Reductive dimerization of benzothiazolium salts

Three different types of reaction products were obtained from the reduction of 2-substituted 3-methylbenzothiazolium salts using Na : Hg (1 wt%). Depending on the 2-substituents, two types of dimeric compounds were obtained: the 2-cyclohexyl-, 2-phenyl-, and 2-(p-tolyl)-substituted species are reduced to the corresponding 2,2'-bibenzo[d]thiazoles, while their 2-((p-OMe)C6H4)- and 2-((p-NMe2)C6H4)-substituted derivatives afford cis-[1,4]benzothiazino[3,2-b][1,4]benzothiazines. Furthermore, in the presence of molecular O2, new disulfide derivatives were obtained from the bibenzo[d]thiazoles. The products were obtained in a moderate to good yield, and the structures were confirmed using single-crystal X-ray diffraction. The electrochemistry and further reactivity towards different oxidants of the dimeric compounds were studied; the 2,2'-bibenzo[d]thiazoles show oxidation potentials similar to that of ferrocene and are converted back to the corresponding benzothiazolium cations by mild oxidants such as TCNQ. In contrast, the benzothiazino-benzothiazines show no oxidations in the solvent window of THF.

Benzoimidazolium-derived dimeric and hydride n-dopants for organic electron-transport materials: impact of substitution on structures, electrochemistry, and reactivity

1,3-Dimethyl-2,3-dihydrobenzo[d]imidazoles, 1H, and 1,1',3,3'-tetramethyl-2,2',3,3'-tetrahydro-2,2'-bibenzo[d]imidazoles, 12, are of interest as n-dopants for organic electron-transport materials. Salts of 2-(4-(dimethylamino)phenyl)-4,7-dimethoxy-, 2-cyclohexyl-4,7-dimethoxy-, and 2-(5-(dimethylamino)thiophen-2-yl)benzo[d]imidazolium (1g-i+, respectively) have been synthesized and reduced with NaBH4 to 1gH, 1hH, and 1iH, and with Na:Hg to 1g2 and 1h2. Their electrochemistry and reactivity were compared to those derived from 2-(4-(dimethylamino)phenyl)- (1b+) and 2-cyclohexylbenzo[d]imidazolium (1e+) salts. E(1+/1•) values for 2-aryl species are less reducing than for 2-alkyl analogues, i.e., the radicals are stabilized more by aryl groups than the cations, while 4,7-dimethoxy substitution leads to more reducing E(1+/1•) values, as well as cathodic shifts in E(12•+/12) and E(1H•+/1H) values. Both the use of 3,4-dimethoxy and 2-aryl substituents accelerates the reaction of the 1H species with PC61BM. Because 2-aryl groups stabilize radicals, 1b2 and 1g2 exhibit weaker bonds than 1e2 and 1h2 and thus react with 6,13-bis(triisopropylsilylethynyl)pentacene (VII) via a "cleavage-first" pathway, while 1e2 and 1h2 react only via "electron-transfer-first". 1h2 exhibits the most cathodic E(12•+/12) value of the dimers considered here and, therefore, reacts more rapidly than any of the other dimers with VII via "electron-transfer-first". Crystal structures show rather long central C-C bonds for 1b2 (1.5899(11) and 1.6194(8) Å) and 1h2 (1.6299(13) Å).

Organometallic and Organic Dimers: Moderately Air-Stable, Yet Highly Reducing, n-Dopants

