K_2CO_3 catalyzed solvent-free synthesis of molecular tweezers containing chiral unsymmetrical urea unit under microwave irradiation

A facile,rapid and efficient method for the synthesis of molecular tweezers containing chiral unsymmetrical urea unit in solvent- free conditions using microwave was reported.

Design and synthesis of chiral single-armed molecular tweezers derived fromα-hyodeoxycholic acid

A novel type of molecular tweezers with different chiral center and cleft has been designed and prepared by using α- hyodeoxycholic acid as spacer and D/L-amino acid methyl ester as chiral arm attached at 3-position. Their structures were elucidated by ^1H NMR, FTIR and elemental analysis. Their recognition properties for various D/L-amino acid methyl esters were also investigated. The preliminary results indicated that these chiral single-armed molecular tweezers exhibited good recognition ability for D/L-amino acid methyl esters with high association constant （up to 5.24 × 10^3 L mol^-1）.

Design and Synthesis of Chiral Molecular Tweezers Based on Deoxycholic Acid

A series of new chiral molecular tweezers have been designed and synthesized by using deoxycholic acid as spacer and aromatic amines as arms. Instead of using toxic phosgene, the triphosgene was employed in synthesis of the molecular tweezers receptors. These chiral molecular tweezers showed good enantioselectivity for D-amino acid methyl esters.

Design and Synthesis of Novel Molecular Tweezers Derived from Chenodeoxycholic Acid

A novel type of chiral molecular tweezers has been designed and synthesized by using chenodeoxy cholic acid as spacer and the aromatic compounds as arm. Their structures were characterized by 1HNMR, IR, MS spectra and elemental analysis. These chiral molecular tweezers showed good enantioselectivity for D-amino acid methyl esters.

Rapid and efficient synthesis of new chiral aromatic amide molecular tweezers under solvent-free conditions using microwave

An efficient and simple method for the synthesis of new chiral aromatic amide molecular tweezers by irradiation with microwave under solvent-free conditions has been developed. Its main advantages are short reaction times, good conversions and the environmentally friendly nature of the process.

Design and synthesis of novel chiral molecular tweezers based on deoxycholic acid

A novel type of chiral molecular tweezers has been designed and synthesized by using deoxycholic acid as backbone and ethanoyl and the chiral unsymmetrical urea unit as arms. Their structures were characterized by 1H NMR, IR, MS spectra and elemental analysis. These molecular tweezers showed good binding ability for neutral molecules and chiral molecules.

π-Fused Diazocines with Controllable Photoswitching Properties as Molecular Tweezers

Diazocines,a type of photoswitch molecules,are distinguished by their unique conformation and photochromic properties.Molecular engineering of diazocines,especially theπ-extended ones,remains challenging due to limited synthetic methods.Here,we developed threeπ-fused diazocines(BAZO-1,BAZO-2,and BAZO-3)via Bischler–Napieralski cyclization.Their isomerizations(Z⇆E)were switchable under visible light sources(427 and 630 nm).The size of theirπ-extension exerted a significant influence on the isomerization process,whereby the biggest fourfold ring-closure diazocine(BAZO-3)showed the fastest conversion rate(Z→E).Notably,the half-life(t1/2)of the E isomer of BAZO-3 was 14.6 times higher than that of the twofold ring-closure BAZO-1.Thus,BAZO-3 acted as a molecular tweezer based on double N-embedded pyrene units,allowing it to bind to pyrene through supramolecular interactions.This work may pave the way for designing novel photoswitches with long half-lives and lightcontrolled properties.

Simultaneous enhancement of phosphorescence and chirality by host–guest recognition of molecular tweezers

A novel type of host-guest recognition systems have been developed on the basis of a Au(Ⅲ) molecular tweezer receptor and chiral Pt(Ⅱ) guests. The complementary host-guest motifs display high non-covalent binding affinity (Ka: ∼10^(4) L/mol) due to the participation of two-fold intermolecular π-π stacking interactions. Both phosphorescence and chirality signals of the Pt(Ⅱ) guests strengthen in the resulting host-guest complexes, because of the cooperative rigidifying and shielding effects rendered by the tweezer receptor. Their intensities can be reversibly switched toward pH changes, by taking advantage of the electronic repulsion effect between the protonated form of tweezer receptor and the positive-charged guests in acidic environments. Overall, the current study demonstrates the feasibility to enhance and modulate phosphorescence and chirality signals simultaneously via molecular tweezer-based host-guest recognition.

