Naphthalene Diimide Research Articles

Lone‐Pair‐π Bond Strength Unveiled by a Combined Experimental and Computational Study

AbstractA series of naphthalene‐diimide (NDI) and perylene‐diimide (PDI) connected bis‐N‐heterocyclic carbene complexes of iridium(III) have been prepared and fully characterized. The analysis of their NMR spectroscopic features, together with their molecular structures show that these species display lone‐pair‐π interactions between the chloride ligands of the Ir(III) complex and the heterocycles of the NDI/PDI moieties. The detection of this type of interaction in solution is due to the formation of two atropisomers, which are formed as a result of the restricted rotation about the Ir−Ccarbene bond imposed by the (Cl)lp⋅⋅⋅π interaction. Variable‐temperature 1H NMR analysis allowed the determination of the strength of this non‐covalent interaction, which lies between ΔH=6.6 and 10 kcal/mol. The computational studies performed fully support the experimental findings.

Click generated photochromic naphthalenediimide-dithienylethene diad: Application in deciphering secret codes

Photochromic molecules with efficient fluorescence switching capability remain a core research interest among the scientific community for the application in security technologies and anti-counterfeiting measures. A dithienylethene-naphthalene diimide diad was designed and synthesized using Cu(I) catalysed click reaction between a fluorescent core substituted naphthalene diimide (cNDI) and photochromic dithienylethene (DTE) molecule, which demonstrated excellent photocyclization (ksolution = 0.0359 s−1, ksolid = 0.0122 s−1) and photocycloreversion (ksolution = 0.01737 s−1, ksolid = 0.00456 s−1) dynamics with high fluorescence quantum yield (5o ΦF = 0.39, PSS ΦF = 0.05). The fluorescence property of the molecule was switched ‘on-off’ by UV and visible light irradiation respectively via Förster resonance energy transfer (FRET) mechanism in solution state as well as in solid state, which was further corroborated with DFT studies. In view of efficient fluorescence switching behaviour and high fatigue resistance properties (25 cycles), the molecule was successfully applied in secret code encryption-decryption purposes using barcode demonstrating real-life applicability of the molecule in security technologies.

Structure-Activity Study on Substituted, Core-Extended, and Dyad Naphthalene Diimide G-Quadruplex Ligands Leading to Potent Antitrypanosomal Agents.

Several G-quadruplex nucleic acid (G4s) ligands have been developed seeking target selectivity in the past decade. Naphthalene diimide (NDI)-based compounds are particularly promising due to their biological activity and red-fluorescence emission. Previously, we demonstrated the existence of G4s in the promoter region of parasite genomes, assessing the effectiveness of NDI-derivatives against them. Here, we explored the biological activity of a small library of G4-DNA ligands, exploiting the NDI pharmacophore, against both Trypanosoma brucei and Leishmania major parasites. Biophysical and biological assays were conducted. Among the various families analyzed, core-extended NDIs exhibited the most promising results concerning the selectivity and antiparasitic effects. NDI 16 emerged as the most potent, with an IC50 of 0.011 nM against T. brucei and remarkable selectivity vs MRC-5 cells (3454-fold). Fascinating, 16 is 480-fold more potent than the standard drug pentamidine (IC50 = 5.3 nM). Cellular uptake and parasite localization were verified by exploiting core-extended NDI red-fluorescent emission.

