The copper complexes with the ligands containing pyridine-2-carboxamide functionality have attracted much attention in the last few years because of their interesting physico-chemical properties. 1-11 Some of the complexes were found to be effective HIV-1 protease inhibitors. 12-14 Electrospray ionization mass spectrometry (ESI-MS) is one of the most popular techniques used for the study of metal-ligand interactions. 15-18 However, ESI-MS has only been used occasionally for the study of the copper complexes with pyridine-2-carboxamide moieties. 1,11,12 This work concerns the interactions of copper(II) with Nalkyl-pyridine-2-carboxamides (1-3, Scheme 1) studied by ESI-MS. To establish the influence of the solvent, the solutions used for ESI mass spectra recording were prepared in methanol, acetonitrile or water (most popular solvents used for ESI-MS). To evaluate the influence of the counter ion, two copper salts, namely CuCl 2 and Cu(ClO 4) 2 , were used (most popular copper salts used for copper complex synthesis).

In Issue 5 of Volume 12, Scheme 2 in the paper by Frński et al. (page 314) is incorrect. The correct scheme is shown below. Scheme 2. N-alkyl-pyridine-3-carboxamides studied.