Cyclotriveratrylene Research Articles

Novel diphenylacrylonitrile-decorated cyclotriveratrylene columnar liquid crystals with high fluorescence

ABSTRACT Although some cyclotriveratrylene (CTV) liquid crystals had been reported, the CTV liquid crystal with high fluorescence in mesophase was not presented up to now. By introducing diphenylacrylonitrile units on CTV skeleton, two CTV derivatives with AIE units (7a and 7b) were prepared for the first time. Their structures and crown conformations were characterised by 1H NMR, 13C NMR, MALDI-MS spectra and elemental analysis. Samples 7a and 7b exhibited the reversible liquid crystalline behaviours with hexagonal columnar mesophase supported by the DSC, POM and XRD analysis. The studies on photophysical properties of samples 7a and 7b suggested the high fluorescence in solid state and mesophase. The absolute fluorescence quantum yield of 7b in mesophase was as high as 0.45. This work not only reported the first CTV liquid crystals with high fluorescence in aggregated state but also provided a good strategy for constructing the novel CTV liquid crystals with excellent fluorescence.

Ditopic Covalent Cage for Ion-Pair Binding: Influence of Anion Complexation on the Cation Exchange Rate.

A new hemicryptophane host with a ditopic molecular cavity combining a cyclotriveratrylene (CTV) unit with a tris-urea moiety was synthesized. The complexation of halides, tetramethylammonium (TMA+) cation, and ion pairs was investigated. A positive cooperativity was observed, since halides display a higher binding constant when a TMA+ cation is already present inside the cage. When TMA+ was complexed alone, a decrease of temperature from 298 K to 230 K was required to switch from a fast to a slow exchange regime on the NMR time scale. Nevertheless, the prior complexation of a halide guest in the lower part of the host resulted in significant decrease of the exchange rate of the subsequent complexation of the TMA+ cation. Under these conditions, the 1H NMR signals characteristic of a slow exchange regime were observed at 298 K. Addition of an excess of salts, increases the ionic strength of the solution, restoring the fast exchange dynamics. This result provides insight on how the exchange rate of a cation guest can be modulated by the complexation of a co-guest anion.

Chiral Molecular Cages Based on Cyclotriveratrylene and Sucrose Units Connected with p‐Phenylene Linkers

AbstractFour diastereomeric molecular cages based on cyclotriveratrylene (CTV) and sucrose scaffolds, connected via p‐phenylene linkers, were synthesized in a few steps synthesis. The absolute configuration of these diastereoisomers was determined by advanced NMR and ECD spectroscopies supported by DFT calculations. The X‐Ray crystal structure of P‐4 b cage gave an insight into its unique structure. The binding properties of P‐4 a and M‐4 a cages towards small ammonium guests (1‐methylpyridinium and 1,3‐dimethylimidazolium salts) were investigated.

Synthesis, resolution, and chiroptical properties of hemicryptophane cage controlling the chirality of propeller arrangement of a C3 triamide unit.

The five-steps synthesis of a hemicryptophane cage combining a benzene-1,3,5-tricarboxamide unit and a cyclotriveratrylene (CTV) moiety is described. Chiral high-performance liquid chromatography (HPLC) was used to resolve the racemic mixture. The absolute configuration of the isolated enantiomers was assigned by comparison of the experimental electronic circular dichroism (ECD) spectra with the calculated ones. X-ray molecular structures reveal that the capped benzene-1,3,5-tricarboxamide unit adopts a structurally chiral conformation in solid state: the chirality of CTV moiety controls the Λ or Δ orientation of the three amides.

Synthesis of Cyclotriveratrylene-Sucrose-Based Capsules.

Cyclotriveratrylene (CTV) is a C3-symmetrical macrocycle, which can be used as a chiral building block in the construction of supramolecular containers. Coupling of the CTV unit with a sucrose molecule gave enantiopure water-soluble (after deprotection) containers. The absolute configuration of the synthesized capsules was determined by NMR and ECD spectroscopies and DFT calculations.

High-Relaxivity Gd(III)-Hemicryptophane Complex.

The polytopic hemicryptophane cage HC1 combining a cyclotriveratrylene (CTV) unit and a tris(2-aminoethyl)amine (tren) moiety connected by three 2-hydroxyisophthalamide linkers was synthesized in 12 steps. The resulting highly functionalized covalent host is soluble in aqueous medium and has been used to complex Gd(III) ion. The Gd(III)@HC1 complex presents promising relaxivity properties when compared to the clinically used Dotarem MRI agent.

