bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamic Chemical Devices: Photoinduced Electron Transfer and Its Ion‐Triggered Switching in Nanomechanical Butterfly‐Type Bis(porphyrin)terpyridines
Authors: Linke‐Schaetzel Myriam , Anson Christopher E. , Powell Annie K. , Buth Gernot , Palomares Emilio , Durrant James D. , Balaban Teodor Silviu , Lehn Jean‐Marie 
Published: November 2005

AbstractA series of butterfly‐type molecular constructs has been prepared in good yield by using a double Stille coupling synthetic protocol. They are composed of a terpyridine (terpy) scaffold and two wings composed of appended porphyrins that are capable of switching from an extended W geometry to a compact U geometry upon cation coordination of the terpy unit. The porphyrin moieties exist in the constructs either as free bases or they can be sequentially metallated, thus giving rise to wings of different “colours”. Stationary and time‐resolved emission studies of the HZn, ZnAu and Zn2Au constructs show that the electronic properties are strongly dependent on the geometry. In the extended W conformation an energy‐transfer process is seen from the free base to the Zn‐metallated porphyrin. In the U conformation in Zn2Au the donor luminescence resulting from the singlet excited state of the Zn wing is strongly, quenched not only due to the heavy atom effect but also due to a fast electron‐transfer process to the ground state of the Au wing. Furthermore, the binding of (α,ω)‐diamine substrates to the ZnII–porphyrin sites can also influence the conformation of the system. For the Zn2Zn construct, single‐crystal diffraction experiments with synchrotron radiation allowed the structure to be solved by direct methods and fully refined; it shows the expected U conformation. The central Zn atom is six‐coordinate, whereby the zinc atom is coordinated by the η3‐terpy ligand as well by monodentate and semi‐chelating acetate anions. The structure is made rigid by hydrogen bonds involving the aqua ligands on the outer Zn centres and acetate oxygen atoms. The present system thus represents a double‐trigger‐modulated optomechanical switching device with selective substrate binding for either metal atoms or tailored ligands. Both energy‐ and electron‐transfer processes can be controlled opening a means of improving the on/off ratio in future constructs.
Origin of Stereoinduction by Chiral Aminophosphane Phosphinite Ligands in Enantioselective Catalysis: Asymmetric Hydroformylation
Authors: Carbó Jorge J. , Lledós Agustí , Vogt Dieter , Bo Carles 
Published: November 2005

AbstractThe origin of stereoinduction by chiral aminophosphane phosphinite (AMPP) ligands in asymmetric hydroformylation was investigated with a theoretical approach. The roles of the stereogenic center at the aminophosphane phosphorus atom (NP*) and of the chirality of the backbone were analyzed by considering three experimentally tested cases: 1) P‐stereogenic yielding highee, 2) P‐nonstereogenic yielding lowee, and 3) P‐stereogenic yielding lowee. We succeeded in reproducing the experimentally observed trends for the three studied AMPP ligands. Our results indicated that alkene insertion into the rhodium–hydride bond is the selectivity‐determining step, and not alkene coordination. Additional calculations on model systems revealed that the different nonbonding weak‐type interactions of styrene with the substituents of the NP* stereogenic center in an axial position is responsible for stereodifferentiation. The chirality of the AMPP backbone plays a secondary role. The rationalization of the stereochemical outcome is not straightforward, because two competitive equatorial/axial reaction paths, showing opposite asymmetric induction, must be considered. Construction of stereochemical models and evaluation of stereoinduction for novel ligand systems suggested that two prerequisites are required to improve the performance of AMPP‐type ligands in asymmetric hydroformylation: 1) combination of stereorecognition and stereohindrance by substituents at the NP* atom, and 2) more rigid backbones.
Silica Self‐Assembly and Synthesis of Microporous and Mesoporous Silicates
Authors: Rimer Jeffrey D. , Fedeyko Joseph M. , Vlachos Dionisios G. , Lobo Raul F. 
Published: November 2005