Synthesis, Stability, Meisenheimer Complex Formation, and Charge‐Transfer Properties of Ultra‐Electron‐Deficient Tetracyano‐Naphthalene Diimides

AbstractTetra‐cyano substituted naphthalene diimides (TCNDIs) with calculated LUMO of −5.2 eV, form one of the strongest electron‐acceptors known to date. However, the synthesis and isolation of this class of molecules remain challenging due to its reactivity emanating from its ultra‐electron‐deficiency. Herein we have established an improved synthetic methodology of TCNDIs with cost‐effective reagents and circumventing metallic catalysts. The synthesis is amenable to TCNDIs with the shortest axial alkyl groups, i. e., methyl group and also longer alkyl chains. We also gained insight on how axial alkyl chain lengths influence electron‐deficiency, Meisenheimer complex formation, reactivity, and charge‐transfer of TCNDIs from computation, spectroscopy, and electrochemical studies. The TCNDIs with Me/Et axial groups were found to be more susceptible to moist solvents vis‐à‐vis the TCNDIs with longer alkyl groups. The single crystal structures of the TCNDIs show infinitely π‐stacked structure, and a new C=O ⋅ ⋅ ⋅ C≡N or C≡N ⋅ ⋅ ⋅ π motif is discerned. Finally, toluene‐mediated charge‐transfer properties of TCNDIs in the single crystals as well as in solution have been examined.

Structural descriptions of ligand interactions to RNA quadruplexes folded from the non-coding region of pseudorabies virus

To rationalise the binding of specific ligands to RNA-quadruplex we investigated several naphthalene diimide ligands that interact with the non-coding region of Pseudorabies virus (PRV). Herein we report on the x-ray structure of the naphthalene diimide ND11 with an RNA G-quadruplex putative forming sequence from rPRV. Consistent with previously observed rPRV sequence it assembles into a bimolecular RNA G-quadruplex consisting of a pair of two tetrads stacked 3ʹ to 5ʹ. We observe that ND11 interacts by binding on both the externally available 5ʹ and 3ʹ quartets. The CUC (loop 1) is structurally altered to enhance the 5ʹ mode of interaction. These loop residues are shifted significantly to generate a new ligand binding pocket whereas the terminal A14 residue is lifted away from the RNA G-quadruplex tetrad plane to be restacked above the bound ND11 ligand NDI core. CD analysis of this family of NDI ligands shows consistency in the spectra between the different ligands in the presence of the rPRV RNA G-quadruplex motif, reflecting a common folded topology and mode of ligand interaction. FRET melt assay confirms the strong stabilising properties of the tetrasubstituted NDI compounds and the contributions length of the substituted groups have on melt temperatures.

Over 60h of Stable Water-Operation for N-Type Organic Electrochemical Transistors with Fast Response and Ambipolarity.

Organic electrochemical transistors (OECTs) are of great interest in low-power bioelectronics and neuromorphic computing, as they utilize organic mixed ionic-electronic conductors (OMIECs) to transduce ionic signals into electrical signals. However, the poor environmental stability of OMIEC materials significantly restricts the practical application of OECTs. Therefore, the non-fused planar naphthalenediimide (NDI)-dialkoxybithiazole (2Tz) copolymers are fine-tuned through varying ethylene glycol (EG) side chain lengths from tri(ethylene glycol) to hexa(ethylene glycol) (namely P-XO, X=3-6) to achieve OECTs with high-stability and low threshold voltage. As a result, the NDI-2Tz copolymers exhibit ambipolarity, rapid response (<10ms), and ultra-high n-type stability. Notably, the P-6O copolymers display a threshold voltage as low as 0.27V. They can operate in n-type mode in an aqueous solution for over 60h, maintaining an on-off ratio of over 105. This work sheds light on the design of exceptional n-type/ambipolar materials for OECTs. It demonstrates the potential of incorporating these ambipolar polymers into water-operational integrated circuits for long-term biosensing systems and energy-efficient brain-inspired computing.

Enzymatic Reaction-Coupled, Cooperative Supramolecular Polymerization.

