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We have developed a tunable emissive supramolecular metallo-gel functionalized with lanthanide coordination bonds using a low molecular weight gelator 1 having terminal terpyridine. In the presence of Tb(III) and Eu(III) ions, the coordination of lanthanides to gelator 1 results in green and red emissive supramolecular metallogels, respectively. A supramolecular growth mechanism of 1-Tb that follows an isodesmic model has been observed, relying on delicate balances between non-covalent interactions. Furthermore, controlling the stoichiometry of lanthanide metal ions with respect to 1 : Tb(III) : Eu(III) leads to yellow and white light-emitting supramolecular bimetallic gels. [ABSTRACT FROM AUTHOR]

We report Ag(I)-coordinated supramolecular architectures of a terpyridine-based ligand bearing an alanine moiety and a trans- or cis-double bond in the alkyl chain in the presence of AgNO3 (0.5 and 1.0 equiv.) in H2O and dimethyl sulfoxide (DMSO) (1 : 4 v/v). In the presence of AgNO3, trans-L exhibited a helical ribbon structure while cis-L exhibited a linear ribbon structure. Furthermore, self-assembled trans-L exhibited a strong circular dichroism (CD) signal helicity. In contrast, self-assembled cis-L formed in the presence of 0.5 and 1.0 equiv. of AgNO3 showed a weak CD signal, indicating that the cis-L molecules did not form a helical arrangement in the supramolecular architecture. [ABSTRACT FROM AUTHOR]

Enantiomeric excess of chiral compounds is a key parameter that can influence their activity or therapeutic action. Current approaches to the rapid measurement of enantiomeric excess using 1H NMR is based on the formation of diastereomeric complexes between chiral analytes and a chiral host, leading to two species with no symmetry relationship. Here, we demonstrate that a gelator host system can provide a means to elicit distinct chemical shifts in the 1H nuclear magnetic resonance (NMR) of a mixture of diamines or monoamines depending on the corresponding enantiomeric excess of the guest mixture of chiral amines. These gelator hosts provide a unique example of NMR based assessment of the chirality and enantiopurity of guest amines. [ABSTRACT FROM AUTHOR]

Tetra-imidazole-appended p-phenylene-Cu(ii) doped nanofibrous membranes (IP-Cu-NMs) as portable chemoprobes were prepared using the electrospinning method. Fluorescence changes were observed upon dropping amino acids and proteins containing histidine residues onto the surface. IP-Cu-NMs prepared with 1.0 equivalent of Cu(ii) showed non-emissive properties, indicating that Cu(ii) induced the quenching with an aggregation-caused quenching (ACQ) effect. The fluorescence intensity of IP-Cu-NMs was enhanced approximately 25-fold upon dropping histidine onto the film, which is a “turn-on” system. In contrast, no significant fluorescence intensities were observed upon dropping other amino acids, such as valine, serine, phenylalanine, alanine, cysteine, lysine, leucine, asparagine, glutamic acid, glycine, methionine and arginine. IP-Cu-NMs achieved a low detection limit of 6.24 ppb observed by the fluorescence change. The results indicate that IP-Cu-NMs could be used to selectively detect histidine. More interestingly, the fluorescence of IP-Cu-NMs exhibited a strong emission with “turn-on” when proteins containing different numbers of His were dropped onto IP-Cu-NMs, and the intensity was dependent on the number of His residues in the protein. The enhanced fluorescence of IP-Cu-NMs with His could be recovered by treatment with Cu(ii) solution, suggesting the fluorescence reversibility of IP-Cu-NMs. Furthermore, this advanced convenient method was found to be valid up to 80% with excellent linearity for His detection over the range of 0–10 ppm in urine as a biological sample. [ABSTRACT FROM AUTHOR]

A cyclohexane-based ligand (1) as a triconnected linker forms a supramolecular gel in the presence of transition metal ions, particularly Cd2+ and Zn2+. 1 can also be gelated with cadmium counter ions such as NO3−, ClO4− and SO42−. The gels have been characterized by SEM, TEM, rheometry and single crystal X-ray crystallography. The Cd2+–cyclohexane-based ligand gel shows a fibrillar structure with diameters ranging from 20–50 nm. X-ray analysis revealed that 1 forms a 1D coordination polymer structure with the Cd2+ ion, with an octahedral structure. The rheological properties of the Cd2+–cyclohexane-based ligand gel were strongly dependent on the concentration of Cd2+. Furthermore, the xerogel 1 with Cd2+ acted as a base catalyst in the Knoevenagel condensation reaction. [ABSTRACT FROM AUTHOR]

