Spheroid Metallacycles and Metallocavitands with Calixarene- and/or Cleft-Shaped Receptors on the Surface

Abstract

Flexible hexatopic ligands, 1,2,3,4,5,6-hexakis(1H-naphtho[2,3-d]imidazol-1-ylmethyl)benzene (L(2)) and 1,2,3,4,5,6-hexakis(4,5-diphenylimidazol-1-ylmethyl)benzene (L(3)), containing six neutral naphthanoimidazolyl and 4,5-diphenylimidazolyl N donors were synthesized and used to assemble M6L6L'-type [M = Re(CO)3, L = anionic angular rigid NN donors, and L' = flexible hexatopic N donors] spheroid metallacycles. These molecules with a diameter of ∼17 Å were obtained from Re2(CO)10, H-L (imidazole, benzimidazole, and naphthanoimidazole), and L' [1,2,3,4,5,6-hexakis(benzimidazol-1-ylmethyl)benzene (L(1)), L(2), and L(3)] in a one-step process. Ligands L(2) and L(3) were characterized by elemental analysis, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and (1)H NMR spectroscopy. Metallacycles 1-5 were characterized by elemental analysis, ESI-TOF-MS, Fourier transform infrared spectroscopy, and single-crystal X-ray diffraction analysis. Molecules 1, 2, and 4 can be considered as metallocavitands and contain multiple solvent-accessible receptors, i.e., two metallocalix[3]arene units and six/four calix[4]arene-/cleft-shaped receptors, on the surface. Guests such as acetone molecules could be accommodated in the calix[4]arene/cleft-shaped receptor of the metallocavitands.

Rhenium‐Carbonyl‐Based Supramolecular Coordination Complexes: Synthesis, Structure and Properties

“…Six calix[4]arene shaped exo‐cavities are present on the circular space that can accommodate small molecules. Solid state structures of 30a–30c confirm the ability of these molecules to accommodate guest molecules in its exo –calixarenes shaped cavities ,…”

“…Solid state structures of 30a-30c confirm the ability of these molecules to accommodate guest molecules in its exo-calixarenes shaped cavities. [107,108] Ligand modification allowed cavity alteration on these spheroid metallocavitands by introducing metallocalix [3]arene and calix [4]arene type receptor sites at the curvature of the spherical surface with acetone molecules occupying these convex cavities. In these structures, the size of the anionic motif and the neutral multitopic donor affected the overall size of the supramolecule as well as the geometry of the exocyclic convex cavity, thus providing a control over the number, size and position of the cavity at the exterior surface of the metallacyclic structure.…”

“…The first report on octanuclear metallacycle described Figure 26. Cavity modified molecular spheroids [108] Scheme 7. Re(I)-based double metallocavitand 31.…”

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 c...…”

A Straightforward Strategy for Constructing Zirconium Metallocavitands

“…Metallocavitands (MCs), an emerging class of functional cavernous compounds, have attracted considerable interest in the past decades due to their structural beauty and their promising applications in chemical sensing, separation, host–guest chemistry, molecular reactors, and so on. − Varieties of MCs based on different metal ions/clusters and organic linkers have been well developed. − These MCs can be specifically divided into six categories based on either a macrocycle-templating or self-assembly strategy, including flexible macrocycle-templated, Schiff base macrocycle-templated, noble metal N-donor assembled, paddlewheel, miscellaneous metallacrown, and organometallic half-sandwich MCs . In particular, the organometallic half-sandwich MCs with distinct structural characteristics, in which metal centers were blocked by cyclopentadienyl (Cp), pentamethylcyclo-pentadienyl (Cp*), or arene (C n H m ) ligands, − are amenable to form discrete structures.…”