1. a Department of Inorganic Chemistry , Institute of Chemistry, P. J. Šafárik University , Moyzesova 11, 041 54, Košice, Slovakia
2. b Department of Inorganic Chemistry , Masaryk University , Kotlářska 12, 61 137 Brno, Czech Republic
3. c Centre of Low Temperature Physics of the Faculty of Science of P. J. Šafárik University and Institute of Experimental Physics of the Slovak Academy of Science , Park Angelinum 9, 041 54 Košice, Slovakia