Novel fluorescent strigolactone derivatives that contain the piperidine-substituted 1,8-naphthalimide ring system connected through an ether link to a bioactive 3-methyl-furan-2-one unit were ...synthesized and their spectroscopic properties investigated. The solvatochromic behavior of these piperidine-naphthalimides was monitored in solvents of different polarity using the electronic absorption and fluorescence spectra. These compounds exhibited a strong positive solvatochromism taking into account the change of solvent polarity, and the response mechanism was analyzed by fluorescence lifetime measurements. According to Catalan and f(n), f(ε), β, α solvent scales, the dipolarity and polarizability are relevant to describe the solute-solvent interactions. The emission chemosensing activity was discussed in order to determine the water content in organic environments. The emission intensity of these compounds decreased rapidly in dioxane, increasing water level up to 10%. Measuring of quantum yield indicated that the highest values of quantum efficiency were obtained in nonpolar solvents, while in polar solvents these derivatives revealed the lowest quantum yield. The fluorescence decay can be described by a monoexponential model for low water levels, and for higher water contents a biexponential model was valid.
Strigolactones (SLs) have potential to be used in sustainable agriculture to mitigate various stresses that plants have to deal with. The natural SLs, as well as the synthetic analogs, are difficult ...to obtain in sufficient amounts for practical applications. At the same time, fluorescent SLs would be useful for the mechanistic understanding of their effects based on bio-imaging or spectroscopic techniques. In this study, new fluorescent SL mimics containing a substituted 1,8-naphthalimide ring system connected through an ether link to a bioactive furan-2-one moiety were prepared. The structural, spectroscopic, and biological activity of the new SL mimics on phytopathogens were investigated and compared with previously synthetized fluorescent SL mimics. The chemical group at the C-6 position of the naphthalimide ring influences the fluorescence parameters. All SL mimics showed effects similar to GR24 on phytopathogens, indicating their suitability for practical applications. The pattern of the biological activity depended on the fungal species, SL mimic and concentration, and hyphal order. This dependence is probably related to the specificity of each fungal receptor-SL mimic interaction, which will have to be analyzed in-depth. Based on the biological properties and spectroscopic particularities, one SL mimic could be a good candidate for microscopic and spectroscopic investigations.
Three novel triphenylamine-based compounds containing strong electron acceptor groups have been synthesized and their comparative photophysical properties are presented. These compounds were obtained ...by a two-step method: (i) triphenylamine compounds with one, two and three phenylacetylene arms were synthesized by Sonogashira reaction between iodine-substituted triphenylamines and phenylacetylene, followed by (ii) post-modification of these electron-rich alkynes by addition of the strong electron acceptor, tetracyanoethylene. Characterization of all oligomers was made by FTIR, 1H-NMR, UV–vis and fluorescence spectroscopy. A batochromic shifting of the UV and photoluminescence maxima was observed with the increase of the acceptor group number. The electrochemical behavior was studied by cyclic voltammetry. The cyclic voltammograms have evidenced that triphenylamine-phenylacetylene compounds undergo only oxidation processes while compounds modified with tetracyanoethylene show both oxidation and reduction peaks associated with donor and acceptor groups, respectively. The donor–acceptor compounds coordinate metal ions (i.e., Hg2+ and Sn2+) by cyano groups resulting in the decreasing of charge transfer band intensity, and they can be used as chemosensors.
•Three triphenylamine-based ethynylene compounds were prepared by Sonogashira reaction.•Post-modification of ethynylene linkages by tetracyanethylene cycloaddition and retroconversion led to donor–acceptor compounds.•Photophysical properties of donor–acceptor oligomers were studied in different solvents.
Display omitted
► New telechelic or side-functionalized oligodiorganosiloxanes with aminopropyl groups were prepared. ► Aminopropyl groups attached to the siloxane were converted in ferrocenylimine ...ones. ► Iron spin state, electrochemical behavior and solvent effect were investigated by 57Fe Mossbauer spectroscopy, cyclic voltammetry, and UV–Vis absorption spectroscopy, respectively.
