The electronic structure and the He (I) photoelectron spectrum of bis(π-pentadienyl)dinickel

The electronic structure of bis(π-pentadienyl)dinickel (1) has been investigated by means of semi-empirical MO calculations of the INDO type and by means of He(I) photoelectron (PE) spectroscopy. The vertical ionization potentials obtained by a Green's function approach are in good agreement with the measured ionization energies. It is demonstrated that the Ni 3d ionization events occur at lower energies than the lowest ligand band, a sequence that differs from the case of bis(π-allyl)nickel (2) where ligand π orbitals are ionized at lower energies than Ni 3d orbitals. This difference between the two π complexes can be traced back to a less efficient metal to ligand charge transfer in the binuclear complex 1 leading to a destabilization of the MOs with large Ni 3d amplitudes. According to the semi-empirical INDO-hamiltonian the direct interaction between the two 3d manifolds in the closed shell ground state of 1 is small.     

Synthesis and crystal structure of a silver(I) 6-methylmercaptopurine riboside complex

Silver nitrate reacts with 6-methylmercaptopurine riboside (6-MMPR) in aqueous solution containing methanol and dimethyl sulfoxide at room temperature to give a colourless crystalline complex, namely, bis(6-methylmercaptopurine riboside-κN⁷)(nitrato-κ²O,O′)silver(I) 2.32-hydrate, [Ag(NO₃)(C₁₁H₁₄N₄O₄S)₂]·2.32H₂O. The crystal structure, determined from synchrotron diffraction data, shows a central Ag^I ion on a crystallographic twofold rotation axis, coordinated in an almost linear fashion by two 6-MMPR ligands via atom N7 (purine numbering), with the nitrate counter-ion loosely coordinated as a bidentate ligand, forming a discrete molecular complex as an approximate dihydrate. The complex and water molecules are connected in a three-dimensional network by hydrogen bonding.     

The crystal structure of silver(I) 2,4,5-trichlorophenolate

The crystal structure of silver(I) 2,4,5-trichlorophenolate has been determined by X-ray diffraction and refined to a residual R = 0.031 for 1072 observed reflections. Crystals are orthorhombic, space group Pccn with 8 molecules in a cell of dimensions, a 11.455(4), b 23.75(1), c 5.645(1) Å. Each silver in the polymeric structure is bonded to three independent phenolate oxygens (Ag  O range, 2.317-2543(3) Å; OAgO range, 86.5–106.5(2)°). In addition there is an unusual symmetrical and directed phenyl carbon-silver bond (AgC, 2.443(5) Å) that completes a trigonal pyramidal stereochemistry about silver.     

The electronic spectrum of the triethylamine-perfluoro-tert-butanol complex

The far-ultraviolet absorption spectrum of the triethylamine-perfluoro-tert-butanol complex has been measured in the gas phase. The photoelectron band of lowest energy has also been determined. It is about 13000 cm^?1 higher than for free triethylamine. Up to at least 60000 cm^?1, the UV spectrum is readily interpreted as a triethylamine spectrum shifted to higher frequencies by about 13000 cm^?1. The bands of lowest frequency are the 3s and 3p Rydberg bands which follow the ionization potential. Up to 60000 cm^?1, no charge transfer type band has been found.     

The electronic structure and spectrum of Mo(CN)8(3-)

State of the art CASSCF and CASPT2 calculations have been performed to elucidate the nature of the electronic transitions observed in the experimental spectrum of the octacyanomolybdate(V) cation. Assuming a triangular dodecahedral structure for this complex gives a convincing agreement between theory and experiment. All absorption bands are assigned to low-lying charge-transfer transitions involving excitations from ligand orbitals to 4dx2-y2. The calculated molecular orbitals reveal weak pi interactions between the metal and ligand orbitals, compared to much stronger sigma interactions. This calculated electronic structure substantiates the previous hypothesis concerning the giant spin ground states of magnetic clusters and networks containing Mo(CN)8(3-) as a constituent part.     

The electronic structure of the aqua-oxo complex of vanadium(IV)

The Jorgensen [16] and Ros-Cotton [9, 10] methods have been used to calculate the electronic structure of VO(OH₂) ₅ ²⁺ . The results are compared with those obtained from the simple Wolfsberg-Helmholz method and with the electronic absorption spectra. Good agreement with the experimental data is obtained in the latter case. When calculating the transition energies associated with charge transfer, we took into account the interaction of an excited electron with the effective charges in the complex and the redistribution of these charges when the excited state is populated.     

