共查询到20条相似文献,搜索用时 31 毫秒
1.
Ying-Li Rao Dylan Schoenmakers Yi-Lu Chang Jia-Sheng Lu Prof. Zheng-Hong Lu Prof. Youngjin Kang Prof. Suning Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(36):11306-11316
New phosphorescent PtII compounds based on dimesitylboron (BMes2)-functionalized 2-phenylpyridyl (ppy) N,C-chelate ligands and an acetylacetonato ancillary ligand have been achieved. We have found that BMes2 substitution at the 4′-position of the phenyl ring can blue-shift the phosphorescent emission energy of the PtII compound by approximately 50 nm, compared to the 5′-BMes2 substituted analogue, without substantial loss of luminescent quantum efficiencies. The emission color of the 4′-BMes2 substituted PtII compound, Pt(Bppy)(acac) ( 1 ) can be further tuned by the introduction of a substituent group at the 3′-position of the phenyl ring. A methyl substituent red-shifts the emission energy of 1 by approximately 10 nm whereas a fluoro substituent blue-shifts the emission energy by about 6 nm. Using this strategy, three bright blue-green phosphorescent PtII compounds 1 , 2 and 3 with emission energy at 481, 492, and 475 nm and ΦPL=0.43, 0.26 and 0.25, respectively, have been achieved. In addition, we have examined the impact of BMes2 substitution on 3,5-dipyridylbenzene (dpb) N,C,N-chelate PtII compounds by synthesizing compound 4 , Pt(Bdpb)Cl, which has a BMes2 group at the 4′-position of the benzene ring. Compound 4 has a phosphorescent emission band at 485 nm and ΦPL=0.70. Highly efficient blue-green electroluminescent (EL) devices with a double-layer structure and compounds 1 , 3 or 4 as the phosphorescent dopant have been fabricated. At 100 cd m−2 luminance, EL devices based on 1 , 3 and 4 with an external quantum efficiency of 4.7, 6.5 and 13.4 %, respectively, have been achieved. 相似文献
2.
Dr. Masayuki Gon Junko Wakabayashi Masashi Nakamura Prof. Dr. Kazuo Tanaka Prof. Dr. Yoshiki Chujo 《化学:亚洲杂志》2021,16(6):696-703
We demonstrate that multi-fluorinated boron-fused azobenzene (BAz) complexes can work as a strong electron acceptor in electron donor-acceptor (D-A) type π-conjugated polymers. Position-dependent substitution effects were revealed, and the energy level of the lowest unoccupied molecular orbital (LUMO) was critically decreased by fluorination. As a result, the obtained polymers showed near-infrared (NIR) emission (λPL=758–847 nm) with high absolute photoluminescence quantum yield (ΦPL=7–23%) originating from low-lying LUMO energy levels of the BAz moieties (−3.94 to −4.25 eV). Owing to inherent solid-state emissive properties of the BAz units, deeper NIR emission (λPL=852980 nm) was detected in film state. Clear solvent effects prove that the NIR emission is from a charge transfer state originating from a strong D-A interaction. The effects of fluorination on the frontier orbitals are well understandable and predictable by theoretical calculation with density functional theory. This study demonstrates the effectiveness of fluorination to the BAz units for producing a strong electron-accepting unit through fine-tuning of energy gaps, which can be the promising strategy for designing NIR absorptive and emissive materials. 相似文献
3.
