Bromination of Intermolecular Chelate Linkage Isomers of 3-Oximino-4,9-Dimethyl (or 4,7,9-Trimethyl)-5,8-Diazadodeca-4,8-Diene-2,11-Dionato Nickel(II)

The reaction of the title complexes (FIG. 1) with N-bromosuccinimide or bromine in chloroform yields isomeric bromo complexes on substitution of the γ-CH carbon proton by bromine. The brominated products have been characterised by ir, pmr, electronic absorption spectra, conductivity and magnetic susceptibility measurements. The linkage isomerisation of the brominated products in chloroform has been shown to depend on the diamine residue.

Assessment of luteal rescue and desensitization of macaque corpus luteum brought about by human chorionic gonadotrophin and deglycosylated human chorionic gonadotrophin treatment

The objective of the current study was to investigate the mechanism by which the corpus luteum (CL) of the monkey undergoes desensitization to luteinizing hormone following exposure to increasing concentration of human chorionic gonadotrophin (hCG) as it occurs in pregnancy. Female bonnet monkeys were injected (im) increasing doses of hCG or dghCG beginning from day 6 or 12 of the luteal phase for either 10 or 4 or 2 days. The day of oestrogen surge was considered as day '0' of luteal phase. Luteal cells obtained from CL of these animals were incubated with hCG (2 and 200 pg/ml) or dbcAMP (2.5, 25 and 100 mu M) for 3 h at 37 degrees C and progesterone secreted was estimated. Corpora lutea of normal cycling monkeys on day 10/16/22 of the luteal phase were used as controls, In addition the in vivo response to CG and deglycosylated hCG (dghCG) was assessed by determining serum steroid profiles following their administration. hCG (from 15-90 IU) but not dghCG (15-90 IU) treatment in vivo significantly (P < 0.05) elevated serum progesterone and oestradiol levels. Serum progesterone, however, could not be maintained at a elevated level by continuous treatment with hCG (from day 6-15), the progesterone level declining beyond day 13 of luteal phase. Administering low doses of hCG (15-90 IU/day) from day 6-9 or high doses (600 IU/day) on days 8 and 9 of the luteal phase resulted in significant increase (about 10-fold over corresponding control P < 0.005) in the ability of luteal cells to synthesize progesterone (incubated controls) in vitro. The luteal cells of the treated animals responded to dbcAMP (P < 0.05) but not to hCG added in vitro, The in vitro response of luteal cells to added hCG was inhibited by 0, 50 and 100% if the animals were injected with low (15-90 IU) or medium (100 IU) between day 6-9 of luteal phase and high (600 IU on day 8 and 9 of luteal phase) doses of dghCG respectively; such treatment had no effect on responsivity of the cells to dbcAMP, The luteal cell responsiveness to dbcAMP in vitro was also blocked if hCG was administered for 10 days beginning day 6 of the luteal phase. Though short term hCG treatment during late luteal phase (from days 12-15) had no effect on luteal function, 10 day treatment beginning day 12 of luteal phase resulted in regain of in vitro responsiveness to both hCG (P < 0.05) and dbcAMP (P < 0.05) suggesting that luteal rescue can occur even at this late stage. In conclusion, desensitization of the CL to hCG appears to be governed by the dose/period for which it is exposed to hCG/dghCG. That desensitization is due to receptor occupancy is brought out by the fact that (i) this can be achieved by giving a larger dose of hCG over a 2 day period instead of a lower dose of the hormone for a longer (4 to 10 days) period and (ii) the effect can largely be reproduced by using dghCG instead of hCG to block the receptor sites. It appears that to achieve desensitization to dbcAMP also it is necessary to expose the luteal cell to relatively high dose of hCG for more than 4 days.

