Magnetic relaxation in two chain-like Zn2Dy2 Schiff base coordination polymers bridged by tetraoxolene and its one-electron reduced radical

In the process of solvothermal synthesis of one-dimensional (1D) Zn-Dy Schiff base coordination polymers, 25% of tetraoxolene anions (X2tetraox2−) underwent a one-electron reduction in situ reaction to form X2tetraox3•− radical anions, which was verified by the νCO vibration Raman spectra. Both the (X2tetraox2−) anion and the X2tetraox3•− radical anion act as bridging ligands to connect two Zn-Dy Schiff base structural units [DyZn(LSchiff)(NO3)(MeOH)]2+ (H2LSchiff = N, N′- bis(3-methoxysalicylidene)-1,3-diaminopropane) and [DyZn(LSchiff)(MeOH)2]3+, and finally assemble into two ionic zig-zag chain-like coordination polymers, [Dy2Zn2(LSchiff)2(X2tetraox2−)1.5(X2tetraox3•−)0.5(NO3)(MeOH)3](ClO4)0.5∙2MeOH [1: X = Cl; 2: X = Br]. The two 1D Zn-Dy heterometallic coordination polymers exhibit the properties of single-molecule magnets (SMMs), and have two-step magnetic relaxation behaviors under a 1500 Oe dc field. Their effective energy barriers are adjusted by the halogenated groups on the bridging ligands X2tetraox2− and X2tetraox3•−.