臺灣博碩士論文加值系統

三個銥(III)錯合物Ir(ppy)2(CN)2- (1)、Ir(ppy)2(NCS)2- (2) 和Ir(ppy)2(NCO)2- (3)的光物理性質在文獻中已被發現和探討。經由我們理論計算(TD-DFT) 結合了溶劑效應(CPCM)所得的最低三重激發態與能量，和文獻報導的放光波長比較可得到令人信服的結果。藉由分析三個錯合物Optical Orbitals (HOMO 和 LUMO)的組成，我們可以瞭解造成實驗上放光行為的差異(藍、綠、黃)是源自於配位子的p-donating或p-accepting特性所造成的HOMO能階位移。我們修改了Roald Hoffmann 的分子軌域作用圖，來表示配位子中硫或氧的孤對電子與NC p-p* 體系的相互作用。而這些分子軌域，則是基於天然鍵性軌域方法所獲得。

The photophysical properties of a series of cyclometalated Ir(III) complexes Ir(ppy)2(CN)2- (1), Ir(ppy)2(NCS)2- (2), and Ir(ppy)2(NCO)2- (3) (where ppy = 2-phenyl pyridine, CN = cyanide, NCS = isothiocyanate, and NCO = isocyanate) have been reported. It is concluded that time-dependent density functional theory (TD-DFT) calculations supply theoretical interpretation of the triplet excited states and the nature of photophysical behaviors reported in literature. Combined with conductive polarizable continuum model (CPCM) the calculations are valid in examining the solvent effect on excitation energies. Analysis of highest occupied molecular orbital (HOMO) and lowest unoccupied orbital (LUMO) obtained by B3LYP functional reveals effects of p-donating and/or p-accepting properties of three pseudohalogens on optical orbitals in complexes 1, 2, and 3. The origin of HOMO tuning up, results in the blue, green and yellow photoluminescence observed in experiments, can be interpreted by interaction between the lone pairs perturbed p-p*(NC) system with metal dp orbitals. We have modified the Hoffman’s orbital interaction diagram to demonstrate effects of sulfur or oxygen atoms on the energy of p(NC). The degree of HOMO tuning-up is parallel to the lone-pair contribution to the perturbed p (NC) analyzed by the natural bonding orbital (NBO) method.

摘要..........................................................................Ⅰ
Abstract......................................................................Ⅱ
Context.......................................................................Ⅲ
List of Schemes..............................................................IⅤ
List of Tables...............................................................IⅤ
List of Figures..............................................................IⅤ
1. Introduction...............................................................1
2. Theoretical Methods........................................................3
2.1 Natural Bonding Orbital....................................................3
2.2 Second Order Perturbation Theory...........................................4
2.3 Linear Combination of Bond Orbital-Molecular Orbitals (LCBO-MO)............5
2.4 Spin Densities.............................................................5
2.5 Time-Dependent Density Functional Theory...................................6
3. Computational Details......................................................8
4. Results and Discussions....................................................9
4.1 Ground State Structures....................................................9
4.2 Molecular Orbital Energies and Composition.................................9
4.3 s-donating and p-accepting Properties of Pseudohalogens...................11
4.4 LCBO-MO Analyses..........................................................12
4.5 Ionization Potentials and Spin Densities..................................14
4.6 TD-DFT Results............................................................15
5. Conclusion................................................................17


List of Schemes
Scheme 1 Orbital Interaction in Complexes.....................................18
Scheme 2 Orbital Interactions in Pseudohalogens...............................19

List of Tables
Table 1 Selected ground state geometry parameters.............................20
Table 2 Frontier Orbitals of these Three Complexes............................20
Table 3 LCAO-MO of HOMOs in the Three Complexes...............................21
Table 4 s-donating and p-accepting Capabilities by Donor-Acceptor Interaction.21
Table 5 LCBO-MO of HOMOs by Pseudohalogens in the Three Complexes.............21
Table 6 Ionization Potentials and Spin Densities for the Three Complexes......22
Table 7 Triplet Excited States from TD-DFT/CPCM Calculation...................22

List of Figures
Figure 1a Molecular Structure of [Ir(ppy)2(CN)2]-............................23
Figure 1b Molecular Structure of [Ir(ppy)2(NCS)2]-...........................23
Figure 1c Molecular Structure of [Ir(ppy)2(NCO)2]-...........................23
Figure 2 Orbital Energy and Assignment of Complexes Frontier Orbitals.......24
Figure 3 Contour Plots of Selected MOs......................................25
Figure 3a HOMO of [Ir(ppy)2(CN)2]-...........................................25
Figure 3b HOMO of [Ir(ppy)2(NCS)2]-..........................................25
Figure 3c HOMO of [Ir(ppy)2(NCO)2]-..........................................25
Figure 3d LUMO of [Ir(ppy)2(CN)2]-...........................................25
Figure 3e LUMO of [Ir(ppy)2(NCS)2]-..........................................25
Figure 3f LUMO of [Ir(ppy)2(NCO)2]-..........................................25

Reference.....................................................................26

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