Abstract
By reacting a 3,6-ditriazolyl-2,5-dihydroxybenzoquinone (H(2)trz(2)An) anilato linker with Ln(III) ions (Ln(III) = Dy, Tb, Ho), two different series of polymorphs, formulated as [Ln(2)(trz(2)An)(3)(H(2)O)(4)] (n) ·10H(2)O (Dy(III), 1a; Tb(III), 2a, Ho(III), 3a) and [Ln(2)(trz(2)An)(3)(H(2)O)(4)] (n) ·7H(2)O (Dy(III), 1b, Tb(III), 2b, Ho(III), 3b) have been obtained. In these series the two Dy(III)-coordination networks (1a and 1b) and the Tb(III)-coordination polymer (2b) show a Single Ion Magnet (SIM) behavior. 1-3a MOFs show reversible structural flexibility upon removal of a coordinated water molecule from a distorted hexagonal 2D framework to a distorted 3,6-brickwall rectangular 3D structure in [Ln(2)(trz(2)An)(3)(H(2)O)(2)] (n) ·2H(2)O (Dy(III), 1a_des; Tb(III), 2a_des, Ho(III), 3a_des) involving shrinkage/expansion of the hexagonal-rectangular networks. Noteworthy, 2b represents the first example of a Tb(III)-anilate-based coordination polymer showing SIM behaviour to date and the best SIM properties within the polymorphs. Theoretical investigation via ab initio CASSCF calculations supports this behavior, since 2b shows less mixing between the m (J) states of the ground state among all the studied complexes.