Nature employs sophisticated mechanisms to precisely regulate self-assembly and functions within biological systems, exemplified by the formation of cytoskeletal filaments. Various enzymatic reactions and auxiliary proteins couple with the self-assembly process, meticulously regulating the length and functions of resulting macromolecular structures. In this context, we present a bioinspired, reaction-coupled approach for the controlled supramolecular polymerization in synthetic systems. To achieve this, we employ an enzymatic reaction that interfaces with the adenosine triphosphate (ATP)-templated supramolecular polymerization of naphthalene diimide monomers (NSG). Notably, the enzymatic production of ATP (template) plays a pivotal role in facilitating reaction-controlled, cooperative growth of the NSG monomers. This growth process, in turn, provides positive feedback to the enzymatic production of ATP, creating an ideal reaction-coupled assembly process. The success of this approach is further evident in the living-growth characteristic observed during seeding experiments, marking this method as the pioneering instance where reaction-coupled self-assembly precisely controls the growth kinetics and structural aspects of supramolecular polymers in a predictive manner, akin to biological systems.

Boosting the performance of polymer field-effect transistors through fluorine atom substitutions and comparing the effect of various acceptor units and channel mobilities

Three conjugated copolymers, PDPP-2FTVT, PIID-2FTVT, and PNDI-2FTVT based on the 2,2′-(1E)-1,2-ethenediylbis[3-fluorothiophene] (2FTVT) core with varying acceptor units, diketopyrrolopyrrole (DPP), isoindigo (IID), and naphthalenediimide (NDI) were developed for organic field-effect transistors (OFETs). Combined electron-withdrawing fluorine atoms and vinyl linkage in the 2FTVT unit not only reduce the frontier molecular orbital energies but also extended the absorption profile and planarize the polymer backbone, manifesting synergetic effect on the strengthened molecular interactions and charge-carrier properties. The resulted copolymer, PDPP-2FTVT show highly reliable thin film transistor properties with highest hole mobility of 1.93 cm2 V−1 s−1 compared to PIID-2FTV and PNDI-2FTVT. PIID-2FTV copolymer show ambipolar characteristic with hole and electron mobilities of 0.71 and 0.03 cm2 V−1 s−1 respectively while PNDI-2FTVT exhibited the highest electron mobility of 0.20 cm2 V−1 s−1 among three copolymers. Thin film micro-structure characterization reveal that the three copolymers formed lamellar, edge-on molecular packing (for PDPP-2FTVT and PIID-2FTV), increased crystallinity with smaller π-π stacking distances, and strengthen the planarity after thermal annealing. These results contribute important progresses in solution-processed OFET and could provide a greater possibility of 2FTVT based copolymers for commercial application.

Commercializable Naphthalene Diimide Anolytes for Neutral Aqueous Organic Redox Flow Batteries

AbstractNeutral aqueous organic redox flow batteries (AORFBs) hold the potential to facilitate the transition of renewable energy sources from auxiliary to primary energy, the commercial production of anolyte materials still suffers from insufficient performance of high‐concentration and the high cost of the preparation problem. To overcome these challenges, this study provides a hydrothermal synthesis methodology and introduces the charged functional groups into hydrophobic naphthalene diimide cores, and prepares a series of high‐performance naphthalene diimide anolytes. Under the synergistic effect of π–π stacking and H‐bonding networks, the naphthalene diimide exhibits excellent structural stability and the highest water solubility (1.85 M for dex‐NDI) reported to date. By employing the hydrothermal method, low‐cost naphthalene diimides are successfully synthesized on a hundred‐gram scale of $0.16 g−1 ($2.43 Ah−1), which is also the lowest price reported to date. The constructed full battery achieves a high electron concentration of 2.4 M, a high capacity of 54.4 Ah L−1, and a power density of 318 mW cm−2 with no significant capacity decay observed during long‐duration cycling. These findings provide crucial support for the commercialization of AORFBs and pave the way for revolutionary developments in neutral AORFBs.

Commercializable Naphthalene Diimide Anolytes for Neutral Aqueous Organic Redox Flow Batteries.

