Abstract  A series of quadrupolar and tribranched molecules were synthesized in order to examine the role of the edge substituents on their photophysical and two-photon absorption properties. Two-photon absorption cross sections, delta, of the molecules were determined in THF solution using a two-photon excited fluorescence technique with femtosecond pulsed excitation. The quadrupolar molecules contained a fluorene or alcoxy-substituted phenylene central core together with various electron accepting edge substituents such as pyridine, terpyridine, phthalimide and naphthalimide. The tribranched molecules contained triphenylamine at the center and terpyridine or phthalimide substituents at the periphery. It was found that edge phthalimide substituent favour high h values. 6 Values as high as 1660 GM and 1500 GM were obtained from the phthalimide-fluorene-phthalimide and phthalimide-phenylene-phthalimide molecules. respectively; in the case of the tribranched molecule with a phthalimide substituent, a delta-value of 1200 GM was found. (C) 2008 Elsevier Ltd. All rights reserved.

Abstract  The preparation of smart photonic gels composed of two orthogonally self assembled fibrillar networks is reported. The molecular gelators are a light acceptor derived from 4-amino-1,8-naphthalimide and an acridine-based energy donor. Fibrillar orthogonal assembly of both chromophores is a requisite for light harvesting to be observed which results in emission from the naphthalimide-based acceptor upon irradiation of the acridine-derived donor with a significant Stokes shift of ca. 200 nm. Energy transfer is present both in the form of molecular gels in acetonitrile and in the solid-like xerogels and efficiently visualized both by fluorescence spectroscopy and confocal laser scanning microscopy. The chameleonic, stimuli responsive behavior is linked to the fact that the gel network formed by the acridine derivative can be selectively disassembled by means of temperature changes or chemical species. For example, the light harvesting process can be switched off/on by addition of HCl or NaOH respectively, affording a new type of stimuli responsive photonic soft materials.

Abstract  A fluorophorel-spacer-receptor-spacer-fluorophore, dyad was prepared and photophysically characterized. The two spectrally well-differentiated fluorophores are 1,8-naphthalimide and its 4-amino-substituted derivative, the latter showing strong ICT emission. The receptor unit consists of a tertiary amine, which leads to site-selective PET (only the 1,8-naphthalimide part gets quenched). This process can be blocked by protonation of the tertiary amine, which, on the other hand, results in enhanced singlet-singlet energy transfer between the 1,8-naphthalimide and 4-amino-1,8-naphthalimide parts (Phi(EET) = 0.27 and 0.59 for neutral and monoprotonated form, respectively). In acetonitrile, the monoprotonated form can be deprotonated by sufficiently basic anions like fluoride in micromolar concentration (<20 mu M). The observed fluorescence\ quenching, due to PET-reactivation, is ca. 41%. Further addition of fluoride in concentrations > 1 mM leads to deprotonation of the 4-amino group of one of the naphthalimides, which is accompanied by more fluorescence quenching (ca. 93%). The resulting double-sigmoidal titration curve enables the implementation of ternary logic. Using fluoride anions as degenerate inputs results in a ternary NOR logic gate, which is demonstrated for the first time.

Abstract  A series of galactosyl naphthalimide-piperazine derivatives have been synthesized as intracellular pH and lysosome-targeting imaging probes for live human hepatoma cells. The probes show good sensitivity in both aqueous buffer and intracellular environments. Incorporation of the galactose moiety with the pH probes facilitates their specific endocytosis and, thus targeted trafficking to lysosome, by the asialoglycoprotein receptor of human hepatoma cells. The acidic intracellular pH of live human hepatoma cells gives rise to a fluorescence "turn-on" signal of the probes probably via a modulation of the photo induced electron transfer (PET) mechanism. Additionally, galactosylation of the probes enhances their selective accumulation in lysosome and decreases the cytotoxicity. (C) 2016 Elsevier Ltd. All rights reserved.

