside, California 92521, USAhttps://doi.org/10.1142/9789814327824_0011Cited by:2 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: The following sections are included: Introduction Molecular Porphyrin Hosts for Fullerenes The Porphyrin-Fullerene Interaction Cobalt(II) Porphyrins and Fullerenes Synthesis of bis-porphyrins Binding Constants and Charge Transfer Bands X-ray Structures of T3,4,5-OMePP Cocrystallates Conclusions Acknowledgments References FiguresReferencesRelatedDetailsCited By 2Cyclotriveratrylene-Containing PorphyrinsJude Deschamps, Adam Langlois, Gaël Martin, Léo Bucher and Nicolas Desbois et al.7 September 2016 | Inorganic Chemistry, Vol. 55, No. 18Synthesis, characterization and photophysical studies of ß-triazolomethyl-bridged porphyrin-benzo- a-pyrone dyadsDILEEP KUMAR SINGH and MAHENDRA NATH17 March 2016 | Journal of Chemical Sciences, Vol. 128, No. 4 Handbook of Carbon Nano MaterialsMetrics History PDF download

A ferrocene (Fc) functionalized bis-porphyrin molecule has been synthesized as a host for fullerenes. The porphyrin used in these studies was prepared using a mixed boronic acid Suzuki reaction, which gives A2BC type porphyrins in high yield. The bis-porphyrin was characterized through 1H NMR spectroscopy, high-resolution mass spectroscopy and analyzed via molecular modeling studies. Complexation experiments with fullerenes utilizing both UV-visible and fluorescence spectroscopy demonstrated formation of strong complexes for the bis-porphyrin. A short-lived charge transfer luminescent state is detected for the fullerene adducts. Owing to the tight coupling of the fullerene and porphyrin partners, the host-appended Fc moiety does not show a direct role in the pattern of photoinduced processes upon excitation of either chromophores, but causes blue-shift of the NIR CT luminescence compared to previously investigated systems without appended fragments. Instead, the active role of Fc in photoinduced processes is observed for the guest molecules alone, where photoinduced energy transfer from the porphyrin to the ferrocene occurs.

Reaction of PhCONH2 with [WCl6] under reflux in benzene gives a near quantitative yield of [WOCl4(NCPh)] (1) which can be prepared directly by the reaction of PhCN and [WOCl4]. PhCONH2 reacts with [WOCl4] under reflux in benzene to give [WO2Cl2(NCPh)] (2) and with [NbCl5] under similar conditions to give [NbOCl3(NCPh)] (3). PhCONH2 and TiCl4 give [TiCl4(NH2COPh)2] (4). Reaction of the aroyl isocyanate PhCONCO with [WOCl4] gave [WOCl4(NCPh)] (1) and 4-Me3CPhCONCO and [WOCl4] gave [WOCl4(NCPhCMe3-4)] (5). PhCONCO reacts catalytically with [WOCl4] or [WOCl4(NCPh)] to give quantitative yields of PhCN. Similarly, 4-Me3CPhCONCO and 2-ClCPhCONCO react catalytically with [WOCl4] to give complete conversion to 4-Me3CPhCN and 2-ClCPhCN. DFT studies show structures and intermediates in support of a possible catalytic mechanism. This involves initial complexation followed by formation of a metallocycle from the WO bond and the CN bond of the isocyanate. Rearrangement and elimination of CO2 leads to an amidate complex that undergoes C–O bond scission and O migration to the W atom to give PhCN bound to the WOCl4 moiety in a cis arrangement. This complex is unstable with respect to dissociation which completes the catalytic cycle. The overall reaction WOCl4+PhC(O)NCO→WOCl4·PhCN+CO2 is exothermic (ΔH=−20.7kJmol−1) and is favoured from free energy considerations (ΔG=−69.3kJmol−1).

N-[1-Alkylpyridin-4(1H)-ylidene]amides (PYAs) are a new class of easily prepared, neutral N-donor ligands that share some features in common with N-heterocyclic carbenes. They are strongly electron-donating toward metal centers, and a palladium(II) complex of one of these ligands has been shown to successfully catalyze both the Heck-Mizoroki and Suzuki-Miyaura cross-coupling reactions.