AbstractThe microstructure of silica in basic aqueous solutions containing organic cations and prepared from monomeric precursors is reviewed and interpreted within the context of classical ideas of self‐assembly of molecular aggregates. The solution properties can be understood by using the pseudo‐phase separation approach coupled to the acid–base chemistry of silanol groups and the Poisson–Boltzmann equation. The silica nanoparticles frequently observed in these systems have a core–shell structure with silica in the core and the organic cations at the shell. Individual particles are observed when the forces between particles are repulsive—as is the case for small cations such as tetramethylammonium or tetrapropylammonium—and extended structures such as M41S materials are formed when the forces are attractive—‐as is the case for surfactants such as cetyltrimethylammonium. These ideas are useful to understand the evolution of zeolite synthesis gels from nucleation to crystal growth. Although at room temperature the silica and the organic cations are segregated, upon heating the organic cations are embedded within the particles. This transformation signals the onset of structure direction whereby the size and geometry of the organic cation induce changes in the structure of silica that may lead to zeolite nuclei.
Controlling the Nature of Mixed (Phthalocyaninato)(porphyrinato) Rare‐Earth(III) Double‐Decker Complexes: The Effects of Nonperipheral Alkoxy Substitution of the Phthalocyanine Ligand
Authors: Wang Rongming , Li Renjie , Li Yong , Zhang Xianxi , Zhu Peihua , Lo Pui‐Chi , Ng Dennis K. P. , Pan Na , Ma Changqin , Kobayashi Nagao , Jiang Jianzhuang 
Published: November 2005

AbstractThe half‐sandwich rare‐earth complexes [MIII(acac)(TClPP)] (M=Sm, Eu, Y; TClPP=meso‐tetrakis(4‐chlorophenyl)porphyrinate; acac=acetylacetonate), generated in situ from [M(acac)3]⋅n H2O and H2(TClPP), were treated with 1,8,15,22‐tetrakis(3‐pentyloxy)phthalocyanine [H2{Pc(α‐OC5H11)4}] (Pc=phthalocyaninate) under reflux in n‐octanol to yield both the neutral nonprotonated and protonated (phthalocyaninato)(porphyrinato) rare‐earth double‐decker complexes, [MIII{Pc(α‐OC5H11)4}(TClPP)] (1–3) and [MIIIH{Pc(α‐OC5H11)4}(TClPP)] (4–6), respectively. In contrast, reaction of [YIII(acac)(TClPP)] with 1,4,8,11,15,18,22,25‐octakis(1‐butyloxy)phthalocyanine [H2Pc(α‐OC4H9)8] gave only the protonated double‐decker complex [YIIIH{Pc(α‐OC4H9)8}(TClPP)] (7). These observations clearly show the importance of the number and positions of substituents on the phthalocyanine ligand in controlling the nature of the (phthalocyaninato)(porphyrinato) rare‐earth double‐deckers obtained. In particular, α‐alkoxylation of the phthalocyanine ligand is found to stabilize the protonated form, a fact supported by molecular‐orbital calculations. A combination of mass spectrometry, NMR, UV‐visible, near‐IR, MCD, and IR spectroscopy, and X‐ray diffraction analyses, facilitated the differentiation of the newly prepared neutral nonprotonated and protonated double‐decker complexes. The crystal structure of the protonated form has been determined for the first time.
Unusual High‐Temperature Structural Behaviour in Ferroelectric Bi2WO6
Authors: McDowell Neil A. , Knight Kevin S. , Lightfoot Philip 
Published: November 2005