Dr. Zafar Mahmood Noreen Rehmat Prof. Shaomin Ji Prof. Jianzhang Zhao Shanshan Sun Dr. Mariangela Di Donato Prof. Mingde Li Maria Teddei Prof. Yanping Huo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):14912-14918
Zinc(II) bis(dipyrrin) complexes, which feature intense visible absorption and efficient symmetry breaking charge transfer (SBCT) are outstanding candidates for photovoltaics but their short lived triplet states limit applications in several areas. Herein we demonstrate that triplet excited state dynamics of bis(dipyrrin) complexes can be efficiently tuned by attaching electron donating aryl moieties at the 5,5′-position of the complexes. For the first time, a long lived triplet excited state (τT=296 μs) along with efficient ISC ability (ΦΔ=71 %) was observed for zinc(II) bis(dipyrrin) complexes, formed via SBCT. The results revealed that molecular geometry and energy gap between the charge transfer (CT) state and triplet energy levels strongly control the triplet excited state properties of the complexes. An efficient triplet–triplet annihilation upconversion system was devised for the first time using a SBCT architecture as triplet photosensitizer, reaching a high upconversion quantum yield of 6.2 %. Our findings provide a blueprint for the development of triplet photosensitizers based on earth abundant metal complexes with long lived triplet state for revolutionary photochemical applications. 相似文献
4.
Elżbieta Tomaszewicz Malgorzata Guzik Joanna Cybińska Janina Legendziewicz 《Helvetica chimica acta》2009,92(11):2274-2290
A new Zn and Eu tungstate was characterized by spectroscopic techniques. This tungstate, of the formula ZnEu4W3O16, crystallized in the orthorhombic system and was synthesized by a solid‐state reaction. It melts incongruently at 1330°. The luminescent properties, including excitation and emission processes, luminescent dynamics, and local environments of the Eu3+ ions in ZnEu4W3O16 and ZnY4W3O16 : Eu3+ diluted phases (1, 5, and 10 mol‐% of Eu3+ ion) were studied basing on the f6‐intraconfigurational transitions in the 250–720 nm spectral range. The excitation spectra of this system (λem 615 and 470 nm) show broad bands with maxima at 265 and 315 nm related to the ligand‐to‐metal charge‐transfer (LMCT) states. The emission spectra under excitation at the O→W (265 nm) and O→Eu3+ (315 nm) LMCT states present the blue‐green emission bands. The emission of tungstate groups mainly originate from the charge‐transfer state of excited 2p orbitals of O2? to the empty orbitals of the central W6+ ions. On the other hand, in the emission of the Eu3+ ions, both the charge transfer from O2? to Eu3+ and the energy transfer from W6+ ions to Eu3+ are involved. The emission spectra under excitation at the 7F0→5L6 transition of the Eu3+ ion (394 nm) of ZnY4W3O16 : Eu3+ diluted samples show narrow emission lines from the 5D3, 5D2, and 5D1 emitting states. The effect of the active‐ion (Eu3+) concentration on the colorimetric characteristic of the emissions of the compound under investigation are presented. 相似文献
5.
Hooi Ling Kee James R. Diers Marcin Ptaszek Chinnasamy Muthiah Dazhong Fan Jonathan S. Lindsey David F. Bocian Dewey Holten 《Photochemistry and photobiology》2009,85(4):909-920
The photophysical properties of two energy‐transfer dyads that are potential candidates for near‐infrared (NIR) imaging probes are investigated as a function of solvent polarity. The dyads ( FbC‐FbB and ZnC‐FbB ) contain either a free base (Fb) or zinc (Zn) chlorin (C) as the energy donor and a free base bacteriochlorin (B) as the energy acceptor. The dyads were studied in toluene, chlorobenzene, 1,2‐dichlorobenzene, acetone, acetonitrile and dimethylsulfoxide (DMSO). In both dyads, energy transfer from the chlorin to bacteriochlorin occurs with a rate constant of ~(5–10 ps)?1 and a yield of >99% in nonpolar and polar media. In toluene, the fluorescence yields (Φ f = 0.19) and singlet excited‐state lifetimes (τ~5.5 ns) are comparable to those of the benchmark bacteriochlorin. The fluorescence yield and excited‐state lifetime decrease as the solvent polarity increases, with quenching by intramolecular electron (or hole) transfer being greater for FbC‐FbB than for ZnC‐FbB in a given solvent. For example, the Φ f and τ values for FbC‐FbB in acetone are 0.055 and 1.5 ns and in DMSO are 0.019 and 0.28 ns, whereas those for ZnC‐FbB in acetone are 0.12 and 4.5 ns and in DMSO are 0.072 and 2.4 ns. The difference in fluorescence properties of the two dyads in a given polar solvent is due to the relative energies of the lowest energy charge‐transfer states, as assessed by ground‐state redox potentials and supported by molecular‐orbital energies derived from density functional theory calculations. Controlling the extent of excited‐state quenching in polar media will allow the favorable photophysical properties of the chlorin–bacteriochlorin dyads to be exploited in vivo. These properties include very large Stokes shifts (85 nm for FbC‐FbB , 110 nm for ZnC‐FbB ) between the red‐region absorption of the chlorin and the NIR fluorescence of the bacteriochlorin (λ f = 760 nm), long bacteriochlorin excited‐state lifetime (~5.5 ns), and narrow (≤20 nm) absorption and fluorescence bands. The latter will facilitate selective excitation/detection and multiprobe applications using both intensity‐ and lifetime‐imaging techniques. 相似文献
6.
