Synthesis, and Crystal Strucrures of a 1D Cobalt-Coordination Polymer Based on a Flexible Imidazole-Linked Naphthalenediimide Ligand and its Polymorphic Forms

Two polymorphs of 2,7-bis(3-(1H-imidazol-1-yl)propyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (L) and a one-dimensional (1D) cobalt coordination polymer of L (Co-Poly) have been successfully synthesized and reported. These polymorphs were crystallized using different solvent systems-polymorph 1 in dimethylformamide (DMF) and polymorph 2 in a mixture of DMF and methanol. Their solid-state structures were determined through single crystal X-ray diffraction. These compounds were characterized with spectroscopic tools like Powder X-ray Diffraction (PXRD) and elemental analysis. Various supramolecular interactions, including C–H⋯O, C–H⋯N, and C–H⋯π interactions, were identified in both polymorphs, with additional π⋯π interactions observed in polymorph 2. In the case of the coordination polymer, the Co(II) center adopts a distorted octahedral coordination environment. The polymer is synthesized under solvothermal conditions, with its solid-state structure stabilized by intra-ligand π⋯π stacking interactions. These supramolecular interactions collectively contribute to the formation of a three-dimensional (3D) supramolecular architecture in the solid-state structures of all the compounds. Additionally, 2D-fingerprint (2D-FP) and Hirshfeld surface analysis (HSA) were employed to confirm the 2D-network-packed crystal lattice interactions. Crystal void calculations indicate that all compounds exhibit mechanical stability in the solid state.