Molecular recognition by a novel boronate-containing CTG derivative for hydroxyanthraquinones

C3-functionalized cyclotriguaiacylene (CTG) derivatives were employed in the development of highly selective recognition compounds due to their unique molecular structures. Here, a novel C3-functionalized CTG containing boronate (PPB-CTG) was synthesized and its molecular recognition ability for hydroxyanthraquinones was investigated by fluorescence spectroscopy. The addition of the synthesized PPB-CTG led to a large increase in the fluorescence intensity of only alizarin and not 1-hydroxyanthraquinone, 2-hydroxyanthraquinone nor quinizarin. It was, thus, suggested that the cyclotriveratrylene (CTV) structure plays an important role in the recognition ability toward alizarin since the mono-phenyl boronate compound (m-TPBAP) showed poor fluorescence properties toward alizarin. Moreover, it was found that the 1:1 mixture of PPB-CTG and alizarin was effective as a fluorescence-enhanced probe toward fluoride ions.

A C3-substituted cyclotriveratrylene derivative with 8-quinolinyl groups as a fluorescence-enhanced probe for the sensing of Cu2+ ions.

C 3-Substituted cyclotriveratrylene (CTV) derivatives were considered suitable candidates for recognition compounds due to their unique structures. In this study, a C3-substituted CTV derivative with three fluorogenic 8-quinolinyl groups (1) was designed and prepared as a fluorescent probe. The synthesized CTV derivative 1 exhibited a selective response of fluorescence enhancement toward Cu2+ ions among the examined cations. The sensing ability of CTV derivative 1 toward Cu2+ ions was superior to that of the previously reported C3-substituted CTV derivative with three 2-quinolinyl groups (2). It is, thus, suggested that the CTV structure plays an important role in selective sensing ability toward Cu2+ ions since the mono-quinoline compound 5 showed fluorescence properties toward the Cr3+, Fe2+ and Fe3+ ions in addition to Cu2+ ions. In other words, the high Cu2+ ion-selectivity of CTV derivative 1 was demonstrated even in the presence of other co-existing examined cations. Moreover, it was found that CTV derivative 1 could work as a reversible fluorescence-enhanced probe toward Cu2+ ions by the simple addition of Et3N.

Enantiopure C1-Cyclotriveratrylene with a Reversed Spatial Arrangement of the Substituents.

Cyclotriveratrylene (CTV) is a macrocyclic cyclophane presenting a bowl-shaped conformation, used as building block to construct cryptophane and hemicryptophane capsules. A method to synthesize new enantiopure CTV derivatives with an unprecedented spatial arrangement of their substituents, exhibiting C1 symmetry, is described. The absolute configuration was assigned by ECD spectroscopy coupled with modeling. A statistical model has allowed for optimization of the proportion of C1 CTV, and the modularity of this approach is also highlighted.

Helical Chirality Induces a Substrate-Selectivity Switch in Carbohydrates Recognitions.

A new chiral hemicryptophane cage combining an electron-rich cyclotriveratrylene (CTV) unit and polar amine functions has been synthesized. The resolution of the racemic mixture has been performed by chiral HPLC, and the assignment of the absolute configuration of the two enantiomers has been achieved using ECD spectroscopy. In contrast with other hemicryptophane receptors, the two enantiomeric hosts display both remarkable enantioselectivities in the recognition of carbohydrates and good binding constants. Moreover, by switching the chirality of the CTV unit from M to P, a strong preference shift from glucose to mannose derivatives is observed.

How does chiral self-sorting take place in the formation of homochiral Pd6L8 capsules consisting of cyclotriveratrylene-based chiral tritopic ligands?

The chiral self-sorting process during the self-assembly of homochiral Pd6L8 capsules from cyclotriveratrylene (CTV)-based chiral tritopic ligands (L) and (Py*: 3-chloropyridine) was investigated by an NMR-based approach (QASAP: quantitative analysis of the self-assembly process). From the beginning to the formation of the immature capsules (ICs), enantiomeric ligands are distributed in the intermediates in a non-self-sorting manner, which leads to the isomers of heterochiral ICs over 99% yield. The mismatch of the chirality in the heterochiral ICs prevents intramolecular ligand exchanges in ICs to form the heterochiral capsules. The correction of the chirality in the heterochiral ICs (chiral self-sorting) takes place very slowly to finally lead to the homochiral capsules. The reason why the chiral self-sorting took place in the late stage of the self-assembly (after the formation of the heterochiral ICs) would be due to the relatively high flexibility of the CTV-based ligand.

An orthogonally protected CycloTriVeratrylene (CTV) as a highly pre-organized molecular scaffold for subsequent ligation of different cyclic peptides towards protein mimics

The synthesis of a semi-orthogonally protected CycloTriVeratrilene (CTV) scaffold derivative as well as the sequential introduction of three different peptide loops onto this molecular scaffold via Cu(I)-catalyzed azide alkyne cycloaddition towards a medium-sized protein mimic is described. This approach for the construction of medium-sized protein mimics is illustrated by the synthesis of a paratope mimic of the monoclonal antibody Infliximab (Remicade®) and provides access to a range of highly pre-organized molecular constructs bearing three different peptide segments. This approach may find wide applications for development of protein-protein interaction disruptors as well as synthetic vaccines.

