Bent 1,10-Phenanthroline Ligands within Octahedral Complexes Constructed around a TiO₄N₂ Core

The synthesis of monomeric octahedral complexes constructed around a TiO₄N₂ core bearing neocuproine derivatives is detailed. These architectures follow the [Ti(1)₂(N-N)] general formulas, where 1 is the 6,6'-diphenyl-2,2'-biphenolato ligand and N-N is a 1,10-phenanthroline derivative. Single-crystal analysis revealed that the neocuproine-based ligands within these architectures adopt a nonplanar geometry. The distortion of these aromatic diimine systems has been quantified through measurement of a torsion angle (α) and a dihedral angle (β) defined by two planes within the aromatic diimine molecule (π₁ and π₂), permitting one to evaluate the twisting and bending of a coordinated nitrogen ligand, respectively. Next, the scope of this investigation was extended to the synthesis of a dimeric architecture, [Ti₂(1)₄(3)], where 3 is the 5,5'-bis(neocuproine) ligand. Again, a strong distortion of the neocuproine fragments was characterized in the crystalline state for such a complex. The UV-visible properties of these complexes were interpreted with the help of time-dependent density functional theory calculations. The solution behavior as well as good hydrolytic stability of these species has been established.