(E)-3-(3,4-Dimeth­oxy­phen­yl)-1-(2-hy­droxy­phen­yl)prop-2-en-1-one

In the title compound, C17H16O4, the dihedral angle between the mean planes of the hy­droxy­phenyl and dimeth­oxy­phenyl rings is 5.9 (6)°. The mean plane of the prop-2-en-1-one group makes dihedral angles of 3.6 (0) and 2.6 (7)° with the hy­droxy­phenyl and dimeth­oxy­phenyl rings, respectively. An intra­molecular O—H⋯O hydrogen bond occurs. The crystal packing is stabilized by weak inter­molecular C—H⋯O contacts and π–π stacking inter­actions [centroid–centroid distance = 3.6571 (8) Å]

(2E)-1-(2-Bromo­phen­yl)-3-(4-chloro­phen­yl)prop-2-en-1-one

In the title compound, C15H10BrClO, the dihedral angle between the mean planes of the benzene rings in the ortho-bromo- and para-chloro-substituted rings is 70.5 (6)°. The dihedral angles between the mean plane of the prop-2-en-1-one group and the mean planes of the benzene rings in the 4-chloro­phenyl and 2-bromo­phenyl rings are 14.9 (3) and 63.3 (8)°, respectively. In the crystal, inversion dimers linked by pairs of weak C—H⋯O interactions are observed as well as aromatic π–π stacking inter­actions

4-(4-Chloro­phen­yl)-4-hy­droxy­piperidinium benzoate

In the title salt, C11H15ClNO+·C7H5O2 −, the dihedral angle between the mean planes of the chloro­phenyl ring of the cation and the benzene ring of the anion is 74.4 (1)°. In the cation, the six-membered piperazine ring adopts a chair conformation. The crystal packing is stabilized by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds, and weak inter­molecular C—H⋯O, C—H⋯Cl and C—H⋯π inter­actions

4-(4-Chloro­phen­yl)-4-hy­droxy­piperidinium 2-(2-phenyl­eth­yl)benzoate

In the title compound, C11H15ClNO+·C15H13O2 −, the piperidinium ring adopts a chair conformation. In the crystal, cations and anions are connected by inter­molecular O—H⋯O and N—H⋯O hydrogen bonds, forming two-dimensional networks parallel to the bc plane. Furthermore, the crystal structure is stabilized by weak C—H⋯π inter­actions

Fluorescence Manipulation by Gold Nanoparticles: From Complete Quenching to Extensive Enhancement

<p>Abstract</p> <p>Background</p> <p>When a fluorophore is placed in the vicinity of a metal nanoparticle possessing a strong plasmon field, its fluorescence emission may change extensively. Our study is to better understand this phenomenon and predict the extent of quenching and/or enhancement of fluorescence, to beneficially utilize it in molecular sensing/imaging.</p> <p>Results</p> <p>Plasmon field intensities on/around gold nanoparticles (GNPs) with various diameters were theoretically computed with respect to the distance from the GNP surface. The field intensity decreased rapidly with the distance from the surface and the rate of decrease was greater for the particle with a smaller diameter. Using the plasmon field strength obtained, the level of fluorescence alternation by the field was theoretically estimated. For experimental studies, 10 nm GNPs were coated with polymer layer(s) of known thicknesses. Cypate, a near infrared fluorophore, was placed on the outermost layer of the polymer coated GNPs, artificially separated from the GNP at known distances, and its fluorescence levels were observed. The fluorescence of Cypate on the particle surface was quenched almost completely and, at approximately 5 nm from the surface, it was enhanced ~17 times. The level decreased thereafter. Theoretically computed fluorescence levels of the Cypate placed at various distances from a 10 nm GNP were compared with the experimental data. The trend of the resulting fluorescence was similar. The experimental results, however, showed greater enhancement than the theoretical estimates, in general. The distance from the GNP surface that showed the maximum enhancement in the experiment was greater than the one theoretically predicted, probably due to the difference in the two systems.</p> <p>Conclusions</p> <p>Factors affecting the fluorescence of a fluorophore placed near a GNP are the GNP size, coating material on GNP, wavelengths of the incident light and emitted light and intrinsic quantum yield of the fluorophore. Experimentally, we were able to quench and enhance the fluorescence of Cypate, by changing the distance between the fluorophore and GNP. This ability of artificially controlling fluorescence can be beneficially used in developing contrast agents for highly sensitive and specific optical sensing and imaging.</p

1,3-Bis(biphenyl-4-yl)-2,2-dibromo-3-oxopropyl acetate

In the title compound, C29H22Br2O3, the dihedral angles between the mean planes of the benzene rings within each biphenyl group are 26.7 (8) and 30.9 (8)°. The mean planes of the terminal and inner benzene rings of the biphenyl groups bonded through a propan-1-one group in the V-shaped mol­ecule are oriented at angles of 66.1 (7) and 60.0 (8)°, respectively. The two Br atoms are opposite the propen-1-one group. Weak inter­molecular C—H⋯O and C—H⋯π inter­actions are observed in the crystal structure

(2E)-3-[4-(Dimethyl­amino)­phen­yl]-1-(4-fluoro­phen­yl)prop-2-en-1-one

The mean planes of the two benzene rings in the title compound, C17H16FNO, are twisted slightly, making a dihedral angle of 7.8 (1)°. The prop-2-en-1-one group is also twisted slightly with a C—C—C—O torsion angle of −11.6 (3)°. In the crystal, weak inter­molecular C—H⋯O inter­actions link pairs of mol­ecules, forming centrosymmetric dimers

Imatinibium dipicrate

In the crystal structure of imatinibium dipicrate [systematic name: 1-methyl-4-(4-{4-methyl-3-[4-(3-pyrid­yl)pyrimidin-2-yl­amino]­anilinocarbon­yl}benz­yl)piperazine-1,4-diium dipicrate], C29H33N7O2+·2C6H2N3O7 −, the imatinibium cation is proton­ated at both of the pyrimidine N atoms. Each of the two picrate anions inter­acts with the diprotonated cation through bifurcated N—H⋯O hydrogen bonds forming R 1 2(6) ring motifs. Also, an R 2 2(24) graph set is formed between the benzamidium –NH– group and the 4-pyridyl N atom inter­acting through N—H⋯N hydrogen-bond inter­actions. Additional weak C—H⋯Cg π-ring and π–π inter­molecular inter­actions are observed which also influence crystal packing

4-(4-Chloro­phen­yl)-4-hy­droxy­piperidinium maleate maleic acid solvate

In the cation of the title compound, C11H15ClNO+·C4H3O4 −·C4H4O4, the dihedral angle between the mean planes of the chlorine-substituted aromatic ring and the 4-hy­droxy­piperidinium ring (C–C–C–C–C–N) is 61.9 (8)°. Intra­molecular O—H⋯O and inter­molecular O—H⋯O and N—H⋯O hydrogen bonding, as well as weak π-stacking inter­actions [centroid–centroid distance = 3.646 (5) Å] help to establish the packing