Sulfate Donor Based Dinuclear Heteroleptic Triple-Stranded Helicates from Sulfite and Ditopic Nitrogen Donor Ligands and Their Transformation to Dinuclear Homoleptic Double-Stranded Mesocates

Abstract

Sulfate donor based supramolecular coordination complexes [{ fac-Re(CO)}(μ-SO)(L ){ fac-Re(CO)}] (1-3) were obtained using ditopic N donors (L ; n = 1-3), NaHSO, and Re(CO) in a one-pot, multicomponent, coordination-driven self-assembly approach, in which SO becomes oxidized to SO during the reaction and acts as a building framework. Complexes 1-3 were characterized using IR, ESI-TOF-MS, and H NMR spectroscopy. The structures of complexes 1-3 were confirmed using single-crystal X-ray diffraction analysis. The transformation of the dinuclear heteroleptic triple-stranded helicate to the dinuclear homoleptic double-stranded mesocate [{Re(CO)Cl}(L )] (L = L, L, L; 4a-6a) was achieved by the addition of BaCl. The direct treatment of Re(CO)X (X = Cl, Br) with L/L/L yielded the dinuclear homoleptic double-stranded helicates [{Re(CO)X} (L )] (4b-6b and 7-9).

Rhenium–Pyrazolyl-Based Figure-Eight- and Z-Shaped Metallocycles: Self-Assembly, Solid-State Structures, Dynamic Properties in Solution, and Competitive Ligand-Induced Supramolecular Transformations into Rhenium-Pyridyl/-Benzimidazolyl/-Phosphine-Based Metallocycles/Acyclic Complexes

“…The design and synthesis of metallocycles such as cages, helicates, and simple-to-complex topological architectures via coordination-driven self-assembly have been gaining significant attention owing to their potential applications in materials and medicinal fields. − Further, new aesthetically appealing molecular architectures including intricate topological metallocyclic architectures such as metallo-links (a series of interlocked metallocyclic rings where at least one ring has to be broken to separate them) and metallo-knots similar to those found in nature can be prepared using the self-assembly. − Among various topologies, “figure-eight” architecture is one of the elegant self-assembled structures, which is found in natural systems such as Lissoclinamide 7, the recombinant structure of circular DNA and marine alkaloid. , However, very few examples of “figure-eight”-shaped metallocycles are known until now. − The design and synthesis of “figure-eight”-shaped metallocycles and other metallocyclic architectures using various metal precursors and organic building units are important in the development of the field, which might yield molecules having various potential applications in the near future. Among the few metal ion-based coordination-driven approaches, the fac -[Re(CO) 3 ] core-based self-assembly method is one of the methods to construct neutral homoleptic and heteroleptic metallocycles, which have potential applications in the field of host–guest encapsulation, catalysis, selective reactivity, sensing, and as bioactive agents. − Although a considerable number of synthetic principles for the preparation of various sizes and shapes of fac -[Re(CO) 3 ] core-based metallocycles are currently available, synthetic approaches for preparing “figure-eight” topology, complex-knot, and complex-link-shaped metallocycles are scarce. In addition to the metal core, the nature of the ligand is crucial to obtaining com...…”

Heteroleptic Triple-Stranded Metallosupramolecules with Hydrophobic Inner Voids

“… 25 The formation of helicate or mesocate greatly depends on the nature of the metal and ligands 26 , 27 and sometimes on additional information introduced by template 28 or reaction conditions. 29 For ligands, the stereoselectivity of the self-assembly can be influenced by ligand rigidity, ligand geometry, and the number of methylene units in the alkyl spacers. 30 Immense works have been done for the investigation of helicate and mesocate compounds, but the future will show the merit of studying this fascinating topic of metallosupramolecular chemistry.…”

“…If two units of opposite configurations are combined, an achiral mesocate is formed . The formation of helicate or mesocate greatly depends on the nature of the metal and ligands , and sometimes on additional information introduced by template or reaction conditions . For ligands, the stereoselectivity of the self-assembly can be influenced by ligand rigidity, ligand geometry, and the number of methylene units in the alkyl spacers .…”