A FRET-based ultraviolet to near-infrared frequency converter

The synthesis and photophysical characterization of a generation 1 dendrimer containing four coumarin 2 laser dyes at the periphery and a perylenebis(dicarboximide) derivative at the core are described. It was found that 99% of the UV light absorbed by the peripheral coumarin 2 donor chromophores is transferred through fluorescence resonance energy transfer (FRET) to the core acceptor. Emission from the core via FRET is observed in the near-infrared with a 6.2-fold amplification relative to direct excitation.     

Simultaneous light emission from a mixture of dendrimer encapsulated chromophores: a model for single-layer multichromophoric organic light-emitting diodes

The site isolation of two dyes capable of electronic interaction via Forster energy transfer has been studied with the two dyes coumarin 343 and pentathiophene encapsulated by dendrons containing both solubilizing and electroactive moieties. Photoluminescence studies of mixtures of the dendritic dyes show that at high dendron generation, significant site isolation is achieved with relative emission characteristics influenced by both the degree of site isolation and the emission quantum yield of the dyes. Electroluminescence studies carried out in organic light emitting diode devices confirm that color tuning may be achieved by mixing the two encapsulated dyes in a single layer. However, selective carrier trapping by one of the core component dyes can dramatically influence the effectiveness of other components in the device.     

Local environments of coumarin dyes within mesostructured silica-surfactant nanocomposites

The local environments surrounding dye molecules were studied with use of coumarin dyes in a mesostructured silica-surfactant nanocomposite, which was formed in a porous alumina membrane by a surfactant-templated method and has an average pore diameter of 3.4 nm. Coumarin dyes, such as coumarin 480 (C480), coumarin 343 (C343), and propylamide coumarin 343 (PAC343), were extracted into the silica-surfactant nanocomposite and time-resolved fluorescence spectra of these dyes were examined. C480 and C343 show slow dynamic Stokes shifts and the decay curve can be fitted by a biexponential function. The decay-time constants obtained from the fitting are almost identical for C480 and C343: 0.87 and 7.5 ns for C480, and 0.86 and 7.6 ns for C343. In contrast to these two coumarin dyes, short decay-time constants (0.50 and 4.8 ns) were obtained for PAC343 in the silica-surfactant nanocomposite. These results indicate that the local environments of C480 and C343 are almost identical but different from that of PAC343. By considering the origin of the dynamic Stokes shift and the mesostructure of the silica-surfactant nanocomposite, the location and microenvironment of coumarin dyes within the silica-surfactant nanocomposite are discussed.     

Effect of anisotropic and isotropic solvent on the dipole moment of coumarin dyes

The ground state (μ(g)) and the excited state (μ(e)) dipole moments of two coumarin laser dyes, coumarin 440 and 460, were studied at room temperature in various solvents, viz., general solvents, alcohols and liquid crystals at 298 K. In this work, we report dipole moment of laser dyes in different anisotropic (liquid crystal) and isotropic environments for understanding the effects of environments on the molecular dipole moment and comparing them. Ground and excited state dipole moments of coumarin dyes were evaluated by means of solvatochromic shift method. It was observed that dipole moment values of excited states (μ(e)) were higher than the corresponding ground state values (μ(g)) in all media.     

Synthesis of phosphacoumarins and phosphonocoumarins. Two new classes of fluorescent dyes

The synthesis of two new classes of phosphorous-containing coumarin dyes is described and their fluorescent properties are compared with those of known coumarin dyes.     

Functionally layered dendrimers: a new building block and its application to the synthesis of multichromophoric light-harvesting systems

[reaction: see text] A divergent synthesis of internally functionalized dendrimers based on a modular functional monomer has been developed. This strategy was applied to the construction of a light-harvesting dendrimer containing one set of naphthopyranone dyes located at the interior and another set of coumarin chromophores located in the adjacent outer layer surrounding a porphyrin acceptor. Quantitative energy transfer from both donor pigments is observed, giving rise to exclusive emission from the porphyrin core over all excitation wavelengths.     