Unusual Hydrogenation of Fumarate Anion Followed by Metal−Carbon Bond Formation: Synthesis and Characterization of Two Metallochelates

The treatment of [M(dppf)(H2O)2](OTf)2 (dppf =1,1′-bis(diphenylphosphino)ferrocene; M = Pd, Pt) with 1 equiv of disodium fumarate in methanol medium showed an unusual hydrogenation of the ethylenic bond followed by the formation of metallochelates linking M through one of the carboxylates and the β-carbon with respect to COO−. Despite the possibility of formation of a [2 + 2] or [4 + 4] self-assembled macrocycle, the reduction of fumarate to succinate, and in particular the linking through the β-carbon, is unique since a similar treatment using disodium succinate instead of disodium fumarate yielded an expected metallochelate where both the carboxylates were coordinated to the square-planar metal.

Reaction of carbon disulfide with azide ion

Carbon disulfide reacts with azide ion to form the 1,2,3,4-thiatriazolinethionate ion and not the acyclic azido dithiocarbonate ion as previously reported. A series of salts of thiatriazoline have been prepared and none shows evidence for the presence of the azido group. Esters of thiatriazolinethione prepared by the reaction of the sodium salt with alkyl or acyl halides have been found to be either 5-(substituted) mercapto-1,2,3,4-thiatriazoles or 4-substituted 1,2,3,4-thiatriazoline-5-thiones. These structures have been assigned on the basis of degradative and spectroscopic evidence. The chemistry of the so-called azidodithiocarbonates has been reinterpreted in terms of the thiatriazole structure.

Implications of rapid footpoint motions of photospheric flux tubes for coronal heating

Some recent observations at Pic-du-Midi (Mulleret al., 1992a) suggest that the photospheric footpoints of coronal magnetic field lines occasionally move rapidly with typical velocities of the order 3 km s–1 for about 3 or 4 min. We argue that such occasional rapid footpoint motions could have a profound impact on the heating of the quiet corona. Qualitative estimates indicate that these occasional rapid motions can account for the entire energy flux needed to heat the quiet corona. We therefore carry out a mathematical analysis to study in detail the response of a vertical thin flux tube to photospheric footpoint motions in terms of a superposition of linear kink modes for an isothermal atmosphere. We find the resulting total energy that is asymptotically injected into an isothermal atmosphere (i.e., an atmosphere without any back reflection). By using typical parameter values for fast and slow footpoint motions, we show that, even if the footpoints spend only 2.5% of the time undergoing rapid motions, still these rapid motions could be more efficient in transporting energy to the corona than the slow motions that take place most of the time.

Second harmonic generation in poled molecularly doped polymer films : Push-pull butadienes in poly(methyl methacrylate) and polystyrene

We report second harmonic generation in a new class of organic materials, namely donor-acceptor substituted all-trans butadienes doped in poly(methyl methacrylate) or polystyrene and oriented by corona poling at elevated temperatures. Second harmonic measurements were made at room temperature. The observed d33 coefficients are greater than those of potassium dihydrogen phosphate or 4-dimethylamino-4'-nitrostilbene doped in similar polymer matrices. Rotational diffusion coefficients estimated from the decay characteristics of the second harmonic intensity in the polymer films indicate that the polymer matrix plays a major role in stabilizing the dopants in a nonlinear optics conducive environment.

Terpyridine Oxovanadium(IV) Complexes of Phenanthroline Bases for Cellular Imaging and Photocytotoxicity in HeLa Cells

