NDI Units Research Articles

Intrinsically microporous polyimide membranes with synergistic aromatic and alicyclic linking groups for efficient molecular separation

Polymers of intrinsic microporosity (PIMs) are widely recognized for having great potential in reforming membrane technology for molecular separation within organic solvents, due to their rich and appropriate pore structures with a size < 2 nm. However, the swelling in organic solvents has a significant effect on their pore structures due to the amorphous and linear nature, resulting in the permeability and selectivity performances of developed PIM membranes being far from ideal. In this work, we synthesized an advanced polyimide of intrinsic microporosity by integrating a Tröger’s base (TB) structure with an synergistic structure of aromatic (naphthalenediimide, NDI) and alicyclic (bicyclooctenediimide, BCODI) linking groups. The TB with a rigid and twisted structure was used to furnish a basis for inhibiting chain packing for high overall free volume. The ultra-rigid NDI units maintained such a tailored high free volume and provided superior solvent resistance. The relatively flexible and polar BCODI units promoted local chain mobility to tailor uniform pore size distribution and increased affinity for polar solvents. The innovative design fostered the formation of stable, uniform, and highly solvent-accessible intrinsic micropores. The prepared TFC membrane exhibited good organic solvent separation capabilities, achieving an ethanol permeance of 7.6 L m-2 h−1 bar−1 and a low molecular weight cut-off (MWCO) of approximately 470 Da. This work contributes significantly to the strategic design of PIMs for preparing high-performance membranes for realistic chemical-related separation application scenarios.

Mixed Ionic-Electronic Conduction Increases the Rate Capability of Polynaphthalenediimide for Energy Storage.

Conjugated polymers offer a number of unique and useful properties for use as battery electrodes, and recent work has reported that conjugated polymers can exhibit excellent rate performance due to electron transport along the polymer backbone. However, the rate performance depends on both ion and electron conduction, and strategies for increasing the intrinsic ionic conductivities of conjugated polymer electrodes are lacking. Here, we investigate a series of conjugated polynapthalene dicarboximide (PNDI) polymers containing oligo(ethylene glycol) (EG) side chains that enhance ion transport. We produced PNDI polymers with varying contents of alkylated and glycolated side chains and investigated the impact on rate performance, specific capacity, cycling stability, and electrochemical properties through a series of charge-discharge, electrochemical impedance spectroscopy, and cyclic voltammetry measurements. We find that the incorporation of glycolated side chains results in electrode materials with exceptional rate performance (up to 500C, 14.4 s per cycle) in thick (up to 20 μm), high-polymer-content (up to 80 wt %) electrodes. Incorporation of EG side chains enhances both ionic and electronic conductivities, and we found that PNDI polymers with at least 90% of NDI units containing EG side chains functioned as carbon-free polymer electrodes. This work demonstrates that polymers with mixed ionic and electronic conduction are excellent candidates for battery electrodes with good cycling stability and capable of ultra-fast rate performance.

Alignment of linear polymeric grains for highly stable N-type thin-film transistors

Summary Temperature-insensitive properties are attractive for most electronics, including polymeric semiconducting devices. Especially, polymeric field-effect transistors (FETs) with high mobility have been important research targets due to their broad applications. However, polymeric FETs with stable charge transport operating at extremely cold or hot zones are faced with enormous challenges. In this study, the polyacrylonitrile was found to significantly tune the sizes of pre-aggregates of polymers in solutions and the crystallinity of the polymeric films. The orientation of 5–25 μm linear grains in the films were prepared through the bar-coating process with polyacrylonitrile as an additive, which stabilized the electron mobility over a wide range of temperatures. The linear-grain morphology of the film contributed to reducing the holes and grain boundaries in the transport paths of carriers. Typically, the top-gate FETs based on P(NDI2OD-T2) displayed a stable electron transporting behavior from 200 to 460 K, with mobility greater than 3.5 cm2V−1s−1.

A bistable [2]catenane switched by hetero-radical pairing interactions.

A bistable [2]catenane composed of a tetracationic cyclophane, namely cyclobis(paraquat-p-phenylene) (CBPQT4+) that is mechanically interlocked by a neutral macrocylic component containing both a 1,5-dioxynaphthalene (DNP) and a naphthalene-1,4,5,8-bis(dicarboximide) (NDI) unit, was obtained by using template-directed synthesis via click chemistry. In the fully oxidized state, the CBPQT4+ component encircles the DNP unit, driven by donor-acceptor interactions. Upon reduction of both the CBPQT4+ ring and the NDI unit, the CBPQT2(˙+) ring undergoes shuttling and resides on the NDI˙- station, driven by coulombic-enhanced spin-pairing interactions between different aromatic radicals.

