The syntheses, structures and magnetic properties of the compounds of formula [Fe(III)(sal(2)-trien)][Mn(II)Cr(III)(ox)(3)].CH(2)Cl(2) (1; H(2)sal(2)-trien=N,N'-disalicylidenetriethylenetetramine, ox=oxalate), [Fe(III)(sal(2)-trien)][Mn(II)Cr(III)(ox)(3)].CH(3)OH (2), [In(III)(sal(2)-trien)][Mn(II)Cr(III)(ox)(3)].0.25H(2)O.0.25CH(3)OH.0.25CH(3)CN (3), and [In(III)(sal(2)-trien)][Mn(II)Cr(III)(ox)(3)].CH(3)NO(2).0.5H(2)O (4) are reported. The structure of 1 presents a 2D honeycomb anionic layer formed by Mn(II) and Cr(III) ions linked through oxalate ligands and a cationic layer of [Fe(sal(2)-trien)](+) complexes intercalated between the 2D oxalate network. The structures of 2, 3, and 4 present a 3D achiral anionic network formed by Mn(II) and Cr(III) ions linked through oxalate ligands with [Fe(sal(2)-trien)](+) or [In(sal(2)-trien)](+) complexes and solvent molecules intercalated within the 3D oxalate network. The magnetic properties and Mössbauer spectroscopy of 1 and 2 indicate that these compounds undergo a long-range ferromagnetic ordering at around 5 K and a spin crossover of the intercalated [Fe(sal(2)-trien)](+) complexes above 130 K, which is complete in the case of 1. The magnetic properties of the compounds 3 and 4 confirm the ferromagnetic ordering of the bimetallic oxalate network.

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Combining Fe(ii) with the carboxylate-functionalized 2,6-bis(pyrazol-1-yl)pyridine (bppCOOH) ligand results in the spin-crossover compound [Fe(bppCOOH)2](ClO4)2 which shows an abrupt spin transition with a T1/2 of ca. 380 K and a TLIESST of 60 K due to the presence of a hydrogen-bonded linear network of complexes.