Nuclear tunneling effects of charge transport in rubrene, tetracene, and pentacene

The mechanism of charge transport in organic materials is still controversial from both experimental and theoretical perspectives. At room temperature, molecular deformations interact strongly with the charge carrier both through intermolecular and intramolecular phonons, suggesting a thermally activated hopping mechanism as described by the Marcus electron transfer theory. However, several experimental measurements have indicated that the electronic transport behaves in a "bandlike" manner, as indicated by a decrease in mobility with increasing temperature, in contradiction to the Marcus description. Bandlike first-principles calculations based on the Holstein-Peierls model tend to overestimate the charge mobility by about 2 orders of magnitude. Here, a hopping model is derived that not only quantitatively describes the charge mobility but also explains the observed bandlike behavior. This model uses the quantum version of charge-transfer theory coupled with a random-walk simulation of charge diffusion. The results bridge the gap between the two extreme mechanisms. This first-principles method predicts the room-temperature hole mobilities to be 2.4, 2.0, and 0.67 cm(2)/V s, for rubrene, pentacene, and tetracene, respectively, in good agreement with experiment

Charge transfer rates in organic semiconductors beyond first-order perturbation: From weak to strong coupling regimes

Semiclassical Marcus electron transfer theory is often employed to investigate the charge transport properties of organic semiconductors. However, quite often the electronic couplings vary several orders of magnitude in organic crystals, which goes beyond the application scope of semiclassical Marcus theory with the first-order perturbative nature. In this work, we employ a generalized nonadiabatic transition state theory (GNTST) [Zhao , J. Phys. Chem. A 110, 8204 (2004)], which can evaluate the charge transfer rates from weak to strong couplings, to study charge transport properties in prototypical organic semiconductors: quaterthiophene and sexithiophene single crystals. By comparing with GNTST results, we find that the semiclassical Marcus theory is valid for the case of the coupling < 10 meV for quaterthiophene and < 5 meV for sexithiophene. It is shown that the present approach can be applied to design organic semiconductors with general electronic coupling terms. Taking oligothiophenes as examples, we find that our GNTST-calculated hole mobility is about three times as large as that from the semiclassical Marcus theory. The difference arises from the quantum nuclear tunneling and the nonperturbative effects.Ministry of Science and Technology of China [2006CB806200, 2006CB0N0100, 2009CB623600]; NSFC [20833004

Aggregation of an anionic porphyrin with chiral metal complexes and the competitive binding influences of a surfactant and a polyelectrolyte

The non-covalent interactions of chiral metal complexes with the achiral 5,10,15,20-tetrakis (4-sulonatophenyl) porphyrin (H(4)TTPS(2-)) have been investigated by UV-vis and circular dichroism (CD) spectra. The results show that under acidic environments, only the chiral complex cations ([CoBr(NH(3))(en)(2)](+), [Co(en)(3)](3+), [Ru(phen)(3)](2+)) could interact with H(4)TTPS(2-) to form chiral aggregates, accompanied with the metal-centered chirality information transferred to the formed J-aggregates. However, the chiral complex anion ([Co(edta)](-)) does not cause the self-assembly process. The competitive binding interactions between an achiral water-soluble cationic surfactant (N-hexadecyltrimethyl ammonium chloride, CTAC) and a cationic polyelectrolyte (polyallylamine, PAA) with the chiral metal complex H(4)TTPS(2-) J-aggregates, respectively, were also investigated. It was found that chiral-symmetry-breaking phenomena occur in the cationic surfactant induced event. In the case of a cationic polyelectrolyte, it could change the conformational flexibility of the H(4)TTPS(2-) aggregates. These results may lead us to understand the possible mechanism of the supramolecular self-assembly process by the non-covalent interactions.National Natural Science Foundation of China[20973136, 20877099, 20972183]; State Key Laboratory of Natural and Biomimetic Drugs[20080208]; Hunan High Education Research Fund[06C068]; GUCAS (A B); Ministry of Science and Technology of China[2008AA100801]; Guangdong Province[2010B090300031]; CAS[2010B090300031

Transformation, memorization and amplification of chirality in cationic Co(III) complex-porphyrin aggregates

Lambda-and Delta-enantiomers of cis-[CoBr(NH3)(en)(2)]Br-2 were obtained by absolute asymmetric synthesis. The interactions between the achiral 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) and two chiral cationic Co(III) complexes were studied by UV-vis spectroscopy, circular dichroism (CD), fluorescence spectroscopy and atomic force microscopy (AFM). It was found that the cationic Co( III) complexes can induce the formation of chiral porphyrin J-aggregates, that the metal-centered chirality can be transferred to the J-aggregates, and that the chirality was able to be memorized and amplified in the porphyrin J-aggregates. Therefore, this should be a good chiral model for understanding similar processes in physical and biological systems.National Natural Science Foundation of China [20773098, 20877099, 20972183]; State Key Laboratory of Natural and Biomimetic Drugs [20080208]; GUCAS [065101HM03 B

Synthesis of micro-nano hierarchical structured LiFePO(4)/C composite with both superior high-rate performance and high tap density

