Search results for "Acene"

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 .

The different redox-activity of dianthrylbenzene and dianthrylbiphenyl

1989

Abstract The reduction of dianthrylbenzene and dianthrylbiphenyl to stable tetraanion salts is described by NMR spectroscopy and cyclic voltammetry. The significantly different Coulomb interactions between the anthracene units are compared with those in dianthrylalkanes.

Electrochemistry and spectroelectrochemistry of bismanganese biscorroles dyads

2011

Three manganese biscorrole dyads were synthesized, physicochemically characterized and investigated as to their electrochemistry and spectroelectrochemistry in nonaqueous media. Each dyad contained the same two corroles linked in a face-to-face arrangement via one of the three different linking groups, 9,9-dimethylxanthene, anthracene or diphenylether, the exact nature of which determined the distance and possible interaction between the two metallomacrocycles. The initial compounds contained Mn ( III ) in their air stable form and were shown to exhibit two major redox processes, one being a Mn (III)/ Mn (IV) conversion and the other being either Mn ( III )/ Mn ( II ) or reduction at the c…

Electronic Interactions in a New π-Extended Tetrathiafulvalene Dimer

2006

The first pi-extended tetrathiafulvalene (exTTF) dimer in which the two exTTF units are covalently connected by 1,3-dithiole rings has been obtained in a multistep synthetic procedure involving the Ullmann cross-coupling reaction by using copper(I) thiophene-2-carboxylate (CuTC). The electronic spectrum reveals a significant electronic interaction between the exTTF units. The electrochemical study carried out by cyclic voltammetry in solution and in thin-layer conditions, and the electrochemical simulation and spectroelectrochemical (SEC) measurements confirm the electronic communication and show that the oxidation of dimer 14 occurs as two consecutive 2 e(-) processes D(0)-D(0)-->D(2+)-D(0…

Dendron to central core S1-S1 and S2-S(n) (n1) energy transfers in artificial special pairs containing dendrimers with limited numbers of conformatio…

2013

Two dendrimers consisting of a cofacial free-base bisporphyrin held by a biphenylene spacer and function- alized with 4-benzeneoxomethane (5-(4-benzene)tri-10,15,20-(4-n-octyl- benzene)zinc(II)porphyrin) using either five or six of the six available meso-positions, have been synthesized and characterized as models for the an- tenna effect in Photosystems I and II. The presence of the short linkers, -CH2O-, and long C8H17 soluble side chains substantially reduces the number of conformers (foldamers) compared with classic dendrimers built with longer flexible chains. This simpli- fication assists in their spectroscopic and photophysical analysis, notably with respect to fluorescence resonance…

Allergic contact dermatitis from anthrarobin.

1995

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…

Mucoadhesive Polymeric Films to Enhance Barbaloin Penetration Into Buccal Mucosa: a Novel Approach to Chemoprevention.

2018

Nowadays, chemoprevention by administering natural supplements is considered an attractive strategy to reverse, suppress, or prevent the evolution of premalignant oral lesions. In particular, Barbaloin exhibits anti-proliferative, anti-inflammatory, and anti-cancer properties, and it results useful in multi-therapy with classic chemotherapeutics. Therefore, in this work, mucoadhesive buccal films, as locoregional drug delivery system able to provide a targeted and efficient therapeutic delivery of Barbaloin, are proposed. Thus, Aloin extract-loaded Eudragit (R) RL100 or Eudragit (R) RS100-based buccal films were designed in order to obtain an easily self-administrable formulation capable of…

Acene-type donors bearing one 1,3-dithiole ring

1999

Abstract A series of acene-type donors bearing only one 1,3-dithiole ring have been synthesized by following a Wittig-Horner reaction from 7 H -benz[ d,e ]anthracen-7-one and several phosphonate esters. The excellent donor properties have been studied using both experimental techniques and quantum-chemical calculations and reveal that the extraction of the first electron in the oxidation process occurs from the dithiole ring (0.42 e) and the acene unit (0.58 e).

Palladium-Catalyzed Arylation of Linear and Cyclic Polyamines.

2005

Synthetic protocols for the palladium-catalyzed arylation of various linear and cyclic polyamines and polyoxapolyamines has been worked out. Pd(0) and Pd(II) complexes with such phosphine ligands as dppf, BINAP, PPF-OMe, P(tBu) 3 , 2-ditert-butylphosphino- 1,1'-biphenyl have been explored in the catalytic amination reactions. Monoamination of chloro-, bromo-, and iodoarenes with di-, tri-, and tetraamines have been carried out, condi- tions for di- and polyarylation of linear polyamines have been elaborated. Successful aryla- tion of 1,4,7,10-tetraazacyclododecane (cyclene) and 1,4,8,11-tetraazacyclotetradecane (cy- clam) have been conducted. Intramolecular diamination of dihaloarenes such …