Host-Guest Interactions and Laser Activity in AlPO4-5/Laser Dye Composites

In situ inclusion of the laser dyes coumarin 466, coumarin 7, pyridine 2 and DCM has been conducted successfully in AlPO₄-5 crystals. The charged molecule pyridine 2 interacts with the framework and leads to bundle-like morphologies with increasing dye content. Uncharged molecules (DCM, coumarin 7, coumarin 466) are included, although corresponding molecular dimensions are exceeding pore size. These dyes probably induce local defects in the pore walls of AlPO₄-5 which are healed during crystal growth leading to well-developed hexagonal prisms. Spectroscopic studies show interactions of the dyes with the solid-state matrix which are reflected by shifts of absorption and emission maxima of the dyes. For the first time, laser activity is demonstrated on a perfect hexagonal single AlPO₄-5/DCM crystal.     

Azole-linked coumarin dyes as fluorescence probes of domain-forming polymers.

The binding of 7-aminocoumarins, substituted in the 3-position with heterocyclic benzimidazole or benzothiazole groups by domain-forming polymers in water has been studied. The acrylic polyelectrolyte, poly(methacrylic) acid (PMAA) was used as a solubilizing agent for coumarin dyes 6, 7, and 30 in water. The acid-base properties of these bound coumarin dyes were monitored spectroscopically on titration of aqueous solutions. Alterations in the fluorescence wavelength and intensity, quantum yields, lifetimes, and polarization are consistent with the preferential binding of the dyes in compact hydrophobic domains that form at a pH regime in which the polymer is in its protonated (uncharged) state. In this pH range (<4.0), coumarins 7 and 30 are bound as monocations, whereas coumarin 6 remains in its neutral form. Reduced quantum yields and lifetimes of fluorescence for cationic coumarins can be understood in terms of the imposition of a low-lying electron transfer state, an example of a twisted intramolecular charge transfer (TICT) intermediate. Effects of polymer microenvironment on the rate of TICT state decay (a reverse electron transfer) are observed. Coumarins of the azole type may find use as fluoroprobes of the microenvironments of proteins and other biological macromolecules and as agents for pH sensing.     

Ultrafast electron transfer in a nanocavity. dimethylaniline to coumarin dyes in hydroxypropyl gamma-cyclodextrin

Photoinduced electron transfer (PET) from N,N-dimethylaniline (DMA) to four coumarin dyes (C151, C481, C153, and C480) inside the cavity of hydroxypropyl gamma-cyclodextrin (hpCD) is studied using femtosecond upconversion. The rate of PET is found to be nonexponential and to vary significantly with the coumarin dyes. The rate for C481 is 100 times faster than that for C480. The PET rate displays a bell-shaped dependence on the free energy change and thus reveals a Marcus-type inverted region. The anisotropy decay of the four dyes in hpCD are found to be very similar, and hence the observed variation in the rate of PET is not due to variation in rotational diffusion of the acceptors (coumarin dyes).     

Systematic study of the fluorescence decays of amino‐coumarin dyes in polymer matrices

We measured the fluorescence decays of seven different amino‐coumarin dyes in polymer films of poly(methyl methacrylate) (PMMA), poly(styrene) (PS), and ethylene‐butene rubber (EBR); as well as in the small molecule analogs ethyl acetate and toluene. Many of the dye‐solvent and dye‐polymer combinations exhibited single exponential decays with lifetimes ranging from 2.3 to 3.9 ns. Small deviations from single exponential behavior occurred for most of the dyes in EBR. Significant deviations from single exponential behavior occurred for 7‐(diethylamino)‐2‐oxo‐2H‐1‐benzopyran‐3‐carboxylic acid (coumarin‐3) in ethyl acetate and in all polymer matrices and 2,3,6,7‐tetrahydro‐11‐oxo‐1H,5H,11H‐[1]benzopyrano[6,7,8‐ij]quinolizin‐10‐carboxylic acid (coumarin‐343) in all of the polymer matrices. Time‐resolved fluorescence spectra indicated the presence of two different excited states for coumarin‐3 and coumarin‐343 in PMMA; these spectra were qualitatively different from the time‐resolved spectra of coumarin‐3 in ethyl acetate. We rationalize these results in terms of the chemical functionalities of the various dyes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2333–2343, 2007     

