Coordination polymers of copper(II) with pyridyl-methylamino benzoate linkers: Structures and solvent-induced structural transformation

• Three copper(II) coordination polymers (CPs) using the flexible N,O-donor ligands 4-[(pyridin-4-ylmethyl)amino]benzoate (44paba) or 3-[(pyridin-4-ylmethyl)amino]benzoate (34paba). were successfully synthesized and characterized. • The CPs have non-interpenetrated frameworks which differ in coordination but are always 2D grid-type. • Guest desorption from {[Cu(44paba) 2 (H 2 O].2DMF} n ( I) and {[Cu(34paba) 2 (H 2 O] 4 .[Cu(34paba) 2 ].4DMF} n ( II) resulted in the formation of a new collapsed phase. • {[Cu(34paba) 2 ].1.6DMA} n ( III ) was subject to guest exchange by soaking. • The crystal structure of the water-exchanged material was elucidated, {[Cu(34paba) 2 ]. 2.25(H 2 O)} n (IIIW) , which provided further evidence of the flexibility of the framework through the concertina-like action of the 2D grids. Four new coordination polymers have been prepared using the flexible linkers 4-[(pyridin-4-ylmethyl)amino]benzoate (44paba) and 3-[(pyridin-4-ylmethyl)amino]benzoate (34paba). {[Cu(44paba) 2 (H 2 O].2DMF} n ( I), {[Cu(34paba) 2 (H 2 O] 4 .[Cu(34paba) 2 ].4DMF} n ( II) and {[Cu(34paba) 2 ].1.6DMA} n ( III) were synthesized by slow evaporation and characterized by FT-IR, thermal analysis and diffraction analysis. {[Cu(34paba) 2 ]. 2.25(H 2 O)} n (IIIW) was prepared by solvent exchange from III . Single crystal X-ray diffraction revealed that the copper(II) ion coordination geometry is octahedral in all cases, but that the carboxylate moiety binds in a monodentate fashion in I , bidentate in III and IIIW and that II contains two different frameworks in which the carboxylate is either mono- or bidentate. In all cases the frameworks form 2D layers with paba bridging linkers between copper ions. The frameworks are shown to be flexible and display a concertina-like ability to link with longer or shorter Cu…Cu distances.