Weak epitaxy growth of organic semiconductor thin films

The fabrication of organic semiconductor thin films is extremely important in organic electronic devices. This tutorial review-which should particularly appeal to chemists and physicists interested in organic thin-film growth, organic electronic devices and organic semiconductor materials-summarizes the method of weak epitaxy growth (WEG) and its application in the fabrication of high quality organic semiconductor thin films.

The adsorption of dopamine on gold and its interactions with iron(III) ions studied by microcantilevers

The adsorption of dopamine (DA) molecules on gold and their interactions with Fe3+ were studied by a microcantilever in a flow cell. The microcantilever bent toward the Au side with the adsorption of DA due to the change Of Surface stress induced by the intermolecular hydrogen bonds of DA or the charge transfer effect between adsorbates and the Substrate. The interaction process between DA adsorbates and Fe3+ was revealed by the deflection curves of microcantilever. As indicated by the appearance of a variation during the decline of curves, two steps were observed in the curve at relative high concentrations of Fe3+. In this case, Fe3+ reacted with DA molecules only in the outer layers and the complexes removed with solution. Then Fe3+ reacted further with DA molecules forming the surface complex in the first layer next to the gold. At this stage, the stability Of Surface complexes was time dependent, i.e., unstable initially and stable finally. This may be due to the surface complexes change from mono-dentate to bi-dentate complexes. In another case, i.e., at relative low concentration of Fe3+, only the first step was observed as indicated by the absence of a variation.

Interaction Between Tripeptide Gly-Gly-His and Cu2+ Probed by Microcantilevers

Gly-Gly-His tripeptide modified microcantilever was developed by carbodiimide attachment of the Gly-Gly-His tripeptide onto a 3-mercaptopropionic acid(MPA) modified gold surface. The interaction of peptide with Cu2+ ion was studied. At a relative high concentration of Cu2+, the cantilever bent toward the gold side initially as the N atom of imidazole ring and carboxyl group in different peptide coordinate with Cu2+, which results in a tensile surface stress. And then the reversed deflection of microcantilever was observed, which implies that the peptide-Cu2+ complex are formed with conformation transition. In another case, i.e., at a relative low concentration Of Cu2+, only the process of conformation transition was observed due to the coordination mode can not be formed initially. The influences of pH and salt concentration of the test solution on the performance of the sensor were studied. The results show that the maximum deflection was obtained at pH 7 and the bonding Of Cu2+ to the Gly-Gly-His tripeptide was inhibited due to the formation Of CuClx2-x.

Structural stability and electronic state of transition metal trimers

Ground state geometries were searched for transition metal trimers Sc-3, Y-3, La-3, Lu-3, Ti-3, Zr-3, and Hf-3 by density functional methods. For all the studied trimers, our calculation indicates that the ground state geometries are either equilateral triangle (Zr-3 and Hf-3) or near equilateral triangle (Ti-3, Sc-3, Y-3, La-3, and Lu-3). For rare earth trimers Sc-3, Y-3, La-3, and Lu-3, isosceles triangle (near equilateral triangle) at quartet state is the ground state. Isosceles triangle at doublet state is the competitive candidate for the ground state. For Zr-3 and Hf-3, equilateral triangle at singlet state is the most stable. For Ti-3, isosceles triangle (near equilateral triangle) at quintet state gives the ground state. For Sc-3, Zr-3, and Hf-3, where experimental results are available, the predicted geometries are in agreement with experiment in which the ground state is equilateral triangle (Zr-3) or fluxional (Sc-3 and Hf-3). For Y-3, the calculated geometry is in agreement with experimental observation and previous theoretical study that Y-3 is a bent molecule for the ground state.

Synthesis and properties of novel polyimides derived from 2,2 ',3,3 '-benzophenonetetracarboxylic dianhydride

