Chirality-sensing supramolecular systems

Mechanistic Interplay between Light Switching and Guest Binding in Photochromic [Pd2Dithienylethene4] Coordination Cages

Photochromic [Pd₂L₄] coordination cages based on dithienylethene (DTE) ligands L allow triggering guest uptake and release by irradiation with light of different wavelengths. The process involves four consecutive electrocyclic reactions to convert all chromophores between their open and closed photoisomeric forms. So far, guest affinity of the fully switched species was elucidated, but mechanistic details concerning the intermediate steps remained elusive. Now, a new member of the DTE cage family allows unprecedented insight into the interplay between photoisomerization steps and guest location inside/outside the cavity. Therefore, the intrinsic chirality of the DTE backbones was used as reporter for monitoring the fate of a chiral guest. In its "open" photoisomeric form ( o-L, [Pd₂( o-L)₄] = o-C), the C₂-symmetric DTE chromophore quickly converts between energetically degenerate P and M helical conformations. After binding homochiral 1 R-( -) or 1 S-( +) camphor sulfonate ( R-CSA or S-CSA), guest-to-host chirality transfer was observed via a circular dichroism (CD) signal for the cage-centered absorption. Irradiating the R/S-CSA@ o-C host-guest complexes at 313 nm produced configurationally stable "closed" photoisomers, thus locking the induced chirality with an enantiomeric excess close to 25%. This value (corresponding to chiral induction for one out of four ligands), together with DOSY NMR, ion mobility mass spectrometry, and X-ray structure results, shows that closure of the first photoswitch is sufficient to expel the guest from the cavity.

Optical lateral forces and torques induced by chiral surface-plasmon-polaritons and their potential applications in recognition and separation of chiral enantiomers

Surface plasmon polaritons carry an intrinsic transverse spin angular momentum which is locked to their propagation direction due to the quantum spin Hall effect of light. We study the chirality-sorting lateral optical forces arising from this phenomenon in a Kretschmann configuration. We show that the characteristics of surface plasmon polaritons are affected by small changes of the environment's chirality. This property can be utilized to detect the medium's chirality in the macro-world. Furthermore, we explain how the the lateral forces and optical torques interact with the chirality of nano-particles located or adsorbed in the vicinity of the surface in the micro-world. Finally, we demonstrate that introducing one handedness of chirality to the dielectric medium in the Kretschmann configuration will benefit the discrimination of chiral enantiomers compared with the nonchiral case. Our work presents physical insights into chirality-selective lateral forces using surface plasmon polaritons and provides a new approach to discriminating and separating chiral enantiomers in the chemical and pharmaceutical industries.

Kinetic and spectroscopic studies on the chiral self-aggregation of amphiphilic zinc and copper (l)-prolinate-tetraarylporphyrin derivatives in different aqueous media

The chiral self-aggregation of (l)-proline porphyrin derivatives depends on both the nature of the media and the coordinated metal ion.

Room-temperature phosphorescent γ-cyclodextrin-cucurbit[6]uril-cowheeled [4]rotaxanes for specific sensing of tryptophan

The room temperature phosphorescence of iodine-substituted-γ-CD-CB[6]-cowheeled[4] rotaxanes was quenched specifically by tryptophan among plasma amino acids.

A simple and visual approach for enantioselective recognition through supramolecular gels with specific selectivity

(S)/(R)1 enantioselectively self-assemble to form a gel or solution with one enantiomer of (S)/(R)BINAM with specific selectivity.

