Benzoylecgonine [HRP]

Tetraureido-dihomooxacalix[4]arenes (tert-butyl 4a and phenyl 4b) were synthesised and obtained in a partial cone conformation in solution and in the solid state, as confirmed by NMR and X-ray diffraction studies. Their complexation ability towards halides, pseudo-halides and oxoanions was assessed by H-1 NMR and UV/Vis titrations. Structural and energetic insights of phenylurea 4b complexes were also obtained using molecular dynamics (MD) simulations. The binding data showed that the association constants are strongly dependent on the nature of the substituent (alkyl/aryl) at the urea unit. tert-Butyl urea 4a is a much weaker receptor than phenylurea 4b, and showed association constants that decrease with decreasing of anion basicity. Phenylurea 4b is a highly efficient anion receptor, exhibiting a remarkable binding ability towards BzO(-) ion (log K-ass = 4.81). In comparison to the phenylurea analogue bearing a butyl spacer and a cone conformation, receptor 4b containing a shorter spacer (three carbon atoms) and a partial cone conformation is more pre-organized, displaying a strong enhancement of its binding efficiency. MD simulations have shown that the anions are preferentially bound to the urea moieties of the macrocycle lower rim, in agreement with the ROESY spectrum carried out with phenylurea 4b and BzO(-) anion.

We report the thickness dependence of critical current density (J(c)) in YBa2Cu3O7-x (YBCO) films with BaZrO3 (BZO) and Y2O3 additions grown on single crystal LaAlO3 substrates by metalorganic deposition using trifluoroacetates (TFA-MOD). Comparing with pure YBCO films, the J(c) of BZO/Y2O3-doped YBCO films was significantly enhanced. It was also found that with the increase of the thickness of YBCO film from 0.25 mu m to 1.5 mu m, the I-c of BZO/Y2O3-doped YBCO film increased from 130 A/cm to 250 A/cm and yet J(c) of YBCO film decreased from 6.5 MA/cm(2) to 2.5 M A/cm(2). The thick BZO/Y2O3-doped MOD-YBCO film showed lower J(c), which is mainly attributed to the formation of a-axis grains and pores.