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Showing papers by "University of Duisburg-Essen published in 1989"



Journal ArticleDOI

116 citations


Journal ArticleDOI
TL;DR: Direct comparison of lymphocyte and cardiac beta-adrenoceptor densities revealed that changes in lymphocyte beta 2- adrenoceptors are significantly correlated with changes in cardiac beta 1-and-a-half, but not related to changes in heart failure patients with chronic heart failure.
Abstract: In heart failure a decrease in cardiac beta-adrenoceptors presumably due to endogenous down-regulation by the elevated catecholamines is a general phenomenon Thus, attempts have been made to assess beta-adrenoceptor function in patients with chronic heart failure in order to monitor the functional state of cardiac beta-adrenoceptors The model most widely used is that of circulating lymphocytes that contain a homogeneous population of beta 2-adrenoceptors coupled to the adenylate cyclase/cyclic AMP system The biochemical and pharmacological properties of beta 2-adrenoceptors present in lymphocytes are quite comparable to those of beta 2-adrenoceptors in the human heart, but clearly different from those of human cardiac beta 1-adrenoceptors Furthermore, beta-adrenoceptor agonists and antagonists regulate lymphocyte beta 2- and cardiac beta 1- and beta 2-adrenoceptors in a subtype-selective fashion: while non-selective agonists (independent of exogenously applied or endogenously elevated) and antagonists affect both cardiac beta 1- and beta 2- as well as lymphocyte beta 2-adrenoceptors, beta 1-selective agonists and antagonists influence only cardiac beta 1-, but not cardiac and lymphocyte beta 2-adrenoceptors Finally, direct comparison of lymphocyte and cardiac beta-adrenoceptor densities revealed that changes in lymphocyte beta 2-adrenoceptors are significantly correlated with changes in cardiac beta 2-adrenoceptors, but not related to changes in cardiac beta 1-adrenoceptors Since beta 1-adrenoceptors predominate in all parts of the human heart, the use of lymphocyte beta 2-adrenoceptors as a tool for predicting the status of cardiac beta-adrenoceptors is, therefore, quite limited

73 citations


Journal ArticleDOI
TL;DR: In this paper, the central charge is shown to be a discontinuous function of the distances of the defects, while the critical exponents (generalized corner exponents) depend continuously on the positions of the defect.

50 citations



Journal ArticleDOI
TL;DR: The cyclohexadiene iron complex I (R = H) prepd. from tricarbonyl(h5-cyclohexadienylium)iron tetrafluoroborate and 2,3,4-Me2(MeO)C6H2NH2, underwent oxidative cyclization with highly active MnO2 to give 4-deoxycarbazomycin B (II R = H), was detd. by x-ray anal as mentioned in this paper.
Abstract: The cyclohexadiene iron complex I (R = H) prepd. from tricarbonyl(h5-cyclohexadienylium)iron tetrafluoroborate and 2,3,4-Me2(MeO)C6H2NH2, underwent oxidative cyclization with highly active MnO2 to give 4-deoxycarbazomycin B (II R = H). The structure of the carbazole complex III, obtained from I (R = H) and FeCl3, was detd. by x-ray anal. A total synthesis of carbazomycin (II, R = MeO) was achieved starting from 2,3-Me2C6H3OH via complex I (R = MeO).

