Synthesis and Conformational Analysis of Constrained Ethylene-Bridged Bis(hydroxylamino-1,3,5-triazine) Compounds as Tetradentate Ligands; Structure of Rigid Dinuclear Ti(IV) Complex

Ethylene-bridged bis(hydroxylamino-1,3,5-triazine) compounds, that may serve as tetradentate ligands, were synthesized in three steps from 2,4,6-trichloro-1,3,5-triazine. These compounds demonstrate different rotation restrictions around the CAr−N bonds due to their distinctive electronic structure as apparent from their resonative contributors. A dinuclear complex Ti2(μ-L)2(OiPr)4 (L = bis(triazine)) was synthesized where each octahedral Ti(IV) center is also bound to two isopropoxo groups. The complex rigidity is manifested in a significant deviation from planarity of the aromatic systems, and relatively long Ti−N bonds compared to mononuclear analogous complexes. Increased ligand lability in this complex brings about diminished cytotoxicity toward colon and ovarian cells.