AbstractThe crystal structure of Aurivillius phase ferroelectric Bi2WO6 has been studied in detail as a function of temperature by using high‐resolution powder neutron diffraction. In agreement with an earlier study, a transition from space group P21ab to B2cb occurs at about 660 °C. This transition corresponds to the loss of one octahedral tilt mode within the perovskite‐like WO4 layer of the structure. A second, reconstructive, phase transition occurs around 960 °C, corresponding to the ferroelectric Curie point; in contrast to previous suggestions, the structure of this high‐temperature phase contains layers of stoichiometry WO4, with WO6 octahedra sharing edges and corners, and with the fluorite‐like Bi2O2 layers remaining essentially unchanged. This structure is closely related to that of the ambient temperature phase of lanthanide‐doped derivatives, for example, Bi0.7Yb1.3WO6 recently reported. This phase‐transition behaviour is in stark contrast to that of other members of the Aurivillius family, such as SrBi2Ta2O9 and Bi4Ti3O12, which retain the archetypal Aurivillius connectivity at all temperatures.
A Starburst‐Shaped Heterometallic Compound Incorporating Six Densely Packed Gd3+ Ions
Authors: Livramento João Bruno , Sour Angélique , Borel Alain , Merbach André E. , Tóth Éva 
Published: November 2005

AbstractThe heterotritopic ligand [bpy(DTTA)2]8− has two diethylenediamine‐tetraacetate units for selective lanthanide(III) coordination and one bipyridine function for selective FeII coordination. In aqueous solution and in the presence of these metals, the ligand is capable of self‐assembly to form a rigid supramolecular metallostar structure, {Fe[Gd2bpy(DTTA)2(H2O)4]3}4−. We report here the physicochemical characterization of the dinuclear complex [Gd2bpy(DTTA)2(H2O)4]2− and the metallostar {Fe[Gd2bpy(DTTA)2(H2O)4]3}4− with regard to potential MRI contrast agent applications. A combination of pH potentiometry and 1H NMR spectroscopy has been used to determine protonation constants for the ligand [bpy(DTTA)2]8− and for the complexes [Fe{bpy(DTTA)2}3]22− and [Y2bpy(DTTA)2]2−. In addition, stability constants have been measured for the dinuclear chelates [M2bpy(DTTA)2]n− formed with M = Gd3+ and Zn2+ (log KGdL = 18.2; log KZnL = 18.0; log KZnHL = 3.4). A multiple field, variable‐temperature 17O NMR and proton relaxivity study on [Gd2bpy(DTTA)2(H2O)4]2− and {Fe[Gd2bpy(DTTA)2(H2O)4]3}4− yielded the parameters for water exchange and the rotational dynamics. The 17O chemical shifts are indicative of bishydration of the lanthanide ion. The exchange rates of the two inner‐sphere water molecules are very similar in the dinuclear [Gd2bpy(DTTA)2(H2O)4]2− and in the metallostar (kex298 = 8.1±0.3×106 and 7.4±0.2×106 s−1, respectively), and are comparable to kex298 for similar GdIII poly(amino carboxylates). The rotational dynamics of the metallostar has been described by means of the Lipari–Szabo approach, which involves separating global and local motions. The difference between the local and global rotational correlation times, τlO298 = 190±15 ps and τgO298 = 930±50 ps, respectively, shows that the metallostar is not completely rigid. However, the relatively high value of S2 = 0.60±0.04, describing the restriction of the local motions with regard to the global one, points to a limited flexibility compared with previously reported macromolecules such as dendrimers. As a result of the two inner‐sphere water molecules, with their near‐optimal exchange rate, and the limited flexibility, the metallostar has a remarkable molar proton relaxivity, particularly at high magnetic fields (r1 = 33.2 and 16.4 mM−1 s−1 at 60 and 200 MHz, respectively, at 25 °C). It packs six efficiently relaxing GdIII ions into a small molecular space, which leads, to the best of our knowledge, to the highest relaxivity per molecular mass ever reported for a GdIII complex. The [bpy(DTTA)2]8− ligand is also a prime candidate as a terminal ligand for constructing larger sized, FeII (or RuII)‐based metallostars or metallodendrimers loaded with GdIII on the surface.
Mollusk Shell Formation: A Source of New Concepts for Understanding Biomineralization Processes
Authors: Addadi Lia , Joester Derk , Nudelman Fabio , Weiner Steve 
Published: November 2005