Rational Design of Emissive NIR‐Absorbing Chromophores: RhIII Porphyrin‐Aza‐BODIPY Conjugates with Orthogonal Metal–Carbon Bonds
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Jinfeng Zhou Lizhi Gai Dr. Zhikuan Zhou Wu Yang Dr. John Mack Kejing Xu Prof. Jianzhang Zhao Dr. Yue Zhao Dr. Hailin Qiu Prof. Kin Shing Chan Prof. Zhen Shen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13201-13209
The facile synthesis of Group 9 RhIII porphyrin‐aza‐BODIPY conjugates that are linked through an orthogonal Rh?C(aryl) bond is reported. The conjugates combine the advantages of the near‐IR (NIR) absorption and intense fluorescence of aza‐BODIPY dyes with the long‐lived triplet states of transition metal rhodium porphyrins. Only one emission peak centered at about 720 nm is observed, irrespective of the excitation wavelength, demonstrating that the conjugates act as unique molecules rather than as dyads. The generation of a locally excited (LE) state with intramolecular charge‐transfer (ICT) character has been demonstrated by solvatochromic effects in the photophysical properties, singlet oxygen quantum yields in polar solvents, and by the results of density functional theory (DFT) calculations. In nonpolar solvents, the RhIII conjugates exhibit strong aza‐BODIPY‐centered fluorescence at around 720 nm (ΦF=17–34 %), and negligible singlet oxygen generation. In polar solvents, enhancements of the singlet‐oxygen quantum yield (ΦΔ=19–27 %, λex=690 nm) have been observed. Nanosecond pulsed time‐resolved absorption spectroscopy confirms that relatively long‐lived triplet excited states are formed. The synthetic methodology outlined herein provides a useful strategy for the assembly of functional materials that are highly desirable for a wide range of applications in material science and biomedical fields. 相似文献
7.
Hui Liang Manlin Lu Zafar Mahmood Zheng Li Zeduan Chen Guowei Chen Prof. Ming-De Li Prof. Yanping Huo Prof. Shaomin Ji 《Angewandte Chemie (International ed. in English)》2023,62(44):e202312600
The design of efficient heavy atom-free triplet photosensitizers (PSs) based on through bond charge transfer (TBCT) features is a formidable challenge due to the criteria of orthogonal donor-acceptor geometry. Herein, we propose using parallel (face-to-face) conformation carbazole-bodipy donor-acceptor dyads (BCZ-1 and BCZ-2) featuring through space intramolecular charge transfer (TSCT) process as efficient triplet PS. Efficient intersystem crossing (ΦΔ=61 %) and long-lived triplet excited state (τT=186 μs) were observed in the TSCT dyad BCZ-1 compared to BCZ-3 (ΦΔ=0.4 %), the dyad involving TBCT, demonstrating the superiority of the TSCT approach over conventional donor-acceptor system. Moreover, the transient absorption study revealed that TSCT dyads have a faster charge separation and slower intersystem crossing process induced by charge recombination compared to TBCT dyad. A long-lived charge-separated state (CSS) was observed in the BCZ-1 (τCSS=24 ns). For the first time, the TSCT dyad was explored for the triplet-triplet annihilation upconversion, and a high upconversion quantum yield of 11 % was observed. Our results demonstrate a new avenue for designing efficient PSs and open up exciting opportunities for future research in this field. 相似文献
8.