Neutral aqueous organic redox flow batteries (AORFBs) hold the potential to facilitate the transition of renewable energy sources from auxiliary to primary energy, the commercial production of anolyte materials still suffers from insufficient performance of high-concentration and the high cost of the preparation problem. To overcome these challenges, this study provides a hydrothermal synthesis methodology and introduces the charged functional groups into hydrophobic naphthalene diimide cores, and prepares a series of high-performance naphthalene diimide anolytes. Under the synergistic effect of π-π stacking and H-bonding networks, the naphthalene diimide exhibits excellent structural stability and the highest water solubility (1.85 M for dex-NDI) reported to date. By employing the hydrothermal method, low-cost naphthalene diimides are successfully synthesized on a hundred-gram scale of $0.16 g-1 ($2.43 Ah-1), which is also the lowest price reported to date. The constructed full battery achieves a high electron concentration of 2.4 M, a high capacity of 54.4 Ah L-1, and a power density of 318 mW cm-2 with no significant capacity decay observed during long-duration cycling. These findings provide crucial support for the commercialization of AORFBs and pave the way for revolutionary developments in neutral AORFBs.

Auxiliary ligand influence on interpenetration and C2H2/CO2 separation in NDI based isoreticular MOFs

Selective separation of C2H2 from CO2 mixtures promises a critical industrial process to produce high-purity C2H2 but challenging due to their similar physical properties and molecular sizes/shapes. Naphthalenediimide (NDI) ligand-based metal − organic frameworks (MOFs) exhibit potential in selective adsorption of C2H2 due to NDI’s high affinity to C2H2 molecules. Here, three iso-reticular NDI based MOFs (denoted as FJU-109, 110 and 111) are obtained by tuning interpenetration using auxiliary ligands of different lengths. Based on the actual column breakthrough experiments, FJU-111 can achieve separation C2H2/CO2 mixture, with a separation selective of 2.2. Calculation of the binding energy shows that C-H…O interactions between guest and O atom from NDI ligand play a dominant role in elective recognition of acetylene.

A new water−soluble naphthalene diimide as a highly selective fluorescent chemosensor for Cu(II) ion: Synthesis, DFT calculations, photophysical and electrochemical properties

The highly selective, sensitive, and water-soluble fluorescent sensors are desideratum for optoelectronic, environmental, biological, and biomedical applications. An innovative fluorescence chemosensor, naphthalene diimide (3) with metal binding sites, was designed, synthesized and characterized. The chemosensor's optical, electrochemical, spectroelectrochemical, and morphological properties were investigated, and then the density functional theory (DFT) simulations were conducted. The selectivity of 3 for the metals Cu(II), Ag(I), Hg(II), Mg(II), Fe(III), Ca(II), Co(II), Zn(II), Pb(II) and Cd(II) were investigated through UV–visible and fluorescence spectroscopy techniques. 3 was highly selective and sensitive toward Cu(II) metal ions. The chemosensor can detect Cu(II) in water with a detection limit of 1.11 μM, which is lower than the WHO standard and has good repeatability. Further investigations through the IR, DPV, AFM, UV–visible and fluorescence spectroscopies, SEM, EDX and TEM techniques confirmed the binding capabilities of the 3 with Cu(II).

The role of fused thiophene and naphthalene diimide (NDI) in shaping the optical and electrical properties of donor-acceptor polymers

Three polymers with general structure (D-A)n were designed and synthetized to investigate the interaction of strong donors and strong acceptors in polymer chain. They are based on different fused thiophenes (1Th: 4,4′-bis(2-ethylhexyl)-cyclopenta [2,1-b:3,4-b’]dithiophene; 2Th: 4,8-bis [(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b']dithiophene; 3Th: 4,8-bis(4-fluoro-5-(2-ethylhexyl)-thiophen-2-yl)benzo [1,2-b:4,5-b']bisthiophene) and N,N′-bis(2-ethylhexyl)-1,8:4,5-naphthalenetetracarboxdiimide (NDI). Fused benzo- and cyclopenta-thiophene derivatives were selected because they are known for their strong electron-donating properties. NDI was coupled with them in polymer chain because it is one of the best known electron withdrawing units. Such combination of donor and acceptor units is one of the strategies for obtaining low band gap conjugated polymers with semiconducting properties for many applications. The interaction of donors and acceptors is a key factor determining the properties of such polymers. The electrochemical and spectroscopic measurement were supported by DFT calculations. Moreover, organic field effect transistors (OFET) were fabricated to demonstrate the feasibility of using the newly developed materials in electronic devices.