有机染料及其在染料敏化太阳电池中的应用

在染料敏化太阳电池中,染料敏化剂分成无机染料与有机染料两大类。无机染料受稀有金属钌的制约而成本较高,开发有机染料是降低染料敏化太阳电池成本的有效手段,成为目前研究的热点。本文从有机染料敏化剂的分子设计入手,简述了染料敏化太阳电池中有机染料敏化剂的基本结构,将有机染料敏化剂分为吲哚啉类染料、香豆素类染料、三苯胺类染料、菁...     

Synthesis,Absorption Spectra Studies and Biological Activity of Some Novel Conjugated Dyes

Novel monomethine 2a‐f , dimethine 4a‐f and tetramethine 6a‐h cyanine dyes were prepared as conjugated dyes. Such dyes incorporating coumarin and/or quinoline derivatives 1a‐d . These dyes were synthesized to study their spectral behavior, solvatochromism and biological activity. These dyes are characterized by elemental analysis, IR, ¹H NMR and mass‐spectra.     

蓝光有机存储染料研究进展

近年来,蓝光有机存储染料作为超高密度存储技术的核心已经日益受到人们的广泛关注,出现了与之相关的大量专利文献报道.本文介绍了卟啉染料、偶氮染料、菁染料、芪类染料和香豆素衍生物染料等蓝光染料的合成及应用,并对蓝光有机存储染料的发展趋势作了展望.     

Molecular origins of optoelectronic properties in coumarin dyes: toward designer solar cell and laser applications

Coumarin derivatives are used in a wide range of applications, such as dye-sensitized solar cells (DSCs) and dye lasers, and have therefore attracted considerable research interest. In order to understand the molecular origins of their optoelectronic properties, molecular structures for 29 coumarin laser dyes are statistically analyzed. To this end, data for 25 compounds were taken from the Cambridge Structural Database and compared with data for four new crystal structures of coumarin laser dyes [Coumarin 487 (C(19)H(23)NO(2)), Coumarin 498 (C(16)H(17)NO(4)S), Coumarin 510 (C(20)H(18)N(2)O(2)), and Coumarin 525 (C(22)H(18)N(2)O(3))], which are reported herein. The competing contributions of different resonance states to the bond lengths of the 4- and 7-substituted coumarin laser dyes are computed based on the harmonic oscillator stabilization energy model. Consequently, a positive correlation between the contribution of the para-quinoidal resonance state and the UV-vis peak absorption wavelength of these coumarins is revealed. Furthermore, the perturbations of optoelectronic properties, owing to chemical substituents in these coumarin laser dyes, are analyzed: it is found that their UV-vis peak absorption and lasing wavelengths experience a red shift, as the electron-donating strength of the 7-position substituent increases and/or the electron-withdrawing strength of the 3- or 4-position substituent rises; this conclusion is corroborated by quantum-chemical calculations. It is also revealed that the closer the relevant substituents align with the direction of the intramolecular charge transfer (ICT), the larger the spectral shifts and the higher the molar extinction coefficients of coumarin laser dyes. These findings are important for understanding the ICT mechanism in coumarins. Meanwhile, all structure-property correlations revealed herein will enable knowledge-based molecular design of coumarins for dye lasers and DSC applications.     

PHOTOPHYSICAL and PHOTOCHEMICAL PROPERTIES OF COUMARIN DYES IN AMPHIPHILIC MEDIA

Abstract— Photophysical properties of coumarin dyes solubilized in aqueous detergent solutions have been investigated including measurement of absorption and fluorescence emission maxima, and fluorescence quantum yields. Use of coumarin 4 as a fluorescence probe of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) solutions led to the conclusion that the sites for dye incorporation in micelles are significantly hydrogen-bonded (hydrated). The inhibition of photochemical decomposition for detergent-solubilizcd dyes has also been observed. Electron transfer from micelle-bound dye to a water soluble acceptor, methyl viologen, has been investigated by flash photolysis.     