A new synthetic route to 2,2',3,3'-BTDA (where BTDA is benzophenonetetracarboxylic dianhydride), an isomer of 2,3',3',4'-BTDA and 3,3',4,4'-BTDA, is described. Single-crystal X-ray diffraction analysis of 2,2',3,3'-BTDA has shown that this dianhydride has a bent and noncoplanar structure. The polymerizations of 2,2',3,3'-BTDA with 4,4'-oxydianiline (ODA) and 4,4'-bis(4-aminophenoxy)benzene (TPEQ) have been investigated with a conventional two-step process. A trend of cyclic oligomers forming in the reaction of 2,2',3,3'-BTDA and ODA has been found and characterized with IR, NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and elemental analyses. Films based on 2,2',3,3'-BTDA/TPEQ can only be obtained from corresponding polyimide (PI) solutions prepared by chemical imidization because those from their polyamic acids by thermal imidization are brittle. PIS from 2,2',3,3'-BTDA have lower inherent viscosities and worse thermal and mechanical properties than the corresponding 2,3',3',4'-BTDA- and 3,3',4,4'-BTDA-based PIs. PIs from 2,2',3,3'-BTDA and 2,3',3',4'-BTDA are amorphous, whereas those from 3,3',4,4'-BTDA have some crystallinity, according to wide-angle X-ray diffraction.

Titanium complexes with novel triaryl-substituted phosphinimide ligands: Synthesis, structure and ethylene polymerization behavior

A series of titanium phosphinimide complexes [Ph2P(2-RO-C6H4)(2)TiCl2 (7, R = CH3; 8, R = CHMe2) and (PhP(2-Me2CHOC6H4)][THF]TiCl3 (9) have been prepared by reaction of TiCl4 with the corresponding phosphinimines under dehalosilylation. The structure of complex 9 has been determined by X-ray crystallography, and a solvent molecule THF was found to be coordinated with the central metal and the Ti-O bond was consistent with the normal Ti-O (donor) bond length. The complexes 7 and 8 displayed inactive to ethylene polymerization, and the complex 9 displayed moderate activity in the presence of modified methylaluminoxane (MMAO) or i-BU3Al/Ph3CB(C6F5)(4), and this should be partly attributed to coordination of THF with titanium and the steric effect of two iso-propoxyl. And catalytic activity up to 32.2 kg-PE/(mol-Ti h bar) was observed.

Synthesis, structure and ethylene polymerization of group 4 complexes with phosphinoamide ligands

Group 4 complexes containing diphosphinoamide ligands [Ph2PNR](2)MCl2 (3: R = Bu-t, M = Ti; 4: R = Bu-t, M = Zr; 5: R = Ph, M = Ti; 6: R = Ph, M = Zr) were prepared by the reaction Of MCl4 (M = Ti; Zr) with the corresponding lithium phosphinoamides in ether or THF. The structure of [(Ph2PNBu)-Bu-t](2)TiCl2 (3) was determined by X-ray crystallography. The phosphinoamides functioned as eta(2)-coordination ligands in the solid state and the Ti-N bond length suggests it is a simple single bond. In the presence of modified methylaluminoxane or i-Bu3Al/Ph3BC(C6F5)(4), catalytic activity of up to 59.5 kg PE/mol cat h bar was observed.

Titanium and zirconium complexes with aminoiminophosphorane ligands

A series of titanium and zirconium complexes based on aminoiminophosphorane ligands [Ph2P(Nt-Bu)(NR)](2)MCl2 (4, M = Ti, R = Ph; 5, M = Zr, R = Ph; 6, M = Ti, R = SiMe3; 7, M = Zr, R = SiMe3) have been synthesized by the reaction of the ligands with TiCl4 and ZrCl4. The structure of complex 4 has been determined by X-ray crystallography. The observed very weak interaction between Ti and P suggests partial pi-electron delocalization through both Ti and P. The complexes 4-7 are inactive for ethylene polymerization in the presence of modified methylaluminoxane (MMAO) or i-Bu3Al-Ph3CB(C6F5)(4) under atmospheric pressure, and is probably the result of low monomer ethylene concentration and steric congestion around the central metal.

In situ ethylene homopolymerization and copolymerization catalyzed by zirconocene catalysts entrapped inside functionalized montmorillonite

Ethylene homopolymerizations and copolymerizations were catalyzed by zirconocene catalysts entrapped inside functionalized. montmorillonites that had been rendered organophilic via the ion exchange of the interlamellar cations of layered montmorillonite with hydrochlorides Of L-amino acids (AAH(+)Cl(-)) or their methyl esters (MeAAH(+)Cl(-)), with or without the further addition of hexadecyltrimethylammonium bromide (C16H33N+Me3Br-; R4N+Br-). In contrast to the homogeneous CP2ZrCl2/methylaluminoxane catalyst for ethylene homopolymerizations and copolymerizations with 1-octene, the intercalated Cp2ZrCl2 activated by methylaluminoxane for ethylene homopolymerizations and copolymerizations with 1-octene proved to be more effective in the synthesis of polyethylenes with controlled molecular weights, chemical compositions and structures, and properties, including the bulk density. The effects of the properties of the organic guests on the preparation and catalytic performance of the intercalated zirconocene catalysts were studied.

