Water crystal field splitting

The effect of crystal field splitting is easily seen by studying the absorption spectrum of [Ti(H20)6]3+ because the Ti3+ ion has a single electron in the 3d orbitals. In the octahedral field produced by the six water molecules, the 3d orbitals are split in energy as shown in Figure 17.3. The only transition possible is promotion of the electron from an orbital in the t2g set to one in the eg set. This transition... 

The [Ti(NCS)g]3- ion exhibits a single absorption band at 544 nm. Calculate the crystal field splitting energy A (in kj/mol). Is NCS- a stronger or weaker field ligand than water Predict the color of [Ti(NCS)6]3-. 

Aqua ions are prototypes illustrating the solution properties of complexes in a particular oxidation state. The properties displayed generally reflect size, charge, and effects such as crystal field splitting, as well as the tendency to form polynuclear oxo/hydroxo-bridged species, and metal-metal bonded species. Residence times of water ligands on aqua ions across the periodic table cover a remarkable 20 orders of magnitude from the most labile (<1 ns) to the most inert (>300 years), which is an important feature to understand. 

Classified as a ligand for metal ions, water has decent crystal field splitting properties, standing between oxygen-bound anions and nitrogen donors such as pyri-dines in the spectrochemical series ... 

The absence of crystal field splitting and the shielding of the / orbitals makes classical molecular dynamics (MD) simulations feasible. Hence, for solvents without covalent bonding like water, ion-solvent forces can be well represented by simple Coulomb and van der Waals terms. The polarization of water molecules in the first coordination shell due to the strong electric field of the trivalent ions has... 

Values of the crystal field splitting parameters A or QDq are listed in Table 8. These give a good idea of relative strengths of ion-water interactions they are available from solution transmission spectra and from diffuse reflectance spectra for solids containing [M(OH2) J" complex cations. The greater interaction with than with and with second-row M " than with first-row as well as the dependence on d electron configuration and spin all accord satisfactorily with crystal field theory. 

The conditional stability constants (log K<.) obtained for copper with humic compounds extracted from soils and natural waters are invariably greater than those for other transition metals (see Table IV). This is expected from the enhanced levels of crystal field stabilisation energy which result fi-om the splitting of the 3d electronic orbitals on Cu by an octahedral field (Mackay and Mackay, 1969). The divei ence in the values of log Kc shown in Table IV, may, in part, have arisen from intrinsic variations in the copper-binding properties of the various humic samples. However, these deviations may also be explained in terms of the different experimental conditions employed (pH, ionic strength, temperature, for example) and the assumptions made in the calculations. For example, an increase in the pH will enhance the availability of dissociated binding sites (see Section 6) which are then free to participate in further complexation of copper and... 

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