Self-assembled Cages and Capsules Using Cyclotriveratrylene-type Scaffolds

Pyramidal molecular hosts related to cyclotriveratrylene (CTV) form self-assembled cages including organic cages, hydrogen-bonded cages, and metallocages. The latter include M3L2, M4L4, M6L8, and M12L8 assemblies, including topologically complicated structures. Metallocages may show ligand exchange and/or homochiral sorting of the C3-symmetric CTV-analog ligands. Cages also occur within coordination networks.

Closed vs Open‐Shell CTV Based Host Compounds: A Direct Comparison

AbstractNew hemicryptophane compounds combining a cyclotriveratrylene (CTV) unit, three binaphthol moieties in the linkers and closed by a simple benzene unit have been synthesized enantiomerically and diastereomerically pure. Assignment of their absolute configuration was achieved by chemical correlation. These closed shell host compounds were then tested in the recognition of carbohydrates and compared with their open‐shell counterparts. Closing the molecular cage induces a slight drop in affinity, associated with an improvement in the stereoselectivity of the recognition process, probably related to the higher preorganization of the cage compounds.

Incarceration of Higher-Order Fullerenes within Cyclotriveratrylene-Based Hemicarcerands Allows Selective Isolation of C76 , C78 , and C84 from a Commercial Fullerene Mixture.

Size-complementary cyclotriveratrylene (CTV)-based hosts can incarcerate C76 , C78 , and C84 , thus allowing the selective isolation of these higher-order fullerenes from a commercially available mixture of fullerenes. The hemicarceplexes, formed after the encapsulation of the size-complementary fullerenes within the hosts, are isolated by column chromatography and released at elevated temperature, thereby leading to the isolation of C76 /C78 and C84 in good purities (up to 95 and 88 %, respectively).

Cyclotriveratrylene-BINOL-Based Host Compounds: Synthesis, Absolute Configuration Assignment, and Recognition Properties.

New host compounds combining a cyclotriveratrylene (CTV) unit and three binaphthol moieties have been synthesized enantiomerically and diastereomerically pure. The use of a chemical correlation allows for the assignment of their absolute configuration. The energy barrier of epimerization was measured, suggesting that no intramolecular hydrogen bonding occurs between the hydroxyl groups of the binaphthols. These open-shell host compounds were then tested in the recognition of carbohydrates; a preferential binding of mannose toward glucose was observed, and good diastereoselectivities were reached (up to 1:10). This recognition of sugar derivatives by open-shell CTV-based host compounds is unprecedented and opens up the way for a wider use of this easily accessible class of molecules as chiral sensors.

ChemInform Abstract: Controlling the Assembly of Cyclotriveratrylene‐Derived Coordination Cages

AbstractReview: 85 refs + subrefs.

Cyclotriveratrylene as a new-type stationary phase for gas chromatographic separations of halogenated compounds and isomers

Cyclotriveratrylene (CTV) is reported here for the first time as stationary phase for capillary gas chromatographic (GC) separations. CTV stationary phase showed weak polarity comparable to the conventional 5% phenyl polysiloxane stationary phase but exhibited different retention behaviours and higher resolution for some of the indicated analytes. Most importantly, CTV stationary phase exhibited preferential selectivity for halogenated compounds, positional and geometrical isomers. Effect of column temperature on retention and thermal stability of CTV column were also investigated. Moreover, CTV capillary column showed good repeatability in terms of run-to-run, day-to-day and column-to-column. The unique physicochemical features and efficient separation ability for analytes of close properties show the potential of CTV as a new-type stationary phase in GC as well as separation science.

Precursor Modified Electrodes: Electrochemical Detection of Captopril

AbstractA fast and facile method for captopril determination is reported using an electrode modified to contain the precursor of a species which can selectively and suitably detect the target. Cyclotriveratrylene (CTV) is first incorporated into a carbon paste electrode then the precursor is converted into cyclotricatechylene (CTC) using voltammetric methods at the point in time when the captopril detection is sought. The resulting cyclotricatechylene (CTC) was used to mediate the electrochemical detection of the thiol containing drug, captopril, via electrocatalytic oxidation. Optimization towards the detection method was investigated by changing experimental conditions including pH and mediator loading. Optimal analytical parameters were determined in acidic conditions which gave a real measurable limit of detection of 1 µM for captopril detection.

Remote control of helical chirality: thermodynamic resolution of a racemic mixture of CTV units by remote stereogenic centers.

Enantiopure hemicryptophanes designed from the cyclotriveratrylene (CTV) unit display remarkable properties in selective host-guest recognition or as supramolecular catalysts. The unprecedented control of the helical chirality of the CTV unit by remote stereogenic centers of a tren moiety is reported, providing an original access to this highly promising class of host molecules. Although the chiral centers and the CTV unit are separated by more than 10 Å, one single diastereomer is formed; the nature of the diastereoselective process is discussed and the procedure is exemplified using different enantiopure tren derivatives. This work also highlights the influence of the chirality of the CTV unit on the whole cage structure.