Dynamically switchable porphyrin-based molecular tweezer for on-off fullerene recognition

Herein,a novel molecular tweezer based on 2,2'-bipyridine-bridged porphyrin subunits was constructed for efficient fullerenes recognition.The syn conformation of the molecule,which was obtained by Zn(Ⅱ)coordination,gives rise to a proper cavity to interact with fullerene guests to form a stable 1:1 complex in toluene solution.It exhibits distinct binding selectivity towards C_(60)over C_(70).Moreover,the fullerene recognition capacity can be adequately suppressed by importing H_(2)PO_(4)^(-)to competitively capture Zn(Ⅱ)along with syn-anti conformational conversion.Subsequently,the molecular tweezer regenerated to bind the fullerene by introducing the Ca^(2+)into the system.Significantly,the association-disassociation process can be switched reversibly and repeatedly.

Design and synthesis of novel tweezer anion receptors based on deoxycholic acid

A novel type of molecular tweezer receptors based on deoxycholic acid has been designed and synthesized and their binding properties were examined by UV-vis spectral titration. These molecular tweezers showed a high selectivity toward F^- over Cl^-, Br^-, I^-, AcO^-, H2PO4^-.

Near-Infrared-Emissive Self-assembled Polymers via the Implementation of Molecular Tweezer/Guest Complexation on a Supramolecular Coordination Complex Platform

Coordination-driven self-assembly strategy has demonstrated the efficiency and versatility to construct well-ordered supramolecular coordination complexes （SCCs） such as discrete metallacycles and metallacages. In recent years, it has aroused tremendous interest to build more complexed self-assembled structures via the implementation of additional non-covalent recognition motifs on the SCCs platform. In this work, we have successfully attained this objective, with the elaborate manipulation of non-interfering pyridine-Pt2＋ and molecular tweezer/guest complexation in a hierarchical self-assembly manner. The resulting SCCs-based linear supramolecular polymers exhibit intriguing NIR-emissive behaviors, primarily attributed to the presence of intermolecular Pt（II）-Pt（II） metal-metal interactions in the non-covalent tweezering structure. Hence, supramolecular engineering of multiple non-covalent interactions offers a feasible avenue toward functional materials with tailored properties.

Mechanochromism of polyurethane based on folding-unfolding of cyano-substituted oligo(p-phenylene)vinylene dimer

The incorporation of mechanophores,motifs that transform mechanical stimulus into chemical reaction or optical variation,allows creating materials with stressresponsive properties.The most widely used mechanophore generally features a weak bond,but its cleavage is typical an irreversible process.Here,we showed that this problem can be solved by folding–unfolding of a molecular tweezer.We systematically studied the mechanochromic properties of polyurethanes with cyano-substituted oligo(p-phenylene)vinylene(COP)tweezer(DPU).As a control experiment,a class of polyurethanes containing only a single COP moiety(MPU)was also prepared.The DPU showed prominent mechanochromic properties,due to the intramolecular folding–unfolding of COP tweezer under mechanical stimulus.The process was efficient,reversible and optical detectable.However,due to the disability to form either intramolecular folding or intermolecular aggregation,the MPU sample was mechanical inert.

Thiourea Based Tweezer Anion Receptors for Selective Sensing of Fluoride Ions

Three 3,3＇-di（4-substituted-phenyl）-1,1＇-isophthaloylbis（thiourea） compounds were designed as novel neutral anion receptors, and synthesized by simple steps in good yields. The single crystal structure of receptor 1 shows that a solvent molecule was captured by the host molecule through intermolecular hydrogen bonding. Moreover, it was self-assembled as a supramolecular system for the presence of abundant inter- and intramolecular hydrogen bonding and π-π interactions between phenyl groups. Their application as anion receptors has been examined by UV-Vis and ^1H NMR spectroscopy, showing that they had a higher selectivity for fluoride than other halides. The host and guest formed a 1 ： 1 stoichiometry complex through hydrogen bonding interactions in the first step, then following a process of deprotonation in presence of an excess of F^- in the solvent of DMF.