Three new supramolecular networks formed via hydrogen bonding interactions: Syntheses, crystal structures and magnetic properties

Three new iron(III) citrate complexes [Fe2(cit)2(H2O)2](H2bpa) (1), [Fe2(cit)2(H2O)2](H2bpe) (2) and [Fe4(cit)4(H2O)4](H2bpp)2(H2O) (3) (cit = C(O−)(COO−)(CH2COO−)2, bpa = 1,3-bis(4-pyridyl)ethane, bpe = 1,3-bis(4-pyridyl)ethene, bpp = 1,3-bis(4-pyridyl)propane) were synthesized and characterized by elemental analysis, spectroscopic techniques and magnetic properties. Single X-ray diffraction analyses in the 1–3 complexes reveal that the iron ion is six-coordinated and is bound by two deprotonated citrates and a pair of aqua ligands in a distorted octahedral fashion. The anionic complex contains a centro-symmetrical planar of four-membered Fe2O2 ring. There are significant contributions to the stabilities of the assembled lattices in 1–3 arising from the protonated pyridine analogue counterions neutralizing the anionic charges of the complexes. The units in the complexes are connected together via hydrogen bonding to form 3D supramolecular networks. The supramolecular structures of 1–2 show alternating R66(50) and R64(48) motif linking the anionic moieties which are in turn interwoven with cationic moieties, while 3 shows alternating R66(51) and R64(49) motif. The magnetic properties of 1–3 are investigated and discussed in detail.

Graphical abstractThree supramolecular compounds have been constructed by the self-assembly of iron(III) citrate complexes containing three types of pyridyl-like ramification. The magnetic susceptibility studies of 1–3 complexes demonstrate the presence of anti-ferromagnetic interaction between two Fe(III) ions.Figure optionsDownload full-size imageDownload as PowerPoint slide