β-Cyclodextrin Phenolphthalein Supramolecular System as Probe for Detecting Trace Tricyclazole by Competitive Host–Guest Inclusion

Supramolecular Nanohelix Fabricated by Pillararene-Based Host–Guest System for Chirality Amplification, Transfer, and Circularly Polarized Luminescence in Water

Strong thickening performance and mechanism of supramolecular system constructed by β-cyclodextrin polymer included adamantane polymer

Macrocyclic hosts can bind appropriate guests in endo‐cavity or exo‐wall modes to yield Host–Guest cocrystals via weak intermolecular forces. Contrary, it remains challenging to achieve their nonmacrocyclic partners with high‐efficiency fluorescence even lasing due to profound adaptive behaviors during guest inclusion. Here, a variety of low dispersity 1D and 2D assemblies made of a sterically demanding perylenediimide derivative (PDI) host and diverse aromatic guests are realized. Depending on the types and the substituted groups of aromatic guests, these Host–Guest microcrystals show high‐efficiency solid‐state emissions ranging from orange to near‐infrared (NIR). Interestingly, either electron‐deficient or electron‐rich guests can adapt to the cavity of the nonmacrocyclic PDI host in diverse geometries and orientations. Theoretical analysis indicates that the long‐wavelength emissions stem from local or charge‐transfer excited states and the Host–Guest Donor–Acceptor cocrystals are stabilized largely by dispersion forces. The binding of appropriate π‐electron guests makes the PDI‐derived Host–Guest microcrystals function as microscale lasers with low lasing thresholds. The rational creation of these nonmacrocyclic Host–Guest Donor–Acceptor cocrystals offers new insights for developing new crystal structures and high‐efficiency optoelectronic devices.

Developing more extensive methods to understand the underlying structure-property relationship of mechanochromic luminescent molecules is demanding but remains challenging. Herein, the effect of host-guest interaction on the mechanochromic properties of organic molecules is illustrated. A series of pyridinium-functionalized triphenylamine derivatives show bathochromic-shifted emission upon mechanical stimulation. These derivatives bind to cucurbit[8]uril to form homoternary host-guest inclusion complexes through host-stabilized intermolecular charge transfer interactions. Remarkably, the homoternary complexes exhibit longer emission than that of free guests in the solid state (even longer than ground guests), and a further bathochromic-shifted emission is observed upon grinding. Additionally, a heteroternary complex constructed through the encapsulation of pyrene (donor) and pyridinium (acceptor) guest pair in cucurbit[8]uril also displays the mechanochromic luminescent property. This work not only discloses the effect of host-guest inclusion on the mechanochromic property of organic molecules, but also provides a principle and a facile way to design the sequentially red-shifted mechanochromic materials.

Development of a liquid crystal-based sensor utilizing EDTA-cyclodextrin polymer for real-time optical detection of methylene blue in natural water samples

A new topological parameter for monitoring subtle aggregation events in host–guest inclusion processes

Fluorescence enhancement of cyanine/hemicyanine dyes with adamantane as an auxochrome through host–guest inclusion with methylated cyclodextrin in water

Sensitive detection of α-amylase based on host–guest inclusion system of γ-cyclodextrin and dansyl-derived diphenylalanine

We report an original strategy towards supramolecular assembly of reversible comb-shaped polymers in aqueous solution through β-cyclodextrin–adamantane (β-CD–Ada) host–guest inclusion. Ada-functionalized poly(acrylic acid) grafts were generated by RAFT polymerization mediated by an adamantane-α-functionalized RAFT agent. A β-CD-grafted backbone was obtained by a two-step procedure: alkyne-functionalized backbones were first generated by RAFT polymerization of trimethylsilyl propargyl methacrylate and subsequently converted in a host system by CuAAC with azide-functionalized β-CD. The self-assembly between a β-CD-grafted polymer backbone and Ada-functionalized grafts was highlighted by 1H 2D NOESY NMR in D2O and by DLS. The reversible character of the host–guest association between the complementary macromolecular blocks was demonstrated by DLS through the addition of competing free β-CD.

