4-Bromo-N,N′-bis­(4-methoxy­phen­yl)benzamidine

The title compound, C21H19BrN2O2, is an amidine containing electron-donating meth­oxy groups and a bulky Br atom on the benzene rings. The solid-state structure reveals a non-centrosymmetric mol­ecule, with an E configuration around the C=N double bond. The C—N bonds show distinct amine [1.3689 (19) Å] and imine [1.285 (2) Å] characteristics. In the crystal, symmetry-related mol­ecules are linked via a very weak N—H⋯N inter­action, and C—H⋯O and C—H⋯π inter­actions

Synthesis and properties of d6 metal complexes of bidentate and tridentate ‘super donor’ ligands

La polyvalence de la réaction de couplage-croisé C-N a été explorée pour la synthèse de deux nouvelles classes de ligands: (i) des ligands bidentates neutres de type N^N et (ii) des ligands tridentates neutres de type N^N^N. Ces classes de ligands contiennent des N-hétérocycles aromatiques saturés qui sont couplés avec hexahydropyrimidopyrimidine (hpp). Les ligands forment de cycles à six chaînons sur la coordination du centre Ru(II). Ce fait est avantageux pour améliorer les propriétés photophysiques des complexes de polypyridyl de Ru(II). Les complexes de Ru(II) avec des ligands bidentés ont des émissions qui dépendent de la basicité relative des N-hétérocycles. Bien que ces complexes sont électrochimiquement et photophysiquement attrayant, le problème de la stereopurité ne peut être évité. Une conception soigneuse du type de ligand nous permet de synthétiser un ligand bis-bidentate qui est utile pour surmonter le problème de stereopurité. En raison de la spécialité du ligand bis-bidentate, son complexe diruthénium(II,II) présente une grande diastéréosélectivité sans séparation chirale. Alors que l'unité de hpp agit comme un nucléophile dans le mécanisme de C-N réaction de couplage croisé, il peut également agir en tant que groupe partant, lorsqu'il est activé avec un complexe de monoruthenium. Les complexes achiraux de Ru(II) avec les ligands tridentés présentent des meilleures propriétés photophysiques en comparason avec les prototypes [Ru(tpy)2]2+ (tpy = 2,2′: 6′, 2′′-terpyridine). L’introduction de deux unités de hpp dans les ligands tridentates rend le complexe de Ru(II) en tant que ‘absorbeur noir’ et comme ‘NIR émetteur’ (NIR = de l’anglais, Near Infra-Red). Cet effet est une conséquence d'une meilleure géométrie de coordination octaédrique autour de l'ion Ru(II) et de la forte donation sigma des unités hpp. Les complexes du Re(I) avec des ligands tridentates présentent un comportement redox intéressant et ils émettent dans le bleu. L'oxydation quasi-réversible du métal est contrôlée par la donation sigma des fragments hpp, tandis que la réduction du ligand est régie par la nature électronique du motif N-hétérocycle central du ligand lui-même. Cette thèse presente également l'auto-assemblage des métal-chromophores comme ‘métallo-ligands’ pour former des espèces supramoléculaires discretes utilisant des complexes neutres. Les synthèses et propriétés des métaux-chromophores précités et les supramolécules sont discutées.The versatility of C-N cross coupling reactions has been explored for the synthesis of two novel classes of ligands : (i) neutral bidentate N^N ligands and (ii) neutral tridentate N^N^N ligands. Both classes of ligands contain saturated aromatic N-heterocycles coupled with the unsaturated hexahydropyrimidopyrimidine (hpp) unit. The ligands form six-membered chelate rings upon coordination to a Ru(II) center. This fact is advantageous to improve the photophysical properties of Ru(II)-polypyridyl complexes. Ru(II) complexes of bidentate ligands can act as red-emitters. The red-emission is dependent on the relative basicity of the N-heterocycles. While these complexes are electrochemically and photophysically appealing, the problem of stereopurity can not be avoided. Careful ligand design affords bis-bidentate ligand that is useful to overcome the problem of stereopurity. Due to the speciality of this bis-bidentate ligand, its diruthenium(II,II) complex exhibits high diastereoselectivity without any chiral separation. While the hpp unit acts as a nucleophile in the mechanism of C-N cross coupling reaction, it can also act as a leaving group when activated as a monoruthenium complex. Achiral Ru(II) complexes of the tridentate ligands display improved photophysical properties over the prototype complex [Ru(tpy)2]2+ (tpy = 2,2’:6’,2’’-terpyridine). Introduction of two hpp units in the tridentate ligands renders the Ru(II) complex into a ‘black absorber’ and a ‘NIR emitter’ (NIR = Near Infra-Red). This fact is a consequence of better octahedral geometry around the Ru(II) ion and strong sigma-donation from the hpp units. The blue-emitting Re(I) complexes of the tridentate ligands also exhibit interesting redox behavior. The metal-based quasi-reversible oxidation is controlled by the sigma-donation from the hpp moieties, while the ligand-based reduction is governed by the electronic nature of the central N-heterocycle of the same ligand moiety. This thesis also incorporates self-assembly of metal-chromophores as ‘metallo-ligands’ to form discrete supramolecular species using neutral metal-complexes. The syntheses and properties of the aforesaid metal-chromophores and the supramolecules are discussed