Recent developments in the construction of metallacycle/metallacage-cored supramolecular polymers via hierarchical self-assembly

Supramolecular polymers have received considerable attention during the last few decades due to their scientific value in polymer chemistry and profound implications for future developments of advanced materials. Discrete supramolecular coordination complexes (SCCs) with well-defined size, shape, and geometry have been widely employed to construct hierarchical systems by coordination-driven self-assembly with the spontaneous formation of metal-ligand bonds, which results in the formation of well-defined two-dimensional (2D) metallacycles or three-dimensional (3D) metallacages with high functionalities. The incorporation of discrete SCCs into supramolecular polymers by the orthogonal combination of metal-ligand coordination and other noncovalent interactions or covalent bonding could further facilitate the construction of novel supramolecular polymers with hierarchical architectures and multiple functions including controllable uptake and release of guest molecules, providing a flexible platform for the development of smart materials. In this review, the recent progress in metallacycle/metallacage-cored supramolecular polymers that were constructed by the combination of metal-ligand interactions and other orthogonal interactions (including hydrophobic or hydrophilic interactions, hydrogen bonding, van der Waals forces, π-π stacking, electrostatic interactions, host-guest interactions and covalent bonding) has been discussed. In addition, the potential applications of metallacycle/metallacage-cored supramolecular polymers in the areas of light emitting, sensing, bio-imaging, delivery and release, etc., are also presented.

Reaction-based chiroptical sensing of ClO− using circularly polarized luminescence via self-assembly organogel

A chiral amino acid functionalized probe, PTZ-D, could self-assemble into a chiral organogel displaying unprecedented chiroptical monitoring of ClO⁻ with switchable CPL signals.

A novel multifunction photochromic metal–organic framework for rapid ultraviolet light detection, amine-selective sensing and inkless and erasable prints

The system shows efficient and fast low intensity ultraviolet light detection, amine-selective sensing and also be used as inkless and erasable print.

Fluorescent molecular spring that visualizes the extension and contraction motions of a double-stranded helicate bearing terminal pyrene units triggered by release and binding of alkali metal ions

A unique springlike motion of a fluorescent pyrene-terminated double-stranded helicate is visualized by the catch and release of alkali metal ions.

Photocontrolled morphological conversion and chiral transfer of a snowflake-like supramolecular assembly based on azobenzene-bridged bis(dibenzo-24-crown-8) and a cholesterol derivative

A snowflake-like supramolecular clockwise-helical assembly was fabricated via the host–guest interaction, while a snowflake-like supramolecular non-helical assembly can be obtained upon UV-irradiation.

Spiro[pyrrol-benzopyran]-based probe with high asymmetry for chiroptical sensing via circular dichroism

We proposed an efficient approach to construct a novel spiro[pyrrol-benzopyran] scaffold with high asymmetry for reaction-based chiroptical sensing via circular dichroism.

A dual chromophore sensor for the detection of amines, diols, hydroxy acids, and amino alcohols

The determination of enantiomeric excess (ee) in various groups of chiral compounds, namely amines, amino alcohols, diols, and hydroxy acids is performed using a dual chromophore FRET/PET based sensor ensemble. The sensing ensemble utilizes fluorescence changes from two chromophores (indicators) to classify 13 pairs of enantiomers as well as allows for the qualitative and quantitative determination of ee of various classes of chiral compounds with high accuracy (<2% error).

Smart, chiral, and nonconjugated cyclohexane-based bis-salicylaldehyde hydrazides: multi-stimuli-responsive, turn-on, ratiometric, and thermochromic fluorescence, single-crystal structures via DFT calculations

Multidentate and environmentally sensitive dyes show turn-on, ratiometric, and thermochromic fluorescence.

Electronic chirality inversion of lanthanide complex induced by achiral molecules

A novel mechanism for chiroptical activity inversion based on the electronic structure of metal complexes without Λ- or Δ-type structure change was demonstrated spectroscopically and theoretically. To demonstrate the mechanism, a europium (Eu(III)) complex with chiral (+)-3-(trifluoroacetyl)camphor (+tfc) and achiral triphenylphosphine oxide (tppo) was prepared. The steric and electronic structures of the Eu(III) complex were adjusted by additional achiral tppo and coordinating acetone molecules, and were characterised by 1H NMR, photoluminescence, and emission lifetime measurements. The optical activity of the Eu(III) complex in solution was evaluated by circularly polarized luminescence (CPL) measurements. CPL sign inversion, which was independent of Λ- or Δ-type structure changes from the spectroscopic viewpoint, and a drastic CPL intensity enhancement were observed depending on the external achiral molecules around Eu(III) ion. These phenomena provide the first clarification of optical activity change associated with electronic structure rather than chiral coordination structure-type (Λ or Δ) under external environments.

