Photophysical properties of diphenyl-2,3-dihydroxychlorin and diphenylchlorin

The photophysical properties of 5,15-diphenyl-2,3-dihydroxychlorin (DPCOH) and 5,15-diphenyl-chlorin (DPC) in organic solution were studied. Absorption, fluorescence, triplet state and photobleaching experiments are reported. The ground states of both compounds show strong absorbance in red region (lambda = 638 nm, epsilon = 35,000 M(-1) cm(-1) and lambda = 645 nm, epsilon = 42,000 M(-1) cm(-1), respectively) and the singlet excited states show low fluorescence quantum yields of 0.0802 and 0.150 in benzene and the lifetimes are 7.38 and 10.18 ns, respectively. Absorption spectra of the triplet states were also measured and they have nearly the same triplet state lifetimes of 53 micros (DPCOH) and 50 micros (DPC). The triplet quantum yields are 0.82 and 0.75, respectively. The data of photobleaching quantum yields show that the presence of oxygen does not significantly affect the photobleaching. All the results demonstrate that both diphenylchlorines are good candidates for second-generation photosensitizer in photodynamic therapy.     

Enthalpies of sublimation and fusion of monophenylurea and diphenyl-1,3 urea

The sublimation enthalpies of monophenylurea (MPhU) and diphenyl-1,3 urea (1,3-DPhU) have been derived from the dependence of their vapour pressures on temperature, as measured by the torsion-effusion method. Values obtained are: 136 kj mol⁻¹ for MPhU and 152 kJ mol⁻¹ for 1,3-DPhU, where the estimated errors are comprised within 6 kJ mol⁻¹Enthalpies and temperatures of fusion have been measured by differential scanning calorimetry, leading to 23.7 kJ mol⁻¹ and 420.6 K for MPhU, and 34.6 kJ mol⁻¹ and 512 K for 1,3-DPhU. Poor reproducibility of results for 1,3-DPhU seems be due to the beginning of decomposition. No solid-to-solid transitions have been revealed from r.t. to fusion for both compounds.     

Synthesis of some novel tetraimidazolium salts derived from diphenyl- and dimethylglycolurils

Several new tetrabromo compounds based on diphenyl- and dimethylglycolurils were synthesized. Sequential treatment of these compounds with imidazole, methyl iodide, and sodium tetrafluoroborate gave their corresponding tetra imidazolium salts. Some of these compounds because of their low melting points can be registered as a potential and new class of ionic liquids. Correspondence: Mehdi Bakavoli, Department of Chemistry, School of Sciences, Ferdowsi University, Mashhad 91375-1436, Iran.     

Characterization of a new non-centrosymmetric polymorph of diphenyl-1,3,4-oxadiazole

Diphenyl-1,3,4-oxadiazole (DPO) crystallization experiments from solutions clearly reveal the polymorphism of the substance. Besides the formerly known centrosymmetric monoclinic structure with space group P2₁/c (DPO I) a new monoclinic structure with the non-centrosymmetric space group Cc is found (DPO II): a=2.4134(4) nm, b=2.4099(3)  nm, c=1.2879(2) nm, β=110.048(3)°, and V=7.0363(17) nm³. The asymmetric unit contains six independent molecules in a complex packing motif. A re-determination of the crystal structure of DPO I at room temperature gives lattice parameters a=0.51885(6) nm, b=1.8078(2) nm, c=1.21435(14) nm, β=93.193(3)°, and V=1.1373(2) nm³. X-ray measurements at 363 K show a significant increase of the unit cell volume by 1.6%. Differences between both structures concerning morphology and characteristic Raman bands are outlined in detail. DSC investigations show an irreversible transition from DPO I to DPO II at 97 °C. DPO II does not show any transition in the temperature range up to the melting point at 141 °C. The non-centrosymmetric DPO II structure shows triboluminescence.     

A novel synthesis of 4,6-dimethyl- and diphenyl-2,5-dihydro-1,3,5,2-triazaphosphorines

The synthesis of 2,5-dihydro-1,3,5,2-triazaphosphorines via the intramolecular cyclization of N,N'-phos-phinylacetamidines or benzamidines is described. These derivatives represent the sole examples of 4,6-dialkyl or diaryl substitutions of this ring system.     

Computationally identified novel diphenyl- and phenylpyridine androgen receptor antagonist structures

We have identified and profiled a set of androgen receptor (AR) binding compounds representing two nonsteroidal scaffolds from a public chemical database supplied by Asinex with virtual screening procedure incorporating our recently published 3D QSAR model of AR ligands. The diphenyl- and phenylpyridine-based compounds act as antagonists in wild-type AR in CV1 cells and also retain this antagonistic character in CV1 cells expressing T877A mutant receptor. This mutation is frequently associated with prostate cancer. Two of the compounds repress the androgen-dependent cell growth of LNCaP prostate cancer cells expressing the T877A AR mutant. Molecular modeling of the observed in vitro antagonism with induced fit docking suggests that W741 and M895 could be mechanistically involved in the initiation of the antagonism. The results indicate finding of nonsteroidal AR antagonist compounds from a public chemical database with computational methods. Compounds could serve as a novel platform to develop more potent AR antagonists with inhibitory activity in both wild-type and T877A mutant AR.     

