Synthesis and photochemical properties of two ICT compounds with naphthalimide and diarylamine units

Two new diarylamine-substituted 1, 8-naphthalimide derivatives are synthesized by Cu I/18-crown-6/K2CO3 catalyst system and characterized by Fourier transform infrared （FT- IR）, ^1H-NMR and elemental analyses. The UV-vis absorption and photoluminescent （PL）spectra of the systems in n-hexane, tetrahydrofuran（THF）, and CH2Cl2 are investigated. These naphthalimide molecules have an absorption band centered at about 450 nm, which is assigned to an intramolecular chargetransfer （ICT）transition, and they emit light at 492, 501 nm in a nonpolar solvent such as n-hexane, and at 600, 620 nm in a polar solvent such as CH2Cl2. From the Lippert-Mataga equation, the difference of the dipole moment between the excited state and the ground state is estimated to be 9.2 and 9.8 D for 4- （ diphenylamine ）-N-（ 2-methoxyphenyl ）-1, 8-naphthalimide （ DMN-1 ） and 4-（ 2-naphthylphenylamine ）-N-（ 2- methoxyphenyl）-1, 8-naphthalimide （DMN-2）, respectively. This large change in the dipole moment upon excitation is typical for photoinduced ICT processes.

Synthesis and near-infrared characteristics of novel perylene bisimide dyes bay-functionalized with naphthalimide chromophores

Novel perylene bisimide dyes bay-functionalized with naphthalimide chromophores have been prepared conveniently by coupling of 1,8-naphthalimide and dibromoperylene bisimides. Their optical properties were investigated by UV-vis and fluorescence spectroscopy. The absorption spectra of these compounds showed wide spectral responses from 300 to 700 nm, which would be potentials for application as organic solar cells.

Alkynyl-modified Naphthalimide:Synthesis,Crystal Structure and Fluorescence Spectrum

A novel alkynyl substituted N-aryl-1,8-naphthalimide II （C20H11NO2） was synthesized for the discovery and evaluation of new fluorescence probes, and was characterized by X-ray crystal diffraction. It crystallizes in monoclinic, space group P21/n with a = 15.898（3）, b = 5.0102（10）, c = 17.962（4）A, β = 92.97（3）°, V = 1428.7（5） A^3, Z = 4, Mr = 297.30, Dc = 1.382 g/cm^3, F（000） = 616,/J = 0.090 mm^-1, S = 1.011, the final R = 0.0542 and wR = 0.1204 for 1669 observed reflections with I 〉 2σ（I） and 212 variable parameters. Hydrogen-bounding and n-stacking interactions were discussed. The influence of acetylene group on the fluorescence properties was also investigated. In comparison with N-phenyl-1,8-naphthalimide I （C18H11NO2）, few new structure characters and fluorescence properties of the title compound have been found.

White light generation by regulating hydrogen bond-sensitive ESPT of naphthalimide dyes

White light emitting systems of pure organic materials have attracted extensive research interest due to their better compatibility and functional scalability.The reported organic white light materials are mainly based on the multi-channel emission regulation of the compound itself or the mixing of multicolor luminescence materials,but studies on the dependence between multicolor luminescence and the external environment are lacking,which limits the application of these materials in areas such as identification and sensing.This paper reports that the 4-or 3?hydroxyl-substituted naphthalimides NapH1 and NapH2 form intermolecular hydrogen bonds with adjacent molecules in the environment,and undergo excited-state intermolecular proton transfer under irradiation,resulting in blue-yellow or blue-red dual fluorescence emission,respectively.Since the two compounds have different two-color luminescence channels and the two-color intensity ratio is affected by the environment,and the intermolecular hydrogen bond is determined by the hydrogen bond receptor,polarity,and temperature in the environment,the full spectrum from blue to red light and white light emission can be obtained by adjusting the mixing ratio of the two dyes and the solvent polarity and the ambient temperature.This environmentally sensitive white emission is used to detect the alkalinity of different papers,and the dyed paper can be used as a test strip for acid-base vapor detection.

A series of naphthalimide azoles: Design, synthesis and bioactive evaluation as potential antimicrobial agents

A series of naphthalimide azoles as potential antibacterial and antifungal agents were conveniently and efficiently synthesized starting from commercially available 6-bromobenzo[de]isochromene-l,3-dione. All the new compounds were characterized by NMR, IR, MS and HRMS spectra. Their antimicrobial activities were evaluated against four Gram-positive bacteria, four Gram-negative bacteria and two fungi using two-fold serial dilution technique. The biological assay indicated that most of the prepared compounds exhibited inhibition to the tested strains. In particular, the triazolium derivatives not only gave higher ef- ficacy than their corresponding precursory azoles, but also demonstrated comparable or even better potency than the reference drugs Chloromycin, Orbifloxacin and Fluconazole. Some factors including structural fragments, pH and ClogP values of the target molecules were also preliminarily discussed.

