1. J. Heyrovský Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, v.v.i., Dolejškova 3,
182 23 Prague 8, Czech Republic
2. Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic
3. Faculty of Education, J. Selye University, Bratislavská cesta 3322, 945 01 Komárno,
Slovak Republic