ELECTRONIC SPECTRA OF HYPOCRELLIN A, B AND THEIR DERIVATIVES

In this paper, the electronic spectra of hypocrellin A and B (HA and HB) are studied in detail. It has been proved that their three visible absorption bands come respectively from the ππ transition of their conjugated systems and intramolecular proton transfer. In dilute solutions, their fluorescence spectra consist of the fluorescence peak of the neutral monomolecule and that of the zwitter-ions that are formed through proton transfer of excited states. In concentrated solution, the longer wavelength emission band is composed of the overlapped fluorescence peaks of zwitter-ions and excimers. The fluorescence spectra of the crystalline hypocrellin A and B consist of the fluorescence peaks of zwitter-ions and excimers and the fluorescence of neutral monomolecules could not be observed. Their relative intensities are closely related to the excitation wavelength.     

SYNTHESIS AND ELECTRONIC SPECTRA OF RUTNENIUM(Ⅱ)-1,1''''-BIISOQUINOLINE COMPLEXES

l,l'-biisoquinoline can coordinate with ruthenfum(Ⅱ) to form a new series of mononuclear complexes and the electronic absorption of these complexes were measured and reasonably assigned.     

EXPERIMENTAL STUDY AND THEORETICAL INTERPR ETATION OF ELECTRONIC STRUCTURE OF CRYSTAL OF ETHYLENEDIAMINE COMPLEX OF NICKEL(Ⅱ)-SILVER(Ⅰ) THIOCYANATE

d-d electronic absorption spectrum of Ni(en)_3 [Ni (en)_2Ag_2(NCS)_6]·H_2O, ENST, was measured. Absorption bands are at 11,300, 13,150, 18,650, 23,000 and 28,700 cm~(-1). The electronic energy levels were calculated by means of ligand field theory. Its EPR spectrum was measured directly at 77 K without dilution with diamagnetic medium. Zero-field splitting and half-field transition were observed g=2.169±0.020, g= 2.164 ± 0.020 and |D|=0.095±0.003cm~(-1). This paper discusses synthetically and theoretically the experimental results of electronic structure and crystal structure of this complex crystal.     

ELECTRONIC STRUCTURE AND CHEMICAL BONDING OF BIS(TRIMETHYLSILYL)AMIDE DERIVATIVES OF LANTHANIDES(Ln(N(SiMe_3)_2)_3, Ln=Nd, Eu, Yb)

The electronic structure and chemical bonding of Ln(N(SiMe_3)_2)_3 have been studied by INDO calcula-tions. The results have shown that the Ln-N bonds are considerably covalent in character and that thecovalency decreases with increasing atomic numbers. A new explanation of the pyramidal structure of thecompounds has been proposed based on 5d orbital participation in bonding. With the calculation of asimplified model of Eu(N(SiMe_3)_2)_3. OPPh_3, the roles of electronic and steric effects in bonding have beencompared.     

ELECTRON SPIN RESONANCE OF γ -IRRADIATED COBALT(III) COMPLEXES; ELECTRONIC AND SPIN STATES OF HOT COBALT(II) IONS

Abstract

ESR investigation of the γ -ray irradiated Co(III) complexes have been carried out. The identification and the classification of the irradiation products on the basis of the ESR signal patterns, and the electronic and the spin states of the products are discussed.

Co(III) complexes are reduced by the γ irradiation into Co(II) complexes, where the produced Co(II) ions have low spin configurations, S = ½. Authors refer to these particular spin states as hot ions.     