Aggregation-induced emission or aggregation-caused quenching?Impact of covale nt bridge between tetraphenylethene and naphthalimide

Understanding the physical mechanisms governing aggregation-induced-emission(AIE)and aggrega-tion-caused-quenching plays a vital role in developing functional AIE materials.In this work,tetraphenylethene(TPE,a classical AiEgen)and naphthalimide(NI,a popular fluorophore with ACQ characteristics)were connected through non-conjugated linkages and conjugated linkages.We showed that the nonconjugated-linkage of TPE to NI fragments leads to substantial PET in molecular aggregates and ACQ.In con trast,the conjugated conn ection between TPE and NI moieties results in the AIE phenomenon by suppressing twisted intramolecular charge transfer.This work provides an important guideline for the rational design of AIE materials.

Highly sensitive and selective ratiometric fluorescent copper sensors: Different binding affinities modulated by three separate side chains of naphthalimide

A series of compounds 1-11 with different side chains of naphthalimide as fluorescent copper sensors were designed and synthesized. Compounds 1, 9, 10 and 11 presented a high selectivity to Cu2+ in a neutral aqueous environment. Here 1, 9 and 10 showed selectivity and affinity to Cu2+ with an association constant of about ～106. It gave somewhat response to Ag+, Co2+, Ni2+ and Fe2+ while 1 detected copper. 9 and 10 displayed better selectivity by changing their hydrophobic side chains to the hydrophilic ones on imide moieties. 11, with one flexible side chain, showed high selectivity and an association constant (Ka = 2.2 × 108), which were much higher than those of 1, 9 and 10. These results indicated that the selectivity and affinity could be improved by changing side chains of naphthalimide. That might provide a novel strategy or method for the development of fluorescent sensors.

Naphthalimide-modified near-infrared cyanine dye with a large stokes shift and its application in bioimaging

Developing the novel fluorescent dyes with a larger Stokes shift is still a challenge in the research of fluorescence probes. In this work, a naphthalimide-modified near-infrared cyanine dye with an emission at 785 nm has been synthesized for lysosome-targeting imaging. This fluorescent dye showed a large Stokes shift（up to 165 nm） and favorable lysosome-targeting property, which facilitated it to be a potential candidate for studying of lysosomal functions. The result also indicated that the probe is a promising contrast agent for in vivo imaging in mouse models.

Novel benzimidazole derived naphthalimide triazoles: synthesis, antimicrobial activity and interactions with calf thymus DNA

A novel series of benzimidazole derived naphthalimide triazoles and some corresponding triazoliums have been successfully synthesized and characterized by 1H NMR, 13 C NMR, 1H-1H COSY, IR and HRMS spectra. All the new compounds were screened for their antimicrobial activities in vitro by two-fold serial dilution. 2-Chlorobenzyl triazolium 8g and compound 9b with octyl group exhibited the best antibacterial activities among all the tested compounds, especially against S. aureus with inhibitory concentration of 2 μg/mL which was equipotent potency to Norfloxacin(MIC=2 μg/mL) and more active than Chloromycin(MIC=7 μg/mL). Triazoliums 8g and 8f bearing 3-fluorobenzyl moiety displayed the best antifungal activities(MIC=2-19 μg/mL) against all the tested fungal strains without being toxic to PC12 cell line within concentration of 128 μg/m L. Further investigations by fluorescence and UV-Vis spectroscopic methods revealed that the compound 8g could effectively intercalate into calf thymus DNA to form the 8g-DNA complex which could block DNA replication, exerting powerful antimicrobial activities.

Anaphthalimide-based fluorescent probe for mercapto-containing compounds

A polarity-sensitive fluorescent probe MNP was rationally designed and synthesized with naphthalimide as the fluorophore and maleimide as the receptor for thiols. MNP is weakly fluorescent due to the photoinduced electron-transfer （PET） from the fluorophore to the receptor, and it displays evidently solvatochromic UV-vis and fluorescence spectra： the emission shifted from 495 nm in n-hexane to 545 nm in phosphate buffer solution. Michael addition reaction between thiols and the maleimide in MNP inhibited the PET process, which led to about eight-fold fluorescence enhancement. In addition, MNP showed highly sensitivity to rnercapto-containing proteins and it could detect as low as 20.4 μg/mL of BSA in PBS. MNP has potential in fluorescent imaging of thiols in living cells.