ConspectusElectrical doping using redox-active molecules can increase the conductivity of organic semiconductors and lower charge-carrier injection and extraction barriers; it has application in devices such as organic and perovskite light-emitting diodes, organic and perovskite photovoltaic cells, field-effect transistors, and thermoelectric devices. Simple one-electron reductants that can act as n-dopants for a wide range of useful semiconductors must necessarily have low ionization energies and are, thus, highly sensitive toward ambient conditions, leading to challenges in their storage and handling. A number of approaches to this challenge have been developed, in which the highly reducing species is generated from a precursor or in which electron transfer is coupled in some way to a chemical reaction. Many of these approaches are relatively limited in applicability because of processing constraints, limited dopant strength, or the formation of side products.This Account discusses our work to develop relatively stable, yet highly reducing, n-dopants based on the dimers formed by some 19-electron organometallic complexes and by some organic radicals. These dimers are sufficiently inert that they can be briefly handled as solids in air but react with acceptors to release two electrons and to form two equivalents of stable monomeric cations, without formation of unwanted side products. We first discuss syntheses of such dimers, both previously reported and our own. We next turn to discuss their thermodynamic redox potentials, which depend on both the oxidation potential of the highly reducing odd-electron monomers and on the free energies of dissociation of the dimers; because trends in both these quantities depend on the monomer stability, they often more-or-less cancel, resulting in effective redox potentials for a number of the organometallic dimers that are approximately -2.0 V vs ferrocenium/ferrocene. However, variations in the dimer oxidation potential and the dissociation energies determine the mechanism through which a dimer reacts with a given acceptor in solution: in all cases dimer-to-acceptor electron transfer is followed by dimer cation cleavage and a subsequent second electron transfer from the neutral monomer to the acceptor, but examples with weak central bonds can also react through endergonic cleavage of the neutral dimer, followed by electron-transfer reactions between the resulting monomers and the acceptor. We, then, discuss the use of these dimers to dope a wide range of semiconductors through both vacuum and solution processing. In particular, we highlight the role of photoactivation in extending the reach of one of these dopants, enabling successful doping of a low-electron-affinity electron-transport material in an organic light-emitting diode. Finally, we suggest future directions for research using dimeric dopants.

Powerful Organic Molecular Oxidants and Reductants Enable Ambipolar Injection in a Large-Gap Organic Homojunction Diode

Doping has proven to be a critical tool for enhancing the performance of organic semiconductors in devices like organic light-emitting diodes. However, the challenge in working with high-ionization-energy (IE) organic semiconductors is to find p-dopants with correspondingly high electron affinity (EA) that will improve the conductivity and charge carrier transport in a film. Here, we use an oxidant that has been recently recognized to be a very strong p-type dopant, hexacyano-1,2,3-trimethylene-cyclopropane (CN6-CP). The EA of CN6-CP has been previously estimated via cyclic voltammetry to be 5.87 eV, almost 300 meV higher than other known high-EA organic molecular oxidants. We measure the frontier orbitals of CN6-CP using ultraviolet and inverse photoemission spectroscopy techniques and confirm a high EA value of 5.88 eV in the condensed phase. The introduction of CN6-CP in a film of large-band-gap, large-IE phenyldi(pyren-1-yl)phosphine oxide (POPy₂) leads to a significant shift of the Fermi level toward the highest occupied molecular orbital and a 2 orders of magnitude increase in conductivity. Using CN6-CP and n-dopant (pentamethylcyclopentadienyl)(1,3,5-trimethylbenzene)ruthenium (RuCp*Mes)₂, we fabricate a POPy₂-based rectifying p-i-n homojunction diode with a 2.9 V built-in potential. Blue light emission is achieved under forward bias. This effect demonstrates the dopant-enabled hole injection from the CN6-CP-doped layer and electron injection from the (RuCp*Mes)₂-doped layer in the diode.

Potential Risk by Disposal of Bottom Ash from Thermal Power Plants and Minimization by Addition of NaHCO3

In the present study, the leachability of traced elements from the bottom ash of three different Indian power plants was investigated. Environmental impact of bottom ash was studied by varying the liquid-to-solid (L/S) ratio from 20:1 to 60:1. Leaching results show the presence of a major proportion of elements Mn, Mg, Cr, Zn and Cu and a minor proportion of Pb, Fe, Co, and Mo. The effect of the addition of sodium bicarbonate (NaHCO₃) on leaching characteristics of bottom ash was also studied. Leaching concentration of bottom ash samples reduces with addition of additive from 0.2% to 0.6% and found to be optimum with 0.4% the addition of additive. This aspect of the investigation helps to design the ash disposal system for higher solid concentrations to minimize the environmental pollution.