PRECURSORS OF HEXA-AZAMACROCYCLES. SYNTHESIS AND X-RAY STRUCTURE OF 2,9-DIAMINOPHENANTHROLINEBISACETATE-Co(II) AND 6,6′-DIAMINOBIPYRIDINE-BISACETATE-M(II) (M = Ni,Cu)

Abstract

The synthesis, conventional characterisations and x-ray structures of the following monomeric complexes are given for 2,9-diaminophenanthroline-bisacetate-cobalt(II) ( A ) and 6,6′-diaminobipyridine-bisacetate-M(II) (M = nickel( C ) and copper( B )). Complex A crystalizes in the monoclinic, C2/c space group with a=12.813(6), b = 10.218(3), c= 13.811(5), Å; β= 118.17(2)°; Z=4; V=1549(2) ų. A total of 1787 unique reflections with F > 6σ(F) were refined to values of R and R_w 0.0461 and 0.0774, respectively. Complex B crystallizes in the triclinic, P-1 space group with a=10.099(5), b=10.257(5), c=8.015(11), Å; α=112.98(2), β=93.13(2), γ=92.960(2),°; Z=2; V = 761(1), ų. A total of 2603 unique reflections with F > 3.00σ(F) were refined to values of R and R_w 0.0764 and 0.1022, respectively. Complex C crystallizes in the monoclinic, P2₁/n space group with a=8.124(5), b=10.343(6), c=18.724(11), β=98.36(2),°; Z=4; V=1556(1), ų. A total of 2537 unique reflections with F > 3.00σ(F) were refined to values of R and R_w 0.0689 and 0.0975, respectively. The structures consist of six-coordinate [M(CH₃COO)₂(L)] (L=2,9-diaminophenanthroline or 6,6′-diaminobipyridine) discrete monomeric neutral species, although in the Cu(II) compound the elongation of two long Cu—O bonds, due to the Jahn-Teller effect, makes the metal essentially four-coordinate. In the Ni and Co compounds the acetate acts as a bidentate ligand. The diamino ligands are coordinated by the pyridine nitrogen atoms. The IR spectra of the complexes have been recorded and are discussed in relation to the crystal structure and the acetate coordination mode.     

ELECTRONIC EFFECTS OF POLYFLUORINATED SUBSTITUENTS ON THE POLYMERIZATION AND THE PROPERTIES OF POLYTHIOPHENES

Three series of polythiophenes containing fluoroalkoxy and fluoroether substituentswere prepared by electrochemical polymerization. The effect of substituents with fluoro-alkoxy or ether functional groups on the electrochemical polymerization of thiophene mono-mers and properties of the obtained polymers were analyzed. The introduction of a flu-oroether functional group at the 3-position of the thiophene ring leads to an increase ofthe oxidation potential of the monomer and to a decrease of the conductivity of the re-sulting polymers, even with the use of a CH_2 group as spacer. Conversely, the presenceof an oxygen atom directly at the 3-position of the thiophene ring, which offsets the nega-tive withdrawing effect of fluoroalkyl groups, facilitates the synthesis of highly conductingpolythiophenes.     

ELECTRONIC STRUCTURE OF(C_5H_5)_aCe(OCMe_a)

The electronic structure of(C_σH_σ)_σCe(OCMe_a)have beenstudied by INDO method.Some interesting results hays been obtained.     

STUDY ON ELECTRONIC STRUCTURE AND BONDING OF CLUSTER COMPOUND Sc_7Cl_(10)C_2

<正> The electronic structure and bonding of the cluster compound Sc7Cl10C2 have been studied by INDO method. In contract to the weak interaction between metal-metal in the compound Gd10Cl18C4, the bonding between metal atoms (Sc-Sc) in Sc7Cl10C2 is rather strong. The contribution of the orbitals 4s and 4p is larger than that of 3d to the Sc-Sc bond. In the cluster compound, besides Sc-Sc bonding, there are Sc -C and Sc -Cl bonds. The contribution of 3d is larger than that of 4s and 4p to the bond Sc-C. The contribution of 3d is slightly less than that of 4p and 4s to the bond Sc-Cl. Among the three kinds of bonds, the Sc-Cl bond is the weakest, the bond order of the Sc-Sc is close to that of the Sc-C.     