Abstract  A pair of four-armed star and dicyclic 8-shaped poly(tetrahydrofuran)s, poly(THF)s, possessing a perylene diimide group at the core position (Ia and Ib, respectively) were synthesized by means of an electrostatic self-assembly and covalent fixation (ESA-CF) protocol. Mono- and bifunctional poly(THF)s having N-phenylpiperidinium salt end groups accompanying a perylene diimide tetracarboxylate as a counteranion were prepared by the ion-exchange reaction, and the subsequent covalent conversion by reflux in toluene afforded the corresponding core-fluorescent four-armed star and dicyclic 8-shaped poly(THF)s, (Ia and Ib, respectively) for the use of single-molecule fluorescence microscopy measurements. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract  Solubility studies were performed in aqueous solutions of 1,8-naphthalimides and 1,4,5,8-naphthalenediimides (Scheme 1). A large solubility increase was found for N-butyl-1,8-naphthalimide (MBN) and N,N'-dibutyl-1,4,5,8-naphthalenediimide (DBN) in the presence of a-cyclodextrin (alpha-CD), indicating the formation of inclusion complexes. The presence of the N-butyl group is required for complex formation, leading to the conclusion that the butyl groups are the binding sites for alpha-CD. Accordingly, the analysis of solubility isotherms for the systems MBN/alpha-CD and DBN/alpha-CD showed the presence of 1:1 complexes for the former and of both 1:1 and 1:2 complexes for the latter. Association constants for the two systems were estimated, giving K = 470 M-1 for the MBN/alpha-CD complex and K-11 = 1316 M-1 and Kit = 329 M-1 for the stepwise association constants in the DBN/alpha-CD system. MBN undergoes hydrolysis in water, but the reaction is inhibited upon complexation with alpha-CD. The remarkable solubilization in water and stabilization toward hydrolysis makes these novel complexes of imides and diimides with alpha-CD potentially useful in the pharmaceutical applications known for these imides, as well as in the preparation of new materials, like polyimide-based polyrotaxanes.

Abstract  Perylenediimide (PDI)-based materials exhibit great potential as non-fullerene acceptors in bulk-heterojunction (BHJ) organic solar cells (OSCs). Recent investigations have revealed that PDI molecules with a twisted structure could disrupt aggregation of perylene unit. Here, we present a PDI monomer via bay-substitutions with four fused naphthalene units by three-step reactions, named TN-PDI. The introduction of four fused naphthalene rings into the bay positions of PDI unit leads to a strong steric hindrance with a twist angle of 33 degrees between the two PDI subplanes. Blended with a wide-band gap polymer donor (PDBT-T1), the TN-PDI based non-fullerene solar cells show power conversion efficiency (PCE) of 3.0%. Our results indicate that the bay-substitutions with fused aromatic substitutions could be an efficient approach to develop monomeric PDI acceptors.

Abstract  The system surface was labeled with blue emitting 1,8-naphthalimide "donor" dyes capable of absorbing light and efficiently transferring the energy to a single yellow-green emitting 1,8-naphthalimide "acceptor" dye. The overlap between the blue emission of the donor and the absorbance of the acceptor (focal dye) was >70%. Due to the energy transfer from the periphery to the focal 1,8-naphthalimide chromophore (67%) the core fluorescence (lambda(ex) = 360 nm) was enhanced >36 times. It was also found that the novel light harvesting system displayed sensitive fluorescence signaling over a wide pH scale, which was ascribed to photoinduced electron transfer from the dendron bone to the blue emitting periphery. In acidic media the electron transfer was "switched off" and, in turn, the periphery emission was "switched on", resulting in energy transfer enhancement to the focal chromophore up to 92%. This indicates the high potential of the novel light harvesting system as an efficient pH hemosensing material. (C) 2008 Elsevier Ltd. All rights reserved.

Abstract  Four unsaturated derivatives of 1,8-naphthalimide have been synthesized and their spectrophotometric properties and Cielab colour coordinates determined. They can copolymerize with styrene, and the coloured polymers thus obtained have good resistance to wet treatments and to organic solvents.

Abstract  The present study describes the infrared characterization of some newly synthesized photoactive poly(amidoamine) dendrimers, whose peripheries have been modified with 1,8-naphthalimides. Main attention is being paid to the effect that different substituents at C-4 position of the naphthalene ring have upon the dendrimers polarization. Infrared studies have shown that the dendrimer generations have similar polarizations as the dendrimer molecules wherein no intermolecular hydrogen bonds occur. (C) 2004 Elsevier Ltd. All rights reserved.

