Syntheses, structures, and spectroscopy of mono- and polynuclear lanthanide complexes containing 4-acyl-pyrazolones and diphosphineoxide

Lanthanide coordination compounds are important due to their unique luminescence and magnetic properties. Direct synthesis of oligo- and polymeric Ln complexes with a predicted structure is hampered due to high coordination numbers and unstable coordination polyhedra. A «building blocks» strategy for the synthesis of Ln(Q)₃L polymers (Ln = Eu, Tb or Gd; HQ = 1-phenyl-3-methyl-4-RC(O)pyrazol-5-one in general, in detail HQ_S, R = thienyl; HQ_CP: R = cyclopentyl; L = bis(diphenylphosphine)methane dioxide dppMO₂, bis(diphenylphosphine)ethane dioxide dppEO₂, and bis(diphenylphosphine)butane dioxide dppBO₂) has been used: {Ln(Q)₃} mononuclear fragments have been linked by dppXO₂ bridges when X = E or B, while monomeric molecular derivatives have been isolated with dppMO₂. Eighteen new complexes were prepared, 12 of them showing a polymeric nature and 6 being monomers. Three compounds have been structurally characterized, further confirming the hypothesized connectivity where metal centers have been found to exist in LnO₈ square antiprismatic environments. Luminescence properties have been also investigated.