Synthesis of a Helical Analogue of Kekulene: A Flexible π-Expanded Helicene with Large Helical Diameter Acting as a Soft Molecular Spring

A π-expanded helicene that is the helically twisted analogue of kekulene was synthesized using a 6-fold ring-closing olefin metathesis (RCM) reaction as a key step. The π-expanded geometry with large helical diameter ( d_h = 10.2 Å), consisting only of carbon and hydrogen atoms (C₅₄H₃₀), was unambiguously determined by single-crystal X-ray analysis. We found that the π-expanded helicene with large helical diameter will act as a soft molecular spring with a small spring constant. Interestingly, the mechanical properties of the molecular springs roughly satisfied a physical formula for macroscopic spring materials; i.e., the force constant of the elongation of a molecular spring ( k) is inversely proportional to the third power of the helical diameter ( k ∝ d_h^-3).

Asymmetric vinylogous aldol addition of alkylidene oxindoles on trifluoromethyl-α,β-unsaturated ketones

A novel vinylogous aldol addition of alkylidene oxindole with 1-trifluoromethyl-3-alkylidene-propan-2-ones is presented. The reaction, catalyzed by a bifunctional tertiary amine, provides an efficient application of the vinylogous reactivity of oxindoles for the preparation of enantioenriched trifluoromethylated allylic alcohols.

The effect of the linker size in C2-symmetrical chiral ligands on the self-assembly formation of luminescent triple-stranded di-metallic Eu(iii) helicates in solution

Chiral lanthanide-based supramolecular structures have gained significant importance in view of their application in imaging, sensing and other functional purposes. We have designed chiral C2-symmetrical ligands (L) based on the use of two 2,6-pyridine-dicarboxylic-amide moieties (pda), that differ from one another by the nature of the diamine spacer groups (from 1,3-phenylenedimethanamine (1(S,S), 2(R,R)) and benzene-1,3-diamine (3(S,S), 4(R,R)) to much bulkier 4,4'-(cyclohexane-1,1-diyl)bis(2,6-dimethylaniline) (5(S,S), 6(R,R))) between these two pda units. The self-assembly between L and Eu(iii) ions were investigated in CH3CN solution at low concentration whereby the changes in the absorbance, fluorescence and Eu(iii)-centred emission spectra allowed us to model the binding equilibria occurring in the solution to the presence of [Eu:L2], [Eu2:L2], [Eu2:L3] assemblies and reveal their high binding constant values. The self-assembly in solution were also studied at higher concentration by following the changes in the 1H NMR spectra of the ligands upon Eu(iii) addition, as well as by using MALDI-MS of the isolated solid state complexes. The chiroptical properties of the ligands were used in order to study the structural changes upon self-assembly between the ligands and Eu(iii) ions using circular dichroism (CD) and circularly polarised luminescence (CPL) spectroscopies. The photophysical properties of [Eu2:L3] complexes were evaluated in solution and showed a decrease of luminescence quantum yield when going from the ligand with smaller (1(S,S)) to bulkier (5(S,S)) linker from ∼5.8% to ∼2.6%. While mass-spectrometry revealed the possible formation of trinucler assemblies such as [Eu3:L3] and [Eu3:L2].

