2 research outputs found
Relationship between solid state structure and solution stability of copper(ii)-hydroxypyridinecarboxylate complexes
The complementary solid state/solution studies of the systematic series of bioactive ligands 3-hydroxy-
1-methyl-4-pyridinecarboxylate (L1), 3-hydroxy-1,2,6-trimethyl-4-pyridinecarboxylate (L2), 4-hydroxy-1-
methyl-3-pyridinecarboxylate (L3), 4-hydroxy-1,6-dimethyl-3-pyridinecarboxylate (L4), 4-hydroxy-1-(2-
hydroxyethyl)-6-methyl-3-pyridinecarboxylate (L5) and 4-hydroxy-1-(2-carboxyethyl)-6-methyl-3-
pyridinecarboxylate (L6) with copper(II) have been performed in order to design efficient chelating drugs
for the treatment of metal overloading conditions. Single crystals of [Cu(L1)2(H2O)]3H2O (1) (monomer) with
axial water coordination, [Cu2(L2)4]6H2O (2) and [Cu2(L3)4]4H2O (3) (cyclic dimers), where pyridinolato and
carboxylato oxygens, respectively, act as linkers between adjacent copper complexes, [Cu(L4)2]n3H2O (4) (1D
polymer) and [Cu3(L5)6]18H2O (5) (trimer), constructed using two square-pyramidal and one elongated
octahedral Cu(II) complexes have been determined by SXRD. The bidentate coordination mode of the ligands
has been found preferentially with cis arrangements in 1 and 2 and trans arrangements in 3\u20135. The solution
speciation and complex stability of aqueous solutions have been studied by pH-dependent electron
paramagnetic resonance spectroscopy resulting in the detection of solely monomeric [CuL]+ and [CuL2]
complexes. The stability order obtained for the [CuL]+ complexes could be correlated with the deprotonation
constants of their hydroxyl group (log bLH) reflecting that the higher acidity increases the complex stability in
the order L2 o L1 E L6 o L4 E L5 o L3. This stability order elucidates the different axial linkers in the
cyclic dimers 2 and 3. DFT quantum-chemical calculations support the effect of the electron distribution on
the established stability order