Fluorescence Quantum Yield In Solution Research Articles

Porphyrin, Phthalocyanine and Porphyrazine Derivatives with Multifluorenyl Substituents as Efficient Deep‐Red Emitters

The synthesis and photophysical properties are described for a series of porphyrin, phthalocyanine and pyrazinoporphyrazine derivatives which bear four or eight peripheral fluorenyl substituents as antennae. Representative examples are 5,10,15,20-tetra(9,9-dihexyl-9H-fluoren-2-yl)porphyrin (2), 5,10,15,20-tetrakis[4-(9,9-dihexyl-9H-fluoren-2-yl)phenyl]porphyrin (3), 2,3,9,10,16,17,23,24-octakis(9,9-dihexyl-9H-fluoren-2-yl)-29H,31H-phthalocyanine (8) and 2,3,9,10,16,17,23,24-octakis[4-(9,9-dihexyl-9H-fluoren-2-yl)phenyl]-29H,31H-tetrapyrazinoporphyrazine (9). Palladium-mediated Suzuki-Miyaura cross-coupling reactions have been key steps for attaching the substituents. The compounds are deep-red emitters: lambda(max)(em)=659 (3), 737 (8) and 684 nm (9). Their absorption and emission spectra, their fluorescence lifetimes and quantum yields are correlated with the structures of the macrocycles and the substituents. The solution fluorescence quantum yields of porphyrin derivatives substituted with fluorene (2-4) and terphenyl substituents (7) (Phi(f)=0.21-0.23) are approximately twice that of tetraphenylporphyrin. For phthalocyanine derivative 8, Phi(f) was very high (0.88). Specific excitation of the fluorene units of 8 produced emission from both of them (lambda(max)=480 nm) and also from the phthalocyanine core (lambda(max)=750 nm), indicating a competitive rate of energy transfer and radiative decay of the fluorenes. Organic light-emitting devices (OLEDs) were made by spin-coating techniques by using a polyspirobifluorene (PSBF) copolymer as the host blended with 3 (5 wt. %) in the configuration ITO/PEDOT:PSS/PSBF copolymer:3/Ca/Al. Deep-red emission (lambda(max)=663 nm; CIE coordinates x=0.70, y=0.27) was observed with an external quantum efficiency of 2.5 % (photons/electron) (at 7.5 mA cm(-2)), a low turn-on voltage and high emission intensity (luminance) of 5500 cd m(-2) (at 250 mA/ m(2)).

Synthesis and characterization of 1,3,4‐oxadiazole‐triazolopyridinone hybrid derivatives as new blue‐greenish photoluminescent materials

Abstractmagnified imageRecently, New functionalized oxadiazole‐triazolopyridinone hybrid compounds were investigated as photoluminescent materials. In this work, we introduce triazolopyridinone to synthesize a series of oxadiazole‐triazolopyridinone hybrid derivatives as potential photoluminescent materials and explore the effect of modification of the triazolopyridinone moiety. The λmax values of the photoluminescence (PL) spectra of 1,3,4‐oxadiazole‐triazolopyridinone hybrids are promoted to longer wavelengths (470‐486 nm) than the traditional 1,2,3‐triazole derivatives (410‐425 nm) in solutions. PL spectra 5a, 5d, and 5g of the vacuum evaporated films on quartz substrates, with a maximum at 487 nm, shows a red‐shift (∼15‐20 nm), with respect to the solution spectrum. The solution fluorescence quantum yields (Φf) were measured, all of which fell into the range 0.65‐0.76, and were determined relative to that of 2‐phenyl‐5‐(4‐biphenyl)‐1,3,4‐oxadiazole in benzene (Φf = 0.80). 1,3,4‐Oxadiazole‐triazolopyridinone hybrid derivatives show clearly non‐reversible reduction processes in cyclic voltammogram measurements. Following spectroscopic studies and observation of the electrochemical behaviors, 1,3,4‐oxadiazole‐triazolopyridinone derivatives were determined to be potential efficient bluegreenish photoluminescent materials.

