Exploration of the Differences in Coordination Behaviors and Spectrographic Properties of Two Novel Seven‐Nucleated Ni (II) Complexes of a Salamo‐Type Flexible‐Bisoxime Ligand

ABSTRACT A salamo‐type bis‐oxime ligand H 2 L was synthesized, which reacted with Ni (NO 3 ) 2 ·6H 2 O in different reaction solvents to synthesize two novel heptanuclear Ni (II) complexes: [Ni 7 (L) 3 ( μ 3 ‐OH) 8 (EtOH) 6 ]·2CH 2 Cl 2 ( 1 ) and [Ni 7 (L) 3 ( μ 3 ‐OMe) 2 ( μ 3 ‐OH) 6 (MeOH) 6 ]·CH 2 Cl 2 ( 2 ). X‐ray crystal diffraction results showed that each Ni (II) ion exhibits a distorted octahedral geometry. Its uniqueness lies in the fact that the Ni (II) ion in Complex 1 not only coordinates with ligand units but also coordinates with ethanol solvent molecules and water molecules participating in bridging. Complex 2 is composed of water molecules and methanol molecules connected together. Interestingly, the coordination mode is different due to the different reaction solvents. The energy gap changes of the ligand, and its complexes were then explored by DFT calculations. In addition, the influence of the weak interaction force was confirmed through the in‐depth study of electrostatic potential, IRI, freedom analysis, and Hirshfeld surfaces analyses, which is important for explaining the formation of reaction sites and supramolecular structures. UV‐visible spectrometric titration tests showed that the binding ratios of the ligand to Ni (II) ions are all 3:7, which is consistent with the crystal structure. Finally, fluorescence characterization studies showed that both complexes exhibited reduced fluorescence compared to H 2 L.