Role of particle size in assessment of physico-chemical properties and trace elements of Indian fly ash

In this paper, the effect of particle size on the physico-chemical, mineralogical, and leaching behavior of Indian fly ash was studied. Experiments were carried out to study the leaching of different elements such as Mg, Cr, Zn, Pb, Mn, Fe, Cu, Co, Mo, and Ni from Indian fly ash. During the experiments, the liquid-to-solid (L/S) ratio of the fly ash was taken as 9/1, 8/2, 7/3, 3/2, 1/1, and 2/3. The effect of four different particle size ranges (below 53, 53-75, 75-106, and 106-150 μm) of fly ash was analyzed. The ASTMD-3987 method was used to analyze the presence of trace elements from fly ash. In the ASTM D-3987 method, distilled water was used for extraction of leachate. Fly ash slurry samples were agitated in a lubricating type temperature-controlled Remi orbital shaker for a time duration of 18 hours with speed of 100 revolutions per minute (rpm) at a temperature of 25ºC. Distilled water does not save cost as well as being easily available. The leaching test of trace elements from fly ash was investigated at different pH conditions in order to predict the environmental effect from the ash disposal on the groundwater quality. Results revealed that pH of slurry suspension increases with increase in particle size. The pH value of fly ash slurries was negligibly affected by the decrease in L/S ratio for all particle sizes. Fine particles of fly ash produce a more harmful effect as compared to the coarser range of fly ash particles.

Performance and exhaust emission characteristics of variable compression ratio diesel engine fuelled with esters of crude rice bran oil

As a substitute to petroleum-derived diesel, biodiesel has high potential as a renewable and environment friendly energy source. For petroleum importing countries the choice of feedstock for biodiesel production within the geographical region is a major influential factor. Crude rice bran oil is found to be good and viable feedstock for biodiesel production. A two step esterification is carried out for higher free fatty acid crude rice bran oil. Blends of 10, 20 and 40 % by vol. crude rice bran biodiesel are tested in a variable compression ratio diesel engine at compression ratio 15, 16, 17 and 18. Engine performance and exhaust emission parameters are examined. Cylinder pressure-crank angle variation is also plotted. The increase in compression ratio from 15 to 18 resulted in 18.6 % decrease in brake specific fuel consumption and 14.66 % increase in brake thermal efficiency on an average. Cylinder pressure increases by 15 % when compression ratio is increased. Carbon monoxide emission decreased by 22.27 %, hydrocarbon decreased by 38.4 %, carbon dioxide increased by 17.43 % and oxides of nitrogen as NO_x emission increased by 22.76 % on an average when compression ratio is increased from 15 to 18. The blends of crude rice bran biodiesel show better results than diesel with increase in compression ratio.

Comparative Studies on Performance Characteristics of CI Engine Fuelled with Neem Methyl Ester and Mahua Methyl Ester and Its Respective Blends with Diesel Fuel

In the present investigation, neem and mahua methyl ester were prepared by transesterification using potassium hydroxide as a catalyst and tested in 4-stroke single cylinder water cooled diesel engine. Tests were carried out at constant speed of 1500 rev/min at different brake mean effective pressures. A series of tests were conducted which worked at different brake mean effective pressures, OkPa, 1kPa, 2kPa, 3kPa, 4kPa, 5kPa, 6kPa and 6.5kPa. The performance and exhaust emission characteristics of the diesel engine were analyzed and compared with diesel fuel. Results showed that BTE of NME was comparable with diesel and it was noted that the BTE of N0100 is 63.11% higher than that of diesel at part load whereas it reduces 11.2% with diesel fuel at full load. In case of full load, NME showed decreasing trend with diesel fuel. BTE of diesel was 15.37% and 36.89% at part load and full load respectively. The observation indicated that BTE for MME 100 was slightly higher than diesel at part loads. The specific fuel consumption (SFC) was more for almost all blends at all loads, compared to diesel. At part load, the EGT of MME and its blends were showing similar trend to diesel fuel and at full load, the exhaust gas temperature of MME and blends were higher than diesel. Based on this study, NME could be a substitute for diesel fuel in diesel engine.

