BINOL Units Research Articles

Flexible Anti‐Counterfeiting Circularly Polarized Luminescent Elastomer from Supramolecular Polyurethanes

AbstractSupramolecular polymers with circularly polarized luminescence (CPL) have promoted future intelligence development of polymer‐based materials for flexible display. However, preparing polymer‐based CPL materials with simultaneous enhanced luminescence dissymmetry factor (|glum|) and mechanical performance for industrial applications remains challenging. This work develops an eco‐friendly preparation method for preparing CPL elastomers from supramolecular polyurethanes bearing chiral fluorescent S (or R)‐1,1′‐Bi(2‐naphthol) (BINOL) groups in a solvent‐free system. Surprisingly, a polymer system containing 0.0028 mol% of chiral BINOL unit is sufficient to emit the significant CPL‐activity with a |glum| value of 2.30 × 10−2, appear a good mechanical toughness of 56.28 ± 3.9 MJ·m−3, thereby exhibit multiple flexible anti‐counterfeiting behaviors. The long‐range ordered microphase arrangement in polyurethanes is the key to improving both mechanical properties and |glum|. This is attributed to in‐situ additive polymerization of BINOL‐based isocyanate prepolymer and macromolecular polyols induced helical supramolecular structure, afforded solid‐state films with flexibility and chiral amplification. Furthermore, these results from Circular dichroism, CPL, Fourier transform infrared, X‐ray diffraction analyses, and atomic force microscope confirm the formation of long‐range ordered microphase arrangement through the synergistic effect of hydrogen bonding and π–π interactions. This work offers significant insights into the construction of CPL elastomers for developing novel flexible display materials.

Cascade Alkenylation/Intramolecular Friedel–Crafts Alkylation: High Selectivity at the C7-Position of BINOL

An efficient and straightforward approach for the synthesis of C7 site-selective BINOL derivatives has been achieved via cost-effective Co(III)-catalyzed C-H cascade alkenylation/intramolecular Friedel-Crafts alkylation of BINOL units and propargyl cycloalkanols. Under the advantage of the pyrazole directing group, the protocol allows the rapid synthesis of various BINOL-tethered spiro[cyclobutane-1,1'-indenes].

Light-Triggered Reversible Open-Close Motion of a Chiral Molecular Plier to Modulate Guest Binding.

A chiral molecular plier's design, synthesis, characterisation and operations are presented. The molecular plier encompasses three units: a BINOL unit which acts as a pivot as well as a chiral inducer, an azobenzene unit, which acts as a photo-switchable component and two zinc porphyrin, acting as a reporter. E to Z isomerisation persuaded by irradiating with 370 nm light alters the dihedral angle of the pivot BINOL unit, which adjusts the distance between two porphyrin units. The plier can be switched to its initial state by exposure to 456 nm light or heating at 50 °C. NMR, CD and molecular modelling supported the reversible switching and change in dihedral angle and distance between reporter moiety, which was further exploited for binding with several ditopic guests. The longest guest was found to form the strongest complex, R,R-isomer formed a stronger complex than S,S-isomer, Z-isomer of the plier formed stronger complex than the E-isomer with the guest. Moreover, complexation also increased the E-to-Z switching efficiency and decreased the thermal back isomerisation of the azobenzene unit.

C-O Coupling/[4+2] Cycloaddition Tandem Reactions via Oxidative Dearomatization of BINOLs: Access to Bridged Polycyclic Compounds.

Intramolecular C-H activation/C-O coupling, dearomatization, and [4+2] cycloaddition of BINOL units have been well developed in a one-pot approach with maleimide derivatives as the dienophiles. This tandem catalytic system generates a variety of functionalized bridged polycyclic products in a step-economical manner, which greatly enriches the modification methods and strategies for the BINOL skeletons.

BINOL-Containing Chiral Porous Polymers as Platforms for Enantiorecognition.