AbstractThe biological approach to forming crystals is proving to be most surprising. Mollusks build their shells by using a hydrophobic silk gel, very acidic aspartic acid rich proteins, and apparently also an amorphous precursor phase from which the crystals form. All this takes place in a highly structured chitinous framework. Here we present ideas on how these disparate components work together to produce the highly structured pearly nacreous layer of the mollusk shell.
A Family of Ferro‐ and Antiferromagnetically Coupled Decametallic Chromium(III) Wheels
Authors: Low David M. , Rajaraman Gopalan , Helliwell Madeleine , Timco Grigore , van Slageren Joris , Sessoli Roberta , Ochsenbein Stefan T. , Bircher Roland , Dobe Christopher , Waldmann Oliver , Güdel Hans‐Ulrich , Adams Mark A. , Ruiz Eliseo , Alvarez Santiago , McInnes Eric J. L. 
Published: November 2005

AbstractThe synthesis and crystal structures of a family of decametallic CrIII “molecular wheels” are reported, namely [Cr10(OR)20(O2CR′)10] [R′=Me, R=Me (1), Et (2); R′=Et, R=Me (3), Et (4); R′=CMe3, R=Me (5), Et (6)]. Magnetic studies on 1–6 reveal a remarkable dependence of the magnetic behaviour on the nature of R. In each pair of complexes with a common carboxylate (R′) the nearest neighbour Cr⋅⋅⋅Cr magnetic exchange coupling is more antiferromagnetic for the ethoxide‐bridged (R=Et) cluster than for the methoxide analogue. In complexes 2, 4 and 6 the overall coupling is weakly antiferromagnetic resulting in diamagnetic (S=0) ground states for the cluster, whilst in 1 and 5 it is weakly ferromagnetic thus resulting in very high‐spin ground states. This ground state has been probed directly in the perdeuterated version of 1 ([D]1) by inelastic neutron scattering experiments, and these support the S=15 ground state expected for ferromagnetic coupling of ten CrIII ions, and they also indicate that a single J‐value model is inadequate. The ground state of 5 is large but not well defined. The trends in J on changing R are further supported by density functional calculations on 1–6, which are in excellent agreement with experiment. The very large changes in the nature of the ground state between 1 and 2, and 5 and 6 are the result of relatively small changes in J that happen to cross J=0, hence changing the sign of J.
A New Entry to Doubly N‐Confused [26]Hexaphyrins(1.1.1.1.1.1) from Normal [26]Hexaphyrins(1.1.1.1.1.1) through an Unprecedented Double Pyrrolic Rearrangement
Authors: Suzuki Masaaki , Yoon Min‐Chul , Kim Deok Yun , Kwon Jung Ho , Furuta Hiroyuki , Kim Dongho , Osuka Atsuhiro 
Published: November 2005

AbstractTreatment of hexakis(pentafluorophenyl)‐substituted [26]hexaphyrin(1.1.1.1.1.1) (1) with CuCl in the presence of pyridine and molecular oxygen led to formation of doubly N‐confused [26]hexaphyrin(1.1.1.1.1.1) 2 in a moderate yield through an unprecedented double pyrrolic rearrangement. Macrocycle 2 has been shown to serve as an effective bis‐metal‐coordinating ligand and exhibits attractive optical properties such as a sharp Soret‐like band at 566 nm and low‐energy fluorescence at 1058 nm.
Treatment of local breast carcinoma in Florida
Authors: Voti Lydia , Richardson Lisa C. , Reis Isildinha M. , Fleming Lora E. , MacKinnon Jill , Coebergh Jan Willem W. 
Published: November 2005