Abstract  Novel poly(propylenamine) first and second generation dendrimers in which the periphery was modified with 1,8-naphthalimide units were synthesized. Acetonitrile solutions of the materials were subjected to photophysical investigation to evaluate their capability to detect metal cations, by monitoring changes in their absorption and fluorescence spectra in the presence of Ag(+), Cu(2+), Co(2+), Ni(2+), Fe(3+) and Zn(2+). The potential of the dendrimers to detect metal ion pollutants was estimated. (C) 2009 Elsevier Ltd. All rights reserved.

Abstract  Novel non-fullerene acceptors with an A(1)-A-A(1) framework were designed and synthesized, in which benzothiadiazole and diketopyrrolopyrrole building blocks were employed as the A unit and naphthalimide units were incorporated as the A(1) units. Both acceptor systems exhibited a broadened absorption spectra from 300 nm to 700 nm in contrast to that of fullerene derivatives. Meanwhile, high lying LUMO energy levels were also observed for both developed acceptors. To investigate photovoltaic properties of the acceptors, bulk-heterojunction organic solar cells were fabricated using an established electron donating polymer as the donor material. As anticipated, efficient non-fullerene OSCs with high Voc values up to 1.01-1.12 V were achieved when the new molecules were employed as electron acceptors, leading to the PCE values of 1.23% and 1.64% in their solar cells. Our results here demonstrate that the A(1)-A-A(1) type small molecule containing naphthalimide building blocks in molecular backbone could be the promising electron acceptor in organic solar cells. (C) 2016 Elsevier Ltd. All rights reserved.

Abstract  In this paper, the surface modi. cation of silk fiber using anhydrides to graft the polysaccharide chitosan and dyeing ability of the grafted silk were studied. Silk fiber was degummed and acylated with two anhydrides, succinic anhydride (SA) and phthalic anhydride (PA), in different solvents (dimethyl sulfoxide (DMSO) and N,N-dimethyl formamide (DMF)). The effects of anhydrides, solvents, anhydride concentration, liquor ratio (L: R) and reaction time on acylation of silk were studied. The polysaccharide chitosan was grafted to the acylated silk fiber and dyed by acid dye (Acid Black NB. B). The effects of pH, chitosan concentration, and reaction time on chitosan grafting of acylated silk were investigated. The physical properties show sensible changes regardless of weight gain. Scanning electron microscopy (SEM) analysis showed the presence of foreign materials firmly attached to the surface of silk. FTIR spectroscopy provided evidence that chitosan was grafted onto the acylated silk through the formation of new covalent bonds. The dyeing of the chitosan grafted-acylated silk fiber indicated the higher dye ability in comparison to the acylated and degummed silk samples. The mechanism of chitosan grafting over degummed silk through anhydride linkage was proposed. The findings of this research support the potential production of new environmentally friendly textile fibers. It is worthwhile to mention that the grafted samples have antibacterial potential due to the antibacterial property of chitosan molecules. (C) 2008 Elsevier B. V. All rights reserved.

Abstract  A new perylene diimide derivative, namely N,N'-diallyl-1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxylic acid diimide (phenoxy-allyl-PTCDI, abbreviated PA-PTCDI), is introduced. The investigations presented in this paper aim at finding a molecule for use as a sensitzer in thin film silicon solar cells in order to enhance efficiency. The synthesis is described along with optical and electrochemical measurements of PA-PTCDI in solution. A good agreement is found between the measured data and theoretical calculations. The molecule is characterized further by optical and photoemission data on thin films, which also show that the dye can be sublimed in vacuum. The interface between the dye and silicon is investigated on the model system Si(111):H with synchrotron-induced photoemission spectroscopy. The result is an electronic lineup with the gap centers of silicon and PA-PTCDI almost at identical positions and thus very similar band discontinuities from the lowest unoccupied molecular orbital (LUMO) to the conduction band as well as from the highest occupied molecular orbital (HOMO) to the valence band. This clearly permits a transfer of photogenerated electrons and holes from PA-PTCDI to silicon. The experimental valence band discontinuity matches very well the value calculated for a very similar PTCDI molecule.

