Benzophenone-Initiated Photoisomerization of the Norbornadiene Group in a Benzophenone−Steroid−Norbornadiene System via Long-Distance Intramolecular Triplet Energy Transfer

Bichromophoric compound 3β-((2-(methoxycarbonyl)bicyclo[2.2.1]hepta-2,5-diene-3-yl)carboxy)androst-5-en-17β-yl benzophenone-4-carboxylate (NBD-S-BP) was synthesized, and its photochemistry was examined. The phosphorescence of the benzophenone (BP, donor) chromophore is efficiently quenched by the remote norbornadiene (NBD, acceptor) group. Time-resolved spectroscopic measurements indicate that the lifetime of the triplet state of the BP chromophore is shortened by the NBD group. Selective excitation of the BP chromophore results in isomerization of the NBD group to quadricyclane. All these observations suggest that a long-distance intramolecular triplet energy transfer occurs in the NBD-S-BP molecule. The efficiency and rate constant for this triplet energy transfer were determined to be ca. 22% and 1.5 × 105 s-1, respectively, by steady-state photolysis and laser flash photolysis. This long-distance intramolecular triplet energy transfer is proposed to proceed via a through-bond exchange mechanism

Synthesis, characterization and anti-lung cancer activity of two transition metal coordination polymers based on the imidazole-containing ligands

This work presents the synthesis and characterization of two new transition metal coordination polymers [Co(tib)2](NO3)2 (1, tib = 1,3,5-tris(1-imidazolyl)benzene) and [Cd4(bib)5(HCOO)8](DMF)3 (2, bib = 4,4′-bisimidazolylbiphenyl) have been successfully prepared by using two imidazole-containing ligands with different geometers. All structures have been fully elucidated by single-crystal X-ray diffraction along with the elemental analysis. The structural solution and refinement results based on the crystal data collected at room temperature reveal that complex 1 shows a 2D layered structure with a binodal (3,6)-connected kgd topological net, while complex 2 also demonstrates a 2D framework but reflecting a 4-connected sql topological net. Furthermore, the anti-lung cancer activity of the two complexes has been studied via the Cell Counting Kit-8 (CCK-8) assay along with the corresponding action mechanism.</p

Enhanced Stereoselectivity in Photoelectrocyclization of Tropolone Ethers via Confinement in Chiral Inductor-Modified Lyotropic Liquid Crystals

Photochemistry of tropolone methyl ether (1) and optically pure (S)-tropolone-2-methylbutyl ether (4) has been examined in lyotropic liquid crystals (LCs) in the presence of a chiral inductor. LCs significantly enhance the influence of chiral inductors during the photoelectrocyclization of the tropolone ethers. Chiral inductors that lead to 1:1 mixtures of enantiomers or diastereomers in solution give products in up to 40% enantiomeric excess for 1 and 35% diastereomeric excess for 4 in LCs

Intramolecular Long-Distance Electron Transfer and Triplet Energy Transfer. Photophysical and Photochemical Studies on a Norbornadiene−Steroid−Benzidine System

A bichromophoric compound 3β-((2-(methoxycarbonyl)bicyclo-[2.2.1]hepta-2,5-diene-3-yl)carboxy)androst-5-en-17β-yl-2,2‘,6,6‘,N,N,N‘,N‘ heptamethylbenzidine (N−S−B) was synthesized, and its photochemistry was examined by using both steady-state and time-resolved techniques. Intramolecular electron transfer from the singlet excited state of benzidine to the norbornadiene chromophore in N−S−B occurs with efficiency (ΦET ) of ca. 12% and rate constant (kSET) of ca. 1.1 × 107 s-1, resulting in the singlet radical ion pair 1(N•-−S−B•+) followed by intersystem crossing to the triplet state 3(N•-−S−B•+). Recombination of 3(N•-−S−B•+) yields triplet norbornadiene group. The efficiency (φRIPISC·φRIPRC) of the formation of the triplet norbornadiene from the radical ion pair is ca. 17%. The singlet excited state of benzidine group in N−S−B undergoes intersystem crossing to its triplet state with efficiency (ΦISC) of ca. 56%. Intramolecular triplet energy transfer leading to the formation of the triplet norbornadiene chromophore is efficient (φTT = ca. 65%, kTT = ca. 5.2 × 105 s-1). Selective excitation of the benzidine chromophore results in isomerization of the norbornadiene group to quadricyclane. This isomerization proceeds either via intramolecular triplet sensitization or radical-ion pair recombination mechanism. The long-distance intramolecular triplet energy transfer and singlet electron transfer are proposed to proceed via a through-bond mechanism

The ACF and PACF graphs of stabilized tuberculosis morbidity series.

