Synthesis and unexpected reactivity of Ru(eta(6)-cymene)Cl-2(PPh2Cl)], leading to Ru(eta(6)-cymene)Cl-2(PPh2H)] and Ru(eta(6)-cymene)Cl-2(PPh2OH)] complexes

The reaction of Ru(eta(6)-cymene)Cl-2](2) and PPh2Cl in the ratio 1:2 gives a stable Ru(h(6)-cymene) Cl-2(PPh2Cl)] complex. Attempts to make the cationic Ru(eta(6)-cymene)Cl(PPh2Cl)(2)]Cl with excess PPh2Cl and higher temperatures led to adventitious hydrolysis and formation of Ru(eta(6)-cymene)Cl-2(PPh2OH)]. Attempts to make a phosphinite complex by reacting Ru(eta(6)-cymene)Cl-2](2) with PPh2Cl in the presence of an alcohol results in the reduction of PPh2Cl to give Ru(eta(6)-cymene)Cl-2(PPh2H)] and the expected phosphinite. The yield of the hydride complex is highest when the alcohol is 1-phenyl-ethane-1,2-diol. All three half-sandwich complexes are characterized by X-ray crystallography. Surprisingly, the conversion of chlorodiphenylphosphine to diphenylphosphine is mediated by 1-phenyl-ethane-1,2-diol even in the absence of the ruthenium half-sandwich precursor.

H2O-CH4 and H2S-CH4 complexes: a direct comparison through molecular beam experiments and ab initio calculations

New molecular beam scattering experiments have been performed to measure the total ( elastic plus inelastic) cross sections as a function of the velocity in collisions between water and hydrogen sulfide projectile molecules and the methane target. Measured data have been exploited to characterize the range and strength of the intermolecular interaction in such systems, which are of relevance as they drive the gas phase molecular dynamics and the clathrate formation. Complementary information has been obtained by rotational spectra, recorded for the hydrogen sulfide-methane complex, with a pulsed nozzle Fourier transform microwave spectrometer. Extensive ab initio calculations have been performed to rationalize all the experimental findings. The combination of experimental and theoretical information has established the ground for the understanding of the nature of the interaction and allows for its basic components to be modelled, including charge transfer, in these weakly bound systems. The intermolecular potential for H2S-CH4 is significantly less anisotropic than for H2O-CH4, although both of them have potential minima that can be characterized as `hydrogen bonded'.

Endoplasmic reticulum targeting tumour selective photocytotoxic oxovanadium(IV) complexes having vitamin-B6 and acridinyl moieties

Oxovanadium(IV) complexes of vitamin-B6 Schiff base, viz., VO(HL1/L-2/L-3)(B)] Cl (1-4), where B is 2,2'-bipyridine (bpy in 1 and 2), 11-(9-acridinyl)dipyrido3,2-a:2',3'-c]phenazine (acdppz in 3 and 4), H2L1 center dot HCl is 3-hydroxy-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylp yridin-1-ium chloride (in 1 and 4), HL2 is 2-(((2-(1H-imidazol-4-yl)ethyl) imino)methyl) phenol (in 2) and HL3 is 4-(((2-(1H-imidazol-4- yl)ethyl)imino)methyl)-5-(hydroxymethyl)-2-methylpyridin-3-ol (in 3) were synthesized, characterized and their cellular uptake, photo-activated cytotoxicity and intracellular localization were studied. Complexes 1a, as the perchlorate salt of 1, and 2a, as the hexafluorophosphate salt of 2, were structurally characterized. Vitamin-B6 transporting membrane carrier (VTC) mediated entry into tumour cells in preference to the normal ones seems to be responsible for the higher cellular uptake of the complexes into HeLa and MCF-7 cells over MCF-10A cells. Complexes 3 and 4 having acdppz as the photosensitizer exhibit remarkable photocytotoxicity in these cancer cells giving IC50 of < 0.9 mu M. The complexes remain non-toxic in the dark. The complexes show photo-induced apoptotic cell death via singlet oxygen (O-1(2)) generation. Fluorescence microscopy reveals specific localization of complex 4 to endoplasmic reticulum (ER) and generation of O-1(2) possibly leads to apoptotic cell death by triggering ER stress response (ERSR).

