Naphthalene Diimide Moieties Research Articles

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.

Tuning the Catalytic Activity of a Pincer Complex of Rhodium(I) by Supramolecular and Redox Stimuli.

We report the rhodium(I) complex [Rh(CNC-NDI)(CO)]+ , in which CNC-NDI refers to a pincer-CNC ligand decorated with a naphthalenediimide moiety. Due to the presence of the planar CNC ligand and the naphthalenediimide moiety, the electronic nature of the complex can be modulated by means of supramolecular and redox stimuli, respectively. The metal complex shows a strong π-π-stacking interaction with coronene. This interaction has an impact on the electron-richness of the metal, as demonstrated by the shifting of the ν(CO) stretching band to a lower frequency. The addition of tetrabutylammonium fluoride facilitates the sequential one- and two-electron reduction of the NDI moiety of the ligand, thus resulting in a situation in which the ligand can increase its electron-donor strength in two levels. The nature of the interaction with the fluoride anion was studied computationally. The catalytic activity of the [Rh(CNC-NDI)(CO)]+ complex was tested in the cycloisomerization of alkynoic acids, where it is observed that the activity of the catalyst can be modulated between four levels of activity, which correspond to i) the use of the unmodified catalyst, ii) catalyst+coronene, iii) catalyst+2 equivalents of fluoride, and iv) catalyst+5 equivalents of fluoride.

Tuning the Catalytic Activity of a Pincer Complex of Rhodium(I) by Supramolecular and Redox Stimuli

AbstractWe report the rhodium(I) complex [Rh(CNC−NDI)(CO)]+, in which CNC−NDI refers to a pincer‐CNC ligand decorated with a naphthalenediimide moiety. Due to the presence of the planar CNC ligand and the naphthalenediimide moiety, the electronic nature of the complex can be modulated by means of supramolecular and redox stimuli, respectively. The metal complex shows a strong π–π‐stacking interaction with coronene. This interaction has an impact on the electron‐richness of the metal, as demonstrated by the shifting of the ν(CO) stretching band to a lower frequency. The addition of tetrabutylammonium fluoride facilitates the sequential one‐ and two‐electron reduction of the NDI moiety of the ligand, thus resulting in a situation in which the ligand can increase its electron‐donor strength in two levels. The nature of the interaction with the fluoride anion was studied computationally. The catalytic activity of the [Rh(CNC−NDI)(CO)]+ complex was tested in the cycloisomerization of alkynoic acids, where it is observed that the activity of the catalyst can be modulated between four levels of activity, which correspond to i) the use of the unmodified catalyst, ii) catalyst+coronene, iii) catalyst+2 equivalents of fluoride, and iv) catalyst+5 equivalents of fluoride.

Thermosalient effect of a naphthalene diimide and tetrachlorocobaltate hybrid and changes of color and magnetic properties by ammonia vapor.

An organic-inorganic hybrid metal halide (OIMH), namely the electron-deficient naphthalene diimide (NDI) and [CoCl4]2- hybrid (1), showed potential as a sensor for ammonia and amines, in addition to magnetic changes upon vapochromism. Crystal 1 exhibited thermosalient behavior such as leaping and movement, at around 130 °C, which could be explained to be associated with the removal of water molecules from the crystal lattice as shown by TGA and DSC. Compound 1 changed from green to black within 5 minutes when exposed to ammonia vapor, which was attributed to the radical formation in the NDI moiety as evidenced by ESR, and this phenomenon was preserved even when other mono- and di-alkylamines were applied. The exposure of 1 to ammonia resulted in a subsequent color alteration, progressing from black to a gradually dark orange after one day (1_NH3_1 day). This transformation was concomitant with the formation of [Co(NH3)6]3+ from [CoCl4]2-, leading to a modification of the magnetic properties from paramagnetic Co(II) (S = 3/2) to diamagnetic Co(III) (S = 0). Based on these findings, compound 1 represents the first example of an OIMH that exhibits thermosalient behaviour, color change, and magnetic conversion upon exposure to ammonia.

Solvent-Modulated Self-Assembly of Naphthalenediimide-Based Cd(II) Complexes and the Controllable Photochromism via Conformational Isomerization.

