A theoretical investigation of the ground and core hole states of linear and bent NiCO; a prototype for CO adsorbed on nickel

Non-empirical LCAO MO SCF calculations within the Hartree-Fock formalism have been performed on linear and bent conformations of NiCO, for both the states arising from the 3d⁹4s¹ and 3d¹⁰ electronic configurations of Ni, for ground and core ionized species. Binding and relaxation energies are computed for the nickel atom, the free ligand (CO) and the absorbed species (NiCO). Comparison with available experimental data reveals good agreement for the shifts in core binding energies for the bent, 3d⁹4s¹ NiCO system. The main contribution to these binding energy shifts is found to be due to relaxation effects, which may be rationalized in terms of atomic population and bond overlap changes accompanying core ionization.     

The coordination chemistry of simple phospholes. Complexes of rhenium,ruthenium, cobalt,rhodium and iridium chlorides and of some chlorocarbonyls of ruthenium and rhodium

The reactions of 1-phenylphosphole (PP), 3-methyl-1-phenylphosphole (mPP), 3,4-dimethyl-1-phenylphosphole (dPP) and, in certain instances, 1-n-butyl-3,4-dimethylphosphole (dBP) with some transition metal chlorides and some metal-Cl-CO systems are reported. These reactions show that simple phospholes in general unexpectedly behave much like ordinary tertiary phosphines and that, unlike the reactions with Ni(II), Pd(II) and Pt(II), the complexes formed are conventional in most respects. However, a few unusual reactions were observed. For example, mPP partially reduces Ru(III) to give a mixed-valent Ru(III)-Ru(II) complex while PP reduces Ir(III) to Ir(I). From infrared spectroscopic studies of the square-planar Rh(I) complexes L₂Rh(CO) Cl (L = phosphole), it appears that donor character decreases with decreasing substitution on the phosphole ring carbon atoms. Phosphorus-phenyl cleavage has been observed in reactions of 1-phenylphosphole with Rh-CO systems. The results are briefly discussed in relation to the behaviour of other phospholes in similar reactions and in the context of the electronic structure of phospholes.     

Programmable assembly of colloidal particles using magnetic microwell templates

A substrate of thin micromagnets covered by a template of microwells is used to direct the assembly of superparamagnetic colloidal beads into two-dimensional arrays. It is confirmed that the magnetization of the micromagnets can direct beads to programmed locations on the substrate with assistance of externally applied magnetic fields. Empirical investigations on this topic were guided by mathematical models with the intent to elucidate the conditions that promote a single bead to be assembled in the desired microwells. To demonstrate that this technique is programmable, heterogeneous arrays of colored beads are produced.     

Distribution kinetics of Ostwald ripening at large volume fraction and with coalescence

Condensation phase transitions from metastable fluids occur by nucleation with accompanying particle growth and eventual Ostwald ripening. During ripening the subcritical particles dissolve spontaneously while larger particles grow and possibly coalesce if their volume fraction is large enough. The classical diffusion-influenced rates are also affected by large particle concentrations and are here described by mass-dependent rates. We represent the kinetics of ripening through growth, dissolution, and biparticle coalescence by a new population dynamics equation for the particle size distribution (PSD). Numerical solutions of the scaled governing equations show that coalescence plays a major role in influencing the PSD when the scaled mass concentration (volume fraction) or number concentration is relatively large. The solution describes the time range from initial conditions to the final narrowing of polydispersity. We show that the time dependence of the average particle mass in the asymptotic period of ripening has a power-law increase dependent on rate expressions for particle growth and coalescence at large values of volume fraction.     

Stabilities of the C-H...O bonded complexes of the haloforms HCClnF3-n (n = 0-3) with dimethyl ether, oxirane, and acetone: an experimental and theoretical study

Complexation enthalpies of the complexes of the haloforms HCCl(n)F(3-)(n) (n = 0-3) with dimethyl ether, oxirane, and acetone have been determined in liquid krypton and/or liquid argon using infrared spectroscopy. The same quantities were derived starting from ab initio complexation energies, calculated at the MP2=FULL/aug-cc-VTZ level, and by correcting these energies for thermodynamic and solvent contributions. The two sets of data are compared and discussed.     

