Studies On The Electrical Properties Of Some Crystalline Organic Compounds And Conducting Polymers

Solid electrolytes for applications like chemical sensing, energy storage, and conversion have been actively investigated and developed since the early sixties. Although of immense potential, solid state protonic conductors have been ignored in comparison with the great interest that has been shown to other ionic conductors like lithium and silver ion conductors. The non-availability of good, stable protonic conductors could be partly the reason for this situation. Although organic solids are better known for their electrical insulating character, ionic conductors of organic origin constitute a recent addition to the class of ionic conductors. However, detailed studies (N1 such conductors are scarce. Also the last decade has witnessed an unprecedented boom in research on organic "conducting polymers". These newly devised materials show conductivity spanning from insulator to metallic regimes, which can be manipulated by appropriate chemical treatment. They find applications in devices ranging from rechargeable batteries to "smart windows". This thesis mainly deals with the synthesis and investigations on the electrical properties of (i) certain organbc protonic conductors derived from ethylenediamine and (ii) substituted polyanilines

Structural, magnetic and electrical properties of the sol-gel prepared Li0.5Fe2.5O4 fine particles

Fine particles of lithium ferrite were synthesized by the sol-gel method. By subsequent heat treatment at different temperatures, lithium ferrites of different grain sizes were prepared. A structural characterization of all the samples was conducted by the x-ray diffraction technique. A grain size of around 12 nm was observed for Li0.5Fe2.5O4 obtained through the sol-gel method. Magnetic properties of lithium ferrite nanoparticles with grain size ranging from 12 to 32 nm were studied. Magnetization measurements showed that Li0.5Fe2.5O4 fine particles exhibit a deviation from the predicted magnetic behaviour. The as-prepared sample of lithium ferrite showed a maximum saturation magnetization of 75 emu g−1. Variation of coercivity is attributed to the transition from multi-domain to single domain nature. Dielectric permittivity and ac conductivity of all the samples were evaluated as a function of frequency, temperature and grain size. Variation of permittivity and ac conductivity with frequency reveals that the dispersion is due to the Maxwell–Wagner type interfacial polarization

New studies on the versatile roles of Polyaniline and its composites in polymer based optoelectronic and energy storage devices

