Showing papers on "Benzophenone published in 2001"

Comparison of DNA Damage Photoinduced by Ketoprofen, Fenofibric Acid and Benzophenone via Electron and Energy Transfer¶

Abstract: Ketoprofen (KP) and fenofibrate, respectively, anti-inflammatory and hypolipidemiant agents, promote anormal photosensitivity in patients and may induce photoallergic cross-reactions correlated to their benzophenone-like structure. Here, their ability to photosensitize the degradation of biological targets was particularly investigated in DNA. The photosensitization of DNA damage by KP and fenofibric acid (FB), the main metabolite of fenofibrate, and their parent compound, benzophenone (BZ), was examined on a 32P-end-labeled synthetic oligonucleotide in phosphate-buffered solution using gel sequencing experiments. Upon irradiation at lambda > 320 nm, piperidine-sensitive lesions were induced in single-stranded oligonucleotides by KP, FB and BZ at all G sites to the same extent. This pattern of damage, enhanced in D2O is characteristic of a Type-II mechanism. Spin trapping experiments using 2,2,6,6-tetramethyl-4-piperidone have confirmed the production of singlet oxygen during drug photolysis. On double-stranded oligonucleotides, highly specific DNA break occurred selectively at 5'-G of a 5'-GG-3' sequence, after alkali treatment. Prolonged irradiation led to the degradation of all G residues, with efficiency decreasing in the order 5'-GG > 5'-GA > 5'-GC > 5'-GT, in good agreement with the calculated lowest ionization potentials of stacked nucleobase models supporting the assumption of a Type-I mechanism involving electron transfer, also observed to a lesser extent with adenine. Cytosine sites were also affected but the action of mannitol which selectively inhibited cytosine lesions suggests, in this case, the involvement of hydroxyl radical, also detected by electronic paramagnetic resonance using 5,5-dimethyl-1-pyrrolidine-1-oxide as spin trap. On a double-stranded 32P-end-labeled 25-mer oligonucleotide containing TT and TTT sequences, the three compounds were found to photosensitize by triplet-triplet energy transfer the formation of cyclobutane thymine dimers detected using T4 endonuclease V.

Elastic and thermoelastic properties of selected organic crystals: Acenaphthene, trans-azobenzene, benzophenone, tolane, trans-stilbene, dibenzyl, diphenyl sulfone, 2,2'-biphenol, urea, melamine, hexogen, succinimide, pentaerythritol, urotropine, malonic acid, dimethyl malonic acid, maleic acid, hippuric acid, aluminium acetylacetonate, iron acetylacetonate, and tetraphenyl silicon

Abstract: Elastic and thermoelastic properties of the 21 title crystalline species have been determined from ultrasonic resonant frequencies of plates and their shift upon variation of temperature, respectively. In addition, the tensors of thermal expansion have been measured by the aid of a Fizeau interferometer. An analysis of the elastic behaviour of organic crystals, including earlier elastic data of other organic compounds taken from the literature, revealed common features of organic crystals and organic liquids in respect to the scalar invariants C = (c 11 + c 22 + c 33 + c 44 + c 55 + c 66 + c 12 + c 13 + c 23 )/9 and d log C/dT, T temperature, especially in the case of Van-der-Waals crystals. Contrary to ionic crystals the invariant C increases in these crystals with larger molecular volume. Crystals with strong hydrogen bonds like dicarboxylic or sulfonic acids behave rather like ionic crystals. The influence of a small molecular elastic stiffness, as observed in plastic crystals, is clearly recognizable in the elastic properties. The impact of structural details on the invariant C and its logarithmic temperature derivative is surprisingly small.

Evaluation of N-Aromatic Maleimides as Free Radical Photoinitiators: A Photophysical and Photopolymerization Characterization

Abstract: Photopolymerizable compositions were prepared using acrylate monomers in combination with various N-aromatic maleimides. N-aromatic maleimides were segregated into two groups: those that could adopt a planar conformation and those that could not adopt a planar conformation. The maleimides were characterized using single-crystal X-ray diffraction spectroscopy, laser flash photolysis spectroscopy, UV−vis absorption spectroscopy, and photodifferential scanning calorimetry. Planar N-aromatic maleimides were found to have a low relative excited-state triplet yield, showing significant shift of the primary maleimide UV absorption band with changes in solvent polarity, and did not initiate free radial polymerization upon direct UV excitation. Twisted N-aromatic maleimides have a higher relative triplet yield, show negligible shift of the primary maleimide UV absorption band, with solvent polarity, and initiate free radical polymerization upon direct excitation. Addition of benzophenone was found to dramatically...

Time-resolved spectroscopy of sulfur- and carboxy-substituted N-alkylphthalimides.

