Cu(ii)–Dy(iii) and Co(iii)–Dy(iii) based single molecule magnets with multiple slow magnetic relaxation processes in the Cu(ii)–Dy(iii) complex

Abstract

Two dinuclear Schiff-base complexes [Cu(II)Dy(III)] and [Co(III)Dy(III)] have been synthesized and structurally characterized. The AC susceptibility measurements taken at BDC = 0.2 T show a slow magnetic relaxation typical for single-molecule magnets. Unusual is the presence of three relaxation branches in [Cu(II)Dy(III)]; the slowest (low-frequency) process possesses the barrier to spin reversal of U/kB = 2.8 K and an extrapolated relaxation time as slow as τ0 = 0.11 s. The intermediate-frequency process is typical for SMM of this class with U/kB = 122 K and τ0 = 9.9 × 10(-7) s; an onset of the high-frequency process is evidenced and this is the fastest. In contrast, the [Co(III)Dy(III)] complex free of exchange coupling exhibits only a single relaxation path with SMM parameters U/kB = 113 K and τ0 = 7.0 × 10(-9) s.

Synthesis, Crystal Structures, Magnetic Properties, and Fluorescence of Two Heptanuclear CoIII4LnIII3 Compounds (Ln = GdIII, DyIII): Multiple Relaxation Dynamics in the DyIII Analogue

“…A number of compounds containing both Co III and Dy III have been reported previously (Table S7) . In terms of nuclearity, those systems include Co III Dy III ,[27h], Co III 2 Dy III , Co III 2 Dy III 2 , Co III 4 Dy III 2 ,[42a] Co III Dy III 3 ,[44l] Co III 3 Dy III 3 [44m] and Co III 2 Dy III 4 . [33a, o], However, no compound of nuclearity Co III 4 Dy III 3 (or Co III 4 Ln III 3 , Ln = Ce–Yb) was reported previously.…”

“…So, in 2 , two relaxation channels at higher temperature ( T > 5 K) region arise most probably due to the presence of two distinct Dy III centers, viz , nine coordinated Dy1/Dy1D centers with TCTPR as the “most ideal” geometry and eight coordinated Dy2 center with TDD as the “most ideal” geometry. As listed in Table S7 and S8, the double‐relaxation channels in most cases are not well resolved in zero‐dc field[44f], [44g], [44k], [46a], [46c], [46e], [46h] and also even under an applied dc field. [27h], [42a], [44d] Only in very few cases, the two processes are well resolved in zero‐dc field.…”

“…As listed in Table S7 and S8, the double‐relaxation channels in most cases are not well resolved in zero‐dc field[44f], [44g], [44k], [46a], [46c], [46e], [46h] and also even under an applied dc field. [27h], [42a], [44d] Only in very few cases, the two processes are well resolved in zero‐dc field. [44h], [46b] Clearly, compound 2 is among some few examples where the two channels are well resolved in zero‐dc field and the U eff values of both channels could be determined.…”

“…[27h], [42a], [44d] Only in very few cases, the two processes are well resolved in zero‐dc field. [44h], [46b] Clearly, compound 2 is among some few examples where the two channels are well resolved in zero‐dc field and the U eff values of both channels could be determined. In the Co III Dy III SMMs, the range of U eff values is ca .…”

Manifold relaxation processes in a mononuclear Co(II) single-molecule magnet

“…Three relaxation modes were detected for a [Dy III Cu II ] 2 assembly in contrast to the [Dy III Co III ] analogue where only a single relaxation process was detected [38]. Some authors identified an on-set of another relaxation branch at low and/or high frequencies but they did not analyze such a feature in detail [11].…”