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1.
The role of the low-lying two-electron excited 1A g states of C 60 in contributing to its hyperpolarizability γ is investigated by singly and doubly excited CI calculations in the semi-empirical CNDO/S approximation. It is found that inclusion of the doubly excited configurations is essential in evaluating γ. The calculated values of γ zzzz(−3ω; ω, ω, ω) at wavelengths of ∞, 1.9, 1.83 μm sufficiently far from the first resonance are in reasonable agreement with experiment. 相似文献
2.
The hydroxo-complexes [{PdR(PPh 3)(μ-OH)} 2] (R = C 6F 5 or C 6Cl 5) have been obtained by reaction of the corresponding [{PdR(PPh 3)(μ-Cl)}2] complexes with NBu 4OH in acetone. In this solvent, the reaction of the hydroxo-bridged complexes with pyrazole (Hpz) and 3,5-dimethylpyrazole (Hdmpz) in 1:2 molar ratio leads to the formation of the new complexes [{Pd(C 5F 5)(PPh 3)(μ-azolate)}2] and [{Pd(C 6Cl 5)(PPh 3)} 2(μ-OH)(μ-azolate)] (azolate = pz or dmpz). The reaction of the bis(μ-hydroxo) complexes with Hpz and Hdmpz in acetone in 1:1 molar ratio has also been studied, and the resulting product depends on the organic radical (C 6F 5 or C 6Cl 5) as well as the azolate (pz or dmpz). The identity of the isomer obtained has been established in every case by NMR ( 1H, 19F and 31P) spectroscopy. The reaction of the bis(μ-hydroxo) complexes with oxalic (H 2Ox) and acetic (HOAc) acids yields the binucle ar complexes [{PdR(PPh 3)}2(μ-Ox)] (R = C 6F 5 or C 6Cl 5) and [{Pd(C 6F 5)(PPh 3)(μ-OAc)}2], respectively. [{Pd(C 6F 5)(PPh 3)(μ-OH)} 2] reacts with PPh 3 in acetone in 1:2 ratio giving the mononuclear complex trans-[Pd(C 6F 5) (OH)(PPh 3) 2], whereas the pentachlorophenylhydroxo complex does not react with PPh 3, even under forcing conditions. 相似文献
3.
The
and
-benzyl derivatives (1 and 2, respectively) of (+)-camphor have been synthesized and are found to exert a strong influence on the circular dichroism n→π * Cotton effects: 1: Δε 301max -0.36 (n- heptane) and 2: Δε 302max +3.22, relative to camphor: Δε 304max +1.8 (n-heptane). Evidence for electric dipole transition moment coupling in these γ, δ -unsaturated systems is found in the n→π * UV: 1: ε 291max 84 (n-heptane) and 2: ε 285max 303, relative to camphor: ε 290max 25. 相似文献
4.
The compounds C 5H 5Co(η 2-CH 3CHS)PMe 3 (I) and C 5H 5Co(η 2-CH 3CHSe)PMe 3 (II) are prepared from C 5H 5Co(CO)PMe 3, CH 3CHBr 2 and NaSH or NaSeH, respectively. The synthesis of the corresponding rhodium complexes C 5H 5Rh(η 2-CH 3CHS)P(i-Pr) 3 (VI) and C 5H 5Rh(η 2-CH 3CHSe)P(i-Pr) 3 (VII) has been achieved through hydrogenation of C 5H 5Rh(η 2-EC=CH 2)P(i-Pr) 3 (E = S, Se), using RhCl(PPh 3) 3 as a catalyst. The crystal structure of VII has been determined. 相似文献
5.
We have tailored some interesting mono- and diporphyrins, viz., 5, 10, 15, 20-tetrakis(octadecyloxyphenyl)-21 H,23 H-porphyrin (TP), 5, 15-bis(3, 5-dioctylphenyl)-2, 8, 12, 18-tetramethyl-3, 7, 13, 17-tetradodecyl-21 H,23 H-porphyrin (AP) and 1, 3-bis(10′,20′-diundecyl-21′ H,23′ H-porphyrin-5′-yl)benzene (DP) as host molecules to study their complexation behavior with C 60 and C 70. Fluorescence spectroscopic measurements showed that emission of TP, AP and DP in toluene was quenched in the presence of C 60 or C 70. Large binding constants ( K) in the magnitude of 1.5 × 10 4 dm 3 mol −1 have been obtained for the 1:1 complexes of C 70 with TP, AP and DP. However, the C 60 complexes have exhibited 8.5 times smaller K compared to C 70 complexes. Ab initio theoretical calculations give a good support in favor of strong complexation between C 70 and porphyrins. 相似文献
6.