Macroscopic helical chirality and self-motion of hierarchical self-assemblies induced by enantiomeric small molecules

Transfer of molecular chirality to supramolecular chirality at nanoscale and microscale by chemical self-assembly has been studied intensively for years. However, how such molecular chirality further transfers to the macroscale along the same path remains elusive. Here we reveal how the chirality from molecular level transfers to macroscopic level via self-assembly. We assemble a macrostripe using enantiomeric camphorsulfonic acid (CSA)-doped polyaniline with hierarchical order. The stripe can twist into a single-handed helical ribbon via helical self-motion. A multi-scale chemo-mechanical model is used to elucidate the mechanism underlying its chirality transfer and induction. The molecular origin of this macroscopic helical chirality is verified. Results provide a comprehensive understanding of hierarchical chirality transfer and helical motion in self-assembled materials and even their natural analogues. The stripe exhibits disparate actuation behaviour under stimuli of enantiomeric amines and integrating such chiral perception with helical self-motion may motivate chiral biomimetic studies of smart materials.

Chirality transfer by chemical self-assembly has been studied intensively for years but chirality transfers along the same path remains elusive. Here the authors use a multiscale chemo-mechanical model to elucidate the mechanism underlying the chirality transfer via self-assembly in hierarchical camphorsulfonic acid doped polyaniline.

Combined Experimental and Theoretical Study on Circular Dichroism and Circularly Polarized Luminescence of Configurationally Robust D3-Symmetric Triple Pentahelicene

Pentahelicene (PH) exhibits the largest absorption ( g_abs) and luminescence ( g_lum) dissymmetry factors among the helicene family but is configurationally and (photo)chemically labile, encumbering its application to chiroptical materials. To bypass the pitfalls, three PH units are merged in a single molecule to build D₃-symmetric triple pentahelicene, hexabenzotriphenylene (HBT), which attains indeed the configurational and (photo)chemical robustness through equilibrium with a C₂-symmetric conformer that interrupts the racemization and photocyclization. UV-vis, circular dichroism (CD), and circularly polarized luminescence (CPL) spectral examinations reveal the significantly larger g_abs and g_lum values for HBT than for any of configurationally robust single [ n]helicene ( n ≥ 6) and C₂-symmetric triple pentahelicene, trinaphthotriphenylene (TNT). Theoretical calculations precisely reproduce the main features of the experimental CD and CPL spectra of PH, HBT, and TNT, and the relevant electric and magnetic transition moments and their mutual angles well rationalize the relative CD and CPL intensities of all the single and triple pentahelicenes.

Induced chirality sensing through formation and aggregation of the chiral imines double winged with pyrenes or perylenes

Reaction of chiral amines with benzaldehydes 3,5-disubstituted by two pyrenes or perylenes afforded corresponding double winged chiral imines, which aggregated to show significantly enhanced circular dichroism spectra at the transition bands of the chromophores in the mixture solutions of DMF and H2O.

Self-Assembly of Amphiphilic Dipeptide with Homo- and Heterochiral Centers and Their Application in Asymmetric Aldol Reaction

Chiral self-assembly has drawn increasing interest in supramolecular chemistry. Here, we have designed amphiphilic l-Pro-l-Glu and l-Pro-d-Glu dipeptides and investigated their chiral self-assembly as well as asymmetric catalytic performance to disclose the synergistic effect of two stereogenic centers in the self-assembly and catalysis. It was found that both of the diastereomeric dipeptides can easily self-assemble into organogels with nanofibers. When these nanofibers were used as a catalyst for the asymmetric aldol reactions, enhanced enantioselectivity was obtained compared with their molecular state. Moreover, the L-L isomer assemblies showed higher enantioselectivity than the L-D isomer. It was revealed that both the supramolecular chirality of the nanofiber and the chiral catalytic site of l-proline played important roles in the asymmetric catalysis. In addition, the synergistic effect of two homochiral centers led to more efficient supramolecular catalysis that the L-L assemblies showed high yields (up to 97%), anti-diastereoselectivity (up to 99%), and excellent enantioselectivity (up to >99%).

