Novel lanthanide-based polymeric chains and corresponding ultrafast dynamics in solution

Two types of structurally related one-dimensional coordination polymers were prepared by reacting lanthanide trichloride hydrates [LnCl3·(H2O)m] with dibenzoylmethane (Ph2acacH) and a base. Using cesium carbonate (Cs2CO3) and praseodymium, neodymium, samarium, or dysprosium salts yielded [Cs{Ln(Ph2acac)4}]n (Ln = Pr (1), Nd (2), Sm (3), Dy (4)) in considerable yields. Reaction of potassium tert-butoxide (KOtBu) and the neodymium salt [NdCl3·(H2O)6] with Ph2acacH resulted in [K{Nd(Ph2acac)4}]n (5). All polymers exhibit a heterobimetallic backbone composed of alternating lanthanide and alkali metal atoms which are bridged by the Ph2acac ligands in a linear fashion. ESI-MS investigations on DMF solutions of 1−5 revealed a dissociation of all the five compounds upon dissolution, irrespective of the individual lanthanide and alkali metal present. Temporal profiles of changes in optical density were acquired performing pump/probe experiments with DMF solutions of 1−5 via femtosecond laser spectroscopy, highligh...