Rational regulation of the properties of photochromic materials is a challenging and meaningful work. In the present work, NDI-based complexes, namely, [Cd0.5(NDI)(HBDC)]·H2O (1) and a series of conformational isomers of {[Cd(NDI)0.5(BDC)]·MeCN}n (2), were synthesized by varying the solvent conditions (H2BDC = terephthalic acid, NDI = N,N'-bis(3-pyridylcarbonylhydrazine)-1,4,5,8-naphthalene diimide). Complex 1 exhibits a 0D mononuclear structure without photochromic behavior due to the bad conjugation of the naphthalene diimide moiety. The conformational isomers of complex 2 manifest a 3D network, showing ultra-fast photo-induced intermolecular electron transfer photochromic behavior under X-ray, UV, and visible light. However, they show different photochromic rates and coloring contrast upon photoirradiation, which originates from their difference in the distances of lone pair(COO)···π(NDI). This was realized via controlling the solvent ratio in the reaction system. In addition, compared to UV/X-ray light, 2 exhibits greater sensitivity to visible light and is an organic-inorganic hybrid material with photomodulated luminescence. Based on the excellent performance, complex 2 can be applied to filter paper, showing potential applications as an inkless printing medium and selective perception of ammonia and amine vapors in the solid state via different visual color changes.

Mixed ionic–electronic conductance across naphthalenediimide-functionalized biopolymers

A proton conducting protein-based biopolymer is modified with naphthalenediimide (NDI) monomers to specific amino acids resulting in an oriented organization of the NDI moieties exhibiting electronic conductivity of 40 mS cm−1 upon reduction.

Reversible photochromism and photoresponsive luminescence in naphthalene diimide-based framework with Lindqvist-type polyoxometalate template

Metal-organic frameworks that contain photoactive organic ligands or photoactive inorganic components are an emerging class of multifunctional hybrid materials that in recent years has gradually become an ideal platform for building photochromic complexes. In this paper, a metal-organic framework based on naphthalene diimide (NDI) ligand with Lindqvist-type W6O192– polyanions, [Ce2(BINDI) (DMF)8]·[W6O19] (1), (H4BINDI = N, N'-bis(5-isophthalic acid)-1,4,5,8-naphthalene diimide) was synthesized and systematically characterized. It displays a cationic two-dimensional grid coordination network, featuring anion–π interactions between W6O192– and expanded π–electron deficient naphthalene diimide (NDI) moieties. Moreover, because of the presence of electron-deficient NDI moieties and photoactive W6O192–, this complex exhibits fast responsive reversible photochromism and photoresponsive tunable luminescence. UV–Vis, IR, PXRD, EPR, and XPS spectral studies indicate that the obviously photochromic phenomenon of complex 1 is derived from photoinduced electron-transfer form NDI radicals and W5+ species.

Immobilization of Ethynyl-π-Extended Electron Acceptors with Amino-Terminated SAMs by Catalyst-Free Click Reaction.

Surface modification of SiO2 using a catalyst-free quantitative reaction between an amine and an ethynyl-π-extended naphthalenediimide was investigated. A post-reaction method, in which the catalyst-free reaction was performed at the surface after the formation of amino-terminated self-assembled monolayers (SAMs), resulted in dense, uniform modification of the SiO2 surface with the naphthalenediimide molecules. Both X-ray reflectivity and angle-resolved X-ray photoemission spectroscopy showed consistent results for the layer thickness and density. In contrast, a pre-reaction method, in which an amino-silane and the ethynyl-π-extended naphthalenediimide reacted first and then formed a SAM, afforded a sparse SAM on the SiO2 surface, probably due to the steric hindrance of the naphthalenediimide moieties. The in situ decoration of the SiO2 surface by a catalyst-free quantitative reaction offers a facile route for modifying surface properties with various π-conjugated molecules suitable for many applications.

Acceptor–acceptor-type conjugated polymer for use in n-type organic thin-film transistors and thermoelectric devices

The development of n -type conjugated polymers (CPs) forming an acceptor–acceptor (A–A)-type structure are quite challenging due to the synthetic limitation of imposing a functional group on the electron deficient aromatic structure. The diketopyrrolopyrroles (DPP) structure exhibits n -type characteristics; however, the extended π-structure enables stannylation at the terminal position. The stannylated DPP is beneficial for making n -type CPs, but its use in the development of n -type CPs and their application in n -type organic thin-film transistors and organic thermoelectric devices have been not extensively studied. In the present study, we synthesized the A–A-type conjugated polymer, poly [((2,5-bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)-2,5-dihydropyrrolo [3,4- c ]pyrrole-1,4-dione)-5,5′-diyl)- alt -((2,7-bis(2-ethylhexyl)benzo [lmn] [3,8]phenanthroline-1,3,6,8(2 H ,7 H )-tetraone)-4,9-diyl))] (PDPP-NDI), by Stille coupling of distannylated DPP and dibrominated naphthalene diimide (NDI). The alternating copolymerization of DPP and NDI moieties led to a low-lying LUMO energy level of −4.4 eV, suitable for electron transport. The n -type organic thin-film transistors were fabricated with PDPP–NDI, and a substantial average electron mobility of 3.78 × 10 −2 cm 2 V −1 s −1 was obtained after thermal annealing. The n -type organic thermoelectric devices were developed via n -doping, and PDPP–NDI exhibited n -type thermoelectric properties, with an average power factor of 1.82 × 10 −3 μW m −1 K −2 . • An acceptor–acceptor-structured n -type alternating copolymer, PDPP–NDI, was developed. • A small bandgap of 1.03 eV and deep LUMO energy level of −4.4 eV were achieved. • The n -type characteristics of PDPP–NDI were successfully utilized in n -type OTFTs and OTE devices. • The device characteristics of both OTFT and OTE devices were fully studied and discussed.

