Synthesis of N-acyl carbazoles, phenoxazines and acridines from cyclic diaryliodonium salts

• Nils Clamor,
• Mattis Damrath,
• Thomas J. Kuczmera,
• Daniel Duvinage and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2024, 20, 12–16, doi:10.3762/bjoc.20.2

• fluorophors, previously shown to exhibit strong organic phosphorescence when mixed with specific additives [1][2][3][4][5]. Carbazole units are also found in drugs and natural products. They are also used in electrochemistry and as reagents in transamidation reactions [6][7][8][9][10][11][12]. The traditional

Aromatic systems with two and three pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile fragments as electron-transporting organic semiconductors exhibiting long-lived emissions

• Karolis Leitonas,
• Brigita Vigante,
• Dmytro Volyniuk,
• Audrius Bucinskas,
• Pavels Dimitrijevs,
• Sindija Lapcinska,
• Pavel Arsenyan and
• Juozas Vidas Grazulevicius

Beilstein J. Org. Chem. 2023, 19, 1867–1880, doi:10.3762/bjoc.19.139

• respect to the incident photon energy (hν) and the hν axis. This approach allowed for a precise determination of the IPPE, facilitating a deeper understanding of the electron behavior and electronic properties of the studied materials. UV–vis absorbance, photoluminescence (PL), and phosphorescence

• . By using these solvents, we aimed to investigate and visualize the charge transfer nature of the organic compounds under study through their spectra. To prepare the films, we used a spin-coating method by using a high-concentration THF solution (2 mg/mL). To study the phosphorescence spectra of Me

• -THF solutions, measurements were performed at an ultra-low temperature of 77 K, with and without a delay after excitation. This experimental setup ensured that we could capture the long-lived phosphorescence signals with high sensitivity and accuracy. To explore the temperature-dependent

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

• assigned to singlet locally excited fluorescence (1LE) from the benzoguanidine donor ligand. The second high-energy PL component at 470 nm becomes visible only after a long-time delay (720 ms, see Figure 5 black profile), therefore, we ascribed it to a phosphorescence from a higher lying 3LE state

• localized on a donor benzoguanidine moiety. Unlike 1LE-fluorescence, 3LE-phosphorescence has a very long lifetime of 1.8 s. Excitation spectra of the broad and resolved bands for 4BGIPN in MCH glass at 77 K (Figure S4, Supporting Information File 1) follow a mirror image rule when compared with emission

• as phosphorescence from a 3CT state. A more than 100-fold increase in radiative lifetime on cooling to 77 K is characteristic for the organic TADF emitters [1]. Upon cooling Zeonex matrices of 4BGIPN from 296 K to 16 K (Figure 5), the excited state lifetime shows an order of magnitude increase down

The effect of dark states on the intersystem crossing and thermally activated delayed fluorescence of naphthalimide-phenothiazine dyads

• Liyuan Cao,
• Xi Liu,
• Xue Zhang,
• Jianzhang Zhao,
• Fabiao Yu and
• Yan Wan

Beilstein J. Org. Chem. 2023, 19, 1028–1046, doi:10.3762/bjoc.19.79

• 1CS/3CS states should be small, on a <0.1 eV scale [39][58]. For the dyads with oxidized PTZ moieties, the CS state energy is higher than that of the unoxidized molecules, and it is also decreased with increasing solvent polarity. The T1 state of NI was determined as 2.25 eV (phosphorescence method

• ) [65], and the T1 state of the PTZ unit was determined as 2.45 eV (phosphorescence method) [66]. These energy levels are close to the CS states (Table 4), and thus, in HEX and TOL, the three states 1CS, 3CS, and 3LE share a similar energy, and TADF may be resulted. For the dyads with the oxidized PTZ

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence

• Kaiyue Ye,
• Liyuan Cao,
• Davita M. E. van Raamsdonk,
• Zhijia Wang,
• Jianzhang Zhao,
• Daniel Escudero and
• Denis Jacquemin