Abstract  Three new derivatives of triphenylamine containing different number of 1,8-naphthalimide moieties linked via ethynyl linkages were obtained by a Sonogashira cross-coupling reaction and their properties were studied. The glass-forming derivatives showed glass transition temperatures ranging from 73 to 96 degrees C. They showed high thermal stabilities with the temperatures of the onset of thermal degradation ranging from 421 to 462 degrees C. Fluorescence quantum yields of the dilute solutions in nonpolar solvents of the compounds ranged from 0.063 to 0.94 while those of the solid films were in the range of 0.011-0.25. Small singlet-triplet gap was predicted by DFT calculations, which was confirmed by the similarity between the prompt and the delayed fluorescence energies. Cyclic voltammetry measurements revealed close values of the solid state ionization potentials ranging from 5.48 to 5.61 eV and electron affinities ranging from -3.29 to -3.16 eV. The layer of 4,4'-((di(N-(2-ethylhexyl)-1,8-naphthalimide-4-yl)phenyl)ethynyl)benzenamine exhibited effective charge-transport with hole drift mobilities exceeding 10(-2) cm(2)/Vs. Good intrinsic hole transport parameters were predicted by theoretical estimations. Both efficient fluorescence and high hole mobilities are found to be positively influenced by the presence of ethynyl bridges, (i) allowing for molecular planarization and high hole mobility and (ii) inducing large space separation between the HOMO and LUMO localizations, with direct impact in singlet triplet splitting.

Abstract  Solution-processable donor-acceptor molecules consisting of triphenylamine core and 1,8-naphthalimide arms were designed and synthesized by palladium-catalyzed Heck reaction. Dilute solutions of the synthesized compounds show strong absorption peaks in the visible wavelength range from 400 to 550 nm, which can be ascribed to the intramolecular charge transfer. Fluorescence quantum yields of dilute solutions of the synthesized materials range from 0.45 to 0.70, while those of the solid samples are in the range of 0.09-0.18. The synthesized molecules exhibit high thermal stability with the thermal degradation onset temperatures ranging from 431 to 448 degrees C. The compounds form glasses with glass-transition temperatures of 55-107 degrees C. DFT calculations show that HOMO and LUMO orbitals are almost entirely localized on the donor and acceptor moieties, respectively. Consequently, the frontier orbital energies for the three synthesized compounds are similar and practically do not depend on the number of 1,8-naphthalimide moieties. Ionization potentials of the solid samples (5.75-5.80 eV) are comparable. The charge-transporting properties of the synthesized materials were studied using xerographic time-of-flight method. Hole mobilities in the layers of the compounds having one and two 1,8-naphthalimide moieties exceed 10(-3) cm(2).V-1.s(-1) at high electric fields at room temperature. The differences on the hole mobilities between the three synthesized compounds are discussed in the frame of Marcus theory by comparing the reorganization energy and electronic coupling parameters.

Abstract  Structural properties of a single crystal and of a thin film of 3,4,9, 10-perylene-tetracarboxylic-acid-diimide are compared. The two samples are both obtained from the vapour phase, the latter being deposited at room temperature, in an ultrahigh vacuum environment, on a clean Pt(100) substrate. In the single crystal we have pointed out interactions between adjacent molecules by overlapping of the pi systems in the stacks and by hydrogen bonds between neighbouring stacks. The various surface unit cells of the nanocrystals from the film, identified by means of scanning tunnelling microscopy, are not comparable to those expected from the X-ray diffraction study of the single crystal and to those already published for other substrates. This fact clearly highlights the role played by the type of substrate chosen and/or the substrate-molecule interaction that affects the stacking and crystallinity of the growing crystal on top. (c) 2006 Elsevier B.V All rights reserved.