The enantioselective discrimination of racemic compounds can be achieved through the design and preparation of a new family of chiral conjugated BINOL-porous polymers (CBPPs) from enantiopure (R)- or (S)-BINOL derivatives and 1,3,5-tris(4-phenylboronic acid)benzene or 1,3,5-tris(4-ethynylphenyl)benzene, 1,3,5-triethynyl-2,4,6-trifluorobenzene, and tetra(4-ethynylphenyl)methane as comonomers following Suzuki-Miyaura and Sonogashira-Hagihara carbon-carbon coupling approaches. The obtained CBPPs show high thermal stability, a good specific surface area, and a robust framework and can be applied successfully in the fluorescence recognition of enantiomers of terpenes (limonene and α-pinene) and 1-phenylethylamine. Fluorescence titration of CBPPs-OH in acetonitrile shows that all Sonogashira hosts exhibit a preference for the (R)-enantiomer over the (S)-enantiomer of 1-phenylethylamine, the selectivity being much higher than that of the corresponding BINOL-based soluble system used as a reference. However, the Suzuki host reveals a preference toward (S)-phenylethylamine. Regarding the sensing of terpenes, only Sonogashira hosts show enantiodifferentiation with an almost total preference for the (S)-enantiomer of limonene and α-pinene. Based on the computational simulations and the experimental data, with 1-phenylethylamine as the analyte, chiral recognition is due to the distinctive binding affinities resulting from N···H-O hydrogen bonds and the π-π interaction between the host and the guest. However, for limonene, the geometry of the adsorption complex is mostly governed by the interaction between the hydroxyl group of the BINOL unit and the C═C bond of the iso-propenyl fragment. The synthetic strategy used to prepare CBPPs opens many possibilities to place chiral centers such as BINOL in porous polymers for different chiral applications such as enantiomer recognition.

Iridium(iii)-catalyzed two-fold C–H alkylation of BINOLs with allyl alcohols

Ir(iii)-Catalyzed C–H alkylation of BINOL units has been well examined by using allyl alcohols as coupling partners.

Theoretical Investigation of the Circularly Polarized Luminescence of a Chiral Boron Dipyrromethene (BODIPY) Dye.

Over the last decade, molecules capable of emitting circularly polarized light have attracted growing attention for potential technological and biological applications. The efficiency of such devices depend on multiple parameters, in particular the magnitude and wavelength of the peak of emitted light, and also on the dissymmetry factor for chiral applications. In light of these considerations, molecular systems with tunable optical properties, preferably in the visible spectral region, are particularly appealing. This is the case of boron dipyrromethene (BODIPY) dyes, which exhibit large molecular absorption coefficients, have high fluorescence yields, are very stable, both thermally and photochemically, and can be easily functionalized. The latter property has been extensively exploited in the literature to produce chromophores with a wide range of optical properties. Nevertheless, only a few chiral BODIPYs have been synthetized and investigated so far. Using a recently reported axially chiral BODIPY derivative where an axially chiral BINOL unit has been attached to the chromophore unit, we present a comprehensive computational protocol to predict and interpret the one-photon absorption and emission spectra, together with their chiroptical counterparts. From the physico-chemical properties of this molecule, it will be possible to understand the origin of the circularly polarized luminescence better, thus helping to fine-tune the properties of interest. The sensitivity of such processes require accurate results, which can be achieved through a proper account of the vibrational structure in optical spectra. Methodologies to compute vibrationally-resolved electronic spectra can now be applied on relatively large chromophores, such as BODIPYs, but require more extensive computational protocols. For this reason, particular attention is paid in the description of the different steps of the protocol, and the potential pitfalls. Finally, we show how, by means of appropriate tools and approaches, data from intermediate steps of the simulation of the final spectra can be used to obtain further insights into the properties of the molecular system under investigation and the origin of the visible bands.

Rapid Synthesis of Alkenylated BINOL Derivatives via Rh(III)-Catalyzed C-H Bond Activation.

Modification of BINOL units has been well examined via Rh-catalyzed C-H activation and functionalization reactions by using ester carbonyls as directing groups and alkenes as coupling partners. The one-pot strategy was an efficient protocol for the rapid synthesis of BINOL derivatives with retention of optical purity.

Synthesis of Bis-BINOL Derivatives: Linking via the 3-, 4-, or 5-Position by Generation of Suitable C 1-Symmetric Precursors

Bis-BINOL derivatives have proven highly useful in applications such as chemosensing or organocatalysis. In this account, we describe strategies for the linking of BINOL units via the 3-, 4-, or 5-positions, showing that unique synthetic strategies are necessary to address each position. We report the synthesis of suitable C 1-symmetric precursors, which are generated either by monohalogenation or by monodeprotection of C 2-symmetric starting materials, and their subsequent coupling to give linked bis-BINOL derivatives.

A simple but effective ferrocene derivative as a redox, and fluorescent receptor for highly selective recognition of Al3+ ions

A new probe, based on BINOL and ferrocene unit, senses Al3+ selectively among a variety of metal cations. Through different channels: anodic redox shift of the Fe(II)/Fe(III) redox couple, and a remarkable enhancement of the fluorescence. This fluorescence recognition of Al3+ also shows color changes under a UV lamp. Mass and NMR spectroscopic analyses have been used to study the mechanism, which indicates the formation of [1 + 2] complexes.