L Ma H Guo Q Li S Guo J Zhao 《Dalton transactions (Cambridge, England : 2003)》2012,41(35):10680-10689
Visible light-harvesting cyclometalated Ir(iii) complexes with 3-(2-benzothiazoly)-7-diethylaminocoumarin as the C^N cyclometalation ligands were prepared. The ancillary N^N ligand is either 6-piperidine naphthalimide-phenanthroline (Ir-1) or 9-aminophenanthroline (Ir-3). Ir(ppy)(2)(Phen) was prepared as model complex (Ir-2). Ir-1 and Ir-3 show strong absorption of visible light (ε = 109?000 M(-1) cm(-1) or 112?000 M(-1) cm(-1) at 486 or 484 nm, respectively). All the complexes show room temperature phosphorescence with drastically different phosphorescence quantum yields (Φ(P) = 4.3%, 44.3% and 46.0% for Ir-1, Ir-2 and Ir-3, respectively). With steady state and time-resolved spectra, as well as DFT calculations, the T(1) excited states of Ir-1 and Ir-3 were proposed to be the (3)IL state, whereas the (3)MLCT state was proposed for Ir-2. Long-lived emissive triplet excited states (7.6 μs and 54.5 μs) were observed for Ir-1 and Ir-3, compared to the short T(1) excited state lifetime of Ir-2 (1.2 μs). The complexes were used as triplet photosensitizers for triplet-triplet annihilation upconversion and upconversion quantum yields (Φ(UC)) of 19.3% and 12.7% were observed for Ir-1 and Ir-3, respectively. No upconversion was observed for Ir-2 under the same experimental conditions. 相似文献
9.
Hao Zhuo Dao-Bin Guan Jia-Cun He Prof. Dr. Hai-Bing Xu Prof. Dr. Ming-Hua Zeng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16204-16211
We designed two near-infrared (NIR) lanthanide complexes [( L )2-Nd(NO3)3] ( L =TPE2-BPY for 1 , TPE-BPY for 2 ) by employing aggregation-induced emission (AIE)-active tetraphenylethylene (TPE) derivatives as sensitizers, which possessed matched energy to NdIII, prevented competitive deactivation under aggregation, even shifted the excitation window toward 600 nm by twisted intramolecular charge transfer. Furthermore, benefiting from the 4 f electron shielding effect and antenna effect, the enhanced excitation energies of the AIE-active sensitizers by structural rigidification transferred into the inert NdIII excited state through 3LMCT, affording the first aggregation-induced phosphorescence enhancement (AIPE)-active discrete NIR-emitting lanthanide complexes. As 1 equipped with more AIE-active TPE than 2 , L →Nd energy transfer efficiency in the former was higher than that in the latter under the same conditions. Consequently, the crystal of 1 exhibited one of the longest lifetimes (9.69 μs) among NdIII-based complexes containing C−H bonds. 相似文献
10.