Photocytotoxic luminescent lanthanide complexes of DTPA-bisamide using quinoline as photosensitizer

Lanthanide complexes Ln(DTPAAQ)(DMF)] (1-3) (Ln - Pr (1), Eu (2), Tb (3), H(3)DTPAAQ - N, N `'-bis(3-amidoquinolyl) diethylenetriamine-N, N', N `'-triacetic acid, DMF - N, N-dimethylformamide) were studied for their structures, photophysical properties, DNA and protein binding, DNA photocleavage, photocytotoxicity and cellular internalization. The crystal structures of complexes Ln(DTPAAQ)(DMF)] (1-3) display a discrete mononuclear nine-coordinate {LnN(3)O(6)} tricapped-trigonal prism (TTP) coordination geometry. The europium and terbium complexes show strong luminescence properties in the visible region having a long luminescence lifetime (tau = 0.51-0.64 ms). The conjugated 3-aminoquinoline moieties act as efficient light harvesting antennae, which upon photoexcitation transfer their energy to Eu(III) or Tb(III) for their characteristic D-5(0) -> F-7(J) or D-5(4) -> F-7(J) f-f transitions respectively. The complexes display efficient binding affinity to DNA (K-b = 3.4 x 10(4) - 9.8 x 10(4) M-1) and BSA (KBSA = 3.03 x 10(4) - 6.57 x 10(4) M-1). Europium and terbium complexes give enhanced luminescence upon interacting with CT-DNA suggesting possible luminescence-based sensing applications for these complexes. Complexes 1-3 show moderate cleavage of supercoiled (SC) DNA to its nicked circular (NC) form on exposure to UV-A light of 312 nm involving formation of singlet oxygen (O-1(2)) and hydroxyl radicals (cOH) in type-II and photoredox pathways. Eu(III) and Tb(III) complexes exhibit remarkable photocytotoxicity with human cervical cancer cell line (HeLa) (IC50 = 20.7-28.5 mM) while remaining essentially noncytotoxic up to 150 mM in the dark. Complexes are nontoxic in nature thus suitable for designing cellular imaging agents. Fluorescence microscopy data reveal primarily cytosolic localization of the Eu(III) and Tb(III) complexes in HeLa cells.

Endoplasmic reticulum targeting tumour selective photocytotoxic oxovanadium(IV) complexes having vitamin-B6 and acridinyl moieties

Oxovanadium(IV) complexes of vitamin-B6 Schiff base, viz., VO(HL1/L-2/L-3)(B)] Cl (1-4), where B is 2,2'-bipyridine (bpy in 1 and 2), 11-(9-acridinyl)dipyrido3,2-a:2',3'-c]phenazine (acdppz in 3 and 4), H2L1 center dot HCl is 3-hydroxy-5-(hydroxymethyl)-4-(((2-hydroxyphenyl)imino)methyl)-2-methylp yridin-1-ium chloride (in 1 and 4), HL2 is 2-(((2-(1H-imidazol-4-yl)ethyl) imino)methyl) phenol (in 2) and HL3 is 4-(((2-(1H-imidazol-4- yl)ethyl)imino)methyl)-5-(hydroxymethyl)-2-methylpyridin-3-ol (in 3) were synthesized, characterized and their cellular uptake, photo-activated cytotoxicity and intracellular localization were studied. Complexes 1a, as the perchlorate salt of 1, and 2a, as the hexafluorophosphate salt of 2, were structurally characterized. Vitamin-B6 transporting membrane carrier (VTC) mediated entry into tumour cells in preference to the normal ones seems to be responsible for the higher cellular uptake of the complexes into HeLa and MCF-7 cells over MCF-10A cells. Complexes 3 and 4 having acdppz as the photosensitizer exhibit remarkable photocytotoxicity in these cancer cells giving IC50 of < 0.9 mu M. The complexes remain non-toxic in the dark. The complexes show photo-induced apoptotic cell death via singlet oxygen (O-1(2)) generation. Fluorescence microscopy reveals specific localization of complex 4 to endoplasmic reticulum (ER) and generation of O-1(2) possibly leads to apoptotic cell death by triggering ER stress response (ERSR).