STUDIES ON CRYSTAL AND MOLECULAR STRUCTURES OF DEMETHYLCANTHARATE-M (M=Zn, Cu, Ni, Co)

The complexes of demethylcantharic acid coordinating with Zn~(2+), Cu~(2+), Ni~(2+) and Co~(2+) wereprepared and the five crystal structures were all determined by X-ray diffraction. Metal ions in thefive structures are of six-membered coordination. The demethylcantharate ions can act as a tri-,tetra- or penta-dentate ligand toward metal ions to form ion-pair structure, chain structure or threedimensional polymer structure respectively. The bridge oxygen atom in ligand always participatesin coordination. In the structures of KM(C_8H_8O_5)_2·6H_2O, the formal valence of M (Ni, Co) is+3, but the data of crystal structures show that M are M~(2+) ions and Ni may form a Ni~(2+) -stabilizedligand radical. In addition, the metal ions are assumed to be probes and some possible Interactionsbetween the acceptor and the receptor are discussed.     

CRYSTAL STRUCTURE OF COMPLEX OF Cu(Ⅱ) AND o-HYDROXYLBENZYLAMINE-O,N,N-TRIACETIC ACID(HBATA)

<正> [Cu(H2O)6][CuC13H12NO7]2.2H2O,Mr=904.5, Monoclinic, P21/n,a= 8.287(2), b=20.462(3), c=10.921(2)A,β=108.90(2), Z=2, V=1752.2A3, Dc=1.750 g/cm3, μ=13.166cm-1, R=0.042 for 2524 observed reflections. The title complex contains a [CuC13H12NO7]22- dimeric anion which consists of two mono-anions related by centrosymmetry and connecting each other by coordination bond Cu-O.The dimeric complex anion is compatible with an aquo-Cu(Ⅱ) cation that is located in centrosymmetric position. Here all Cu(Ⅱ) ions are six-coordinated with distorted octahedral configuration.     

EPR AND ELECTRONIC STRUCTURE OF Mo(V) COMPLEX Mo_2O_3(S_2CNEt_2)_4

<正> INTRODUCTION. Particular interest of some chemists has directed to the chemistry of molybdenum, as the oxidation states of molybdenum (-2～+6) are interesting and Mo atom in various forms usually is contained in the active site of enzymes or catalysts.     

THE INFLUENCE OF AXIALLIGANDS ON THE ELECTRONIC ABSORPTION SPECTRA OF PHTHALOCYANINATOIRON(Ⅱ)

Axial ligation in solution by phthalocyaninatolron(Ⅱ)with a varicty of donor ligandshas been widely investigated by measuring the visible spectral changes.It has been foundthat the axial ligation does not influence the Q_ο-οband so much as the Ⅱ-band,the appearance and the red shift of the latter under the action of σ-donation of ligands could be attri-buted to the Charge transfer from the metal d-orbital toward e_σ(π)orbital of PC-ring:e_g(dπ)M→Cg(π)Pc.A linear relation was found to exist between the energy of Q_ο-οand that of Ⅱ-band of ligands containing the same donor atoms(O,N,S,).This may be corre-lated with the electronegativity of donoratoms.     

INVESTIGATION OF ELECTRONIC SPECTRA OF AZOCOMPOUNDS——ABSORPTION AND EMISSION SPECTRA OF β-NAPHTHOL AZOBENZENE DERIVATIVES

Absorption and emission spectra of eight naphtholazobenzene derivatives are investigated.Absorption processes of n→π~* and π→π~* transition and emission processes from the excitedstates are studied separately in each compound. Intra- and inter-molecular energy transfersfrom the excited states of different chromophores are discussed. Effects of the molecularstructure and the pH value of the solution on the electronic spectra are discussed also. On thebasis of quantum chemistry theory, the spectral data are analyzed qualitatively.     