Ultralow doping in organic semiconductors: evidence of trap filling

Tail states in organic semiconductors have a significant influence on device performances by acting as traps in charge transport. We present a study of the controlled passivation of acceptor tail states in fullerene C(60) by the addition of electrons introduced by molecular n doping. Using ultralow doping, we are able to successively fill the traps with charges and examine the changes in conductivity, activation energy, mobility, and Fermi-level position. Passivation of the traps leads to an increase of the electron mobility in C(60) by more than 3 orders of magnitude, to reach 0.21 cm(2)/(V s).

n-Doping of organic electronic materials using air-stable organometallics

Air-stable dimers of sandwich compounds including rhodocene and (pentamethylcyclopentadienyl)(arene)ruthenium and iron derivatives can be used for n-doping electron-transport materials with electron affinities as small as 2.8 eV. A p-i-n homojunction diode based on copper phthalocyanine and using rhodocene dimer as n-dopant shows a rectification ratio of greater than 10(6) at 4 V.

Selective lithiation and phosphane-functionalization of [(eta(7)-C7H7)Ti(eta(5)-C5H5)] (troticene) and its use for the preparation of early-late heterobimetallic complexes

The cycloheptatrienyl-cyclopentadienyl sandwich complex [(eta(7)-C(7)H(7))Ti(eta(5)-C(5)H(5))] (troticene) can be dilithiated (once at each ring) or selectively monolithiated, either at the seven- or five-membered ring, depending on the reaction conditions. Treatment of the resulting lithiotroticenes with ClPPh(2) afforded the corresponding troticenyl-phosphanes [(eta(7)-C(7)H(6)PPh(2))Ti(eta(5)-C(5)H(4)PPh(2))] (1), [(eta(7)-C(7)H(6)PPh(2))Ti(eta(5)-C(5)H(5))] (2), or [(eta(7)-C(7)H(7))Ti(eta(5)-C(5)H(4)PPh(2))] (3). The use of nBuLi/N,N',N',N'',N"-pentamethyldiethylenetriamine (pmdta) allowed us to isolate the lithium complexes [(eta(7)-C(7)H(6)Li)Ti(eta(5)-C(5)H(4)Li)] x pmdta (4) and [(eta(7)-C(7)H(7))Ti(eta(5)-C(5)H(4)Li)] x pmdta (5), which were structurally characterized by X-ray diffraction analyses. Reaction of the monophosphane 3 with Mo(CO)(6) and [(tht)AuCl] (tht = tetrahydrothiophene) afforded the heterobimetallic complexes [(3)Mo(CO)(5)] (6) and [(3)AuCl] (7) and also the trimetallic species [(3)(2)AuCl] (8). The reaction of trans-[PtCl(2)(SEt(2))(2)] with the diphosphane 1 led to the formation of cis-[(1)PtCl(2)] (9), whereas the complexes trans-[(2)(2)PtCl(2)] (10) and trans-[(3)(2)PtCl(2)] (11) were isolated by reaction of two equivalents of the monophosphanes 2 and 3 with trans-[PtCl(2)(SEt(2))(2)]. The X-ray crystal structures of 6-11 are also reported.

Primary CNS lymphoma as second malignancy in a case of carcinoma larynx treated with chemoradiation

A 66-year-old male was diagnosed as carcinoma larynx in the year April 2004. He was treated with concurrent chemoradiation and remained disease free for three consecutive years. After 3 years he suddenly complained of giddiness and seizures. Magnetic Resonance Imaging of brain showed features of primary CNS lymphoma (PCNSL) which was confirmed by histopathology test. To the best of our knowledge PCNSL as second malignancy in a case of carcinoma of head and neck has not been reported till date. The PCNSL in this patient may have resulted from depressed immunity due to previous radiotherapy. Whatever may be the predisposing cause, this case is most probably the first reported case of PCNSL in a patient of squamous cell carcinoma of larynx.

Growth of carbon nanotubes on nanoporous titania templates

This work reports the synthesis of multiwalled carbon nanotubes (MWCNTs) on nanoporous titanium dioxide (TiO2) templates. TiO2 nanotubular templates for MWCNTs are produced by anodization of titanium followed by pulsed electrodeposition (PED) of cobalt inside the TiO2 nanotubes. Cobalt acts as a catalyst for the growth of MWCNTs using chemical vapor deposition (CVD) technique. The cobalt catalyst initiates the growth of well graphitized MWCNTs inside the titania pores as well as beyond the titania pores. These materials have been characterized by SEM, EDS, GXRD, XPS, TEM, and ED techniques. The MWCNTs were about 10 mu in length and 80-120 nm in diameter.

