Solvent-controlled synthesis and reversible dynamic structural conversions of a series of iron(II) coordination complexes

Abstract

In this work, a versatile multi-dentate 1,2-bis(pyridin-4-ylmethylene)hydrazine (L) ligand has been employed to construct three novel iron(II) coordination complexes, [Fe(L)2(NCS)2(H2O)2]·2H2O (1), [Fe(L)(NCS)2(H2O)2] (2) and {[Fe(L)2(NCS)2]·2CH3OH}n (3) (NH4NCS=ammonium thiocyanate), which can be isolated under similar synthetic conditions, only different molar ratio of metal/ligand or different solvent systems are used. 1 is a mono-nuclear iron(II) coordination complex, and 2 is a one-dimensional (1D) iron(II) coordination complex, while 3 is a 2D micro-porous iron(II) framework with the channel dimensionality of 13.936(3) Å×13.936(3) Å. PXRD patterns also confirm the purity of the bulky samples of 1–3. For 1–3, it represents the first example of solvent-induced drastic reversible dynamic conformation between different dimensional iron(II) coordination complexes 1 (0D), 2 (1D) and 3 (2D) (for 1: water; for 2: benzene; for 3: methanol/acetone/acetonitrile), which are unambiguously confirmed by PXRD characterizations. Variable-temperature magnetic susceptibility data of 2–3 have been recorded in the 2–300K temperature range, indicating weak antiferromagnetic interactions.