The electronic spectrum and electronic structure of 1,5 dinitronaphthialene

The electronic absorption spectra of the n-heptane and ethanol solutions and the polarized absorption spectrum of the single crystal were measured with 1,5-dinitronaphthalene. 1,5-Dinitronaphthalene shows three absorption bands at 198.7, 230 and 323 m. The 230 m and 323 m. bands are polarized almost parallel with the long and short axes of the naphthalene ring respectively. The assignment of the bands has been made by combining the observed results with the theoretical consideration.

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Zusammenfassung Das UV-Absorptionsspektrum von 1,5-Dinitronaphthalin in Lösung von n-Heptan und Äthanol und das Polarisationsabsorptionsspektrum des Einkristalls wurde aufgenommen. Es zeigt drei Banden bei 198,7, 230 und 323 m, wobei die Polarisationsrichtungen der beiden letzteren nahezu parallel zur langen und kurzen Achse des Naphthalinringes liegen. Die Zuordnung der Banden wurde auf Grund einer Kombination experimenteller und theoretischer Gegebenheiten vorgenommen.

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Résumé Le spectre électronique d'absorption du 1,5-dinitronaphthalène a été mesuré dans l'éthanol, le n-heptane et dans le monocristal. Des bandes à 198,7, 230 et 323 m la deuxième (troisième) est polarisée presque parallèle à l'axe longue (courte) du noyau naphthalénique. La comparison aux résultats théoriques permet l'interprétation des bandes.

     

Molecular and electronic structure, magnetotropicity and absorption spectra of benzene-trinuclear copper(I) and silver(I) trihalide columnar binary stacks

The molecular and electronic structures, stabilities, bonding features, magnetotropicity and absorption spectra of benzene-trinuclear Cu(I) and Ag(I) trihalide columnar binary stacks with the general formula [c-M(3)(μ(2)-X)(3)](n)(C(6)H(6))(m) (M = Cu, Ag; X = halide; n, m ≤ 2) have been investigated by means of electronic structure calculation methods. The interaction of c-M(3)(μ(2)-X)(3) clusters with one and two benzene molecules yields 1:1 and 1:2 binary stacks, while benzene sandwiched 2:1 stacks are formed upon interaction of two c-M(3)(μ(2)-X)(3) clusters with one benzene molecule. In all binary stacks the plane of the alternating c-M(3)(μ(2)-X)(3) and benzene components adopts an almost parallel orientation. The separation distance between the centroids of the benzene and the proximal c-M(3)(μ(2)-X)(3) metallic cluster found in the range 2.97-3.33 ? at the B97D/Def2-TZVP level is indicative of a π···π stacking interaction mode, for the centroid separation distance is very close to the sum of the van der Waals radii of Cu···C (3.10 ?) and Ag···C (3.44 ?). Energy decomposition analysis (EDA) at the SSB-D/TZP level revealed that the dominant term in the c-M(3)(μ(2)-X)(3)···C(6)H(6) interaction arises from dispersion and electrostatic forces while the covalent interactions are predicted to be negligible. On the other hand, charge decomposition analysis (CDA) illustrated very small charge transfer from C(6)H(6) toward the c-M(3)(μ(2)-X)(3) clusters, thus reflecting weak π-base/π-acid interactions which are further corroborated by the respective electrostatic potentials and the fact that the total dipole moment vector points to the center of the metallic ring of the c-M(3)(μ(2)-X)(3) cluster. The absorption spectra of all aromatic columnar binary stacks simulated by means of TD-DFT calculations showed strong absorptions in the UV region. The main features of the simulated absorption spectra are thoroughly analyzed, and assignments of the contributing electronic transitions are given. The magnetotropicity of the binary stacks evaluated by the NICS(zz)-scan curves indicated an enhancement of the diatropicity of the inorganic ring upon interaction with the aromatic benzene molecule. Noteworthy is the slight enhancement of the diatropicity of the benzene ring, particularly in the region between the interacting rings, probably due to the superposition (coupling) of the diamagnetic ring currents of the interacting aromatic ring systems.     

