Stephen P. Roe

An x-ray photoelectron spectroscopic study of some nickel(II) amine complexes

Abstract The X-ray photoelectron (XPS) spectra of several Ni(II) diamine complexes, a Ni(II) triamine complex and several Ni(II) diimine complexes are reported in terms of the Ni 2p, Cl 2p and N 1s core level binding energies. Theoretical models are presented to account for the quadratic relationship observed between XPS Ni 2p 3 2 binding energy shifts and the N-H infrared rocking frequency as related to these complexes. On the basis of this correlation, it is possible to discriminate between free counter-ions coordinated to the metal or involved in cluster-ion formation. Individual XPS data for these complexes are interpreted in terms of the intrinsic nature of the metal environment and an attempt is made to calculate the metal and donor nitrogen atomic charges for selected complexes.

AN INFRARED AND ELECTRONIC SPECTROSCOPIC STUDY OF A SERIES OF NICKEL(II) AMINE COMPLEXES

SummaryQualitative infrared and electronic spectroscopic data for a series of nickel(II) amine complexes suggest structures involving octahedral (transtetragonal) symmetry and associated with varying degrees of cation-anion interaction. N-methyl ligand substituents contribute significantly to ligand conformations, complex symmetry, and cation-anion steric interactions. From the electronic data, the parametersDq,B′,C,C/B′, β35, andZ* are determined for each complex and a spectrochemical and nephelauxetic series is proposed for the associated amine ligands.ZusammenfassungDie qualitative Auswertung von Daten aus Infrarot- und Elektronenspektroskopie von Nickel(II)-Amin-Komplexen erlaubte die Zuordnung einer oktaedrischen (trans-tetragonalen) Symmetrie mit verschieden abgestuften Kation-Anion-Wechselwirkungen. Substituenten am N-Methyl-Liganden tragen signifikant zur Ligandenkonformation, Komplexsymmetrie und Kation-Anion-Wechselwirkung bei. Aus den elektronenspektroskopischen Daten wurden die ParameterDq,B′,C,C/B′, β35 undZ* für jeden Komplex bestimmt und als Kriterium für eine Reihung der Aminliganden herangezogen.

An X-ray photoelectron and infrared spectroscopic study of nickel squarate dihydrate and bis(2,4-pentanedionato) nickel(II)

Abstract The X-ray photoelectron spectra of nickel squarate dihydrate and of bis(2,4-pentanedionato)nickel(II) are interpreted in terms of the known crystal structures of these complexes. The comparative degree of pielectron delocalisation over metal and ligand for these complexes is also evaluated from the XPS data.

An X-ray photoelectron spectroscopic study of some copper(II) tetraaza complexes

Abstract A selected series of copper(II) tetraaza complexes, involving open-chain and macrocyclic ligands, has been studied by X-ray photoelectron spectroscopy. The binding energy data obtained are interpreted in terms of the structures of these complexes with particular reference to the existence of π-electron delocalisation over metal and ligand, peripheral ring substituents, cation-anion interaction and hydration water. It is apparent that the degree of cation-anion interaction and photoreduction is a function of the existing experimental conditions.

An X-ray photoelectron spectroscopic study of some bis(diamine)-copper (II) complexes

Abstract XPS data for a series of octahedral copper(II) diamine tetrafluoroborate and perchlorate complexes are interpreted in the following terms; (i) the inductive effect of diamine substituents; (ii) the degree of cation-anion interaction; (iii) the effect of progressive increase in diamine chelate ring size; and (iv) the Jahn-Teller effect in these complexes.

