Near-IR Luminescence and Field-Induced Single Molecule Magnet of Four Salen-type Ytterbium Complexes

A series
of rigid hexadentate salen-type (H2L) ytterbium
complexes, namely, [Yb2L3(CH3OH)]·3CH3CN (1), [Yb2LL′L″(CH3OH)­(H2O)2]­(ClO4)2·CH3OH·H2O (2), [Yb2L­(OAc)4(CH3OH)2]·2CH3OH (3), and {[Yb2L­(OAc)4]·3H2O}n (4) (H2L = N,N′-bis­(2-oxy-3-methoxybenzylidene)-1,2-phenylenediamine,
HL′ = 2-(2′-hydroxy-3′-methyloxy-phenyl)­benzimidazole
and HL” = 3-methoxysalicylaldehyde) have been synthesized by
reactions of H2L with multifarious Yb3+ salts.
X-ray crystallographic analyses demonstrate that complex 1 is of a triple-decker sandwich-type Yb2L3 structure
with a ratio of H2L/Yb = 3:2, 2 and 3 possess the unique Yb2 core with a ratio of H2L/Yb = 2:2 and 1:2, respectively, 4 exhibits
one dimensional coordination polymers in which the polymeric structures
are formed by acetate (OAc–) groups. All complexes 1–4 exhibit near-IR luminescence, which
can be rationalized on the basis of the disparate structural effects.
The magnetic analysis unveils that all complexes 1–4 are of field-induced single-molecule magnet behavior with
the energy barriers (Ueff/kB) of 14.5, 2.0, 9.5, and 2.4 K at 3 kOe direct current
fields, respectively.