AbstractBACKGROUNDBreast‐conserving surgery combined with radiation (BCSR) is the recommended alternative treatment to mastectomy for local breast carcinoma. However, limited access to healthcare may result in more extensive surgical treatment. The effect of distance to radiation therapy facilities on the likelihood of receiving BCSR was examined in Florida.METHODSLocal breast carcinomas reported to Florida's statewide registry between July, 1997, and December, 2000 were linked to the Agency of Healthcare Administration inpatient and outpatient databases to supplement the registry's treatment data, resulting in 18,903 local breast carcinoma cases treated with BCSR or mastectomy. The odds of receiving BCSR were modeled as a function of distance to the closest radiation therapy facility, adjusting for health insurance, age, race/ethnicity, and marital status.RESULTSDistance to the closest radiation therapy facility was negatively associated with BCSR, with the odds ratio (OR) decreasing by 3% per 5‐mile increase in distance. Compared with the uninsured, privately insured women were 49% more likely to receive BCSR (OR of 1.49; 95% confidence interval [95% CI], 1.20–1.86) and Medicare patients were 37% more likely (OR of 1.37; 95% CI, 1.09–1.72). Age at diagnosis was negatively associated, reducing the odds of BCSR by 1% per year increase in age. Compared with white non‐Hispanic, Hispanic women were 38% less likely to receive BCSR (OR of 0.62; 95% CI, 0.55–0.71). Married women were 23% more likely to receive BCSR compared with singles (OR of 1.23; 95% CI, 1.09–1.40); women who were separated, divorced, or widowed did not differ significantly from single women.CONCLUSIONSDistance to radiation therapy facilities may negatively impact the likelihood of BCSR in Florida. Age at diagnosis, insurance type, race/ethnicity, and marital status were associated with BCSR. Future efforts should target the uninsured, Hispanics, the elderly, and the unmarried women to reduce disparities in the administration of BCSR for local breast carcinoma. Cancer 2006. © 2005 American Cancer Society.
The impact of fluor‐18‐deoxyglucose‐positron emission tomography in the management of colorectal liver metastases
Authors: Wiering Bastiaan , Krabbe Paul F. M. , Jager Gerrit J. , Oyen Wim J. G. , Ruers Theo J. M. 
Published: November 2005

AbstractFluor‐18‐deoxyglucose‐positron emission tomography (FDG‐PET) has emerged as a promising diagnostic modality in recurrent colorectal carcinoma. Whole‐body FDG‐PET may be an accurate diagnostic modality to determine whether patients with recurrent hepatic disease are suitable candidates for curative resection. Reports on the use of FDG‐PET in patients with recurrent colorectal carcinoma are scarce, especially those on colorectal liver metastases. To assess the usefulness of this emerging modality for the selection of patients to undergo resection for colorectal liver metastases, a systematic (meta)‐analysis of the current literature was conducted. In the absence of randomized controlled clinical trials, a traditional meta‐analysis could not be performed. An alternative strategy was designed to evaluate the current literature. After a literature search, an index score was devised to evaluate the articles with regard to the impact of FDG‐PET in patients with colorectal liver metastases. The index scored articles on several items and, as such, could be considered an objective approach for the assessment of diagnostic, nonrandomized clinical trials. The proposed index proved to be an independent instrument for judging several research questions and was used systematically to address the sensitivity, specificity, and clinical impact of FDG‐PET in patients with colorectal liver metastases. For FDG‐PET, the pooled sensitivity and specificity results were 88.0% and 96.1%, respectively, for hepatic disease and 91.5% and 95.4%, respectively, for extrahepatic disease. For the 6 articles that reported the highest scores on the index, the sensitivity and specificity of FDG‐PET for hepatic metastatic disease were 79.9% and 92.3%, respectively, and 91.2% and 98.4%, respectively, for extrahepatic disease, respectively. For computed tomography, the pooled sensitivity and specificity results were 82.7% and 84.1%, respectively, for hepatic lesions and 60.9% and 91.1%, respectively, for extrahepatic lesions. The percentage change in clinical management due to FDG‐PET was 31.6% (range, 20.0–58.0%) in the articles that scored above the mean and reported this item. For the 6 highest scoring studies, the percentage change in clinical management was 25.0% (range, 20.0–32.0%). Despite apparent omissions in the literature, the combined sensitivity and specificity of FDG‐PET clearly indicated that FDG‐PET has added value in the diagnostic workup of patients with colorectal liver metastases. FDG‐PET can be considered a useful tool in preoperative staging and produced superior results compared with conventional diagnostic modalities, especially for excluding or detecting extrahepatic disease. Cancer 2005. © 2005 American Cancer Society.
The predictive value of apoptosis protease‐activating factor 1 in rectal tumors treated with preoperative, high‐dose‐rate brachytherapy
Authors: Zlobec Inti , Vuong Te , Compton Carolyn C. 
Published: November 2005

