Optical rotatory power of co-ordination compounds. Part XVIII. The circular dichroism of trigonal nickel(II) chelate complexes
- 1 January 1973
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 9,p. 955-960
- https://doi.org/10.1039/dt9730000955
Abstract
The axial circular dichroism spectrum of [Ni(en)3]2+ in the hexagonal host crystal, [Zn(en)3](NO3)2,6H2O, has been measured, together with the solution c.d. spectra of tris-1,2-diamine and tris-1,2-di-imine complexes of nickel(II). The results show that the spin-allowed octahedral transition of nickel(II) with the lowest energy, 3A2g→3T2g, is allowed for magnetic dipole radiation and breaks down in tris-1,2-diamine complexes with the Δ-configuration into a lower-energy doubly-degenerate component with a negative rotational strength and a higher-energy non-degenerate component with a positive rotational strength, like the corresponding transition in the analogous complexes of d3 and low-spin d6 transition-metal ions. The similarities between the d3, d6, and d8 cases are found to extend to the c.d. absorption of the second d-electron transition and of the u.v. charge-transfer transition. The complex [Ni(tren-py3)]2+{tren-py3= tris-[4-(2-pyridyl)-3-azabut-3-enyl]amine} has been resolved and the Δ-configuration is tentatively assigned to the (–)-isomer from its c.d. spectrum.Keywords
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