Oxovanadium(IV) complexes VO(N-N-N)(N-N)](NO3)(2) (1-4) of (4'-phenyl)-2,2': 6',2 `'-terpyridine (ph-tpy in 1 and 2) or (4'-pyrenyl)-2,2':6',2 `'-terpyridine (py-tpy in 3 and 4) having N-N as 1,10-phenanthroline (phen in 1 and 3) or dipyrido3,2-a:2',3'-c]phenazine (dppz in 2 and 4) are prepared and characterized. The crystal structure of 1 has VO2+ group in VN5O coordination geometry. The terpyridine ligand coordinates in a meridional binding mode. The phen ligand displays a chelating mode of binding with an N-donor site trans to the vanadyl oxo group. The complexes show a d-d band in the range of 710-770 nm in aqueous DMF (4:1 v/v). The complexes exhibit an irreversible V-IV/V-III redox response near -1.0 V vs. SCE in aqueous DMF/0.1 M KCl. The complexes bind to CT DNA giving K-b values within 3.5 x 10(5) to 1.2 x 10(6) M-1. The complexes show poor chemical nuclease activity in dark. Complexes 2-4 show photonuclease activity in UV-A light of 365 nm forming O-1(2) and (OH)-O-center dot. Complex 4 shows DNA photocleavage activity at near-IR light of 785 nm forming (OH)-O-center dot radicals. Complexes 2 and 4 show significant photocytotoxicity in HeLa cancer cells. Uptake of the complexes in HeLa cells, studied by fluorescence imaging, show predominantly cytosolic localization inside the cells.

Rearrangements in the cerium(IV) and manganese(III) oxidations of substituted naphthalenes and the nih shift mechanism

Ceric ammonium sulphate oxidation of 1- and 1,4- disubstituted naphthalenes gives 2- and/or 2,3- disubstituted 1,4- naphthoquinones through migration of substituents (D, Br, Ph). Similar rearrangements are also observed in the manganese(III) oxidation and also in the anodic oxidation of these substrates. The results are consistent with the proposal that these oxidations go through the formation of radical cation followed by reaction with H2O and further oxidation of the radical to the carbocationic intermediate on the way to the corresponding 1,4-naphthoquinone. Oxidation of 1,4-diphenylnaphthalene gives 2,3-diphenyl-1,4-naphthoquinone or 4-hydroxy- 2,4- diphenyl - 1(4)R - naphthalenone. The results are in accordance with the conclusion that such rearrangements do not require prior formation of arene oxide intermediates, originally proposed for the NM shift mechanism.

Selectivities in the formation of pyridines and pyrimidines by ammonia-induced cyclocondensations of vinamidiniums

Arylvinamidines (2-, 3- or 4-aryl-4-(N,N-dimethyl)amino-1-azabuta-1,3-dienes), generated from 1,1,5,5-tetramethyl-2- or -3-phenyl-1,5-diazapentadienium salts, cyclocondense orientation-specifically under two regioselections forming 1-4' + 4-3' and 1-2' + 4-1' bonds on exposure to ammonia. The initial cyclates aromatise eliminatively to give mixtures of diarylpyridines and arylpyrimidines. The 2-arylvinamidines do not participate as 2-centre reactants and their 4-aryl isomers not as 4-centre reactants in the cyclocondensations which appear to be stepwise and not concerted. Reasons for the selective participation appear to be that the required eliminations from the initial cyclates are disfavoured in the first case and that a geometric factor prevents cyclate-formation in the second.

A simple strategy for spirocyclopentannullation of cyclic ketones. Formal total synthesis of (+/-)-acorone

A general and simple methodology for spirocyclopentannulation of cyclic ketones (or 4,4-disubstituted cyclopentenones from acyclic ketones) and its application in the synthesis of the spirodienone 7 via a prochiral precursor constituting a formal total synthesis of (+/-)-acorone (6), are described.

meso-substituted octabromoporphyrins: Synthesis, spectroscopy, electrochemistry and electronic structure