A ratiometric near-infrared naphthalimide-based fluorescent probe with high sensitivity for detecting Fe^(2+)in vivo

Iron is one of the essential trace elements in the human body.It plays an important role in human biology and pathology.Deregulation of iron levels in cells is associated with disease development.In this work,we synthesized a novel near-infrared intramolecular charge transfer(ICT)based ratiometric fluorescent probe to detect Fe^(2+),by using naphthalimide and indole moieties as building blocks.Our work showed that the radiometric probe has excellent selectivity,sensitivity and rapid response.Moreover,we could successfully perform real-time monitoring of Fe^(2+) in He La cells and C.elegans.

A hydrophilic fluorescent polymer containing naphthalimide moiety as chemosensor for microbioreactors

A novel hydrophilic copolymer P(NI-HEMA) containing the pendant group of naphthalimide moiety has been prepared. In the aqueous buffer solution, its film on the glass substrate shows an obvious fluorescence change and excellent linear relevance in the pH range of 5.8-8.0. Specifically, using the isobestic point at 406 nm as excitation wavelength can avoid the UV irradiation and the tedious calibration process. The film stability and hydrophilicity of copolymer P(NI-HEMA) were studied. Because of the easy synthesis, low price and high linear relevance to pH, the hydrophilic chemosensor film of P(NI- HEMA) could be potentially applied as a low-cost pH indicator for high-throughput bioprocessing in microreactors.

Synthesis of 1,8-naphthalimide-based fluorescent nano-probes and their application in pH detection

Two kinds of fluorescent nano-probes（pH-A and pH-B） with different diameters for the determination of H＋concentration, based on photo-induced electron transfer mechanism, were synthesized through click reaction. In which 1,8-naphthalimide was employed as the fluorophore and N,N-dimethylethylenediamine as the receptor. The effects of particle size and linker length on the photophysical properties of the probe were studied. The results revealed that the nano-probes were more sensitive toward pH with increasing particle size. The fluorescence intensity at 529 nm（I529） of the nano-probe p H-A of 120 nm exhibited good linear relationship with solution＇s pH in the range of 6–8. The probe p H-A displayed excellent selectivity and competition toward proton over other possible coexisted ions, and it could be applied to detect pH in realistic samples（river water, urine）.

NAPHTHALIMIDE BASED DISPERSE DYES FOR NYLON 6 AND POLYESTER(PET) FIBERS:SYNTHESIS AND EVALUATION OF TECHNICAL PROPERTIES IN THE PRESENCE OF UREA

Technical properties of two naphthalimide based disperse dyes on nylon 6 and polyester fibers were investigated in the presence of urea. The two naphthalimide based disperse dyes were synthesized. The dyes were purified and then fully characterized using 1H-NMR, FTIR and melting point analysis. Dispersion of the dyes was prepared in water and applied on nylon 6 and PET fibers. The dyes offered good build-up properties on the substrates. In order to increase dye adsorption of the substrates, urea was added into the dyebath. By adding urea, the dye adsorption of polyester was increased significantly, while the increase of that of nylon 6 was not marked. The dyes showed good fastness properties on the substrates.

A Bioorthogonal-Activated Fluorescence Turn-On Probe Based on Nitrone-Modified 1,8-Naphthalimide for Live-Cell Imaging

A nitrone-modified 1,8-naphthalimide was desig ned as a novel bioorthog on alactivated turn-on probe based on strain-promoted alkyne-nitrone cycloadditio n(SPANC).The bioorthog onal cycloadducts were subseque ntly tran sformed into fluoresce nt rearra nge-ment products by photo-accelerati on,which exhibited sign ificant fluoresce nee enhan ceme nt,large stokes shift,and high fluores-cence qua ntum yield.DFT calculati ons were performed to elucidate the fluoresce nee OFF-ON mecha nism.This fluoroge nic strategy was successfully applied to labeling of proteins and visualizing mitochondria in live cells in real time.

