Search results for "ORC"
showing 10 items of 4623 documents
Effect of π-Electron Delocalization on Tautomeric Equilibria – Benzoannulated 2-Phenacylpyridines
2006
Most benzoannulated 2-methylpyridines react with phenyllithium and substituted alkyl benzoates to give the corresponding 2-phenacylpyridines. 3-Methylisoquinoline is transformed into 2-benzoyl-3-methyl-1-phenyl-1,2-dihydroisoquinoline under these conditions, but replacement of phenyllithium with lithium isopropylcyclohexylamide is effective for production of 3-phenacylisoquinolines. Except in the cases of some substituted 6-phenacylphenanthridines, tautomeric mixtures of benzoannulated 2-phenacylpyridines in chloroform solution always contain the ketimine forms.(Z)-2-(2-Hydroxy-2-phenylvinyl)pyridine (enolimine) forms also contribute if the pyridine ring is not benzoannulated or if such ann…
Recent advances in electrochemical meso- and β-functionalization of porphyrins and electrografting of diazonium porphyrins
2020
Abstract Recent studies on electrochemical meso- and β-functionalization of porphyrins and electrografting of diazonium porphyrin are presented. First, the electrochemical oxidative C–C coupling between porphyrins will be presented, followed by the intermolecular and intramolecular meso- and β-substitutions of porphyrins. Then, the latest results on diazonium porphyrin electrografting will be reviewed.
Rearrangement of the carbon skeleton in the intramolecular photoadduct of anthracene and benzene rings
2003
Abstract The effectivity of optical switching between anthracene derivatives 3a,b and their intramolecular photocycloadducts 4a,b is impaired by traces of acid. The systematic treatment of 4a,b with an increasing excess of formic acid revealed that—apart from the normal enolether cleavage 4a,b → 6a,b → 7a,b —a cleavage with rearrangement of the carbon skeleton can occur: 5b → 6b′ . The driving force is a stability enhancement of the involved carbenium ions 5b → 5b′ . A further increased excess of formic acid leads finally to a competitive ether cleavage in the tetrahydrofuran ring 5b → 8 .
Optical Switching and Antenna Effect of Dendrimers with an Anthracene Core
2007
Dendrimers 6G(i) (i=1-4) consisting of an anthracene core and Fréchet dendrons which are attached via a CH(2)OCH(2) chain in the 9-position undergo quantitative and completely reversible intramolecular [4pi+4pi] cycloaddition. The process can be monitored by absorption and fluorescence measurements. The Fréchet dendrons act as an energy funnel that collects and focuses the photon energy but does not change the photostationary states, which for both directions are completely on the product side when the separate chromophores are selectively irradiated. The quantum yields of anthracene fluorescence and of singlet energy transfer from the dendrons to the core were studied as a function of dend…
Switching from intramolecular energy transfer to intramolecular electron transfer by the action of pH and Zn2+ co-ordination
2002
Abstract Intramolecular electron (eT) and energy transfer (ET) have shown to occur in a covalently linked donor–acceptor (CLDA) system consisting of a naphthalene donor covalently linked through a polyamine chain connector to an anthracene acceptor; the connector has been chosen in order to switch ON or OFF the energy flux as a function of its protonation state as well as by co-ordination to Zn 2+ . The largest energy transfer efficiency ( η =0.61) occurs for the fully protonated form (pH 9 (eT) from the lone pairs of the nitrogens to the excited fluorophore takes place, leading to complete quenching of the emission. On the other hand at neutral and basic pH values, co-ordination of Zn 2+ p…
Intramolecular photocycloaddition of anthracene and benzene ring systems
2002
Abstract The anthracenes 3a – c , substituted in the 9-position with 3,5-dialkoxybenzyloxymethyl groups exhibit, in diluted solutions, intramolecular [4π+4π] photocycloaddition reactions to the polycyclic compounds 4a – c . The quantitative processes are completely reversible by heating, unless acid-catalyzed cleavages lead to thermally stable mono- and diketones: 4a – c → 5a – c → 6 .
Intramolecular electronic excitation energy transfer in donor∕acceptor dyads studied by time and frequency resolved single molecule spectroscopy
2008
Electronic excitation energy transfer has been studied by single molecule spectroscopy in donor/acceptor dyads composed of a perylenediimide donor and a terrylenediimide acceptor linked by oligo(phenylene) bridges of two different lengths. For the shorter bridge (three phenylene units) energy is transferred almost quantitatively from the donor to the acceptor, while for the longer bridge (seven phenylene units) energy transfer is less efficient as indicated by the occurrence of donor and acceptor emission. To determine energy transfer rates and efficiencies at the single molecule level, several methods have been employed. These comprise time-correlated single photon counting techniques at r…
Selling a vote
2005
Abstract A voting function is a rule that determines the outcome of an election: taking the voters' votes as input, a voting function selects the winning candidate from the set of candidates receiving some vote. A voting function is immune to vote selling when, given that neither voter i nor voter j votes for the winning candidate, a change ceteris paribus in i's vote cannot make the candidate for which j votes the winner. It is shown that voting functions immune to vote selling have either a dictator (a voter who always determines the winning candidate) or a dictated candidate (a candidate who becomes the winner by just receiving some vote).
Novel isoquinoline derivatives as antimicrobial agents.
2013
The wide variety of potent biological activities of natural and synthetic isoquinoline alkaloids encouraged us to develop novel antimicrobial isoquinoline compounds. We synthesized a variety of differently functionalized 1-pentyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines (THIQs), including dihydroisoquinolinium salts (2 and 5), methyl pentanoate-THIQ (6), 1-pentanol-THIQ (7), ester derivatives (8-15) and carbamate derivatives (16-23). We employed classic intramolecular Bischler-Napieralski cyclodehydration to generate the isoquinoline core. All the structures were characterized by nuclear magnetic resonance and mass spectrometry. The bactericide and fungicide activities were evaluated f…
Structure of chloroantimonates(III) with an imidazolium cation: (C3H5N2)[SbCl4] and (C3H5N2)2[SbCl5]
2003
Abstract Two different chloroantimonates(III) with an imidazolium cation have been synthesized by the reaction of antimony trichloride and imidazole in an aqueous solution of hydrochloric acid. The crystals of (C3H5N2)[SbCl4] are monoclinic, space group C2/c, while (C3H5N2)2[SbCl5] crystallizes in the orthorhombic system, space group Pbcn. Both crystals are built of one dimensional zig-zag chains composed of [SbCl6]3− octahedra connected by edges and corners, respectively. The cavities between inorganic chains are filled by imidazolium cations. In both structures, one crystallographically independent imidazolium cation is rotationally disordered, and the positions of all atoms are split bet…