The Electroni Spectra of Coordination Compounds配合物的电子光谱.pptVIP

The Electronic Spectra of Coordination Compounds Electron Spectra The UV/Vis spectra are used to determine the value of ?o for the complex. The spectra arise from electronic transitions between the t2g and eg sets of molecular orbitals. Electron-electron interactions can greatly complicate the spectra. Only in the case of a single electron is interpretation of the spectrum straightforward. Obtaining ?o For a d1 configuration, only a single peak is seen. It results from the electron promotion from the t2g orbitals to the eg orbitals. The “toothed” appearance of the peak is due to a Jahn-Teller distortion of the excited state. The energy of the peak = ?o. General Observations d1, d4, d6 and d9 usually have 1 absorption, though a side “hump” results from Jahn-Teller distortions. General Observations d2, d3, d7 and d8 usually have 3 absorptions, one is often obscured by a charge transfer band. General Observations d5 complexes consist of very weak, relatively sharp transitions which are spin-forbidden, and have a very low intensity. Qualitative Explanation Consider a Cr(III) complex such as [Cr(NH3)6]3+. The ground state configuration is: ____ ____ A transition from the dz2 dx2-y2 dxy to the dx2-y2, or the dyz or dxz to the dz2 ____ ____ ____ orbitals involve a relatively dxy dyz dxz minor change in environment. Qualitative Explanation The transition from the dxz orbitals to the dz2 orbitals involves a relatively minor change in the electronic environment. Qualitative Explanation Consider a Cr(III) complex such as [Cr(NH3)6]3+. The ground state configuration is: ____ ____ A transition from the dz2 dx2-y2 dxy to the dz2, or the dyz or dxz to the dx2-y2 ____ ____ ____ orbitals involve a major dxy dyz dxz change in environment. Qualitative Explanation The transition from orbitals in the xy plane to the dz2 orbitals involves a fairly major change in the electronic environm