Anionic lanthanide complexes with 3-methyl-1-phenyl-4-formylpyrazole-5-one and hydroxonium as counter ion

New lanthanide (Ln) coordination compounds of the composition [H3O][LnL4]·nH2O (n = 1-3, Ln = Nd, Sm, Eu, Tb; HL - 3-methyl-1-phenyl-4-formylpyrazol-5-one) with hydroxonium cation as counter were synthesized and investigated by various means, showing the rare case of stronger Sm(III) luminescence compared with an analogues Eu(III) compound.