A new three-dimensional barium(II) coordination polymer constructed from N,N′-bis(glycinyl)-pyromellitic diimide: microwave-assisted synthesis, structure, Hirshfeld surface analysis and properties

A new three-dimensional (3D) coordination polymer, namely, poly[diaqua[mu(5)-2,2 '-(1,3,5,7-tetraoxo-1,2,3,5,6,7-hexahydropyrrolo[3,4-f]isoindole-2,6-diyl)di-acetato]barium(II)], [Ba(C14H6N2O8)(H2O)(2)](n), (I), has been synthesized by the microwave-irradiated reaction of Ba(NO3)(2) with N,N '-bis(glycinyl)pyromellitic diimide {BGPD, namely, 2,2 '-(1,3,5,7-tetraoxo-1,2,3,5,6,7-hexahydropyrrolo[3,4-f]isoindole- 2,6-diyl)diacetatic acid, H2L}. The title compound was structurally characterized by single-crystal X-ray diffraction analysis and powder X-ray diffraction analysis, as well as IR spectroscopy. In the crystal structure of (I), the Ba-II ion is nine-coordinated by six carboxylate O atoms from five symmetry-related L2- dianions and one imide O atom, as well as two water O atoms. The coordination geometry of the central Ba-II ion can be described as a spherical capped square antiprism. One carboxylate group of the ligand serves as a mu(3)-bridge linking the Ba-II cations into a one-dimensional polynuclear secondary building unit (SBU). Another carboxylate group of the ligand acts as a mu(2)-bridge connecting the 1D SBUs, thereby forming a two-dimensional (2D) SBU. The resulting 2D SBUs are extended into a 3D framework via the pyromellitic diimide moiety of the ligand as a spacer. The 3D Ba framework can be simplified as a 5-connected hexagonal boron nitride net (bnn) topology. The intermolecular interactions in the 3D framework were further investigated by Hirshfeld surface analysis and the results show that the prominent interactions are H center dot center dot center dot O (45.1%), Ba center dot center dot center dot O (11.1%) and C center dot center dot center dot H (11.1%), as well as H center dot center dot center dot H (11.1%) contacts. The thermal stability, photoluminescence properties and UV-Vis absorption spectra of (I) were also investigated. The coordination polymer exhibits a fluorescence emission with a quantum yield of 0.071 and high thermal stability.