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1.
We continue the studies on the so–called genuine Bernstein–Durrmeyer operators U
n
by establishing a recurrence formula for the moments and by investigating the semigroup T(t) approximated by U
n
. Moreover, for sufficiently smooth functions the degree of this convergence is estimated. We also determine the eigenstructure
of U
n
, compute the moments of T(t) and establish asymptotic formulas.
Received: January 26, 2007. 相似文献
2.
H. Homborg 《无机化学与普通化学杂志》1982,493(1):104-120
Vibrational Raman Spectra of Hexahalo Complexes of OsIV (X = Cl, I) and IrIV (X = Cl, Br) at 80 K The Resonance-Raman (RR) spectra of the tetrabutyl- resp. tetraethylammonium salts of [OsCl6]2?, [OsI6]2?, [IrCl6]2?, and [IrBr6]2? have been investigated with the excitation-lines of an Ar+ and Kr+ laser. Devices with a movable sample holder for low-temperature experiments (80 K) are described. The anormal intensities of some of the Ra-active fundamentals are attributed to the RR effect. As a rule the deformation vibration υ5(T2g) is RR enhanced if excited within a π—π*(dt2g)-CT-transition and the stretching vibration υ2(Eg) is RR-enhanced within a π—σ*(deg)-CT-transition. The dispersion of the degree of depolarisation of the three Ra-active fundamentals of [IrBr6]2? demonstrates, that this rule cannot only be applicated to the symmetrical but also to the antisymmetrical part of the scattering tensor. 相似文献
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6.
CrIII Phthalocyaninates: Synthesis, Properties, and Crystal Structure of l-Bis(triphenylphosphine)iminium trans-Di(nitrito(O))phthalocyaninato(2–)chromate(III) [Cr(H2O)2Pc2?]Ix reacts with excess (PNP)NO2 in dimethylformamide to yield less soluble greenblack l-bis(triphenylphosphine)iminium trans-di(nitrito(O))phthalocyaninato(2–)chromate(III), l(PNP)trans[Cr(ONO)2Pc2?], which crystallizes in the triclinic space group P1 (No. 2) with Z = 2. The Cr atom is in the center of the Pc2? ligand and the two nitrite ions are monodentate O-coordinated in a mutually trans arrangement to the Cr atom. The Cr? O and Cr? Niso bond distances are 1.9898(14) und 1.981(2) Å, respectively. The geometric data of the coordinated nitrite ion are: d(N? O) = 1.307(2) Å; d(N? O) = 1.205(2) Å; ?(O? N? O) = 113.7(2)°; ?(Cr? O? N) = 116.85(12)°. The non-bonding O atoms are trans to the Cr atom. The Pc2? ligand is slightly saddled. Three weak spin-allowed trip-quartet(TQ) transitions (in 103 cm?1): TQ1 (8.20) < TQ2 (11.3) < TQ3 (20.33) and the characteristic π-π* transitions of the Pc2? ligand: B (14.68) < Q1 (27.1) < Q2 (29.0) < N (35.4) are observed in the UV-VIS-NIR spectrum. Prominent luminescence spectra are obtained by excitation within the TQ1 region, in which the spin-forbidden trip-sextet transition at 7376 cm?1 dominates at low temperatures (T < 50 K). The vibrational spectra are discussed. In coincidence of the excitation lines with TQ3, vs(Cr? O) at 378 cm?1 is selectively resonance Raman (RR) enhanced. vas(Cr? O) is observed in the FIR spectrum at 391 cm?1. The following internal vibrations (in cm?1) of the nitrito ligand are in the MIR spectrum: vas(N? O)/1447 > vas(N? O)/1018/1029 > δ(O? N? O)/828 and in the RR-spectrum: vs(N? O)/1410 > vs(N? O)/952, the last followed by three overtones. 相似文献
7.
Synthesis and Spectroscopical Characterization of Di(halo)phthalocyaninato(1–)rhodium(III), [RhX2Pc1?] (X = Cl, Br, I) Bronze-coloured di(halo)phthalocyaninato(1–)-rhodium(III), [RhX2Pc1?] (X = Cl, Br) and [RhI2Pc1?] · I2 is prepared by oxidation of (nBu4N)[RhX2Pc2?] with the corresponding halogene. Irrespective of the halo ligands, two irreversible electrode reactions due to the first ringreduction (ER = ?0,90 V) and ringoxidation (EO = 0,82 V) are present in the cyclovoltammogram of (nBu4N)[RhX2Pc2?]. The optical spectra show typical absorptions of the Pc1?-ligand at 14.0 kK and 19.1 kK. Characteristic vibrational bands are at 1 366/1 449 cm?1 (i. r.) and 569/1 132/1 180/1 600 cm?1 (resonance Raman (r. r.)). The antisym. (Rh? X)-stretching vibration is observed at 294 cm?1 (X = Cl), 240 cm?4 (Br) and 200 cm?1 (I). Only the sym. (Rh? I)-stretching vibration at 133 cm?1 is r. r. enhanced together with a strong line at 170 cm?1, which is assigned to the (I? I)-stretching vibration of the incorporated iodine molecule. Both modes show overtones and combinationbands. 相似文献
8.