Synthesis and Characterization of Potential Efficient Electroluminescent Materials: 2-Phenyl-5-[4-(4-phenylamino-2H-1,2,3-triazol-2-yl)]phenyl-1,3,4-oxadiazole Derivatives

Abstract Recently, 1,3,4-oxadiazole-based on heterocyclic compounds were investigated as electroluminescent materials. In this work, we first introduce 1,2,3-triazole to synthesize a series of 1,3,4-oxadiazole–1,2,3-triazole hybrids derivatives as potential electroluminescent materials and explore the effect of modification of the 1,2,3-triazole moiety. The λmax values of the UV–vis of 1,3,4-oxadiazole–1,2,3-triazole hybrids are promoted to longer wavelengths (340–350 nm) than the traditional 1,2,3-triazole derivatives (280–330 nm) in solutions and have a bathochromic shift to 350–360 nm in THF solution. The λmax values of the photoluminescence (PL) spectra are in the range 406–480 nm in solutions. Compound 7h evaporated to form films on quartz substrates, had a maximum at 455 nm and showed a red-shift (≈40 nm) with respect to the solution spectrum. The solution fluorescence quantum yields (Φf) were measured, all of which fell into the range 0.65–0.76, and were determined relative to that of 2-phenyl-5-(4-biphenyl)-1,3,4-oxadiazole in benzene (Φf = 0.80). 1,3,4-Oxadiazole–1,2,3-triazole hybrids derivatives show unclearly reversible reduction processes in cyclic voltammogram measurements. Following spectroscopic studies and observation of the electrochemical behaviors, 1,3,4-oxadiazole–1,2,3-triazole derivatives were determined to be highly potential efficient blue electroluminescent materials.

Synthesis and characterisation of soluble aluminium complex dyes based on 5-substituted-8-hydroxyquinoline derivatives for OLED applications

Some new 5-substituted 8-hydroxyquinoline derivatives and their Al(III) complex dyes (Al( 2) 3–Al( 9) 3) have been synthesised. The compounds were characterized by 1H, 13C, mass and elemental analysis. The aluminium complexes retain the spectroscopic properties of the parent compound, namely, tris(8-hydroxyquinolinato) aluminium (III) (AlQ 3). In dichloromethane solution, these aluminium complexes show absorption maxima in the range of 390–395 nm, strong green luminescence in the range 527–536 nm and aluminium complexes show high fluorescence quantum yield in solution and thin films. The fluorescence decay in solution as well as in thin film is fitted to biexponential with τ av ranging from 3 to 9 ns. Electroluminescence (EL) of the spin-cast film of Al( 3) 3 ( 3 = 5-(2-ethylhexyloxymethyl)-8-hydroxyquinoline) as the emitting layer was performed and the turn-on voltage for the EL device is about 11 V.

1,3,6,8‐Tetraphenylpyrene Derivatives: Towards Fluorescent Liquid‐Crystalline Columns?

AbstractTetraphenylpyrene has been selected as a discotic core to promote liquid‐crystalline fluorescent columns in view of its high fluorescence quantum yield in solution and ease of substitution by flexible lateral side chains. The synthesis and characterization of ten new derivatives of pyrene have been carried out; the pyrene core has been substituted at the 1,3,6,8‐positions by phenylene rings bearing alkoxy, ester, thioether, or tris(alkoxy)benzoate groups on the para position; the compounds have been characterized by mass spectrometry and 1H NMR and UV‐vis spectroscopies. In order to generate liquid‐crystalline phases, the nature, number, and size of the side chains as well as the degree of polarity around the tetraphenylpyrene core have been varied. However, the desired liquid‐crystalline behavior has not been observed. The supramolecular order together with the absorption and emission properties in solution and the solid state are discussed and compared to theoretical predictions. Quantum‐chemical calculations rationalize the high solid‐state fluorescence of a tetraphenylpyrene derivative for which the crystal structure has been determined.

Conjugation Length Control in Soluble Poly[2-methoxy-5-((2‘-ethylhexyl)oxy)-1,4-phenylenevinylene] (MEHPPV): Synthesis, Optical Properties, and Energy Transfer

