Titanium(iv)-based helicates incorporating the ortho-phenylenediamine ligand: a structural and a computational investigation

Abstract

The multicomponent coordination chemistry involving Ti(OPr), the ortho-phenylenediamine ligand (opda) and 2,2'-biphenol-based proligands (LH and LH) is described. The proligands LH and LH incorporate two and three 2,2'-biphenol units linked with p-phenylene bridges (p-PLB) respectively. We demonstrate that this selected set of components allows the spontaneous formation of neutral double-stranded helicates. In particular, we report the X-ray crystal structure of a multicomponent helicate formed with L, named Ti(L)(opda). The molecular structure of the helicate shows two inequivalent L ligands. H NMR analysis at variable temperature highlights an intramolecular fluxional phenomenon for this species. An insight into this dynamic behaviour is obtained via the energy profiles of Ti(L)(opda) resulting from the full rotation of the p-PLB rings. Additionally, the thermodynamic parameters associated with the formation of the Ti(L)(opda) complex are modelled and discussed related to the ones linked to the formation of a related monomeric complex.

From monomeric complexes to double-stranded helicates constructed around trans-TiO4N2 motifs with intramolecular inter-ligand hydrogen-bonding interactions

“…This situation contrasts strongly with a related double-stranded helicate constructed around two cis-TiO4N2 motifs, where CH- interactions occur between the two central aromatic units belonging to L 2 . 22 These compounds are chiral owing to their inherent helicity. In these crystals, the P and M helicates are found in equal proportion since all these structures belong to centrosymmetric space groups.…”

“…20 Already, this approach has permitted to evaluate weak interactions in crystalline hydrogen bond networks 24 or Ti(IV)based helicates. 22 Therefore, a virtual 360 ° rotation of one nitrogen ligand along the Ti-N bond within a complex is performed. These interactions are estimated from two situations.…”

An Alternate [2×2] Grid Constructed Around TiO4N2 Units

“…Dinuclear Ti(IV)-based doublestranded helicates were obtained with monodentate [43] or bidentate nitrogen ligands. [44,45] Also, we have shown that the nuclearity of these architectures formed around TiO 4 N 2 units is tuned by the choice of the bidentate nitrogen ligand as a bowlshaped circular trinuclear helicate could be isolated by applying a multicomponent self-assembly reaction with the 2,2'-bipyrimidine chelate [46] (bpym) or bis((anthryl)vinyl)2,2'bipyrimidine. [47] Herein, we examine how a structural modification of the bis-biphenol could impact the structure and/or the nuclearity of the final aggregate.…”

“… [42] This pro‐ligand has proved to be ideally designed to afford several neutral helicate systems with Ti(O i Pr) 4 and nitrogen ligands. Dinuclear Ti(IV)‐based double‐stranded helicates were obtained with monodentate [43] or bidentate nitrogen ligands [44,45] . Also, we have shown that the nuclearity of these architectures formed around TiO 4 N 2 units is tuned by the choice of the bidentate nitrogen ligand as a bowl‐shaped circular trinuclear helicate could be isolated by applying a multicomponent self‐assembly reaction with the 2,2’‐bipyrimidine chelate [46] (bpym) or bis((anthryl)vinyl)2,2’‐bipyrimidine [47] .…”

Evaluation of the stereoselectivity for titanium(IV)-based coordination entities induced by the enantiopure diphenylethene-1,2-diamine ligand

“…Recently, our group has reported some examples of helicates built up around TiO 4 N 2 centers through a multicomponent self-assembly approach [11]. The components involved in these chiral systems are Ti (IV), achiral nitrogen bidentate ligands (ortho-phenylenediamine [11a] or 2,2-bipyrimidine [11b]) and a bis-biphenol pro-ligand where the two biphenol units are linked by a p-phenylene spacer (Fig.…”