Ka Young Kim

Geometric Change of a Thiacalix[4]arene Supramolecular Gel with Volatile Gases and Its Chromogenic Detection for Rapid Analysis

A coordination polymer gel that is self-assembled to form a network structure between a thiacalix[4]arene derivative (L) and Co(2+) has been prepared. This gel is capable of selectively changing color in the presence of gases that yield hydrogen chloride upon hydrolysis. The UV-vis absorption spectrum of a coordination polymer gel derived from Co(NO3)2 exhibits an absorption band at 527 nm and is colored red, indicating the formation of an octahedral Co(2+) complex. Treatment with a small amount of volatile gases containing a chlorine atom (VGCl) causes a red shift of ∼150 nm, resulting in a new strong band with a maximum at 670 nm and a color change to blue. In addition, the red color of the filter paper coated with a Co(NO3)2 coordination polymer gel changed to blue upon exposure to VGCl, reflecting a change in the coordination geometry. Red and blue colors of single crystals of Co(2+) complexes were obtained from a basic solution. From X-ray crystallographic analysis, the red Co(2+) complex corresponds to an octahedral structure, while the blue Co(2+) complex reflects the presence of a tetrahedral structure. Thus, the induced color change of Co(2+) gel from red to blue upon exposure to VGCl is due to the coordination geometry. The quantitative concentration of VGCl was calculated by employing the RGB histogram available in a smartphone application.

Chiral Supramolecular Gels with Lanthanide Ions: Correlation between Luminescence and Helical Pitch

We report the correlation between the fluorescence intensity and the helical pitch of supramolecular hydrogels with Tb(III) and Eu(III) as well as their inkjet printing patterning as an application. The luminescent gels, which exhibited three different emissions of red, green, and blue, could be prepared without and with Eu(III) and Tb(III). The luminescence intensity of supramolecular gels (gel-Tb and gel-Eu) composed of Tb(III) and Eu(III) was ca. 3-fold larger than that of the sol (1+Tb(III) or 1+Eu(III)), which was attributed to large tilting angles between molecules. By AFM observations, these gels showed well-defined right-handed helical nanofibers formed by coordination bonds in which the helical pitch lengths were strongly dependent on the concentrations of lanthanide ions. In particular, the large luminescence intensity of gel-Tb exhibited a smaller helical pitch length than that of gel-1 due to relatively weak π-π stacking with large tilting angles between molecules. The luminescence intensities were enhanced linearly with increasing concentrations of lanthanide ions. This is the first example of the correlation between the helical pitch length and the luminescence intensity of supramolecular materials. The coordination bonding in supramolecular hydrogels had a strong influence on rheological properties. We also developed a water-compatible inkjet printing system to generate luminescent supramolecular gels on A4-sized paper. The images of a logo and the text were composed of three different emissions and were well-printed on A4 sized paper coated with gel-1.

Self-Assembled Tb3+ Complex Probe for Quantitative Analysis of ATP during Its Enzymatic Hydrolysis via Time-Resolved Luminescence in Vitro and in Vivo

To more accurately assess the pathways of biological systems, a probe is needed that may respond selectively to adenosine triphosphate (ATP) for both in vitro and in vivo detection modes. We have developed a luminescence probe that can provide real-time information on the extent of ATP, ADP, and AMP by virtue of the luminescence and luminescence lifetime observed from a supramolecular polymer based on a C3 symmetrical terpyridine complex with Tb3+ (S1-Tb). The probe shows remarkable selective luminescence enhancement in the presence of ATP compared to other phosphate-displaying nucleotides including adenosine diphosphate (ADP), adenosine monophosphate (AMP), guanosine triphosphate (GTP), thymidine triphosphate (TTP), H2PO4- (Pi), and pyrophosphate (PPi). In addition, the time-resolved luminescence lifetime and luminescence spectrum of S1-Tb could facilitate the quantitative measurement of the exact amount of ATP and similarly ADP and AMP within living cells. The time-resolved luminescence lifetime of S1-Tb could also be used to quantitatively monitor the amount of ATP, ADP, and AMP in vitro following the enzymatic hydrolysis of ATP. The long luminescence lifetime, which was observed into the millisecond range, makes this S1-Tb-based probe particularly attractive for monitoring biological ATP levels in vivo, because any short lifetime background fluorescence arising from the complex molecular environment may be easily eliminated.

NMR detection of chirality and enantiopurity of amines by using benzene tricarboxamide-based hydrogelators as chiral solvating agents

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.

Self-Assembled Coumarin Nanoparticle in Aqueous Solution as Selective Mitochondrial-Targeting Drug Delivery System

The development of specifically targeted nanoparticles for subcellular organelles modified with a low-molecular-weight organic compound as drug nanocarriers can bring about wide applications in cancer therapy. However, their utility has been hampered by low selectivity, poor biodistribution, and limited efficiency. Herein, we report the aggregation behavior of a triphenylphosphonium-appended coumarin probe (TPP-C) in an aqueous solution and its applications as a mitochondria-targeting probe, and drug delivery carrier, which is a rare example for a low molecular-weight organic compound. The TPP-C formed homogeneous nanoparticles with small diameters in water as well as in mixtures of organic solvents and water. In pure water, the homogeneous nanoparticles induced J-aggregation, whereas in mixed solvents, the homogeneous nanoparticles induced H-aggregation. The luminescence intensities of nanoparticles originated from the aggregation-induced emission (AIE) effect in pure water and also in mixtures of organic solvents and water. These findings indicate that the AIE effect of TPP-C was dependent on the solvent. More interestingly, the TPP-C nanoparticles selectively accumulated in mitochondria. The TPP-C nanoparticles alone exhibited noncytotoxicity toward cancer cells. However, with the encapsulation of the anticancer drug doxorubicin (DOX) into the TPP-C nanoparticles, the DOX was efficiently delivered to the mitochondria. These results indicated that the proposed system demonstrates promise as a platform for future clinical medication, particularly for specific suborganelle-targeted drug delivery systems for cancer therapy.

