Highly pH-dependent synthesis of two novel three-dimensional dysprosium complexes with interesting magnetic and luminescence properties

Abstract

Two novel Dy-based MOFs, namely, {[Dy 2 IJPA) 3 IJH 2 O) 3 IJDMF)]ĴIJDMF) 2 ĴIJH 2 O)} n (1) and ijDy 2 IJPA) 3 IJH 2 O) 2 -IJDMF) 2 ]ĴIJDMF) 3 ĴIJH 2 O)} n (2) (H 2 PA = pamoic acid), were solvothermally synthesized from the reaction of DyIJNO 3 ) 3 and H 2 PA at different pH values. Interestingly, both complexes can be obtained simultaneously within the pH range of 5.0-6.2, while higher pH values (6.2-7.0) promote the formation of compound 1 and lower pH values (2.0-5.0) tend to produce pure complex 2. Single-crystal X-ray diffraction studies indicate that 1 and 2 are both three-dimensional frameworks composed of dinuclear DyIJIII) subunits featuring pcu networks with the point symbol of {4 12 Ĵ6 3 }. Significantly, their slight structure difference results in these two compounds showing completely different magnetic properties. Variable temperature magnetization measurements ( χ M T-T) demonstrate ferromagnetic interactions in compound 1, while possible antiferromagnetic interactions were observed in compound 2. Alternating current (ac) susceptibility measurements indicate that both the in-phase ( χ′) and out-of-phase ( χ″) components showed frequency dependence in compound 1, suggesting that there is a slow relaxation behavior of the magnetization, which is typical of single-molecule magnets (SMMs), while no out-of-phase ac signal was noticed for 2. Furthermore, both 1 and 2 exhibit the characteristic luminescence of Dy 3+ upon excitation at 365 nm, but with different intensities. The reasons for such magnetic and luminescence differences are discussed in detail.

A dysprosium(III) complex based on Schiff-base ligand exhibiting two magnetic relaxation processes

“…M increases rapidly at low field and then grows slowly without complete saturation up to 8 T. Its magnetization values (23.43Nb) at 8 T are lower than the theoretical saturated value of 30Nb anticipated for three independent Dy 3+ ions, which can be mainly attributed to magnetic anisotropy [15]. Furthermore, the M vs HT À1 data at 2.0-5.0 K show non-superimposed magnetization curves for complex 1 confirms the presence of anisotropy and/or low-lying excited states [16], which is expected for compound containing Dy 3+ ions (Fig. 4).…”

Tuning the Magnetoluminescence Behavior of Lanthanide Complexes Having Sphenocorona and Cubic Coordination Geometries

“…The plausible reason behind this behavior may be two‐fold: (i) differences in the coordination environment around the Dy III ion in complexes 1 and 2 , and (ii) attachment of a more chromophoric ligand to Dy III in complex 1 , which can facilitate a more efficient antenna effect in 1 . In complex 3 , three characteristic bands at 468, 518, and 556 nm are observed that correspond to 5 F 3 →( 5 I 8 , 5 F 4 ), 5 S 2 → 5 I 8 , and 5 F 5 → 5 I 8 transitions, respectively (Figure b) . For complex 4 , the emission spectrum exhibits characteristic strong emission bands of Tb III at 494, 545, 581, and 623 nm (Figure c) .…”

Synthesis, crystal structures and, magnetic and photoluminescence properties of lanthanide-based metal–organic frameworks constructed with 2,5-dihydroxybenzene-1,4-dicarboxylic acid

“…The plots of M versus H for complexes show nonsuperposition of curves, indicating magnetic anisotropic nature of 3 and 4. [76][77][78] Magnetization versus eld (À90 to 90 kOe) plots of 3 and 4 ( Fig. 9) at 4 K is showing relatively more hysteresis loop for 3 and hence presence of more coercive forces.…”