Large M₄L₄ (M = Al(III), Ga(III), In(III), Ti(IV)) Tetrahedral Coordination Cages:  an Extension of Symmetry-Based Design

Abstract

As an extension to a rational design for the formation of self-assembled coordination cages, the syntheses for very large M4L4 tetrahedra based on a hexadentate 3-fold symmetric ligand (1,3,5-tris(4'-(2' ',3' '-dihydroxybenzamido)phenyl)benzene (H6L2)) are described. Four tetrahedral M4L2(4) assemblies (M = Al(III), Ga(III), In(III), Ti(IV)), with cavity sizes of around 450 A3, have been characterized by elemental analysis, NMR spectroscopy, and high-resolution electrospray mass spectrometry. Differences in chiral resolution and dynamic behavior of host-guest interactions with previously reported tetrahedral M4L(N)6 and M4L1(4) architectures are highlighted for the ligands 1,5-bis(2',3'-dihydroxybenzamido)naphthalene (H4L(N)) and 1,3,5-tris(2',3'-dihydroxybenzamido)benzene (H6L1). An even larger 3-fold symmetric ligand, 1,3,5-tris(4'-(2' '',3' ''-dihydroxybenzamido)-1',1' '-biphenyl)benzene (H6L3) has been prepared but, due to increased flexibility and deviation from the intended 3-fold symmetry, does not undergo self-assembly to form the M4L3(4) structure.

Tris(pyridylmethylamino)cyclotriguaiacylene Cavitands: An Investigation of the Solution and Solid‐State Behaviour of Metallo‐Supramolecular Cages and Cavitand‐Based Coordination Polymers

“…[43] This approach to increasing the internal dimensions of [M 4 L 4 ] tetrahedra has also been described by Albrecht et al [40] These structures are of similar dimensions to the stellated tetrahedron. Raymond and coworkers noted that increased conformational flexibility of the ligands somewhat limits the quest for structures with larger internal cavities.…”

Symmetry Driven Self-Assembly of Metallo-Supramolecular Architectures

“…71,72 Our approach was to use triangular ligands with catechol corners and octahedrally coordinating metal ions to obtain tetrahedra. [73][74][75][76][77] In the investigations the problem was addressed, if the ligands have to be rigid and highly preorganized, or if flexible ligands also can be manipulated in such a way that they lead to the desired oligonuclear structure and not only to mononuclear complexes (Fig. 16).…”

Protonation of Tris(iminocatecholato) Complexes of Gallium(III) and Titanium(IV)

“…[3] Starting with rigid ligand systems like 1-H 6 , we easily obtained the desired container molecule [Ti 4 1 4 ] 8-, which shows interesting host-guest chemistry.…”