Delineation of homogeneous hydrometeorological regions using wavelet-based global fuzzy cluster analysis

Identification of homogeneous hydrometeorological regions (HMRs) is necessary for various applications. Such regions are delineated by various approaches considering rainfall and temperature as two key variables. In conventional approaches, formation of regions is based on principal components (PCs)/statistics/indices determined from time series of the key variables at monthly and seasonal scales. An issue with use of PCs for regionalization is that they have to be extracted from contemporaneous records of hydrometeorological variables. Therefore, delineated regions may not be effective when the available records are limited over contemporaneous time period. A drawback associated with the use of statistics/indices is that they do not provide effective representation of the key variables when the records exhibit non-stationarity. Consequently, the resulting regions may not be effective for the desired purpose. To address these issues, a new approach is proposed in this article. The approach considers information extracted from wavelet transformations of the observed multivariate hydrometeorological time series as the basis for regionalization by global fuzzy c-means clustering procedure. The approach can account for dynamic variability in the time series and its non-stationarity (if any). Effectiveness of the proposed approach in forming HMRs is demonstrated by application to India, as there are no prior attempts to form such regions over the country. Drought severity-area-frequency (SAF) curves are constructed corresponding to each of the newly formed regions for the use in regional drought analysis, by considering standardized precipitation evapotranspiration index (SPEI) as the drought indicator.

Photocytotoxic ternary copper(II) complexes of histamine Schiff base and pyridyl ligands

Ternary copper(Il) complexes of salicylaldehyde-histamine Schiff base (HL) and pyridyl ligands, viz. Cu(bpy)(L)](ClO4) (1) and Cu(dppz)(L)](C104) (2), where bpy is 2,2'-bipyridine (in 1) and dppz is dipyrido3,2-a:2',3'-c]phenazine (in 2), were synthesized, characterized and their DNA binding, photo-activated DNA cleavage activity and photocytotoxicity studied. The 1:1 electrolytic one-electron paramagnetic complexes showed a d-d band near 670 nm in aqueous DMF (1:1 v/v). The crystal structure of complex 1 showed the metal in CuN4O distorted square-pyramidal geometry. Complex 2 intercalatively binds to calf-thymus (ct) DNA with a binding constant (K-b) of similar to 10(5) M-1. It exhibited moderate chemical nuclease activity but excellent DNA photocleavage activity in red light of 647 nm forming (OH)-O-center dot radicals. It showed remarkable photocytotoxicity in human cervical cancer cells (HeLa) giving IC50 of 1.6 mu M in visible light (400-700 nm) with low dark toxicity. The photo-induced cell death is via generation of oxidative stress by reactive oxygen species.

Flow Investigation of Linear Cluster Plug Nozzle

Computational and experimental tools have been used to understand the linear cluster plug nozzle flowfield for a range of pressure ratios. The experimental cluster configuration is arrived at from a linear plug nozzle by introducing splitter plates in the primary nozzle, and computational analysis of corresponding geometry is also carried out. The flow development on the plug surface has been analyzed for two different cluster module spacings. The interactions between the cluster module jets is a complex one with a three-dimensional shock structure because of the differential end condition the shock experiences on the plug wall and freejet boundary. A prominent streamwise vorticity resulting from curvature of the shock is also seen along the length of the plug downstream of the module junctions. The out-of-phase wave interactions occurring along the module centerline and the splitter plate centerline, resulting in a wavy surface-limiting streamline pattern, particularly at lower pressure ratios, is explained.

