Influence of ligand substitution and the solvent effect on the structures and magnetic properties of dinuclear Dy 2 supramolecular architectures constructed with the bis-β-diketonate-Dy 2 building block as a metalloligand.

Based on the bis-β-diketonate-Dy 2 metalloligand [Dy 2 (pbth) 4 ]·2Et 3 N (1, pbth = (3z,3'z)-4,4'-(1,3-phenylene)bis(1,1,1-trifluoro-4-hydroxybut-3-en-2-one)), six dinuclear complexes with eight-coordinated geometries were synthesized solvothermally through different capping N-donor coligands or solvent systems. These complexes are namely [Dy 2 (pbth) 3 (Phen) 2 ]·2C 2 H 5 OH (2), [Dy 2 (pbth) 3 (BPhen) 2 ]·2C 2 H 5 OH (3), [Dy 2 (pbth) 3 (Dppz) 2 ]·2C 2 H 5 OH (4), [Dy 2 (pbth) 3 (Dppz) 2 ]·2CH 3 OH (4a), [Dy 2 (pbth) 3 (4-Dmbp) 2 ]·CH 3 OH·C 2 H 5 OH (5) and [Dy 2 (pbth) 3 (5-Dmbp) 2 ]·CH 3 OH (6) (Phen = 1,10-phenanthroline, BPhen = 4,7-diphenyl-1,10-phenanthroline, dppz = dipyrido [3,2- a :2',3'- c ] phenazine, 4-Dmbp = 4,4'-dimethyl-2,2'-bipyridyl, 5-Dmbp = 5,5'-dimethyl-2,2'-bipyridyl), respectively. In the synthetic processes of 2-6, one of four bis-β-diketonate ligands in the metalloligand is replaced by two capping N-donor coligands. The coordination geometries, metal distances and M-L-M torsion angles of the synthesized complexes are perceptibly fine-tuned by the modification of the capping N-donor coligands or the latticed solvent molecules. Systematic magnetic investigations indicate the different magnetic relaxation dynamics of 1-6. Complex 1 displays no characteristics of single-molecule magnets (SMMs), while complexes 2-6 exhibit SMM behaviours in the absence of a static magnetic field. Complexes 2 and 3 possess effective energy barriers ( U eff ) of 110.18 (2) K and 133.21 (4) K, respectively. Theoretical analysis based on ab initio calculation provides some interpretations of experimental observation.