Beilstein J. Org. Chem. 2022, 18, 1435–1453, doi:10.3762/bjoc.18.149

• explained above, an orthogonal geometry is beneficial to achieve SOCT-ISC. However, for TADF, it was proposed that the rotational freedom is beneficial for the rISC, and that too rigid molecular structures may favor phosphorescence and therefore limit rISC and TADF [34][35]. Studies with time-resolved

• phosphorescence emission spectra of NI-PTZ-O in frozen solution at 77 K were recorded (Figure 5 and Figure S29 in Supporting Information File 1). No phosphorescence was detected for NI-PTZ nor NI-PTZ2. For NI-PTZ-O (Figure 5a), a structured emission with significant vibrational progression was observed in the 520

• –650 nm range, which is attributed to the 3LE state, as the emission band is similar to the one of 4-bromo NI [48]. Thus, the 3NI state energy can be approximated to be 2.29 eV from the 0–0 band of the phosphorescence. The 3NI energy of NI-Ph-PTZ, NI-PhMe2-PTZ, and NI-3Br were determined to be 2.24 eV

Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells

• Merve Karaman,
• Abhishek Kumar Gupta,
• Subeesh Madayanad Suresh,
• Tomas Matulaitis,
• Lorenzo Mardegan,
• Daniel Tordera,
• Henk J. Bolink,
• Sen Wu,
• Stuart Warriner,
• Ifor D. Samuel and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2022, 18, 1311–1321, doi:10.3762/bjoc.18.136

• -radiative decay due to the energy gap law (ΦPL = 11% and 7% under vacuum and in air, respectively) in MeCN [37]. The S1 and T1 levels were measured from the onsets of fluorescence (2.66 eV) and phosphorescence spectra (2.41 eV) in 2-MeTHF glass at 77 K (Figure S26, Supporting Information File 1). DiKTa

• emission in the neat film was also observed for DiKTa (ΦPL = 11%, under N2) [27]. The S1 and T1 levels were measured from the onsets of fluorescence and phosphorescence spectra in the 1 wt % doped mCP film at 77 K (Figure S29 in Supporting Information File 1). The corresponding ΔEST values are 0.20 eV and

Thermally activated delayed fluorescence (TADF) emitters: sensing and boosting spin-flipping by aggregation

• Ashish Kumar Mazumdar,
• Gyana Prakash Nanda,
• Nisha Yadav,
• Upasana Deori,
• Upasha Acharyya,
• Bahadur Sk and
• Pachaiyappan Rajamalli

Beilstein J. Org. Chem. 2022, 18, 1177–1187, doi:10.3762/bjoc.18.122

• Figure 1d as well as Tables S3–S5 in Supporting Information File 1). The phosphorescence spectra of BPy-pTC and BPy-p3C were recorded in toluene at 77 K (Figure 1b). The structural phosphorescence bands were obtained for both compounds. The nature of the phosphorescence bands indicated the locally

• excited (3LE) character of the T1 state. The onset of the fluorescence spectrum (energy of S1) in toluene at room temperature and the onset of the phosphorescence spectrum (energy of T1) in toluene at 77 K was chosen to estimate the ΔEST values of the emitters (Figure 1b) [31]. A smaller singlet–triplet

• -lying triplet state T1 to the singlet excited state S1, we recorded the fluorescence and phosphorescence spectra of aggregates (90 vol % water/THF) at room temperature and 77 K, respectively (Figure 4). The structural phosphorescence band was obtained from the aggregates in 90 vol % water/THF mixtures

Substituent effect on TADF properties of 2-modified 4,6-bis(3,6-di-tert-butyl-9-carbazolyl)-5-methylpyrimidines

• Irina Fiodorova,
• Tomas Serevičius,
• Rokas Skaisgiris,
• Saulius Juršėnas and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 497–507, doi:10.3762/bjoc.18.52

• for compounds with stronger CT emission (e.g., compounds 1 and 4). The phosphorescence (PH) spectra of the carbazole–pyrimidine TADF compounds were rather intriguing. 10 K PH spectra of compounds tCbz-mPYR, 1, 3, 5, and 6 clearly resembled that of individual tCbz units, peaking at about 418 nm [29