Poly[2-methoxy-5-(($2^{\prime}$-ethylhexyl)oxy)-1,4-henylenevinylene] (MEHPPV) of varying conjugation length was prepared by the selective thermal elimination of one of the substituents in a suitable precursor polymer. The precursor, a dialkoxy poly(1,4-xylylene) derivative with varying amounts of acetoxy and methoxy groups, was prepared by a competitive nucleophilic substitution of the Wessling polyelectrolyte, using methanol and sodium acetate in acetic acid as nucleophiles. Selective thermal elimination(in solution) of the acetate groups alone yielded MEHPPV of varying conjugation lengths. The selective nature of the acetate elimination was confirmed by $^1H$ NMR spectroscopy. As expected, both the absorption and emission maxima of the eliminated samples shifted to the red with increasing conjugation length. While there was very little difference between the absorption spectra of thin film and solutions of MEHPPV-x, there was a significant bathochromic shift in the emission spectra of the thin films when compared to their dilute solution spectra. Additionally, separate emission from the various oligomers, which are occasionally visible in solution, is absent in thin films. Energy transfer from short to longer conjugated segments, within a single polymer chain in solution, was inferred by comparison of the fluorescence spectra of the partially conjugated polymers with those expected from a system where simultaneous independent emission occurs from a similar collection of noninteracting oligophenylenevinylene (OPV)molecules. The latter was calculated assuming a statistically random substitution/elimination process of the precursor in conjunction with the fluorescence spectral data of OPV's reported by previous workers. The extent of energy transfer increases as the average conjugation length increases. Furthermore, unlike in the model oligomers, in the case of polymers the fluorescence quantum yield in solution rapidly decreases with increase in the average conjugation length.

Synthesis of 2,2′-bipyridine-containing polymers: synthesis of poly[2,2′-bipyridine-4,4′-diylethynylene-(2,5-dialkoxy-1,4-phenylene)ethynylene

Novel 2,2′-bipyridine-based conjugated polymers of formula 2 have been synthesized by Pd-catalyzed cross-coupling reactions between 4,4′-dibromo-2,2′-bipyridine (3) and substituted phenyldiacetylenes (4). The zig-zag arrangement of the 2,2′-bipyridine units implies a helical conformation of 2. The solubility of 2 requires at least a dodecyl side-chain. 2 is thermostable up to 400°C. The polymers have a high fluorescence quantum yield in solution (60%).

Are Fluorescence Quantum Yields So Tricky to Measure? A Demonstration Using Familiar Stationery Products

Fluorescence quantum yields are used to quantify the efficiency of the emission process. In spite of the importance of these data, experimental directions for their acquisition are rarely given. A general procedure for determining the relative fluorescence quantum yield of solutions is described here, drawing attention to the many pitfalls that students may encounter. Starting materials are common yellow and pink highlighter pens.

Radiationless Deactivation of the Fluorescent State of 9‐Methoxyanthracene and of Related meso‐Substituted Anthracenes

AbstractThe temperature dependence of the fluorescence quantum yield, the fluorescence decay time, and the triplet‐triplet absorption spectrum of 9‐methoxyanthracene have been measured in n‐heptane. The sum of the fluorescence quantum yield and the quantum yield for intersystem crossing of 9‐methoxyanthracene and two partially deuterated 9‐methoxyanthracenes at room temperature is only ∼0.60. While the fluorescence quantum yield in methyl methacrylate has nearly the same value as in n‐heptane, the fluorescence quantum yield is twice as high in the rigid matrix of PMMA. When passing from fluid solutions to the PMMA matrix, a dramatic increase in the fluorescence quantum yield can be demonstrated for the following meso‐substituted anthracenes: 9.‐tert.butyl‐, 9‐cyano, 10‐tert.butyl‐ and 9‐cyano,10‐methoxyanthracene. Anthracene, 9‐chloro‐ and 9‐phenylanthracene do not show neither this matrix effect nor an anomalous temperature dependence on the fluorescence quantum yield in solution. — The anomalous temperature dependence of the fluorescence quantum yield and fluorescence decay time and the increase in fluorescence quantum yield in the rigid PMMA matrix of 9‐methoxy‐and some meso‐substituted anthracenes indicate that at moderate temperatures a very fast S1 → S0 internal conversion is operative which competes with intersystem crossing.

Excitation energy effects on the fluorescence quantum yield in solution. Deactivation pathways for aromatic amines

Download options Please wait... Article information DOI https://doi.org/10.1039/F19807601576 Article type Paper Download Citation J. Chem. Soc., Faraday Trans. 1, 1980,76, 1576-1584 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Excitation energy effects on the fluorescence quantum yield in solution. Deactivation pathways for aromatic amines G. Köhler and N. Getoff, J. Chem. Soc., Faraday Trans. 1, 1980, 76, 1576 DOI: 10.1039/F19807601576 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Gottfried Köhler Nikola Getoff