Central Naphthalene Research Articles

Effect of substituents of naphthalene diimide derivatives on electrochromic behaviours observed in proto-type devices

Several triphenylamine end capped to substituted central naphthalenetetracarboxylic diimide based four donor - acceptor - donor type electro-active monomers (BRTPANDI, CNTPANDI, PHTPANDI, NPYTPANDI) were designed and developed to explore the effect of substituent on the formation of electro-polymers and subsequent the chromic effect of prepared films on the conductive surface. Initially, with the help of density functional theory (DFT) studies, it was observed that HOMO was located over triphenylamine unit, responsible electro-polymerization process upon oxidation, LUMO was residing on the central naphthalene core, and all substituents were not coplanar with naphthalene moiety. Also, the band gap energy was gradually decreased with the effect of strong electron withdrawing substituents on NDI core. In three electrode configuration, reversible multiple colour changes of brown to deep blue by applying voltage 0 to 1.1 V and also brown to deep pink with the voltage change of 0 to −2 V were impressively investigated with relatively good response times, optical contrast, switching stabilities, and coloration efficiencies. Polymer made of CNTPANDI might be switched upto 1200 cycles with the optimum colouration efficiency 560 cm2/C in the anodic process and 300 cycles for the cathodic process in a three electrodes configuration. Proto type devices made of p-CNTPANDI demonstrated the electrochromism operated at a potential range of 0 to 2.2 V. Besides, the device exhibited the EC memory in open-circuit condition with 50% retention of its coloured state until 27 min. The long EC memory as well as high colouration efficiency compared to other TPA based conjugated polymers suggested the potentiality of those polymer films as a power-efficient EC material for modern display applications.

Optimization of the C2 substituents on the 1,4-bis(arylsulfonamido)naphthalene-N,N′-diacetic acid scaffold for better inhibition of Keap1-Nrf2 protein-protein interaction

Direct inhibition of the protein-protein interaction (PPI) between Kelch-like ECH-associated protein 1 (Keap1) and nuclear factor erythroid 2-related factor 2 (Nrf2) reduces the ubiquitination and subsequent degradation of Nrf2, leading to Nrf2 accumulation in the cytosol and the nuclear translocation of Nrf2. Once inside the nucleus, Nrf2 binds to and activates the expression of antioxidant response element (ARE) genes involved in redox homeostasis and detoxification. Herein, we report a series of 1,4-bis(arylsulfonamido)naphthalene-N,N′-diacetic acid analogs with varying C2 substituents to explore the structure-activity relationships at this position of the central naphthalene core. The Keap1-binding activities were first screened with a fluorescence polarization (FP) assay followed by further evaluation of the more potent compounds using a more sensitive time-resolved fluorescence energy transfer (TR-FRET) assay. It was found that compound 24a with C2-phthalimidopropyl group was the most potent in this series showing an IC50 of 2.5 nM in the TR-FRET assay with a Ki value in the subnanomolar range. Our docking study indicated that the C2-phthalimidopropyl group in compound 24a provided an extra hydrogen bonding interaction with the key residue Arg415 that may be responsible for the observed boost in binding affinity. In addition, compounds 12b, 15, and 24a were shown to activate the Nrf2 signaling pathway in NCM460D cells resulting in elevated mRNA levels of GSTM3, HMOX1 and NQO1 by 2.4–11.7 fold at 100 μM as compared to the vehicle control.

Arylene Diimide Derivatives as Anolyte Materials with Two-Electron Storage for Ultrastable Neutral Aqueous Organic Redox Flow Batteries

Arylene Diimide Derivatives as Anolyte Materials with Two-Electron Storage for Ultrastable Neutral Aqueous Organic Redox Flow Batteries