Periodic mesoporous organosilicas containing naphthalenediimides within the pore walls for asphaltene adsorption

Abstract Periodic mesoporous organosilicas (PMO) containing 1,4,5,8-naphthalenediimides (NDI) as integral part of the pore walls were employed for the adsorption of asphaltenes from toluene solutions. The adsorbents, which were named PMONDI, contained variable amounts of NDI co-condensed with inorganic silica. The PMONDI showed a better performance for asphaltene adsorption than purely inorganic mesoporous silica SBA-15, which was used for comparison. Adsorption isotherms of the PMONDI showed asphaltene adsorption capacities reaching up to 224 mg/g, which is higher than most reported adsorbents. The best fit for the adsorption isotherms was achieved with the Langmuir model (developed for homogeneous surfaces) for SBA-15 and with the Sips model (which deals with heterogeneous surfaces) for the PMONDI. It was concluded that the homogeneous surface in SBA-15, where asphaltene binding is mainly due to hydrogen bonding to silanol groups, was converted to heterogeneous surfaces in the presence of the NDI, indicating that hydrophobic and π-stacking interactions between wall-embedded NDI units and asphaltene molecules contributed for binding. These conclusions were supported by contact angle measurements. The adsorbents could be reused for at least three adsorption cycles, and the adsorbed asphaltenes could be easily regenerated by desorption with organic solvents. In conclusion, the PMONDI are novel materials with great potential for applications such as oil upgrading and the remediation of oil spills.

Fine‐Tuning Aromatic Stacking and Single‐Crystal Photoluminescence Through Coordination Chemistry

Organic aromatics usually show a decrease in fluorescence efficiency in the solid state on account of well‐known aggregation induced quenching. We have found that single crystals of coordination polymers consisting of γ‐aminobutyric acid functionalized naphthalenediimide ligand (H2GABA‐NDI) can give rise to highly emissive, broad, and red‐shifted photoluminescence (PL) in the solid state. To better understand the origin of the bandwidth broadening with the π–π stacking distances, we performed time‐resolved PL studies in a series of polymers with a variety of metal centers. We conclude that the broad steady‐state PL signals is originated from a superposition of two emissive states with differing energy and lifetimes, with the lower energy one produced by the interchromophoric interactions mediated by π–π stacking of neighboring NDI units. Our work demonstrates that coordination chemistry is an effective tool to modulate interchromophoric couplings and that simple PL analysis can be used as a measure of the degree of π‐stacking.

Pain pattern classification and directional preference for patients with neck pain

Objectives:Pain Pattern Classification (PPC) and Directional Preference (DP) have been shown to be predictive of health care outcomes and serve to guide orthopedic clinical decision making. We conducted a prospective, observational cohort study to verify the association between PPC, DP, and clinical outcomes.Methods:Clinical outcome measures including pain intensity and disability were completed at first examination and follow-up by 335 patients. A Pearson’s chi-squared test was used to determine differences in prevalence rates for the categorical variables, and two-sample t-tests were used to determine differences in rates for the continuous variables. A Tukey’s range test was used to determine differences in follow-up pain intensity and disability for neck pain dual-classification schemes.Results:The prevalence of DP was 82.4%. The prevalence of CEN, Non-CEN, and Non-Classifiable (NC) was 15.2%, 42.1%, and 25.1%, respectively. The prevalence of DP was lowest for patients with sub-acute symptoms and who were <45 years old. Patients classified as DP CEN had, on average 2.62 NDI units less than patients classified as Non-DP. Patients classified as DP CEN had, on average, 0.90 pain intensity units less than patients classified as Non-DP at follow-up. Patients who demonstrated DP CEN did not have clinically significant lower pain intensity or disability at follow-up than patients who demonstrated Non-DP.Discussion:The results of this investigation need to be interpreted with caution with respect to the study design and it’s subsequent strengths and limitations.Level of Evidence:1b.

Persistent radical anion polymers based on naphthalenediimide and a vinylene spacer.

Persistent n-doped conjugated polymers were achieved by doping the electron accepting PDNDIV and PFNDIV polymers with ionic (TBACN) or neutral (TDAE) dopants. The great electron affinities, as indicated by the low LUMO levels of PDNDIV (−4.09 eV) and PFNDIV (−4.27 eV), facilitated the chemical reduction from either TBACN or TDAE. The low-lying LUMOs of the neutral polymers PDNDIV and PFNDIV were achieved by incorporation of vinylene spacers between the electron poor NDI units to increase the conjugation length without the use of an electron donor, and this was lowered further by an electron-withdrawing fluorinated N-substituent on the NDI moiety. The polymer radical anions were found to persist for several days under ambient conditions by EPR spectroscopy. A distinguishing and noteworthy feature of these polymers is that they can be consecutively reduced by up to four electrons in acetonitrile. Conductivity measurements demonstrate the prospective impact of PDNDIV and PFNDIV for organic electronics.