Abstract  The [Ru(II) (phen)(2)(pPDIp)](2+) complex, where pPDIp is the symmetric bridging ligand phenanthroline-perylene-phenanthroline, shows strong electronic absorption bands attributed to the pPDIp and {Ru(phen)(2)}(2+) moieties in acetonitrile. The charge-separated intermediate {Ru(III) (phen)(2)(pPDIp(-center dot))} was detected by transient absorption spectroscopy upon electronic excitation in either the pPDIp or the complex moieties. The charge-separated intermediate species decays to generate the triplet state (3)*pPDIp-Ru(II) (tau(P) = 1.8 mu s) that sensitizes the formation of singlet molecular oxygen with quantum yield phi(Delta) = 0.57. The dyad in deaerated acetonitrile solutions is reduced by triethylamine (NEt3) to the [Ru(II) (phen)(2)(pPDIp(center dot-))] radical anion in the dark. The electron-transfer reaction is accelerated by light absorption. By photolysis of the radical anion, a second electron transfer reaction occurs to generate the [Ru(II)(phen)(2)(pPDIp(center dot-))] dianion. The changes of the color of solution indicate the redox states of complexes and offer a sensitive reporter of each stage of redox reaction from start to finish. The reduced complexes can be converted to the initial complex, using methyl viologen or molecular oxygen as an electron acceptor. The accumulation of electrons in two well-separated steps opens promising opportunities such as in catalysis.

Abstract  A series of novel zinc complexes containing 4-2',2"-dipyridylamino-1,8-naphthalimide have been synthesized by a concise route. The luminescent properties of these materials have been investigated. Complexes Zn (N-pentyl-4-2',2"-dipyridylamino-1,8-naphthalimide)Cl-2 and compound 6 Zn(SMDP)Cl-2 show strong fluorescence in solution. In solid state the coordination of 1 and 5 ligands to a zinc center cause a blue shift of emission wavelength. They have absorption bands in the UV or near-UV region, and have the potential function as fluorescent sensors.

Abstract  The charge generation and recombination processes following photo-excitation of a low-bandgap polymer:perylene diimide photovoltaic blend are investigated by transient absorption pump-probe spectroscopy covering a dynamic range from femto-to microseconds to get insight into the efficiency-limiting photophysical processes. The several tens of picoseconds, and its efficiency is only half of that in a polymer:fullerene photoinduced electron transfer from the polymer to the perylene acceptor takes up to blend. This reduces the short-circuit current. Time-delayed collection field experiments reveal that the subsequent charge separation is strongly field-dependent, limiting the fill factor and lowering the short-circuit current in polymer:PDI devices. Upon excitation of the acceptor in the low-bandgap polymer blend, the PDI exciton undergoes charge transfer on a time scale of several tens of picoseconds. However, a significant fraction of the charges generated at the interface are quickly lost because of fast geminate recombination. This reduces the short-circuit current even further, leading to a scenario in which only around 2596 of the initial photoexcitations generate free charges that can potentially contribute to the photocurrent. In summary, the key photophysical limitations of perylene diimide as an acceptor in low-bandgap polymer blends appear at the interface between the materials, with the kinetics of both charge generation and separation inhibited as compared to that of fullerenes.

Abstract  We demonstrate new fluorophore-labelled materials based on acrylamide and on oligo(ethylene glycol) (OEG) bearing thermoresponsive polymers for sensing purposes and investigate their thermally induced solubility transitions. It is found that the emission properties of the polarity-sensitive (solvatochromic) naphthalimide derivative attached to three different thermoresponsive polymers are highly specific to the exact chemical structure of the macromolecule. While the dye emits very weakly below the LCST when incorporated into poly(N-isopropylacrylamide) (pNIPAm) or into a polyacrylate backbone bearing only short OEG side chains, it is strongly emissive in polymethacrylates with longer OEG side chains. Heating of the aqueous solutions above their cloud point provokes an abrupt increase of the fluorescence intensity of the labelled pNIPAm, whereas the emission properties of the dye are rather unaffected as OEG-based polyacrylates and methacrylates undergo phase transition. Correlated with laser light scattering studies, these findings are ascribed to the different degrees of pre-aggregation of the chains at low temperatures and to the extent of dehydration that the phase transition evokes. It is concluded that although the temperature-triggered changes in the macroscopic absorption characteristics, related to large-scale alterations of the polymer chain conformation and aggregation, are well detectable and similar for these LCST-type polymers, the micro-environment provided to the dye within each polymer network differs substantially. Considering sensing applications, this finding is of great importance since the temperature-regulated fluorescence response of the polymer depends more on the macromolecular architecture than the type of reporter fluorophore.