Multifunctional naphthalene diimide-based coordination polymers: Photochromism and solventchromism

Naphthalene diimides (NDIs), a class of organic dyes with high photochemical activity and high redox activity, have attracted considerable interest attributing to their photoinduced electron transfer to form stable radical anions upon irradiation in the presence of electron donors. In this study, a naphthalenediimide-based ligand and different aromatic carboxylic acids self-assembled in the presence of zinc ions, forming three novel coordination polymers, [Zn2 (DPMNI) (TPDC)2] (1), [Zn (DPMNI) (BPC)] (2), Zn (DPMNI) (HBTC) (3) (DPMNI = N,N′-bis(4-pyridylmethyl)-1,4,5,8-naphthalene diimide, H2TPDC = thiophene-2,5-dicarboxylic acid, H2BPC = 4,4′-biphenyldicarboxylic acid, H3BTC = 1,3,5-benzenetricarboxylic acid). These coordination polymers characterized by single-crystal X-ray diffraction, elemental analyses, IR spectroscopy, powder X-ray diffraction, and theromgravimetric analysis. Because of the presence of electron-deficient NDI moieties, they exhibit reversible photochromic properties. Furthermore, due to the different π–π interactions between the NDI moieties and aromatic carboxylic acid, compounds 1–3 exhibit different photosensitive properties. Moreover, the solvatochromic behaviour of compound 1 was also investigated.

Naphthalene diimide-incorporated helical thienoacene: a helical molecule with high electron mobility, good solubility, and thermally stable solid phase.

A Naphthalene diimide (NDI)-incorporated helical thienoacene was developed. The compound has high electron mobility (1.4 cm2 V-1 s-1) thanks to its two-dimensional π-π interaction assisted by the intermolecular C-HO hydrogen bonding of the NDI moieties. Moreover, its bow-shaped π-skeleton reduces molecular fluctuation and gives the compound a thermally stable solid phase, which enables us to fabricate thermally stable organic devices.

Polyoxometalate-based room-temperature phosphorescent materials induced by anion-π interactions.

A series of host-guest materials containing polyoxometalate anions and lanthanide-organic layers have been synthesized and structurally characterized. By anion-π interactions between the anions and the π-acidic naphthalenediimide moieties, the materials emit strong red room-temperature phosphorescence and exhibit reversible photochromism.

Intersystem Crossing in Naphthalenediimide-Oxoverdazyl Dyads: Synthesis and Study of the Photophysical Properties.

Oxoverdazyl (Vz) radical units were covalently linked to the naphthalenediimide (NDI) chromophore to study the effect of the radical on the photophysical properties, especially the radical enhanced intersystem crossing (REISC), which is a promising approach to develop heavy-atom-free triplet photosensitizers. Rigid phenyl or ethynylphenyl linkers between the two moieties were used, thus REISC and formation of doublet (D1 , total spin quantum number S=1/2) and quartet states (Q1 , S=3/2) are anticipated. The photophysical properties of the dyads were studied with steady-state and femtosecond/nanosecond transient absorption (TA) spectroscopies and DFT computations. Femtosecond transient absorption spectra show a fast electron transfer (<150 fs), and ISC (ca. 1.4-1.85 ps) is induced by charge recombination (CR, in toluene). Nanosecond transient absorption spectra demonstrated a biexponential decay of the triplet state of the NDI moiety. The fast component (lifetime: 50 ns; population ratio: 80 %) is assigned to the D1 →D0 decay, and the slow decay component (2.0 μs; 20 %) to the Q1 →D0 ISC. DFT computations indicated ferromagnetic interactions between the radical and chromophore (J=0.07-0.13 eV). Reversible formation of the radical anion of the NDI moiety by photoreduction of the radical-NDI dyads in the presence of sacrificial electron donor triethanolamine (TEOA) is achieved. This work is useful for design of new triplet photosensitizers based on the REISC effect.