Efforts were made to synthesize LiFePO(4)/C composites showing both high rate capability and high tap density. First, monoclinic phase FePO(4)center dot 2H(2)O with micro-nano hierarchical structures are synthesized using a hydrothermal method, which are then lithiated to LiFePO(4)/C also with hierarchical structures by a simple rheological phase method. The primary structures of FePO(4 center dot)2H(2)O are nanoplates with similar to 30 nm thickness, and the secondary structures of the materials are intertwisted micro-scale rings. The LiFePO(4)/C materials lithiated from these specially structured precursors also have hierarchical structures, showing discharge capacities of more than 120, 110, and 90 mAh g(-1) at rates of 5 C, 10 C and 20 C, respectively, and high tap density of 1.4 g cm(-3) as cathode materials for lithium ion batteries. Since tap density is an important factor that needs to be considered in fabricating real batteries in industry, these hierarchical structured LiFePO(4)/C moves closer to real and large-scale applications.National Science Foundation of China[20901062]; Central Universities[2082002

Thermodynamic assessments of the Er-Sb and Sb-Tm systems

通讯作者：E-mail address: [email protected] (X.J. Liu).By using the calculation of phase diagrams (CALPHAD) method, thermodynamic assessments of the Er-Sb and Sb-Tm systems were carried out based on the available experimental data including thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, hcp, and rhombohedral phases in the Er-Sb and Sb-Tm systems were modeled by the substitutional solution model with the Redlich-Kister formula, and the intermetallic compounds (Er(5)Sb(3), alpha ErSb, beta ErSb, ErSb(2), Sb(2)Tm, alpha SbTm, beta SbTrn, alpha Sb(3)Tm(5), and beta Sb(3)Tm(5) phases) in these two binary systems were described by the sublattice model. An agreement between the present calculated results and experimental data was obtained.National Natural Science Foundation of China 51031003 Ministry of Education of China 707037 Ministry of Science and Technology of China 2009DFA52170 2009AA03Z101 Doctoral Foundation of Qingdao University of Science and Technolog

Planar Quinary Cluster inside a Fullerene Cage: Synthesis and Structural Characterizations of Sc3NC@C-80-I-h

The endohedral fullerene Sc3NC@C-80-I-h has been synthesized and characterized; it has an unprecedented planar quinary cluster in a fullerene cage. It is also the first chemical compound in which the presence of an unprecedented (NC)(3-) trianion has been disclosed. The fascinating intramolecular dynamics in Sc3NC@C-80-I-h enables the whole molecule to display high polarity and promising ferroelectricity. This finding inspires the possibility that such a planar quinary cluster may be useful in constructing many other endohedral fullerenes.973 Program [2006CB300402, 2007CB815307]; NSFC [20821003, 20702053, 20973137, 20673088, 20425312, 20721001, 20423002]; Ministry of Science and Technology [2008ZX05013-004

Site-selective DNA hydrolysis induced by a metal-free peptide nucleic acid-cyclen conjugate

A metal-free artificial restriction DNA cutter which is composed of cyclen and classical peptide nucleic acid (PNA) was synthesized. Analysis of DNA cleavage products indicates the site-selective hydrolysis.National Science Foundation of China[20725206, 20732004, 20972104]; Program for Changjiang Scholars and Innovative Research Team in University; Ministry of Education in China; Scientific Fund of Sichuan Province for Outstanding Young Scientist; DAA

Effects of anharmonicity on diffusive-controlled symmetric electron transfer rates: From the weak to the strong electronic coupling regions

The approach for the diffusive-controlled electron transfer rates [W. Zhu and Y. Zhao, J. Chem. Phys. 126, 184105 (2007)], which is modeled after the Sumi-Marcus theory, is applied to symmetric electron-transfer reactions in a solvent environment with anharmonic potential functions. The electron-transfer rates are evaluated using the quantum R-matrix theory for dealing with the intramolecular vibrational motions and imaginary-time split operator technique for solving the diffusive equations, thereby taking explicit account of the weak-to-strong electronic couplings. The effect of anharmonicity for both the solvent and intramolecular vibrational degrees of freedom are investigated. It is found that the anharmonicity of the intramolecular modes always enhances the rate while the solvent anharmonicity decreases the rate, compared with the harmonic modes. The possible mechanisms have been clarified.National Nature Science Foundation of China [20773115, 20833004]; National Key Basic Research Foundation Program of China [2007CB815204

Non-Condon nature of fluctuating bridges on nonadiabatic electron transfer: Analytical interpretation

Rigorous expressions for the calculation of nonadiabatic electron transfer rates are presented in closed forms for donor-acceptor systems incorporated fluctuating bridges and their non-Condon electronic couplings. In high temperature limit, they show a similar property to the Marcus formula. However, the Marcus parabolic with respect to the driving force is shifted for the exponential coupling while it becomes an overlap of several Gaussian functions for the linear coupling. Furthermore, the effective couplings are exponentially and linearly dependent on temperature and the squared frequencies of bridge modes for the exponential and linear couplings, respectively.National Science Foundation of China [20673104, 20773115, 20833004]; National Key Basic Research Foundation Program of China [2007CB815204