Spectroscopical Properties of Di(phthalocyaninato)metalates(III) of the Rare Earth Elements. Part 2: The Multinuclear (1H, 13C, 15N, 17O, and 31P) NMR Spectra and Determination of Complex Bound Water The 1H, 13C, 15N, 17O and 31P NMR spectra of (PNP)[Ln(Pc2?)2] and (TDOA)[Ln(Pc2?)2] (Ln = La …? (—Pm) …? Lu); PNP: di(triphenylphosphine)-iminium; TDOA: Tri(n-dodecyl)n-octylammonium dissolved in CD2Cl2 are reported. With the exception of the nitrogen atoms of the cations all light atoms of both homologues complex salt rows have been detected and assigned. Proof of the presence of additional water contained in the (solid) complex salts has been given unambigously. The otherwise strong Fermi contact interactions diminuish rapidly with growing distance from the paramagnetic centre favouring dipolar (pseudo-contact) interactions. As a consequence the mostly element independent paramagnetic shifts of the atoms situated on the periphery of the anion as well as those of the cations and water are determined by the distance factor. Therefore a first glance of the structure of the ion-pair present in solution emerges, in which the water molecule seems to play an important role. 相似文献
9.
Zirconiumphthalocyanines: Synthesis and Properties of Chloride Ligated Phthalocyanines of Ter- and Quadrivalent Zirconium; Crystal Structure of cis-Di(triphenylphosphine)iminium-tri(chloro)phthalocyaninato(2–)zirconate(IV)-di(dichloromethane) cis-Di(chloro)phthalocyaninato(2–)zirconium(IV) is obtained by the reaction of ZrCl4 with phthalodinitrile in 1-chloronaphthaline at 230°C. It reacts with molten di(triphenylphosphine)iminiumchloride ((PNP)Cl) yielding cis-di(triphenylphosphine)iminium-tri(chloro)phthalocyaninato(2-)zirconate(IV), cis-(PNP)[ZrCl3Pc2?]. This crystallizes with two molecules of dichloromethane in the monoclinic space group P21/n with the lattice constants a = 15.219(4) Å, b = 20.262(10) Å, c = 20.719(4) Å, b? = 93.46(2)°, Z = 4. The seven coordinated Zr atom is situated in a “square base-trigonal cap” polyhedron. The plane of the three chlorine atoms runs parallel to the plane of the four isoindole nitrogen atoms Niso. The Zr–Cl distances range from 2.49 to 2.55 Å, the Zr? Niso distances from 2.26 to 2.29 Å. Due to ion packing effects the Pc2? ligand shows an asymmetrical convex distortion. The PNP cation adopts the bent conformation. The P? N? P angle is 139°, the P? N distance 1.58 Å. As confirmed by the cyclovoltammograms cis-(PNP)[ZrCl3Pc2?] is oxidized (anodically or chemically by Cl2) to yield cis-tri(chloro)phthalocyaninato(1–)zirconium(IV) and reduced (cathodically or chemically by [BH4]?) yielding chlorophthalocyaninato(2–)zirconium(III) and cis-di(triphenylphosphine)iminium-di(chloro)phthalocyaninato(2–)zirconate(III). The optical spectra show the typical π–π*-transitions of the Pc2? resp. Pc? ligand not much affected by the different states of oxidation and coordination of zirconium. The same is true for the vibrational spectra of the Pc2? resp. Pc? ligand. In the f.i.r. spectra between 350 and 150 cm?1 the asym. and sym. Zr? Cl stretching and Cl? Zr? Cl deformation vibration as well as the asym. Zr? N stretching vibration of the [ZrClxN4] skeleton (x = 1–3) is assigned. 相似文献
10.
Osmium(II) Phthalocyanines: Preparation and Properties of Di(acido)phthalocyaninatoosmates(II) “H[Os(X)2Pc2?]” (X = Br, Cl) reacts in basic medium or in the melt with (nBu4N)X forming less stable, diamagnetic, darkgreen (nBu4N)2[Os(X)2Pc2?]. Similar dicyano and diimidazolido(Im) complexes are formed by the reaction of “H[Os(Cl)2Pc2?]” with excess ligand in the presence of [BH4]?. The cyclic voltammograms show up to three quasireversible redoxprocesses: E1/2(I) = 0.13 V (X = CN), ?0.03 V (Im), ?0.13 V (Br) resp. ?0.18 V (Cl) is metal directed (OsII/III), E1/2(II) = 0.69 V (Cl), 0.71 V (Br), 0.83 V (CN), 1.02 V (Im) is ligand directed (Pc2?/?) and E1/2(III) = 1.17 V (Cl) resp. 1.23 V (Br) is again metal directed (OsIII/IV). Between the typical “B” (~16.2 kK) and “Q” (~29.4 kK), “N regions” (~34.1 kK) up to seven strong “extra bands” of the phthalocyanine dianion (Pc2?) are observed in the uv-vis spectrum. Within the row CN > Im > Br > Cl, most of the bands are shifted slightly, the “extra bands” considerably more to lower energy in correlation with E1/2(I). The vibrational spectra are typical for the Pc2? ligand with D4h symmetry. M.i.r. bands at 514, 909, 1 173 and 1 331 cm?1 are specific for hexa-coordinated low spin OsII phthalocyanines. In the resonance Raman (r.r.) spectra polarized, depolarized or anomalously polarized deformation and stretching vibrations of the Pc2? ligand will be selectively enhanced, if the excitation frequency coincides with “extra bands”. With excitation at ~19.5 kK the intensity of the symmetrical Os? X stretching vibration at 295 cm?1 (X = Cl), 252 cm?1 (X = Im) and 181 cm?1 (X = Br) is r.r. enhanced, too. The asymmetrical Os? X stretching vibration is observed in the f.i.r. spectrum at 345 cm?1 (X = CN), 274 cm?1 (X = Cl), 261 cm?1 (X = Im) and 200 cm?1 (X = Br). 相似文献