Search results for "MOLECULE"
showing 10 items of 5162 documents
Coordination Driven Capture of Nicotine Inside a Mesoporous MOF.
2017
Metal organic frameworks (MOFs) are a wide class of crystalline porous polymers studied in many fields, ranging from catalysis to gas storage. In the past few years, MOFs have been studied for the encapsulation of organic or organometallic molecules and for the development of potential drug carriers. Here, we report on the study of two structurally-related mesoporous Cu-MOFs, namely PCN-6 and PCN-6′ (PCN stands for Porous Coordination Network), for nicotine trapping. Nicotine is a well-known alkaloid liquid molecule at room temperature, whose crystalline structure is still unknown. In this work, the loading process was monitored by electron ionization mass spectrometry by using a direct ins…
DFT study on the cycloreversion of thietane radical cations.
2011
The molecular mechanism of the cycloreversion (CR) of thietane radical cations has been analyzed in detail at the UB3LYP/6-31G* level of theory. Results have shown that the process takes place via a stepwise mechanism leading to alkenes and thiobenzophenone; alternatively, formal [4 + 2] cycloadducts are obtained. Thus, the CR of radical cations 1a, b(center dot+) is initiated by C2-C3 bond breaking, giving common intermediates INa,b. At this stage, two reaction pathways are feasible involving ion molecule complexes IMCa,b (i) or radical cations 4a,b(center dot+) (ii). Calculations support that 1a(center dot+) follows reaction pathway (leading to the formal [4 + 2] cycloadducts 5a). By cont…
Polycatenane systems from Co(II) and trans-1,2-bis(4-pyridyl)ethene (bpe). Synthesis and structure of Co(bpe)2(NCS)2·CH3OH, [Co(bpe)2(H2O)2](ClO4)2·2…
2001
Three new compounds of formulae Co(bpe)2(NCS)2·CH3OH, 1, [Co(bpe)2(H2O)2](ClO4)2·2CH3OH, 2 and [Co(bpe)2(H2O)2(CH3OH)2](ClO4)2·bpe·H2O, 3, [bpe = trans-1,2-bis(4-pyridyl)ethene] have been synthesised and characterised by single crystal X-ray diffraction. The metal environment in 1–3 is distorted octahedral. Compound 1 is a polycatenane. Its structure consists of parallel layers containing Co2+ ions linked by bpe ligands, the Co···Co distance through the bpe bridge being 13.65(3) A. Each metal ion, in a layer, defines the edges of a rhombus. Two thiocyanate groups trans-coordinated to the metal atoms are perpendicular to the sheets. Each sheet has an infinite number of perpendicular sheets …
Ca[Ag2(SCN)4]·2H2O
2004
Calcium tetrathiocyanatodiargentate(I) dihydrate, Ca[Ag(2)(SCN)(4)].2H(2)O, contains eight-membered Ag(4)S(4) rings bonded together through shared atoms to form layers parallel to (100). The thiocyanate groups link the layers to Ca-O chains running parallel to the c axis. The Ca atom is located on a twofold rotation axis parallel to b and is surrounded by four water molecules of crystallization and four thiocyanate N atoms in a distorted square antiprism.
The two-dimensional iron(ii)–thiocyanate–4,4′-bipyridine coordination network
2010
The crystal structures of eight solvates of {Fe(4,4′-bipyridine)2(NCS)2}n have been determined. All of them contain a layered iron–bipyridine–thiocyanate framework formed from approximately square infinite two-dimensional (4,4) iron–bipyridine grids, with the solvent molecules hosted between adjacent layers. All the structures contain the iron(II) centres in the high-spin electronic configuration, and magnetic susceptibility measurements on the toluene and nitrobenzene solvates do not reveal any spin-crossover behaviour.