1,8‐Diarylnaphthalenes: Synthesis, Properties, and Applications

Abstract1,8‐Diarylnaphthalenes are a fascinating example of strained organic molecules that have found many practical applications due to unusual parallel face‐to‐face arrangement of two peri‐aryl rings in close proximity almost perpendicular to the central naphthalene backbone. 1,8‐Diarylnaphthalenes show notable potential as photoluminescent and chiral sensors, stereodynamic switches, nonlinear optic chromophores, blue‐transparent frequency doublers, materials for creating high‐performance blue and green OLEDs, chiral ligands and so on. Molecules of this type have also been used as convenient models for studying π‐π, dipole‐π and cation‐π interactions. 1,8‐Diarylnaphthalenes are also interesting as objects to study atropisomeric transformations: if the peri‐aryl rings have ortho‐ or meta‐substituents, then the anti‐conformer becomes C2‐symmetrical (hence chiral), and the syn‐isomer upon symmetrical substitution is achiral. In this review, data on synthetic methods, applications, atropisomerism and structural characteristics of 1,8‐diaryl‐ and 1,8‐dihetarylnaphthalenes are summarized.

Mechanical Force Enables an Anomalous Dual Ring-Opening Reaction of Naphthodipyran.

Multimodal mechanophores that exhibit complex mechanochromic behavior beyond the typical binary response are capable of distinguishing between multiple stress states through discrete changes in color. Naphthodipyran photoswitches contain two pyran rings fused to a central naphthalene core and represent a potentially promising framework for multimodal reactivity. However, the concurrent ring opening of both pyran moieties has previously proven inaccessible via photochemical activation. Here, we demonstrate that mechanical force supplied to naphthodipyran through covalently linked polymer chains generates the elusive dual ring-opened dimerocyanine product with unique near-infrared absorption properties. Trapping with boron trifluoride renders the merocyanine dyes thermally persistent and reveals apparent sequential ring-opening behavior that departs from the reactivity of previously studied mechanophores under the high strain rates imposed by ultrasound-induced solvodynamic chain extension.

Synthetic, Mesomorphic, and DFT Investigations of New Nematogenic Polar Naphthyl Benzoate Ester Derivatives.

Four new non-symmetrical derivatives based on central naphthalene moiety, 4-((4–(alkoxy)phenyl) diazenyl)naphthalen–1–yl 4–substitutedbenzoate (In/x), were prepared, and their properties were investigated experimentally and theoretically. The synthesized materials bear two wing groups: an alkoxy chain of differing proportionate length (n = 6 and 16 carbons) and one terminal attached to a polar group, X. Their molecular structures were elucidated via elemental analyses and FT-IR and NMR spectroscopy. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) were carried out to evaluate their mesomorphic properties. The results of the experimental investigations revealed that all the synthesized analogues possess only an enantiotropic nematic (N) mesophase with a high thermal stability and broad range. Density functional theory (DFT) calculations were in accordance with the experimental investigations and revealed that all prepared materials are to be linear and planar. Moreover, the rigidity of the molecule increased when an extra fused ring was inserted into the center of the structural shape, so its thermal and geometrical parameters were affected. Energy gap predictions confirmed that the I16/c derivative is more reactive than other compounds.

Synthesis, mesomorphic and geometrical approaches of new non-symmetrical system based on central naphthalene moiety

ABSTRACT New non-symmetrical homologues series based on central naphthalene moiety, (E)-4-(4-(hexyloxy phenyl diazenylnaphthalene-1-yl-4ʹ-alkoxybenzoate (I 6/n), were synthesised and their mesomorphic properties was investigated. The prepared group constitutes four homologues bearing two terminal alkoxy chains of different proportionation. Elemental analyses, FT-IR and NMR spectroscopy were carried out to elucidate their molecular structures. Examination of their mesomorphic properties, were conducted via differential scanning calorimetry (DSC) and polarised optical microscopy (POM). DSC and POM investigations indicated that all the synthesised homologues are monomorphic possessing the enantiotropic nematic (N) phase. A comparative study was conducted between the present investigated central naphthalene series (I 6/n) and their corresponding central benzene analogues (II 6/n). The results indicated that, the mesophase type and stability as well as the mesophase temperature are affected by the protrusion of the naphthalene group. Theoretical calculations are in accordance with the experimental values of the investigated series. Moreover, the location of naphthalene group in the centre of the molecular geometry, increases the rigidity of the molecule, thus affects their thermal and physical parameters. The experimentally determined nematic stability was correlated with the calculated parameters and the study reveals that there are many factors sharing together to different extents in the enhancement of the behaviour of the observed nematic phase, depending on the different proportionation of the terminal lengths.

