1 research outputs found
Polyfunctional Tetraaza-Macrocyclic Ligands: Zn(II), Cu(II) Binding and Formation of Hybrid Materials with Multiwalled Carbon Nanotubes
The binding properties
of HL1, HL2, and HL3 ligands toward CuĀ(II)
and ZnĀ(II) ions, constituted by tetraaza-macrocyclic rings decorated
with pyrimidine pendants, were investigated by means of potentiometric
and UV spectrophotometric measurements in aqueous solution, with the
objective of using the related HL-MĀ(II) (HL = HL1āHL3; M =
Cu, Zn) complexes for the preparation of hybrid MWCNT-HL-MĀ(II) materials
based on multiwalled carbon nanotubes (MWCNTs), through an environmentally
friendly noncovalent procedure. As shown by the crystal structure
of [CuĀ(HL1)]Ā(ClO<sub>4</sub>)<sub>2</sub>, metal coordination takes
place in the macrocyclic ring, whereas the pyrimidine residue remains
available for attachment onto the surface of the MWCNTs via ĻāĻ
stacking interactions. On the basis of equilibrium data showing the
formation of highly stable CuĀ(II) complexes, the MWCNT-HL1-CuĀ(II)
material was prepared and characterized. This compound proved very
stable toward lixiviation processes (release of HL1 and/or CuĀ(II));
thus, it was used for the preparation of its reduced MWCNT-HL1-Cu(0)
derivatives. X-ray photoelectron spectroscopy and transmission electron
microscopy images showed that MWCNT-HL1-Cu(0) contains Cu(0) nanoparticles,
of very small (less than 5 nm) and regular size, uniformly distributed
over the surface of the MWCNTs. Also, the MWCNT-HL1-Cu(0) material
proved very resistant to detachment of its components. Accordingly,
both MWCNT-HL1-CuĀ(II) and MWCNT-HL1-Cu(0) are promising candidates
for applications in heterogeneous catalysis