Micro-X-ray fluorescence as a general high-throughput screening method for catalyst discovery and small molecule recognition

A powerful high-throughput screening technique is described for the rapid screening of bead-based libraries for catalyst discovery and molecular recognition. Micro-X-ray fluorescence (MXRF) screens materials for elemental composition with mesoscale analysis. This method is nondestructive and requires minimal sample preparation and no special tags for analysis, and the screening time is dependent on the desired sensitivity. The speed, sensitivity, and simplicity of MXRF as a high-throughput screening technique were applied to screen bead-based libraries of oligopeptides for phosphate hydrolysis catalysts and molecular recognition of selective receptors for the degradation products and analogues of chemical warfare agents. This paper demonstrates the analytical or HTS capability of MXRF for combinatorial screening. It is meant only to show the capabilities of MXRF and is not meant as an exhaustive study of the catalyst and molecular recognition systems presented.     

Microscopic investigation of iron (III), cobalt (II), and nickel(II) in mixtures

Summary The complex FeI₃·3 C₉H₇N has been verified through topochemical reactions leading to known microcrystalline products. Using the same technique, Fe(III), Co(II), and Ni(II) can be detected in mixtures at concentrations of 1 to 0.01% within an hour.

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Zusammenfassung Die Zusammensetzung des Komplexes FeJ₃ · (C₉H₇N)₃ wurde durch topochemische Kristallfällungsreaktionen erwiesen. In gleicher Weise lassen sich Fe(III), Co(II) und Ni(II) in Konzentrationen zwischen 0,01 und 1% innerhalb 1 Stunde nebeneinander nachweisen.

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Presented at the 8th Pan-American Congress of Pharmacy and Biochemistry, November 30-December 7, 1969, Caracas, Venezuela.     

Magnetic circular dichroism and cobalt(II) binding equilibrium studies of Escherichia coli methionyl aminopeptidase

Equilibrium dialysis of methionyl aminopeptidase from Escherichia coli (EcMetAP) monitored by atomic absorption spectrometry and magnetic circular dichroism (MCD) shows that the enzyme binds up to 1.1 +/- 0.1 equiv of Co(2+) in the metal concentration range likely to be found in vivo. The dissociation constant, K(d), is estimated to be between 2.5 and 4.0 microM. Analysis of the temperature and magnetization behavior of the two major peaks in the MCD spectrum at 495 and 567 nm suggests that these transitions arise from Co(2+) with different ground states. Ligand field calculations using AOMX are used to assign the 495 nm peak to Co(2+) in the 6-coordinate binding site and the 567 nm peak to Co(2+) in the 5-coordinate site. This is further supported by the fact that the binding affinity of the Co(2+) associated with the 567 nm peak is enhanced when the pH is increased from 7.5 to 9.0, consistent with having an imidazole ligand from a histidine amino acid residue. On the basis of the MCD intensities, it is estimated that, when the 5-coordinate site is fully occupied, 0.1 equiv of cobalt is in the 6-coordinate site. Even when the cobalt concentration is very low, there is a small fraction of binuclear sites in EcMetAP formed through cooperative binding between the 5- and 6-coordinate Co(2+) ions. The magnetization behavior of the 6-coordinate Co(2+) MCD peak is consistent with an isolated pseudo-Kramer doublet ground state, suggesting that the cobalt ions in the binuclear sites are not magnetically coupled.     

A novel methodology for the synthesis of complexes containing long carbon chains linking metal centres: molecular structures of [Ru(dppe)Cp*]2(mu-C14) and [Co3(mu-dppm)(CO)7]2(mu3:mu3-C16)

Elimination of AuX(PR3)(X = halogen, R = Ph, tol) occurs readily in reactions between compounds containing C(sp)- or C(sp2)-X bonds and alkynyl or polyynyl gold(I) complexes; this reaction has been applied to the syntheses of complexes containing a variety of metal centres linked by C(n) chains (n up to 16).     

Structural design criteria for anion hosts: strategies for achieving anion shape recognition through the complementary placement of urea donor groups

The arrangement of urea ligands about different shaped anions has been evaluated with electronic structure calculations. Geometries and binding energies are reported for urea complexes with Cl-, NO(3)-, and ClO(4)-. The results yield new insight into the nature of urea-anion interactions and provide structural criteria for the deliberate design of anion selective receptors containing two or more urea donor groups.