Dicaesium silver zinc thiocyanate, Cs2[AgZn(SCN)5]
2001
The title compound, dicaesium(I)-μ-thiocyanato-κ2N:S-zinc(II)-tetra-μ-thiocyanato-κ2S:N-argentate(I), crystallizes in the orthorhombic space group Pmn21 and contains units of composition AgZn(SCN)3 lying on a mirror plane and bonded together through Cs+ ions and thiocyanate groups. The crystal studied contained equal numbers of inversion twins.
Syntheses, crystal structures and magnetic properties of copper(II) polynuclear and dinuclear compounds with 2,3-bis(2-pyridyl)pyrazine (dpp) and pse…
2001
Abstract The preparation, crystal structures and magnetic properties of four heteroleptic copper(II) complexes with 2,3-bis(2-pyridyl)pyrazine (dpp) and azide, cyanate or thiocyanate as ligands are reported, [Cu(dpp)(N3)2]n (1), [Cu(dpp)(NCO)2]n (2), [Cu(dpp)(NCS)2]2 (3) and [Cu(H2O)(dpp)(NCS)2]2·2H2O (4). Compounds 1 and 2 are isomorphous, triclinic, space group P1, and consist of mononuclear building blocks featuring copper atoms with close to square planar coordination geometries. The mononuclear units are, however, associated into chains through weak axial Cu–N bonds formed by end-on asymmetrically bridging azido/cyanato groups and by pyridyl nitrogen atoms. Taking these contacts into a…
Pseudohalide derivatives of manganese(II) and copper(II) complexes with mepirizole, a biologically active pyrimidyl-pyrazole ligand
1989
Abstract The synthesis and characterization of thiocyanate and azide derivatives of mepirizole(4-methoxy-2-(5-methoxy-3-methyl-pyrazol-1-yl)-6-methylpyrimidine, hereinafter L) with manganese(II) and copper(II) is reported. The compounds were characterized by IR, electronic and EPR spectra and analytical data. Spectroscopic results suggest the existence of dimeric neutral entities [L2Cu2(μ-X)2(X)2] (X = NCS or N3) with unsymmetrical end-to-end bridges and five-coordination geometry around the copper(II) ion. Magnetic susceptibility data show that in the azide derivative the copper atoms are antiferromagnetically coupled (J = −18 cm−1), but no magnetic exchange interaction could be detected i…
Discovery and validation of small-molecule heat-shock protein 90 inhibitors through multimodality molecular imaging in living subjects.
2012
Up-regulation of the folding machinery of the heat-shock protein 90 (Hsp90) chaperone protein is crucial for cancer progression. The two Hsp90 isoforms (α and β) play different roles in response to chemotherapy. To identify isoform-selective inhibitors of Hsp90(α/β)/cochaperone p23 interactions, we developed a dual-luciferase (Renilla and Firefly) reporter system for high-throughput screening (HTS) and monitoring the efficacy of Hsp90 inhibitors in cell culture and live mice. HTS of a 30,176 small-molecule chemical library in cell culture identified a compound, N -(5-methylisoxazol-3-yl)-2-[4-(thiophen-2-yl)-6-(trifluoromethyl)pyrimidin-2-ylthio]acetamide (CP9), that binds to Hsp90(α/β) an…
Pigment organization and energy transfer dynamics in isolated photosystem I (PSI) complexes from Arabidopsis thaliana depleted of the PSI-G, PSI-K, P…
2002
Abstract Green plant photosystem I (PSI) consists of at least 18 different protein subunits. The roles of some of these protein subunits are not well known, in particular those that do not occur in the well characterized PSI complexes from cyanobacteria. We investigated the spectroscopic properties and excited-state dynamics of isolated PSI-200 particles from wild-type and mutant Arabidopsis thaliana plants devoid of the PSI-G, PSI-K, PSI-L, or PSI-N subunit. Pigment analysis and a comparison of the 5K absorption spectra of the various particles suggests that the PSI-L and PSI-H subunits together bind approximately five chlorophyll a molecules with absorption maxima near 688 and 667nm, that…