• rest of compounds with low-energy shoulder. More detailed analysis (see Figure S30 in Supporting Information File 1) revealed the presence of room-temperature phosphorescence (RTP), perturbing the lineshape of PL spectra. The estimated singlet–triplet energy gaps (ΔEST) of carbazole–pyrimidine TADF

• and ΦDF values were estimated according to [50]. Time-integrated fluorescence, phosphorescence spectra as well as fluorescence decay kinetics were recorded with a time-gated intensified iCCD camera iStar DH340T (Andor) with a spectrograph SR-303i (Shamrock) coupled with nanosecond YAG:Nd3+ laser NT

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

• (Figure 2b), suggesting that these emissions have a mixed character of localized (1LE) and charge-transfer state (1CT, Figure 3b). The emission from the T1 state (phosphorescence, PH) at a low temperature (10 K) with the energy of ET1 = 2.26 eV showed a similar spectral shape to the phosphorescence

• and for each relevant electronic state. From these calculations, emission spectra were computed along with fluorescence, phosphorescence, and ISC rates, providing us insight into the mechanism behind the photophysical behavior of the molecules under analysis in this work. Taking fluorescence

• rates to S1 are orders of magnitude larger than estimated phosphorescence rates (Table S3 in Supporting Information File 1). The analysis of the probabilities associated with each transfer mechanism from T1 and T2 (shown in Table S8 and Table S9 of Supporting Information File 1) indicates that the

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

• , respectively, while the S1 level for DICzTRZ is more stabilized at 2.80 eV vs 2.94 eV for ICzTRZ). We can clearly observe that the phosphorescence spectrum presents a well-defined structure, typical for transitions coming from a local excited (LE) type state on the diindolocarbazole. TDA-DFT calculations in

• phosphorescence spectra at 77 K in drop-casted 20 wt % CzSi film (λexc = 343 nm, prompt and delayed fluorescence spectra were obtained in the 1–100 ns and 1–10 ms time range, respectively). Angle-resolved photoluminescence measurement of a solution-processed film of 20 wt % DICzTRZ in CzSi. The red line shows a

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• state that collides with nearby molecules to reach its lowest vibrational energy state. Another fate of T1{PS}, permitted by spin–orbit coupling, is the radiative process of phosphorescence. If a molecule exhibits a high triplet quantum yield (rapid ISC and slow phosphorescence), this state is long

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• emission behavior. Keywords: bromoarylaldehydes; click-chemistry; fluorenes; fluorescence; phosphorescence; Introduction Small organic luminophores exhibiting room-temperature phosphorescence (RTP) have attracted great attention due to promising applications in optoelectronic devices [1][2][3][4][5][6][7

• can occur. While the latter decay (fluorescence) takes place without a change in the electron spin, phosphorescence is defined as the radiative transition from the lowest excited triplet state (T1) to the singlet ground state (S0) [18][19][20][21]. Triplet state excitons are generated by the spin

• inert conditions [28] are necessary to facilitate an afterglow emission. Most phosphorescence studies are focused on metal complexes due to a strong heavy atom-induced spin-orbit coupling [29][30][31][32][33]. Considering the high price and the toxicity of many metal complexes, pure organic phosphors

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

• fluorinated benzils to emit phosphorescence, which may arise from immediate spin-orbit coupling involving the 1(n, π)→3(π, π) transition, unlike the case of fluorinated or nonfluorinated bisbenzil analogues. These findings offer a useful guide for developing novel pure organic room-temperature phosphorescent

• materials. Keywords: alkyne oxidation; benzils; bistolanes; fluorinated compounds; phosphorescence; Introduction The development of organic light-emitting molecules is recognized as one of the most important studies because of the broad application of these compounds as fluorescence probes, bio-imaging

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

• points of the compounds were determined with an Electrothermal MEL-TEMP apparatus. Absorption spectra of dilute solutions (10−4–10−5 mol/L) and thin films of the synthesized compounds were recorded with a Perkin Elmer Lambda 25 spectrophotometer. Fluorescence and phosphorescence spectra of thin films and