Pillar[n]arenes are a relatively new class of macrocyclic host molecules which have not been extensively studied for their ability to form inclusion complexes. The properties and host–guest inclusion complexes of dimethoxypillar[5]arene (DMPill[5]) hosts with the polarity-sensitive fluorescent probes 8-anilinonaphthalene-1-sulfonic acid (1,8-ANS) and 2-anilinonaphthalene-6-sulfonic acid (2,6-ANS) as guests were investigated in nonaqueous solvents via fluorescence spectroscopy. The binding properties of DMPill[5] were found to depend significantly on the shape of the guest molecule, as well as on the properties of the solvent. Formation of host–guest inclusion complexes of DMPill[5] with these two fluorescent ANS guests occurred in the polar aprotic solvents acetonitrile, acetone, and tetrahydrofuran. Fluorescence titration experiments were performed to determine the nature and strength of the complexation. In the case of 1,8-ANS, 1:1 host–guest complexation was observed in all three solvents, with average binding constant K values of 408, 1000 and 5500 M−1 in acetone, acetonitrile, and tetrahydrofuran, respectively. This large dependence of the binding constant on solvent provides insight into the nature of the binding in these complexes. In the case of 2,6-ANS, 2:1 host–guest complexation was observed; this difference with 1,8-ANS was explained in terms of the shape and size of these two isomeric guests. These results show that DMPill[5] is an excellent host for these neutral aromatic guests, and shows strong binding abilities even in these nonaqueous solvents. The strength (or lack) of binding in different solvents was found to be dependent on a range of factors beyond solvent polarity, including guest and solvent shape and size, and most importantly, specific solvent–solute interactions.

The mechanism of selectivity by enclathration of four amides, N-methylformamide (NMF), dimethylformamide (DMF), N-methylacetamide (NMA) and dimethylacetamide (DMA), has been investigated by employing a bulky, flexible host. We measured the two-component selectivity curves for a mixture of amides, whose proportions in the crystals were determined by 1H NMR spectroscopy. The crystal structures of the single guest inclusion compounds were elucidated and analyzed. The subtle changes in the torsional flexibility of the host were correlated to the selectivity. The packing factor, which represents the occupied vs. available space by the guest in the crystal structures correlates with the measured selectivities.

Fluorescence Correlation Spectroscopy (FCS) is a powerful single molecule technique for the study of the stability and the association dynamics of supramolecular systems and, in particular, of host–guest inclusion complexes. With FCS the host–guest binding equilibrium constant is determined analysing the variation in the diffusion coefficient of the fluorescent guest or host with no need for a change in the photophysical properties of the fluorescent probe. FCS gives also access to the association/dissociation rate constants of the host–guest inclusion providing that the fluorescence intensity of host or guest changes upon complexation. These rate constants can be compared with that of a diffusion-controlled process estimated from the same FCS experiment allowing for a better understanding of the association dynamics. The results show that cyclodextrin cavities act as “hard” cages which put geometric and orientational restrictions on the inclusion of a hydrophobic guest, whereas micelles behave as “soft” cages without geometrical requirements. In our contribution to this special issue we review briefly the application of FCS to the study of host–guest inclusion complexes with an emphasis on practical aspects and relevant bibliographic references.

Despite the thriving interest in the aqueous complexation properties of carboxylated pillar[6]arene, its solid state supramolecular chemistry has remained a mystery. Here, overcoming challenging crystallogenesis, we report the first crystallographic authentication of carboxylated pillar[6]arene in the form of two host–guest inclusion complexes with methyl viologen and pentamidine. The key to the successful crystallization of carboxylated pillar[6]arene is the mixed ionization state of its 12 carboxylic substituents. The deprotonation of several but not all substituents enables intermolecular hydrogen bonding and, as a result, “gluing” and crystallization of pillar[6]arene complexes with the aid of carboxylic-carboxylate, carboxylic-carboxylic, and amidinium-carboxylate supramolecular synthons. Single crystal X-ray diffraction analysis revealed that upon guest inclusion pillar[6]arene adopts a quasi-pentagonal shape rather than the expected hexagonal shape. The squeezed quasi-pentagonal conformation of the six-membered macrocycle is stabilized by two intramolecular hydrogen bonds between pillar[6]arene substituents. Moreover, the distinctive deviation of the macrocycle from hexagonal shape stays operative in the solution/gas phase as concluded from ion mobility mass spectrometry (IM-MS) studies and theoretical calculations. These results provide the first insight into how to gain control over the conformation of flexible pillar[6]arene with a view of solid state design of more advanced supramolecular host–guest structures.

Synergistic thickening mechanism of surfactants and supramolecular inclusion systems

Light and host–guest inclusion mediated salmon sperm DNA/surfactant interactions