Squarato-bridged polymeric networks of iron(II) with N-donor coligands: Syntheses, crystal structures and magnetic properties

Two new squarato-bridged Fe(II) polymeric networks of molecular formula [Fe(squarate)(bpp)2(H2O)2] (1) and [Fe(squarate)(bpee)(H2O)2] (2) [bpp = 1,3-bis(4-pyridyl)propane; bpee = 1,2-bis(4-pyridyl)ethylene; View the MathML sourcesquarate=C4O42-] have been synthesized and characterized by single-crystal X-ray diffraction studies and low temperature (300–2 K) magnetic measurements. Complex 1 is a 1D coordination chain of Fe(H2O)2 units connected by μ-O,O″ squarate dianions with monocoordinated bpp ligands dangling from the polymer. These 1D chains ultimately transform to a thick 2D layer through π–π interaction of pyridyl rings as well as through hydrogen bonds. Whereas structural determination of complex 2 reveals an inclined interpenetrated 3D architecture. Magnetic data for both the complexes 1 and 2 have been fitted using the Fisher formula for S = 2 system and show antiferromagnetic coupling for both the complexes. The best fit parameters are J = −0.40 cm−1, g = 2.30 and R = 0.01 for complex 1 and J = −0.49 cm−1, g = 2.08 and R = 1.9 × 10−3 for complex 2.