Realization of nitroaromatic chromophores with intense two-photon brightness.

Strong fluorescence is a general feature of dipyrrolonaphthyridinediones bearing two nitrophenyl substituents. Methyl groups simultaneously being weakly electron-donating and inducing steric hindrance appear to be a key structural parameter that allows for significant emission enhancement, whereas EtN groups cause fluorescence quenching. The magnitude of two-photon absorption increases if 4-nitrophenyl substituents are present while the contribution of EtN groups is detrimental.

Photophysics, Electrochemistry and Efficient Electrochemiluminescence of Trigonal Truxene-Core Dyes.

We synthesized and characterized a series of dyes built from a spirofluorene or truxene core. The quadrupolar spirofluorene system is the initial building unit for the design and preparation of more complex star-shaped dyes consisting of a truxene core bearing three di- or triphenylamine moieties with or without a thiophene connector. Their photophysical, electrochemical, and electrochemiluminescence (ECL) properties were first investigated in solution.

Multimodal optical contrast agents as new tools for monitoring and tuning nanoemulsion internalisation into cancer cells. From live cell imaging to imaging of tumours.

Tailor-made NIR emitting dyes were designed as multimodal optical probes. These asymmetric amphiphilic compounds show combined intense absorption in the visible region, NIR fluorescence emission, high two-photon absorption in the NIR (with the maximum located around 1000 nm) as well as large Stokes' shift values and second-harmonic generation ability. Thanks to their structure, high loading into nanoemulsions (NEs) could be achieved leading to very high one- and two-photon brightness.

Hydrophilic Fluorescent Nanoprodrug of Paclitaxel for Glioblastoma Chemotherapy.

Highly water-soluble, nontoxic organic nanoparticles on which paclitaxel (PTX), a hydrophobic anticancer drug, has been covalently bound via an ester linkage (4.5% of total weight) have been prepared for the treatment of glioblastoma. These soft fluorescent organic nanoparticles (FONPs), obtained from citric acid and diethylenetriamine by microwave-assisted condensation, show suitable size (Ø = 17-30 nm), remarkable solubility in water, softness as well as strong blue fluorescence in an aqueous environment that are fully retained in cell culture medium.

Modified Isoindolediones as Bright Fluorescent Probes for Cell and Tissue Imaging.

New L-shaped fluorophores possessing five conjugated rings have been synthesized through a four-step procedure involving diketopyrrolopyrrole synthesis and its double N-alkylation, followed by trimethylsilyl bromide-mediated rearrangement to thieno[2,3-f]isoindole-5,8-dione and an intramolecular Friedel-Crafts reaction. In comparison with the parent isoindolediones and π-expanded diketopyrrolopyrroles, these new dyes show red-shifted absorption and emission (up to ≈630 nm). Their structural rigidity is responsible for both the observed small Stokes shifts and large fluorescence quantum yields.

Dual-wavelength efficient two-photon photorelease of glycine by π-extended dipolar coumarins.

Photolabile protecting groups (PPGs) releasing bioactive compounds upon two-photon excitation have emerged as increasingly popular tools to control and study physiological processes. Yet the limited two-photon photosensitivity of many cages is still a critical issue for applications. We herein report the design, synthesis and photophysical study of polarized extended coumarinyl derivatives which show large two-photon sensitivity (up to 440 GM) at two complementary wavelengths in the NIR spectral range.

Synthesis of Bis(arylethynyl)pyrrolo[3,2-b]pyrroles and Effect of Intramolecular Charge Transfer on Their Photophysical Behavior.

3,6-Bis(arylethynyl)pyrrolo[3,2-b]pyrroles were synthesized through a two-step procedure involving double direct alkynylation of the electron-rich core followed by Sonogashira coupling. In comparison with the parent tetraarylo-pyrrolo[3,2-b]pyrroles and benzo-fused pyrrolopyrroles, these new dyes showed moderately redshifted absorption. Almost all derivatives showed positive fluorescence solvatochromism and, for the first time, red-emitting pyrrolopyrroles were obtained.

