[2+2] or [4+4] metallamacrocycle: Synthesis and crystal structures of Hg(II) complexes derived from two flexible bis(pyridylurea) ligands

Abstract Two complexes, [Hg 2 ( L 1 ) 2 Br 4 ]·4DMF·2H 2 O ( 1 ) and [Hg 4 ( L 2 ) 4 Br 8 ]·8DMF·2H 2 O ( 2 ), have been synthesized and characterized from two flexible bis(pyridylurea) ligands ( L 1 and L 2 ) with mercury(II) bromide respectively. Both the two complexes exist as centrosymmetric metallamacrocycles with four-coordination Hg(II) centers, but they present different architectures with slightly adjusted 3- and 4-position of nitrogen atom in the pyridyl rings from the two ligands. Complex 1 exists as a [2+2] metallamacrocycle with L 1 as bidentate ligands bridging two HgBr 2 , while complex 2 exists as a novel 84-membered [4+4] metallamacrocycle, which indicates that the nature of the ligand plays an important role in the coordination networks.