ISSN:
0020-7608
Keywords:
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The oscillator strengths f1, f2, and f3 corresponding to the three allowed 2eu, → 3b1g, 3eu → 3b1g, and 1b2u → 3b1g charge-transfer transitions of the D4h CuCl2-4 -complex together with their dependence on the metal-ligand distance R are investigated using the self-consistent charge extended Hückel (SCCEH) and MSXα methods. The main conclusions of this work are the following: (1) f1 and f2 directly reflect the σ-character displayed by 2eu and 3eu orbitals. When this character is suppressed, f1 and f2 decrease by an order of magnitude and then become comparable to f3. This trend concurs with experimental findings. (2) The different σ-character exhibited by 2eu and 3eu orbitals arises mainly from the 4p(Cu) admixture. A similar one involving the 3s(Cl) orbitals plays a minor role. When such admixtures are neglected, the two wave functions |2eu〉 and |3eu〉 can simply be written as |σ〉 + |π〉 and |σ〉 - |π〉, respectively. The inclusion of 4p(Cu), although small, produces an interference between |σ〉 + |π〉 and |σ〉 - |π〉, enhancing the σ-character in 2eu and destroying it in 3eu. This explains well the asymmetry between f1 and f2 observed experimentally. (3) The σ-character in 2eu and 3eu together with f1 and f2 are found to be nearly independent upon R. (4) Also, the separation, Δ, between the energies of the 2eu → 3b1g and 3eu → 3b1g transitions was explored. It is shown that Δ is determined mainly by the ligand-ligand interaction and, thus, is strongly dependent upon R. © 1997 John Wiley & Sons, Inc.
Additional Material:
3 Ill.
Type of Medium:
Electronic Resource
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