Photochromic and photocontrolled luminescence properties of two metal-organic frameworks constructed from a naphthalene diimide derivative

Naphthalene diimides (NDIs), a class of organic dyes with high photochemical activity and strong luminescent characteristics, have attracted considerable interest because of their photoinduced electron transfer to form stable radical anions in the presence of electron donors upon irradiation. In this paper, two novel metal–organic frameworks constructed from NDIs chromophoric and aromatic dicarboxylic acids, [Zn2(DPMNI)(NCA)2·0.5DMF] (1), [Zn(DPMNI)(PTA)·DMF] (2), (H2NCA = 1,4-naphthalenedicarboxylic acid, H2PTA = p-phthalic acid, DPMNI = N,N′-bis(4-pyridylmethyl)-1,4,5,8-naphthalene diimide, DMF = N,N′-dimethylformamide), have been synthesized and characterized systematically. Because of the presence of electron-deficient NDI moieties, they exhibit reversible naked photochromic properties upon irradiation and photocontrolled luminescence due to the generation of NDI radicals. The carboxylate groups as electron donors play a key role in the photoinduced electron-transfer process, and the lone pair–π interaction is a preferred pathway to support photoinduced electron transfer from our work. This study has not only convincingly corroborated the relationship between the photoresponsive rate and non-covalent interactions, but also provided a feasible idea to design novel luminescence switching materials.

Switchable luminescent properties in two photochromic naphthalene diimide coordination networks

Photochromic materials as a new class of multifunctional materials have received much attention owing to their potential applications in many fields. In order to investigate the electron-transfer photochromic behaviour of coordination polymers, two new coordination polymers based on the electron-deficient naphthalene diimide (NDI) and dicarboxylate ligand, namely [Zn2(DPNDI)(TPDC)2] (1) [Cd6(DPNDI)(TPDC)6(DMF)6] (2) (DPNDI = N,N′-di(3-pyridyl)-1,4,5,8-naphthalene tetracarboxydiimide, H2TPDC = thiophene-2,5-dicarboxylic acid, DMF = N,N′-dimethylformamide), were synthesized under solvothermal condition and were characterized by elemental analysis, IR spectroscopy, thermogravimetric analyses, and single-crystal X-ray diffraction. Complex 1 is a three-dimensional coordination with rhombus channels, whereas complex 2 shows a sandwiched layer structure. Because of the presence of electron-deficient NDI moieties, complexes 1 and 2 can easily undergo photoinduced electron transfer and eye-detectable photochromic behaviour. Moreover, their luminescence can be switched by UV–Vis light irradiation and standing in the air.

Influence of Charge Distribution on Structural Changes of Aromatic Imide Derivatives upon One-Electron Reduction Revealed by Time-Resolved Resonance Raman Spectroscopy during Pulse Radiolysis.

Structural changes of aromatic imides upon one-electron reduction are investigated by time-resolved resonance Raman spectroscopy during pulse radiolysis. Significant downshifts are observed for both the aromatic ring stretching and carbonyl stretching modes, which are related to a reduction of the bond order and increase of the charge density on these moieties. For three aromatic imides, i.e., 1,8-naphthalene imide (1,8-NI), 2,3-naphthalene imide (2,3-NI), and naphthalene diimide (NDI), the extent of structural changes is found to follow the order: 2,3-NI > 1,8-NI > NDI, reflecting the influence of charge distribution on molecular structure. To further investigate this phenomenon, a series of homologous NDI derivatives with a substituted phenyl group at the imide position are studied. The Raman peaks between 1550 and 1600 cm-1, which are assigned to aromatic stretching vibrations of the NDI moieties,are found to be sensitive to the charge distribution: stronger electron-withdrawing substituents result in these peaks shifting to slightly higher wavenumbers. As supported by a spin density analysis, despite the fact that the added charge is mostly localized on the NDI moiety, in the presence of an electron-withdrawing group, the subtle charge is likely to delocalize on the phenyl fragment, alleviating the effect of one-electron reduction on the molecular structure.

