1. Symmetry Decrease between Self-Assembled Circular TiO 4 N 2 -Based Helicates
- Author
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Brice Kauffmann, Pierre Mobian, Marc Henry, Laurent Barloy, Georges Khalil, Alain Chaumont, Nathalie Kyritsakas, Chimie de la matière complexe (CMC), and Université de Strasbourg (UNISTRA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
chemistry.chemical_classification ,010405 organic chemistry ,Ligand ,Chemistry ,Crystal structure ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Coordination complex ,Inorganic Chemistry ,Crystallography ,Transition metal ,Octahedron ,Proton NMR ,Molecule ,[CHIM]Chemical Sciences ,Self-assembly - Abstract
International audience; A multicomponent self-assembly reaction involving a bis-biphenolato ligand (LH 4), a 2,2′-bipyrimidine chelate substituted by two (anthryl)vinyl moieties (bAnt) and Ti(OiPr) 4 was investigated. An assembly {[Ti 3 (L) 3 (bAnt) 3 ]}, composed of three homochiral TiO 4 N 2 nodes, was characterized as being the ther-modynamically-end product. The crystal structure of this circular helicate highlighted an absence of symmetry for this compact compound. DOSY 1 H NMR indicated that the nuclearity Self-assembly processes driven by transition metals are highly powerful methods to access complex architectures. [1] These self-assembled architectures, which are impossible to obtain through conventional step-by-step synthetic strategies, result from the mutual programmed recognition between metal ions and organic ligands. An impressive number of rationally designed helicates, [2] cages, [3] squares, [4] spheres, [5] grids, [6] top-ological non-trivial molecules [7] and other architectures [8] have been reported so far. Whereas the main interest in self-assembly is focused on the thermodynamically-end products, the characterization and the isolation of intermediate architectures generated during the self-assembly is rather scarce. [9] This is mainly linked to the low energy barriers existing between transient compounds. However, it is an important issue since the full identification of intermediates could provide fundamental information to apprehend some mechanistic aspects of a self-assem-[a] Dr. 3527 observed in the solid state for [Ti 3 (L) 3 (bAnt) 3 ] was maintained in solution. An intermediate formulated as [Ti 4 (L) 4 (bAnt) 4 ] was isolated. The structural analysis revealed that [Ti 4 (L) 4 (bAnt) 4 ] was a symmetrical circular hollow helicate composed of four homochiral metallovertices. This study, supported by DFT calculation , brought some evidences on the sequences and the reasons leading to the symmetry decrease for this self-assembly process. bly reaction. Therefore, the isolation and characterization of one or several intermediates produced in the course of a self-assembly process is a challenging and major task. [10] Over the latest decade, our group has developed a tita-nium(IV)-based coordination chemistry involving a bis-biphe-nolato ligand named as LH 4 as shown in Figure 1, leading to neutral self-assembled helical structures. [11,12] By following a multicomponent self-assembly approach with the 2,2′-bipyrimi-dine (bpym) chelate, a circular trinuclear bowl-shaped helicate constructed around octahedral TiO 4 N 2 motifs, [Ti 3 (L) 3 (bpym) 3 ], was generated. [13] This study also highlighted the formation of a tetranuclear intermediate {[Ti 4 (L) 4 (bpym) 4 ]} detected only by mass-spectrometry and 1 H NMR. Figure 1. Structure of LH 4 and bAnt.
- Published
- 2020
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