Single‐Crystal to Single‐Crystal Transformations and Magnetic Properties of a Series of “Butterfly” Ni II 2 Ln III 2 Compounds: SMM Behavior of the Dysprosium(III) Analogue

This investigation reports syntheses, crystal structures, and magnetic properties of a series of “butterfly” Ni II 2 Ln III 2 compounds of compositions [Ni II 2 Ln III 2 L 4 (NO 3 ) 2 (MeOH) 2 ] ( 1 , Ln = Gd; 2 , Ln = Tb; 3 , Ln = Dy; 4 , Ln = Ho; 5 , Ln = Er) and [Ni II 2 Ln III 2 L 4 (NO 3 ) 2 (H 2 O) 2 ] · 2H 2 O ( 1A , Ln = Gd; 2A , Ln = Tb; 3A , Ln = Dy; 4A , Ln = Ho; 5A , Ln = Er), where H 2 L is the Schiff base ligand, obtained on [1+1] condensation of 3‐ethoxysalicylaldehyde and 2‐aminophenol. The five compounds 1A – 5A are formed as a result of single‐crystal to single‐crystal transformations (SC–SC) of the five compounds 1 – 5 . The dc and ac magnetic measurements carried out for the five stable compounds 1A – 5A reveal the following: (i) overall ferromagnetic interaction exists in all of the Ni II 2 Ln III 2 compounds 1A – 5A ; (ii) both Ni II ··· Ni II and Ni II ··· Gd III interactions in the Gd III analogue 1A are ferromagnetic, with J values of 1.83(0.08) cm –1 and 0.285(0.002) cm –1 , respectively; and (iii) only the Dy III analogue 3A exhibits single‐molecule magnet (SMM) properties, with an energy barrier ( U eff ) of 25 cm –1 and a relaxation time ( τ 0 ) of 8 × 10 –8 s. Comparison of the structures and properties of the compounds in the present investigation with those of analogous systems derived from a related ligand reveals remarkable differences.