Ethylene polymerization by self-immobilized neutral nickel catalysts bearing allyl groups

[Ni(Ph)(PPh3)(N,O)] complexes containing phenyliminophenolato ligands (N,O) (1: N,O = A; 2: N,O = B; 3: N,O = Q 4: N,O = D; 5: N,O = E) have been synthesized and characterized. The molecular structure of 4 was determined by single-crystal X-ray analysis. Complexes 2-5 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization without the use of co-catalysts. The high ethylene polymerization activities of ca. 10(5) g.PE mol(-1) Ni.h(-1) and high molecular weight (M-w approximate to 10(5)) of polyethylene could be accomplished by changing the ligand structures and reaction conditions. The self-immobilization of catalysts brings about a dramatic increase in the catalytic activities of ethylene polymerization.

Polymer immobilized silane bridged metallocene catalysts for ethylene polymerization

Ansa-zirconocene complex with an allyl substituted silane bridge [(CH2=CHCH2)CH3Si(C5H4)(2)]ZrCl2 (1a) has been synthesized and characterized. The molecular structure of la has been determined by X-ray crystallographic analysis. The polymer immobilized metallocene catalyst 1b is prepared by the co-polymerization of la with styrene in the presence of radical initiator. The result of ethylene polymerization showed that the polymer immobilized metallocene catalyst kept high activity for ethylene polymerization and was a potential supported catalyst for olefin polymerization.

Synthesis of C-1 bridge-containing metallocene catalysts and their catalytic activities for olefin polymerization

The synthesis and characterization of metallocene complexes which can be used as catalysts in the presence of MAO for olefin polymerization were discussed in the present paper. The metallocene complexes have been characterized by IR, H-1 NMR, EI-MS spectra and element analyses; The catalytic features of Olefin polymerization were studied under different conditions. Metallocenes in which metals is Ti had no activity for ethylene polymerization, Polymers with different features can be obtained by using different catalysts.

1,1 '-di(tert-butyl)metallocenium cations. The x-ray crystal structures of [M((C5H4Bu)-Bu-t)(2)]PF6 (M = Fe, Co) and [Co((C5H4Bu)-Bu-t)(2)](2)CoCl4

The hexafluorophosphate salts [Fe((C5H4Bu)-Bu-t)(2)]PF6 (1) and [Co((C5H4Bu)-Bu-t)(2)]PF6 (2) crystallize in isotypic structures with centrosymmetric cations which have a staggered (transoid) conformation of the exactly parallel ring Ligands (conformational angle tau = 180 degrees). The tetrachlorocobaltate salt, [CO((C5H4Bu)-Bu-t)(2)](2)CoCl4 (3), contains one almost eclipsed (tau = 140.4 degrees) and one almost staggered (tau = 101.4 degrees) cobaltocenium cation; in both cases, the cyclopentadienyl ring planes are slightly inclined (by alpha = 5.4 degrees and 4.1 degrees, respectively) to give more room to the tert-butyl substituents which are bent away from the metal in all three complexes 1 - 3.

Molecular and supramolecular deformations and disclinations in a liquid crystalline copolyether thin films under an electrostatic field

An alignment study of a liquid crystalline copolyether TPP-7/11(5/5) thin films has been carried out in a 10 kV . cm(-1) electrostatic field parallel to the thin film surface normal. This copolyether possesses a negative dielectric anisotropy. The chain molecules are homogeneously aligned in the electric field and they form two-dimensionally ordered lamellae in a tilted columnar phase when the samples were cooled to room temperature. It is observed that the chain molecules are splayed to form bent lamellae and the chain direction is perpendicular to the tangential direction of the lamellar surfaces. These lamellae thus become replicas of the chain orientation, Due to the flexoelectric effect and density fluctuation on the thin film free surface, disclinations having topological strength s = 1, c = pi /4 and defect walls form. These s = 1 disclinations possesses both left- and right-handednesses. Discussion of the defect formations have been attempted.

New development of organolanthanide complexes containing chalcogenide ligands

This article is to present and outline new approaches to chalcogen coordination chemistry from the organolanthanides point of view.