33 citations




Journal ArticleDOI
TL;DR: The bis-diorganoboryl chalcogenides (R2B)2O [R = C2H5 (3); R2B2S [R2 = 1,5-C8H14 (5)], and (R 2B2Se] as discussed by the authors react with pyrazole and its derivatives 3-methylpyrazole (3-MePz) and indazole (benzo-Pz), to form in high yields (65-92%) stable 1:1 adducts.
Abstract: The bis(diorganoboryl) chalcogenides (R2B)2O [R = C2H5 (3); R2 = 1,5-C8H14 (1)], (R2B)2S [R2 = 1,5-C8H14 (5)], and (R2B)2Se [R2 = 1,5-C8H14 (7)] react with pyrazole (Pz) and its derivatives 3-methylpyrazole (3-MePz) and indazole (benzo-Pz) to form in high yields (65–92%) stable 1:1 adducts [e.g. 2 (El = O), 4 (El = O), 6 (El = S) and 8 (El = Se)]. 1H-, 13C-, 11B-NMR spectra and X-ray analyses (of 2 and 6) show a basic structure with a central B2ElN2 (El = O, S, Se) heterocycle. The reaction of 2 with R2BH and the thermolysis of 4 give the dimeric 1-pyrazolylboranes 9a and 9b, respectively. Neuartige Substituierte B2ElVIN2 Heterocyclen Die Bis(diorganoboryl)chalkogenide (R2B)2O [R = C2H5 (3); R2 = 1,5-C8H14 (1)], (R2B)2S [R2 = 1,5-C8H14 (5)], und (R2B)2Se [R2 = 1,5-C8H14 (7)] reagieren mit Pyrazol (Pz) und dessen Derivaten 3-Methylpyrazol (3-MePz) und Indazol (benzo-Pz) in hohen Ausbeuten (65–92%) zu stabilen 1:1-Additionsverbindungen [z. B. 2 (El = O), 4 (El = O), 6 (El = S), 8 (El = Se)]. 1H-, 13C-, 11B-NMR-Spektren und Rontgenstrukturanalysen (von 2 und 6) zeigen eine Grundstruktur mit einem zentralen B2ElN2-Heterocyclus (El = O, S, Se). Die Reaktion von 2 mit R2BH und die Thermolyse von 4 fuhren zu den dimeren 1-Pyrazolylboranen 9a bzw. 9b.

21 citations


Journal ArticleDOI
TL;DR: In this article, the structure and properties of the title compd. (I) were compared to those of cyclopropabenzene and cyclobutabenzenes.
Abstract: The structure and properties of the title compd. (I) were compared to those of cyclopropabenzene and cyclobutabenzene. I reacted with (Me3P)2Ni[COD] to give Ni complex II.

21 citations


Journal ArticleDOI
TL;DR: In this paper, the structure of the two adducts P-1 and Q-1 of bis(1,5-cyclooctanediyl)diboroxane (1) with pyridine (P) and quinuclidine (Q), which show solid-solid phase transformations at about 127 and 88°C, respectively, have been determined by X-ray diffraction at −145 and −163°C.
Abstract: The structures of the two adducts P-1 and Q-1 of bis(1,5-cyclooctanediyl)diboroxane (1) with pyridine (P) and quinuclidine (Q), which show solid-„solid” phase transformations at about 127 and 88°C, respectively, have been determined by X-ray diffraction at −145 and −163°C, respectively. The structure of Q-1 has also been determined at room temperature and at +50°C. Both P-1 and Q-1 are packed in head-to-tail pairs and show extensive isothermal as well as temperature-dependent dynamics in the crystalline phase. The onset of transformations into the new „fluctional solid” phase is discussed in terms of these lattice packings and the observed translational and vibrational dynamics. Rontgenstrukturanalyse und molekulare Dynamik von Festkorper-Phasenumwandlungen der N-Base-Addukte des Bis(1,5-cyclooctandiyl)diboroxans Von zwei Lewis-Base-Addukten des Bis(1,5-cyclooctandiyl)diboroxans (1) (mit Pyridin: P-1; Quinuclidin: Q-1) mit Fest-„Fest”-Phasenumwandlungen bei 127 bzw. 88°C wurden Rontgenstrahlbeugungs-Strukturen bei −145 bzw. −163°C ermittelt. Von Q-1 wurde zusatzlich die Struktur bei Raumtemperatur und bei +50°C bestimmt. P-1 und Q-1 sind im Gitter als Paare geordnet und zeigen umfangreiche isotherme und temperaturabhangige Dynamik in kristalliner Phase. Der Ubergang in die neue, „fluktuierende Festkorper”-Phase wird unter Einbeziehung der Gitteranordnung, der beobachteten Intragitter-Translative und der vibrativen Bewegungsvorgange diskutiert.