Electron Hopping and Charge Separation within a Naphthalene-1,4:5,8-bis(dicarboximide) Chiral Covalent Organic Cage.

We present the stereoselective synthesis of a chiral covalent organic cage consisting of three redox-active naphthalene-1,4:5,8-bis(dicarboximide) (NDI) units by dynamic imine chemistry. Single crystal X-ray diffraction analysis shows that host-guest interactions and racemic cocrystallization allow for controlling the solid state structure. Electronic interactions between the NDI units probed by absorption and circular dichroism spectroscopies, electrochemistry and theoretical calculations are shown to be weak. Photoexcitation of NDI leads to intracage charge separation with a longer lifetime than observed in the corresponding monomeric NDI and dimeric NDI cyclophane imines. The EPR spectrum of the singly reduced cage shows that the electron is localized on a single NDI unit at ambient temperatures and transitions to rapid hopping among all three NDI units upon heating to 350 K. Dynamic covalent chemistry thus promises rapid access to covalent organic cages with well-defined architectures to study charge accumulation and electron transport phenomena.

Even and odd oligothiophene-bridged bis-naphthalimides for n-type and ambipolar organic field effect transistors

Which effect directs supramolecular packing? π–π stabilizing interactions between two NDI units or dipole–dipole couplings?

Switching of the triplet excited state of rhodamine/naphthaleneimide dyads: an experimental and theoretical study.

Rhodamine-bromonaphthaleneimide (RB-NI) and rhodamine-bromonaphthalenediimide (RB-NDI) dyads were prepared for switching of the triplet excited states. Bromo-NI or bromo-NDI parts in the dyads are the spin converters, i.e., the triplet state producing modules, whereas the RB unit is the acid-activatable electron donor/energy acceptor. NI and NDI absorb at 359 and 541 nm, and the T1 state energy levels are 2.25 and 1.64 eV, respectively. RB undertakes the reversible spirolactam (RB-c) ↔ opened amide (RB-o) transformation. RB-c shows no visible light absorption, and the triplet-state energy level is ET1 = 3.36 eV. Conversely RB-o shows strong absorption at 557 nm, and ET1 is 1.73 eV. Thus, the acid-activated fluorescence-resonance-energy-transfer (FRET) competes with the ISC of NI or NDI. No triplet state was observed for the dyads with nanosecond time-resolved transient absorption spectroscopy. Upon addition of acid, strong fluorescence and long-living triplet excited states were observed. Thus, the producing of triplet state is acid-activatable. The triplet state of RB-NI is localized on RB-o part, whereas in RB-NDI the triplet state is delocalized on both the NDI and RB-o units. The ISC of spin converter was not outcompeted by RET. These studies are useful for switching of triplet excited state.

A π-conjugated hydrogel based on an Fmoc-dipeptide naphthalene diimide semiconductor

The beta-sheet self-assembly of an n-type NDI-dipeptide into a transparent, self-supporting hydrogel at low concentrations is described. The nanostructure of the gel is stabilized by the intermolecular pi-pi association of the NDI units and pi-pi interdigitation of the fluorene groups.

Structural Characterization of a Rigidified Threading Bisintercalator

NMR spectroscopy was used to explore the sequence-specific interaction of DNA with a new threading bisintercalator (C1) consisting of two intercalating 1,4,5,8-naphthalenetetracarboxylic diimide (NDI) units connected by a rigid, tricyclic spiro linker. A structural model of C1 complexed to d(CGGTACCG)(2) was calculated using distance constraints obtained from solution NMR data. The model was also supported by the results from residual dipolar coupling (RDC) measurements obtained using Pf1-phage as a cosolvent. According to the model, the central cyclohexane ring of the linker connecting the two NDI units lies flat in the minor groove of DNA. Linker length, hydrogen bonding, steric, and hydrophobic factors all appear to contribute to the observed sequence specificity of binding. These results serve to illustrate the versatility of threading polyintercalation given that, in a previous study, a ligand consisiting of two NDI units joined by a flexible peptide linker was shown to bind sequence specifically within the major groove of this same sequence of DNA.

Tunable Columnar Mesophases Utilizing C2 Symmetric Aromatic Donor−Acceptor Complexes

Derivatives of relatively electron rich 1,5-dialkoxynaphthalene (Dan) donors and relatively electron deficient 1,4,5,8-naphthalenetetracarboxylic diimide (Ndi) acceptors have been exploited in the folding and self-assembly of a variety of complex molecular systems in solution. Here, we report the use of Dan and Ndi derivatives to direct assembly of extended columns with alternating face-centered stacked structure in the solid state. A variety of 1:1 Dan:Ndi mixtures produced mesophases that were found to be stable over temperature ranges extending up to 110 degrees C. Analysis of these mesophases indicates mixtures with soft/plastic crystal phases and a few mixtures with the thermodynamic properties of true liquid crystals, all composed of alternating donor-acceptor columns within. Importantly, a correspondence was found between the clearing and crystallization points of the mesophase mixtures and the melting/clearing points of the component Ndi and Dan units, respectively. This correspondence enables the predictable tuning of mesophase phase transition temperatures. The study of sterically hindered derivatives led to a set of mixtures in which a dramatic and sudden color change (deep red to yellow) was observed upon crystallization of the mesophase due to a phase separation of the component donor and acceptor units.

