Dual-Property Supramolecular H-Bonded 15-Crown-5 Ln(III) Chains: Joint Magneto-Luminescence and ab Initio Studies.

Two complexes comprising 9-coordinate capped square antiprismatic [Ln(NO3)3(OH2)2(MeOH)] units [Ln(III) = Dy 6; Tb 7] are reported in which the metal complexes are hydrogen-bonded to 15C5 (15-crown-5) macrocycles to form supramolecular chains, {[Ln(NO3)3(OH2)2(MeOH)]·(15C5)}n. Alternating current magnetic susceptibility measurements supported by ab initio studies show field-induced SMM (single-molecule magnet) behavior for 6, but rapid relaxation of the magnetization for 7 because of the presence of dominant quantum tunneling processes as evidenced by the presence of a significant calculated tunnel splitting within the ground-state multiplet. Modeling the high-resolution emission spectra for 6 afforded energies of 37 ± 5 and 28 ± 5 cm-1 for the first-excited-state Stark sublevels of the two crystallographically independent Dy1 and Dy2 ions, in excellent agreement with the calculated values of 31 and 21 cm-1 for ΔE1 derived from ab initio studies.