Remarkable photo-induced anticancer activity of vitamin-S6 Schiff base copper(II) complexes of pyridyl bases

Vitamin-B6 (VB6) Schiff base (H2L) copper(II) complexes of pyridyl bases, viz. Cu(bpy)(L)] (1), Cu(phen)(L)] (2) and Cu(dppz)(L)] (3), where bpy is 2,2'-bipyridine, phen is 1,10-phenanthroline and dppz is dipyrido3,2-a:2',3'c]phenazine are synthesized, characterized and their phto-induced anticancer activity studied. The non-electrolytic one electron paramagnetic complexes exhibit a d-d band near 700 nm in DMF. The dppz complex intercalatively binds to calf-thymus DNA with binding constant (K-b) values of similar to 10(6) M-1. This complex exhibits low chemical nuclease activity but excellent DNA photocleavage activity when irradiated with red light of 705 nm forming (OH)-O-center dot radical. It displays remarkable photocytotoxicity in human cervical cancer cells (HeLa) giving IC50 value of 0.9 mu M in visible light (400-700 nm) while being less toxic in darkness (IC50 : 23 mu M). The cellular uptake of the complexes seems to be via VB6 transporting membrane carrier mediated diffusion pathway. Photo-induced cell death follows apoptotic pathway involving photo-generated intracellular reactive oxygen species.

Cold gas in cluster cores: global stability analysis and non-linear simulations of thermal instability

We perform global linear stability analysis and idealized numerical simulations in global thermal balance to understand the condensation of cold gas from hot/virial atmospheres (coronae), in particular the intracluster medium (ICM). We pay particular attention to geometry (e.g. spherical versus plane-parallel) and the nature of the gravitational potential. Global linear analysis gives a similar value for the fastest growing thermal instability modes in spherical and Cartesian geometries. Simulations and observations suggest that cooling in haloes critically depends on the ratio of the cooling time to the free-fall time (t(cool)/t(ff)). Extended cold gas condenses out of the ICM only if this ratio is smaller than a threshold value close to 10. Previous works highlighted the difference between the nature of cold gas condensation in spherical and plane-parallel atmospheres; namely, cold gas condensation appeared easier in spherical atmospheres. This apparent difference due to geometry arises because the previous plane-parallel simulations focused on in situ condensation of multiphase gas but spherical simulations studied condensation anywhere in the box. Unlike previous claims, our non-linear simulations show that there are only minor differences in cold gas condensation, either in situ or anywhere, for different geometries. The amount of cold gas depends on the shape of tcool/tff; gas has more time to condense if gravitational acceleration decreases towards the centre. In our idealized plane-parallel simulations with heating balancing cooling in each layer, there can be significant mass/energy/momentum transfer across layers that can trigger condensation and drive tcool/tff far beyond the critical value close to 10.

Influence of cluster-assembly parameters on the field emission properties of nanostructured carbon films

Supersonic cluster beam deposition has been used to produce films with different nanostructures by controlling the deposition parameters such as the film thickness, substrate temperature and cluster mass distribution. The field emission properties of cluster-assembled carbon films have been characterized and correlated to the evolution of the film nanostructure. Threshold fields ranging between 4 and 10 V/mum and saturation current densities as high as 0.7 mA have been measured for samples heated during deposition. A series of voltage ramps, i.e., a conditioning process, was found to initiate more stable and reproducible emission. It was found that the presence of graphitic particles (onions, nanotube embryos) in the films substantially enhances the field emission performance. Films patterned on a micrometer scale have been conditioned spot by spot by a ball-tip anode, showing that a relatively high emission site density can be achieved from the cluster-assembled material. (C) 2002 American Institute of Physics.

Fabrication of 25nm wide gold lines using nanometer scale lithography and ionized cluster beam deposition

It becomes increasingly difficult to make continuous metal lines with well defined thickness and edges by the lift-off technique as the line width is decreased. We describe in this paper a technique in which the combination of high resolution electron beam lithography and ionized cluster beam (ICB) deposition has enabled very high quality gold lines ({all equal to}25nm wide) to be obtained on thick single crystal silicon substrates. © 1990.