An x-ray photoelectron spectroscopic study of some nickel(II) tetraaza macrocyclic complexes

SummaryX-ray photoelectron spectra (XPS) of the Ni(2 p3/2, 1/2), N(1s) and Cl(2p) core levels for seven nickel(II) tetraaza macrocyclic complexes and three related macrocycles of the basic cyclam and corrin ring structures are reported. Relative satellite intensities for the Ni(2p3/2) level are also reported, where observed. The binding energy data for the core levels are interpreted in terms of structural features of these complexes, such as: (i) the conformation of the macrocyclic ring and the concomitant isomerism possibilities, (ii) the existence of “cluster-ions”, formed as a consequence of hydrogen bonding between macrocyclic cation and counter-ion, and (iii) the coordination number of nickel in these complexes. Additional information of chemical significance, which is derived from the binding energy data, concerns the magnetic properties of the complexes and an estimate of the degree of metal-ligand covalency.

X-ray photoelectron spectroscopy and infrared adsorption spectroscopy - correlations

Abstract Since the early seventies, a correlation has been known to exist between changes in intramolecular bond vibrational frequencies (as measured by IAS) and core level binding energy shifts (as measured by XPS). It is possible to explain such correlations by relating both shifts to the partial atomic charges which exist on the bonding pair of atoms. For a series of related molecules, for example, the charge on a common atom may vary and may be related to the core level shifts on that atom. Equally, Liesegang and Lee have shown that changes in this charge correspond with variations to the bond stretching frequency. This model has also been recently extended to include correlations between XPS shifts and rocking vibrational mode variations. In both applications, however, the elastic properties of bonds (springs) are considered. In the former, spring stretching properties are linked to the partial charges, while in the latter case molecular flexing involving a cantilever-like vibration permits a link with partial charges and their effect on rocking frequency. Experimental data will be presented for comparative purposes to illustrate the predictions of the model.

Electrochemical and spectroscopic studies on some pyridyl and morpholyl adducts of (meso-tetraphenylporphyrin)chromium(III) chloride

The electrochemical behaviour of the adducts Cr(TPP)·Cl·L, whereTPP = tetraphenylporphyrin;L = pyridine, 2-picoline, 2,6-lutidine, 4-cyanopyridine, morpholine or 4-picoline is reported and the relationship between reduction potentials, the electron band I transition and the binding energy of the Cr2p3/2 level examined.Based on criteria for the differences in oxidation potentials determined in acetonitrile by cyclic voltammetry and reduction potentials determined inDMSO, it is concluded that the adducts behave as normal metalloporphyrins. Further, variations for the different adducts are attributed primarily to different inductive effects from the heterocyclic axial groups. The adduct formed from 2,6-lutidine, however, shows anomalous behaviour which is attributed to a marked steric effect between the ligand and the porphinato-nitrogen atoms.

Correlation of x-ray photoelectron spectroscopic core level binding energies with melting point for a series of diamine dihydrochlorides

X-ray photoelectron spectroscopic (XPS) and differential thermal analysis (DTA) studies of a series of diamine dihydrochlorides have shown that a linear relationship exists between the N(1 s) and Cl(2p3/2) binding energy shifts and the melting points of these salts. A theoretical model is presented to verify this empirical correlation. It is apparent that such binding energy shifts and melting points are also dependent upon intrinsic electronic and bonding features of these salts such as quaternary nitrogen substituent inductive effects, charge delocalisation within the cation, cation-anion interaction and salt hydration.

Synthesis and characterisation of some novel β-aminodiketones

The synthesis and characterisation of five newβ-aminodiketones is reported: (a) 3,3,5,8,10,10-hexamethyl-5,8-diazadodecane-2,11-dione; (b) 3,3,11,11-tetramethyl-5,8-diazatridecane-2,12-dione; (c) 3,3,12,12-tetramethyl-5,10-diazatetradecane-2,13-dione; (d) 3,3,10,10-tetramethyl-5,8-diphenyl-5,8-diazadodecane-2,11,dione and (e) 6,7-benzo-3,3,10,10-tetramethyl-5,8-diazadodecane-2,11-dione. These compounds are discussed as potential precursors in the synthesis of tetra-aza macrocyclic complexes.