Direct coordination of metal ions to cucurbit[n]urils

Abstract

Cucurbit[n]urils (Q[n]) are promising ligands for the coordination of metal ions, metal complexes or clusters, and form various Q[n]-based complexes. Among the Q[n] complexes, those formed by direct coordination between Q[n]s and metal ions are particularly important. The direct coordination of metal ions to cucurbit[n]urils leads to the formation of Q[n]-based molecular capsules, tubular polymers and molecular bracelets, which could have nanoscale applications in drug delivery, molecular devices and new materials. metal ions, cucurbit[n]urils, direct coordination, molecular capsules, tubular polymers, molecular bracelets Citation: Cong H, Zhu Q J, Xue S F, et al. Direct coordination of metal ions to cucurbit[n]urils.Recently, much attention has focused on the design and synthesis of interlocked molecules [1-4], tubular architectures with controlled sizes and shapes [5][6][7], and porous coordination polymers with metal organic frameworks (MOFs) [8][9][10][11][12]. These materials have attracted considerable interest for applications as molecular sieves, ion sensors, fluidic transport systems, and in the field of nanotechnology [13][14][15][16][17][18]. One class of macrocycle capable of building such molecular architectures is the cucurbit[n]urils. Cucurbituril and its homologs have shown to be a promising class of ligand that is useful as an organic building block [19][20][21][22][23][24]. This is largely because of the two open portals of these macrocycles, which creates a unique cavity rimmed with carbonyl groups (Figure 1). Cucurbit[n]urils (Q[n]) readily include different organic molecules to form various hostguest inclusion complexes, pseudorotaxanes, catenanes, and molecular knots [25-34]. In addition, they also readily coordinate to metal ions, such as alkali and alkaline earth metal ions [35-40], transition metal ions [41-43], lanthanide metal ions, uranyl ions and their complexes [44-51] or clusters [52-61]. These interactions result in the formation of various exclusion complexes, one-dimensional (1D) or poly-dimensional architectures and frameworks. The development of Q[n] chemistry has been reviewed elsewhere [62-65]. Among the known Q[n] inclusion and exclusion complexes is an important class of compound in which the metal ions coordinate directly to the carbonyl oxygen atoms of the Q[n]s. This direct coordination leads to the formation of Q[n]-based molecular capsules, tubular polymers and molecular bracelets, which have potential nanoscale applications in drug delivery, molecular devices and new materials. In this review, we will describe direct coordination of metal ions to Q[n]s, and their supramolecular assemblies based on the research of both other groups and our group.Figure 1 Structure of cucurbit[n]urils.

Cucurbit[n]uril-based coordination chemistry: from simple coordination complexes to novel poly-dimensional coordination polymers

“…19,43 In particular, they have led Scherman and co-workers to published their first paper on Q[n] chemistry in Science in 2012. [38][39][40][41] In fact, the establishment of Q[n] chemistry started with Q[n]-based coordination chemistry because the structural characteristics of the first-characterized member of the Q[n] family, Q [6], was based on the determination of the complex of Q [6] molecules with Ca 2+ cations. However, few of them focus on Q[n]-based coordination chemistry or Q[n]-based host-guest/coordination chemistry.…”

“…[12][13][14][15][16][17][18][19][34][35][36][37] On the other hand, the interaction of Q[n] with various metal ions established the Q[n]-based coordination chemistry as an increasingly important area in Q[n] chemistry. 20,[38][39][40][41] A combination of Q[n]-based host-guest chemistry and coordination chemistry creates a different branch in Q[n] chemistry: Q[n]-based host-guest/coordination chemistry 42 (Scheme 2). There have been significant developments in Q[n] chemistry since 1981.…”

Complexation of trivalent metal cations (Al3+, Ga3+, In3+, La3+, Lu3+) to cucurbiturils: a DFT/SMD evaluation of the key factors governing the host–guest recognition

“…Favorable binding of metal ions to the open macrocycle portals results in soluble highly stable metal-CB[n] complexes and supramolecular architectures. 12,13 It can be inferred that metal-CB[n] coordination significantly expands the field of their application, as this process results in the formation of various novel constructs such as molecular capsules, 12,14 tubular polymers, 15,16 and molecular ''jewelry''bracelets 17 and necklaces. 18 Therefore, understanding (at the atomic level) the mechanism of cucurbit[n]uril-metal complex formation is of particular interest.…”

H3 BTC-Induced Supramolecular Assembly Based on Cucurbit[6]uril: Possible Application for Sensing Small Molecules

“…Cucurbit[n]urils (CB[n]s) are ideal building blocks for the construction of supramolecular assemblies, which have attracted remarkable attention in supramolecular chemistry and coordination chemistry in recent years, because of their rigid hydrophobic cavity and two identical carbonyl fringed portals . They readily coordinate with metal ions or form various host‐guest inclusion complexes to provide supramolecular frameworks , . In recent years, there has been a trend towards introducing a third species (such as organic or an inorganic molecule) into metal‐CB[n] systems as a “structure inducer” or trigger, in order to obtain novel supramolecular assemblies, which the properties and functionalities are often superior to those obtained in the absence of such agents .…”