Synthesis, characterization and catalytic properties of trivalent iron substituted hexagonal mesoporous aluminophosphates

Trivalent iron substituted hexagonal mesoporous aluminophosphate molecular sieve has been synthesized and characterized for the first time, which showed excellent catalytic activity and reusability for the cyclohexane oxidation reaction under mild conditions.

Artificial neural network and medicine

The introduction of human brain functions such as perception and cognition into the computer has been made possible by the use of Artificial Neural Network (ANN). ANN are computer models inspired by the structure and behavior of neurons. Like the brain, ANN can recognize patterns, manage data and most significantly, learn. This learning ability, not seen in other computer models simulating human intelligence, constantly improves its functional accuracy as it keeps on performing. Experience is as important for an ANN as it is for man. It is being increasingly used to supplement and even (may be) replace experts, in medicine. However, there is still scope for improvement in some areas. Its ability to classify and interpret various forms of medical data comes as a helping hand to clinical decision making in both diagnosis and treatment. Treatment planning in medicine, radiotherapy, rehabilitation, etc. is being done using ANN. Morbidity and mortality prediction by ANN in different medical situations can be very helpful for hospital management. ANN has a promising future in fundamental research, medical education and surgical robotics.

Screening for okadaic acid by immunoassay

Increasing incidences of phytoplankton blooms with the potential danger of toxin release into the food chain have necessitated the search for new diagnostic methods that can detect toxins quickly and reliably. A competitive enzyme-linked immunosorbent assay (ELISA) was developed to quantitate okadaic acid in shellfish and phytoplankton extracts. To determine the specificity of the assay, a number of toxins, such as calyculin A, brevetoxin-1, and dinophysistoxins-1, -2, and -3 were analyzed. Both dinophysistoxins-2 and -1 could be detected by the assay but in concentration ranges 10- and 20-fold higher than that for okadaic acid, respectively. Dinophysistoxin-3, calyculin A, or brevetoxin-1 could not be detected with this assay. To validate the accuracy of the method, 18 mussel and 7 phytoplankton extracts were analyzed in parallel for okadaic acid content by ELISA and liquid chromatography combined with either fluorescence or mass spectrometric detection. Very high correlation between the results was found.

Purification and characterization of lutropin receptor from membranes of pig follicular fluid

Membranes derived from free floating granulosa cells in porcine ovarian follicular fluid were used as a starting material for structural characterization of both LH/hCG and FSH receptors. The receptors were highly hormone-specific and showed single classes of high-affinity binding sites (Kd = 19-74 pM). Their molecular weights as determined by affinity cross-linking with their respective 125I-ligands were similarly 70,000. The membrane-localized receptors could be solubilized with reduced Triton X-100 in the presence of 20% glycerol with good retention of hormone binding activity. The Triton extracts of membranes also showed hormone specificity and equilibrium binding constants similar to the membrane receptors (Kd = 32-48 pM). Affinity chromatography on divinylsulfonyl-Sepharose-oLH columns was utilized to purify the solubilized LH/hCG receptor to a specific activity of 2000 pmol/mg of protein. The purified receptor exhibited a high specificity for hCG and hLH but not for hFSH nor bTSH. The purified receptor was iodinated and visualized to be composed of a major protein of Mr approximately 70,000 and other minor proteins of molecular weights ranging from 14,000 to 40,000. Except for the Mr 14,000 protein, all other protein species bound to the concanavalin A-Sepharose column. The data suggest that the ovarian LH/hCG and FSH receptors are structurally similar and consist of a single polypeptide chain, as recently documented for the LH/hCG receptor (Loosefelt et al., 1989; McFarland et al., 1989).

