3–(2–Pyridyl)pyrazole Based Luminescent 1D-Coordination Polymers and Polymorphic Complexes of Various Lanthanide Chlorides Including Orange-Emitting Cerium(III)

A series of 18 lanthanide-containing 1D-coordination polymers 1∞[Ln2(2–PyPzH)4Cl6], Ln = La, Nd, Sm, dinuclear polymorphic complexes α–, β–[Ln2(2–PyPzH)4Cl6], Eu, Gd, α–[Tb2(2–PyPzH)4Cl6], and [Gd2(2–PyPzH)3(2–PyPz)Cl5], mononuclear [Ce(2–PyPzH)3Cl3], [Ln(2–PyPzH)2Cl3], Tb, Dy, Ho, Er, salt-like [Gd3(2–PyPzH)8Cl8]Cl [PyH][Tb(2–PyPzH)2Cl4] were obtained from the reaction respective lanthanide chloride with 3–(2–pyridyl)pyrazole (2–PyPzH) ligand at different temperatures. An antenna effect through ligand-to-metal energy transfer was observed for several products, leading to highest luminescence efficiency displayed by a quantum yield 92% in [Tb(2–PyPzH)2Cl3]. The Ce3+ ion complex [Ce(2–PyPzH)3Cl3] exhibits bright orange 5d-based broadband emission maximum around 600 nm, marking an example strong reduction 5d-excited states Ce(III). absorption spectroscopy shows ion-specific 4f–4f transitions, which can be assigned Nd3+, Sm3+, Eu3+, Dy3+, Ho3+, Er3+ wide spectral range UV–VIS NIR region.