Magnetic and Luminescence Properties of 8-Coordinate Holmium(III) Complexes Containing 4,4,4-Trifluoro-1-Phenyl- and 1-(Naphthalen-2-yl)-1,3-Butanedionates

A new series of mononuclear Ho(3+) complexes derived from the β-diketonate anions: 4,4,4-trifluoro-1-phenyl-1,3-butanedioneate (btfa(−)) and 4,4,4-trifuoro-1-(naphthalen-2-yl)-1,3-butanedionate (ntfa(−)) have been synthesized, [Ho(btfa)(3)(H(2)O)(2)] (1a), [Ho(ntfa)(3)(MeOH)(2)] (1b), (1), [Ho(btfa)(3)(phen)] (2), [Ho(btfa)(3)(bipy)] (3), [Ho(btfa)(3)(di-(t)bubipy)] (4), [Ho(ntfa)(3)(Me(2)bipy)] (5), and [Ho(ntfa)(3)(bipy)] (6), where phen is 1,10-phenantroline, bipy is 2,2′-bipyridyl, di-(t)bubipy is 4,4′-di-tert-butyl-2,2′-bipyridyl, and Me(2)bipy is 4,4′-dimethyl-2,2′-bipyridyl. These compounds have been characterized by elemental microanalysis and infrared spectroscopy as well as single-crystal X-ray difraction for 2–6. The central Ho(3+) ions in these compounds display coordination number 8. The luminescence-emission properties of the pyridyl adducts 2–6 display a strong characteristic band in the visible region at 661 nm and a series of bands in the NIR region (excitation wavelengths (λ(ex)) of 367 nm for 2–4 and 380 nm for 5 and 6). The magnetic properties of the complexes revealed magnetically uncoupled Ho(3+) compounds with no field-induced, single-molecule magnet (SMMs).