<p>ACF = autocorrelation function, PACF = partial autocorrelation function. Based on the ACF, we determine the possible values of <i>q</i> (<i>q</i> = 1, 2 or 3) and <i>Q</i>(<i>Q</i> = 1) of ARIMA (<i>p</i>, <i>d</i>, <i>q</i>) (<i>P</i>, <i>D</i>, <i>Q</i>) ₁₂, and based on PACF, we determine the possible values of <i>p</i> (<i>p</i> = 1, 2 or 3) and <i>P</i> (<i>P</i> = 1) of ARIMA (<i>p</i>, <i>d</i>, <i>q</i>) (<i>P</i>, <i>D</i>, <i>Q</i>)₁₂.</p

A New Unusual Natural Pigment from <i>Selaginella </i><i>sinensis</i> and Its Noticeable Physicochemical Properties

A new unusual pigment with a novel carbon framework named selaginellin (1) was isolated from the acetone extract of Selaginella sinensis, and its methoxy derivative (1a) was synthesized. Both selaginellin 1 and 1a are racemic compounds. The structure of selaginellin 1 was established as (R,S)-4-[(4‘-hydroxy-4-(hydroxymethyl)-3-((4-hydroxyphenyl)ethynyl)biphenyl-2-yl)(4-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one and 1a as (R,S)-4-[(4‘-methoxy-4-(methoxymethyl)-3-((4-methoxyphenyl)ethynyl)biphenyl-2-yl)(4-methoxyphenyl)methylene]-2,5-cyclohexadien-1-one by the analysis of one- and two-dimensional NMR data, HR-ESIMS, EI-MS, IR, UV, CD, and single-crystal X-ray experiments, and the mechanism of their color change according to different pH values and fluorescent properties was studied

Core reactions of fatty acid biosynthesis reconstructed based on the <i>de novo</i> assembly and annotation of <i>C. oleifera</i> transcriptome.

<p>During fatty acid biosynthesis, two-carbon units are added for each cycle reaction, and the four-step cycle is repeated until the appropriate chain-length is reached. Finally, different types of fatty acids are synthesized. The identified enzymes are shown in boxes and abbreviated as below: ACC, acetyl-CoA carboxylase (EC: 6.4.1.2); MAT, malonyl-CoA ACP transacylase (EC: 2.3.1.39); KAS, beta-ketoacyl-ACP synthase (KAS I, EC: 2.3.1.41; KASII, EC: 2.3.1.179; KAS III, EC: 2.3.1.180); KAR, beta-ketoacyl-ACP reductase (EC: 1.1.1.100); HAD, beta-hydroxyacyl-ACP dehydrase (EC: 4.2.1.-); EAR, enoyl-ACP reductase (EC: 1.3.1.9); AAD, acyl-ACP desaturase (EC: 1.14.19.2); OAH, oleoyl-ACP hydrolase (EC: 3.1.2.14); FatA, Acyl-ACP thioesterase A (EC: 3.1.2.-); Δ¹²D, Δ¹²(ω⁶)-desaturase (EC: 1.4.19.6). The numbers-in-circles indicates the repeat time of the condensation reaction.</p

Photosensitized Oxidative Deprotection of Oximes to Their Corresponding Carbonyl Compounds by Platinum(II) Terpyridyl Acetylide Complex

Platinum(II) terpyridyl acetylide complex (1) photosensitizes the oxidation of aldoximes 2−4, aliphatic acyclic and cyclic ketoximes 5−7, and aromatic ketoximes 8−10 into their corresponding carbonyl compounds with good to excellent yields in acetonitrile solution. This deprotection of oximes proceeds via singlet oxygen (1O2) mechanism. The photosensitizer can be easily separated from the product and unreacted starting material by extraction with ethyl acetate and reused for photooxidation without loss of 1O2-generation capacity

A New Unusual Natural Pigment from <i>Selaginella </i><i>sinensis</i> and Its Noticeable Physicochemical Properties

A new unusual pigment with a novel carbon framework named selaginellin (1) was isolated from the acetone extract of Selaginella sinensis, and its methoxy derivative (1a) was synthesized. Both selaginellin 1 and 1a are racemic compounds. The structure of selaginellin 1 was established as (R,S)-4-[(4‘-hydroxy-4-(hydroxymethyl)-3-((4-hydroxyphenyl)ethynyl)biphenyl-2-yl)(4-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one and 1a as (R,S)-4-[(4‘-methoxy-4-(methoxymethyl)-3-((4-methoxyphenyl)ethynyl)biphenyl-2-yl)(4-methoxyphenyl)methylene]-2,5-cyclohexadien-1-one by the analysis of one- and two-dimensional NMR data, HR-ESIMS, EI-MS, IR, UV, CD, and single-crystal X-ray experiments, and the mechanism of their color change according to different pH values and fluorescent properties was studied

Tuberculosis morbidity from January 2004 to June 2014 in Xinjiang.

<p>The Data was obtained from the website of Bureau of Health, Xinjiang Uyghur Autonomous Region, China. The tuberculosis morbidity has roughly seasonal fluctuations and slightly rising trend.</p