Naphthalimide‐Based Chiral Fluorescence Sensor Employing (S)‐BINOL Unit for Highly Enantioselective Recognition of α‐Amino Alcohols with Opposite Chiral Selectivity

AbstractA new naphthalimide‐based fluorescent probe [(S)‐1 and (S)‐2] employing (S)‐BINOL unit as a chiral responsive group has been designed and synthesized. Ligand (S)‐1 showed greater fluorescence enhancement towards (R)‐amino alcohol and the value of enantiomeric fluorescence difference (ef) ratio reached as high as 7.07 for phenylalaninol while (S)‐phenylalaninol did not show much enhancement in fluorescence, whereas ligand (S)‐2 showed ef value of 4.49 for phenylalaninol. The fluorescence enhancement can be attributed to imine formation and H‐bonding. Further, the R/S chiral selectivity of ligands (S)‐1 and (S)‐2 is opposite. The chiral discrimination ability of (S)‐1 and (S)‐2 was tested via fluorescence, NMR and CD spectral analysis. The results indicated that the sensor (S)‐1 was very promising for use as a fluorescent sensor in determining the enantiomeric composition of α‐amino alcohols.

Crystal structure of tris(binol)cyclotriphosphazene. A new clathration system

The crystal structure of inclusion compound constituted by chiral tris(binol)cyclotriphosphazene ((S,S,S)-TBP) host and o-xylene guest has been determined. It has an orthorhombic unit cell with space group P212121 (no. 19) and unit cell dimensions a=10.9265(4)Å, b=17.8959(8)Å, and c=30.3964(1)Å. Guest free (S,S,S)-TBP is an amorphous material according to the literature (Chem. Eur. J.2001, 7, 1486–1494) and crystal structure has not been reported so far. Formation of inclusion adduct with o-xylene guests acting as a molecular glue allowed to determine the structural features. (S,S,S)-TBP has a propeller-like shape with binol units considered as paddles. Naphthalene units are twisted at 51° in those paddles. Effects of this twist on spirocyclic seven-membered ring and on cyclotriphosphazene ring are discussed.

New chiral diphosphoramidite rhodium(I) complexes for asymmetric hydrogenation

Chiral 1,5‐cyclooctadiene rhodium(I) cationic complexes with C2‐symmetric chelate diphosphoramidite ligands containing (R,R)‐1,2‐diaminocyclohexane as the backbone and two atropoisomeric biaryl units were easily synthesized and fully characterized by multinuclear one‐ and two‐dimensional NMR spectroscopy and elemental analysis. These complexes were used as catalysts in the asymmetric hydrogenation of dimethyl itaconate, methyl 2‐acetamidoacrylate and (Z)‐methyl‐2‐acetamido‐3‐phenylacrylate. The rhodium complexes derived from diphosphoramidite ligands that contain two (R) or (S) BINOL (2,2′‐dihydroxy‐1,1′‐binaphthyl) units proved to be efficient catalysts, giving complete conversion and very good enantioselectivity (up to 88% ee). An uncommon positive H2 pressure effect on the enantioselectivity was observed in the hydrogenation of dimethyl itaconate catalyzed by Rh‐complex with diphosphoramidite ligand that contains two (S)‐binaphthol moieties. Copyright © 2014 John Wiley & Sons, Ltd.

Stereoselective Di-pi-Methane Rearrangement of a BINOL-Substituted Dibenzobarrelene Derivative

Abstract Two dibenzobarrelene derivatives were synthesized that are covalently linked to a (S)-BINOL unit through an oxymethylene (1b) or ethylenedioxymethylene (1c) unit, and their photoreactivity was examined. Irradiation of 1b in acetone resulted in a di-π-methane rearrangement to give diastereoselectively one dibenzosemibullvalene isomer. Experimental and theoretical data point to a directing effect of the BINOL auxiliary based on steric repulsion. The derivative 1c with a longer linker between the BINOL unit and the dibenzobarrelene is photoinert, presumably because of fast competing relaxation processes in the excited state.

キラルBINOL基を有するポリチオフェンナノチューブの合成と金ナノ粒子の包接

We report the preparation of chiral polymer nanotubes bearing terthiophene and BINOL units [(S)-TBOH-PNTs] and the encapsulation of metal nanoparticles (NPs) therein. The monomer, (S)-TBOH, was synthesized by coventional methods and electrochemically polymerized using porous alumina with a pore diameter of 200 nm on a platinum electrode. The electrolyte solution contained 7mM monomer [(S)-TBOH] and 0.1M Bu4NPF6 in CH2Cl2. A voltage of 1.00 V was applied for polymerization. The porous alumina was removed by dissolving in NaOH. The UV-vis spectrum of the PNTs in C2HCl2 exhibited a broad absorption peak at 425 nm which is ascribed to the polythiophene. The CD spectra of (S)-TBOH-PNTs and (R)-TBOH-PNTs, show intense Cotton effects and a mirror-image relationship. The PNTs and the encapsulated Au NPs in PNTs (Au NPs@(S)-TBOH-PNTs) were characterized by SEM, TEM and EDX analysis.