Erratum to: Mitochondria-targeting self-assembled nanoparticles derived from triphenylphosphonium-conjugated cyanostilbene enable site-specific imaging and anticancer drug delivery

One of the correspondence authors, Jeehyeon Bae, in the original version of this article was unfortunately not marked on page 1082 and the first page of the ESM.Instead ofKa Young Kim1,§, Hanyong Jin2,§, Jaehyeon Park1, Sung Ho Jung1, Ji Ha Lee1, Hyesong Park1, Sung Kuk Kim1, Jeehyeon Bae2, and Jong Hwa Jung1 (✉)It should beKa Young Kim1,§, Hanyong Jin2,§, Jaehyeon Park1, Sung Ho Jung1, Ji Ha Lee1, Hyesong Park1, Sung Kuk Kim1, Jeehyeon Bae2 (✉), and Jong Hwa Jung1 (✉)One of the correspondence authors, Jeehyeon Bae, and his email address in the original version of this article were unfortunately not written on page 1082 and the first page of the ESM.Instead ofAddress correspondence to jonghwa@gnu.ac.krIt should beAddress correspondence to Jong Hwa Jung, jonghwa@gnu.ac.kr; Jeehyeon Bae, jeehyeon@cau.ac.kr

Correction: A crown-ether-based moldable supramolecular gel with unusual mechanical properties and controllable electrical conductivity prepared by cation-mediated cross-linking

Typical supramolecular gels do not exhibit electrical conductivity because of the wide band gaps present in the low-conjugation gelator molecules and the long distances between them, which arise because of the large amount of solvent within gel networks. Consequently, the practical applications of supramolecular gels are largely limited. Herein, a strategy for significantly enhancing the mechanical, electrical, and vibrational isolation properties of supramolecular gels derived from low-molecular-weight building blocks, which involves the incorporation of Cs+ ions, is described. High-elasticity supramolecular gels produced from the hydrazone reaction between calix[4]arene- and 18-crown-6-ether-based building blocks are mechanically strong and can be molded into free-standing objects. By controlling the concentration of Cs+ in the supramolecular gels, their mechanical and electrical properties can be tuned. The supramolecular gels exhibit 34-fold and 62-fold enhanced storage and loss moduli, respectively, upon addition of Cs+ ions. Furthermore, the electrical conductivities of the supramolecular gels proportionally increase with the amount of Cs+ ions in the gel network. These dramatic enhancements are due to the sandwich complex formation between the 18-crown-6 moieties and Cs+ ions. Also, the supramolecular gels reveal effective vibration-isolation abilities. It is believed that this strategy presents new possibilities for developing soft materials with unique functions.

Helicity Control of Triphenylamine-Based Supramolecular Polymers: Correlation between Solvent Properties and Helicity in Supramolecular Gels

We describe the role of amide groups formed by achiral and chiral moieties to study supramolecular helicity at the molecular level and the correlation between helicity and solvent properties at the supramolecular level. Using circular dichroism (CD) spectroscopy, we observed the CD spectra of supramolecular gel 1, which comprised a triphenylamine (TPA) core, terpyridine, and alanine moieties, formed in various solvents. The strong positive CD signals of supramolecular gel 1 formed in organic solvents, such as chloroform, tetrahydrofuran (THF), and dichloromethane, which have low polarity and a low acceptor number, were observed at 350 nm, indicating right-handed helicity. In contrast, the negative CD signals of supramolecular gel 1 formed in mixed DMSO/water (5:1 v/v), methanol, ethanol, and n-propanol were obtained at 350 nm, indicating left-handed helicity. These findings suggest that the helicity of supramolecular gel 1 was strongly influenced by the solvent properties. Indeed, atomic force spectroscopy images showed the right- and left-handed helicity of supramolecular gel 1 formed in various organic solvents, which was pure helicity.

Peculiar Triarylamine-Based Co-assembled Supramolecular Polymers That Exhibit Two Transition Temperatures in the Formation of a Coiled Helical Bundle

This paper describes the peculiar co-assembly supramolecular polymerization behavior of triphenylamine trisamide derivatives with d-alanine (T-ala) or glycine (T-gly) moieties. Concentration and temperature-dependent circular dichroism (CD) spectroscopy revealed that the heating curves of co-assemblies obtained at various molar ratios of T-ala to T-gly exhibited two distinct transition temperatures. The first transition was due to the transformation from coiled helical bundles to single helical fibers without handedness. The second was due to a change from typical elongation to nucleation. These phenomena were confirmed by solvent-dependent decoiling of coiled helical structures and concentration-dependent morphological analysis. The two transitioning temperatures were dependent on the concentration of T-ala in the co-assemblies, suggesting that T-ala concentration plays an important role in the formation of coiled helical bundles. Our study demonstrated the first observation of two distinct transition temperatures in supramolecular polymers.