Abstract: The photophysical and photochemical properties of N-phthaloylmethionine (1), S-methyl-N-phthaloylcysteine methyl ester (2) and N-phthaloyltranexamic acid (3) were studied by time-resolved UV/Vis spectroscopy, using laser pulses at 248 or 308 nm. The quantum yield of fluorescence is low (Φf<10⁻²) for 1–3 in fluid and glassy media, whereas that of phosphorescence is large (0.3–0.5) in ethanol at −196 °C. The triplet properties were examined in several solvents, at room temperature and below. The spectra and decay kinetics are similar, but the population of the π,π* triplet state, as measured by T–T absorption, is much lower for 1 and 2 than for 3 or N-methyltrimellitimide (5′) at ambient temperatures. The quantum yield (ΦΔ) of singlet molecular oxygen O₂(1Δg) formation is substantial for 3 and 5′ in several air- or oxygen-saturated solvents at room temperature, but small for 2 and 1. The quantum yield of decomposition is substantial (0.2–0.5) for 3 and small (<0.05) for 2 and 1. It is postulated that photoinduced charge separation in the spectroscopically undetectable ³n,π* state may account for the cyclization products of 1 and 2. In aqueous solution, this also applies for 3, whereas in organic solvents cyclization involves mainly the lower lying ³π,π* state. Triplet acetone, acetophenone and xanthone are quenched by 1–3 in acetonitrile; the rate constant is close to the diffusion-controlled limit, but smaller for benzophenone. While the energy transfer from the triplet ketone occurs for 3, a major contribution of electron transfer to the N-phthalimide derivative is suggested for 1 and 2, where the radical anion of benzophenone or 4-carboxybenzophenone is observed in alkaline aqueous solution.

Preparation and characterization of novel basic polysulfone polymers

Abstract: Two synthesis routes for the preparation of novel base-modified polysulfones (PSUs; Udel®) were investigated: (1) the addition of the basic aromatic ketones 2,2'-dipyridylketone and 4,4'-bis-(diethylamino)benzophenone and the basic aromatic aldehydes N,N-dimethylamino-benzaldehyde, pyridine-2-aldehyde, pyridine-3-aldehyde, and pyridine-4-aldehyde to lithiated PSU and (2) the reaction of lithiated PSU with basic aromatic carboxylic acid esters such as 4-N,N-dimethylaminobenzoic acid ethylester, pyridine-2-carboxylic acid ethylester, pyridine-3-carboxylic acid ethylester, and pyridine-4-carboxylic acid ethylester. Both synthesis routes lead to a high degree of conversion, without the occurrence of crosslinking. This is remarkable, especially for the reaction of lithiated PSU with the ester compounds, because the -(C=O)-Ar groups formed by the reaction of the ester with PSU-Li are not further converted with the remaining PSU-Li sites to (crosslinked) PSU-C(-OLi)-Ar-PSU alcoholates, as normally observed when esters are reacted with Li-organic compounds. Starting with dilithiated PSU, we obtained degrees of substitution of 0.8-2 groups per PSU repeating unit. The structures and compositions of the modified PSU polymers were confirmed with NMR spectroscopy and elemental analysis. The modified polymers were also characterized via thermogravimetric analysis (thermal stability). Interestingly, the product of the reaction of lithiated PSU with 4,4'-bis-(diethylamino)benzophenone could be oxidized to a deep blue polymeric dye that showed proton self-conductivity.

Multiple Structures in Supramolecular Solids: Benzophenone Embedded in Three Different C-Methylcalix[4]resorcinarene/bipyridine Frameworks

Abstract: Three different supramolecular frameworks based on C-methylcalix[4]resorcinarene (CMCR) and 4,4‘-bipyridine are described. All contain benzophenone molecules as guests and are prepared by almost identical hydrothermal procedures, indicating that variations during the cooling process, rather than templating, can lead to different phases. The benzophenone molecules show significantly different conformations, with energies calculated to be 10−17 kJ/mol higher than that of the isolated benzophenone molecule. CMCR exhibits chair, boat, and crown-like conformations in the three solid phases.

Intramolecular Charge Transfer and Photochemical Isomerization in Donor/Acceptor-Substituted Butadienes

Abstract: Intramolecular charge transfers, triplet state properties, and photoisomerization of five donor/acceptor (D/A) substituted butadienes were investigated. Four of these derivatives (1−4) show dual fluorescence arising from a locally excited (LE) state and a considerably more polar intramolecular charge transfer (ICT) state. The presence of an amino substituent with the nitrogen atom directly attached to the butadiene chain is essential for observing dual fluorescence in this class of compounds. The compounds undergo E−Z photoisomerization from the excited singlet state with a quantum efficiency of about 0.1 in benzene at room temperature. The intersystem crossing efficiency for these compounds is negligible. The triplet excited-state properties of the five butadienes have been characterized via triplet−triplet sensitization with benzophenone as the donor.