Synthesis, photophysical and electrochemical properties of chiral and achiral thiadiazolophanes

One pot synthesis of chiral and achiral 2:2 oligomeric thiadiazolophane 1 and 3 and 3:3 oligomeric thiadiazolophane 2 and 4 with (S)-BINOL and methylene bis-naphthyl spacer unit has been achieved. The photophysical and electrochemical properties revealed higher degree of aggregation in 2:2 oligomor than 3:3 oligomer. Energy minimized calculations show that 3:3 oligomer has less heat of formation than 2:2 oligomer.

キラルリン酸触媒反応における反応制御·立体制御機構に関する理論的研究

The chiral BINOL-phosphoric acid is a well-designed asymmetric organocatalyst because it features the bifunctionality of the Brønsted acid (proton)/base (phosphoryl oxygen) and the conformational rigidity of the 3,3-substituents of the BINOL unit controlling the stereoselectivity through the hydrogen bonding network. Though the bifunctional activation has emerged as an important paradigm of chiral phosphoric acid catalyzed asymmetric reactions, it has remained elusive in most cases. Recently, we revealed the reaction mechanism as well as the stereocontrol mechanism by our computational two-step approach using (1) simplified chemical model and (2) realistic chemical model.

Connecting BINOL and terpyridine: the electronic effects of the linkage

1,1′-Bi-2-naphthol and terpyridine are covalently connected either directly or through different linkers. It is found that in contrast to the directly connected one, when the saturated methyleneoxy linker is used, there is inefficient electronic communication between the BINOL and terpyridine units and the fluorescence of the BINOL unit cannot be completely quenched by the coordination of terpyridine unit with a Cu 2+ ion. However, a phenylene linker allows an efficient electronic communication between the BINOL and terpyridine units and the fluorescence of the BINOL is almost completely quenched upon Cu 2+ coordination. The interaction of these compounds with valinol is studied and large fluorescence enhancements are observed for those with efficient electronic communication between the BINOL and terpyridine units.

Study of the Fluorescent Properties of Partially Hydrogenated 1,1′-Bi-2-naphthol-amine Molecules and Their Use for Enantioselective Fluorescent Recognition

The fluorescent properties of a series of H(8)BINOL-amine compounds are investigated. It is revealed that the intramolecular hydrogen bonds of these compounds contribute to the shift of the emission of their H(8)BINOL unit to a much longer wavelength. That is, the emission of H(8)BINOL is at λ = 323 nm, but that of the H(8)BINOL-amino alcohol (S)-5 is at λ = 390 nm. Binding of (S)-5 with mandelic acid suppresses its intramolecular hydrogen bonding and restores the short wavelength emission of the H(8)BINOL unit. When (S)-5 (1.0 × 10(-4) in CH(2)Cl(2)) was treated with (R)-mandelic acid (4.0 × 10(-3)), a large fluorescence enhancement at the short wavelength (λ(emi) = 330 nm) was observed with I(R)/I(0) = 11.7. When (S)-MA was used under the same conditions, the enhancement at the short wavelength emission was much smaller. Thus, a good enantioselective fluorescent response was observed with ef =3.5 [ef: enantioselective fluorescence enhancement ratio = (I(R) - I(0))/(I(S) - I(0))]. This study demonstrates that the H(8)BINOL-based molecules are promising as a new class of enantioselective fluorescent sensors.

Recognition of Achiral and Chiral Ammonium Salts by Neutral Ditopic Receptors Based on Chiral Salen-UO2 Macrocycles

A mononuclear (M20) and a dinuclear (M40) uranyl chiral macrocyclic complex, incorporating both a salen unit containing two phenyl rings linked to a chiral diimine bridge and the (R)-BINOL unit, behaves as an efficient ditopic receptor for achiral and chiral quaternary ammonium salts. Binding affinities in chloroform solution have been measured for 1:1 complexes of many quaternary salts encompassing tetramethylammonium (TMA), tetraethylammonium (TEA), tetrabutylammonium (TBA), and acetylcholine (ACh), as well as trimethylanilinium (TriMAn), benzyltrimethylammonium (BnTriMA), (alpha-methylbenzyl)trimethylammonium and pyrrolidinium cations. The anion of the salt is bound by the hard Lewis acidic uranyl site, with an increasing binding efficiency on increasing the anion hardness (I(-) < Br(-) < Cl(-)), whereas CH-pi or pi-pi attractions by binapthyl moiety, or the salicylaldehyde unit, or the phenyl rings of diimine bridge ensure the recognition of the cation partner. Optimized structures of receptor-anion-cation ternary complexes obtained by MM calculations are supported by 2D-ROESY NMR measurements.