A structural study of odd-numbered n-alkane (C n) binary mixtures (C 21 : C 23) was carried out on powder samples using a Guinier-de Wolff camera with increasing concentration of n-C 23 at 293 K. Despite the reports in the literature, these molecular alloys do not form an orthorhombic continuous homogeneous solid solution to C21 from C23 at “low temperature”. Instead, as already observed in two even-numbered Cn systems, X-ray diffraction results show the existence of seven solid solutions as the molar concentration of C23 increases: four terminal solid solutions, denoted β0(C21)β0(C23), isostructural with the “low temperature” phase of pure C21 and C23 (Pbcm), β′0(C21) and β′0(C23), identical to the phase β′0 which appears in pure C23 above the δ transition, and three orthorhombic intermediate solid solutions, designated β″1, β′1 and β″2. On the basis of powder X-ray photographs, the phases β″1 and β″2 (C21 : C23) are indistinguishable, and they are isostructural with the intermediate solid solution β″ of the even-numbered Cn binary systems (C22 : C24) and (C24 : C26). The phase β′1(C21 : C23) is also isostructural with the two indistinguishable intermediate solid solutions β′1 and β′2 of the molecular alloys (C22 : C24) and (24 : C26). From this study and our other laboratory results, the sequences of appearance of the solid solutions and the structural identities between these phases are established at “low temperature” for all the binary molecular alloys of consecutive Cn (odd-odd, even-even or odd-even: 19 < n < 27) when increasing the solute concentration. 相似文献
7.
Bilirubin-IX, the end product of porphyrin metabolism in mammals and the neurotoxic yellow-orange pigment of jaundice, exhibits a strong tendency to fold like a book into either of two interconverting enantiomeric conformations, which are further stabilized by intramolecular hydrogen bonding. Bilirubin exhibits optical activity in R-(-)-ethylmethylsulfoxide solvent, as seen by moderately strong bisignate circular dichroism Cotton effects (Δε max452=+10.9,Δε max404=-4.5), and in dichloromethane solution in the presence of 2 M R-(+)-methyl- p-tolylsulfoxide its circular dichroism spectrum (Δε 463max=+11.2,Δε 412max=-7.1) is comparably strong. As observed earlier for chiral recognition of bilirubin by optically active amines and serum albumins, the optically active sulfoxide acts as a chiral complexation agent to induce an asymmetric transformation of bilirubin, whose bisignate circular dichroism spectra are characteristic of an exciton splitting arising from interaction of the two component dipyrrinone chromophores. 相似文献
8.
A series of luminescent rhenium(I) monoynyl complexes, [Re(N---N)(CO) 3(CC---R)] (N---N=bpy, tBu 2bpy; R=C 6H 5, C 6H 4---Cl-4, C 6H 4---OCH 3-4, C 6H 4---C 8H 17-4, C 6H 4---C 6H 5, C 8H 17, C 4H 3S, C 4H 2S---C 4H 3S, C 5H 4N), together with their homo- and hetero-metallic binuclear complexes, {Re(N---N)(CO) 3(CC---C 5H 4N)[M]} (N---N=bpy, tBu 2bpy; [M]=[Re{(CF 3) 2-bpy}(CO) 3]ClO 4, [Re(NO 2-phen)(CO) 3]ClO 4, W(CO) 5) have been synthesized and their electrochemical and photoluminescence behaviors determined. The structural characterization and electronic structures of selected complexes have also been studied. The luminescence origin of the rhenium(I) alkynyl complexes has been assigned as derived states of a [dπ(Re)→π*(N---N)] metal-to-ligand charge transfer (MLCT) origin mixed with a [π(CCR)→π*(N---N)] ligand-to-ligand charge transfer (LLCT) character. The assignments are further supported by extended Hückel molecular orbital (EHMO) calculations, which show that the LUMO mainly consists of π*(N---N) character while the HOMO is dominated by the antibonding character of the Re---CCR moiety resulted from the overlap of the dπ(Re) and π(CCR) orbitals. 相似文献
9.