Belokon's Ni(II) complex as a chiral masked glycine for the diastereoselective synthesis of 2-substituted 1-aminocyclopropane carboxylic acids

Abstract: (1S,2R)- and (1R,2S)-Allonorcoronamic acids have been efficiently synthesised from the cyclic sulfate of 1,2-propanediol and Belokon's complex (a complex of Ni(II) with glycine-(S)-2-[N′-(N-benzylprolyl)amino]benzophenone Schiff base ligands). The stereochemical outcome of the reaction was totally controlled by the sulfate partner.

Specific Solvent Effects on the Structure and Reaction Dynamics of Benzophenone Ketyl Radical

Abstract: Complex formation reaction between benzophenone ketyl (BPK) radical and triethylamine was investigated by means of transient absorption and time-resolved ESR methods. The formation constants (Kf's) in benzene, toluene, o-xylene, and anisole were measured by a transient absorption method. The enthalpy and entropy changes upon the complex formation were determined by van't Hoff plots of Kf values around 300 K. The ΔG values in the complex formation reaction at 298 K were calculated from these thermodynamic parameters, which show notable difference from those in aliphatic solvents and chlorotoluenes previously reported. The BPK conformation in these solvents was investigated by analyzing the time-resolved ESR spectra of BPK and by the DFT calculation. The hyperfine coupling constant of hydroxy-proton (aOH) was found to depend on solvent as well and there exists a clear correlation between the aOH and Kf (or ΔG) values. It was concluded that the conformation of BPK, especially the conformation between OH and ...

Reactivity of Benzophones in the Different Binding Sites of Sodium Cholate Aggregates

Abstract: The reactivity of excited benzophenone (Bp) and 4,4‘-dimethylbenzophenone (DMBp) in the presence of sodium cholate (NACh) aggregates was studied by following the kinetics of the excited triplet states and the ketyl radicals of both ketones. At low NACh concentrations only primary aggregates are present in solution. The ketyl radicals were formed from the reaction of the triplet ketones bound to the primary sites. The decay of the ketyl radicals occurred primarily by the reaction of these radicals in water. Some long-lived triplets included in the primary aggregate were also observed. A different reactivity was observed at higher NACh concentrations where secondary aggregates are present. The binding process associated with the secondary binding sites is much faster than for the primary site. The hydrogen abstraction reaction in the secondary binding site is too slow to compete with the exit process, but self-quenching competes efficiently, leading to a shortening of the triplet lifetimes for both ketones....

Poly(pyrroles) containing chiral side chains: effect of substituents on the chiral recognition in the doped as well as in the undoped state of the polymer film

Abstract: The chiral discrimination of different poly(pyrroles) grafted by chiral side chains was investigated both in the doped and undoped state of the polymer films. To verify the enantioselective properties in the doped state, cyclic voltammograms were recorded in acetonitrile in the presence of the enantiomers of camphorsulfonic acid and the potentiodynamic polymerization of the appropriate monomers was performed using the same chiral electrolytes. The enantiomericrecognition in the undoped state was investigated by the application of these modified electrode surfaces in the enantioselective electroreduction of the prochiral ketones 4-methyl benzophenone and 2,5-dimethyl benzophenone. One polymer exhibits a recognition ability in the doped state; the investigation for the undoped state is in progress. A second polymer does not show enantioselective properties either in the doped nor in the undoped state.

Benzophenone derivatives and related compounds as potent histamine H3-receptor antagonists and potential PET/SPECT ligands.

Abstract: Para-substituted aromatic ethers with benzophenone or related structural elements and a 3-(1H-imidazol-4-yl)propyloxy moiety were prepared by Mitsunobu-type ether synthesis or SNAr reaction. Most of the title compounds possess high antagonist potency in histamine H3-receptor assays in vitro as well as in vivo in mouse CNS following oral administration. After defining 4-(3-(1H-imidazol-4-yl)propyloxy)phenyl phenyl methanone as a new lead, structure-activity relationships were investigated for this new class of compounds. Substitution of the meta'-position of the benzophenone moiety with halogen atoms (e.g., iodine, fluorine) led to compounds with high antagonist potency in vitro as well as in vivo (Ki = 9.3 and 4.3 nM, ED50 = 0.7 and 0.47 mg/kg p.o., 18 and 12, respectively). A receptor profile of several functional in vitro assays for several biogenic amine receptors for the meta'-iodinated derivative demonstrated high selectivity toward the histamine H3 receptor.