Boosting Self-Assembly Diversity in the Solid-State by Chiral/Non-Chiral ZnII -Porphyrin Crystallization

A chiral Zn^II porphyrin derivative 1 and its achiral analogue 2 were studied in the solid state. Considering the rich molecular recognition of designed metalloporphyrins 1 and 2 and their tendency to crystallize, they were recrystallized from two solvent mixtures (CH₂ Cl₂ /CH₃ OH and CH₂ Cl₂ /hexane). As a result, four different crystalline arrangements (1 a,b and 2 a,b, from 0D to 2D) were obtained. Solid-state studies were performed on all the species to analyze the role played by chirality, solvent mixtures, and surfaces (mica and HOPG) in the supramolecular arrangements. By means of combinations of solvents and substrates a variety of microsized species was obtained, from vesicles to flower-shaped arrays, including geometrical microcrystals. Overall, the results emphasize the environmental susceptibility of metalloporphyrins and how this feature must be taken into account in their design.

Supramolecularly directed rotary motion in a photoresponsive receptor

Stimuli-controlled motion at the molecular level has fascinated chemists already for several decades. Taking inspiration from the myriad of dynamic and machine-like functions in nature, a number of strategies have been developed to control motion in purely synthetic systems. Unidirectional rotary motion, such as is observed in ATP synthase and other motor proteins, remains highly challenging to achieve. Current artificial molecular motor systems rely on intrinsic asymmetry or a specific sequence of chemical transformations. Here, we present an alternative design in which the rotation is directed by a chiral guest molecule, which is able to bind non-covalently to a light-responsive receptor. It is demonstrated that the rotary direction is governed by the guest chirality and hence, can be selected and changed at will. This feature offers unique control of directional rotation and will prove highly important in the further development of molecular machinery.

Unidirectional rotation in a synthetic molecular motor is typically driven by intrinsic asymmetry or sequences of chemical transformations. Here, the authors control the direction of a molecule’s rotation through supramolecular binding of a chiral guest and subsequent transfer of its chiral information.

1,1'-Binaphthyl-substituted diphosphene: synthesis, structures, and chiral optical properties

1,1'-Binaphthyl-substituted diphosphene 1 possessing a P[double bond, length as m-dash]P double bond and an axially chiral 1,1'-binaphthyl group was synthesized and fully characterized. Diphosphene 1 was prepared as an optically active form and thus is the first example of a chiral diphosphene. The CD spectra of 1 showed apparent circular dichroism in the longer wavelength region, caused by the P[double bond, length as m-dash]P moiety.

Enhanced chiral recognition by γ-cyclodextrin-cucurbit[6]uril-cowheeled [4]pseudorotaxanes

Mixing γ-cyclodextrin (γ-CD), cucurbit[6]uril (CB[6]) and tetraammonium-bearing axles together led to a spontaneous formation of γ-CD-CB[6]-cowheeled [4]pseudorotaxanes. The well-defined unsymmetrical cavities thus formed enhance the binding affinity towards chiral amines by factors of several hundreds and show remarkably improved chiral discrimination.

Alanine-Based Chiral Metallogels via Supramolecular Coordination Complex Platforms: Metallogelation Induced Chirality Transfer

Chiral self-assemblies constantly attract great interest because of their potential to provide insight into biological systems and materials science. Herein we report on the efficient preparation of alanine-based chiral metallacycles, rhomboids 1D and 1L and hexagons 2D and 2L using a Pt(II) ← pyridyl directional bonding approach. The metallacycles are subsequently assembled into nanospheres at low concentration, that generate chiral metallogels at high concentration driven by hydrogen bonding, hydrophobic and π-π interactions. The gels consist of microscopic chiral nanofibers with well-defined helicity, as confirmed by circular dichroism (CD) and scanning (SEM) and transmission electron (TEM) microscopies. Given these results, we expect this technique will not only unlock interesting new approaches to understand homochirality in nature but also allow the design of versatile soft materials containing chiral supramolecular cores.