Influence of terminally attached branched alkyloxy chains on the mesophase behaviour of calamitic liquid crystals

ABSTRACT Three sets of new rod-shaped liquid crystals with one terminal fixed branched alkyl chain, other terminal with varying normal alkyl chain, and central naphthalene with terminal branched chain derived symmetric molecules were synthesized and characterized. Chemical structures were confirmed by standard analytical methods. Liquid crystal properties were evaluated with the help of differential scanning calorimetry, polarized optical microscopy and X-ray studies. All the compounds favoured to exhibit highly birefringent smectic and nematic mesophase textures. Further, symmetric naphthalene derivatives preferably exhibited nematic mesophase with elevated transition temperatures.

Selective formation of spiroborate-based double-stranded hetero-helicates assisted by donor–acceptor interactions

A novel spiroborate-based double-stranded hetero-helicate is selectively formed through donor–acceptor interactions between the central electron-rich porphyrin and electron-deficient naphthalene diimide units.

Synthesis and self-assembly of 1,8-naphthalene-based hexacatenar mesogens

ABSTRACT A novel series of hexacatenars consisting of a central naphthalene core functionalised with 1,2,3-triazole dendritic wings at 1 and 8 positions were synthesised by Sonogashira coupling and Click reactions. POM, DSC and XRD investigations revealed that all hexacatenars could self-assemble into absolutely Colhex/p6 mm mesophase in the bulk state. Interestingly, these compounds could gel some organic solvents with low critical gelation concentration and the gel morphologies varied from 3D porous structures via nanofiber structures to 3D spherical aggregates with increasing polarity of solvents. These investigations provide a new strategy to generate supramolecular self-assembly materials.

Fluorescence Anisotropy Decay of Molecular Rotors with Acene Rotators in Viscous Solution.

Herein, we report the use of fluorescence anisotropy decay for measuring the rotation of six shape-persistent molecular rotors with central naphthalene (2), anthracene (3a, 3b, and 3c), tetracene (4), and pentacene (5) rotators axially linked by triple bonds to bulky trialkylsilyl groups of different sizes. Steady-state and time-resolved polarization measurements carried out in mineral oil confirmed that the vibrationally resolved lowest-energy absorption bands are characterized by a transition dipole moment oriented along the short acene axes, in the direction of the alkyne linkers. Fluorescence lifetimes increased significantly with increasing acene size and moderately with a decrease in the size of the trialkylsilyl group. The fluorescence anisotropy decay for all compounds in mineral oil with a viscosity of ca. 21.6 cP at 40 °C was completed within the fluorescence lifetime, so that the rotational time constants could be obtained via their rotational correlation times, which increased with silyl protecting group size rather than acene size, indicating that polarization decay is determined by tumbling of the molecular rotor about the long acene axis. These results suggest that monitoring the rotational motion of bis(silylethynyl)acenes in restricted media should be possible for media with viscosity values on the order of 21.6 cP or greater.

Nematic and switchable intercalated phases in polymerizable bent-core monomers with naphthalene moiety in the side arms of the aromatic core

Liquid crystals (LCs) formed by achiral bent-core (BC) molecules associated with chirality and polar order exhibit electro-optically switchable lamellar and columnar phases, and nematic phases which could be biaxial or polar. As polymeric LCs could have application in photonics and non-linear optics, BC monomers having naphthalene moiety in the side arms and linked with terminal double bonds as polymerizable functional groups were synthesized. 6B2 with a central phenyl ring and 6N2 with a central naphthalene moiety were investigated by optical, x-ray diffraction, dielectric and electro-optic studies. Possible reasons that can account for the exhibited phase transitions will be described.