• . Phosphorescence spectra were recorded at 77 K. Differential scanning calorimetry (DSC) measurements were carried out using a TA Instruments Q2000 thermosystem. The samples were examined at a heating/cooling rate of 10 °C/min under a nitrogen atmosphere. Thermogravimetric analysis (TGA) was performed with a TA

• electroluminescence obtained by mixing sky-blue and orange exciplexes (a). PL spectra of the film of 1, of exciplexes m-MTDATA:1/1:PO-T2T and phosphorescence spectrum of the solution of compound 1 in THF at 77 K (b). Phosphorescence was recorded with the delay of 50 ms after UV excitation (300 nm). EL spectra of OLED

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

• , respectively. The relatively high PL efficiency of the film of 4 originates from the more efficient CT contribution to the emission. The PL and phosphorescence spectra of dilute THF solutions of the studied derivatives recorded at 77 K are shown in Figure 3b. The PL spectra recorded at liquid nitrogen

• values were estimated as 2.54 eV for 4, and 2.67 eV for 3 and 6. The triplet energy could not be estimated for derivative 5, since the phosphorescence at 77 K was practically undetectable for this compound. Electrochemical and photoelectrical properties The electrochemical properties of the acridane

• [29]. DSC curves of compounds 4 and 5. Absorption and PL spectra (λex = 330 nm) of compounds 3–6. a) Absorption spectra as neat films, dilute THF and toluene solutions. b) PL and phosphorescence spectra in dilute THF solutions at 77 K. a) Cyclic voltammogram of derivative 3 in dichloromethane (a three

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• known photocatalysts, such as aryl ketones (Scheme 3) [15][16][17]. Later, Steel and co-workers examined the photochemical properties of benzaldehyde (8), studying the EnT from 8 to azo compounds [18]. Upon the irradiation and excitation of benzaldehyde (8), the phosphorescence was quenched either by

• electronic distribution and the spectroscopy of the excited states of benzaldehyde (8) have been examined. These studies illuminate the ways that the various excited states of benzaldehyde (8) decay, either through phosphorescence or through the dissociation to benzene (21) and carbon monoxide (22) or to a

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• hand, S1 can also transition to the spin-forbidden T1 through intersystem crossing (ISC), which then decays by (longer) radiative processes to S0 (phosphorescence. Figure 3) [41][42][43]. The triplet excited state is oxygen-sensitive as O2 carries out quenching in solution, thereby leading to the

• disappearance of phosphorescence, following the Frank–Condon principle [44][45]. As far as the singlet and triplet excited states of organic dyes and organometallic compounds are concerned, there is a difference in lifetimes. Usually, the lifetime of excited states of organic dyes is nanoseconds, whereas for

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

• ) properties. In EL devices, such as organic light-emitting diodes (OLEDs), there are three main exciton-harvesting mechanisms for organic compounds that offer the potential to expand beyond the 25% internal quantum efficiency (IQE) offered by fluorophores: (1) phosphorescence, frequently mediated by a rare

Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex

• Yoichi Kobayashi,
• Yukie Mamiya,
• Katsuya Mutoh,
• Hikaru Sotome,
• Masafumi Koga,
• Hiroshi Miyasaka and
• Jiro Abe

Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229

• triplet–triplet energy transfer process in Benzil-PIC, we performed two experiments. Firstly, we measured the phosphorescence spectra of benzil and PIC in EPA (diethyl ether/isopentane/ethanol 5:5:2) at low temperature to estimate the energy levels of the T1 states of benzil and PIC. In the conventional

• emission measurement setups at low temperature, both fluorescence and phosphorescence are observed upon irradiation of excitation light. To extract the phosphorescence spectra, the excitation light (continuous wave laser, 355 nm, 1 mW) was chopped at 1 Hz and the afterglow emission under blocking the beam