Abstract  A novel intramolecular donor-acceptor system of four isomers consisting of 7H-benzimidazo(2,1-a)benz(d,e)isoquinolin-7-ones and diarylamine units was synthesized and characterized: the absorption and fluorescence spectra of the system in a variety of solvents were investigated. Intramolecular charge transfer was confirmed within the system by virtue of shifts in emission maximum with increasing solvent polarity; a high dipole moment for the intramolecular excited State Was calculated using the Lippert equation. Shorter lifetimes were observed in polar solvents compared with those in non-polar solvents, indicating strong dipole-dipole interactions occurred. The ground-state geometry, lowest energy transition and the UV-vis spectrum Of the system Were Studied using density functional theory and time-dependent density functional theory at B3LYP/6-31G' level, which showed that the Calculated outcomes were in good agreement with experimental data. (C) 2008 Elsevier Ltd. All rights reserved.

Abstract  The synthesis, characterization, and photovoltaic performance of a series of N-annulated PDI materials is presented. Four novel N-annulated PDI compounds are reported, each of which can be synthesized in gram scale without the need for purification using column chromatography. N-Annulation of the PDI chromophore results in a decrease in electron affinity and lowering of the ionization potential, and renders the chromophore insoluble in organic solvents. Installation of an alkyl group improves the solubility. Single crystal X-ray analysis reveals a bowing of the aromatic backbone and compression of phenyl rings adjacent to the N atom. A brominated N-annulated PDI derivate represents a valuable synthon for creating novel multi-PDI chromophore materials. To demonstrate the utility of the new synthon for making electron transporting materials, a dimerization strategy was employed to create a dimeric PDI material. The PDI dimer has excellent solubility and film forming ability along with energetically deep HOMO and LUMO energy levels. X-ray crystal structure analysis reveals that, despite the isotropic nature of the molecule, only 1-D charge transport pathways are formed. Solar cells based on the new PDI dimer with the standard donor polymer PTB7 gave a high power conversion efficiency of 2.21% for this system. Through N-alkyl chain modification this PCE was increased to 3.13%. Further increases in PCE to 5.54% and 7.55% were achieved by using the more advanced donor polymers PTB7-Th and P3TEA, respectively. The simple yet high performance devices coupled with the highly modular and scalable "acceptor" synthesis make fullerene-free organic solar cells an attractive and cost-effective clean energy technology.

Abstract  Four electron deficient small molecules based on the diketopyrrolopyrrole (DPP) chromophore were synthesized using microwave-assisted direct arylation reactivity. These molecules are based upon an acceptor-donor-acceptor-donor-acceptor (A(1)-D-A(2)-D-A(1)) framework, where DPP is utilized as the central acceptor (A(2)) unit. We compared the effect of naphthalimide vs. phthalimide terminal acceptors (A(1)), and different DPP (A(2)) alkyl groups, on the optical, thermal, electrochemical and electronic properties. A combination of absorption and emission spectroscopy, differential scanning calorimetry, thermal gravimetric analysis, cyclic voltammetry, ultraviolet photoelectron spectroscopy, charge carrier mobility, and DFT calculations were used to characterize the four materials. All compounds were found to have narrow band-gaps, deep HOMO/LUMO levels, and were able to effectively act as electron transport materials.

Abstract  A series of novel 6-(2-substituted-1,3,4-oxadiazol-5-yl)-2-phenylthieno[2,3-d]-pyrimidine fluorescent compounds were obtained by the condensation of 6-(2-methylthio-1,3,4-oxadiazol-5-yl)-2-phenylthieno[2,3-d]pyrimidine with appropriate secondary amines. The structures were characterized by 1R, (1)H NMR, mass, elemental analysis and UV-vis spectroscopy and the fluorescence characteristics were investigated in ethyl acetate and acetone by UV-vis absorption and emission spectra. The absorption spectra and fluorescence characteristics were correlated with substituents of the 6-(2-substituted-1,3,4-oxadiazol-5-yl)-2-phenylthieno[2,3-d]pyrimidine compounds and solvent polarity. The novel compounds also displayed intense blue to yellow-green fluorescence in ethyl acetate and acetone solutions. (c) 2008 Elsevier Ltd. All rights reserved.