Dirk M. Guldi Michele Maggini Gianfranco Scorrano Maurizio Prato 《Research on Chemical Intermediates》1997,23(6):561-573
A systematic fluorescence and flash photolytic investigation of a series of covalently linked fullerene / ferrocene based donor-bridge-acceptor dyads is reported as a function of the nature of the bridge between the donor site and acceptor site. The fluorescence of the investigated dyads 2 (Φrel = 0.17 × 10?4, 3 (Φrel = 0.78 × 10?4), 4 (Φrel = 1.5 × 10?4), 5 (Φrel = 0.7 × 10?4), and 6 (Φrel = 2.9 × 10?4) were substantially quenched, relative to N-methyl fulleropyrrolidine (1) (Φrel = 6.0 × 10?4). Photolysis of N-methyl fulleropyrrolidine (1) in toluene revealed formation of the excited singlet state which was followed by a rapid intersystem crossing to the excited triplet state. On the other hand, the fate of the excited singlet state of 2, 3, 4, 5, and 6 was found to be governed by rapid intramolecular quenching, with rate constants of 28×109 s?1, 6.9×109 s?1, and 3.4×109 s?1, 14×109 s?1, 2.3×109 s?1 respectively. The electron transfer process and the charge separation were confirmed by monitoring the characteristic π-radical anion bands at λmax = 400 and 1055 nm in degassed benzonitrile with τ1/2 = 1.8 μs (3) and 2.5 μs (4). 相似文献
11.
Dr. Tian-yi Li Daniel G. Shlian Prof. Dr. Peter I. Djurovich Prof. Dr. Mark E. Thompson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(20):6191-6197
A luminescent bimetallic AuI complex comprised of N-heterocyclic carbene (NHC) and carbazole (Cz) ligands, that is, (NHC’)Au(NHC)AuCz has been synthesized and studied. Both carbene ligands in the bimetallic complex act as electron acceptors in tandem to increase the energy separation between the ground and excited state, which is higher than those found in either monometallic analogue, (NHC)AuCz and (NHC’)AuCz. A coplanar geometry designed into the tandem complex ensures sufficient electronic coupling between the π-orbitals of the ligands to impart a strong oscillator strength to the singlet intra-ligand charge-transfer (1ICT) transition. Theoretical modelling indicates that the emissive ICT excited state involves both NHC ligands. The tandem complex gives blue luminescence (λmax=480 nm) with a high photoluminescent quantum yield (ΦPL=0.80) with a short decay lifetime (τ=0.52 μs). Temperature-dependent photophysical studies indicate that emission is via thermally assisted delayed fluorescence (TADF) and give a small singlet-triplet energy difference (ΔEST=50 meV, 400 cm−1) consistent with the short TADF lifetime. 相似文献
12.
Simonet Torres Guillermo Ferraudi Maria Jesus Aguirre Mauricio Isaacs Betty Matsuhiro Nancy P. Chandía Leonora Mendoza 《Helvetica chimica acta》2011,94(2):293-300
In contrast to the UV‐photoinduced ligand photoionization of the flavonoid complexes of FeIII, redox reactions initiated in ligand‐to‐metal charge‐transfer excited states were observed on irradiation of the quercetin ( 1 ) and rutin ( 2 ) complexes of CuII. Solutions of complexes with stoichiometries [CuIIL2] (L=quercetin, rutin) and [CuII2Ln] (n=1, L=quercetin; n=3, L=rutin) were flash‐irradiated at 351 nm. Transient spectra observed in these experiments showed the formation of radical ligands corresponding to the one‐electron oxidation of L and the reduction of CuII to CuI. The radical ligands remained coordinated to the CuI centers, and the substitution reactions replacing them by solvent occurred with lifetimes τ<350 ns. These are lifetimes shorter than the known lifetimes (τ>1 ms) of the quercetin and rutin radical's decay. 相似文献
13.