From the early stages of the twentieth century, polyaniline (PANI), a well-known and extensively studied conducting polymer has captured the attention of scientific community owing to its interesting electrical and optical properties. Starting from its structural properties, to the currently pursued optical, electrical and electrochemical properties, extensive investigations on pure PANI and its composites are still much relevant to explore its potentialities to the maximum extent. The synthesis of highly crystalline PANI films with ordered structure and high electrical conductivity has not been pursued in depth yet. Recently, nanostructured PANI and the nanocomposites of PANI have attracted a great deal of research attention owing to the possibilities of applications in optical switching devices, optoelectronics and energy storage devices. The work presented in the thesis is centered around the realization of highly conducting and structurally ordered PANI and its composites for applications mainly in the areas of nonlinear optics and electrochemical energy storage. Out of the vast variety of application fields of PANI, these two areas are specifically selected for the present studies, because of the following observations. The non-linear optical properties and the energy storing properties of PANI depend quite sensitively on the extent of conjugation of the polymer structure, the type and concentration of the dopants added and the type and size of the nano particles selected for making the nanocomposites. The first phase of the work is devoted to the synthesis of highly ordered and conducting films of PANI doped with various dopants and the structural, morphological and electrical characterization followed by the synthesis of metal nanoparticles incorporated PANI samples and the detailed optical characterization in the linear and nonlinear regimes. The second phase of the work comprises the investigations on the prospects of PANI in realizing polymer based rechargeable lithium ion cells with the inherent structural flexibility of polymer systems and environmental safety and stability. Secondary battery systems have become an inevitable part of daily life. They can be found in most of the portable electronic gadgets and recently they have started powering automobiles, although the power generated is low. The efficient storage of electrical energy generated from solar cells is achieved by using suitable secondary battery systems. The development of rechargeable battery systems having excellent charge storage capacity, cyclability, environmental friendliness and flexibility has yet to be realized in practice. Rechargeable Li-ion cells employing cathode active materials like LiCoO2, LiMn2O4, LiFePO4 have got remarkable charge storage capacity with least charge leakage when not in use. However, material toxicity, chance of cell explosion and lack of effective cell recycling mechanism pose significant risk factors which are to be addressed seriously. These cells also lack flexibility in their design due to the structural characteristics of the electrode materials. Global research is directed towards identifying new class of electrode materials with less risk factors and better structural stability and flexibility. Polymer based electrode materials with inherent flexibility, stability and eco-friendliness can be a suitable choice. One of the prime drawbacks of polymer based cathode materials is the low electronic conductivity. Hence the real task with this class of materials is to get better electronic conductivity with good electrical storage capability. Electronic conductivity can be enhanced by using proper dopants. In the designing of rechargeable Li-ion cells with polymer based cathode active materials, the key issue is to identify the optimum lithiation of the polymer cathode which can ensure the highest electronic conductivity and specific charge capacity possible The development of conducting polymer based rechargeable Li-ion cells with high specific capacity and excellent cycling characteristics is a highly competitive area among research and development groups, worldwide. Polymer based rechargeable batteries are specifically attractive due to the environmentally benign nature and the possible constructional flexibility they offer. Among polymers having electrical transport properties suitable for rechargeable battery applications, polyaniline is the most favoured one due to its tunable electrical conducting properties and the availability of cost effective precursor materials for its synthesis. The performance of a battery depends significantly on the characteristics of its integral parts, the cathode, anode and the electrolyte, which in turn depend on the materials used. Many research groups are involved in developing new electrode and electrolyte materials to enhance the overall performance efficiency of the battery. Currently explored electrolytes for Li ion battery applications are in liquid or gel form, which makes well-defined sealing essential. The use of solid electrolytes eliminates the need for containment of liquid electrolytes, which will certainly simplify the cell design and improve the safety and durability. The other advantages of polymer electrolytes include dimensional stability, safety and the ability to prevent lithium dendrite formation. One of the ultimate aims of the present work is to realize all solid state, flexible and environment friendly Li-ion cells with high specific capacity and excellent cycling stability. Part of the present work is hence focused on identifying good polymer based solid electrolytes essential for realizing all solid state polymer based Li ion cells.The present work is an attempt to study the versatile roles of polyaniline in two different fields of technological applications like nonlinear optics and energy storage. Conducting form of doped PANI films with good extent of crystallinity have been realized using a level surface assisted casting method in addition to the generally employed technique of spin coating. Metal nanoparticles embedded PANI offers a rich source for nonlinear optical studies and hence gold and silver nanoparticles have been used for making the nanocomposites in bulk and thin film forms. These PANI nanocomposites are found to exhibit quite dominant third order optical non-linearity. The highlight of these studies is the observation of the interesting phenomenon of the switching between saturable absorption (SA) and reverse saturable absorption (RSA) in the films of Ag/PANI and Au/PANI nanocomposites, which offers prospects of applications in optical switching. The investigations on the energy storage prospects of PANI were carried out on Li enriched PANI which was used as the cathode active material for assembling rechargeable Li-ion cells. For Li enrichment or Li doping of PANI, n-Butyllithium (n-BuLi) in hexanes was used. The Li doping as well as the Li-ion cell assembling were carried out in an argon filled glove box. Coin cells were assembled with Li doped PANI with different doping concentrations, as the cathode, LiPF6 as the electrolyte and Li metal as the anode. These coin cells are found to show reasonably good specific capacity around 22mAh/g and excellent cycling stability and coulombic efficiency around 99%. To improve the specific capacity, composites of Li doped PANI with inorganic cathode active materials like LiFePO4 and LiMn2O4 were synthesized and coin cells were assembled as mentioned earlier to assess the electrochemical capability. The cells assembled using the composite cathodes are found to show significant enhancement in specific capacity to around 40mAh/g. One of the other interesting observations is the complete blocking of the adverse effects of Jahn-Teller distortion, when the composite cathode, PANI-LiMn2O4 is used for assembling the Li-ion cells. This distortion is generally observed, near room temperature, when LiMn2O4 is used as the cathode, which significantly reduces the cycling stability of the cells.

