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HOMO Energy Level (homo + energy_level)
Selected AbstractsRoyal crown-shaped electride Li3 -N3 -Be containing two superatoms: New knowledge on aromaticityJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 8 2006Zhi-Ru Li Abstract The structure and aromaticity of a royal crown-shaped molecule Li3 -N3 -Be are studied at the CCSD(T)/aug-cc-pVDZ level. This molecule is a charge-separated system and can be denoted as Li32+N33,Be+. It is found that the Li32+ ring exhibits aromaticity mainly because the Li32+ ring can share the ,-electron with the N3,3 ring. The 4n+2 electron counter rule can be satisfied for the Li32+ subunit if the shared , valence electron of N33, subunit is also taken into account. This new knowledge on aromaticity of a ring from the interactions between subunits is revealed first time in this paper. Li3 -N3 -Be can be also regarded as a molecule containing two superatoms (Li3 and N3), which may be named as a "superomolecule." Li3 -N3 -Be is a new metal,nonmetal,metal type sandwich complex. The N33, trianion in the middle repulses the electron clouds of the two metal subunits (mainly to the Li3 superatom) to generate an excess electron, and thus Li3 -N3 -Be is also an electride. This phenomenon of the repulsion results in: (a) the HOMO energy level increased, (b) the electron cloud in HOMO distended, (c) the area of the negative NICS value extended, and (d) the VIE value lowered. So the superomolecule Li3 -N3 -Be is not only a new metal,nonmetal,metal type sandwich complex but also a new type electride, which comes from the interaction between the alkali superatom (Li3) and the nonmetal superatom (N3). © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 986,993, 2006 [source] Synthesis and applications of low-bandgap conjugated polymers containing phenothiazine donor and various benzodiazole acceptors for polymer solar cellsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010Harihara Padhy Abstract A series of soluble donor-acceptor conjugated polymers comprising of phenothiazine donor and various benzodiazole acceptors (i.e., benzothiadiazole, benzoselenodiazole, and benzoxadiazole) sandwiched between hexyl-thiophene linkers were designed, synthesized, and used for the fabrication of polymer solar cells (PSC). The effects of the benzodiazole acceptors on the thermal, optical, electrochemical, and photovoltaic properties of these low-bandgap (LBG) polymers were investigated. These LBG polymers possessed large molecular weight (Mn) in the range of 3.85,5.13 × 104 with high thermal decomposition temperatures, which demonstrated broad absorption in the region of 300,750 nm with optical bandgaps of 1.80,1.93 eV. Both the HOMO energy level (,5.38 to ,5.47 eV) and LUMO energy level (,3.47 to ,3.60 eV) of the LBG polymers were within the desirable range of ideal energy level. Under 100 mW/cm2 of AM 1.5 white-light illumination, bulk heterojunction PSC devices containing an active layer of electron donor polymers mixed with electron acceptor [6,6]-phenyl-C61 -butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71 -butyric acid methyl ester (PC71BM) in different weight ratios were investigated. The best performance of the PSC device was obtained by using polymer PP6DHTBT as an electron donor and PC71BM as an acceptor in the weight ratio of 1:4, and a power conversion efficiency value of 1.20%, an open-circuit voltage (Voc) value of 0.75 V, a short-circuit current (Jsc) value of 4.60 mA/cm2, and a fill factor (FF) value of 35.0% were achieved. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] The Origin of the Improved Efficiency and Stability of Triphenylamine-Substituted Anthracene Derivatives for OLEDs: A Theoretical Investigation,CHEMPHYSCHEM, Issue 17 2008Bing Yang Dr. Abstract Herein, we describe the molecular electronic structure, optical, and charge-transport properties of anthracene derivatives computationally using density functional theory to understand the factors responsible for the improved efficiency and stability of organic light-emitting diodes (OLEDs) with triphenylamine (TPA)-substituted anthracene derivatives. The high performance of OLEDs with TPA-substituted anthracene is revealed to derive from three original features in comparison with aryl-substituted anthracene derivatives: 1) the HOMO and LUMO are localized separately on TPA and anthracene moieties, respectively, which leads to better stability of the OLEDs due to the more stable cation of TPA under a hole majority-carrier