Chao‐Han Cheng Dr. Ruei‐Ding Hung Wen‐Zhen Wang Dr. Shie‐Ming Peng Prof. I‐Chia Chen Prof. 《Chemphyschem》2010,11(2):466-473
Transient absorption spectroscopy is used to study the excited‐state dynamics of Co3(dpa)4(NCS)2, where dpa is the ligand di(2‐pyridyl)amido. The ππ*, charge‐transfer, and d–d transition states are excited upon irradiation at wavelengths of 330, 400 and 600 nm, respectively. Similar transient spectra are observed under the experimental temporal resolution and the transient species show weak absorption. We thus propose that a low‐lying metal‐centered d–d state is accessed immediately after excitation. Analyses of the experimental kinetic traces reveal rapid conversion from the ligand‐centered ππ* and the charge‐transfer states to this metal‐centered d‐d state within 100 fs. The excited molecule then crosses to a second d–d state within the ligand‐field manifold, with a time coefficient of 0.6–1.4 ps. Because the ground‐state bleaching band recovers with a time coefficient of 10–23 ps, we propose that an excited molecule crosses from the low‐lying d–d state either directly within the same spin system or with spin crossing via the state 2B to the ground state 2A2 (symmetry group C4). In this trimetal string complex, relaxation to the ground electronic surface after excitation is thus rapid. 相似文献
14.
A Highly Efficient Near‐Infrared‐Emissive Copolymer with a N=N Double‐Bond π‐Conjugated System Based on a Fused Azobenzene–Boron Complex
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Masayuki Gon Kazuo Tanaka Yoshiki Chujo 《Angewandte Chemie (International ed. in English)》2018,57(22):6546-6551
Fused azobenzene–boron complexes (BAzs) show highly efficient near‐infrared (NIR) emission from the nitrogen–nitrogen double bond (N=N) containing π‐conjugated copolymer. Optical measurements showed that BAz worked as a strong electron acceptor because of the intrinsic electron deficiency of the N=N double bond and the boron–nitrogen (B?N) coordination which dramatically lowered the energy of the lowest unoccupied molecular orbital (LUMO) of the azobenzene ligand. The simple donor–acceptor (D–A) type copolymer of bithiophene (BT) and BAz exhibited intense photoluminescence (PL) in the NIR region both in the dilute solution (λPL=751 nm, ΦPL=0.25) and in the film (λPL=821 nm, ΦPL=0.038). The BAz monomer showed slight PL in the dilute solution, and aggregation‐induced emission (AIE) was detected. We proposed that N=N double bonds should be attractive and functional building blocks for designing π‐conjugated materials. 相似文献
15.
Ekaterina S. Smirnova Anna A. Melekhova Vladislav V. Gurzhiy Stanislav I. Selivanov Dmitrii V. Krupenya Dr. Igor O. Koshevoy Prof. Dr. Sergey P. Tunik 《无机化学与普通化学杂志》2012,638(2):415-422
Reactions of [Cu(NCMe)4]+ with stoichiometric amount of diphosphine R2P–(C6H4)n–PR2, (R = NC4H4, n = 1; R = Ph, n = 1, 2, 3) or tri‐phosphine 1, 3, 5‐(PPh2–C6H4–)3–C6H3 ligands give the corresponding di‐ or trinuclear copper(I) acetonitrile‐phosphine complexes 1 – 5 . Substitution of the labile acetonitrile groups with chelating aromatic diimines – 2, 2′‐bipyridine (bpy), 1, 10‐phenanthroline (phen), 5, 6‐dimethyl‐1, 10‐phenanthroline (dmp), 5, 6‐dibromo‐1, 10‐phenanthroline (phenBr2) – gives the corresponding substituted compounds 6 – 16 . In all complexes 1 – 16 each central CuI atom has tetrahedral configuration completed with two N‐ and two P‐donor groups. The compounds obtained were characterized using elemental analysis, ESI‐MS, X‐ray crystallography, and NMR spectroscopy. All phosphine‐diimine compounds 6 – 16 are photoluminescent at room temperature both in dichloromethane solution and in solid state (λex = 385 nm). In CH2Cl2 solution the maxima of emission bands are found in a range 540–640 nm, and in solid in a similar range 538–620 nm. Emission of 6 – 16 is assigned to the triplet excited state dominated by the charge transfer transitions with contribution of the MLCT character. 相似文献
16.
