Unusual large Stokes shift and solvatochromic fluorophore: Synthesis, spectra, and solvent effect of 6-substituted 2,3-naphthalimide

Practical access to fluorescent 2,3-naphthalimide derivatives via didehydro-Diels-Alder reaction

A practical and efficient approach for the synthesis of fluorescent 2,3-naphthalimide derivatives has been developed from readily available starting materials via an intramolecular didehydro-Diels-Alder reaction, which proceeded well under room temperature, exhibiting a wide substrate scope and good functional group tolerance. The practicability of this methodology has been verified by one-step synthesis of the environmentally sensitive fluorophore 6-DMN on a gram scale with a shorter time, fewer steps and less waste disposal, and without the utilization of toxic transition metals. The present experimental and computational studies support the crucial role of the propiolimide moiety in the transformation.

Single-Atom Switching as a General Approach to Designing Colorimetric and Fluorogenic Probes for Mercury Ions

By performing a single-atom replacement within common fluorophores, we have developed a facile and general strategy to prepare a broad-spectrum class of colorimetric and fluorogenic probes for the selective detection of mercury ions in aqueous environments. Thionation of carbonyl groups from existing fluorophore cores results in a great reduction of fluorescence quantum yield and loss of fluorescence emission. The resulting thiocaged probes are efficiently desulfurized to their oxo derivatives in the presence of mercury ions, leading to pronounced changes in chromogenic and fluorogenic signals. Because these probes exhibit high selectivity, excellent sensitivity, good membrane-permeability, and rapid responses towards mercury ions, they are suitable for visualization of mercury in both aqueous and intracellular environments.

Disproportionation-induced solid-state fluorescence in 6,13-dihydropentacenes

The thermally and photolytically induced disproportionation of 6,13-dihydropentacene derivatives into tetrahydropentacenes and pentacenes results in unique solid-state fluorescence. The fluorescence thereby depends on the molecular structure and the molecular arrangement in the solid state.

The thermally and photolytically induced disproportionation of 6,13-dihydropentacene derivatives into tetrahydropentacenes and pentacenes results in unique solid-state fluorescence.

Reversible mechanofluorochromism of aniline-terminated phenylene ethynylenes

Seven three-ring phenylene-ethynylene (PE) structural analogs, differing only in the lengths of alkyl chains on terminal aniline substituents, show 50-62 nm bathochromic shifts in emission maxima in response to mechanical force (mechanofluorochromism, MC). These shifts are fully reversible with heat or solvent fuming. Shearing of these solids yields a transition from green-emitting crystalline phases to orange-emitting amorphous phases as established by differential scanning calorimetry and X-ray diffraction. Molecules with shorter alkyl chain lengths required higher temperatures to recover the hypsochromically shifted crystalline phases after grinding, while the recovery with chain lengths longer than butyl occurred at room temperature. In addition to this structure-dependent thermochromism, these compounds retain their MC properties in polymer hosts to various extents. The crystalline phases of these materials have PE chromophores that are twisted due to non-covalent perfluoroarene-arene (ArF-ArH) interactions involving perfluorophenyl pendants and the terminal rings of the PE chromophore, resulting in interrupted conjugation and an absence of chromophore aggregation. The MC behavior of an analog without the perfluoroarene rings is severely attenuated. This work demonstrates the general utility of twisted PEs as stimuli-responsive moieties and reveals clear structure-property relationships regarding the effects of alkyl chain length on these materials.

One-pot syntheses of blue-luminescent 4-aryl-1H-benzo[f]isoindole-1,3(2H)-diones by T3P® activation of 3-arylpropiolic acids

In situ activation of 3-arylpropiolic acids with T3P^® (n-propylphosphonic acid anhydride) initiates a domino reaction furnishing 4-arylnaphtho[2,3-c]furan-1,3-diones in excellent yields. Upon employing these anhydrides as reactive intermediates blue-luminescent 4-aryl-1H-benzo[f]isoindole-1,3(2H)-diones are formed by consecutive pseudo three-component syntheses in a one-pot fashion. The Stokes shifts correlate excellently with the Hammett-Taft σ_R parameter indicating an extended degree of resonance stabilization in the vibrationally relaxed excited singlet state.

