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

Abstract

Three new polymeric squarato-bridged manganese complexes {[Mn(H₂O)₂(bpe)(sq)]·bpe·H₂O}_n (1), [Mn₂(H₂O)₄(phen)₂(sq)₂]_n (2) and [Mn₂(H₂O)₂(phen)₄(sq)]·(sq)·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.