Cucurbiturils as Effectors on the Self-Assembly of Pd(II) and Pt(II) Metallacycles

Abstract

Four bidentate, dicationic ligands (L1 2+ −L4 2+ ) were prepared and investigated as guests for binding by the cucurbit[7]uril (CB[7]) host and structural components for metal (Pd and Pt)-coordinated self-assembly into metallacycles. In aqueous solutions, all the ligands were found to form stable complexes of variable stoichiometries with CB[7], and only one (L2 2+ ) failed to self-assemble, induced by the presence of suitable Pd or Pt complexes, into metallacycles. Exposure of the Pd-based metallacycles to CB[7] led to their disassembly at room temperature, while the Pt-based metallacycles remained stable under these conditions. However, heating of the Pt metallacycles in the presence of CB[7] also led to their disassembly. This interplay between the interactions in aqueous media of the L1 2+ , L3 2+ , and L4 2+ ligands with the CB[7] host and Pd (or Pt) complexes suggests the possibility of using these or related systems for controlled drug delivery applications.

Near-infrared fluorescence probes based on disassembly-induced emission pyrene derivatives

“…After CB [8] encapsulates PYN, the 1 H-NMR spectrum of PYN changes accordingly due to the de-shielding effect of CB [8]. 43 Therefore, the analysis of 1 H-NMR spectra can provide crucial information about the binding modes of the host-guest complexes, including the determination of their binding sites. The 1 H-NMR spectra of pure CB [8], PYN and PYN@CB [8] in D 2 O are shown in Fig.…”

Coordinating nature of M6L12 double-stranded macrocycles: co-ligand competition of perchlorate, water, and acetonitrile depending on metal(ii) ions

“…[1][2][3][4][5][6][7][8][9][10] Thus, construction of new functional metallacyclic ensembles is a particularly coveted goal, [11][12][13][14][15][16][17] since their specific functions are comparable with those of organic macrocycles such as crown-ethers, cyclodextrins, calixarenes, and cucurbiturils. [18][19][20][21][22][23][24] Self-assembly reactions of metal cations with appropriate hemi-circular bidentate ligands can provide opportunities for efficient use of metallacyclic hosts as guest receptors. [25][26][27][28][29][30] The coordinating nature, including the local geometry of the central metal cations, is an important factor for the formation of desirable coordination macrocycles.…”

Water‐soluble Self‐assembled {Pd84}Ac Polyoxopalladate Nano‐wheel as a Supramolecular Host

“…[11][12][13][14][15][16] Macrocyclic hosts most commonly studied include crown ethers, metal-organic cages, cyclodextrins, cucurbiturils, calixarenes and resorcinarenes. [17][18][19][20][21] The presence of transition metals in these structures allows a greater degree of control over molecular shape, binding sites and chemical selectivity due to the preferred coordination geometry the metal adopts on complexation with a specific ligand. [22,23] Metallacycles, cages and MOFs have all attracted attention, whilst the use of polyoxometalates is relatively unexplored.…”

“…Applications of host‐guest systems include sensing, drug delivery vehicles, molecular machinery and catalysis [11–16] . Macrocyclic hosts most commonly studied include crown ethers, metal‐organic cages, cyclodextrins, cucurbiturils, calixarenes and resorcinarenes [17–21] . The presence of transition metals in these structures allows a greater degree of control over molecular shape, binding sites and chemical selectivity due to the preferred coordination geometry the metal adopts on complexation with a specific ligand [22, 23] .…”