Altering the Folding Patterns of Naphthyl Trimers

Proteins can adopt helical and sheet-type secondary structures that depend on their primary sequence of amino acids. Nonnatural foldamers have been developed to emulate these protein structures as well as investigate various types of noncovalent interactions. Here we report a strategy to access two distinct folding topologies in aqueous solutions using the inherent recognition properties of aromatic donor/acceptor interactions. These oligomers are constructed of electron-rich 1,5-dialkoxynaphthalene (Dan) and electron-deficient 1,4,5,8-naphthalenetetracarboxylic diimide (Ndi) units. A trimer of the sequence Dan-Ndi-Dan was shown to adopt a pleated fold in solution, while its constitutional isomer, Dan-Dan-Ndi, adopted an intercalative or turn-type fold. UV-vis and NOESY spectroscopy analyses were consistent with the two different conformations. This study illustrates the designability of folding naphthyl oligomers and encourages the use of directed aromatic interactions to construct larger and more complex assemblies in water.

Aromatic oligomers that form hetero duplexes in aqueous solution.

The electron-deficient 1,4,5,8-naphthalenetetracarboxylic diimide (Ndi) and electron-rich 1,5-dialkoxynaphthalene (Dan) have been shown to complex strongly with each other in water due to the hydrophobic effect as modulated through the electrostatic complementarity of the stacked dimer. Previously, oligomers of alternating Ndi and Dan units, termed aedamers, were the first foldamers to employ intramolecular aromatic stacking to effect the formation of secondary structure of nonnatural chains in aqueous solution. Described here is the use of this aromatic-aromatic (or pi-pi) interaction, this time in an intermolecular format, to demonstrate the self-assembly of stable hetero duplexes from a set of molecular strands (1a-4a) and (1b-4b) incorporating Ndi and Dan units, respectively. A 1-to-1 binding stoichiometry was determined from NMR and isothermal titration calorimetry (ITC) investigations, and these experiments indicated that association is enthalpically favored with the tetra-Ndi (4a) and tetra-Dan (4b) strands forming hetero duplexes (4a:4b) with a stability constant of 350 000 M-1 at T = 318 K. Polyacrylamide gel electrophoresis (PAGE) also illustrated the strong interaction between 4a and 4b and support a 1-to-1 binding mode even when one component is in slight excess. Overall, this system is the first to utilize complementary aromatic units to drive discrete self-assembly in aqueous solution. This new approach for designing assemblies is encouraging for future development of duplex systems with highly programmable modes of binding in solution or on surfaces.

Changing DNA grooves--a 1,4,5,8-naphthalene tetracarboxylic diimide bis-intercalator with the linker (beta-Ala)(3)-Lys in the minor groove.

We have been investigating a modular, threading DNA polyintercalator design based upon the 1,4,5,8-naphthalene tetracarboxylic diimide (NDI) intercalating unit. Previously, we have reported the NMR analysis of a bis-intercalator-DNA complex in which the peptide linker between NDI units was found to occupy the DNA major groove (Guelev, Lee, Sorey, Hoffman, Iverson, Chem. Biol. 2001, 8, 415-425). Here we describe the NMR analysis of a complex between a related bis-intercalator known to display altered DNA sequence specificity. In this case, the linker resides in the DNA minor groove. We have thus shown that within this set of sequence specific bis-intercalators, both DNA grooves can be accessed, setting the stage for longer threading polyintercalators designed to have linkers occupying both grooves in an alternating fashion.

An octakis-intercalating molecule

Herein we report the synthesis and characterization of a polyintercalator with eight potential intercalating l,4,5,8-naphthalenetetracarboxylic diimide (NDI) units linked in a head-to-tail arrangement via a peptide linker. UV spectroscopy and viscometry measurements indicated the molecule binds to double-stranded DNA with all eight NDI units intercalated simultaneously. Competition dialysis and DNAse 1 footprinting studies revealed a preference for GC-rich regions of DNA, and circular dichroism studies revealed significant distortion of B-form DNA upon binding. Our so-called ‘octamer’ represents, to the best of our knowledge, the first intercalator that binds as an octakis-intercalator, capable of spanning at least 16 base pairs of DNA.