Journal ArticleDOI
TL;DR: In this article, the transition metal transition metal fragments are characterized by X-ray structure analyses. But they do not have the ability to be used in the analysis of cycloenantiomeric (Ligand) transitions.
Abstract: Sechs π-Komplexe der Heterocyclen [4a: R1R2R3 CH3; 5a: R1 C6H5, R2R3 CH3; 7d: R1 H, R2 C6H5, R3 CH3; 3a: R1 = yl, R2R3 CH3; 4b: R1R2 CH3, R3 C(CH3)CH2] mit den (Ligand)Ubergangsmetall-Fragmenten (OC)3Cr, C5H5Co, C2H4(Cl)Ir, C2H4Rh und Ni werden durch Kristallstrukturanalysen charakterisiert: (OC)3Cr-η6-5a (2 Rotamere) sowie die η4-cycloRS-Enantiomeren cycloS-C5H5Co-η4-5a-η6-Cr(CO)3; cycloS-C5H5Co-η4-7d; cycloR-C2H4(Cl)Ir-η4-4a, meso-(C2H4Rh-η1η4-3a)2 und meso-(Ni-η3η4-4bb′)2. Cycloenantiomeric (Ligand)Transition Metal π-Complexes of Organosubstituted 2,5-Dihydro-1,2,5-azasilaborole Compounds - Characterization in the Solid State Six π-complexes of the heterocycles [4a: R1R2R3 CH3; 5a: R1 C6H5, R2R3 CH3; 7d: R1 H, R2 C6H5, R3 CH3; 3a: R1 = yl, R2R3 CH3; 4b: R1R2 CH3, R3 C(CH3)CH2] with the (ligand)transition metal fragments (OC)3Cr, C5H5Co, C2H4(Cl)Ir, C2H4Rh and Ni are characterized by X-ray structure analyses: (OC)3Cr-η6-5a (2 rotamers) and the η4-cycloRS-enantiomers cycloS-C5H5Co-η4-5a-η6-Cr(CO)3; cycloS-C5H5Co-η4-7d; cycloR-C2H4(Cl)Ir-η4-4a, meso-(C2H4Rh-η1η4-3a)2 und meso-(Ni-η3η4-4bb′)2.

Journal ArticleDOI
TL;DR: The reactions of the bis(diorganoboryl) chalcogenides (R2B) with 3-methyl-, 3,5-dimethyl-, 3methyl-5-phenyl-, 3 methyl-4-dimethyltethenyl, 3 methyl5-diphenyl-, and 3, 5-di-tert-butylpyrazole have been investigated in this article.
Abstract: The reactions of the bis(diorganoboryl) chalcogenides (R2B)2ElVI [R = Et, ElVI = O (9); R2 = 1,5-C8H14 (1, ElVI = O), (2, ElVI = S)] with 3-methyl-, 3,5-dimethyl-, 3-methyl-5-phenyl-, 3,5-diphenyl-, and 3,5-di-tert-butylpyrazole [mPz, m2Pz, mpPz, p2Pz, and (tb)2Pz, respectively] have been investigated. mPz reacts with 2 to form the heterocycle m5, which due to the interaction of the methyl substituent with the carbon skeleton of 2 is unstable and readily rearranges to the novel heterocycle 7 (X-ray analysis) when dissolved in toluene at room temperature. In contrast the analogues m4 (El = O), formed from mPz and 1, is stable even when heated at 100°C. The reaction of 1 with m2Pz and mpPz does not produce stable heterocycles of the type 4, instead the 1:1 adducts m2Pz-1 and mpPz-1 are formed in which the pyrazole fluctuates between the two boron atoms of 1. The diboryl oxide 1 showed only weak interactions with mpPz and none with p2Pz and (tb)2Pz. With 9 the pyrazoles m2Pz, mpPz, and p2Pz from readily the corresponding heterocycles 10, however no reaction was observed with (tb)2Pz (1H-, 11B-, 13C-NMR). Strukturelle Voraussetzungen fur die Bildung der B2ElVIN2-Funfringe Die Reaktionen der Bis(diorganoboryl)chalkogenide (R2B)2ElVI [R = Et, ElVI = O (9); R2 = 1,5-C8H14 (1, ElVI = O), (2, ElVI = S)] mit 3-Methyl-, 3,5-Dimethyl-, 3-Methyl-5-phenyl-, 3,5-Diphenyl-, und 3,5-Di-tert-butylpyrazole [mPz, m2Pz, mpPz, p2Pz, und (tb)2Pz] werden untersucht. mPz reagiert mit 2 zu m5, das durch sterische Wechselwirkungen der Methyl-Gruppen von mPz mit dem C-Gerust von 2 destabilisiert ist und sich in Toluol leicht in den neuen Heterocyclus 7 (Rontgenstrukturanalyse) umwandelt. m4 (El = O) (aus mPz und 1) ist demgegenuber bis 100°C stabil. 1 bildet mit m2Pz und mpPz keine Heterocyclen des Typs 4, sondern die 1:1-Additionsverbindungen m2Pz-1 und mpPz-1 mit zwischen den zwei Bor-Atomen von 1 fluktuierenden Pz-Basen. Zwischen 1 und mpPz lassen sich nur schwache, zwischen 1 und p2Pz bzw. (tb)2Pz keine Wechselwirkungen nachweisen. 9 reagiert mit m2Pz, mpPz und p2Pz zu den Heterocyclen des Typs 10. Zwischen (tb)2Pz und 9 werden keine Wechselwirkungen beobachtet (1H-, 11B-, 13C-NMR).

