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).