Highly Efficient Triplet Photosensitizers: A Systematic Approach to the Application of IrIII Complexes containing Extended Phenanthrolines
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Yue Lu Dr. Niamh McGoldrick Dr. Frances Murphy Dr. Brendan Twamley Xiaoneng Cui Dr. Colm Delaney Dr. Gearóid M. Ó Máille Junsi Wang Prof. Dr. Jianzhang Zhao Prof. Dr. Sylvia M. Draper 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(32):11349-11356
A series of IrIII complexes, based on 1,10‐phenanthroline featuring aryl acetylene chromophores, were prepared and investigated as triplet photosensitizers. The complexes were synthesized by Sonogashira cross‐coupling reactions using a “chemistry‐on‐the‐complex” method. The absorption properties and luminescence lifetimes were successfully tuned by controlling the number and type of light‐harvesting group. Intense UV/Vis absorption was observed for the IrIII complexes with two light‐harvesting groups at the 3‐ and 8‐positions of the phenanthroline. The asymmetric IrIII complex (with a triphenylamine (TPA) and a pyrene moiety attached) exhibited the longest lifetime. Red emission was observed for all the complexes in deaerated solutions at room temperature. Their emission at low temperature (77 K) and nanosecond time‐resolved transient difference absorption spectra revealed the origin of their triplet excited states. The singlet‐oxygen (1O2) sensitization and triplet‐triplet annihilation (TTA)‐based upconversion were explored. Highly efficient TTA upconversion (ΦUC=28.1 %) and 1O2 sensitization (ΦΔ=97.0 %) were achieved for the asymmetric IrIII complex, which showed intense absorption in the visible region (λabs=482 nm, ?=50900 m ?1 cm?1) and had a long‐lived triplet excited state (53.3 μs at RT). 相似文献
17.
The Role of Substituent Effects in Tuning Metallophilic Interactions and Emission Energy of Bis‐4‐(2‐pyridyl)‐1,2,3‐triazolatoplatinum(II) Complexes
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M. R. Ranga Prabhath Dr. Julia Romanova Prof. Richard J. Curry Prof. S. Ravi P. Silva Dr. Peter D. Jarowski 《Angewandte Chemie (International ed. in English)》2015,54(27):7949-7953
The photoluminescence spectra of a series of 5‐substituted pyridyl‐1,2,3‐triazolato PtII homoleptic complexes show weak emission tunability (ranging from λ=397–408 nm) in dilute (10?6 M ) ethanolic solutions at the monomer level and strong tunability in concentrated solutions (10?4 M ) and thin films (ranging from λ=487–625 nm) from dimeric excited states (excimers). The results of density functional calculations (PBE0) attribute this “turn‐on” sensitivity and intensity in the excimer to strong Pt–Pt metallophilic interactions and a change in the excited‐state character from singlet metal‐to‐ligand charge transfer (1MLCT) to singlet metal‐metal‐to‐ligand charge transfer (1MMLCT) emissions in agreement with lifetime measurements. 相似文献
18.
Description of excited states in [Re(Imidazole)(CO)3(Phen)]+ including solvent and spin‐orbit coupling effects: Density functional theory versus multiconfigurational wavefunction approach
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The low‐lying electronic excited states of [Re(imidazole)(CO)3(phen)]+ (phen = 1,10‐phenanthroline) ranging between 420 nm and 330 nm have been calculated by means of relativistic spin‐orbit time‐dependent density functional theory (TD‐DFT) and wavefunction approaches (state‐average‐CASSCF/CASPT2). A direct comparison between the theoretical absorption spectra obtained with different methods including SOC and solvent corrections for water points to the difficulties at describing on the same footing the bands generated by metal‐to‐ligand charge transfer (MLCT), intraligand (IL) transition, and ligand‐to‐Ligand‐ charge transfer (LLCT). While TD‐DFT and three‐roots‐state‐average CASSCF (10,10) reproduce rather well the lowest broad MLCT band observed in the experimental spectrum between 420 nm and 330 nm, more flexible wavefunctions enlarged either by the number of roots or by the number of active orbitals and electrons destabilize the MLCT states by introducing IL and LLCT character in the lowest part of the absorption spectrum. © 2016 Wiley Periodicals, Inc. 相似文献
19.
