In the present work, wetting behavior of an ionic liquid droplet containing 1-methyl-3-butylimidazolium and fluorophosphate on the titanium dioxide (110) surface is studied using a molecular dynamics simulation. On the basis of the anisotropic characteristics of titanium dioxide surface, contact angles were calculated along different directions which are in agreement with experimental data. The obtained results show that a cation-rich layer is spread on the surface. Imidazolium rings of cations of ionic liquid are parallel to the titanium dioxide surface, but their orientation in the upper layer is almost vertical. Such positioning leads to the butyl-ring substituents locating at the top of the first layer to create a relatively empty space of cations while resulting in an anion-rich region. The cations and anions form a spherical shape on top of the first layer. Cross-sectional analysis of the ionic liquid reveals the circular configuration of cations and anions within the nanodroplet. The above observations signify the wetting behavior of the ionic liquid at the adjacent layer of surface and its nonwetting behavior at long distances from the surface which results in the formation of a spherical cap and is the direct consequence of the different behavior of cations and anions on the titanium dioxide surface.
A wide range of ruthenium-based
coordination compounds have been
reported to possess potential as metallodrugs with anticancer or antimetastatic
activity. In this work, we synthesized a set of new zwitterionic Ru(III)
compounds bearing ligands derived from N-alkyl (R)
systems based on pyridine, 4,4′-bipyridine, or 1,4-diazabicyclo[2.2.2]octane
(DABCO). The effects of the ligand(s) and their environment on the
coordination stability have been investigated. Whereas the [DABCO-R]+ ligand is shown to be easily split out of a negative [RuCl4]− core, positively charged R-pyridine and
R-bipyridine ligands form somewhat more stable Ru(III) complexes and
can be used as supramolecular anchors for binding with macrocycles.
Therefore, supramolecular host–guest assemblies between the
stable zwitterionic Ru(III) guests and the cucurbit[7]uril host were
investigated and characterized in detail by using NMR spectroscopy
and single-crystal X-ray diffraction. Paramagnetic 1H NMR
experiments supplemented by relativistic DFT calculations of the structure
and hyperfine NMR shifts were performed to determine the host–guest
binding modes in solution. In contrast to the intramolecular hyperfine
shifts, dominated by the through-bond Fermi-contact mechanism, supramolecular
hyperfine shifts were shown to depend on the “through-space”
spin–dipole contributions with structural trends being satisfactorily
reproduced by a simple point-dipole approximation.
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