有机染料敏化纳米晶太阳能电池

本文综述了有机染料敏化纳米晶太阳能电池的研究现状,简要介绍了有机染料敏化纳米晶太阳能电池的结构和工作原理以及氧化物电极、对电极和电解质的设计思路和制备情况。重点介绍了有机染料的研究现状,包括香豆素类染料、多烯类染料、噻吩类染料、天然染料、半花菁类染料、卟啉类染料、三苯胺类染料、苝类染料等。同时讨论了若干影响有机染料敏化太阳能电池性能的因素,提出了提高光电转换效率的设想与对策,对未来的发展进行了展望。     

A new class of laser dyes from acridinedione derivatives

Synthesis of 10-aryl-3,4,6,7,9,10-hexahydro-1,8(2H,5H)-acridinedione as a new class of laser dyes is reported. These dyes lase around 475–495 nm and are compared to the standard dye coumarin 102.     

Theoretical investigation of the excited states of coumarin dyes for dye-sensitized solar cells

Using time-dependent density functional theory (TD-DFT), configuration interaction single (CIS) method, and approximate coupled cluster singles and doubles (CC2) method, we investigated the absorption spectra of coumarin derivative dyes (C343, NKX-2388, NKX-2311, NKX-2586, and NKX-2677), which have been synthesized for efficient dye-sensitized solar cells. The CC2 calculations are found in good agreement with the experimental results except for the smallest coumarin dye (C343). TD-DFT underestimates the vertical excitation energy of the larger coumarin dyes (NKX-2586 and -2677). Solvents (methanol) are found to induce a red shift of the vertical excitation energies, and their effects on the molecular geometry and the electronic structure are examined in detail. The deprotonated form of coumarin is also investigated, where a blue shift of the vertical excitation energies is observed.     

Phosphorylated 3‐Heteroarylcoumarins and Their Use in Fluorescence Microscopy and Nanoscopy

Photostable and bright fluorescent dyes with large Stokes shifts are widely used as markers in far‐field optical microscopy, but the variety of useful dyes is limited. The present study introduces new 3‐heteroaryl coumarins decorated with a primary phosphate group (OP(O)(OH)₂) attached to C‐4 in 2,2,4‐trimethyl‐1,2‐dihydroquinoline fragment fused with the coumarin fluorophore. The general synthetic route is based on the Suzuki reaction of 3‐bromocoumarines with hetarylboronic acids followed by oxidation of the methyl group at the C?C bond with SeO₂ (to an aldehyde), reduction with NaBH₄ (to an alcohol), and conversion into a primary phosphate. The 4 position in the coumarin system may be unsubstituted or bear a methyl group. Phosphorylated coumarins were found to have high fluorescence quantum yields in the free state and after conjugation with proteins (in aqueous buffers). In super‐resolution light microscopy with stimulated emission depletion (STED), the new coumarin dyes provide an optical resolution of 40–60 nm with a low background signal. Due to their large Stokes shifts and high photostability, phosphorylated coumarins enable to combine multilabel imaging (using one detector and several excitation sources) with diffraction unlimited optical resolution.     

Coumarin-based two-photon AIE fluorophores: Photophysical properties and biological application

Based on the coumarin skeleton, we deliberately designed two groups of fluorophores, termed as Coum-R and Naph-Coum-R, using the diphenylamino group as the electron donor, which displayed long-wavelength emissions (red spectral region), large Stokes shift (up to 204 nm), superior AIE performance, and large two-photon absorbance cross-sections (as high as 365 GM). The electron-withdrawing substituents at the 3-position of these dyes could induce a significant red-shift in their emission spectra. Preliminary imaging experiments demonstrated the capability of these dyes as two-photon fluorophores for specifically staining lipid droplets in living cells.