A study of the photopolymerization kinetics of methyl methacrylate using novel benzophenone initiators

Abstract: A series of novel bifunctional photoinitiators with benzophenone moieties were synthesized. Characterization of these molecules was performed using IR, UV, 1H NMR, 13C NMR and mass spectroscopy. Photopolymerization of methyl methacrylate, a model acrylate-type monomer, was carried out with the bifunctional benzophenone molecules functioning as the photoinitiator and triethylamine as the co-initiator. The progress of the polymerization was followed by dilatometry. The resulting plots of monomer conversion with time were used to evaluate the initial rates of polymerization. The relative enhancement/lowering of the rates of polymerization, with respect to benzophenone as the model photoinitiator, are interpreted in terms of the structure, and the photophysics of the initiator evaluated by nanosecond laser flash photolysis. © 2001 Society of Chemical Industry

Complete assignment of the 1H and 13C NMR spectra of the tetraisoprenylated benzophenone 15-epiclusianone

Abstract: An NMR study of 15-epiclusianone, 1-benzoyl-6-hydroxy-14,14-dimethyl-3,5,15-tri(3-methyl-2-butenyl)-bicyclo[3.3.1]non-1-ene-4,6-dione (1), a novel tetraisoprenylated benzophenone isolated from pericarp of fruits of Rheedia gardneriana, is described. In addition to conventional 1D NMR techniques, 2D shift-correlated NMR experiments [1H × 1H-COSY, 1H × 13C-HMQC-1J(C,H), 1H × 13C-HMBC-nJ(C,H) (n = 2 and 3) and 1H × 1H-NOESY] were used for 1H and 13C chemical shift assignments of this natural product. The 1D 13C NMR spectrum of 1 in the solid state was also obtained. Copyright © 2001 John Wiley & Sons, Ltd.

Synthesis and structure–activity relationships of benzophenone hydrazone derivatives with insecticidal activity

Abstract: A broad range of benzophenone hydrazone derivatives was prepared and tested against selected chewing insect pests, allowing the analysis of structure-activity relationships. Good activity was found only when the aromatic rings were substituted at the 4-positions with an halogen atom and a triflate or perhaloalkoxy group. In contrast, a number of substituents on the hydrazone part led to active compounds, the best results being achieved with acyl-type substituents. The excellent laboratory and greenhouse activity of the best representatives was confirmed in semi-field trials against Spodoptera littoralis.

Deoxygenation of benzoic acid on metal oxides: 2. Formation of byproducts

Abstract: Benzene, benzophenone, toluene and benzylalcohol are byproducts in the selective deoxygenation of benzoic acid to benzaldehyde on ZnO and ZrO2. In this paper, the pathways to the byproducts are discussed and a complete overview of the reaction network is presented. Benzene and benzophenone are products of the decomposition of the strongly adsorbed benzoic acid at elevated temperature. Toluene is formed by the deoxygenation of benzaldehyde at oxygen vacancy sites. Direct hydrogenation of benzaldehyde yields benzylalcohol. Selectivity to byproducts is not only determined by the reaction temperature, but also by the degree of surface reduction and the difference in adsorption strength between reactant and product. At temperatures 95%). Higher temperatures induce decomposition of the benzoate layer into benzene and more importantly enhance the degree of reduction of the catalyst, which results in the formation of toluene from benzaldehyde.

Radical Pair Kinetics in the Hydrogen Abstraction of Benzophenone Derivatives in Micellar Solutions, Studied by Pulsed Microwave Irradiation

Abstract: The hydrogen abstraction reaction of benzophenones in micellar interiors was studied by the effect of a short, resonant microwave pulse on the recombination kinetics under magnetic fields of approx...

Photochemical properties of benzophenone adsorbed on Ti-Al binary oxides: The effects of the surface acidity

Abstract: Ti−Al binary oxides prepared by a coprecipitation method exhibit different chemical behaviors from those of physically mixed TiO2−Al2O3 oxides, and the dispersion of the TiO2 species in the Ti−Al binary oxides increases when the composition of Al of the starting materials is increased. When benzophenone is adsorbed on the Ti−Al binary oxides, the photochemical and photophysical properties of benzophenone are found to be greatly different from those of benzophenone adsorbed on porous silica glass such as Vycor glass. Namely, the phosphorescence properties of benzophenone adsorbed on Ti−Al binary oxides show the presence of the protonated form of benzophenone in addition to the benzophenone hydrogen-bonded to the surface OH groups. The characteristics of the surface properties, structures, and activities of these binary oxides are examined by monitoring the characteristics of the isomerization of cis-2-butene as a probe reaction. The phosphorescence properties of the protonated and hydrogen-bonded form of b...