p-i-n heterojunctions with BiFeO3 perovskite nanoparticles and p- and n-type oxides: photovoltaic properties.

We formed p-i-n heterojunctions based on a thin film of BiFeO3 nanoparticles. The perovskite acting as an intrinsic semiconductor was sandwiched between a p-type and an n-type oxide semiconductor as hole- and electron-collecting layer, respectively, making the heterojunction act as an all-inorganic oxide p-i-n device. We have characterized the perovskite and carrier collecting materials, such as NiO and MoO3 nanoparticles as p-type materials and ZnO nanoparticles as the n-type material, with scanning tunneling spectroscopy; from the spectrum of the density of states, we could locate the band edges to infer the nature of the active semiconductor materials. The energy level diagram of p-i-n heterojunctions showed that type-II band alignment formed at the p-i and i-n interfaces, favoring carrier separation at both of them. We have compared the photovoltaic properties of the perovskite in p-i-n heterojunctions and also in p-i and i-n junctions. From current-voltage characteristics and impedance spectroscopy, we have observed that two depletion regions were formed at the p-i and i-n interfaces of a p-i-n heterojunction. The two depletion regions operative at p-i-n heterojunctions have yielded better photovoltaic properties as compared to devices having one depletion region in the p-i or the i-n junction. The results evidenced photovoltaic devices based on all-inorganic oxide, nontoxic, and perovskite materials

Evaluation of feeds from tropical origin for in vitro methane production potential and rumen fermentation in vitro

Enteric methane arising due to fermentation of feeds in the rumen contributes substantially to the greenhouse gas emissions. Thus, like evaluation of chemical composition and nutritive values of feeds, methane production potential of each feed should be determined. This experiment was conducted to evaluate several feeds for methane production potential and rumen fermentation using in vitro gas production technique so that low methane producing feeds could be utilized to feed ruminants. Protein- and energy-rich concentrates (n=11), cereal and grass forages (n=11), and different straws and shrubs (n=12), which are commonly fed to ruminants in India, were collected from a number of locations. Gas production kinetics, methane production, degradability and rumen fermentation greatly varied (p<0.01) among feeds depending upon the chemical composition. Methane production (mL/g of degraded organic matter) was lower (p<0.01) for concentrate than forages, and straws and shrubs. Among shrubs and straws, methane production was lower (p<0.01) for shrubs than straws. Methane production was correlated (p<0.05) with concentrations of crude protein (CP), ether extract and non-fibrous carbohydrate (NFC) negatively, and with neutral detergent (NDF) and acid detergent fiber (ADF) positively. Potential gas production was negatively correlated (p=0.04) with ADF, but positively (p<0.01) with NFC content. Rate of gas production and ammonia concentration were influenced by CP content positively (p<0.05), but by NDF and ADF negatively (p<0.05). Total volatile fatty acid concentration and organic matter degradability were correlated (p<0.05) positively with CP and NFC content, but negatively with NDF and ADF content. The results suggest that incorporation of concentrates and shrubs replacing straws and forages in the diets of ruminants may decrease methane production

