 Europium compounds tend to exist trivalent oxidation state under most conditions . Commonly these compounds feature Eu ( III ) bound by 6 – 9 <unk> <unk> , typically water . These compounds , the <unk> , <unk> , <unk> , are soluble in water or polar organic solvent . <unk> europium complexes often feature <unk> @-@ like <unk> , e.g. , <unk> . 