Phthalimide and Naphthalimide end-Capped Diketopyrrolopyrrole for Organic Photovoltaic Applications

Two small molecules named PI-DPP and NI-DPP with a DPP core as the central strong acceptor unit and phthalimide/naphthalimide as the terminal weak acceptor were designed and synthesized. The effects of terminal phthalimide/naphthalimide units on the thermal behavior, optical and electrochemical properties, as well as the photovoltaic performance of these two materials were systematically studied. Cyclic voltammetry revealed that the lowest unoccupied molecular orbitals （LUMO） （- -3.6 eV） of both molecules were intermediate to common electron donor （P3HT） and acceptor （PCBM）. This indicated that PI-DPP and NI-DPP may uniquely serve as electron donor when blended with PCBM, and as electron acceptor when blended with P3HT, where sufficient driving forces between DPPs and PCBM, as well as between P3HT and DPPs should be created for exciton dissociation. Using as electron donor materials, PI-DPP and NI-DPP devices exhibited low power conversion efficiencies （PCEs） of 0.90% and 0.76% by blending with PCBM, respectively. And a preliminary evaluation of the potential of the NI-DPP as electron acceptor material was carried out using P3HT as a donor material, and P3HT：NI-DPP device showed a PCE of 0.6%, with an open circuit voltage （Voc） of 0.7 V, a short circuit current density （Jsc） of 1.91 mA·cm^-2, and a fill factor （FF） of 45%.

Naphthalimide as Highly Selective Fluorescent Sensor for Ag^＋ Ions

The naphthalimide derivative. NA1 was synthesized, which consists of a bis（2-（ethylthio）ethyl）amine group binding cations and naphthalimide unit as chromogenic and fluorogenic signaling subunit. Absorption and emission spectra and the effect of polarity of solvents and pH values were studied. The photo-induced electron transfer （PET） occurred from the donor of bis（2-（ethylthio）ethyl）amine group to the naphthalimide fluorophore. The present study demonstrates that NA1 is a viable candidate as a fluorescent receptor for a new Ag^＋ ion sensor. This silver ion chemosensor can discriminate Ag^＋ ion well among heavy metal ions by an enhancement of the fluorescence intensity in ethanol-water （1 ： 9, V ： V）. And NA1 is also a pH-sensor because the fluorescence of the compound varies with the pH values.

Naphthalimide and quinoline derivatives as inhibitors for insect N-acetyl-β-D-hexosaminidase

Insect chitinolyticβ-N-acetyl-D-hexosaminidase,such as OfHex1 from Ostrinia furnacalis,is a potential target for insecticide design.Among the known OfH ex1 inhibitors,Q2 is of great interest because it is the first non-carbohydrate inhibitor.In this study,we designed and synthesized a series of Q2 derivatives by replacing the thiadiazole and naphthalimide groups and changing the linker length.Compound 3 m showed the best inhibitory activity with a Kivalue of 0.34 mmol/L against OfHex1,which is about onequarter that of Q2(K_i=1.4 mmol/L).Compound 6 a showed the best inhibitory activity among the quinoline-containing derivatives(K_i=2.3 mmol/L).Molecular docking indicated that although 3 m,6 a,and Q2 binding the active pocket of OfHex1 in similar mode,compound 3 m engaged better than the other compounds in intermolecular interaction with OfH ex1.

Hoechst-naphthalimide dyad with dual emissions as specific and ratiometric sensor for nucleus DNA damage

A ratiometric fluorescent sensor（Hoe-NI） was developed by connecting a nucleus targeted Hoechst unit to a naphthalimide dye via ＂click chemistry＂. The sensor achieves high specific nucleus labeling with wash-free staining method in various kinds of living cells. The fluorescence ratio of the two emission bands（450 nm for Hoechst and 505 nm for naphthalimide） is changed sensitively to the variation of DNA concentrations, which provides the quantitative information in the processes of DNA damage induced by hydroxyl radicals and antitumor drug. Therefore, Hoe-NI is a recommendable sensor for the monitoring of nuclear DNA damage that reveals the health status of cells.

Study of Linear and Nonlinear Optical Properties of Four Derivatives of Substituted Aryl Hydrazones of 1,8-Naphthalimide

Four 1,8-naphthalimide hydrazone molecules with different electron-donating groups have been applied in the study of linear and nonlinear optical(NLO)properties.These compounds showed strong green emission in solution.Their NLO properties such as two-photon absorption(TPA)behavior with femtosecond laser pulses ca.800 nm and excited-state absorption(ESA)behavior with nanosecond laser pulses at 532 nm were investigated.Compound 4 presented the largest two-photon cross section(550 GM)among them due to two factors:the conjugated length of compound 4 is the longest and the electron-donating ability of compound 4 is the strongest.Different from TPA behavior,compound 2 showed the best nonlinear absorption properties at 532 nm and its nonlinear absorption coef-ficient and third-order nonlinear optical susceptibilitiesχ^(3)were up to 1.41×10^(−10) MKS and 4.65×10^(−12) esu,re-spectively.Through the modification of the structure,the nonlinear optical properties of these compounds at differ-ent wavelengths(532 and 800 nm)were well tuned.The great broad-band nonlinear optical properties indicate hy-drazones are good candidates for organic nonlinear optical absorption materials.