Journal ArticleDOI
TL;DR: In this paper, the 13C-NMR and FT-IR spectra of dicyanoacetic acid esters were measured in various solvents, and the X-ray analysis of the sodium salt of p-nitrophenyl dichyanoacetate established the partial double bond character of the C1C2 bond which is the reason for the hindered rotation in salts and enols as proven by NMR spectroscopy.
Abstract: 13C-NMR- und FT-IR-Spektren von Dicyanesessigsaureestern in verschiedenen Losungsmitteln zeigen, das aprotische Losungsmittel (Chloroform, Acetonitril) die Ester-Form 1, basische bzw. protische Losungsmittel (DMSO, Methanol, Wasser) die Ketenhalbacetal-Form 2 begunstigen. Die 13C-chemischen Verschiebungen von Dicyanessigsaureestern und den davon abgeleiteten Natrium- und Kalium-Salzen sind in DMSO und Wasser praktisch identisch und lassen auf eine weitgehende Dissoziation der Ketenhalbacetale schliesen. Eine Rontgenstrukturanalyse des p-Nitrophenylester-Natrium-Salzes bestatigt den partiellen Doppelbindungscharakter der C1C2-Bindung, welcher der NMR-spektroskopisch nachweisbaren Rotationsbehinderung in den (dissoziierten) Enolen und Salzen zugrunde liegt. On the Structure of Dicyanoacetates The 13C-NMR and FT-IR spectra of dicyanoacetic acid esters were measured in various solvents. Aprotic solvents (acetonitrile, chloroform) favour structure 1, whereas solvents with good hydrogen-bond-accepting ability (DMSO, water, methanol) favour the formation and dissociation of enols, as shown by comparison of the 13C-chemical shifts of the enols with those of the corresponding sodium or potassium salts. The X-ray analysis of the sodium salt of p-nitrophenyl dicyanoacetate establishes the partial double bond character of the C1C2 bond which is the reason for the hindered rotation in salts and enols as proven by NMR spectroscopy.