Wrapping flexible metal–organic framework with organic polymers via site-specific radical polymerization from its crystal surface

In this study, we succeeded in the crystal surface modification of metal–organic framework (MOF) with an organic polymer by site-specific radical polymerization. A MOF was selected with interpenetrated structure containing a naphthalenediimide moiety with electron accepting capability. N, N-dimethylaniline, as an electron donating guest, induced electron transfer to the napthalenediimide moiety, generating radical anions on the pore and crystal surfaces, initiating radical polymerization. The resulting composite was examined in detail with XRD, TG, TEM, ICP, IR, gas adsorption, and fluorescent measurements, demonstrating that an organic polymer was generated only on the crystal surface, preserving the original porous property. In addition, higher structural stability in response to H2O was observed after polymer wrapping.

Intramolecular Energy and Electron Transfers in Bodipy Naphthalenediimide Triads

Borondipyrromethene (BDP) naphthalenediimide (NDI) triads (BDP-NDI) and diiodo-BDP derivative (DiiodoBDP-NDI)) were synthesized to study the Förster resonance energy transfer (FRET) and its impact on the triplet state formation and dynamics. In these triads, diiodo-BDP and BDP are the energy donors and NDI is the energy acceptor. Nanosecond transient absorption spectra of triads indicated that triplet state is localized on NDI moiety, either by selective photoexcitation of the Diiodo-BDP or NDI unit. The intersystem crossing (ISC) is attributed to intramolecular heavy atom effect. The triplet state quantum yield was found to be 54% with a lifetime of 38 μs. However, no triplet state is observed for BDP-NDI system either by exciting BDP or NDI unit. Thus, we confirmed that charge recombination does not produce a triplet state. Interestingly, DiiodoBDP-NDI can be used as broadband excitable (500-620 nm) triplet photosensitizer, and high triplet-triplet annihilation (TTA) upconversion quantum yield of ΦUC = 2.8% was observed with 9,10-bis(phenylethynyl)-anthracene (BPEA) as a triplet acceptor/emitter.

Naphthalenediimide (NDI)‐Conjugated Foldable Polyurethanes: Impact of Chromophoric Location on Hierarchical Supramolecular Assembly and Conductivity

AbstractThe manuscript reports supramolecular assembly and photophysical properties of two polyurethanes (P1, P2) with appended naphthalene‐diimide (NDI) chromophore which serves as a n‐type semiconductor. P1 and P2 are constitutional isomers and they differ in the location of the NDI moiety. In P1, NDI is a part of the polymer backbone (placed between the two urethane groups in each repeating unit) while in P2, it remains as a pendant group. In a non‐polar solvent like tetra‐chloroethylene (TCE), both adopt a pleated structure driven by intra‐chain H‐bonding among the urethane groups. Subsequently the secondary structure of P2 assembles to a meta‐stable spherical structure (similar to polymersome) which after 70–75 h transforms to nanotubes with the folded polymer chains constructing the wall of the tube. In sharp contrast, the intra‐chain folded conformation of P1, owing to its enhanced rigidity contributed by the synergistic π‐stacking and H‐bonding, does not get trapped in the spherical intermediate, but spontaneously grows to fibrils leading to macroscopic gelation within 30 min. Flash‐photolysis time‐resolved microwave conductivity (FP‐TRMC) measurements together with transient absorption spectroscopy studies revealed remarkably high charge carrier mobility (3×10−3 cm2 V−1 s−1) which can be attributed to the long range stacking order of the NDI chromophores in the fibrillar assembly of P1 while for the nanotubular structure of P2, the value was almost an order of magnitude less reflecting importance of the mesoscopic structure on generation of percolated pathway for efficient charge transport.

Star-like n-type conjugated polymers based on naphthalenediimide for all-polymer solar cells

We developed n-type conjugated polymers that contain a naphthalene diimide moiety with star-like molecular geometry that are synthesized by incorporating 1,3,5-trisphenyl-benzene as the branched unit into the linear copolymer N2200. The developed copolymers, NDIPh1 and NDIPh2, exhibited frontier molecular orbital energy levels and optical properties similar to those of N2200, whereas the melting and crystallization temperatures were simultaneously decreased due to the incorporated branched central unit. Both copolymers showed good miscibility with the widely used electron-donating copolymer poly[4,8-bis[5-(2-ethylhexyl)-2-thienyl]benzo[1,2-b:4,5-b′]dithiophene-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th). All-polymer solar cells (All-PSCs) based on PTB7-Th:NDIPh1 presented an impressive power conversion efficiency of 6.87%, which obviously exceeded the 5.75% efficiency obtained from the device based on N2200. The enhanced photovoltaic performance, by virtue of the improved short-circuit current density, can be attributed to the slightly enhanced electron mobility, higher exciton dissociation rates, and more efficient charge collection of NDIPh1-based device. These observations indicate that the developed star-like NDIPh copolymers can be promising n-type acceptors for the construction of high-performance all-PSCs.