Luminescence Spectra of Transition-Metal Complexes
Photoexcited luminescence spectra of transition metal complexes have been reported until now in the literature in several instances, some of which (e. g. Cr3+ in ruby (1) and in other complexes (2)) have acquired major importance in the elucidation of the
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k '3d
= ---I +
cl
where D and tw represent the optical density of the maximum and the halfwidth of the bands, and k the angular non -diagonal matrix elements for dfunctions given by GRiFFITH (4). The sub-indices refer to the levels essentially spin -doublets and quartets, respectively, and the summation should be carried out over the two r components of the quartet level, the factor ~ occurring because only ~ of the quartet level is acting in each case. The result for '3d is 185 cm -1 which in view of the standard deviation on the parameters of 2E should be good to about 300/0. Other implications from the properties of gaussians on the observability of spUt components caused by low symmetry will be discussed. Also the significance of such considerations in interpreting polarized spectra and circular dichroism curves will be stressed. Acknowledgement. The author is much indebted to Dr. ERIK J4'RGENSEN in particular for his philosophy of experiment and its numerical analysis (5). References 1. MEAD, A., Trans.Faraday Soc., 30, 1055 (1934). 2. J4'RGENSEN, C. K., Acta Chem. Scand., ~, 1495 (1954). 3. SCHÄFFER, C.E., Symposium on the Structure and Properties of Coordination Compounds. Bratislava, September 1964. 4. GRIFFITH, J.S., The Theory of Transition Metal Ions. Cambridge University Press. 1961. 5. J4'RGENSEN, E., Framework program far non-linear regression analysis with tests. Danish Institute of Computing Machinery. November 1963.
LUMINESCENCE SPECTRA OF TRANSITION-METAL COMPLEXES.
8 A 2
V. Caglioti, G. Sartori and C. Furlani Istituto Chimico, Universita di Roma, Italy. Photoexcited luminescence spectra of transition metal complexes have been reported until now in the literature in several instances, so me of wh ich (e.g. Cr3+ in ruby (1) and in other complexes (2) ) have acquired major importance in the elucidation of the symmetry type and of the electronic structure of coordination compounds; other literature reports include V. Gutmann (ed.), Proceedings of the 8th International Conference on Coordination Chemistry © Springer-Verlag Wien 1964
- 82 Mn2+ (3) and Mn 3+ ( 4). We shall report here the results of a systematic investigation of i" ... 8 electronic spectra in photoexcited luminescence; although a study of absorption spectra leads in principle to the knowledge of the same system of dn -energy levels as the study of emission spectra. the latter technique can be sometimes superior to the former one in detecting spin -forbidden transitions (since longer 1i ved excited states are more apt to fluoresce). despite instrumental drawbacks (such as the dependence of emission intensities on both source intensity and frequency). and the need for further improvements in the instrumentation. Also. comparison of energy levels inferred from absorption and from luminescence spectra. which differ slightly because of different vibronic levels implied. supplies more informations about vibronic coupling, Franck-Condon mechanisms, Morse curves. and possibility of nonradiative transitions, than could be deduced from ab
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