Ratiometric fluorescence imaging of endogenous selenocysteine in cancer cell matrix

A ratiometric method for tracing the variation of selenocysteine (Sec) in a cell matrix was provided. This was constructed by the quantitative correlation between the fluorescence ratio ofRat-Sec(blue emission, the probe) andNap-OH(green-yellow emission, the product from a Sec-specific reaction) and the concentration of Sec.

Far-Red Fluorescent Lipid-Polymer Probes for an Efficient Labeling of Enveloped Viruses

Far-red emitting fluorescent lipid probes are desirable to label enveloped viruses, for their efficient tracking by optical microscopy inside autofluorescent cells. Most used probes are rapidly released from membranes, leading to fluorescence signal decay and loss of contrast. Here, water-soluble lipid-polymer probes are synthesized harboring hydrophilic or hydrophobic far-red emitting dyes, and exhibiting enhanced brightness. They efficiently label Hepatitis C Virus pseudotyped particles (HCVpp), more stably and reproducibly than commercial probes, and a strong fluorescence signal is observed with a high contrast. Labeling with such probes do not alter virion morphology, integrity, nor infectivity. Finally, it is shown by fluorescence microscopy that these probes enable efficient tracking of labeled HCVpp inside hepatocarcinoma cells used as model hepatocytes, in spite of their autofluorescence up to 700 nm. These novel fluorescent lipid-polymer probes should therefore enable a better characterization of early stages of infection of autofluorescent cells by enveloped viruses.

Synthesis of ester-substituted dihydroacridine derivatives and their spectroscopic properties

Ester substituted dihydroacridine derivatives exhibit a noticeable fluorescence solvatochromism.

Solvent-induced multicolour fluorescence of amino-substituted 2,3-naphthalimides studied by fluorescence and transient absorption measurements

Amino-substituted 2,3-naphthalimide derivatives showed marked positive solvatofluorochromism, and the fluorescence emission was effectively quenched in methanol via the internal conversion process.

A ratiometric fluorescent probe for detection of biogenic primary amines with nanomolar sensitivity

An ultrasensitive ratiometric fluorescent sensor made of an N,N-dimethylaminonaphthalene anhydride moiety for detection of aliphatic primary amines is reported.

Luminescent probes for the bioimaging of small anionic species in vitro and in vivo

This comprehensive review examines recent developments in the use of fluorescent/luminescent probes for the bioimaging of anionic species. Images in cover art reproduced with permission from ref. 290 and 306.

Highly Solvatochromic 7-Aryl-3-hydroxychromones

Introduction of the dialkylaminophenyl group in position 7 of 3-hydroxychromone changes the orientation of the excited-state dipole moment and leads to superior solvatochromic properties (>170 nm emission shift in aprotic media). The excited-state intramolecular proton-transfer (ESIPT) reaction of 7-aryl-3-hydroxychromones is almost completely inhibited in most solvents. Methylation of the 3-OH abolishes ESIPT completely and also leads to improved photostability. The probes exhibit a ∼100-fold increase in fluorescence intensity and large Stokes shifts upon binding to membranes, reflecting differences in membrane phase and charge by a >40 nm spread in the emission band position.

A new Schiff base based on vanillin and naphthalimide as a fluorescent probe for Ag+ in aqueous solution

A new Schiff base based on vanillin and naphthalimide was designed and synthesized as fluorescent probe. The probe showed high selectivity for Ag(+) over other metal ions such as Pb(2+), Na(+), K(+), Cd(2+), Ba(2+), Cr(3+), Zn(2+), Cu(2+), Ni(2+), Ca(2+), Al(3+) and Mg(2+) in aqueous solution. A new fluorescence emission was observed at 682 nm in the presence of Ag(+) ion. The fluorescence intensity quenched with increasing the concentration of Ag(+) at 682 nm. The method of job's plot confirmed the 1:2 complex between Ag(+) and probe, and the mechanism was proposed.