A Halogen Bonding [2]Rotaxane Shuttle for Chloride-Selective Optical Sensing.

The first example of a [2]rotaxane shuttle capable of selective optical sensing of chloride anions over other halides is reported. The rotaxane was synthesised via a chloride ion template-directed cyclisation of an isophthalamide macrocycle around a multi-station axle containing peripheral naphthalene diimide (NDI) stations and a halogen bonding (XB) bis(iodotriazole) based station. Proton NMR studies indicate the macrocycle resides preferentially at the NDI stations in the free rotaxane, where it is stabilised by aromatic donor-acceptor charge transfer interactions between the axle NDI and macrocycle hydroquinone moieties. Addition of chloride ions in an aqueous-acetone solvent mixture induces macrocycle translocation to the XB anion binding station to facilitate the formation of convergent XB⋅⋅⋅Cl- and hydrogen bonding HB⋅⋅⋅Cl- interactions, which is accompanied by a reduction of the charge-transfer absorption band. Importantly, little to no optical response was induced by addition of bromide or iodide to the rotaxane, indicative of the size discriminative steric inaccessibility of the interlocked cavity to the larger halides, demonstrating the potential of using the mechanical bond effect as a potent strategy and tool in chloride-selective chemo-sensing applications in aqueous containing solvent environments.

Naphthalene diimide–Annulated Heterocyclic Acenes: Synthesis, Electrochemical and Semiconductor Properties and Their Multifaceted Applications

Naphthalene diimide–Annulated Heterocyclic Acenes: Synthesis, Electrochemical and Semiconductor Properties and Their Multifaceted Applications

Stabilization of a Photoradiated Naphthalene Diimide-Based Organic Radical Anion Inside a Peptide-Based Gel Matrix with an Improvement of Optoelectronic Properties.

An amino acid-conjugated naphthalene diimide (NDI)-based highly red fluorescent radical anion has been found in a water medium under the photoradiated condition. This molecule has failed to form the radical anion in the monomeric state; however, the J aggregation in the aqueous medium has ensured the formation of radical anion in the ambient condition after the irradiation of both sunlight and UV light exposure. Electron paramagnetic resonance (EPR) studies clearly suggest the formation of radical anions. Herein, the stability of the radical anion in the aqueous medium is only a few minutes as a small amount of shaking is enough to quench the radical anion in the solution state. Furthermore, the incorporation of this molecule into a peptide-based hydrogel matrix and the consequent photoirradiation have not only helped to develop radical anion in the gel matrix but also increased the enormous stability of the radical anion inside the hydrogel matrix even for 30 days. It is envisaged that the formation of the radical anion within the gel matrix prevents the free movement of the NDI molecules and restricts the diffusion of molecular oxygen in the system, which leads to the stability of the radical anions in the gel. Moreover, the stability of the radical anion within the gel has helped to enhance the conductivity of the hybrid gel to a great extent. Interestingly, the radical anion-containing hybrid hydrogel has shown a potential photoswitching property.

Synthesis of cNDI‐Peptide‐Dimer as a G4 Cluster‐Selective Binder and its Interaction with G4 Dimer

AbstractThe amino acid unit carrying cyclic naphthalene diimide (cNDI) was synthesized by linking the amino moiety of cNDI as a G4‐specific ligand with the γ‐carboxylic acid moiety of Fmoc‐Glu. cNDI‐peptide‐dimer, 1 was synthesized by peptide synthesizer using this unit. 1 exhibited an extremely strong binding constant of the order of 108 M−1 with telomeric G4 dimer, probably due to cooperative stacking of the its two G4 planes. It also showed an IC50 at the nM level by the TRAP assay. The results obtained here are expected to enable the design of peptide ligands with multiple cNDI sites targeting the G4 cluster by using the amino acid units of cNDI.