Naphthalene Diimides Prepared by a Straightforward Method and Their Characterization for Organic Electronics

A new approach for the synthesis of acetylene‐substituted naphthalene diimides in polar solvents with PdCl2, Et3N, and electrolytic copper powder was developed. This simplified approach allows for high‐throughput synthesis, and the reaction products can be readily separated. DFT studies revealed that the electronic structures of these compounds are mainly determined by the central naphthalene diimide unit and the acetylene groups. The obtained thermally stable and soluble compounds undergo reversible reduction with electron affinities of 4.18 to 4.28 eV. They emit green light with photoluminescence quantum yields of ca. 6 % in chloroform and in the range 3–12 % as thin films. The compounds were applied as emitting layers for both nondoped and doped single‐layer organic light‐emitting diodes (OLEDs) fabricated by solution processing. Under an applied external voltage, they exhibit orange or red electroluminescence.

Mesogens with central naphthalene core substituted at various positions

ABSTRACTWe have prepared liquid crystalline materials based on hydroxynaphthalene carboxylic acids. The mutual location of both functional groups has been varied, which resulted in compounds possessing a bend angle of 120° and 60°, therefore in bent-core and V-shaped compounds, respectively. The mesomorphic properties have been established with polarizing optical microscopy, DSC measurements and X-ray investigation. The properties of the studied have been compared with analogous derivatives to establish the role of ester orientation in the vicinity of the central naphthalene core.

Electron Accumulation on Naphthalene Diimide Photosensitized by [Ru(2,2'-Bipyridine)3]2.

In a molecular triad comprised of a central naphthalene diimide (NDI) unit flanked by two [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) sensitizers, NDI2- is formed after irradiation with visible light in deaerated CH3CN in the presence of excess triethylamine. The mechanism for this electron accumulation involves a combination of photoinduced and thermal elementary steps. In a structurally related molecular pentad with two peripheral triarylamine (TAA) electron donors attached covalently to a central [Ru(bpy)3]2+-NDI-[Ru(bpy)3]2+ core but no sacrificial reagents present, photoexcitation only leads to NDI- (and TAA+), whereas NDI2- is unattainable due to rapid electron transfer events counteracting charge accumulation. For solar energy conversion, this finding means that fully integrated systems with covalently linked photosensitizers and catalysts are not necessarily superior to multicomponent systems, because the fully integrated systems can suffer from rapid undesired electron transfer events that impede multielectron reactions on the catalyst.

Non-fullerene acceptors based on central naphthalene diimide flanked by rhodanine or 1,3-indanedione.

Through the combination of central naphthalene diimide and terminal rhodanine or 1,3-indanedione functionalities, two new non-fullerene electron acceptors, coded as N3 and N4, were designed, synthesized and characterized. Both of the materials exhibited good solubility, thermal stability, and displayed energy levels matching those of the conventional and routinely used donor polymer poly(3-hexyl thiophene) (P3HT). A high power conversion efficiency of 4.76% was obtained in simple, solution-processable bulk-heterojunction devices (P3HT : N3 1 : 1.2) which is the best result for central NDI-based small molecular non-fullerene acceptors.

Effect of the ethynylene linker on the properties and carrier mobility of naphthalene derivatives with hexylbithienyl arms

A series of new naphthalene derivatives with (5′-hexyl-2,2′-bithiophene-5-yl)ethynyl side arms attached to the central naphthalene core at positions 1 and 4 (H2TA14N), 1 and 5 (H2TA15N), and 2 and 6 (H2TA26N) were synthesized by a sequencing of alkynylations performed according to a Negishi cross-coupling protocol. This synthetic approach provides higher yields compared to Sonogashira-based alkynylations, particularly when aryl bromides are used as starting materials. Compared to the analogous derivatives with hexylbithienyl arms directly attached to the naphthalene core (H2T14N, H2T15N, and H2T26N), an ethynylene linker ensures the planarity of the molecules, causing a change in the order of derivatives by intramolecular conjugation from H2T15N<H2T14N<H2T26N to H2TA15N≈H2TA26N<H2TA14N, as can be seen from the solution, and thin film optical and electrochemical properties as well. However, the order of derivatives by the hole mobility in a field effect transistor remains unaltered by an ethynylene linker (H2TA14N<H2TA15N<H2TA26N). The tendency in charge mobility can be explained by different packing motifs affected by molecular symmetry and was revealed by single crystal X-ray analysis and 2D X-ray GIWAXS and AFM characterization of the thin films.

