By changing template cation but introducing trivalent iron ions in the known niccolite structural metal formate frameworks, three complexes formulated [NH 2 (CH 3 ) 2 ][Fe III M II (HCOO) 6 ] (M = Fe for 1, Mn for 2, and Co for 3) were synthesized and magnetically characterized. The variation in the compositions of the complexes leads to three different complexes: mixed-valent complex 1, heterometallic but with the same spin state complex 2, and heterometallic heterospin complex 3. The magnetic behaviors are closely related to the divalent metal ions used. Complex 1 exhibits negative magnetization assigned as N eel N-Type ferrimagnet, with an asymmetric magnetization reversal in the hysteresis loop, and complex 2 is an antiferromagnet with small spin canting (R canting ≈ 0.06°and T canting = 35 K), while complex 3 is a ferrimagnet with T N = 32 K.

Multiple switchable physical properties have been demonstrated in one single niccolite structural metal-organic framework, [(CH CH ) NH ][Fe Fe (HCOO) ] (1), including (i) a reversible ferroelastic phase transition triggered by freezing the disordered (CH CH ) NH cations, (ii) a thermally switchable dielectric constant transition accompanied by phase transition, and (iii) thermal and positive magnetic field driven magnetic poles reversal at low temperatures, attributed to different responses of the magnetization of Fe and Fe sublattices to external stimuli. More interestingly, the exchange anisotropy between the two sublattices can also give rise to tunable positive and negative exchange bias fields. Straightforwardly, such diverse demonstrations of bistability in one single material (depending on the specific tuning way) will provide extra freedom and flexibility for the design of switcher devices.

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An unprecedented decanuclear Gd(III) cluster composed of the [Gd10(μ3-OH)8](22+) core has been hydrothermally synthesized. Magnetic analyses indicate that this complex shows weak antiferromagnetic behavior with a relatively large magnetocaloric effect (-ΔS(m)(max) = 31.22 J kg(-1) K(-1)).