Tao Liu Bao‐Hui Xia Qing‐Chuan Zheng Xin Zhou Qing‐Jiang Pan Hong‐Xing Zhang 《Journal of computational chemistry》2010,31(3):628-638
Iridium(III) complexes with N‐heterocyclic (NHC) ligands including fac‐Ir(pmb)3 (1), mer‐Ir(pmb)3 (2), (pmb)2Ir(acac) (3), mer‐Ir(pypi)3 (4), and fac‐Ir(pypi)3 (5) [pmb = 1‐phenyl‐3H‐benzimidazolin‐2‐ylidene, acac = acetoylacetonate, pypi = 1‐phenyl‐5H‐benzimidazolin‐2‐ylidene; fac = facial, mer = meridional] were investigated theoretically. The geometry structures of 1–5 in the ground and excited state were optimized with restricted and unrestricted DFT (density functional theory) methods, respectively (LANL2DZ for Ir atom and 6‐31G for other atoms). The HOMOs (highest occupied molecular orbitals) of 1–3 are composed of d(Ir) and π(phenyl), while those of 4 and 5 are contributed by d(Ir) and π(carbene). The LUMOs (lowest unoccupied molecular orbitals) of 1, 2, 4, and 5 are localized on carbene, but that of 3 is localized on acac. The calculated lowest‐lying absorptions with TD‐DFT method based on Perdew‐Burke‐Erzenrhof (PBE) functional of 1 (310 nm), 2 (332 nm), and 3 (347 nm) have MLcarbeneCT/ILphenyl→carbeneCT (MLCT = metal‐to‐ligand charge transfer; ILCT = intraligand charge transfer) transition characters, whereas those of 4 (385 nm) and 5 (389 nm) are assigned to MLcarbeneCT/ILcarbene→carbeneCT transitions. The phosphorescences calculated by TD‐DFT method with PBE0 functional of 1 (386 nm) and 2 (388 nm) originate from 3MLcarbeneCT/3ILphenyl→carbeneCT excited states, but those of 4 (575 nm) and 5 (578 nm) come from 3MLcarbeneCT/3ILcarbene→carbeneCT excited states. The calculated results showed that the carbene and phenyl groups act as two independent chromophores in transition processes. Compared with 1 and 2, the absorptions of 4 and 5 are red‐shifted by increasing the effective π‐conjugation groups near the Ccarbene atom. We predicated that (pmb)2Ir(acac) is nonemissive, because the LUMO of 3 is contributed by the nonemissive acac ligand. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
20.
Revealing the Charge‐Transfer Interactions in Self‐Assembled Organic Cocrystals: Two‐Dimensional Photonic Applications
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Weigang Zhu Dr. Renhui Zheng Xiaolong Fu Prof. Hongbing Fu Prof. Qiang Shi Dr. Yonggang Zhen Dr. Huanli Dong Prof. Wenping Hu 《Angewandte Chemie (International ed. in English)》2015,54(23):6785-6789
A new crystal of a charge‐transfer (CT) complex was prepared through supramolecular assembly and it has unique two‐dimensional (2D) morphology. The CT nature of the ground and excited states of this new Bpe‐TCNB cocrystal (BTC) were confirmed by electron spin resonance measurements, spectroscopic studies, and theoretical calculations, thus providing a comprehensive understanding of the CT interactions in organic donor–acceptor systems. And the lowest CT1 excitons are responsible for the efficient photoluminescence (ΦPL=19 %), which can actively propagate in individual 2D BTCs without anisotropy, thus implying that the optical waveguide property of the crystal is not related to the molecular stacking structure. This unique 2D CT cocrystal exhibits potential for use in functional photonic devices in the next‐generation optoelectronic communications. 相似文献