Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• a certain application, for example where charge transport is more important than photoluminescence quantum yield or vice versa. Introducing alkyl chains can provide solubility, enabling facile solution processing, such as device printing techniques [13]. Hence, there is an ongoing interest in

• , we published a series of ‘bent’ diindenodithienothiophene derivatives (2–4, Figure 2) [16]. It was observed that oxidising the central sulfur atom significantly increased the solution photoluminescence quantum yield (PLQY) from 0.004 (3) to 0.72 (4). The diketo derivative 5 of compound 2 has been

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• feasible to be bound with pyridine groups. As shown in Figure 3a, the protonation by CSA resulted in a significant red-shift in the photoluminescence (PL) spectrum, which was similar to the cases caused by other Lewis acids such as methanesulfonic acid (MSA) and dichloracetic acid (DCA). Wang et al. used

• molecular synthesis. Lewis acid–base interactions found some promising applications in band gap engineering, photoluminescence, and electroluminescence. The in-depth study of the mechanisms of this phenomenon could inspire the innovation in cutting-edge researches beyond organic light-emitting diodes [29

• by 330 nm) for 35DCzPPy (compound 14), B(C6F5)3, B(C6H5)3, 35DCzPPy:B(C6F5)3 (1:1), and 35DCzPPy:B(C6H5)3 (1:1) in films. (c) Fluorescence decay curves for the solid films of 35DCzPPy, 35DCzPPy:B(C6H5)3, and 35DCzPPy:B(C6F5)3 recorded at photoluminescence maxima (385, 435, and 509 nm) at room

Comparative study of thermally activated delayed fluorescent properties of donor–acceptor and donor–acceptor–donor architectures based on phenoxazine and dibenzo[a,j]phenazine

• Saika Izumi,
• Prasannamani Govindharaj,
• Anna Drewniak,
• Paola Zimmermann Crocomo,
• Satoshi Minakata,
• Leonardo Evaristo de Sousa,
• Piotr de Silva,
• Przemyslaw Data and
• Youhei Takeda

Beilstein J. Org. Chem. 2022, 18, 459–468, doi:10.3762/bjoc.18.48

• -state photoluminescence (PL) spectra were acquired (Figure 2, and the summary of the properties presented in Table 1). The solutions were prepared with a variety of organic solvents at concentrations of ca. 10−5 M. It is noted that the solubility of 1 in cyclohexane is quite low, and thereby the

• the D–A compound 1 compared to POZ-DBPHZ reflects the contribution of an additional donor to relaxation of the molecular geometry in the excited state. The photoluminescence quantum yield (ΦPL) of the D–A compound 1 is lower (0.13 in cyclohexane) than that of the D–A–D compound POZ-DBPHZ (0.33) [17

• performed using a time-resolved spectroscopic technique (Figure 3). Time-resolved photoluminescence (PL) from a blended film (1 wt % of 1 in Zeonex®) at 300 K showed two-components emission consisting of a prompt fluorescence (PF) that decays within the order of nanoseconds and a delayed fluorescence (DF

Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode

• Ettore Crovini,
• Zhen Zhang,
• Yu Kusakabe,
• Yongxia Ren,
• Yoshimasa Wada,
• Bilal A. Naqvi,
• Prakhar Sahay,
• Tomas Matulaitis,
• Stefan Diesing,
• Ifor D. W. Samuel,
• Wolfgang Brütting,
• Katsuaki Suzuki,
• Hironori Kaji,
• Stefan Bräse and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 2894–2905, doi:10.3762/bjoc.17.197

• nm compared to that of ICzTRZ at 475 nm and showed a comparable photoluminescence quantum yield of 57.1% in a 20 wt % CzSi film versus 63.3% for ICzTRZ. The emitter was then incorporated within a solution-processed organic light-emitting diode that showed a maximum external quantum efficiency of 8.4

• present high photoluminescence quantum yields, ΦPL, of 75.2% and 71.9%, respectively, and delayed fluorescence lifetimes, τd, of 25.48 μs and 34.31 μs, respectively. The devices produced with these materials reached maximum external quantum efficiencies (EQEmax) values of 14.5% and 30% at low brightness

• nearly complete horizontal orientation in a wide number of host matrices. The best combination of properties was obtained in mCBP as a host, with the photoluminescence maximum wavelength, λPL of 479 nm, ΦPL of 70%, and a τd of 121.1 μs for the vacuum-deposited doped film. The anisotropy factor (a) in 5