Chiral metallosupramolecular architectures

Over the past few decades, supramolecular chirality in discrete metallosupramolecular architectures has received considerable attention. In this review, a comprehensive summary of discrete, chiral coordination-driven structures, including helices, metallacycles, metallocages, etc., is presented. Although chirality can be introduced prior to, during or even after the coordination self-assembly process, this review puts major emphasis on the more recent development of metallosupramolecular architectures from chiral components, where chirality arises from the enantiopure or racemic scaffolds (bridging or auxiliary ligand). Special attention will be paid to homochiral metallo-assemblies using achiral components where chirality is obtained as a consequence of the twisting of the ligands. Additionally, the potential applications of homochiral metallosupramolecular architectures are also discussed. We hope that this review will be of interest to researchers attempting to design new elaborate homochiral metallosupramolecular architectures with even greater complexity and potential for functions such as chiral recognition, enantiomer separation, asymmetric catalysis, nonlinear sensors, and devices.

A Chiral Sensor Array for Peptidoglycan Biosynthesis Monitoring Based on MoS2 Nanosheet-Supported Host-Guest Recognitions

Monitoring the dynamic change with respect to chirality and species of amino acids in bacterial peptidoglycan (PG) during cell wall biosynthesis is correlated with bacterial taxonomy, physiology, micropathology, and antibacterial mechanisms. However, this is challenging because reported methods usually lack the ability of chiral analysis with the coexistence of d- and l-amino acids in PG. Here we report a chiral sensor array for PG biosynthesis monitoring through chiral amino acid recognition. Multitypes of host molecule modified MoS₂ nanosheets (MNSs) were used as receptor units to achieve more accurate and specific sensing. By applying indicator displacement strategy, the distinct and reproducible fluorescence-response patterns were obtained for linear discriminant analysis (LDA) to accurately discriminate achiral Gly, 19 l-amino acids and the corresponding 19 d-enantiomers simultaneously. The sensor array has also been used for identifying bacterial species and tracking the subtle change of amino acid composition of PG including chirality and species during biosynthesis in different growth status and exogenous d-amino acid stimulation.

Supramolecular Photochirogenesis Driven by Higher-Order Complexation: Enantiodifferentiating Photocyclodimerization of 2-Anthracenecarboxylate to Slipped Cyclodimers via a 2:2 Complex with β-Cyclodextrin

Chiral slipped 5,8:9',10'-cyclodimers were preferentially produced over classical 9,10:9',10'-cyclodimers upon supramolecular photocyclodimerization of 2-anthracenecarboxylate (AC) mediated by β-cyclodextrin (β-CD). This photochirogenic route to the slipped cyclodimers, exclusively head-to-tail (HT) and highly enantioselective, has long been overlooked in foregoing studies but is dominant in reality and is absolutely supramolecularly activated by 2:2 complexation of AC with β-CD. The intricate structural and photophysical aspects of this higher-order complexation-triggered process have been comprehensively elucidated, while the absolute configurations of the slipped cyclodimers have been unambiguously assigned by comparing the experimental and theoretical circular dichroism spectra. In the 2:2 complex, two ACs packed in a dual β-CD capsule are not fully overlapped with each other but are only partially stacked in a slipped anti- or syn-HT manner. Hence, they do not spontaneously cyclodimerize upon photoexcitation but instead emit long-lived excimer fluorescence at wavelengths slightly longer than the monomer fluorescence, indicating that the slipped excimer is neither extremely reactive nor completely relaxed in conformation and energy. Because of the slipped conformation of the AC pair in the soft capsule, the subsequent photocyclodimerization becomes manipulable by various internal or external factors, such as temperature, pressure, added salt, and host modification, enabling us to exclusively obtain the slipped cyclodimers with high regio- and enantioselectivities. In this supramolecularly driven photochirogenesis, the dual β-CD capsule functions as a chiral organophotocatalyst to trigger and accelerate the nonclassical photochirogenic route to slipped cyclodimers by preorganizing the conformation of the encapsulated AC pair, formally mimicking a catalytic antibody.