The complementary use of spectroscopy and electrochemistry shed light onto the supramolecular interactions of calixarene scaffold bearing bisporphyrins 1 and 2 as hosts with a series of fullerenes –C60, Sc3N@C80, and Lu3N@C80 – as guest molecules. Importantly, the present work shows a noticeable variation in binding strength when C60 or endohedral fullerene guests are included into the bisporphyrins hosts. These sizeable differences could be clarified by computational models of the host–guest complexes, on the one hand, and a systematic investigation of the electron transfer chemistry, on the other hand. Detailed studies document an oxidative charge transfer (i.e., electron transfer from the bisporphyrin to the fullerene) for the C60 inclusion complexes, while a reductive charge transfer (i.e., electron transfer from the fullerene to porphyrin) is operative in the endohedral metallofullerene host–guest complexes.

Racemic 2-{[1-(chloromethyl)-5-nitro-3-{5-[2-(dimethylamino)ethoxy]indol-2-carbonyl}-1,2-dihydro-3H-benzo[e]indol-7-yl]sulfonyl}aminoethyl dihydrogen phosphate, a synthetic nitro derivative of the duocarmycins, is a hypoxia-selective prodrug active against radiation-resistant tumour cells at nontoxic doses in mice. An intermediate in the synthesis of this prodrug was resolved by chiral HPLC and the absolute configuration assigned by X-ray crystallography. The intermediate was used to prepare the prodrug's enantiomers, and also the enantiomers of the active nitro and amino metabolites. In vitro analysis in the human cervical carcinoma cell line SiHa showed that both nitro enantiomers are hypoxia-selective cytotoxins, but the "natural" S enantiomer is at least 20-fold more potent. Examination of extracellular amino metabolite concentrations demonstrated no enantioselectivity in the hypoxia-selective reduction of nitro to amino. Low levels of amino derivative were also found in aerobic cell suspensions, sufficient to account for the observed oxic toxicity of the nitro form. At an equimolar dose in SiHa-tumour bearing animals, the (-)-R enantiomer of the prodrug was inactive, while the (+)-S enantiomer caused significantly more hypoxic tumour cell kill than the racemate. At this dose, the combination of (+)-S-prodrug and radiation eliminated detectable colony-forming cells in four out of five treated tumour-bearing animals.

Noncovalent binding of fullerenes to bisporphyrins was studied in the gas phase by energy-dependent collision-induced dissociation (CID) with Xe under single-collision conditions. The electrospray ionization mass spectra of calix[4]arene-linked bisporphyrins show that bisporphyrins take up to 3-4 protons, depending on the type of meso-substituents. Of the protonated bisporphyrins, the diprotonated species form stable 1:1 complexes with fullerenes (C(60) and C(70)). CID cracking patterns of the diprotonated bisporphyrins indicate that each monomeric porphyrin moiety is singly protonated. CID yield-energy curves obtained from the 1:1 diprotonated bisporphyrin-fullerene complexes suggest that a fullerene occupies the endo-binding site intercalated between the two singly protonated porphyrin moieties. In the cases of 1:2 diprotonated bisporphyrin-fullerene complexes, CID results show that one fullerene binds inside (endo-binding) and the other outside (exo-binding). The exo-binding mode is energetically almost identical to the binding of fullerenes to singly protonated porphyrin monomers. The endo-binding energy is at least twice the exo-binding energy. To gain insights into the binding mode, we optimized structures of diprotonated bisporphyrins and their 1:1 endo-complexes with fullerenes, and calculated the endo-binding energy for C(60), C(70) (end-on), and C(70) (side-on). The endo-binding of fullerenes to diprotonated bisporphyrins nearly doubles the π-π interactions while reducing the electrostatic repulsion between the two singly protonated porphyrin moieties. The side-on binding of C(70) is favored over the end-on binding because the former exerts less steric strain to the lower rim of calixarene.

