Metal–ligand ring aromaticity in a 2D coordination polymer used as a photosensitive electronic device

In this study, aromaticity of a 14-membered metal-ligand ring present in a two-dimensional coordination polymer (2D CP), [Zn-2(fum)(2)(4-phpy)(4)(H2O)(2)] (1) (H(2)fum = fumaric acid and 4-phpy = 4-phenyl pyridine), was theoretically investigated by calculating the nucleus-independent chemical shifts (NICS). Furthermore, the calculation was supported by free of in-plane component NICS (FiPC-NICS) used specifically for inorganic heterocycle and electron localization function (ELF) analysis. The calculations reveal that the metal-ligand ring has an aromatic character and a moderate C-H center dot center dot center dot pi interaction energy (-8.56 kcal mol(-1) at the HF/6-311++G(d,p) level of theory) of 4-phpy with the 14-membered ring, which plays an active role in the molecular self-assembly for crystal packing. Furthermore, the compound 1 has a substantive photosensitivity with an appreciable on-off ratio; therefore, this material can be used as a photosensitive electronic device.