Search results for "ta116"
showing 10 items of 942 documents
CoIILnIII dinuclear complexes (LnIII = Gd, Tb, Dy, Ho and Er) as platforms for 1,5-dicyanamide-bridged tetranuclear CoII2LnIII2 complexes: A magneto-…
2012
Five acetate-diphenoxo triply-bridged Co-II-Ln(III) complexes (Ln(I) = Gd, Tb, Dy, Ho, Er) of formula [Co(mu-L)(mu-Ac)Ln(NO3)(2)] and two diphenoxo doubly-bridged Co-II-Ln(III) complexes (Ln(III) = Gd, Tb) of formula [Co(H2O)(mu-L)Ln(NO3)(3)]center dot S (S = H2O or MeOH), were prepared in one pot reaction from the compartmental ligand N,N',N ''-trimethyl-N,N ''-bis(2-hydroxy3-methoxy-5-methylbenzyl)diethylene triamine (H2L). The diphenoxo doubly-bridged Co-II-Ln(III) complexes were used as platforms to obtain 1,5-dicyanamide-bridged tetranuclear Co-II-Ln(III) complexes (Ln(III) = Gd, Tb, Dy, Ho, Er). All exhibit ferromagnetic interactions between the Co-II and Ln(III) ions and in the case …
Electrocrystallization of Monolayer-Protected Gold Clusters : Opening the Door to Quality, Quantity, and New Structures
2017
Thiolate-protected metal clusters are materials of ever-growing importance in fundamental and applied research. Knowledge of their single-crystal X-ray structures has been instrumental to enable advanced molecular understanding of their intriguing properties. So far, however, a general, reliable, chemically clean approach to prepare single crystals suitable for accurate crystallographic analysis was missing. Here we show that single crystals of thiolate-protected clusters can be grown in large quantity and very high quality by electrocrystallization. This method relies on the fact that charged clusters display a higher solubility in polar solvents than their neutral counterparts. Nucleation…
Orbiting Orbitals: Visualization of Vi-Bronic Motion at a Conical Intersection
2013
The Jahn-Teller (JT) active unpaired electron of single metalloporphyrin radical anions is imaged through scanning tunneling microscopy. It is demonstrated that the electron is delocalized over the porphyrin macrocycle and its topographic image is determined by vibronic motion: the orbital of the electron adiabatically follows the zero-point pseudorotation of skeletal deformations. Transformation of the polar graphs of the observed images allows visualization of the adiabatic vibrational density to which the electron is coupled. The vibronic potential at the conical intersection is visualized and the half-integer angular momentum characteristic of the Berry phase is revealed in the radial f…
Cooperatively Enhanced Ion Pair Binding with a Hybrid Receptor
2015
A simple 18-crown-6-based bis-urea receptor R(1) was synthesized in three steps from a commercial starting material. The receptor's behavior toward anions, cations, and ion pairs was studied in solution with (1)H NMR, in solid state with single-crystal X-ray diffraction, and in gas phase with mass spectrometry. In 4:1 CDCl3/dimethyl sulfoxide solution the receptor's binding preference of halide anions is I(-) < Br(-) < Cl(-) following the trend of the hydrogen-bonding acceptor ability of the anions. The receptor shows a remarkable positive cooperativity toward halide anions Cl(-), Br(-), and I(-) when complexed with Na(+), K(+), or Rb(+). The solid-state binding modes of R(1) with alkali an…
The effect of temperature on the internal dynamics of dansylated POPAM dendrimers
2011
The internal and rotational dynamics of the dansylated poly(propylene amine) dendrimers (POPAM) have been studied by time correlated single photon counting (TCSPC) and molecular dynamics (MD) simulations. The hydrodynamic volumes of the dendrimer generations from G1 to G4 were estimated by fluorescence anisotropy data. Experiments and simulations suggest that the volume and the shape of the dendrimers are temperature dependent. At low temperatures the dendrimer structure becomes more spacious and rigid and back-folding of the individual branches is slowed down. For the G3 and G4 generations the temperature effects are much stronger than for the smaller G1 and G2 generations, where back-fold…
Dimeric resorcinarene salt capsules with very tight encapsulation of anions and guest molecules
2015
Crystallization of N-cyclohexyl ammonium resorcinarene triflate from methanol results in a dimeric capsule capable of trapping two triflate anions and two methanol molecules within a 341 A3 cavity while with 1,4-dioxane as a guest it forms a new larger dimeric capsule with volume of 679 A3 encapsulating four 1,4-dioxane and four water molecules, resulting in packing coefficients of 0.75 and 0.67, respectively.
Raman spectroscopy of acetic acid monomer and dimers isolated in solid argon
2011
Acetic acid (AA) monomer and its dimers were studied by means of Raman spectroscopy combined with the matrix isolation technique. All fundamental bands of CH3COOH monomer were identified, including the CH3 torsional mode. Additionally, three overtone or combination modes were observed as a result of their enhanced intensities by Fermi resonance (FR). Twenty bands of the cyclic dimer (C2h) were identified and assigned, among which appear all intermolecular modes. Bands due to two different higher energy forms of the dimer were also identified. The experimental assignments are supported by ab initio calculations. Copyright © 2011 John Wiley & Sons, Ltd.
Binding Modes of Nonspherical Anions to N-Alkylammonium Resorcinarenes in the Solid State
2012
A series of hydrogen bond stabilized N-alkylammonium resorcinarene salts with nitrate, triflate, and picrate as the counteranions were synthesized and characterized with 1H NMR and electrospray ionization (ESI) mass spectrometry. Together with electrostatic interactions, the binding of the anions with several hydrogen bond donor sites proceeds through a complex array of intra- and intermolecular hydrogen bonds, evidenced by single crystal X-ray diffraction analysis. These N-alkyl ammonium resorcinarenes bind the larger nonspherical anions into deformed cavitand-like structures and enforce a transformation of the resorcinarene conformation from almost symmetrical to extremely distorted.
Metal-free regioselective C–C bond cleavage in 1,3,5-triazine derivatives of β-diketones
2014
Metal-free regioselective activation of a carbon–carbon bond in 1,3,5-triazine derivatives of β-diketones is easily achieved, in the absence of a catalyst, with the assistance of intramolecular hydrogen bonding.
A Halogen-Bonded Dimeric Resorcinarene Capsule.
2015
Iodine (I2) acts as a bifunctional halogen-bond donor connecting two macrocyclic molecules of the bowl-shaped halogen-bond acceptor, N-cyclohexyl ammonium resorcinarene chloride 1, to form the dimeric capsule [(1,4-dioxane)3@1(2)(I2)2]. The dimeric capsule is constructed solely through halogen bonds and has a single cavity (V=511 Å(3)) large enough to encapsulate three 1,4-dioxane guest molecules.