Two-photon ionization of atomic inner-shells

Die Summation ueber des vollstaendige Spektrum des Atoms, die in der Stoehrungstheorie zweiter Ordnung vorkommt, wurde mit Hilfe der Greenschen Funktion Methode berechnet. Die Methode der Greenschen Funktion verlangt die Berechnung der unterschiedlichen Greenschen Funktionen: eine Coulomb-Greensche-Funktion im Fall von wasserstoffaehnlichen Ionen und eine Zentral-feld-Greensche-Funktion im Fall des Vielelektronen-Atoms. Die entwickelte Greensche Funktion erlaubte uns die folgenden atomaren Systeme in die Zweiphotonenionisierung der folgenden atomaren Systeme zu untersuchen: - wasserstoffaehnliche Ionen, um relativistische und Multipol-Effekte aufzudecken, - die aeussere Schale des Lithium; Helium und Helium-aehnliches Neon im Grundzustand, um taugliche Modelle des atomaren Feldes zu erhalten, - K- und L-Schalen des Argon, um die Vielelektronen-Effekte abzuschaetzen. Zusammenfassend, die relativistische Effekte ergeben sich in einer allgemeinen Reduzierung der Zweiphotonen Wirkungsquerschnitte. Zum Beispiel, betraegt das Verhaeltnis zwischen den nichtrelativistischen und relativistischen Wirkungsquerschnitten einen Faktor zwei fuer wasserstoffaehnliches Uran. Ausser dieser relativistischen Kontraktion, ist auch die relativistische Aufspaltung der Zwischenzustaende fuer mittelschwere Ionen sichtbar. Im Gegensatz zu den relativistischen Effekten, beeinflussen die Multipol-Effekte die totalen Wirkungsquerschnitte sehr wenig, so dass die Langwellennaeherung mit der exakten Naeherung fuer schwere Ionen sogar innerhalb von 5 Prozent uebereinstimmt. Die winkelaufgeloesten Wirkungsquerschnitte werden durch die relativistischen Effekte auf eine beeindruckende Weise beeinflusst: die Form der differentiellen Wirkungsquerschnitte aendert sich (qualitativ) abhaengig von der Photonenenergie. Ausserdem kann die Beruecksichtigung der hoeheren Multipole die elektronische Ausbeute um einen Faktor drei aendern. Die Vielelektronen-Effekte in der Zweiphotonenionisierung wurden am Beispiel der K- und L-Schalen des Argon analysiert. Hiermit wurden die totalen Wirkungsquerschnitte in einer Ein-aktives-Elektron-Naeherung (single-active-electron approximation) berechnet. Es hat sich herausgestellt, dass die Elektron--Elektron-Wechselwirkung sehr wichtig fuer die L-Schale und vernachlaessigbar fuer die K-Schale ist. Das bedeutet, dass man die totalen Wirkungsquerschnitte mit wasserstoffaehnlichen Modellen im Fall der K-Schale beschreiben kann, aber fuer die L-Schale fortgeschrittene Modelle erforderlich sind. Die Ergebnisse fuer Vielelektronen-Atome wurden mittels einer Dirac-Zentral-feld-Greenschen Funktion erlangt. Ein numerischer Algorithmus wurde urspruenglich von McGuire (1981) fuer der Schroedinger-Zentral-feld-Greensche Funktion eingefuehrt. Der Algorithmus wurde in dieser Arbeit zum ersten Mal fuer die Dirac-Gleichung angewandt. Unser Algorithmus benutzt die Kummer- und Tricomi-Funktionen, die mit Hilfe eines zuverlaessigen, aber noch immer langsamen Programmes berechnet wurden. Die Langsamkeit des Programms begrenzt den Bereich der Aufgaben, die effizient geloest werden koennen. Die Zentral-feld-Greensche Funktion konnte bei den folgenden Problemen benutzt werden: - Berechnung der Zweiphotonen-Zerfallsraten, - Berechnung der Zweiphotonenanregung und -ionisierungs-Wirkungsquerschnitte, - Berechnung die Multiphotonenanregung und -ionisierungs-Wirkungsquerschnitte, - Berechnung einer atomaren Vielelektronen-Green-Funktion. Von diesen Aufgaben koennen nur die ersten beiden in angemessener Zeit geloest werden. Fuer die letzten beiden Aufgaben ist unsere Implementierung zu langsam und muss weiter verbessert werden.

Transitions between quintet states of doubly excited four-electron ions

Following an earlier observation in F VI we identified the line pair 1s2s2p^2 {^5P}-1s2s2p3d {^5P^0} , {^5D^0} for the elements N, O, Mg, and tentatively for A1 and Si in beam-foil spectra. Assignment was established by comparison with Multi-Configuration Dirac-Fock calculations along the isoelectronic sequence. Using this method we also identified some quartet lines of lithium-like ions with Z > 10.