The reaction of the anionic mononuclear rhodium complex [Rh(C 6F 5) 3Cl(Hpz)] t- (Hpz = pyrazole, C 3H 4N 2) with methoxo or acetylacetonate complexes of Rh or Ir led to the heterodinuclear anionic compounds [(C 6F 5) 3Rh(μ-Cl)(μ-pz)M(L 2)] [M = Rh, L 2 = cyclo-octa-1,5-diene, COD (1), tetrafluorobenzobarrelene, TFB (2) or (CO) 2 (4); M = Ir, L 2 = COD (3)]. The complex [Rh(C 6F 5) 3(Hbim)] − (5) has been prepared by treating [Rh(C 6F 5) 3(acac)] − with H 2bim (acac = acetylacetonate; H 2bim = 2,2′-biimidazole). Complex 5 also reacts with Rh or Ir methoxo, or with Pd acetylacetonate, complexes affording the heterodinuclear complexes [(C 6F 5) 3Rh(μ-bim)M(L 2)] − [M = Rh, L 2 = COD (6) or TFB (7); M = Ir, L 2 = COD (8); M = Pd, L 2 = η 3-C 3H 5 (9)]. With [Rh(acac)(CO) 2], complex 5 yields the tetranuclear complex [{(C 6F 5) 3Rh(μ-bim)Rh(CO) 2} 2] 2−. Homodinuclear Rh III derivatives [{Rh(C 6F 5) 3} 2(μ-L) 2] ·- [L 2 = OH, pz (11); OH, S tBu (12); OH, SPh (13); bim (14)] have been obtained by substitution of one or both hydroxo groups of the dianion [{Rh(C 6F 5) 3(μ-OH)} 2] 2− by the corresponding ligands. The reaction of [Rh(C 6F 5) 3(Et 2O) x] with [PdX 2(COD)] produces neutral heterodinuclear compounds [(C 6F 5) 3Rh(μ-X) 2Pd(COD)] [X = Cl (15); Br (16)]. The anionic complexes 1–14 have been isolated as the benzyltriphenylphosphonium (PBzPh 3+) salts. 相似文献
10.
1H NMR spectra of binuclear metallocene hydride complexes, (η 5 : η 5-C 10H 8)(C 5H 5) 2M 2(μ-H) 2 (M = Nb, 20°C and Ti, (−60 to +25°C), were studied. The Nb complex is diamagnetic and gives a high resolution spectrum. The coordination of bridging hydride H atoms provides Nb atoms with complete 18 electron configuration. In its ground state, the Ti complex is also diamagnetic (the spectrum at −60°C agrees to that) in spite of only 17 electron configuration of each Ti atom. However, the population of the excited triplet state in the case of the Ti complex is appreciable at temperatures higher than −30°C, the proton resonance lines being shifted downfield and significantly broadened as compared with the spectrum at −60°C. 相似文献
11.
A molecular complex of fullerene C 60 with triptycene, TPC·C 60 is obtained. The complex has a three-dimensional packing of C 60 molecules. According to the IR spectra, the freezing of free rotation of C 60 molecules in the complex is maintained up to 360 K. The XP-spectra of TPC·C 60 show the suppression of π–π * transitions of TPC phenylene rings. The separation of C 60 molecules by TPC ones in TPC·C 60 results in low intensity of the C 60 transitions in the 420–500 nm range in an optical spectrum. This absorption is assumed as that attributed to intermolecular transitions between adjacent C 60 molecules. 相似文献
12.
The synthesis of the new (η 2-dppe)(η 5-C 5Me 5)Fe---CC---1,3-(C 6H 4X) ( m-2a/2b; X=F/Br) and (η 2-dppe)(η 5-C 5Me 5)Fe---CC---1,4-(C 6H 4I) (2c) complexes, as well as the solid-state structure of the known (η 2-dppe)(η 5-C 5Me 5)Fe---CC---1,4-(C 6H 4F) (2a) complex are described. The catalytic coupling reactions of the bromo complexes with various alkynes were next investigated. Starting from the known (η 2-dppe)(η 5-C 5Me 5)Fe---CC---1,4-(C 6H 4Br) complex (2b), the synthesis of the (η 2-dppe)(η 5-C 5Me 5)Fe---CC---1,4-(C 6H 4)---CC---H complex (6d) and of the corresponding silyl-protected precursors (η 2-dppe)(η 5-C 5Me 5)Fe---CC---1,4-(C 6H 4)CC---SiR 3 (6b/6c; R= iPr/Me) are reported. By use of lithium---bromine exchange reactions on 2b, the silyl- (7a; E=Si; R=Me) and tin- (7b–7d; E=Sn; R=Me, Bu, Ph) substituted analogues (η 2-dppe)(η 5-C 5Me 5)Fe---CC---1,4-(C 6H 4)ER 3 are also isolated. The spectroscopic and electrochemical characterisations of all these new Fe(II)/Fe(III) redox-active building blocks are presented and the electronic substituent parameters for the “(η 2-dppe)(η 5-C 5Me 5)Fe---CC” group are determined by means of 19F-NMR. 相似文献
13.