A cyanurate derivative (1) possessing three carboxylic acid groups forms a two-component supramolecular hydrogel in the presence of 4,4-bipyridine (2) by intermolecular hydrogen-bonding interactions between –CH of 4,4-bipyridine (2) and –C=O of cyanurate (1) as well as between the N atoms of 2 and –COOH of 1. [ABSTRACT FROM AUTHOR]

2-(N,N-Dimethylamino)naphthalene-based probe 1 was found to exhibit a dramatic enhancement in fluorescence upon addition of Zn2+, but not with any other metal ions. Probe 1 as a chemoprobe enabled high-resolution fluorescence imaging of zinc ions in HeLa cells and Arabidopsis. [ABSTRACT FROM AUTHOR]

Amide-linked tripyridine derivatives 1, with a para-substituent, and 2, with a meta-substituent, were gelated in water or water–DMSO. The gelation capabilities of 1 and 2 were attributed to the cooperative effects of mainly CH–π and π–π stacking or strong intermolecular hydrogen bonding interactions between the amide groups. The fluorescence properties of gels 1 and 2 were dependent on the binding strength of the π–π stacking. [ABSTRACT FROM AUTHOR]

Recently, cooperative supramolecular polymerization has garnered considerable attention due to its significant potential for enabling controlled chain-growth polymerization, which offers a route to achieving a well-defined degree of polymerization and low polydispersity. In this study, we synthesized two distinct alkynylplatinum(ii) complexes, one bearing a saturated long alkyl chain (Pt-Sat-C18) and another containing a diacetylene moiety within a long alkyl chain (Pt-DA-C25). Spectroscopic analyses revealed that Pt-Sat-C18 undergoes supramolecular polymerization via an isodesmic pathway, while Pt-DA-C25 assembles cooperatively. Intriguingly, the mechanism of supramolecular copolymerization could be tuned by varying the composition ratios: transitioning from an isodesmic to a cooperative pathway was achieved by increasing the proportion of Pt-DA-C25. Moreover, UV irradiation prompted a shift from an isodesmic to a cooperative assembly mechanism. Morphologically, self-assembled Pt-Sat-C18 resulted in left-handed fibrillar structures, whereas Pt-DA-C25 led to left-handed tubular assemblies. Supramolecular co-assembly further revealed helical ribbon or tubular structures. Photoluminescent properties were also observed, with emission spectra centered at approximately 650 nm, attributed to the formation of excimer species facilitated by strong Pt⋯Pt interactions. To elucidate the mechanisms underlying these supramolecular polymerizations, temperature-dependent UV-visible spectroscopy was conducted during the cooling/heating processes, and thermodynamic parameters for both isodesmic and cooperative pathways were quantitatively assessed through curve fitting., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The study of chiral self-sorting is extremely important for understanding biological systems and for developing applications for the biomedical field. In this study, we attempted unprecedented chiral self-sorting supramolecular polymerization accompanying helical inversion with Ag + in one enantiomeric component. Bola-type terpyridine-based ligands ( R -L 1 and S -L 1 ) comprising R - or S -alanine analogs were synthesized. First, R -L 1 dissolved in DMSO/H 2 O (1 : 1, v/v) forms right-handed helical fibers (aggregate I) via supramolecular polymerization. However, after the addition of AgNO 3 (0.2-1.1 equiv.) to the R -L 1 ligand, in particular, it was found that aggregate II with left-handed helicity is generated from the [ R -L 1 (AgNO 3 ) 2 ] complex through the [ R -L 1 Ag] + complex via the dissociation of aggregate I by a multistep with an off pathway, thus demonstrating interesting self-sorting properties driven by helicity and shape discrimination. In addition, the [ R -L 1 (AgNO 3 ) 2 ] complex, which acted as a building block to generate aggregate III with a spherical structure, existed as a metastable product during the formation of aggregate II in the presence of 1.2-1.5 equiv. of AgNO 3 . Furthermore, the AFM and CD results of two samples prepared using aggregates I and III with different volume ratios were similar to those obtained upon the addition of AgNO 3 to free R -L 1 . These findings suggest that homochiral self-sorting in a mixture system occurred by the generation of aggregate II composed of the [ R -L 1 Ag] + complex via the rearrangement of both, aggregates I and III. This