Journal ArticleDOI
TL;DR: In this article, a σ/π rearrangement of cycloadditions of Carbonyl-Activated Alkynes to (η5C5Me5(CO)2RuPPAryl (P = p-Aryl) with methyl 2-butynoate yielded the five-membered metallaheterocycle (3a) with an (E)-configurated exocyclic P P bond.
Abstract: Die Umsetzung von (η5-C5Me5)(CO)2RuPPAryl (1) (Aryl = 2,4,6-tBu3C6H2). mit 2-Butinsaure-methylester (2a) liefert den funfgliedrigen Metallaheterocyclus (3a) mit einer exocyclischen P P-Bindung in der (E)-Konfiguration. Demgegenuber erfahrt das aus 1 und MeO2CCCCO2Me (2c) primar gebildete Cycloaddukt (3c) eine rasche σ/π-Umlagerung zu 5c, in dem eine (η2-PP)Ru-Einheit vorliegt. Die Strukturaufklarung von 5c erfolgte mittels Einkristall-Rontgenbeugung. Transition-Metal-Substituted Diphosphenes, XVII. — Dipolar [3+2] Cycloadditions of Carbonyl-Activated Alkynes to (η5C5Me5(CO)2Ru-P = p-Aryl (Aryl = 2,4,6-tBu3C6H2). First Examples of σ/π-Rearrangements of Diphosphene Ligands The reaction of (η5-C5Me5)(CO)2RuPPAryl (1) (Aryl = 2,4,6-tBu3C6H2) with methyl 2-butynoate (2a) yielded the five-membered metallaheterocycle (3a) with an (E)-configurated exocyclic P P bond. On the other hand the similarly formed cycloadduct (3c), obtained from 1 and MeO2CCCCO2Me (2c) at − 78°C, rapidly underwent a σ/π rearrangement to the complex 5c featuring a η2-coordinated PP unit. The molecular structure of 5c was established by single crystal X-ray diffraction analysis.

Journal ArticleDOI
TL;DR: The stereo selective influence of the Ab ring on substitution reactions at the iron is confirmed by the reaction of racemic 3 with P(C6H5)3 as mentioned in this paper, in which a ratio of the diastereomers of 1/2 is observed.

Journal ArticleDOI
TL;DR: This case report proves that even air rifle shots, which in general are considered to be harmless, may result in life-threatening injuries.
Abstract: Gunshot injuries of the heart are extremely rare thoracic traumas in Europe during peacetime. Concomitant lesions of the coronary arteries occur in less than 5%. This case reports on a 26-year-old man who was shot with an air rifle at short range. On admission the patient showed signs of pericardial tamponade. Emergency thoracotomy was performed and a frontal cardiac lesion was found in the distal third of the anterior descending branch of the left coronary artery. The bullet crossed the cavum of the left ventricle and remained in the posterior wall in the subepicardial layer adjacent to the posterior descending coronary branch. Under the conditions of extracorporeal circulation we removed the bullet, repaired both ventricle walls using patches in sandwich technique, and bypassed the coronary lesion by single aortocoronary venous graft. No signs of myocardial infarction could be detected by ECG. The follow-up after 3 years shows no cardiac problems and normal stress tolerance. This case report proves that even air rifle shots, which in general are considered to be harmless, may result in life-threatening injuries. For the severity of the injury are decisive the kinetic energy at the muzzle as well as configuration and type of the bullet.

Journal ArticleDOI
TL;DR: The results of the present study suggest that in the rat heart extracellular calcium plays a major role in the maintenance of the coronary vascular tone.
Abstract: In order to get more insight into the utilization of calcium in the mammalian heart and the influence of calcium antagonists on this process we have evaluated the negative inotropic and vasodilator effect of nifedipine, diltiazem, verapamil, bepridil and lidoflazine as well as of the intracellularly acting calcium antagonists ryanodine and TMB-8 in the presence of 0.9 and 1.8 mmol/l calcium in rat Langendorff hearts. The effect of ryanodine was also studied in guinea-pig Langendorff hearts. In addition, in rat and guinea-pig papillary muscles the effect of these drugs on the force of contraction was examined.

