2014-现代化学方法和技术解说.pptVIP

Work out example B1g B2u D4h ? ?i(x, y, z) ?j d? In D4h, z ? A2u and x , y ? Eu B1g? A2u ?B2u = A1g B1g? Eu ?B2u = Eg Thus, ? ? ?* transition allowed with z polarization. Interpretations of d – d transition in metal complexes. 1. Mixture of d and p orbitals of the same symmetry species. In Td symmetry, both p orbtils (px, py, pz) and d orbtials (dxy, dxz and dyz) belong to the same irreducible representation T2. Therefore, they are mixing in the t2 a of Tetrahedral metal complex. So, the transition e ? t2 is not strictly d – d. For example, [Co(H2O)6]2+, pink; [CoCl4]2? deep blue; [Ni(H2O)6]2+, pale green; [NiBr4] 2? purple 2. Vibronic Vibration modes deform octahedral molecule and reduces its symmetry from Oh to C4v or to C2v T1u For C4v and C2v, dz2, pz and s belongs to the same irreduciabl representation A1; therefore, they are mixed. The d-d transition is no longer purer. 3. Spin-orbital coupling For Ni2+, d8 ion, 3A2g ? 1Eg transition is observed as a weak, fine band. A2 ? T1 (S = 1) ? T2; E?A1(S = 0) ? E T2 ? E ? T1 + T2 Since there presentation of x, y, z in O point group is T1 and in Oh T1u, the transition is allowed. Complexes without an inversion center, e.g.,[CrIII(acac)3] or [CrIII(ox)3]3?, d3 Possible transitions in Oh and D3 symmetry Allowed and polarized nature of d?d transition in a d3 ion (D3) Transition moment in D3 symmetry: ?z (A2) ?x + ?y (E) 4. Band Polarization Dipolar moment ? Possible transitions in Oh and D4h symmetry Complexes with an inversion center [CoCl2(en)2]+ , d6 Transition moment in D4h symmetry: ?z (A2u) ?x + ?y (Eu) Normal vibrational modes: A2u + B2u + 2Eu Allowed and polarized by means of vibronic couupling Electronic spectrum of a d6 ion (D4h) 1A1g ? 1Eg 1A1g ? 1A2g Charge-Transfer Spectra Octahedral complexes (Oh) M ? L Charge Transfer, or MLCT L ? M Charge Transfer, or LMCT d0, MnO4?, CrO42? L?M CT M ? L CT d8, [PtCl4]2? Creutz-Taube Complex: Questions to Be Answered: