bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses, Structures, and Luminescent Properties of [Bis(iminoalkyl)pyridine]cadmium(II) Complexes
Authors: Fan Rui‐Qing , Zhu Dong‐Sheng , Mu Ying , Li Guang‐Hua , Yang Yu‐Lin , Su Qing , Feng Shou‐Hua 
Published: October 2004

AbstractFour new CdII complexes of 2,6‐bis[1‐(phenylimino)ethyl]pyridine (L1), 2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine (L2), 2,6‐bis[1‐(2,6‐dimethylphenylimino)ethyl]pyridine (L3), 2,6‐bis[1‐(2‐methylphenylimino)ethyl]pyridine (L4) have been synthesized. These complexes have the formulas [Cd(L1)Cl2]·1.5CH3CN (1), [Cd(L2)Cl2] (2), [Cd(L3)Cl2]·CH3CN (3), and [Cd(L4)Cl2]·CH3CN (4). The molecular structures of complexes 1−4 were determined by single‐crystal X‐ray diffraction. Crystallographic studies of 1−4 reveal all four complexes to be five‐coordinate with geometries that can be best described as distorted trigonal‐bipyramidal. All eight compounds (L1−L4 and 1−4) are luminescent at room temperature in solution and the solid state. At 298 K in dichloromethane solution, all compounds have fluorescent emissions at about 368−409 nm. The fluorescent emission of these compounds originates from ligand‐centered π*−π transitions. The CdII centers play a key role in enhancing the fluorescent emission of the ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis, X‐ray Crystal Structure and Magnetic Properties of Oxalato‐Bridged Copper(II) Complexes with 2,3‐Bis(2‐pyridyl)pyrazine, 2,3‐Bis(2‐pyridyl)quinoxaline and 2,2′‐Bipyrazine as Peripheral Ligands
Authors: Carranza José , Grove Hilde , Sletten Jorunn , Lloret Francesc , Julve Miguel , Kruger Paul E. , Eller Chad , Rillema D. Paul 
Published: October 2004

AbstractFive oxalate‐containing copper(II) complexes of formula [Cu(dpq)(H2O)(ox)]·5H2O (1), [Cu(dpp)(H2O)(ox)]·H2O (2), [Cu(bpz)(ox)]n (3), [Cu2(dpp)2(H2O)2(NO3)2(ox)]·4H2O (4) and [Cu2Cl2(bpz)2(H2O)2(ox)][Cu(bpz)(H2O)2(ox)]·2H2O (5) [dpq = 2,3‐bis(2‐pyridyl)quinoxaline; dpp = 2,3‐bis(2‐pyridyl)pyrazine; bpz = 2,2′‐bipyrazine; ox = oxalate] were prepared and their structures were determined by X‐ray diffraction on single crystals. Complexes 1 and 2 are discrete mononuclear complexes with oxalate and dpq (1)/dpp (2) acting as bidentate ligands. Complex 3 is a neutral oxalato‐bridged (2,2′‐bipyrazine)copper(II) chain where the oxalate adopts a bidentate/monodentate coordination mode, whereas 4 is an oxalato‐bridged copper(II) dinuclear complex with ox and dpp acting as bis‐bidentate and bidentate ligands, respectively. The structure of 5 contains neutral [Cu(bpz)(H2O)2(ox)] (mononuclear) and [Cu2(bpz)2(H2O)2Cl2(ox)] (dinuclear) units where the bpz acts as a bidentate ligand and the oxalate group adopts the bidentate (mononuclear) and bis‐bidentate (dinuclear) coordination modes. The copper atoms have distorted square pyramidal (1 and 2) and elongated octahedral (3−5) geometries: two nitrogen atoms from heterocyclic N‐donors and two oxalate‐oxygen atoms occupy the equatorial positions (1−5) and a water molecule (1 and 2), two oxalate‐oxygen atoms (3), a water molecule and a nitrate‐oxygen (4), and either two water molecules (5), mononuclear) or a chlorine atom and a water molecule (5, dinuclear) fill the axial ones. Magnetic susceptibility measurements for 3−5 in the temperature range 1.9−290 K reveal the occurrence of weak (J = −1.4 cm−1, 3) and strong (−312 and −345 cm−1 for 4 and 5, respectively; Hˆ = −J·SˆA·SˆB) antiferromagnetic interactions between the copper(II) atoms in agreement with the out‐of‐plane (3) and in‐plane (4 and 5) exchange pathways involved. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Mechanistic Investigation of the Oxidation of Glyoxylic and Pyruvic Acids by Tris(biguanide)manganese(IV) in Weakly Acidic Aqueous Media
Authors: Dhar Basab Bijayi , Mukherjee Ritam , Mukhopadhyay Subrata , Banerjee Rupendranath 
Published: October 2004

AbstractIn this study the kinetics of two electron transactions between the reducing substrates glyoxylic and pyruvic acids and the oxidising complex cation, tris(biguanide)manganese(IV) in aqueous acidic media have been examined. Under the experimental conditions (pH = 1.50−3.78) only the fully protonated form of the oxidant reacts with the anions of the substrates whereas the parent acids, viz. glyoxylic and pyruvic acids, were found to be unreactive. The second‐order rate constants for the oxidations of glyoxylate and pyruvate by the title MnIV species are (2.24 ± 0.10) × 10−1 and (5.40 ± 0.30) × 10−2 M−1s−1, respectively, at 25.0 °C and at I = 1.0 M (NaNO3 or NaClO4). A rate‐liming one‐electron change between the redox partners seems justified. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Enantiomerically Pure Thrombin Inhibitors for Exploring the Molecular‐Recognition Features of the Oxyanion Hole
Authors: Schärer Kaspar , Morgenthaler Martin , Seiler Paul , Diederich François , Banner David W. , Tschopp Thomas , Obst‐Sander Ulrike 
Published: October 2004

AbstractA new route via intermediate pseudoenantiomers was developed to synthesize racemic and enantiomerically pure new non‐peptidic inhibitors of thrombin, a key serine protease in the blood‐coagulation cascade. These ligands feature a conformationally rigid tricyclic core and are decorated with substituents to fill the major binding pockets (distal (D), proximal (P), selectivity (S1), and oxyanion hole) at the thrombin active site (Fig. 1). The key step in the preparation of the new inhibitors is the 1,3‐dipolar cycloaddition between an optically active azomethine ylide, prepared in situ from L‐(4R)‐hydroxyproline and 4‐bromobenzaldehyde, and N‐piperonylmaleimide (Scheme 1). According to this protocol, tricyclic imide (compounds (±)‐15‐(±)‐18 and (+)‐21) and lactam (compound (+)‐2) inhibitors with OH or ether substituents at C(7) in the proline‐derived pyrrolidine ring were synthesized to specifically explore the binding features of the oxyanion hole (Schemes 2–4). Biological assays (Table) showed that the polar oxyanion hole in thrombin is not suitable for the accommodation of bulky substituents of low polarity, thereby confirming previous findings. In contrast, tricyclic lactam (+)‐2 (Ki=9 nM, Ki(trypsin)/Ki(thrombin)=1055) and tricyclic imide (+)‐21 (Ki=36 nM, Ki(trypsin)/Ki(thrombin)=50) with OH‐substituents at the (R)‐configured C(7)‐atom are among the most‐potent and most‐selective thrombin inhibitors in their respective classes, prepared today. While initial modeling predicted H‐bonding between the OH group at C(7) in (+)‐2 and (+)‐21 with the H2O molecule bound in the oxyanion hole (Fig. 2), the X‐ray crystal structure of the complex of (+)‐21 (Fig. 7, b) revealed a different interaction for this group. The propionate side chain of Glu192 undergoes a conformational change, thereby re‐orienting towards the OH group at C(7) under formation of a very short ionic H‐bond (OH⋅⋅⋅−OOC; d(O⋅⋅⋅O)=2.4 Å). The energetic contribution of this H‐bond, however, is negligible, due to its location on the surface of the protein and the unfavorable conformation of the H‐bonded propionate side chain.
Preparation and Characterization of New Phosphonyl‐Substituted Imidazolium Ionic Liquids
Authors: Mu Zong‐gang , Zhou Feng , Zhang Shu‐xiang , Liang Yong‐min , Liu Wei‐min 
Published: October 2004

AbstractA new series of diethoxyphosphinyl‐substituted imidazolium ‘room‐temperature ionic liquids’ (RTILs) were synthesized and characterized. The new compounds 1–12 (Table 1) were shown to have similar densities, but higher viscosities, than common ionic liquids. The new materials remain liquid over a broad temperature range, possess extremely low vapor pressures, display relatively high thermal stabilities (up to 325°), and decompose in a two‐step process. Analysis of the solid/liquid phase transition showed that all of the new RTILs possess low glass‐transition temperatures (Tg) associated with an intense change in molar heat capacity (ΔCpm).
Synthetic Studies Towards the Preparation of 2‐Benzyl‐2‐ hydroxybenzofuran‐3(2H)‐one, the Prototype of Naturally Occurring Hydrated Auronols
Authors: Löser Reik , Chlupacova Marta , Marecek Ales , Opletalova Veronika , Gütschow Michael 
Published: October 2004

AbstractVarious synthetic approaches were employed to prepare 2‐benzyl‐2‐hydroxybenzofuran‐3(2H)‐one (8), the prototype of naturally occurring auronols. While the base‐induced ring transformation of 3‐hydroxyflavanone (2) as well as the hydration of 2‐benzylidenebenzofuran‐3(2H)‐one (=aurone; 6) proved to be inappropriate, the hydrogenolytic epoxide‐ring opening of 2′‐phenylspiro[benzofuran‐2(3H),2′‐oxiran]‐3‐one (7), obtained from 6, represents an efficient method to afford the auronol 8.
Structure, Characterization, and Metal‐Complexation Properties of a New Tetraazamacrocycle Containing Two Phenolic Pendant Arms
Authors: Cui Xiuling , Calhorda Maria José , Costa Paulo J. , Delgado Rita , Drew Michael G. B. , Félix Vítor 
Published: October 2004

AbstractThe new tetraazamacrocycle 2 (=2,2′‐[[7‐Methyl‐3,7,11,17‐tetraazabicyclo[11.3.1]heptadeca‐1(17),13,15‐triene‐3,11‐diyl]bis(methylene)]bis(4‐bromophenol)) was synthesized and used as a ligand for different metal‐ion complexes. The X‐ray crystal structures of the complexes of the general formula [M(H‐2)]+NO$\rm{_{3}^{-}}$⋅MeOH (M=Ni2+, Zn2+), in which only one of the two pendant phenolic OH groups of 2 is deprotonated, were determined. In both complexes, the coordination environment is of the [5+1] type, the four N‐atoms of the macrocyclic framework defining a square‐planar arrangement around the metal center, with similar NiN and ZnN distances of 1.961(9) to 2.157(9) Å and 2.021(9) to 2.284(8) Å, respectively. In contrast, the MO distances are markedly different, 2.060(6) and 2.449(8) Å in the NiII complex, and 2.027(7) and 2.941(9) Å in the ZnII complex. The UV/VIS spectra of the NiII and CuII complexes with ligand 2, and the EPR spectra of the CuII system, suggest the same type of structure for the complexes in solution as in the solid state. Theoretical studies by means of density functional theory (DFT) confirmed the experimental structures of the NiII and ZnII complexes, and led to a proposal of a similar structure for the corresponding CuII complex. The calculated EPR parameters for the latter and comparison with related data support this interpretation. The singly occupied molecular orbital (SOMO) in these systems is mainly made of a d orbital of Cu, with a strong antibonding (σ*) contribution of the axially bound phenolate residue.
About a Practical Synthesis of Ambrox® from Sclareol: a New Preparation of a Ketone Key Intermediate and a Close Look at its Baeyer–Villiger Oxidation
Authors: Moulines Jean , Bats Jean‐Paul , Lamidey Anne‐Marie , Da Silva Nicole 
Published: October 2004

AbstractThe latest route to Ambrox® (1) starting from sclareol (2) proceeds through an oxy ketone 4 (Scheme 1). A new practical synthesis of the key intermediate 4 is described; it is equivalent to a partial oxidative degradation of sclareol (2) with peracetic and periodic acids (Scheme 2). The final product of the BaeyerVilliger oxidation of the oxy ketone 4 with commercial peracetic acid is decisively dependent on the reaction conditions because the expected acetate 9 reacts with any nucleophile, especially the peracid (Scheme 3). Furthermore, this acetate 9 is very prone to eliminative coupling (Scheme 4).
A New Approach to Nicotine: Symmetry Consideration for Synthesis Design
Authors: Ho Tse‐Lok , Kuzakov Eugene V. 
Published: October 2004

AbstractA synthesis of nicotyrine (9), and hence formally racemic nicotine, was carried out by elaboration of the 1 : 1 adduct 2 of cycloocta‐1,5‐diene and chlorosulfonyl isocyanate (ClSO2NCO). Transformation of adduct 2 into carbamate 4 was followed by ozonolysis, tosylation, and NaH treatment, which led to pyrrolidinylpiperidinone 6. LiAlH4 Reduction, debenzylation, and aromatization yielded 2.
Simulated impacts of climate change and land‐clearing on runoff from a small Sahelian catchment
Authors: Séguis L. , Cappelaere B. , Milési G. , Peugeot C. , Massuel S. , Favreau G. 
Published: October 2004

AbstractIn the Sahel, there are few long‐term data series available to estimate the climatic and anthropogenic impacts on runoff in small catchments. Since 1950, land clearing has enhanced runoff. The question is whether and by how much this anthropogenic effect offsets the current drought. To answer this question, a physically based distributed hydrological model was used to simulate runoff in a small Sahelian catchment in Niger, from the 1950–1998 rain‐series. The simulation was carried out for three soil surface states of the catchment (1950, 1975 and 1992). The catchment is characterized by an increase in cultivated land, with associated fallow, from 6% in 1950 to 56% in 1992, together with an increase in the extent of eroded land (from 7 to 16%), at the expense of the savanna. Effects of climate and land use are first analysed separately: irrespective of the land cover state, the simulated mean annual runoff decreases by about 40% from the wet period (1950–1969) to the dry period (1970–1998); calculated on the 1950–1998 rainfall‐series, the changes that occurred in land cover between 1950 and 1992 multiplies the mean annual runoff by a factor close to three. The analysis of a joint climatic and anthropogenic change shows that the transition from a wet period under a ‘natural’ land cover (1950) to a dry period under a cultivated land cover (1992) results in an increase in runoff of the order of 30 to 70%. At the scale of a small Sahelian catchment, the anthropogenic impact on runoff is probably more important than that of drought. This figure for relative increase in runoff contributions to ponds, preferential sites of seepage to groundwater, is less than that currently estimated for aquifer recharge, which has been causing a significant continuous water table rise over the same period. Copyright © 2004 John Wiley & Sons, Ltd.
Long‐term final void salinity prediction for a post‐mining landscape in the Hunter Valley, New South Wales, Australia
Authors: Hancock G. R. , Wright A. , De Silva H. 
Published: October 2004

AbstractOpencast mining alters surface and subsurface hydrology of a landscape both during and post‐mining. At mine closure, following opencast mining in mines with low overburden to coal ratios, a void is left in the final landform. This final void is the location of the active mine pit at closure. Voids are generally not infilled within the mines' lifetime, because of the prohibitive cost of earthwork operations, and they become post‐mining water bodies or pit lakes. Water quality is a significant issue for pit lakes. Groundwater within coal seams and associated rocks can be saline, depending on the nature of the strata and groundwater circulation patterns. This groundwater may be preferentially drawn to and collected in the final void. Surface runoff to the void will not only collect salts from rainfall and atmospheric fallout, but also from the ground surface and the weathering of fresh rock. As the void water level rises, its evaporative surface area increases, concentrating salts that are held in solution. This paper presents a study of the long term, water quality trends in a post‐mining final void in the Hunter Valley, New South Wales, Australia. This process is complex and occurs long term, and modelling offers the only method of evaluating water quality. Using available geochemical, climate and hydrogeological data as inputs into a mass‐balance model, water quality in the final void was found to increase rapidly in salinity through time (2452 to 8909 mg l−1 over 500 years) as evaporation concentrates the salt in the void and regional groundwater containing high loads of salt continues to flow into the void. Copyright © 2004 John Wiley & Sons, Ltd.
Hydrochemistry of groundwaters in a spa area of Korea: an implication for water quality degradation by intensive pumping
Authors: Kim Kangjoo , Koo Min‐Ho , Moon Sang‐Ho , Yum Byoung‐Woo , Lee Kwang‐Sik 
Published: October 2004

AbstractA geochemical study was carried out in a small spa area (Onyang Spa, Korea) where intensive pumping of deep thermal groundwater (1 300 000 m3 year−1) is taking place. This has caused the deep fractures to lose their artesian pressure and the upper shallow fractures have been encroached by shallow, cold waters. To quantify the influence of long‐term heavy pumping on the quality of the geothermal water, groundwater sampling and chemical analysis, water‐level measurement, and well loggings were performed for the selected deep thermal wells and shallow cold wells. Chemical analysis results indicate a big contrast in water chemistry and origins between the two water types. Shallow groundwater shows a wider concentration ranges in solutes that are closely related to human activity, illustrating the water's vulnerability to contamination near the land surface. Plots of water chemistry as a function of fluoride reveal that the quality of the thermal water was greatly influenced by the shallow, cold groundwater and that intensive pumping of the deep thermal groundwater has caused the introduction of shallow groundwater into the deeper fractures. Although the deep and the shallow fractures were piezometrically separated to some extent, a mixing model based on fluoride and nitrate indicated that the cold‐water fractions in the thermal wells are up to 50%. This suggests that the thermal water is faced with water quality degradation by the downward flow of the shallow, cold water. Restriction on the total of all the pumpage permits per unit area is suggested to restore the artesian pressure of the deep thermal aquifer and to prevent cold‐water intrusion in the study area. Copyright © 2004 John Wiley & Sons, Ltd.
Novel markers for poor prognosis in head and neck cancer
Authors: Chin David , Boyle Glen M. , Williams Rebecca M. , Ferguson Kaltin , Pandeya Nirmala , Pedley Julie , Campbell Catherine M. , Theile David R. , Parsons Peter G. , Coman William B. 
Published: October 2004

