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 HQS, R = thienyl; HQCP: 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.