Journal ArticleDOI
TL;DR: CABOPP/VIM appears to be an effective and well tolerated program for the treatment of aggressive lymphomas and is predicted to have continued CR at 2 years.
Abstract: In 42 patients with high-grade malignant non-Hodgkin lymphomas, a new treatment program was used in an attempt to improve results without increasing toxicity. Two effective but relatively well tolerated and non-cross resistant drug combinations were given sequentially according to the response of disease. Therapy was started with a combination consisting of cyclophosphamide, doxorubicin, bleomycin, vincristine, procarbazine and prednisone (CABOPP). in patients with complete remission after a maximum of 4 cycles of CABOPP, this regimen was continued for a total of 6 cycles. in patients with progressive disease or with only a partial remission after 4 cycles of CABOPP, therapy was switched to a combination consisting of etoposide, ifosfamide and methotrexate (VIM). Complete remission (CR) was achieved in 86% of patients. Sixty-nine percent achieved CR with CABOPP alone and 17% after changing to VIM. the CR rate was 100% in patients with stage I or II and 78 % in those with stage III or IV of disease. the pr...

Journal ArticleDOI
TL;DR: In this paper, the gap emission observed in ultraviolet photoelectron spectra of metals takes place via a wavevector conserving excitation in the surface region localized on bulk Brillouin zone boundaries.
Abstract: It is shown that the gap emission observed in ultraviolet photoelectron spectra of metals takes place via a wavevector conserving excitation in the surface region localized on bulk Brillouin zone boundaries. Thus gap emission correspond to direct transitions between bulk initial statesEi(k⊥=kBZ,k‖) and evanescent statesEf(k⊥=kBZ,k‖) which are made possible by the existence of the surface. This fact can be used to map occupied bulk energy band dispersions. Examples for Silver, Copper, Gold and Platinum are given.


Journal ArticleDOI
TL;DR: In this paper, the static-kinematic optimality criteria are introduced for plastically designed structures having segments of prescribed length such that the variation of the cross sectional area is (1) Segmentwise linear; and (2) continuous across segment boundaries.
Abstract: Static-kinematic optimality criteria are introduced for plastically designed structures having segments of prescribed length such that the variation of the cross sectional area is (1) Segmentwise linear; and (2) continuous across segment boundaries. It is shown that, compared to other geometrical constraints suggested in the past, these constraints have the following advantages: (1) Stress concentrations due to cross-sectional discontinuities are avoided; (2) unlike some unconstrained optimal solutions, the underlying assumptions of simple structural theories are not violated; and (3) a high degree of design flexibility, an easier fabrication (due to linear segments), and a greater material economy are achieved. The optimality criteria, which turn out to be similar to those of Foulkes, are derived in a general form and then they are applied to a clamped beam with four segments. This theory is being extended to (1) Elastic design; and (2) other types of structures (e.g., plates).

Journal ArticleDOI
TL;DR: In this article, the metal-functionalized 1,3-diphospha-2-propanone Fe2(CO)6-[(iPr)2N-PC(O)P-N(iP)2] was used to give the carbonyl-stabilisierte phosphorus ylide 8.
Abstract: Das metallierte 1,3-Diphospha-2-propanon Fe2(CO)6[(iPr)2N–PC(O)P–N(iPr)2] (3) reagiert mit zwei Aquivalenten Me2S(O)-CH2 unter Insertion jeweils einer CH2-Gruppe in beide PC(O)-Bindungen zu dem 1,5-Diphospha-3-pentanon-Derivat 6. Die Behandlung von 3 mit Ph3PCH2 liefert das carbonylstabilisierte Phosphorylid 8. Von 6 wurde eine Rontgenstrukturanalyse durch-gefuhrt. Strukturaufklarung von 8 erfolgte spektroskopisch (IR, 1H-, 13C-, 31P-NMR, MS). Transition Metal Sulfur Ylide Complexes, XXVI. – Reactivity of the (1,3-Diphospha-2-propanone)iron Complex Fe2(CO)6-[(iPr)2N–PC(O)P–N(iPr)2] towards the Ylides Me2S(O)CH2 and Ph3PCH2. Synthesis and Structure of Fe2(CO)6{[(iPr)2N–PCH2]2CO} The metal-functionalized 1,3-diphospha-2-propanone Fe2(CO)6-[(iPr)2N–PC(O)P–N(iPr)2] (3) reacts with two equivalents of Me2S(O)CH2 to give the 1,5-diphospha-3-pentanone derivative 6 by insertion of one CH2 group into each PC(O) bond. Treatment of 3 with Ph3PCH2 affords the carbonyl-stabilized phosphorus ylide 8. The molecular structure of 6 is established by X-ray analysis. Structure elucidation of 8 is based on spectroscopic data (IR, 1H-, 13C-, 31P-NMR, MS).

