POLARIZED CRYSTAL SPECTRA OF TRIS (ETHYLENEDIAMINE) CHROMIUM (III) ION

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Title: POLARIZED CRYSTAL SPECTRA OF TRIS (ETHYLENEDIAMINE) CHROMIUM (III) ION
Creators: Vala, Martin; McCarthy, P. J.
Issue Date: 1972
Publisher: Ohio State University
Abstract: The low temperature single crystal polarized spectra of the $Cr(en)_{3}$ $^{3+}$ complex [$en = $ethylenediamine] in two crystals, $$2[Cr(en)_{3}]C\ell_{3} \cdot KC\ell \cdot 6H_{2}O (I)\ and\ [Cr(en)_{3}]C\ell_{3} \cdot 3.5H_{2}O (II)$$ are presented. Transitions to the spin-forbidden $^{2}E$, $^{2}T_{1}$, and $^{2}T_{2}$ states and the spin-allowed $^{4}T_{2}$ and $^{4}T_{1}$ states have been observed and analyzed. An interference effect has been noted between the sharp $^{2}T_{2}$ state and the broad continuum-like $^{4}T_{2}$ state. The spin-orbit-trigonal field components of the $^{2}E$ and $^{2}T_{1}$ states have been experimentally determined, and theoretically justified via a complete crystal field-spin orbit calculation. The $R_{1}$ and $R_{2}$ lines in crystal I are shown to have different linewidths at 1.6$^{\circ} K$; this is ascribed to a lifetime broadening process for which the radiationless transition rate has been calculated. The much broader line-widths observed in crystal II are the result of random Stark fields from the statistically absent waters of hydration. Satellite bands are observed around the $R_{1}$ and $R_{2}$ lines in crystal I at 1.6$^{\circ} K$. It is suggested that they result from different conformations of the ethylenediamine ligands which are stabilized by hydrogen-bonding in the crystal. Both the emission spectrum and the temperature dependence of the $R_{1}$ and $R_{2}$ absorption lines point to a ground state phonon mode of $\sim 19$ $cm^{-1}$.
Description: Author Institution: Department of Chemistry, University of Florida; Department of Chemistry, Canisius College
URI: http://hdl.handle.net/1811/9088
Other Identifiers: 1972-P-5
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