The free-base, copper(II) and zinc(II) derivatives of 5,10,15,20-tetraarylporphyrin (aryl = phenyl, 4-methylphenyl or 4-chlorophenyl) and the corresponding brominated 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraarylporphyrin derivatives have been synthesized and their spectral and redox properties compared by UV/VIS, H-1 NMR, ESR and cyclic voltammetric methods. Substitution with the electron-withdrawing bromine groups at the pyrrole carbons has a profound influence on the UV/VIS and H-1 NMR spectral features and also on the redox potentials of these systems. On the other hand, electron-withdrawing chloro or electron-donating methyl groups at the para positions of the four phenyl rings have only a marginal effect on the spectra and redox potentials of both the brominated and the non-brominated derivatives. The ESR data for the copper(II) derivatives of ail these systems reveal that substitution at either the beta-pyrrole carbons and/or the para positions of the meso-phenyl groups does not significantly affect the spin-Hamiltonian parameters that describe the metal centre in each case. Collectively, these observations suggest that the highest-occupied (HOMO) and lowest-unoccupied molecular orbitals (LUMO) of the octabromoporphyrins involve the porphyrin pi-ring system as is the case with the non-brominated derivatives.-Investigations have been carried out to probe the electronic structures of these systems by three different approaches involving spectral and redox potential data as well as AMI calculations. The results obtained suggest that the electron-withdrawing beta-bromine substituents stabilize the LUMOs and, to a lesser degree, the HOMOs and that the extent of these changes can be fine-tuned, in a subtle way, by substituting at the meso-aryl rings of a given porphyrin.

Synthesis, properties and crystal structures of diastereomeric areneruthenium(II) chiral Schiff-base complexes

Diastereomers (SRu,Sc)-1a and (RRu,Sc)-1b, in a ratio of 85: 15 and formulated as [Ru(η-MeC6H4Pri-p)Cl(L*)], have been prepared by treating [{Ru(η-MeC6H4Pri-p)Cl2}2] with the sodium salt of (S)-α-methylbenzylsalicylaldimine (HL*) in tetrahydrofuran at –70 °C. The reaction of 1(1a+1b) with AgClO4 in acetone followed by an addition of PPh3 or 4-methylpyridine (4Me-py) leads to the formation of adducts [Ru(η-MeC6H4Pri-p)(PPh3)(L*)]ClO42[(SRu,Sc)2a, (FRu,Sc)2b] and [Ru(η-MeC6H4Pri-p)(4Me-py)(L*)]ClO43[(SRu,Sc)3a, (RRu,Sc)3b] in the diastereomeric ratios (SRu,Sc) : (RRu,Sc) of 2 : 98 and 76 : 24, respectively. Complex 1 crystallises with equal numbers of 1a and 1b molecules in an asymmetric unit of monoclinic space group P21 with a= 10.854(1), b= 17.090(1), c= 12.808(4)Å, β= 110.51(1)°, and Z= 4. The structure was refined to R= 0.0552 and R′= 0.0530 with 2893 reflections having I[gt-or-equal] 1.5σ(I). The absolute configurations of the chiral centres in the optically pure single crystal of the PPh3 adduct have been obtained from an X-ray study. Crystals of formulation [Ru(η-MeC6H4Pri-p)-(PPh3)(L*)]2[ClO4][PF6]·1.5 CHCl3, obtained in presence of both ClO4 and PF6 anions, belong to the non-centric triclinic space group P1 with a= 10.852(2), b= 14.028(1), c= 15.950(2)Å, α= 91.51(1), β= 105.97(1), γ= 106.11(1)°, and Z= 2. The final residuals were R= 0.0713, R′= 0.0752 with 7283 reflections having I[gt-or-equal] 2.5σ(I). The crystal structures of 1a,1b, and the PPh3 adduct (2b,2b′) consist of a ruthenium(II) centre bonded to a η-p-cymene, a bidentate chelating Schiff base, and a unidentate ligand (Cl or PPh3). The chirooptical properties of the complexes have been studied using 1H NMR and CD spectral data. The presence of a low-energy barrier for the intermediate involved in these reactions, showing both retention as well as inversion of the metal configuration, is discussed.

