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

A simple miniaturised photometrical method for rapid determination of nitrate and nitrite in freshwater

A rapid, simple miniaturised photometrical method was developed for the determination of nitrate and/or nitrite in freshwater samples. All procedures, including sample buffering, reduction by copperised cadmium granules, colour development and absorbance determination, were completed in a 96-well microplate. The factors governing the nitrate reduction and its recovery were investigated in detail, and the optimised analysing conditions were established. Nitrate was quantitatively reduced by copperised cadmium granules with a high reduction efficiency (96.59 +/- 0.96%). The proposed method gave a linear calibration ranging from 0.01 to 1.50 mg L-1 for NO2--N and 0.02 to 1.50 mg L-1 for NO3--N. The detection limits for nitrite and nitrate were 2 and 4 mu g L-1, respectively. The proposed method allowed at least 48 samples to be simultaneously analysed in duplicate, with good precision, within 90 min for nitrate and 30 min for nitrite, and was successfully applied to actual freshwater sample analysis with a recovery of 98.02 +/- 1.04% for nitrite and 99.72 +/- 1.39% for nitrate. This method produced accurate results comparable to standard methods, provided a much higher sample throughput than conventional methods and could be routinely used in actual freshwater sample monitoring. (C) 2010 Elsevier B.V. All rights reserved

INFLUENCE OF LINEAR ALKYLBENZENE SULFONATE (LAS) AS ORGANIC COSOLVENT ON LEACHING BEHAVIOR OF PCDD/FS FROM FLY-ASH AND SOIL

The leaching of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was measured in soil and standard fly ash column eluted with pure water and linear alkylbenzene sulfonate (LAS)- water. The data obtained were used to evaluate the leachability of PCDD/Fs from waste dump like incineration residual slag and fly ash deposition. The leaching rate was shown to be increased significantly by using LAS water. The leachate contents of PCDD/Fs were above their known water solubility. Concentration of PCDD/Fs in the leachates as well as the relative leaching (calculated on the fly ash content) increased with increasing chlorinating degree and decreasing water solubility. LAS above the critical micelle concentration (CMC) probably enhances PCDD/Fs solubility

2-(3-Oxo-3,4-dihydro-2H-1,4-benzothiazin-4-yl)acetohydrazide

In the title compound, C10H11N3O2S, the thiazine ring exists in a conformation intermediate between twist-boat and half-chair. The dihedral angle between the mean plane of the thiazine ring and the hydrazide group is 89.45 (13)degrees. In the crystal, N-H center dot center dot center dot O hydrogen bonds link the molecules into (100) sheets and weak C-H center dot center dot center dot O interactions further consolidate the packing.Higher Education Commission of Islamabad, Pakistan [042-120614-PS2-128

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

NC unit trapped by fullerenes: a density functional theory study on Sc3NC@C-2n (2n=68, 78 and 80)

Endohedral metallofullerenes (EMFs) with a trapped cluster size larger than four are rather scarce. Inspired by a recent experimental observation, we explored the possibility of encapsulating an unusual Sc3NC unit in three representative fullerene cages, namely, C-68, C-78 and C-80, by means of density functional computations. The geometries, electronic and electrochemical redox properties of the corresponding EMFs, Sc3NC@C-2n (2n = 68, 78 and 80), were investigated. These novel EMFs all have very favorable binding energies, implying a considerable possibility for experimental realization. The recently observed m/z = 1121 peak in the mass spectroscopy was characterized as Sc3NC@C-80. Notably the lowest-energy isomer of Sc3NC@C-78 has a non-IPR C-78 outer cage, the possibility to accommodate five atoms inside a fullerene as small as C-68 is also intriguing. Moreover, the intracluster and metal-cage covalent interactions were revealed by a quantum theory of atoms in molecules study. Infrared absorption spectra and C-13 nuclear magnetic resonance spectra were also computed to assist future experimental characterization.NSFC [20773018, 20873067, 20673088, 20425312, 20721001, 20423002]; 973 Program [2007CB815307]; NSF, USA [CHE-0716718]; Institute for Functional Nanomaterials (NSF) [0701525]; US Environmental Protection Agency (EPA) [RD-83385601

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

Spin crossover in the cyanide-bridged Mo(V)Mn(III) single-chain magnet containing Fe(II) cations

A 1D Mo(V)Mn(III) chain compound balanced by {Fe[ HC(3,5-Me(2)pz)(3)](2)}(2+) dications was prepared. This complex displays a typical single-chain magnet character associated with the Mo(V)Mn(III) chain and a spin crossover phenomenon arising from cationic Fe(II) subunits. The spin crossover behavior tends to slightly affect single-chain magnetic properties at low temperature.National Research Foundation of Korea; Korean Government[2011-0003264]; Ministry of Education, Science and Technology[NRF20110018396

Riding over the Kuroshio from the South to the East China Sea: Mixing and transport of DIC

Export of dissolved inorganic carbon (DIC) to adjoining oceans enhances the potential of CO2 sequestration in marginal seas. By using a series of measured DIC depth profiles and reported flow transports, we estimated that the intermediate outflow (100-600 m) from the South China Sea is capable of transporting 6.5 +/- 4.1 Tg (1 Tg = 10(12) g) of biologically mediated carbon (DICbio) annually to the East China Sea (ECS) via the northwardly flowing Kuroshio current. The mixing and transport of these DIC-rich waters would raise 3% and 16% of DIC/TA ratio and the Revelle factor of the adjoining seawaters, respectively. Upon upwelling onto the ECS shelf, these DIC-rich waters would counteract the potential of CO2 uptake of shelf waters that might have been enhanced by the accompanying increase in nutrient inputs, thus complicating assessment of the ECS as a net CO2 source or sink. Citation: Sheu, D. D., W.-C. Chou, C. T. A. Chen, C.-L. Wei, H.-L. Hsieh, W.-P. Hou, and M. Dai (2009), Riding over the Kuroshio from the South to the East China Sea: Mixing and transport of DIC, Geophys. Res. Lett., 36, L07603, doi:10.1029/2008GL037017.National Science Council (Taiwan) [NSC-95-2611-M-110-003, NSC-96-2611-M-110-004

Crystal structure of 2-(2-naphthyl)-4,6-dimethylpyrimidine, C(16)H(14)N(2)

C(16)H(14)N(2), monoclinic, P12(1)/c1 (no. 14), a = 8.387(1) angstrom, b = 17.453(3) angstrom, c = 8.694(1) angstrom, beta = 93.092(2)degrees, V = 1270.8 angstrom(3), Z = 4, R(gt)(F) = 0.046, wR(ref)(F(2)) = 0.129, T = 294 K.program for innovation of science and technology talents of Henan Province[104200510022]; program for science and technology leaders of Zhengzhou City[10LJRC174]; Doctor Foundation[D09004]; program for innovative research team of Henan Institute of Engineering[2009IRTHNIE05