Distribution of follitropin and deglycosylated follitropin in the rat: a quantitative and radioautographic study

125I-labeled ovine follitropin (125I-oFSH) and deglycosylated follitropin (125I-DG-oFSH) were injected into rats and the tissue uptake was quantified and correlated with radioautographic data. Trichloroacetic acid (TCA)-precipitable radioactivity and gel filtration analysis of blood samples indicated no degradation of follitropin or analogue with time. Clearance of follitropin from the circulation was accelerated after its deglycosylation. Disappearance of both molecules from the blood was associated with uptake and/or loss of radioactivity from liver, kidney, ovary and spleen. The more rapid removal of deglycosylated follitropin from blood was associated with higher renal levels of accumulated radioactivity than native follitropin. This was associated with its localization within the cortex, specifically the proximal convoluted tubules of the nephron. Binding of 125I-labeled follitropin and analogue to granulosa cells was specific and time-dependent. 125-I-DG-oFSH demonstrated greater avidity of binding to rat granulosa cells with time than 125I-oFSH. This was associated with slower dissociation kinetics and/or metabolism for 125I-DG-oFSH. The absence of localization of either 125I-follitropin or analogue in hepatic tissue suggests that hepatic mechanisms may not significantly contribute to the clearance of these molecules. Implications of these findings in regard to the metabolism of oFSH and its antagonist are discussed.

On the identity of bovine seminal plasma inhibin

In light of current discussions on multiple forms of inhibin, it was thought of interest to ascertain the identity of the postulated 'iso-hormones' of bull seminal plasma inhibin (Chari et al., 1978). By subjecting the biologically active fraction, obtained by Sephadex G-100 gel filtration of bull seminal plasma acetone powder, to extensive dialysis in distilled water adjusted to pH 5.8, it was possible to remove the bulk of inert protein as a precipitate. The resulting active preparation could be readily fractionated by preparative iso-electric focusing in the pH range 4.0-6.5 yielding 2 distinct homogeneous peptides, alpha and beta, capable of suppressing hCG-induced uterine weight increase in immature mice, in a 'reversed Steelman-Pohley' assay design. However, of these, alpha alone was able to suppress post-castrational serum gonadotropin rise in appropriate animal models. This peptide is highly acidic in nature (iso-electric point congruent to 2.2) and has a molecular weight (Mr) of 18200 and a Stokes radius of 1.90 nm. On the basis of currently available evidence, it is concluded that the molecule consists of a single peptide chain.

Juvenile T waves (a study of 100 normal subjects)

"Juvenile pattern" of T wave inversion in the precordial leads of electrocardiogram was studied in 100 normal healthy Indians of 0 to 70 years of age in both sexes. Incidence of such pattern was observed in 25 subjects upto 19 years of age. Persons of weight/height ratio less than 30% had higher incidence of juvenile T waves. Maximum incidence (48%) of juvenile T waves was observed in the annual income group of Rs. 15000/-. Exercise ECC showed slight flattening of the inverted T waves in V1 to V3 leads in eight subjects only.

Aquo-pentamine Co(III) complexes as models for carbonic anhydrase

The hydrolysis of 4-nitrophenyl acetate by metal complexes Co(en)2(imH)H2O3+, Co(en)2(bzmH)H2O3+, and Co(en)2(imCH3)H2O3+ (imH = imidazole, bzmH = benzimodazole, imCH3 = methyl imidazole) has been investigated in the pH range 5.4-8.9. The small difference in nucleophilic reactivity in the pH range 5.4-6.7 is assumed to be due to hydrogen bonding abilities of the imidazole and substituted imidazole ligands and small pKa differences (k2(imH) = 2.2 X 10(-2) M-1 sec-1, k2(bzmH) = 5.68 X 10(-2) M-1 sec-1, k2(imCH3) = 1.35 X 10(-2) M-1 sec-1, 40 degrees C, 1 = 0.3 NaClO4, pKa(imH) = 6.2, pKa(imCH3) = 6.2 and pKa(bzmH) = 5.9). In the pH range 7.8-8.9, the differences in nucleophilic reactivity (k3(imH) = 85.5 X 10(-2) M-1 sec-1, k3(bzmH) = 33.4 X 10(-2) M-1 sec-1, 40 degrees C, I = 0.3 NaClO4) are reconciled with a significant steric factor outweighing the acidity of the benzimidazole complex. In the pH region 6.7-7.7, the deviation from linearity is presumably due to both hydroxo and imido ligands functioning as nucleophiles, the latter being about 40 times stronger than the former.