Diphenylantimony(V) oxo/chloro carboxylates and phosphinates: crystal structures of {SbPh2Cl[O2P(C6H11)2]}2O and [SbPh2(O2CPh)2]2O

Reaction of SbPh(2)Cl(3) (1 mol) with the silver salt of dicyclohexylphosphinic acid (2 mol) afforded {SbPh(2)Cl[O2P(C6H11)(2)]}O-2 1, a similar reaction with AgO2P(C8H15)(2) gave a product formulated as {SbPh(2)Cl[O2P(C8H15)(2)]}O-2 2. Similar reactions with silver carboxylates (1:3 stoichiometry) led to the crystalline derivatives [SbPh(2)(O(2)CR)(2)]O-2 (R = Ph 3, CHPh(2) 4, 2,4,6-Me(3)C(6)H(2) 5, 2-MeC(6)H(4) 6 or 4-MeC(6)H(4) 7), whereas the 1:2 reaction afforded crystalline SbPh(2)Cl(O(2)CR)(2) (R = Ph 8, 2-MeC(6)H(4) 9 or 4-MeC(6)H(4) 10). Interconversion of the previously known compounds [SbPh(2)(O(2)CMe)(2)]O and Sb(4)Ph(8)O(6) . 3MeCO(2)H was achieved and established by H-1 NMR spectroscopy. Compounds 1 and 3 were further characterized by X-ray diffraction; the antimony in 1 is six-co-ordinated with bridging phosphinates whereas in 3 it is seven-co-ordinated with chelating benzoates. Short Sb-O (oxo) distances (1.923 Angstrom) and near linearity at the bridging ox

Localized data gathering paradigms for small and marginal farm lands in Semi-Arid region – Issues and Concerns

In this work we explore the application of wireless sensor technologies for the benefit of small and marginal farmers in semi-arid regions. The focus in this paper is to discuss the merits and demerits of data gathering & relay paradigms that collect localized data over a wide area. The data gathered includes soil moisture, temperature, pressure, rain data and humidity. The challenge to technology intervention comes mainly due to two reasons: (a) Farmers in general are interested in crop yield specific to their piece of land. This is because soil texture can vary rapidly over small regions. (b) Due to a high run-off, the soil moisture retention can vary from region to region depending on the topology of the farm. Both these reasons alter the needs drastically. Additionally, small and marginal farms can be sandwiched between rich farm lands. The village has very little access to grid power. Power cuts can extend up to 12 hours in a day and upto 3 or 4 days during some months in the year. In this paper, we discuss 3 technology paradigms for data relaying. These include Wi-Fi (Wireless Fidelity), GPRS (General Packet Radio Service) and DTN (Delay and Disruption Tolerant Network) technologies. We detail the merits and demerits of each of these solutions and provide our final recommendations. The project site is a village called Chennakesavapura in the state of Karnataka, India.

Role of spacer lengths of gemini surfactants in the synthesis of silver nanorods in micellar media

In this work, we have prepared Ag-nanorods using biscationic gemini surfactant micelles as the media by a seed-mediated wet synthesis method. Towards this end, we first synthesized Ag-nanoseeds of diameter similar to 7 nm stabilized by trisodium citrate (as the capping agent). Then these Ag-nanoseeds were used to synthesize Ag-nanorods of different aspect ratios. With decreasing Ag-nanoseed concentration, the aspect ratios of the Ag-nanorods stabilized by these gemini surfactants increased gradually. Various Ag-nanoseeds and Ag-nanospecies were characterized using UV-Vis spectroscopy (to know the surface plasmon bands), transmission electron microscopy (to find out their particle sizes and distribution), energy-dispersive X-ray spectroscopy and X-ray diffraction. When we used micelles derived from gemini surfactants of shorter spacer-(CH(2))(n)-(n = 2 or 4) to stabilize the Ag-nanorods, the lambda(max) of the longitudinal band shifted more towards the blue region compared to that of the gemini surfactant micelles with a longer spacer-(CH(2))(n)-(n = 5, 12) at a given amount of the Ag-nanoseed solution. So, the growth of Ag-nanorods in the gemini micellar solutions depends on the spacer-chain length of gemini surfactants employed.