The electronic structure and spectrum of tropone

The electronic structure and spectrum of tropone were studied by paying special attention to an assignment of the 300 m band. The band was shown to have a single ^* character overlapped by an n ^* transition from the following experimental and theoretical studies: (i) From the comparison of the observed transition energies and intensities with theoretical values obtained by the Pariser-Parr-Pople calculation in which the values of W _X ^2p (valence state ionization potential of the oxygen atom) and k (bond alternation parameter) taken as guiding parameters were changed widely and their adequateness was carefully examined, (ii) From the correlation among the electronic absorption spectra of tropone, troponeimine, and heptafulvene. (iii) From the finding that the 300 m band increases its intensity with the increasing polarity of the solvent. (iv) From the position and intensity of a band newly observed in the vacuum ultraviolet region.

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Zusammenfassung An Tropon wurden Elektronenstruktur und Spektrum untersucht, speziell die 300 m-Bande. Diese entsteht aus einem einzigen - ^*-Übergang, überlagert von einer schwachen n-^*-Bande, und nicht aus 2 - ^*-Banden. Als Stütze dienen: 1. eine PPP-Rechnung, bei der das Valenzzustandsionisationspotential von Sauerstoff und der Bindungsalternierungsparameter sorgfältig variiert wurden, 2. die Korrelation der Spektren von Tropon, Troponimin und Heptafulven, 3. der Lösungsmitteleinfluß auf die Bande, 4. eine neuaufgefundene UV-Bande.

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Résumé La structure électronique et le spectre de la tropolone ont été étudiés en accordant une attention particulière à l'identification de la bande à 300 m. Cette bande a été caractérisée comme résultant d'une transition ^* recouverte par une transition n ^*, à l'aide des arguments théoriques et expérimentaux suivants: 1. à partir de la comparaison des énergies et des intensités de transition observées, avec les valeurs théoriques obtenues par un calcul Pariser-Parr-Pople où les valeurs de W _X ^2p (potentiel d'ionisation de l'état de valence de l'atome d'oxygène) et de k (paramètre d'alternance des liaisons), considérés comme paramètres régulateurs, ont été largement variées et soigneusement analysées. 2. à partir de la corrélation entre les spectres d'absorption électronique de la tropolone, de la tropolonéimine et de l'heptafulène. 3. à partir du fait que la bande à 300 m voit son intensité croitre avec la polarité du solvent. 4. à partir de la position et de l'intensité d'une bande nouvelle observée dans la région de l'ultra-violet lointain.

     

Formation of uniform silver particles from bis (1,2-ethanediamine)silver(I) complex

Uniform spherical silver particles were produced by decomposing the bis(1,2-ethanediamine)silver(I) complex, by aging a solution of 1.0×10^–3 mole dm^–3 in silver (I) nitrate, 1.0 mole dm^–3 in 1,2-ethanediamine, and 2.5×10^–1 mole dm^–3 in nitric acid (basic solution) at 100°C for 42 min. The average modal diameter was estimated to be 0.52 m with a relative standard deviation of 0.10. A moderately oxygenrich layer, 40 Å thick, on the surface of the particles was detected by means of photoelectron surface microanalysis (XPS). The silver particles grew through a polynuclear-layer mechanism, as judged from the concentration change in soluble silver(I) species in the supernatant solution. The particles' point of zero charge (PZC) was estimated at pH 6.5 by potentiometric titration.     

1D silver(I) complex of nitronyl nitroxide with strong spin-spin interaction through silver(I) ion

A 1D silver(I) complex of nitronyl nitroxide was prepared and its structure was determined by X-ray diffraction analysis; magnetic studies indicate that the spin-spin interaction of nitronyl nitroxides through silver(I) ions along the chain are fairly strong (J/kb = -84 K).     

A novel organometallic columnar complex containing endohedral silver(I)-ethynediyl binding and exterior silver(I)-aromatic interaction

Unprecedented eta 3 pi-donor behavior of the benzyltrimethy-lammonium ion is observed in the polymeric silver(I) complex [(PhCH2NMe3)Ag7(C2)(CF3CO2)6]n that comprises a columnar backbone constructed from the fusion of Ag8 square antiprisms each enclosing an acetylide dianion.     