Quinoline-Derived Two-Photon Sensitive Quadrupolar Probes.

Quadrupolar probes derived from 8-dimethylamino-quinoline (8-DMAQ) having a pegylated fluorene core were prepared and studied under "one-photon" (λ=365 nm) and "two-photon" (TP) (λ=730 nm) irradiation conditions. Compound 1 a was identified as the most efficient probe by UV activation that showed sequential release of acetic acid as a model. Although the probe showed high two-photon absorption it stayed inert under femtosecond irradiation conditions.

Fluorescent periodic mesoporous organosilica nanoparticles dual-functionalized via click chemistry for two-photon photodynamic therapy in cells.

The synthesis of ethenylene-based periodic mesoporous organosilica nanoparticles for two-photon imaging and photodynamic therapy of breast cancer cells is described. A dedicated two-photon absorbing fluorophore possessing four triethoxysilyl groups and having large two-photon absorption in the near IR region, and azidopropyltriethoxysilane were incorporated into the structure. The mesoporous nanoparticles of 100 nm diameter were further functionalized by means of click chemistry with a propargylated fluorescent bromo-quinoline photosensitizer able to generate singlet oxygen.

Z-Shaped Pyrrolo[3,2-b]pyrroles and Their Transformation into π-Expanded Indolo[3,2-b]indoles.

Sterically hindered 1,4-dihydropyrrolo[3,2-b]pyrroles possessing ortho-(arylethynyl)phenyl substituents at positions-2 and -5 were efficiently synthesized through a sila-Sonogashira reaction. These unique Z-shaped dyes showed relatively strong fluorescence in solution. Detailed optimization revealed that, in the presence of InCl3, these alkynes readily undergo an intramolecular double cyclization to give hexacyclic products bearing an indolo[3,2-b]indole skeleton in remarkable yields.

pKa tuning in quadrupolar-type two-photon ratiometric fluorescent membrane probes.

Two bolaamphiphilic quadrupoles built from a fluorene core conjugated with azine endgroups were designed and successfully used to stain GUV membranes. Their quadrupolar character induces both a shift of the pKa values close to the physiological pH and large two-photon absorption responses (i.e.

Strong solvent dependence of linear and non-linear optical properties of donor-acceptor type pyrrolo[3,2-b]pyrroles.

We describe the design, synthesis, and fluorescent profile of two environment-sensitive dyes in which an electron-donating group is conjugated to an electron-accepting unit via a pyrrolo[3,2-b]pyrrole ring system. The maximum emission wavelength (λem) of these donor-donor-acceptor (D-D-A) pyrrolo[3,2-b]pyrroles was found to be very sensitive to the environment (a bathochromic shift of about 100 nm in polar solvents). The longer emission wavelength in polar aprotic as well as hydrophilic solvents compared with that in low-polarity hydrophobic solvents was due to an ICT character of the excited state.

Tandem triad systems based on FRET for two-photon induced release of glutamate.

Tandem systems allowing enhanced two-photon (2P) absorption in a wavelength range permitting coupling of the primary excitation by energy transfer to an intramolecular cage known to have fragmentation properties suited to photolysis in neuroscience is demonstrated to lead to a 10-fold improvement in the 2P photolysis cross-section at experimentally compatible wavelengths.

Fluorescence and two-photon absorption of push-pull aryl(bi)thiophenes: structure-property relationships.

Photophysical and TPA properties of series of push-pull aryl(bi)thiophene chromophores bearing electron-donating (D) and electron-withdrawing (A) end-groups of increasing strength are presented. All compounds show an intense intramolecular charge transfer (ICT) absorption band in the visible region. Increasing the D and/or A strength as well as the length of the conjugated path induces bathochromic and hyperchromic shifts of the absorption band as reported for analogous push-pull polyenes.