Dye-sensitized solar cells based on perylene derivatives

The oil price rises more and more, and the world energy consumption is projected to expand by 50 percent from 2005 to 2030. Nowadays intensive research is focused on the development of alternative energies. Among them, there are dye-sensitized nanocrystalline solar cells (DSSCs) “the third generation solar cells”. The latter have gained attention during the last decade and are currently subject of intense research in the framework of renewable energies as a low-cost photovoltaic. At present DSSCs with ruthenium based dyes exhibit highest efficiencies (ca 11%). The objective of the present work is to fabricate, characterize and improve the performance of DSSCs based on metal free dyes as sensitizers, especially on perylene derivatives. The work begins by a general introduction to the photovoltaics and dye-sensitized solar cells, such as the operating principles and the characteristics of the DSSCs. Chapter 2 and 3 discuss the state of the art of sensitizers used in DSSCs, present the compounds used as sensitizer in the present work and illustrate practical issues of experimental techniques and device preparation. A comparative study of electrolyte-DSSCs based on P1, P4, P7, P8, P9, and P10 are presented in chapter 4. Experimental results show that the dye structure plays a crucial role in the performance of the devices. The dye based on the spiro-concept (bipolar spiro compound) exhibited a higher efficiency than the non-spiro compounds. The presence of tert-butylpyridine as additive in the electrolyte was found to increase the open circuit voltage and simultaneously decrease the efficiency. The presence of lithium ions in the electrolyte increases both output current and the efficiency. The sensitivity of the dye to cations contained in the electrolyte was investigated in the chapter 5. FT-IR and UV-Vis were used to investigate the in-situ coordination of the cation to the adsorbed dye in the working devices. The open-circuit voltage was found to depend on the number of coordination sites in the dye. P1 with most coordination sites has shown the lowest potential drop, opposite to P7, which is less sensitive to cations in the working cells. A strategy to improve the dye adsorption onto the TiO2 surface, and thus the light harvesting efficiency of the photoanode by UV treatment, is presented in chapter 6. The treatment of the TiO2 film with UV light generates hydroxyl groups and renders the TiO2 surface more and more hydrophilic. The treated TiO2 surface reacts readily with the acid anhydride group of the dye that acts as an anchoring group and improves the dye adsorption. The short-circuit current density and the efficiency of the electrolyte-based dye cells was considerably improved by the UV treatment of the TiO2 film. Solid-state dye-sensitized solar cells (SSDs) based on spiro-MeOTAD (used as hole transport material) are studied in chapter 7. The efficiency of SSDs was globally found to be lower than that of electrolyte-based solar cells. That was due to poor pore filling of the dye-loaded TiO2 film by the spin-coated spiro-MeOTAD and to the significantly slower charge transport in the spiro-MeOTAD compared to the electrolyte redox mediator. However, the presence of the donor moieties in P1 that are structurally similar to spiro-MeOTAD was found to improve the wettability of the P1-loaded TiO2 film. As a consequence the performance of the P1-based solid-state cells is better compared to the cells based on non-spiro compounds.

Efectividad de la ketamina en depresión bipolar: revisión sistemática de la literatura

Introducción: Aunque el hallazgo clínico más distintivo del Trastorno Afectivo Bipolar es el ánimo patológicamente elevado, este no suele ser el estado de ánimo prevalente de la enfermedad. La fase depresiva del trastorno o depresión bipolar es más crónica, conlleva a un mayor deterioro de la funcionalidad y representa un reto terapéutico habitual. En la actualidad, el manejo farmacológico de la depresión bipolar suele consistir en combinaciones de al menos dos medicamentos distintos, incluyendo estabilizadores del afecto (litio y anticonvulsivantes), antipsicóticos atípicos y antidepresivos. El objetivo central de este trabajo es evaluar la efectividad de la Ketamina en la depresión bipolar. Métodos: Revisión sistemática de la literatura de artículos que proporcionen información sobre la eficacia de la Ketamina en la fase depresiva del Trastorno Bipolar. Resultados: De los 147 artículos arrojados por la búsqueda, dos cumplieron los criterios de selección (n=33). En comparación con placebo, ketamina tiene un efecto antidepresivo rápido y duradero, incluso en pacientes que han recibido más de 3 medicamentos previamente. No se reportaron efectos adversos severos durante los estudios. Discusión. La evidencia actual apunta a que la ketamina es útil para el manejo de la depresión bipolar, incluso cuando es resistente al tratamiento, es segura y puede tener cierto efecto antisuicida. Es necesario ampliar la evidencia existente.