Elucidation of the origin of chiral amplification in discrete molecular polyhedra

Chiral amplification in molecular self-assembly has profound impact on the recognition and separation of chiroptical materials, biomolecules, and pharmaceuticals. An understanding of how to control this phenomenon is nonetheless restricted by the structural complexity in multicomponent self-assembling systems. Here, we create chiral octahedra incorporating a combination of chiral and achiral vertices and show that their discrete nature makes these octahedra an ideal platform for in-depth investigation of chiral transfer. Through the construction of dynamic combinatorial libraries, the unique possibility to separate and characterise each individual assembly type, density functional theory calculations, and a theoretical equilibrium model, we elucidate that a single chiral unit suffices to control all other units in an octahedron and how this local amplification combined with the distribution of distinct assembly types culminates in the observed overall chiral amplification in the system. Our combined experimental and theoretical strategy can be applied generally to quantify discrete multi-component self-assembling systems.

Recognition of chiral zwitterionic interactions at nanoscale interfaces by chiroplasmonic nanosensors

The ability to detect chiral molecules renders plasmonic nanosensors as promising tools for the study of chirality phenomena in living systems. Using gold nanorod based plasmonic nanosensors, we investigated here typically chiral zwitterionic electrostatic (Zw-Es) and hydrogen-bonding (Hb) interactions occurring via amine and carboxylic groups at nanoscale interfaces in aqueous solutions. Our results reveal that the plasmonic circular dichroism responses of the nanosensors can have both conformational sensitivity and chiral selectivity to the interfacial molecular interactions. Such a dual function of the plasmonic nanosensors enables a new chiroptical way to differentiate between chiral Zw-Es and Hb interactions, to monitor the transformation between these two interaction forces, and particularly to recognize homochiral Zw-Es interactions in solution. Together with the surface enhanced Raman scattering (SERS) technique, this plasmonic CD based biosensing could have important values for the insightful understanding of chirality-dependent molecular recognition in biological and pharmaceutical systems.

Direct Detection of Hardly Detectable Hidden Chirality of Hydrocarbons and Deuterated Isotopomers by a Helical Polyacetylene through Chiral Amplification and Memory

We report the first direct chirality sensing of a series of chiral hydrocarbons and isotopically chiral compounds (deuterated isotopomers), which are almost impossible to detect by conventional optical spectroscopic methods, by a stereoregular polyacetylene bearing 2,2'-biphenol-derived pendants. The polyacetylene showed a circular dichroism due to a preferred-handed helix formation in response to the hardly detectable hidden chirality of saturated tertiary or chiroptical quaternary hydrocarbons, and deuterated isotopomers. In sharp contrast to the previously reported sensory systems, the chirality detection by the polyacetylene relies on an excess one-handed helix formation induced by the chiral hydrocarbons and deuterated isotopomers via significant amplification of the chirality followed by its static memory, through which chiral information on the minute and hidden chirality can be stored as an excess of a single-handed helix memory for a long time.

Synthesis of Amino Acid-Derived 1,2,3-Triazoles: Development of a Nontrivial Fluorescent Sensor in Solution for the Enantioselective Sensing of a Carbohydrate and Bovine Serum Albumin Interaction

A series of amino acid-derived 1,2,3-triazoles presenting the amino acid and the aromatic moieties connected by a triazole-4-carboxylate spacer is discussed in this work. These compounds were achieved in good yields by organocatalytic enamine-azide [3 + 2] cycloadditions. One of the molecules obtained, bearing a 7-chloroquinoline moiety, was photoactive in the UV-violet region and was successfully employed as a probe for substrate-specific enantiomeric sensing using d-(-)-arabinose and l-(+)-arabinose. The potential application as a fluorescent probe to detect protein in phosphate buffer solution was also explored using as model bovine serum albumin (BSA). The studied compounds presented both suppression and association behavior in the presence of BSA. In addition, theoretical calculations were performed at levels ωB97XD/cc-pVDZ and PBE1PBE/6-311+G(d,p) together with the polarizable continuum model to understand the interaction of the molecules with the enantiomers.