FPGA based Novel High Speed DAQ System Design with Error Correction

Present state of the art applications in the area of high energy physics experiments (HEP), radar communication, satellite communication and bio medical instrumentation require fault resilient data acquisition (DAQ) system with the data rate in the order of Gbps. In order to keep the high speed DAQ system functional in such radiation environment where direct intervention of human is not possible, a robust and error free communication system is necessary. In this work we present an efficient DAQ design and its implementation on field programmable gate array (FPGA). The proposed DAQ system supports high speed data communication (~4.8 Gbps) and achieves multi-bit error correction capabilities. BCH code (named after Raj Bose and D. K. RayChaudhuri) has been used for multi-bit error correction. The design has been implemented on Xilinx Kintex-7 board and is tested for board to board communication as well as for board to PC using PCIe (Peripheral Component Interconnect express) interface. To the best of our knowledge, the proposed FPGA based high speed DAQ system utilizing optical link and multi-bit error resiliency can be considered first of its kind. Performance estimation of the implemented DAQ system is done based on resource utilization, critical path delay, efficiency and bit error rate (BER).Comment: ISVLSI 2015. arXiv admin note: substantial text overlap with arXiv:1505.04569, arXiv:1503.0881

Panchromatic Ru(II)-polypyridyl complexes as NIR emitters

AKP thanks the Leverhulme Trust for an early career fellowship (ECF-2017-326), ScotCHEM for a short-term Postgraduate and Early Career Researcher Exchange (PECRE) fellowship and University of St Andrews for financial support. VNKBA thanks the UGC for a fellowship.Two novel mer-Ru(II) heteroleptic complexes containing stongly donating tridendate ligands (dgpy and dgpz) were synthesised and optoelectronically characterised. These complexes exhibited quasi-reversible ligand- and metal-based redox events and panchromatic absorption with the lowest energy absorption maxima trailing up to 750 nm. These panchromatic dyes were found to be NIR emissive at λPL ~ 835 nm with associated excited-state lifetimes (τPL) of ~ 10 ns. The enhanced photophysical properties of these complexes compared to those of [Ru(tpy)2]2+ (tpy = 2,2′:6′,2′′-terpyridine; λabs < 575 nm, λPL ~ 629 nm and τPL ~ 0.25 ns) are due to the larger 3MLCT-3MC energy-gap as a combined effect of larger bite angle and strong σ-donation offered by the dgpy and dgpz ligands.PostprintPeer reviewe

Bis(2,2′-bipyridine)(5-isothio­cyanato-1,10-phenanthroline)ruthenium(II) bis­(hexa­fluoridophosphate) acetonitrile solvate

The title compound, [Ru(C10H8N2)2(C13H7N3S)](PF6)2·CH3CN, was synthesized by the reaction of thio­phosgene and bis­(2,2′-bipyridine)(1,10-phenanthrolin-5-amine)ruthenium(II) bis­(hexa­fluoridophosphate). The RuII atom adopts a slightly distorted octa­hedral RuN6 coordinaton formed by four N atoms of two bipyridine ligands and by two N atoms of the 1,10-phenantroline ligand. The isothio­cyanate group is almost linear, with an N—C—S angle of 174.4 (6)°. Two of the three hexa­fluoridophosphate counter-anions are located on inversion centres