AbstractBACKGROUNDThe objective of this study was to assess the value of apoptosis protease‐activating factor 1 (APAF‐1) as a predictive marker of response in rectal tumors treated with preoperative, high‐dose‐rate endorectal brachytherapy.METHODSImmunohistochemistry for APAF‐1 was performed on 94 rectal tumor biopsy specimens from patients who were treated on a preoperative, high‐dose‐rate brachytherapy protocol. Tumors were considered positive when > 10% of tumor cells were immunoreactive. The association between APAF‐1 expression and tumor response was made using the chi‐square test.RESULTSForty‐four tumors (43%) were positive for APAF‐1. Thirty tumors had complete pathologic tumor regression after preoperative radiotherapy. Of these, 18 tumors were positive for APAF‐1. A partial response occurred in 35 tumors. Eighteen tumors (51%) were positive for the protein. Only 8 of 29 nonresponsive tumors (28%) were immunoreactive for APAF‐1. A significant association was found between complete tumor regression and positive APAF‐1 status (P = 0.018). APAF‐1 expression in partially responsive tumors was significantly greater than in nonresponsive tumors (P = 0.03).CONCLUSIONSAPAF‐1 expression in pretreatment rectal tumor biopsy specimens may be useful as a predictive marker of response to preoperative radiotherapy in patients with rectal carcinoma. Cancer 2006. © 2005 American Cancer Society.
From Molecular Double‐Ladders to an Unprecedented Polycatenation: A Parallel Catenated 3D Network Containing Bicapped Keggin Polyoxometalate Clusters
Authors: Shi Zhenyu , Gu Xiaojun , Peng Jun , Yu Xia , Wang Enbo 
Published: November 2005

AbstractA new three‐dimensional coordination polymer, {Cu3(4,4′‐bpy)3(H2O)[PMo12O40(VO)2]·5H2O}n (1) (4,4′‐bpy = 4,4′‐bipyridine), which represents the first example of 3D polycatenation generated by unprecedented parallel catenation of the 1D double ladders, has been hydrothermally synthesized. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Self‐Assembly and Characterization of Homo‐ and Heterodinuclear Complexes of Zinc(II) and Lanthanide(III) Ions with a Tridentate Schiff‐Base Ligand
Authors: Patroniak Violetta , Stefankiewicz Artur R. , Lehn Jean‐Marie , Kubicki Maciej , Hoffmann Marcin 
Published: November 2005

AbstractTridentate Schiff‐base ligand HL (L = C12H9N2O) reacts with lanthanide(III) nitrates to give complexes of formulae [M2L3(NO3)3], where M = Y3+ (1), La3+ (2), Nd3+ (3), Sm3+ (4), Eu3+ (5), Gd3+ (6), Tb3+ (7), Dy3+ (8), Ho3+ (9), Lu3+ (10), and [MM1L3(NO3)x], where M = Eu3+, and M1 = Dy3+ (11), Zn2+ (12); x = 3 for 11 and 2 for 12. The structures of the complexes have been assigned on the basis of the spectroscopic data (solution analysis) and microanalyses. In the case of complexes 3, 5, 8 and 12 the structures have been confirmed by X‐ray crystallography. The structural analysis of the dinuclear complexes showed the presence of two metal atoms [M(1) and M(2)] and three ligands, L. Each lanthanide atom is coordinated to by 9 donor atoms with typical Ln–N and Ln–O distances. Zinc(II) is coordinated to by two oxygen atoms and four nitrogen atoms from two ligands. The metal ions are bridged by the phenoxo oxygen atoms of the ligands. We have obtained a heterodinuclear complex by a rapid one‐step reaction. Quantum mechanical calculations indicated that the formation of heterodinuclear complex 12 is slightly favored energetically over the homodinuclear complex 5. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)