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• ]. More interestingly, the high fluorescence quantum yield as well as the excellent photoluminescence quantum efficiency in addition to extraordinary thermal stability are the most significant characteristics of these systems. Interestingly, this versatile C3-symmetric aromatic framework can also formally

Synthesis, structural characterization, and optical properties of benzo[f]naphtho[2,3-b]phosphoindoles

• Mio Matsumura,
• Takahiro Teramoto,
• Masato Kawakubo,
• Masatoshi Kawahata,
• Yuki Murata,
• Kentaro Yamaguchi,
• Masanobu Uchiyama and
• Shuji Yasuike

Beilstein J. Org. Chem. 2021, 17, 671–677, doi:10.3762/bjoc.17.56

• the pentacyclic ring is almost planar. Fluorescence spectroscopy data showed that the phosphole derivatives, such as phosphine oxide and the phospholium salt and borane complex exhibited photoluminescence in chloroform. Keywords: benzo[f]naphtho[2,3-b]phosphoindole; molecular structure; optical

• solution. Fluorescence spectroscopy data showed that the phosphole derivatives, such as a phosphine oxide, phospholium salt, and borane complex, exhibited photoluminescence in chloroform. The π and π* levels in all-functionalized phosphole derivatives are lower than those of the parent phosphole, owing to

Exploring the possibility of using fluorine-involved non-conjugated electron-withdrawing groups for thermally activated delayed fluorescence emitters by TD-DFT calculation

• Dongyang Chen and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 210–223, doi:10.3762/bjoc.17.21

• carbazoles was disposed meta or para to the cyano acceptor [19]. OLEDs fabricated using 2,6-2CzBN as the emitter exhibited deep blue emission with λEL = 418 nm and CIE coordinate of (0.15, 0.05); however, due to the low photoluminescence quantum yields (ΦPLs) (28% in 10 wt % DPEPO films) and relatively slow

Naphthalonitriles featuring efficient emission in solution and in the solid state

• Sidharth Thulaseedharan Nair Sailaja,
• Iván Maisuls,
• Jutta Kösters,
• Alexander Hepp,
• Andreas Faust,
• Jens Voskuhl and
• Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

• scattering (DLS). The steady-state and time-resolved photoluminescence spectroscopy studies revealed that all the molecules show intense fluorescence both in solution and in the aggregated state. In THF solutions, a blue emission was observed for the unsubstituted (H), methyl- (Me) and tert-butyl- (t-Bu

• , the π-donor nature of the substituents on the phenyl ring constitutes the main parameter that influences the photophysical properties, such as excited state lifetimes and photoluminescence quantum yields. Hence, a series of highly luminescent materials from deep blue to red emission depending on

• aromatic rings that emit efficiently in very dilute solutions. However, the photoluminescence quantum yields tend to decrease or even fully quench in the aggregated or solid states, due to the well-known effect of aggregation caused quenching (ACQ) [9][10]. This is mainly related to intersystem crossing

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• ][124][125][126][127]. Despite its structural similarities to graphite, the charge carrier mobility in g-C3N4 is significantly different. Transient absorption and transient photoluminescence (TRPL) spectroscopy analysis of a set of g-C3N4 materials found that the charge transport was predominantly

• (HER). The FSO-FS polymer displayed the highest rates of hydrogen evolution (170 μmol⋅h−1), significantly higher than its structural isomer FSO-FSz. The authors studied the charge transfer dynamics of the different polymers through temperature-dependent photoluminescence, photoelectrochemical

Development of fluorinated benzils and bisbenzils as room-temperature phosphorescent molecules

• Shigeyuki Yamada,
• Takuya Higashida,
• Yizhou Wang,
• Masato Morita,
• Takuya Hosokai,
• Kaveendra Maduwantha,
• Kaveenga Rasika Koswattage and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 1154–1162, doi:10.3762/bjoc.16.102

• photophysical properties of the benzil and bisbenzil derivatives in toluene at 25 °C showed both fluorescence with a photoluminescence (PL) band at a maximum wavelength (λPL) of around 400 nm and phosphorescence with a PL band at a λPL of around 560 nm. Interestingly, intersystem crossing effectively caused

• concentrations in toluene were 1.0 × 10−5 and 1.0 × 10−3 M for the absorption and photoluminescence (PL) measurements, respectively, and the absorption and PL spectra are shown in Figure 4. The photophysical data obtained from these measurements are summarized in Table 1. The methoxy-substituted fluorinated