Cp 2MoH 2 reacts with methyl acrylate in the presence of acetylenes (L = C 2H 2, C 2Me 2, HCC tBu, HCCSiMe 3, C 2(SiMe 3) 2, HCCCH 2OMe, HCCCH 2NMe 2) to form acetylene complexes Cp 2Mo(L) 5. Protonation takes place with CF 3CO 2H at −80°C to give short-lived cations [Cp 2MoH(L) + (8) (L = C 2Me 2, HCCSiMe 3, C 2(SiMe 3) 2). The structure of [Cp 2MoH{η 2-C 2(SiMe 3) 2}]PF 6(9) was determined by an X-ray diffraction study. 相似文献
14.
The reactions of the half-sandwich molybdenum(III) complexes CpMo(η 4-C 4H 4R 2)(CH 3) 2, where Cp=η 5-C 5H 5 and R=H or CH 3, with equimolar amounts of B(C 6F 5) 3 have been investigated in toluene. EPR monitoring shows the formation of an addition product which does not readily react with Lewis bases such as ethylene, pyridine, or PMe 3. The analysis of the EPR properties and the X-ray structure of a decomposition product obtained from dichloromethane, [CpMo(η 4-C 4H 6)(μ-Cl)(μ-CH 2)(O)MoCp][CH 3B(C 6F 5) 3], indicate that the borane attack has occurred at the methyl position. 相似文献
15.
A series of fluorinated and one non-fluorinated β-diketonate complexes of oxovanadium IV have been prepared, their gas phase IR spectra examined, vapour pressures determined and their vapour phase thermal decomposition investigated. Decomposition of the fluorinated complexes occurred according to the overall reaction scheme VO(β-diket) 2»VOF 2 + Furanone. The furanones C 5HF 5O 2, C 5H 4F 2O 2 and C 8H 10F 2O 2 were isolated and identified. The non-fluorinated complex gave the parent diketone and a vanadium oxide as its principal products. 相似文献
16.
Theoretical calculations (DFT, MP2) are reported for up to four sets of reaction products of trimethylphosphine, (CH 3) 3P, each with H 2O, HCl and HF together with DFT calculations on up to three sets of reaction products of substituted phosphonium cations, (CH 3) 3P–R +. These products comprise (a) P(III) normal complexes (CH 3) 3PHY, (b) P(IV) ‘reverse’ complexes Y(H–CH 2) 3P–R, (c) P(IV) ylidic complexes YHCH 2(CH 3) 2P–R and (d) P(V) covalent compounds Y–P(CH 3) 3–R for Y=HO, Cl and F and R=H, CH 3, C 2H 5, C 2H 4OH and C 2H 4OC:OCH 3. Calculations are carried out at the B3LYP/6-31+G(d,p) level in all cases and also at the MP2/6-31+G(d,p) level for systems in which R=H. Minimum energy structures are determined for predicted complexes or structures and geometrical properties, harmonic vibrations and BSSE corrected binding energies are reported and compared with the limited experimental information available. Potential energy scans predict equilibria between covalent trigonal bipyramidal P(V) forms and reverse complexes comprising hydrogen bonded or ion pair, tetrahedral P(IV) forms separated by low potential energy barriers. Similar scans are also reported for equilibria between reverse complexes and ylidic complexes for Y=OH and R=CH 3, C 2H 5, C 2H 4OH and C 2H 4OC:OCH 3. Corrected binding energies, structures and values of harmonic modes are discussed in relation to bonding The names ‘pholine’ and ‘acetylpholine’ are suggested for phosphorus analogues to choline and acetylcholine. 相似文献
17.
