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Photoactivatable probe-based fluorescent imaging has become an efficient and attractive technique for spatiotemporal microscopic studies of biological events. However, almost all previously reported photoactivatable organic probes have been based on hydrosoluble precursors, which have produced water-soluble active fluorophores able to readily diffuse away from the photocleavage site, thereby dramatically reducing spatial resolution. Hydroxyphenylquinazolinone (HPQ), a small organic dye known for its classic luminescence mechanism through excited-state intramolecular proton transfer (ESIPT), shows strong light emission in the solid state, but no emission in solution. In this work, HPQ was employed as a precursor to develop a localizable, photoactivatable two-photon probe (PHPQ) for spatiotemporal bioimaging applications. After photocleavage, PHPQ releases a precipitating HPQ fluorophore which shows both one-photon and two-photon excited yellow-green fluorescence, thereby producing a localizable fluorescence signal that affords high spatial resolution for bioimaging, with more than 200-fold one-photon and 150-fold two-photon fluorescence enhancement. [ABSTRACT FROM AUTHOR]

A diversity-orientedone-pot synthesis of a series of membrane-permeableBF2-rigidified benz[c,d]indole N-heteroarene BBN and BBC dyes has beenachieved from the condensation of two commercial components (benz[c,d]indol-2-one and a set of N-heteroarene derivatives that can be selected from thousands of commerciallyavailable sources) and the subsequent in situ BF2complexationreaction. These dyes enjoy a set of excellent photophysical propertiesincluding the large Stokes shift, high solution and solid-state fluorescence,and excellent photostabilities. [ABSTRACT FROM AUTHOR]

Fluorescent proteins (FPs) of the green fluorescent protein family blink and bleach like all fluorophores. However, contrary to organic dyes, the mechanisms by which transient losses of fluorescence occur in FPs have received little attention. Here, we focus on the photoactivatable IrisFP, for which a transient non-fluorescent chromophoric state with distorted geometry was recently reported (Adam, V.; et al. J. Am. Chem. Soc.2009, 131, 18063). We investigated the chemical nature of this blinked state by employing quantum chemical/molecular mechanical calculations. Our findings suggest two previously unidentified dark states that display similar distorted chromophores with a transiently ruptured π-electron system. Both are protonated at atom Cα of the chromophore methylene bridge. Transient protonation may occur via proton transfer from the nearby Arg66 either in the triplet state T1 after intersystem crossing or in an anionic radical (doublet) ground state. As Arg66 is conserved in green-to-red photoconvertible FPs, these dark states are predicted to be common to all these proteins. We also suggest that Cα protonated dark states may accelerate photobleaching by favoring decarboxylation of the fully conserved Glu212. [ABSTRACT FROM AUTHOR]

Through a rational design, a novel Donor–Acceptor π-conjugated (D-π-A) blue fluorescent indenofluorene dye, DA-DSF-IF, has been synthesized for application in single-layer Small Molecule Organic Light Emitting Diodes (SMOLEDs). This new blue emitter possesses bipolar properties as well as good morphological and emission color stabilities and has been successfully used in a blue emitting single-layer SMOLED, with performances impressively magnified compared to a nonbipolar indenofluorene emitter. [ABSTRACT FROM AUTHOR]

Water-soluble BODIPY dyes have been readily obtained by introduction of phosphonate fragments either on the boron for the green and yellow emitting dyes or on the side chain for the red emitting dyes. Hydrolysis of the phosphonate is realized at the end of the reaction sequence and allows isolation of the targets by precipitation. All these novel dyes are soluble and fluorescent in water with quantum yields in the 23–59% range and emission wavelength spanning from 667 to 509 nm. [ABSTRACT FROM AUTHOR]

Organic laser dyes coumarin 1, coumarin 2, coumarin 102, coumarin 314, and coumarin 334 have been included in crystalline guanidinium organodisulfonate (GDS) host frameworks, forming stable inclusion compounds with lamellar architectures. The GDShosts consist of 2D quasihexagonal hydrogen-bonded sheets with topologically complementary guanidinium (G) ions and the sulfonate (S) moieties of a variety of organodisulfonates that serve as “pillars” that connect opposing GSsheets, thus generating inclusion cavities between the sheets. These host frameworks display a variety of architectural isomers, including the so-called bilayer, simple brick, zigzag brick as well as two heretofore unreported framework isomers: double zigzag brick and a “chevron” brick. These isomers vary with respect to the connectivity between opposing GSsheets and the corresponding shape of the inclusion cavities. The preference for the framework isomers reflects a systematic templating role for the guest molecules, largely based on their steric requirements. The coumarin guests exhibit a distinct arrangement in each host−guest combination, resulting in a range of fluorescence emission wavelengths that differ from that observed for the monomeric form in dilute solutions. For example, the bilayer framework, which has narrow 1D pores, enforces the alignment of coumarin guests as head-to-tail arrays resembling J-aggregates. The simple brick structure, however, has wider 1D channels that permit the formation of linear arrays of face-to-face coumarin dimers resembling H-aggregates. The coumarin guests in the zigzag brick architecture are confined within isolated inclusion cavities as face-to-face dimers. In general, the maxima of the emission bands of the coumarin dyes in the bilayer structure are blue-shifted, while those in the simple brick and zigzag brick structures are red-shifted. The fluorescence reflects the unique guest−guest packing in each framework isomer as well as interactions between the coumarin guest and the organodisulfonate pillar. The ability to include laser dyes in high concentrations in a robust host framework with regulation of intermolecular association between the dye molecules may lead to new solid-state lasing materials that overcome some of the barriers encountered for dyes embedded as dilute solutes in amorphous solid-state matrices such as polymers, zeolites, and sol−gel glasses. [ABSTRACT FROM AUTHOR]

The article discusses the syntheses and spectroscopic properties of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes and their derivatives. According to the authors, the dyes tend to be strongly ultraviolet-absorbing small molecules that emit relatively sharp fluorescence peaks with high quantum yields. They add that the dyes are relatively insensitive to the polarity and pH of their environment and are reasonably stable to physiological conditions.

An organic dye, SAMSA, bound to gold nanoparticles, displays random photoactivated fluorescence blinking whose rate depends on the size of the nanoparticles. We report experiments indicating that (1) the dye emission wavelength is red-shifted (10−30 nm) by applying an external low voltage (1−10 V) and that (2) the fluorescence emission of single dyes can be resonantly driven by tuning the alternating external bias frequency from 1 to 3 Hz, depending on the nanoparticle size. These properties appear highly valuable and promising for devising light emitting nanostructures. [ABSTRACT FROM AUTHOR]

The article presents a study which proposes the first molecular system that demonstrates the feasibility of altering the fluorescence properties of an organic dye as a function of radionuclide decay. The study found a clear differentiation in fluorescence between Cu2+ and its decay products. According to the researchers, the new molecular construct and mechanism could be used to develop visible radioactivity decay devices for environmental and nuclear forensic applications.

The article demonstrates the optical properties of mixtures of quantum dots (QDs) and compares the results to fluorescent organic dyes. It is noted that the solutions of mixtures of QDs of different sizes produce colors that are the sum of the fluorescence wavelenghts of the individual QD components. To further understand why mixtures of quantum dots and organic dyes have different appearances, optical properties of both quantom dots and organic dyes are measured using absorption and fluorescence emission spectroscopy.