Formyl-ferrocene, FFc, was prepared and used as agent to attach ferrocenyl moiety to siloxanes through imine group. Thus, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, L1, α,ω-bis(3-aminopropyldimethylsiloxy)oligodiphenylsiloxane, L2, and polydimethyl-methyl(3-aminopropyl)siloxane, L3 (the last two prepared by us) were converted in the corresponding azomethine derivatives: 1,3-bis(3-ferrocenyliminepropyl)tetramethyldisiloxane, L1Fc, α,ω-bis(ferrocenyliminepropyldimethylsiloxy)oligodiphenylsiloxane, L2Fc, and polydimethyl-methyl(3-ferrocenyliminopropyl)siloxane, L3Fc. The iron spin state was determined by Mossbauer spectroscopy, emphasizing the presence of mixed-valence iron of interest for molecular electronics. Cyclic voltammograms of the compounds, both in solution and as films deposited on glassy carbon electrodes, showed quasi-reversible oxidation/reduction waves making them suitable for sensing applications. The solvent effect was studied by UV–Vis spectra.
Some luminophores cannot fluoresce from dilute solution, especially those that are highly flexible. By aggregation, the rigidity of these molecules increases allowing for photoluminescence. However, ...the enhanced rigidity and the intermolecular interactions can give rise to several high-energy excited states, and since they can fluoresce only from the lowest energy excited state, known as the Kasha rule, the energy surplus is lost to the surroundings. In the pursuit of developing efficient light harvesting strategies from the higher energy excited states, it is necessary to look upon the effects not only at the level of nanometric molecules themselves but also of their supramolecular assemblies. Herein, we pinpoint the impact of poor conjugated moieties over the chromophore units, as well as the optical phenomena emerging at the supramolecular level. The molecular design consists of the S-alkylation of 5-amino-1,3,4-thiadiazole-2-thiol with permethylated silicone or hydrocarbons. The synthesized compounds display excited state intermolecular proton transfer (pseudo-ESIPT), blue and green fluorescence, and near-infrared phosphorescence at room temperature.
Display omitted
•The ability of curbit7uril to bind the EDOT afforded the synthesis of PEDOT∙CB7 PS’s and EDOT∙CB7 PR’s water-stable dispersions.•PEDOT∙CB7 PR exhibited higher quantum yield and ...emission lifetimes than those of EDOT∙CB7 PS.•The extended conjugation and π-π interactions of PEDOT∙CB7 PR provided improved electrical conductivity.
While poly(3,4-ethylenedioxythiophene) is known as an interesting material for optoelectronic applications, it still lacks several characteristics and needs further improvements. Within this paper, after we succeeded in making it water-soluble through encapsulation of 3,4-ethylenedioxythiophene units by cucurbit7uril (CB7), the resulting poly(3,4-ethylenedioxythiophene/cucurbit7uril) polypseudorotaxane (PEDOT∙CB7 PS) and polyrotaxane (PEDOT∙CB7 PR) were in-depth investigated regarding their electro-optical properties, as well as their aggregation behavior. Foremost, the DLS and TEM analyses clearly indicated that the polymers form stable dispersions in water. Surprisingly, the studied polymers exhibited fluorescence (FL) and phosphorescence (Ph) in acetonitrile (ACN), but switching to water their Ph was quenched and quantum efficiency (Φ) drastically lowered. The insertion of pyrene (Py) end-capping moiety within PEDOT∙CB7 PR turned out to increase both the ΦPh and emission lifetimes (τ). Despite both compounds being semiconductors, the Py end-capping increases the conductivity, probably due to homogenously packing through π-π interactions and extended conjugation. Herein, we bring to attention new perspectives on the spectroscopic characteristics of these emissive supramolecular materials with a wide range of applications in optoelectronics.