AbstractHead and neck cancer (HNSCC) is one of the most distressing human cancers, causing pain and affecting the basic survival functions of breathing and swallowing. Mortality rates have not changed despite recent advances in radiotherapy and surgical treatment. We have compared the expression of over 13,000 unique genes in 7 cases of matched HNSCC and normal oral mucosa. Of the 1,260 genes that showed statistically significant differences in expression between normal and tumor tissue at the mRNA level, the three top ranking of the top 5% were selected for further analysis by immunohistochemistry on paraffin sections, along with the tumor suppressor genes p16 and p53, in a total of 62 patients including 55 for whom >4‐year clinical data was available. Using univariate and multivariate survival analysis, we identified SPARC/osteonectin as a powerful independent prognostic marker for short disease‐free interval (DFI) (p < 0.002) and poor overall survival (OS) (p = 0.018) of HNSCC patients. In combination with other ECM proteins found in our analysis, PAI‐1 and uPA, the association with DFI and OS became even more significant (p < 0.001). Our study represents the first instance of SPARC as an independent prognostic marker in HNSCC.
Red meat consumption and risk of cancers of the proximal colon, distal colon and rectum: The Swedish Mammography Cohort
Authors: Larsson Susanna C. , Rafter Joseph , Holmberg Lars , Bergkvist Leif , Wolk Alicja 
Published: October 2004

AbstractAlthough there is considerable evidence that high consumption of red meat may increase the risk of colorectal cancer, data by subsite within the colon are sparse. The objective of our study was to prospectively examine whether the association of red meat consumption with cancer risk varies by subsite within the large bowel. We analyzed data from the Swedish Mammography Cohort of 61,433 women aged 40–75 years and free from diagnosed cancer at baseline in 1987–1990. Diet was assessed at baseline using a self‐administered food‐frequency questionnaire. Over a mean follow‐up of 13.9 years, we identified 234 proximal colon cancers, 155 distal colon cancers and 230 rectal cancers. We observed a significant positive association between red meat consumption and risk of distal colon cancer (p for trend = 0.001) but not of cancers of the proximal colon (p for trend = 0.95) or rectum (p for trend = 0.32). The multivariate rate ratio for women who consumed 94 or more g/day of red meat compared to those who consumed less than 50 g/day was 2.22 (95% confidence interval [CI] 1.34–3.68) for distal colon, 1.03 (95% CI 0.67–1.60) for proximal colon and 1.28 (95% CI 0.83–1.98) for rectum. Although there was no association between consumption of fish and risk of cancer at any subsite, poultry consumption was weakly inversely related to risk of total colorectal cancer (p for trend = 0.04). These findings suggest that high consumption of red meat may substantially increase the risk of distal colon cancer. Future investigations on red meat and colorectal cancer risk should consider cancer subsites separately. © 2004 Wiley‐Liss, Inc.
In vitro culture of rat neuromicrovascular endothelial cells on polymeric scaffolds
Authors: Conconi Maria Teresa , Lora Silvano , Baiguera Silvia , Boscolo Elisa , Folin Marcella , Scienza Renato , Rebuffat Piera , Parnigotto Pier Paolo , Nussdorfer Gastone Giovanni 
Published: October 2004

AbstractPolyphosphazenes are polymers possessing a skeleton composed of alternating phosphorous and nitrogen atoms, and two side‐moieties linked to each phosphorous atom. Polyphosphazenes with amino acid esters as side‐moieties are biocompatible and biodegradable polymers. Two polyphosphazenes, poly[bis(ethyl alanate) phosphazene] and poly[(ethyl phenylalanate)0.8(ethyl alanate)0.8(ethyl glycinate)0.4 phosphazene] (PPAGP) were synthesized, and processed to form small fibers. Their ability to support rat neuromicrovascular endothelial cell (EC) adhesion and growth has been studied, using poly(D,L‐lactic acid) as reference compound. Scanning electron microscopy revealed that both poly[bis(ethyl alanate) phosphazene] and PPAGP fibers were thinner than poly(D,L‐lactic acid) fibers, and possessed a more irregular and porous surface. All polymers increased EC adhesion, compared with polystyrene, but only polyphosphazenes were able to improve EC growth. The highest increase in EC proliferation was induced by PPAGP, which, as revealed by environmental scanning electron microscopy, was also able to induce ECs to arrange into tubular structures. The conclusion is drawn that PPAGP may provide the best scaffold for engineered blood vessels, because it promotes adhesion, growth, and organization of ECs into capillary‐like structures. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 669–674, 2004