Cr,Co, and Mn arene π-complexes based on diphenyl- and triphenylmethane

The interaction of Ph₂CH₂ and Ph₃CH with Cr(CO)₆, Co₂(CO)₈, and Mn(CO)₅BF₄ leads to mononuclear LCr(CO)₃, LCo₄(CO)₉, and [LMn(CO)₃]BF₄ π-arene complexes. Similarly, LCr(CO)₃Co₄(CO)₉ and [LCr(CO)₃Mn(CO)₃]BF₄ heteroaromatic derivatives are obtained from LCr(CO)₃ complexes, whereas LCo₄(CO)₉ complexes afford L[Co₄(CO)₉]₂ bicluster derivatives. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1809–1812, October, 1993.     

The extraction of trace amounts of gold from different aqueous mineral acid solutions by diphenyl-2-pyridylmethane dissolved in chloroform

Diphenyl-2-pyridylmethane, a high molecular weight substituted pyridine has been examined and found to be a useful solvent extraction reagent. Its behaviour is similar to amines in that it forms salts with mineral acids. The acid ionization constant (pK_BH ⁺) determined spectrophotometrically has a value of 4.41±0.06 at 25 °C. A study of the partition behaviour of trace amounts of gold between mineral acid solutions and 0.1M diphenyl-2-pyridylmethane dissolved in chloroform indicates that the metal can be quantitatively extracted from dilute mineral acid solutions and also from concentrated hydrochloric acid media in a single extraction. Attempts have been made to gain an understanding of factors affecting the extraction of gold. Common anions have little effect on extraction in concentrations upto 1M. Separation factors of a number of metal ions relative to gold are reported for three mineral acid systems; and gold has been estimated in some synthetic samples using neutron activation technique by prior extraction with 0.1M solution of diphenyl-2-pyridylmethane dissolved in chloroform.     

The fluorescence of scorpions and cataractogenesis.

BACKGROUND: Protein cross-linking and fluorescence are widely recognized markers of oxidative aging in human proteins. Oxidative protein aging is a combinatorial process in which diversity arises from the heterogeneity of the targets and is amplified by the nonselective nature of the reactants. The cross-links themselves defy analysis because they are generally embedded in a covalent matrix. Arthropods rely upon oxidative cross-linking in the hardening of the cuticle - a process known as sclerotization. Among arthropods, scorpions are noteworthy in that the process of sclerotization is accompanied by the buildup of strong visible fluorescence. To date, the nature of the fluorescent species has remained a mystery. RESULTS: We have identified one of the soluble fluorescent components of the scorpions Centuroides vittatus and Pandinus imperator as beta-carboline - a tryptophan derivative that has previously been identified by hydrolysis and oxidation of lens protein. We have also shown that beta-carboline-3-carboxylic acid is released from both scorpion exuvia (the shed cuticle) and human cataracts upon hydrolysis, suggesting that the protein-bound beta-carboline and free beta-carboline have common chemical origins. CONCLUSIONS: Cataractogenesis and cuticular sclerotization are disparate oxidative processes - the former is collateral and the latter is constitutive. The common formation of beta-carbolines shows that similar patterns of reactivity are operative. These fundamental mechanisms provide predictive insight into the consequences of human protein aging.     

The fluorescence properties of luteolines

The fluorescence properties of luteoline and its possible methyl ethers (a representative class of naturally occurring flavonoids) were investigated, together with the effect of diagnostic shift reagents such as sulfuric acid, aluminium trichloride, and borax. The results demonstrate that fluorimetry is a suitable tool for the identification and structure elucidation of minute samples of flavones, in particular if combined with absorption spectrometry. ThepK _a values of all trimethylethers were determined for the ground and first excited singlet states and related to the effects of basic reagents.

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Die Fluoreszenzeigenschaften der Luteoline

Zusammenfassung Es wurden die Fluoreszenzeigenschaften der Luteoline (einer repräsentativen Klasse von natürlich vorkommenden Flavonoiden) sowie der Effekt diagnostischer Verschiebungsreagentien wie z. B. Schwefelsäure, Aluminiumtrichlorid und Borax untersucht. Die Ergebnisse zeigen, daß die Fluorimetrie eine geeignete Methode zur Identifikation und Strukturaufklärung auch geringster Probenmengen sein kann, besonders in Kombination mit Absorptionsmessungen. DiepK _s -Werte aller möglichen Trimethylether wurden für Grund- und ersten angeregten Zustand bestimmt und zu den Effekten der basischen Reagentien in Bezug gebracht.