• was accumulated as the phosphorescence spectra. Figure 4 shows the phosphorescence spectra of benzil in EPA at 77 and 100 K. While the phosphorescence spectrum of benzil at 77 K is broad and observed at 500 nm, that at 100 K becomes sharper and the peak is shifted to 567 nm with a vibrational fine

Fluorescent phosphorus dendrimers excited by two photons: synthesis, two-photon absorption properties and biological uses

• Anne-Marie Caminade,
• Artem Zibarov,
• Eduardo Cueto Diaz,
• Aurélien Hameau,
• Maxime Klausen,
• Kathleen Moineau-Chane Ching,
• Jean-Pierre Majoral,
• Jean-Baptiste Verlhac,
• Olivier Mongin and
• Mireille Blanchard-Desce

Beilstein J. Org. Chem. 2019, 15, 2287–2303, doi:10.3762/bjoc.15.221

• phosphorescence of certain minerals after being exposed to sun light, have fascinated Men for a long time. An important part of luminescence phenomena is due to the influence of light (generally visible or ultra-violet light) on matter, such as for instance a molecule, which can emit light at a wavelength

• intersystem conversion towards a triplet state (T1), from which there will be emission of phosphorescence, having generally a lifetime longer than that of fluorescence. This classical one-photon excited fluorescence has led to the design of numerous types of chemical entities since the XIX century. For

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• singlet state 1MLCT can undergo ultrafast intersystem crossing leading to the formation of the triplet state 3MLCT which could emit phosphorescence. Ru(dcbpy)3 was employed as a representative candidate in this work to study the photophysical response upon complexation with GC5A. Almost no appreciable

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• efficiency of the PET process. The decay of T1 is negligible as the processes which bring this about (phosphorescence mainly) are symmetry forbidden and hence very slow. Therefore, if a molecule can reach the T1 state through excitation with visible light then it is one which can be considered as a

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

• ; electroluminescence; OLED; phosphorescence; platinum complexes; Introduction Photoactive TMCs have attracted enormous attention in the last two decades because of their peculiar photophysical and rich redox properties, which make them appealing from both fundamental research and technological applications points of

• between hundreds of nanoseconds to several microseconds, constituting a formally spin-forbidden transition (phosphorescence). Structural modification of the TMCs and proper tailoring of coordinated ligands can independently act on the nature, energy and topology of frontier orbitals. In fact, a fine

• supplementary interactions reinforced the ligand–metal bond, which explains well the remarkable phosphorescence efficiency obtained in solid-state thin films being PLQY of 0.52 and 0.83 for 8 and 9, respectively. Such findings prompted the authors to fabricate non-doped OLEDs with an architecture as follows

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

• as suitable HOMO and LUMO energy levels. This preferable performance suggests that CEPDO and CBPDO are alternative bipolar host materials for the PhOLEDs. Keywords: host materials; phenothiazine; phosphorescence; synthesis; Introduction Since 1987, the Tang group [1] firstly reported double organic

• phosphorescence (77 K) spectra of CEPDO (a) and CBPDO (b) in solution, respectively. Obviously, the strong absorption peak at 236 nm can be ascribed to the π→π* transition of carbazole moiety of the molecules, and the weaker absorptions around 295 nm assign to the n→π* transition of the conjugation of the whole

• the triplet energy level, their low-temperature Phos spectra were measured in a 2-methyltetrahydrofuran solution at 77 K which are also shown in Figure 2. The phosphorescence emission peaks were at 440 nm and 439 nm, respectively. According to the onset of their phosphorescence spectra, the calculated

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

• ) are shorter compared to the phosphorescence decay of the α-duryl-substituted complex (8.7 µs at 77 K in 2-MeTHF). The observed effects can be attributed to a major influence of the counter ligand on the emission characteristics, which is further supported by the localization of spin density almost

• phosphorescence decay of all complexes was measured with an Edinburgh Instruments mini-τ by excitation with a pulsed EPLED (360 nm, 20 kHz) and time-resolved photon counting (TCSPC). Frozen 2-MeTHF glass emission samples at 77 K were prepared by inserting a sealed quartz tube, containing the solution under argon