• derivatives previously developed by our group and (B) phosphorescent molecular structures intended for this work. Mulliken charge distributions of fluorinated 1a and nonfluorinated 1c obtained from density functional theory calculations [CAM-B3LYP/6-31+G(d) level]. Absorption and photoluminescence (PL

Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

• Rasa Keruckiene,
• Simona Vekteryte,
• Ervinas Urbonas,
• Matas Guzauskas,
• Eigirdas Skuodis,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101

• photoluminescence and electroluminescence based on blue emissive quinazoline derivatives obtained through controlled acid protonation were employed in a single-layered white OLED with EQEs of 1.4% and 3% [9]. These reports proved that by using an asymmetric quinazoline acceptor, highly efficient TADF materials for

• the derivatives 1–3 correlated with electrochemically estimated ones and with the ionization potential values discussed above. The photophysical characteristics determined from the UV–vis absorption and photoluminescence spectra are collected in Table 2. The emission spectra of diluted toluene

• dilute solutions (10−4–10−5 mol/L) of the compounds were recorded at room (295 K) and low (77 K) temperatures with a luminescence spectrometer Edinburgh Instruments FLS980. Photoluminescence quantum yields (PLQY) of the solutions and thin films of the materials were measured using an integrating sphere

Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties

• Nuray Altinolcek,
• Ahmet Battal,
• Mustafa Tavasli,
• William J. Peveler,
• Holly A. Yu and
• Peter J. Skabara

Beilstein J. Org. Chem. 2020, 16, 1066–1074, doi:10.3762/bjoc.16.93

• the meta position to the carbazole ring. The photoluminescence (PL) properties of compounds 7a and 7b were investigated in dichloromethane using a Duetta Fluorescence and Absorbance Spectrometer. Compounds 7a and 7b gave emission maxima at 561 nm and 482 nm, respectively. The UV–vis and PL spectra of

• dependent on the excitation wavelength chosen and the solvent used. It is believed that the dual emission was due to mixed locally excited (LE) and intramolecular charge transfer (ICT) states and the single emission was due to the ICT state. Photoluminescence (PL) spectra of compounds 7a and 7b in different

• ) techniques. UV, PL and photoluminescence quantum yields were measured on a Duetta two-in-one fluorescence and absorbance spectrometer from Horiba Scientific. Both absorption and emission solutions for reference and samples had a concentration of 10−6 M. CV measurements were obtained using a CH Instruments

Aryl-substituted acridanes as hosts for TADF-based OLEDs

• Naveen Masimukku,
• Dalius Gudeika,
• Oleksandr Bezvikonnyi,
• Ihor Syvorotka,
• Rasa Keruckiene,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 989–1000, doi:10.3762/bjoc.16.88

• molecular weights resulting in a stronger intermolecular interaction and by larger volumes restricting molecular motion. These observations confirm that compounds 3–5 can be used for the preparation of thin amorphous layers on substrates. Photophysical properties The absorption and photoluminescence (PL

• earlier [34]. 1H NMR and 13C NMR spectra were obtained using a Varian Unity Inova (300 MHz (1H) and 75 MHz (13C)). Absorption and photoluminescence (PL) spectra of dilute solutions and of the films were recorded as described previously [35]. Theoretical calculations were carried out using Gaussian 16 [29

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• triplet state can be another pathway to understand the lower emission quantum yield of the BODIPYs. However, reactive singlet oxygen species (1O2) was not observed under the aerobic conditions probed by the near-infrared photoluminescence at 1270 nm. The above spectral features were likewise shown with

• , and DFT calculations. Supporting Information File 167: Crystallographic information file of compound 3a. Supporting Information File 168: Crystallographic information file of compound 6b. Acknowledgements We thank Dr. T. Ono at Kyushu University for the help of absolute photoluminescence quantum

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• dehydrogenative coupling adopting oxygen atom as the linker [12][13][14][15][16][17]. In particular, bisbenzofuro[2,3-b:3′,2′-e]pyridines (BBZFPys) were found to exhibit intense photoluminescence with relatively high quantum efficiency (Φflu up to 0.70), indicating that the BBFZPy scaffold may serve as a key