     

Preconcentration and separation of silver from neutron poisons and rare earths using diphenyl-2-pyridylmethane as an extractant

The extraction of silver from aqueous thiocyanate-perchlorate solutions using diphenyl-2-pyridylmethane (DPPM) in benzene has been investigated. The variables such as concentrations of perchloric acid, thiocyanate and DPPM influencing the extraction have been optimized. Maximum extraction has been achieved from 0.01 M perchloric acid solution containing 0.01 M potassium thiocyanate in 0.075 M DPPM in benzene. The extraction was found to be independent of silver concentration in the range from 10^–4–10^–6 M. The influence of several anions on the extraction was examined; only thiosulphate interfered seriously and reduced the extraction below 1%. Thus 0.1M potassium thiosulphate was found to back-extract silver quantitatively in one step. Under selected optimal conditions, very small extraction (<1%) was observed for trivalent Gd, Dy, Ho, Tm, Yb, Lu; Cs(I) and Cd(II) and separation factors for these elements were better than 10³. Only Sn(IV) exhibited quantitative extraction (>99%). This extraction procedure can be used for the preconcentration of silver and tin or their separation from rare earths mentioned above.     

The preparation and fluorescence properties of europium nanoparticles

A new structured metallic nanomaterial of europium nanoparticle was prepared using tannic acid as the reductive agent,and nanoeuropium protein conjugates were synthesized by the method of lipoic acid modification on the surface of nanoparticle,which opens a new field of application of lanthanides in nanotechniques.Their properties were also characterized by UV-vis absorption spectroscopy,transmission electron microscopy (TEM),and fluorescence spectroscopy.The europium nanoparticle and its protein conjugates solution were stable and water-soluble.The fluorescence intensity of the composite europium nanoparticles was significantly increased in the presence of trace protein,and was linear proportional to the concentration of proteins under optimum conditions.According to this,a fluorimetric method for the determination of protein was developed in this paper.     

乌拉地尔的荧光光谱研究及测定

建立了一种测定制剂中乌拉地尔的荧光分光光度法。用荧光分光光度法研究了不同溶剂和pH下乌拉地尔的荧光光谱性质。在pH5.0缓冲溶液中,在3.30×10-7～1.65×10-5mol/L浓度范围内,285nm紫外光的激发下,乌拉地尔在365nm处的荧光强度与浓度呈良好的线性关系。线性相关系数为0 9975,测定片剂和针剂的平均回收率分别为99.0%和99.8%,相对标准偏差小于3 0%。     

Azo anions in synthesis : Use of trityl- and diphenyl-4-pyridylmethylhydrazones for reductive C-C bond formation

The lithium salts of trityl- and diphenyl-4-pyridylmethyl-hydrazones of both aldehydes and ketones react with electrophiles (alkyl halides, aldehydes, ketones, crotonates) at low temperature to form C-trapped azo compounds ; these Intermediates decompose homolytically with loss of nitrogen below room temperature and can be diverted in a synthetically useful way to alkanes, alkenes, alcohols or saturated esters.     

The total fluorescence of human urine

The total fluorescence of human urine was measured at various excitation and emission wavelengths and is presented in 3-dimensional form. Despite the complexity of the composition of urine, 3–5 distinct fluorescence maxima can be observed. Effects of pH were studied and tentative assignments as to the species responsible for the peaks were made. Most likely, however, the peaks observed do not result from a single fluorescent urinary metabolite, but rather from several species having similar spectral properties and being present in comparable concentrations.     

The fluorescence of biliverdin dimethyl ester

Freshly prepared solutions of biliverdin dimethyl ester ( 2 ) in ethanol showed fluorescence maxima at 710 and 770 nm [Φ_F = 1.1. 10^?4 (room temperature) and 5.0 10^?4 (77 K)]. The maxima of monoprotonated 2 at 77 K were shifted to 725 and 806 nm and the quantum yield was increased to 2.6. 10^?2. This acid effect was reversible by neutralization with base. When a neutral solution was kept standing in the dark at room temperature, or when an acidic solution was neutralized by base, an additional fluorescence maximum at 500 nm with a mirror image excitation spectrum with λ_max = 470 nm developed, which disappeared on addition of acid and which is attributed to a chemical change of 2 .     

The fluorescence lifetime of tetracene vapour

The fluorescence lifetimes of tetracene vapour as a function of excess vibrational energy in the first excited singlet state have been measured under collision free conditions. A very marked decrease in lifetime with increasing energy has been observed. We attribute this behaviour to enhanced internal conversion from vibrationally excited levels.