environment; 2) the more balanceable hole and electron transport together with the easier hole injection leads to a larger rate of hole,electron recombination, which corresponds to the higher electroluminescence efficiency; and 3) the increasing reorganization energy for both hole and electron transport and the higher HOMO energy level provide a stable potential well for hole trapping, and then trapped holes induce a built-in electric field to prompt the balance of charge-carrier injection. [source] Synthesis, Optical and Electrochemical Properties of Novel 1,8-Naphthalimide Derivatives Containing Triphenylamine Moiety as Hole-Transporting GroupsCHINESE JOURNAL OF CHEMISTRY, Issue 4 2008Lin-Bo LI Abstract A series of novel 1,8-naphthalimide derivatives have been synthesized via Suzuki cross-coupling and characterized by 1H NMR, IR and elemental analysis, with their luminescent properties, quantum yields and electronic properties also presented. These compounds exhibited orange fluorescence with the maximum wavelengths ranging from 584 to 610 nm and lower HOMO energy level. [source] 1,3-Diphenyl-5-(9-phenanthryl)-2-pyrazoline(DPPhP): An Excellent Hole-Transport Material for Use in Organic Light-Emitting DiodesCHINESE JOURNAL OF CHEMISTRY, Issue 10 2002Chang-Qi Ma Abstract An excellent hole-transport material, 1, 3-diphenyil-5-(9-phenanthryl)-2-pyrazoline (DPPhP) for OLEDs was studied. This compound not only offers high glass transition temperature (Tg = 96 °C), good film forming ability, and high HOMO energy level, but also displays excellent hole-transport property. The electroluminescent device with a simple structure of ITO/DPPhP (60 nm)/AlQ (60 nm)/LiF (0.8 nm)/Al shows an external quantum efficiency as high as 1.6%. [source] Asymmetrical Fluorene[2,3- b]benzo[d]thiophene Derivatives: Synthesis, Solid-State Structures, and Application in Solution-Processable Organic Light-Emitting DiodesCHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2009Chunyan Du Abstract A series of novel asymmetrical fused compounds containing the backbone of fluorene[2,3- b]benzo[d]thiophene (FBT) were effectively synthesized and fully characterized. Single-crystal X-ray studies demonstrated that the length of the substituent side chains greatly affects the solid-state packing of the obtained fused compounds. DFT, photophysical, and electrochemical studies all showed that the FBTs have large band gaps, low-lying HOMO energy levels, and therefore good stability toward oxidation. Moreover, the substituents strongly influence the fluorescence properties of the resulting FBT derivatives. The di- n -hexyl compound exhibits intense fluorescence in solution with the highest quantum yield of up to 91,%. Solution-processed green phosphorescent organic light-emitting diodes with the di- n -butyl derivative as the host material exhibited a maximum brightness of 14,185,cd,m,2 and a luminescence efficiency of 12,cd,A,1. [source] UV/Vis to NIR Photoconduction in Cyclopalladated ComplexesCHEMISTRY - AN ASIAN JOURNAL, Issue 7 2009Nicolas Godbert Abstract Funky discotics: Photoconductivity is measured in newly synthesized cyclopalladated metallomesogens exhibiting hexagonal columnar mesophases at room temperature. The tuning of the HOMO/LUMO energy levels by modification of the chain/core linkage (ester 1 vs ether 2) makes compound 2 photoconductive across the whole UV/Vis/NIR range. The incorporation of a rigid core, formed by a cyclopalladated azobenzene fragment bonded to an ancillary Schiff base ligand, into molecules with 12 or 11 peripheral alkyl chains has been successfully achieved. These new complexes, 1 and 2, respectively, are columnar liquid crystals between room temperature and about 50,°C. Both cyclometallated and ancillary ligands have been polyalkylated through either aryl ester (electron-withdrawing group) or aryl ether (electron-releasing group) linkages, in order to tune the HOMO/LUMO energy levels. The photoconductive properties of 1 and 2 have been studied as a function of their absorption properties before and after annealing, from the UV/Vis to NIR region. Compared with the reference compounds, tris-alkynyl benzene discotics, these new materials gave similar performances (,/I,8×10,13,S,cm,W,1 with E=10,V,,m,1 at ,=370,nm). Moreover, complex 2 shows a normalized photoconductivity ,/I=8.5×10,13,S,cm,W,1 at ,=760,nm. Organic photoconductors in such a high wavelength spectral range are not common and are usually assembled by mixing dyes with organic semiconductors. [source] | ||||||||||