In order to understand the nature of the putative cationic 12-electron species [M(η 5:η 1-C 5R 4SiMe 2NR′)R″] + of titanium catalysts supported by a linked amido-cyclopentadienyl ligand, several derivatives with different cyclopentadienyl C 5R 4 and amido substituents R′ were studied systematically. The use of tridentate variants (C 5R 4SiMe 2NCH 2CH 2X) 2− (C 5R 4=C 5Me 4, C 5H 4, C 5H 3tBu; X=OMe, SMe, NMe 2) allowed the NMR spectroscopic observation of the titanium benzyl cations [Ti(η 5:η 1-C 5Me 4SiMe 2NCH 2CH 2X)(CH 2Ph)] +. Isoelectronic neutral rare earth metal complexes [Ln(η 5:η 1-C 5R 4SiMe 2NR′)R″] can be expected to be active for polymerization. To arrive at neutral 12-electron hydride and alkyl species of the rare earth metals, we employed a lanthanide tris(alkyl) complex [Ln(CH 2SiMe 3) 3(THF) 2] (Ln=Y, Lu, Yb, Er, Tb), which allows the facile synthesis of the linked amido-cyclopentadienyl complex [Ln(η 5:η 1-C 5Me 4SiMe 2NCMe 3)(CH 2SiMe 3)(THF)]. Hydrogenolysis of the linked amido-cyclopentadienyl alkyl complex leads to the dimeric hydrido complex [Ln(η 5:η 1-C 5Me 4SiMe 2NCMe 3)(THF)(μ-H)] 2. These complexes are single-site, single-component catalysts for the polymerization of ethylene and a variety of polar monomers such as acrylates and acrylonitrile. Nonpolar monomers such as -olefins and styrene, in contrast, give isolable mono-insertion products which allow detailed studies of the initiation process. 相似文献
18.
Mixed-carboxylato β-diketonato complexes of chromium (III) (R=C 13H 27, C 15H 31 or C 17H 35 and L=CH 3OH) [Cr 3O(OOCR) 3(dike) 3L 3] + have been synthesized by enforced substitution reactions of [Cr 3O(OOCCH 3) 7(H 2O)] first with straight chain fatty acids (myristic, palmitic or stearic acid) and then with β-diketones (Hβ-dike) like acetylacetone(Hacac) or benzoylacetone(Hbzac) in toluene under reflux. These are new type of oxo-bridged chromium(III) complexes in which one ligand is a fatty acid while the other one is a β-diketone. The complexes were characterized by elemental analyses, spectral (infrared, electronic, FAB mass and powder XRD) studies, molar conductance and magnetic susceptibility measurements. Bridging coordination modes for both carboxylate and β-diketonate anions were indicated by presence of νasym(Cr 3O) vibrations in the infrared spectra. Trinuclear nature of the complexes and their structural features have been discussed on the basis of physicochemical studies. 相似文献
19.
The atomic cations of Sr and Mo have been observed to add sequentially up to four molecules of C 60 in helium at 0.35 Torr and room temperature in the flow tube of a modified inductively coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. The available center-of-mass energy in collision-induced dissociation experiments of approximately 1.3 eV failed to remove C 60 from M +(C 60) 4. A structure is proposed for M +(C 60) 4 cations in which the bonding involves η 6 interaction of the metal with the C 60 ligands and η 2-to-η 2 interactions between the C 60 ligands. 相似文献
20.
CpIr(η 4-C 6H 6) (2) has been obtained in high yield by a four-step synthesis. Thermal reaction of 2 with CpCO(C 2H 4) 2 and photochemical reaction of 2 with CpRh(C 2H 4) 2 or CpRh(C 2H 4) 2 give the compounds μ-(η 3: η 3-C 6H 6)CoIrCp 2 (3), μ-(η 3: η 3-C 6H 6)RhIrCp 2 (4), and μ-(η 3: η 3-C 6H 6)(RhCp)(IrCp) (5), respectively. The X-ray crystallography data of 3 and 4 reveal a boat-shaped conformation of the synfacially bridging benzene ligand with a rather long Co---Ir bond distance in 3 and a relatively short Rh---Ir bond length in 4 which are caused by almost constant folding angles of the benzene unit. The dynamic behaviour of the benzene bridge was investigated by NMR spectrometry. 相似文献
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