Aproximacions sintètiques per a la preparació estereoselectiva de noves quinolil i pirazolilglicines i per a la preparació en fase sòlida de llibreries de benzotiazoles, 1,2,4-triazines i benzimidazoles

El treball experimental que ha permès redactar la present Tesi Doctoral ha estat dividit en dues parts. A la primera part es presenten els resultats referents a la síntesi estereocontrolada de noves heteroarilglicines (quinolil i pirazolilglicines) a partir de cetones acetilèniques, substrats quirals que permeten accedir a l'esquelet de diferents heterocicles (quinolines i pirazoles), la posterior obtenció dels corresponents quinolil i pirazolil--aminoalcohols i les diferents metodologies d'oxidació per tal d'accedir a les corresponents quinolil i priazolilglicines objectiu. A la segona part d'aquesta memòria s'ha estudiat, en dissolució, l'habilitat del grup alquilsulfona com a grup sortint eficaç en reaccions d'ipso-substitució nucleofilica. El desenvolupament d'aquesta reacció ha servit de punt de partida per a la creació de llibreries d'heterocicles amb alta diversitat molecular i potencial interès biològic sobre fase sòlida.

Geochemical precursors to volcanic activity at Mount St. Helens, USA

The importance of the interplay between degassing and crystallization before and after the eruption of Mount St. Helens (Washington, USA) in 1980 is well established. Here, we show that degassing occurred over a period of decades to days before eruptions and that the manner of degassing, as deduced from geochemicai signatures within the magma, was characteristic of the eruptive style. Trace element (lithium) and short-lived radioactive isotope (lead-210 and radium-226) data show that ascending magma stalled within the conduit, leading to the accumulation of volatiles and the formation of lead-210 excesses, which signals the presence of degassing magma at depth.

Regulation of glycogen synthase kinase 3 in human platelets: a possible role in platelet function?

In this study we show that both glycogen synthase kinase 3 (GSK3) isoforms, GSK3alpha and GSK3beta, are present in human platelets and are phosphorylated on Ser(21) and Ser(9), respectively, in platelets stimulated with collagen, convulxin and thrombin. Phosphorylation of GSK3alpha/beta was dependent on phosphoinositide 3-kinase (PI3K) activity and independent of platelet aggregation, and correlated with a decrease in GSK3 activity that was preserved by pre-incubating platelets with PI3K inhibitor LY294002. Three structurally distinct GSK3 inhibitors, lithium, SB415286 and TDZD-8, were found to inhibit platelet aggregation. This implicates GSK3 as a potential regulator of platelet function. (C) 2003 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Ring-chain interconversion in high-performance polymer systems. 3. Cyclodepolymerization of poly(m-phenylene isophthalamide) (Nomex) and entropically driven ring-opening polymerization of the macrocyclic oligomers so produced

A homologous series of macrocyclic oligoamides has been prepared in high yield by reaction of isophthaloyl chloride with m-phenylenediamine under pseudo-high-dilution conditions. The products were characterized by infrared and H-1 NMR spectroscopies, matrix assisted laser desorption-ionization time-of-flight mass spectrometry, and gel permeation chromatography (GPC). A series of linear oligomers was prepared for comparison. The macrocycles ranged in size from the cyclic trimer up to at least the cyclic nonamer (90 ring atoms). The same homologous series of macrocyclic oligomers was prepared in high yield by the cyclodepolymerization of poly(m-phenylene isophthalamide) (Nomex). Cyclodepolymerization was best achieved by treating a 1% w/v solution of the polymer in dimethyl sulfoxide containing calcium chloride or lithium chloride with 3-4 mol % of sodium hydride or the sodium salt of benzanilide at 150 degreesC for 70 h. Treatment of a concentrated solution of the macrocyclic oligomers (25% w/v) with 4 mol % of sodium hydride or the sodium salt of benzanilide in a solution of lithium chloride in dimethyl sulfoxide at 170 degreesC for 6 h resulted in efficient entropically driven ring-opening polymerizations to give poly(m-phenylene isophthalamide), characterized by infrared and H-1 NMR spectroscopies and by GPC. The molecular weights obtained were comparable with those of the commercial polymer.