Journal ArticleDOI
TL;DR: In this paper, an accurate measurement of birefringence, optical activity and rotation of the optical indicatrix of BaMnF4 has been made by using HAUP method near the incommensurate transition point of 250 K.
Abstract: Accurate measurements of birefringence, optical activity and rotation of the optical indicatrix of BaMnF4 have been made by using HAUP method near the incommensurate transition point of 250 K. The IC phase is optically active below Ti and the indicatrix rotates below Ti around all the crystallographic axes.

Book ChapterDOI
01 Jan 1989
TL;DR: In this article, generalized n-th order blending operators are introduced, which share many relevant properties of the classical N-th-order blending operators, including their potential for data reduction, and quite elegant upper bounds for the approximation error are given using mixed moduli of smoothness of appropriate orders.
Abstract: The present note deals with various aspects concerning n-th order blending operators as introduced by Delvos and Posdorf in [2]. These operators constitute a generalization of the well-known technique of discrete blending interpolation as discussed in [6], among others. The motivation of our contribution is two-fold. First, we stress the fact that applications of this technique should not be restricted to those cases in which the univariate building blocks are projectors. To this end, we introduce so-called generalized n-th order blending operators which share many relevant properties of the classical n-th order blending operators, including their potential for data reduction. Secondly, we shall show that quite elegant upper bounds for the approximation error can be given using mixed moduli of smoothness of appropriate orders and some previous results of the present author. Two applications are added in order to illustrate our more general approach.

Journal ArticleDOI
TL;DR: In this article, the authors proposed to remove the ligand sphere together with the outer shell of metal atoms to generate the inner naked M13 nuclei, which are metastable and build up novel structures.
Abstract: The desirable aim to create uniform naked metal clusters still fails. On the other hand, there exist many ligand stabilized clusters. If there was any possibility of eliminating the ligand sphere, a wide field of study, naked clusters of the same size, could be opened. Naked clusters with a magic number of metal atoms (full shell clusters) should have a special stability because of their complete outer geometry. Two-shell clusters of the type M55L12Clx (M = Au, Rh, L = PPh3, x = 6; M Rh, Ru, L = P(t-BU)3, x = 20, M = Pt, L = As(t-Bu)3, x = 20; M = Co, L = PMe3, x = 20) seem to be suited for studying those problems. As can be seen from HRTEM images and from other investigations, they have a cubic close packed structure (ccp) with the outer geometry of a cuboctahedron. The 12 vertices are coordinated by the 12 ligands L, and the chlorine atoms partially fill the gaps between the phosphine or arsine molecules. The nature of the figands makes the cluster molecules soluble in organic solvents. The transformation into water soluble compounds succeeds if PPh3 is exchanged by the hydrophilic derivative Ph2PC6H4SO3Na·2H2O. So, the cluster Au55(Ph2PC6H4SO3Na·2H2O)12Cl6 can be obtained as a very stable (in contrast to Au55(PPh3)12Cl16) water soluble compound which is completely dissociated in aqueous solution. Using a 100 kV electron beam, small crystalline areas of probably intact cluster molecules can be imaged by TEM. The giant cluster Pd56l(Phen)360190–200 (phen = phenanthroline) is obtained by reduction of palladium acetate with H2 in the presence of appropriate amounts of phen with subsequent oxidation by oxygen. The generation of naked clusters indeed succeeds if the M55L12Clx species are degraded in solution by 20 V d.c., using Pt electrodes. The ligand sphere together with the outer shell of metal atoms is eliminated, generating the inner naked M13 nuclei. These full-shell particles are metastable and build up novel structures. The structural principle can be described as an aggregation of 13 M13 particles, combined in a kind of close packed arrangement. The (M13)13 superclusters again act as building blocks and form particles [(M13)13]n. This construction principle is realized for all metals in this investigation, i.e. Au, Rh, Ru, Pt and Co.