• Mettler Toledo MP90. High-resolution mass spectra (HRMS) were recorded by APCI-TOF or EI. Preparative gel permeation chromatography (GPC) was conducted with a YMC GPC-T2000 column eluting with CHCl3. Absorption spectra were recorded with JASCO V-750 spectrometer. Photoluminescence spectra were recorded

Synthesis and optoelectronic properties of benzoquinone-based donor–acceptor compounds

• Daniel R. Sutherland,
• Nidhi Sharma,
• Georgina M. Rosair,
• Ifor D. W. Samuel,
• Ai-Lan Lee and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2019, 15, 2914–2921, doi:10.3762/bjoc.15.285

• LUMO energies of 2–5 are in good agreement with the calculated values (Figure 3). Photophysical properties We next investigated the photophysical properties of 2–5. The UV–vis absorption and photoluminescence (PL) spectra in degassed DCM solution are shown in Figure 5, and the data are summarized in

• photoluminescence quantum yield (ΦPL) of 3 is poor at 4%. We next investigated the solid-state PL behavior of 3 in a 10 wt %-doped thin film using PMMA as host matrix. The PL spectrum of 3 exhibited two bands, one at 550 nm, corresponding to the emission of 3 and a second high-energy band at 450 nm that was

• of 3 and 4. HOMO/LUMO and S1/T1 energies as well as HOMO/LUMO electron density distribution profiles of 2–5. Cyclic voltammograms and differential pulse voltammograms of 2–5 in degassed DCM (scan rate = 100 mV·s−1). UV–vis absorption spectra of 2–5 in DCM and photoluminescence spectrum of 3 in

Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines

• Andrejs Šišuļins,
• Jonas Bucevičius,
• Yu-Ting Tseng,
• Irina Novosjolova,
• Kaspars Traskovskis,
• Ērika Bizdēna,
• Huan-Tsung Chang,
• Sigitas Tumkevičius and
• Māris Turks

Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41

• . Wavelengths are given in cm−1. The UV–vis absorption spectra of all compounds were acquired using a Perkin-Elmer 35 UV–vis spectrometer. Emission spectra were measured on QuantaMaster 40 steady state spectrofluorometer (Photon Technology International, Inc.). Absolute photoluminescence quantum yields were

Fabrication of supramolecular cyclodextrin–fullerene nonwovens by electrospinning

• Hiroaki Yoshida,
• Ken Kikuta and
• Toshiyuki Kida

Beilstein J. Org. Chem. 2019, 15, 89–95, doi:10.3762/bjoc.15.10

• ). Because the red photoluminescence of C60 is useful for a bioimaging applications [30][31], the electrospun fibers were measured with confocal laser scanning microscopy (CLSM). Interestingly, a uniform red color distribution is observed (Figure S9, in Supporting Information File 1), indicating the presence

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• state of the photocatalyst is a key factor for the energy transfer mechanism. To obtain a detailed mechanistic insight, steady-state photoluminescence (PL) quenching of photocatalyst 8 was examined using xanthate 1a and 1-octene (2a) as potential quenchers (Figure 1). The intensity of the PL peak of

• triplet-sensitization process of xanthates by an excited iridium-based photocatalyst. Photoluminescence (PL) spectra of the 3MLCT state of 8 in degassed DMSO solvent with (A) various concentrations of xanthate 1a added and (B) 40 mM of 1-octene (2a) added. The inset of (A) gives the Stern–Volmer plot of

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• with time-resolved photoluminescence spectroscopy revealed that the oxidative quenching of the excited state of Irdfppy favorably proceeds over the reductive quenching mechanism. The combination of 1 and Irdfppy offers the best choice for the dechlorination of DDT among our light-driven systems in

Synthesis and photophysical studies of a multivalent photoreactive Ru^II-calix[4]arene complex bearing RGD-containing cyclopentapeptides

• Sofia Kajouj,
• Lionel Marcelis,
• Alice Mattiuzzi,
• Adrien Grassin,
• Damien Dufour,
• Pierre Van Antwerpen,
• Didier Boturyn,
• Eric Defrancq,
• Mathieu Surin,
• Julien De Winter,
• Pascal Gerbaux,
• Ivan Jabin and
• Cécile Moucheron

Beilstein J. Org. Chem. 2018, 14, 1758–1768, doi:10.3762/bjoc.14.150

• calix[4]arene scaffold. Fortunately, these small aggregates totally disappeared when only 5% of DMSO was added to the medium [80]. The photoluminescence emission originating from the 3MLCT state is centered at 645 nm for both conjugate 9 and reference [Ru(TAP)2phen]2+complex. We measured the