Asymmetric synthesis of (1R,2S,3R)-3-methylcispentacin and (1S,2S,3R)-3-methyltranspentacin by kinetic resolution of tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate

Conjugate addition of lithium dibenzylamide to tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate occurs with high levels of stereocontrol, with preferential addition of lithium dibenzylamide to the face of the cyclic alpha,beta-unsaturated acceptor anti- to the 3-methyl substituent. High levels of enantiorecognition are observed between tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate and an excess of lithium (+/-)-N-benzyl-N-alpha-methylbenzylamide (10 eq.) (E > 140) in their mutual kinetic resolution, while the kinetic resolution of tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate with lithium (S)-N-benzyl-N-alpha-methylbenzylamide proceeds to give, at 51% conversion, tert-butyl (1R, 2S, 3R,alphaS)-3-methyl-2-N-benzyl-N-alpha-methylbenzylaminocyclopentane-1-c arboxylate consistent with E > 130, and in 39% yield and 99 +/- 0.5% de after purification. Subsequent deprotection by hydrogenolysis and ester hydrolysis gives (1R, 2S, 3R)-3-methylcispentacin in > 98% de and 98 +/- 1% ee. Selective epimerisation of tert-butyl (1R, 2S, 3R, alphaS)-3-methyl-2-N- benzyl-N-alpha-methylbenzylaminocyclopentane-1-carboxylate by treatment with (KOBu)-Bu-t in (BuOH)-Bu-t gives tert-butyl (1S, 2S, 3R, alphaS)-3-methyl-2-N-benzyl-N-alpha-methylbenzylaminocyclopentane-1-carb oxylate in quantitative yield and in > 98% de, with subsequent deprotection by hydrogenolysis and ester hydrolysis giving (1S, 2S, 3R)-3-methyltranspentacin hydrochloride in > 98% de and 97 +/- 1% ee.

Templated synthesis of the novel layered silver-antimony Sulfides [H3NCH2CH2NH2][Ag2SbS3] and [H3NCH2CH2NH2](2)[Ag5Sb3S8]

Two new silver-antimony sulfides, [C2H9N2][Ag2SbS3] (1) and [C2H9N2](2)[Ag5Sb3S8] (2), have been prepared solvothermally in the presence of ethylenediamine and characterized by single-crystal X-ray diffraction, thermogravimetry, and elemental analysis. Compound 1 crystallizes in the space group Pn (a = 6.1781(1) Angstrom, b =11.9491(3) Angstrom, c = 6.9239(2) Angstrom, =111.164(1)degrees) and 2 in the space group Pm (a = 6.2215(2) Angstrom, b = 15.7707(7) Angstrom, c = 11.6478(5) Angstrom, beta = 92.645(2)degrees). The structure of 1 consists of chains of fused five-membered Ag2SbS2 rings linked to form layers, between which the template molecules reside. Compound 2 contains honeycomb-like sheets of fused silver-antimony-sulfide six-membered rings linked to form double layers. The idealized structure can be considered to be an ordered defect derivative of that of lithium bismuthide, Li3Bi, and represents a new solid-state structure type.

Heteroaryl substituted titanocenes as potential anti-cancer drugs

From the reaction of Super Hydride (LiBEt3H) with 6-(furyl)fulvene (1a), 6-(thiophenyl)fulvene (1b) or 6-(N-methyl-pyrrole)fulvene (1c) the corresponding lithium cyclopentadienide intermediates (2a-c) were obtained. These intermediates were reacted with titanium tetrachloride and bis-[(furyl-2-cyclopentadienylmethane)] titanium(IV) dichloride (3a) and bis-[(thiophenyl-2-cyclopentadienylmethane)] titanium(IV) dichloride (3b) and bis-[(N-methylpyrrole-2-cyclopentadienylmethane)] titanium(IV) dichloride (3c) were obtained and subsequently characterised by X-ray crystallography. When titanocenes 3a-c were tested against pig kidney (LLC-PK) cells inhibitory concentrations (IC50) of 1.6 x 10(-4) M, 1.5 x 10(-4) M and 9.1 x 10(-5) M, respectively, were observed. These values represent improved cytotoxicity against LLC-PK, when compared to their corresponding ansa substituted analogues and also in comparison to unsubstituted titanocene dichloride. (c) 2006 Elsevier Inc. All rights reserved.

Crystal structures of [PhLi center dot(-)-sparteine](2), [PhOLi center dot(-)-sparteine](2), and the mixed aggregate [PhLi center dot PhOLi center dot 2(-)-sparteine]

Crystal structure determination of adducts of sparteine and PhLi, (-)-sparteine and PhOLi and of sparteine and PhLi/PhOLi reveal a four-membered ring with two lithium centers, each capped by a (-)-sparteine ligand, as central motif of all structure. Quantum-chemical calculations show that the mixed aggregate [PhLi center dot PhOLi center dot 2(-)-sparteine] is energetically more favorable than the model system {1/2[PhLi center dot(-)-sparteine](2) + 1/2[PhOLi center dot(-)-sparteine](2)}.