Structural diversity in manganese squarate frameworks using N,N-donor chelating/bridging ligands: syntheses, crystal structures and magnetic properties

Three new polymeric squarato-bridged manganese complexes {[Mn(H2O)(2)(bpe)(sq)] center dot bpe center dot H2O}(n) ( 1), [Mn-2(H2O)(4)(phen)(2)(sq)(2)](n) ( 2) and [Mn-2(H2O)(2)(phen)(4)(sq)] center dot (sq) center dot 8(H2O) (3) [bpe, 1,2-bis(4-pyridyl)ethane; phen, 1,10-phenanthroline; sq, squarate dianion] have been synthesized and characterized by single crystal X-ray diffraction analysis and variable temperature magnetic studies. Complex 1 is a 2D rectangular grid-like structure, achieved through flexible bpe bridging ligands and squarate dianions. On the other hand the use of chelating phen instead of bpe gives rise to a 1D polymeric chain in complex 2 and to a dinuclear entity in 3. In all the three complexes weak interactions play a vital role in stabilizing the solid-state structure. Variable temperature ( 2 - 300 K) magnetic studies indicate weak antiferromagnetic coupling between the metal centres in all the complexes.