Photomagnetic properties of an Fe(II) spin-crossover complex of 6-(3,5-diamino-2,4,6-triazinyl)-2,2′-bipyridine and its insertion into 2D and 3D bimetallic oxalate-based networks

The Fe(II) complex of the L1 ligand (L1 = 6-(3,5-diamino-2,4,6-triazinyl)-2,2'-bipyridine) has been used as a templating cation for the growth of oxalate-based networks. The magnetic characterization of the [Fe-II(L-1)(2)](ClO4)(2 center dot)CH3CN (1) precursor in the solid state has been performed for the first time showing that the low-spin (LS) state is predominating from 2 to 400 K with 10% of Fe((II)), which undergoes a gradual and irreversible spin-crossover above 350 K. 1 presents the LIESST effect with a photo-conversion close to 25% and a T(LIESST) of 49 K. During the preparation of 1, a secondary product of the formula [Fe-II(L-1)(CH3CN)(2)(H2O)](ClO4)(2)center dot CH3CN (2) has been obtained. The magnetic characterization of 2 shows that it contains high-spin (HS) Fe((II)). 1 has afforded two novel oxalate-based compounds, the 2D compound of the formula [Fe-II(L-1)(2)][(MnCrIII)-Cr-II(ox)(3)](2)center dot(CH3NO2)(6 center dot)(CH3OH)center dot(H2O)(2) (3) and the 3D compound of the formula [Fe-II(L-1)(2)][(MnCrIII)-Cr-II(ox)(3)](2)center dot(CH3CN)(3)(4), which have been obtained by changing the synthetic conditions. The magnetic properties show that in 3 the inserted Fe((II)) cation remains in the LS state from 2 to 340 K and presents a partial and irreversible spin-crossover of similar to 20% at higher temperatures. In 4, most of the Fe((II)) complexes remain in the LS state from 2 to 230 K and present a partial and irreversible spin-crossover of similar to 50% from 230 to 400 K. 3 and 4 do not present the LIESST effect.