is a unique example of helicity- and shape-driven chiral self-sorting supramolecular polymerization induced by Ag + starting from one enantiomeric component. This research will improve understanding of homochirality in complex biological models and contribute to the development of new chiral materials and catalysts for asymmetric synthesis., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We report kinetically controlled chiral supramolecular polymerization based on ligand-metal complex with a 3 : 2 (L : Ag + ) stoichiometry accompanying a helical inversion in water. A new family of bipyridine-based ligands (d- L1 , l- L1 , d- L2 , and d- L3 ) possessing hydrazine and d- or l-alanine moieties at the alkyl chain groups has been designed and synthesized. Interestingly, upon addition of AgNO 3 (0.5-1.3 equiv.) to the d- L1 solution, it generated the aggregate I composed of the d- L1 AgNO 3 complex (d- L1  : Ag + = 1 : 1) as the kinetic product with a spherical structure. Then, aggregate I (nanoparticle) was transformed into the aggregate II (supramolecular polymer) based on the (d- L1 ) 3 Ag 2 (NO 3 ) 2 complex as the thermodynamic product with a fiber structure, which led to the helical inversion from the left-handed (M-type) to the right-handed (P-type) helicity accompanying CD amplification. In contrast, the spherical aggregate I (nanoparticle) composed of the d- L1 AgNO 3 complex with the left-handed (M-type) helicity formed in the presence of 2.0 equiv. of AgNO 3 and was not additionally changed, which indicated that it was the thermodynamic product. The chiral supramolecular polymer based on (d- L1 ) 3 Ag 2 (NO 3 ) 2 was produced via a nucleation-elongation mechanism with a cooperative pathway. In thermodynamic study, the standard Δ G ° and Δ H e values for the aggregates I and II were calculated using the van't Hoff plot. The enhanced Δ G ° value of the aggregate II compared to that of the formation of aggregate I confirms that aggregate II was thermodynamically more stable. In the kinetic study, the influence of concentration of AgNO 3 confirmed the initial formation of the aggregate I (nanoparticle), which then evolved to the aggregate II (supramolecular polymer). Thus, the concentration of the (d- L1 ) 3 Ag 2 (NO 3 ) 2 complex in the initial state plays a critical role in generating aggregate II (supramolecular polymer). In particular, NO 3 - acts as a critical linker and accelerator in the transformation from the aggregate I to the aggregate II. This is the first example of a system for a kinetically controlled chiral supramolecular polymer that is formed via multiple steps with coordination structural change., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The self-assembly of a terpyridine-based ligand in a DMSO/water solvent mixture (1 : 99 v/v) with a high content of water formed a nanofibrillar structure and showed a non-emissive process. On the other hand, the self-assembly of the terpyridine-based ligand exhibited strong emission in the presence of Zn(2+) due to the formation of coordination bonds between the terpyridine moieties and the Zn(2+) by the aggregation-induced emission effect. The morphology of this aggregate represented a spherical structure.

A tetra-imidazole-appended tetrakis(p-phenylene)ethylene 1-Cu(2+) ensemble was found to enhance fluorescence upon addition of histidine, but not with any other amino acids. The 1-Cu(2+) ensemble also selectively detected proteins containing histidine residues in a mixture of water and methanol (90 : 10, v/v%). The 1-Cu(2+) ensemble-coated thin-layered chromatography (TLC) plate could also detect histidine quantitatively. Furthermore, the fluorescence emission recovery upon addition of five concentrations of His was ~80% with good linearity.

Terpyridine-based ligands form octahedral complexes with Co(2+) at low cation concentrations to form helical assemblies which provide a supramolecular gel framework. Increasing the Co(2+) concentration above 0.6 equiv. reveals a second, co-existing square pyramidal complex derived assembly, having a distinct helicity. While this geometry dominates at 1 equiv. of Co(2+), we find this unique form of helical inversion to be fully reversible and controllable.

A tetracarboxylic acid-appended thiacalix[4]arene-based ligand with Tb(3+) formed a supramolecular gel which showed novel fluorogenic sensor capability for probing alanine and proteins containing alanine.