The reaction of PhBCl2 with free base triarylcorroles results in a spontaneous reduction to give diboron corrole complexes (PhBHBPh)(Cor) in which a proton has been captured to forma bridgingB-H-B group encapsulated within the corrole ligand. The proposed mechanism is supported by the reaction of PhBF2 with H(3)Cor to give (PhBF)(BPh)(Cor) in which no reduction has occurred.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The nucleation of chromium dihalide clusters is investigated by studying clusters of the form Cr(n)X(2n) (n <or= 4, X = F, Cl, Br, and I) for different spin states and the corresponding low temperature solid-state modifications using density functional theory. Using both wave function based (coupled cluster) and density functional theory, we predict that in all cases the ground state of the CrX(2) monomer is a bent (5)B(2) state arising from a weakly Renner-Teller distorted (5)Pi(g) state of the linear CrX(2) unit. These quintet units can form antiferromagnetically coupled, two-dimensional chains with chromium being bridged by two halides and a nucleation growth pattern that resembles the structural motif found for the solid state. Deviations from this two-dimensional chain growth are only found for the trimers and tetramers of CrBr(2) and CrI(2), where a "triangular" three-dimensional geometry takes slight precedence over the planar ribbon motif. We find that each single CrX(2) unit adds an almost constant amount of energy between 45 and 50 kcal/mol to the cluster growth. This is in accordance with the calculated sublimation energies for the solid state which gave 58 kcal/mol for CrF(2), and between 41 and 46 kcal/mol for CrCl(2), CrBr(2), and CrI(2). The large deviation of the calculated from the experimental sublimation energy for CrF(2) is due to the high electronegativity of fluorine ligand, which substantially increases the ionic interactions, resulting in a much more tightly packed solid-state structure, which is not so well described by spin-broken density functional theory. In accordance with this, CrF(2) shows an unusually large bulk modulus (395 kbar) compared to the heavier halides CrCl(2) (82 kbar), CrBr(2) (40 kbar), and CrI(2) (18 kbar).

Density functional theory has been used to analyze the detailed reaction mechanism for the reductive cleavage of CO(2) by a dinitrogen bridged bis-beta-diketoiminatediiron complex, L(tBu)Fe-N(2)-FeL(tBu) (I), recently reported by Holland and co-workers. A number of pathways have been investigated and the most likely mechanism correlates well with experimental evidence. A rationale has been provided for the binding of CO(2), the release of CO, and the ready formation of CO(3)(2-). Our results show that the insertion of CO(2) into the diiron complex is the rate determining step of the reductive cleavage reaction. An intramolecular reduction step from the reduced dinitrogen bridge is proposed which serves to increase the activation of CO(2). This is followed by an intersystem crossing from the septet to the nonet state which acts as a driving force for the subsequent release of CO. The overall reductive cleavage reaction is exergonic by 120 kJ/mol, and further reaction of the released CO with the starting diiron complex is also predicted to be strongly exergonic.

Durch basenunterstützte Reduktion einer Palladium(II)-Vorstufe wurde der erste Palladium(I)-NHC-Komplex (NHC=N-heterocyclisches Carben) in hoher Ausbeute hergestellt und isoliert. Die Position des einzigartigen terminalen Hydridliganden (siehe Bild; PdI cyan, H weiß, N blau) wurde durch Neutronenbeugung am Einkristall bestimmt, und das fluktuierende Verhalten des Komplexes in Lösung wurde untersucht. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

The crystal structure of the title compound, C(34)H(54)N(2)O(4), has been solved in order to prove the relative and absolute chirality of the newly-formed stereocentres which were established using an asymmetric Diels-Alder reaction at an earlier stage in the synthesis. This unprecedented stable dialdimine contains a 14-membered ring and was obtained as the minor diastereoisomer in the Diels-Alder reaction. The absolute stereochemistry of the stereocentres of the acetal functionality was known to be R based on the use of a chiral (R)-trisubstituted dienophile derived from enantiopure (S)glyceraldehyde. The assignment of the configuration in the dienophile and the title di-aldimine differs from (S)-glyceraldehyde due to a change in the priority order of the substituents. The crystal structure establishes the presence of six stereocentres all attributed to be R. The 14-membered ring contains two aldimine bonds [C-N = 1.258 (2) and 1.259 (2) angstrom]. It adopts a similar conformation to that proposed for trans-trans-cyclotetradeca-1,8-dienes.