SYNTHESIS, SPECTRAL AND MAGNETIC CHARACTERISATION OF SOME BIMETALLIC ALKOXIDES OF NICKEL(Ⅱ)WITH GALLIUM(Ⅲ)AND ZIRCONIUM(IV)

Some interesting bimetallic isopropoxides of nickel(Ⅱ) with gallium(Ⅲ) and zirconium(Ⅳ), Ni[Ga(OPr~1)_4]_2 and Ni[Zr_2(OPr_1)_9]_2 have been synthesized by the interaction of NiCl_2·2Pr~1OH with K[Ga(OPr~1)_4],and K[Zr_2(OPr~1)_9] respectively, in 1:2 molar ratio. These bimetallic isopropoxides undergo facile alcohol interchange reactions with primary alcohols. However, reactions with tertiary alcohols result in the isolation of partially substituted derivatives with the compositions, Ni[Ga(OPr~1)(OBu~t)_3]_2 and Ni[Zr_2(OPr~1)_3(OBu~t)_6]_2. Characterisation of these derivatives has been made on the basis of elemental analyses, infrared, electronic spectral and magnetic susceptibility measurements. These studies suggest an octahedral geometry for nickel(Ⅱ) in the primary bimetallic alkoxides, while in the case of secondary and tertiary derivatives, an equilibrium is suggested between octahedral and tetrahedral forms.##属性不符     

LOCALIZED INDO STUDY OF THE ELECTRONIC STRUCTURE OF Sc(Sc_6Cl_(12)Co)

Spin-unrestricted localized INDO method was used to calculate the electronic structure ofrare earth cluster Sc(Sc_6Cl_(12)Co).Based on the analysis of the composition of the molecularorbitals and bond orders,it was pointed out that the interstitial transition metal atom Co in theoctahedral Sc skeleton forms strong covalent bond with six Sc atoms and the bonding of Sc-Cl is mainly ionic in character.There are nine valence molecular orbitals in the cluster.     

ELECTRONIC SPECTRA AND STRUCTURE OF PHRIDINUM HYDROGEN DI-μ-OXO-BIS(OXO-(OXALATO)AQUOMOLYBDATE(V))~(2-) ANION

<正> Introduction. Some active enzymes in nature contain Mo element. It has been shown by the experiments that Mo atoms in Mo enzYmes exist probably in dinucleus species with (V) or (VI) oxidational states. Therefore, the coordination chemistry of high-valency Mo compounds has attracted wide attention among which one is di-μ-oxo-dimolybdenum compound. The spectral property of the compounds containing (Mo_2O_4(C_2O_4)_2(H_2O)_2)~2- anion has been studied~(3,4).     

CRYSTAL AND MOLECULAR STRUCTURE OF 1,10-PHENANTHROLINE TETRACARBONYL CHROMIUM AND -MOLYBDENUM COMPLEXES, (C_(12)H_8N_2)M(GO)_4 (M=Cr and Mo)

<正> The crystal and molecular structures of (C12H8N2)Mo(CO)4 and (C12H8N2)Cr(CO)4 are reported. They crystallize in the space group C2/m and are isomorphous with each other. The unit cell dimensions for (C12H8N2 Cr(CO)4 are a=15.404(2), b=12.091(2), c=8.223(2) A, 3=108.70(2)0, and V=1450.6(9) A3, while for (C12H8N2)Mo(CO)4 are a=15.546(6), b=12.086(4), c=8.269(1.) A, β= 107.37(2)0 and V=1482.9(l.5) A3, and both Z=4. Final R=0.040 Rw=0.050 for (C12H8N2)Cr(CO)4 and R=0.034 Rw=0.053 for (C12H8N2)Mo(CO)4.     

ELECTRONIC EFFECTS OF DONOR AND ACCEPTOR SUBSTITUENTS ON DIPYRIDO(3,2-a:2′,3′-c)PHENAZINE (dppz)

Abstract

The chelate ligands 11-R-dipyrido[3,2-a:2′,3′-c]phenazine, dppz-R (R = NH₂, CH₃, H, COOH, NO₂) and the Re(dppz-R)(CO)₃Cl (R = NH₂, COOH, NO₂) complexes were synthesized and characterized by conventional techniques. The influence of the donor and acceptor properties of the R substituents on the ligand properties were studied by spectroscopic techniques such as ¹H-NMR and UV-Vis. Theoretical calculations were also achieved, mainly to interpret and understand the experimental spectra.