Molecular Re^I Cages: Structural and Luminescent Properties

Abstract

Versatile building block [{Re(CO) } (C N S )] (1 a; C N S =cyanurate trianion) reacts with linear dipyridyl ligands [i.e., pyrazine (pz), 4,4'-bipyridine (bpy), 1,2-bis(4-pyridyl)ethylene (bpe), bis(4-pyridyl)acetylene (bpa), and 1,4-bis(pyridyl-4-ylethynyl)benzene (bpb)] and a tripyridyl ligand [1,3,5-tris(4-pyridylethynyl)benzene (tpb)] to afford a series of molecular cages [{Re(CO) } (L) (C N S ) ] [L=pz (2), bpy (3), bpe (4), bpa (5), bpb (6)] and [{Re(CO) } (tpb) (C N S ) ] (7) under solvothermal conditions. Various structural dimensions and motifs can be systematically tuned and obtained by using different dipyridyl and tripyridyl ligands in the reactions. The molecular cages of hexanuclear complexes 2-6 containing dipyridyl ligands feature interesting trigonal-prismatic structures with different dimensions. Furthermore, nonanuclear complex 7 has a novel triangular-star structure, and three benzene rings of tpb ligands form a triple-decker arrangement with significant π⋅⋅⋅π interactions having distances of 3.490(1) and 3.528(1) Å. In addition, molecular cages 1-3 and 5-7 exhibit luminescence in the solid state, and their luminescent properties were also studied.

Fluorine-Assisted Self-Assembly Approach for Tubular Architecture of Cyclic Trinuclear Rhenium(I)-Fluorothiabendazolate Complex

“…The complexes 1 – 3 are air, moisture stable, and are soluble in DMSO, CH 3 COCH 3 , and CH 3 CN. The AT-IR spectra of 1 – 3 displayed two strong bands in the region 1874–2022 cm –1 (Figures S1–S3), corresponding to the fac -[Re­(CO) 3 ] motif. − The ESI-MS spectra of the complexes displayed molecular ion peak ( m / z = 1411.9047 for [ 1 + H] + , 1560.9608 for [ 2 – 2H] + , and 1518.9047 for [ 3 – 2H] + ) and their isotopic distribution peaks match well with the theoretical values (Figures S4–S6).…”

“…The design and synthesis of simple to complex supramolecular coordination complexes (SCCs) is increasing tremendously due to their potential utility in various fields. − Among various SCCs, fac -[Re­(CO) 3 ] core-based SCCs are one of the important classes of complexes having potential applications in molecular recognition, catalysis, sensors, bioimaging, and as anticancer agents. − Due to their significance, different shapes and sizes of Re­(I) SCCs including mono/di/trinuclear cycles, helicates, mesocates, squares, rectangles, tetrahedrons, spheroids, and prisms have been emerging continuously. − Currently, efforts are being directed toward incorporating functional groups on the cyclic framework of SCCs to construct higher-order superstructures and functional materials. The design of a ligand with precisely arranged donors and functional groups plays a vital role in deciding the structure and properties of SCCs.…”

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...…”