Ligand field spectra splitting parameter

V02+ is nearly as great as that of the hg- eg excitation in Ti(OH2)63+ [9, 10] emphasizes the importance of VO 71-bonding. The shoulder at 16,000 cm-1 arises from the 2B2(xy) —> 2Bi(x2 — y2) transition and provides a direct estimate of the octahedral ligand field splitting parameter (lODq). For comparison, lODq values for the V2+ [10,11] and V3+ [10,12-14] hexaaqua ions are estimated to be -12,000 and 18,800 cm-1, respectively. The absorption spectrum reveals that the strength of the V-OH2(equatoriai) interaction in the vanadyl ion lies somewhere between that of V2+ and V3+. 

In Sect. II we give a brief survey of experimental and theoretical studies of copper(11) spectra. In Sect. Ill the various theoretical models are critically assessed, and in Sect. IV we present tabulations of the parameters required for calculations of ligand field splittings of the type advocated in our recent publications. These should enable the reader to calculate the d—d spectrum of any copper(II) complex of known (or suspected) geometry. 

The Mossbauer spectrum of compound (29) shows it to contain two iron environments, and comparison of the parameters with the other data suggests that the dimeric unit contains one 5-coordinated and one 6-coordinated iron atom. The neutral monomers (31) and (32) are equivalent to the penta-coordinated monoanions with an electron removed, possibly from a ligand-based orbital. A ligand-field treatment for the temperature dependence of the quadrupole splitting in some of these complexes has been suggested [33]. 

To study the effect on the electronic spectrum of replacing water as a ligand by ammonia, prepare a 1 M solution of Cu(ll) nitrate in water. Dilute 1 cm of the solution with either water or cone, ammonia make up to 100 cm and record the spectra in a 1 cm cell over the range 400-800 nm. Mix an equal volume of the nitrate solution with cone, ammonia and record the spectrum as above. Calculate the ligand field splitting parameter from the wavelengths of maximum absorption. Comment on your results. 

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