Some indolizines with phenanthroline skeleton derivatives have been investigated using steady state absorption, emission and time resolved fluorescence techniques. The effects of the substituents on ...the electronic absorption spectra and fluorescence emission have been demonstrated. The fluorescence decay curves exhibit one or two decay times. The emission lifetime measurements revealed values of 3–5 ns under the excitation with 370 nm. The quantum yield was also determined. The quenching process of emission using picric acid as quencher was characterized by Stern-Volmer plots. The phenanthroline derivatives 2 and 5 possess high efficiency for the detection of picric acid.
Two groups of new naphthalene-1,8-dicarboxylic acid derived compounds, 6-amino-1,8-naphthalic anhydride derivatives and 2-hydroxy-6-amino-1,8-naphthalimide derivatives, have been synthesized and ...characterized. The spectroscopic properties of all synthesized compounds were investigated in order to be used in the field of bio-imaging studies and as intermediates for the preparation of new fluorescent bioactive compounds. Positive solvatochromism was observed from non-polar to polar solvents and it was discussed using Catalan multilinear regression analysis. Comparative study of the photophysical characteristics of naphthalic anhydride and 1,8-naphthalimide derivatives was performed. The new naphthalic anhydride 6-(4-benzyl-piperazin-1-yl)benzodeisochromene-1,3-dione (3) presents the highest value of fluorescence quantum yield in solvents with lower polarities. The results demonstrate that the quantum yields values of naphthalic anhydride derivatives are higher than those of naphthalimide derivatives.
Display omitted
•Novel 1,8-naphthalic anhydride and 1,8-naphthalimide derivatives have been synthesized.•Multinuclear NMR chemical shift assignments•Application of Catalan and Laurence solvatochromic models•Substituent impact on the photophysical properties of naphthalene-1,8-dicarboxylic acid derivatives•The presence of piperidine moiety leads to high fluorescence in solution
Six new fused isoquinoline based compounds (compounds 5a–c with pyrrolo2,1-a isoquinoline structure and compounds 6a–c with imidazo2,1-aisoquinoline skeleton) have been synthesized using the 3 + 2 ...cycloaddition of the several in situ generated cycloimmonium ylides to ethyl propiolate or ethyl cyanoformate. All the synthesized compounds have been investigated in solution by UV–VIS absorption, steady and time-resolved fluorescence methods. The effect of the substituents on the spectral characteristics has been demonstrated. These derivatives displayed an intense emission between 360 and 420 nm. The emission quantum yields (Φ = 0.54–0.64) of pyrroloisoquinoline derivatives in dimethylsulfoxide (DMSO) were significantly higher than those of imidazoquinolines (0.03–0.16). The fluorescence decay of isoquinoline derivatives follows a biexponential law. A noticeable response of these isoquinoline derivatives to sodium hydroxide was observed.
Display omitted
•New pyrrolo- and imidazoisoquinolines have been synthesized.•The pyrroloisoquinoline derivatives possess high values of fluorescence quantum yield.•The examined products demonstrated high sensitivity to medium basicity.
The photoexcited processes in two compounds belonging to the salicylidene-p-X-anilines family were investigated by time resolved absorption and emission spectroscopy in the femto-to-millisecond time ...domain. The studies were conducted in two solutions of different polarity and were supplemented by investigations in solid state (microcrystalline powder). In the polar solvent, both compounds share similar fluorescence properties. In the non-polar solvent, one of the compounds exhibits only the tautomeric emission, while for the other compound, the fluorescence is almost quenched, but still visible as a co-existence of the normal and tautomeric emissions. These different emission characteristics in a non-polar solvent were correlated with the aggregate formation. From femto– to miliseconds, various deactivation channels and conformers of the known tautomeric forms have been evidenced altogether with an additional fluorescence relaxation appearing only in molecular aggregates. A complete and detailed image of the photochromic cycles emerges by correlating structural dynamics with the experimentally observed kinetic and spectroscopic parameters over 10 orders of magnitude time-scale.
•The photophysical properties two Schiff bases have been studied by time resolved spectroscopy.•The photochromic cycles and the de-activation mechanism of excited states were drawn.•An additional fluorescence relaxation appears only in molecular aggregates.•Two simultaneous processes take place in excited state: E-enol → Z-enol isomerization and the very fast proton transfer.
PDF