High-resolution electronic spectrum of the p-difluorobenzene-water complex: structure and internal rotation dynamics

The rotationally resolved S(1) <-- S(0) electronic spectrum of the water complex of p-difluorobenzene (pDFB) has been observed in the collision-free environment of a molecular beam. Analyses of these data show that water forms a planar sigma-bonded complex with pDFB via two points of attachment, a stronger F---H-O hydrogen bond and weaker H---O-H hydrogen bond, involving an ortho hydrogen atom of the ring. Despite the apparent rigidity of this structure, the water molecule also is observed to move within the complex, leading to a splitting of the spectrum into two tunneling subbands. Analyses of these data show that this motion is a combined inversion-internal rotation of the attached water, analogous to the "acceptor-switching" motion in the water dimer. The barriers to this motion are significantly different in the two electronic states owing to changes in the relative strengths of the two hydrogen bonds that hold the complex together.     

Theoretical study of the electronic spectrum of binuclear gold(I) complexes

The electronic structure and the spectroscopic properties of [Au₂(CS₃)₂]^?2, [Au₂(pym‐2‐S)₂] (pym = pyrimidethiolate), [Au₂(dpm)₂]⁺² (dpm = bis(diphosphino)methane) were studied using density functional theory (DFT) at the B3LYP level. The absorption spectrum of these binuclear gold(I) complexes was calculated by single excitation time‐dependent (TD) method. All complexes showed a ¹(5dσ* → 6pσ) transition associated with a metal–metal charge transfer, which is strongly interrelated with the gold–gold distance. Furthermore, we have calculated the frequency of the gold–gold vibration (ν_Au2) on the above complexes. The values obtained are theoretically in agreement with experimental range. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Crystal structure of mixed-ligand silver(I) hydrogen iminodiacetate

The crystal structure of mixed-ligand silver(I) hydrogen iminodiacetate has been studied. The composition of the [Ag₂(C₄H₆NO₄)(NO₃)(H₂O)] _n ([Ag₂(HIda)(NO₃)(H₂O)] _n ) coordination polymer has been refined. The NO₃ and H₂O ligands in the complex form rather weak coordination bonds with the Ag atoms. The system of hydrogen bonds in the structure has been considered. The formation of a chain of hydrogen bonds between the disordered H₂O molecules was established.     

Synthesis, crystal structure, and luminescent properties of a silver(I) perrhenate complex with phenazine

The silver complex with phenazine [Ag(Phz)₂(H₂O)]ReO₄ (Phz is C₁₂H₈N₂) has been synthesized, and its crystal structure has been determined. The crystals are triclinic: space group $P\bar 1$ , a = 9.587(1) Å, b = 10.875(1) Å, c = 11.668(1) Å, α = 104.98(1)°, β = 103.87(1)°, γ = 92.94(1)°, V = 1132.6(2) ų, Z = 2, ρ_calc = 2.160 g/cm³. The structure is composed of the [Ag(Phz)₂(H₂O)]⁺ silver cationic complexes and ReO ₄ ^? anions. The Ag⁺ ion is coordinated by two nitrogen atoms of independent phenazine molecules and the water oxygen atoms and has a T-shaped coordination (Ag-N_av 2.223 Å, Ag-O_w 2.498(8) Å). Phenazine, being an electron-donor ligand, forms columns due to π-π stacking interaction between the aromatic groups. The water molecules form hydrogen bonds with the oxygen atoms of water molecules of neighboring complexes and with oxygen atoms of the ReO ₄ ^? anions.     

Synthesis,crystal structure and ferromagnetic interactions of a silver(I) complex with imizadolyl-substituted nitroxide radicals

A silver(I) complex with nitronyl nitroxide, [Ag₂(NIT-R)₄(NO₃)₂]?·?CH₃OH [NIT-R?=?2-(5-methylimidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl-3-oxide], has been prepared and characterized by magnetic and single-crystal X-ray diffraction studies. In the complex, the silver(I) ion is coordinated with two monodentate nitronyl nitroxide radicals by the nitrogen of the imizadole ring. The silver(I) ion is two-coordinate and forms a dimer through Ag?···?Ag weak metal bonding interactions. The magnetic properties for the title complex have been investigated in the temperature range 2?～?300?K showing ferromagnetic interactions between the coordinated nitronyl nitroxides (J?=?3.64?cm^?1) and intermolecular antiferromagnetic interactions.