Three new oxodiperoxomolybdenum complexes with nicotinic acid have been synthesized and charac- terized with the use of single-crystal analysis, XRPD versus temperature, TG/DSC, SEM and IR spectros- copy. The investigated compounds are: 1 – (NH 4 ) 2

[MoO(O 2 ) 2 .N-nicO] 2 , 2 – (nicH) 2

[MoO(O 2 ) 2 .N- nicO] 2

2(H 2 O), 3 – MoO(O 2 ) 2 (H 2 O)nicH; (N-nicO, nicH

denote nicotinic acid N-oxide and protonated nicotinic acid, respectively). Compounds 1, 2 are salts of the same acid with cyclic dinuclear anions, whereas compound 3 can be regarded as an inner salt. Compounds 1–3 are stable in ambient conditions, the respective percentages of oxygen in peroxo groups are 19.21%, 14.06% and 20.19%, respectively. Above 125 ° C peroxo compounds 1–3 decompose, forming nanometric MoO 2 and MoO 3 . TG/DSC curves reveal clear effects connected with the release of oxygen and strong exothermic effects connected with final loss of organic components. All the investigated complexes were found to be active in the oxidation of cyclooctane to cyclooctanone and cyclooctanol with molecular oxygen.