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• tuneable over the entire visible spectrum and beyond; together with compounds with photoluminescence quantum yield (PLQY) approaching unity. These peculiar features have greatly fuelled the still growing interest in luminescent TMCs for its potential employment in applications and real-market technology

• narrow deep blue photoluminescence (CIE = 0.14, 0.12) with a PLQY of 0.30 in PMMA films. Multilayer vacuum-processed OLEDs were fabricated to test the electroluminescence performance of this complex. A remarkable value of 8% of EQE was attained, but a severe roll-off efficiency was observed with an EQE

• ···platinum intermolecular distance. These compounds were also suitable OLED dopants, achieving high EQE of 8.5–11.5%. Nevertheless, the electroluminescence was slightly broader than the corresponding photoluminescence due to incomplete suppression of the intermolecular interactions. Taking advantage of the

Two novel blue phosphorescent host materials containing phenothiazine-5,5-dioxide structure derivatives

• Feng-Ming Xie,
• Qingdong Ou,
• Qiang Zhang,
• Jiang-Kun Zhang,
• Guo-Liang Dai,
• Xin Zhao and
• Huai-Xin Wei

Beilstein J. Org. Chem. 2018, 14, 869–874, doi:10.3762/bjoc.14.73

• electron-withdrawing ability of the phenothiazine-5,5-dioxide unit, thus realized the orbital separation of hole and electron transport in the same molecule. This indicated CEPDO and CBPDO have bipolar characteristic. Photophysical properties Figure 2 presents the UV–vis absorption, photoluminescence and

• materials for PhOLEDs. Structures and molecular orbitals of (a) CEPDO and (b) CBPDO. UV–vis absorption and photoluminescence spectra in DCM solution (1 × 10−5 M and 1 × 10−6 M, respectively) at room temperature, phosphorescence spectra in 2-MeTHF solution (1 × 10−3 M) at 77 K of CEPDO (a) and CBPDO (b

D–A–D-type orange-light emitting thermally activated delayed fluorescence (TADF) materials based on a fluorenone unit: simulation, photoluminescence and electroluminescence studies

• Lin Gan,
• Xianglong Li,
• Xinyi Cai,
• Kunkun Liu,
• Wei Li and
• Shi-Jian Su

Beilstein J. Org. Chem. 2018, 14, 672–681, doi:10.3762/bjoc.14.55

• different configurations have a serious effect on the photoluminescence and electroluminescence performance according to the change in singlet–triplet splitting energy (ΔEST) and excited state geometry. This indicates that a better configuration design can reduce internal conversion and improve triplet

• spectrometry. Both of them show TADF behavior with orange emission color according to the photoluminescence spectra and time-resolved transient photoluminescence decay measurement. EQEs of 2.9% and 8.9% were achieved for the OLED devices based on 1 and 2, respectively, which are higher than the theoretical

• high photoluminescence (PL) quantum yields [13][14][15]. The calculated ΔEST of 1 and 2 are 0.33 and 0.27 eV, which are small enough to achieve TADF behavior. As shown in Figure 1c, the twisting angle (θ’) of 1 in S1 is 63.74°, which is much smaller than its θ in S0, meanwhile, the conformation of the

Enhanced quantum yields by sterically demanding aryl-substituted β-diketonate ancillary ligands

• Rebecca Pittkowski and
• Thomas Strassner

Beilstein J. Org. Chem. 2018, 14, 664–671, doi:10.3762/bjoc.14.54

• weak emission, to mesityl (mes) or duryl (dur) substituted acetylacetonates. The new complexes show very efficient emission with quantum yields >70% in the sky-blue spectral region (480 nm) and short decay times (<3 μs). Keywords: ancillary ligand; β-diketonates; photoluminescence; platinum(II

• minor deviations in the absorption intensity. Both complexes exhibit a strong absorption in the ultraviolet spectral region with an intense shoulder at 241 nm. Two weak and one more intense absorption bands are additionally located at 280 nm, 293 m, and 313 nm, respectively. Photoluminescence spectra

• complexes were measured on a Perkin Elmer lambda 25 spectrophotometer in dichloromethane solution. Photoluminescence measurements were performed in amorphous PMMA thin films doped with the emitter. Films were prepared by doctor blading a solution of 2 wt % emitter in a 10 wt % PMMA solution in