Diffusional Electron Transport Coupled to Thermodynamically Driven Electron Transfers in Redox-Conductive Multivariate Metal-Organic Frameworks.

The development of redox-conductive metal-organic frameworks (MOFs) and the fundamental understanding of charge propagation through these materials are central to their applications in energy storage, electronics, and catalysis. To answer some unresolved questions about diffusional electron hopping transport and redox conductivity, mixed-linker MOFs were constructed from two statistically distributed redox-active linkers, pyromellitic diimide bis-pyrazolate (PMDI) and naphthalene diimide bis-pyrazolate (NDI), and grown as crystalline thin films on conductive fluorine-doped tin oxide (FTO). Owing to the distinct redox properties of the linkers, four well-separated and reversible redox events are resolved by cyclic voltammetry, and the mixed-linker MOFs can exist in five discrete redox states. Each state is characterized by a unique spectroscopic signature, and the interconversions between the states can be followed spectroscopically under operando conditions. With the help of pulsed step-potential spectrochronoamperometry, two modes of electron propagation through the mixed-linker MOF are identified: diffusional electron hopping transport between linkers of the same type and a second channel that arises from thermodynamically driven electron transfers between linkers of different types. Corresponding to the four redox events of the mixed-linker MOFs, four distinct bell-shaped redox conductivity profiles are observed at a steady state. The magnitude of the maximum redox conductivity is evidenced to be dependent on the distance between redox hopping sites, analogous to the situation for apparent electron diffusion coefficients, Deapp, that are obtained in transient experiments. The design of mixed-linker redox-conductive MOFs and detailed studies of their charge transport properties present new opportunities for future applications of MOFs, in particular, within electrocatalysis.

Aggregation-Induced Emission of Naphthalene Diimides: Effect of Chain Length on Liquid and Solid-Phase Emissive Properties.

The aggregation-induced emission (AIE) properties of a systematic series of naphthalene diimides (NDIs) varying the chain length at the imide positions have been studied. A solvophobic collapse of NDI units through the flash injection of THF NDI solutions in sonicating water triggers the formation of stable suspensions with enhanced fluorescence emissions. Shorter chains favor the π-π stacking of NDI units through H-aggregation producing a strong AIE effect showing remarkably high quantum yields that have not been observed for non core-substitued NDIs previously. On the other hand, NDIs functionalized with longer chains lead to more disordered domains where π-π stacking between NDI units is mainly given by J-aggregation unfavoring the AIE effect.

Naphthalene diimide-Annulated Heterocyclic Acenes: Synthesis, Electrochemical and Semiconductor Properties and their Multifaceted Applications.

Acenes and Naphthalene Diimides (NDIs) stand as distinguished classes of organic compounds, each possessing unique and intriguing properties that have garnered significant attention across various scientific disciplines. Acenes, characterized by linearly fused aromatic rings, have captivated researchers due to their diverse electronic structures and promising applications in materials science. On the other hand, NDIs, known for their distinctive electron-accepting properties, exhibit remarkable versatility in fields ranging from organic electronics, supramolecular to spin chemistry. In this review, we navigate through the fascinating realms of both acenes and NDIs before converging our focus on the highly diverse and distinctive subgroup of NDI-annulated heterocyclic acenes. This potentially important subgroup, has emerged as a subject of intense investigation, encapsulating their fascinating synthesis, optical and electrochemical characteristics, and multifaceted applications that span the realms of chemistry, physics, and biology. Through the exploration of their synthetic strategies, unique properties, and diverse applications, this review aims to offer a comprehensive understanding of the pivotal role played by NDI-based heterocyclic acenes in contemporary multidisciplinary research and technological innovation.