Synthesis of Naphthalene-Based Push-Pull Molecules with a Heteroaromatic Electron Acceptor.

Naphthalene derivatives bearing electron-accepting and electron-donating groups at the 2,6-positions belong to the family of D-π-A push-pull dyes. It has been found that these compounds, e.g., 2-(1-(6-((2-(fluoro)ethyl)(methyl)amino)naphthalen-2-yl)ethylidene)malononitrile (FDDNP), show not only interesting optical properties, such as solvatochromism, but they have the potential to label protein aggregates of different compositions formed in the brain of patients suffering from neurodegenerative diseases like Alzheimer’s (AD). In continuation of our research we set our goal to find new FDDNP analogs, which would inherit optical and binding properties but hopefully show better specificity for tau protein aggregates, which are characteristic for neurodegeneration caused by repetitive mild trauma. In this work we report on the synthesis of new FDDNP analogs in which the acceptor group has been formally replaced with an aromatic five- or six-membered heterocycle. The heterocyclic moiety was annealed to the central naphthalene ring either by classical ring closure reactions or by modern transition metal-catalyzed coupling reactions. The chemical characterization, NMR spectra, and UV/vis properties of all new compounds are reported.

Dual Role of the 1,2,3-Triazolium Ring as a Hydrogen-Bond Donor and Anion-π Receptor in Anion-Recognition Processes.

Several bis(triazolium)-based receptors have been synthesized as chemosensors for anion recognition. The central naphthalene core features two aryltriazolium side-arms. NMR experiments revealed differences between the binding modes of the two triazolium rings: one triazolium ring acts as a hydrogen-bond donor, the other as an anion-π receptor. Receptors 9(2+)⋅2BF4(-) (C6H5), 11(2+)⋅2BF4(-) (4-NO2-C6H4), and 13(2+)⋅2BF(4-) (ferrocenyl) bind HP2O7(3-) anions in a mixed-binding mode that features a combination of hydrogen-bonding and anion-π interactions and results in strong binding. On the other hand, receptor 10(2+)⋅2 BF4(-) (4-CH3O-C6H4) only displays combined Csp2-H/anion-π interactions between the two arms of the receptors and the bound anion rather than triazolium (CH)(+)⋅⋅⋅anion hydrogen bonding. All receptors undergo a downfield shift of the triazolium protons, as well as the inner naphthalene protons, in the presence of H2PO4(-) anions. That suggests that only hydrogen-bonding interactions exist between the binding site and the bound anion, and involve a combination of cationic (triazolium) and neutral (naphthalene) C-H donor interactions. Theoretical calculations relate the electronic structure of the substituent on the aromatic group with the interaction energies and provide a minimum-energy conformation for all the complexes that explains their measured properties.

The Impact of Antiaromatic Subunits in [4n+2] π-Systems: Bispentalenes with [4n+2] π-Electron Perimeters and Antiaromatic Character.

Three series of stable, neutral, π-extended bispentalene derivatives, with two pentalenes fused to a central benzene or naphthalene moiety, have been prepared through a modified double carbopalladation cascade reaction. While these chromophores feature skeletons with [4n+2] π-electron perimeters, the two 8 π-electron pentalene subunits strongly influence bonding and spectral properties. (1)H NMR spectra showed large upfield shifts of the protons in the pentalene moieties, comparable to antiaromatic monobenzopentalenes. Further investigations on magnetic ring currents through NICS-XY-scans suggest a global paratropic current and a local diatropic current at the central benzene ring in two of the series, while the third series, with a central naphthalene ring, showed more localized ring currents, with stronger paratropic ring currents on the pentalene moieties. X-ray diffraction analyses revealed planar bispentalene cores with large double- and single-bond alternation in the pentalene units, characteristic for antiaromaticity, and small alternation in the central aromatic rings. In agreement with TD-DFT calculations, both optical and electrochemical data showed much smaller HOMO-LUMO energy gaps compared to other neutral, acene-like hydrocarbons with the same number of fused rings. Both experimental and computational results suggest that the molecular properties of the presented bispentalenes are dominated by the antiaromatic pentalene-subunits despite the [4n+2] π-electron perimeter of the skeletons.