Layered dipyridylamide coordination polymers from in situ lactonization of 2-carboxycinnamic acid

Hydrothermal reaction of divalent metal nitrates with 2-carboxycinnamic acid (H2cca) and 3-pyridylisonicotinamide (3-pina) caused in situ rearrangement of the acid precursor to the anionic lactone 1,3-dihydro-3-oxo-1-isobenzofuranacetate (dibf). This resulted in generation of a series of coordination polymer solids of the form [M(3-pina)2(dibf)2]n (M = Zn, 1; Cd, 2; Co, 3; Mn, 4; Ni, 5). Single-crystal X-ray diffraction revealed that 1–5 are isostructural, manifesting (4,4) grid motifs with capping dibf ligands. Use of the structurally related 3-(2-carboxyphenyl)propionic acid (H2cpp) as a precursor avoided any in situ rearrangement. Still, the resulting coordination polymer [Co(3-pina)2(Hcpp)2]n (6) shows a topology virtually identical to 1–5, but with protonated Hcpp carboxylate hydrogen bonding patterns within the grid apertures. Luminescence properties of the d10 derivatives 1 and 2 are also presented, along with thermal degradation behavior.