http://nova.newcastle.edu.au/vital/access/services/Feed ${session.getAttribute("locale")} 5 http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3189 Transition metal complexes with 2,4-substituted tetradentate, 2,3,4- and 2,4,7-substituted pentadentate, and 2,3,4,7-substituted hexadentate bispidine ligands (bispidine) 7-diazabicyclo[3.3.1]nonane) with two tertiary amine and two, three, or four pyridine donors are relatively stable (10 < log KCUL < 18). Interestingly, the two isomeric pentadentate ligands have very different stabilities with a variety of metal ions and, depending on the metal ion, one of the isomers leads to more stable complexes than the hexadentate and the other to less stable complexes than the tetradentate ligand. Another interesting observation is that the complex stabilities of all bispidine ligands reported here do not follow the Iriving-Williams series since the stability constants of the cobalt(II) complexes are up to 4 log units larger than those of the corresponding nickel(II) complexes. All these observations are analyzed on the basis of subtle distortions of the coordination geometries, and these have been related previously to Jahn-Tellerderived distortions for the copper(II) complexes. However, similar but less pronounced structural properties are observed with other metal centers, as shown, e.g., with the experimental structures of the two zinc(II) complexes with the isomeric pentadentate ligands reported here. The structural properties and the related stabilities are also discussed on the basis of force field calculations. 2010-04-27T05:24:34.249Z ]]> http://nova.newcastle.edu.au/vital/access/manager/Repository/uon:3217 The protonation and Ni(II) complexation of 4-(2-pyridylazo) resorcinol (PAR) in ionic strength 0.1 mol L⁻¹ KNO₃ at 25 ℃ has been studied by global analysis. In spectrophotometric titrations, linear or near-linear dependence of concentration profiles and the existence of minor species can cause difficulties in the evaluation of the data. Both calculated absorption spectra and the corresponding equilibrium constants are not or only poorly defined. The result is the inability to reliably fit a reasonable model to the data. In second order global analysis, a number of spectrophotometric titrations with different initial concentrations are simultaneously analyzed. In this way, conditions for the significant formation of all species can be obtained and consequently the concentration matrix is augmented to full rank. EQUISPEC is a computer program using the matrix based MATLAB environment for second order global analysis of spectrophotometric equilibrium data. The spectrophotometric titrations were carried out at least in four different metal to ligand ratios. 2010-04-27T04:53:18.121Z ]]>