含咪唑、吡唑或吡啶配位基之環金屬銥 (III) 錯合物的拉曼光譜與其放光機制之研究

Investigation of Emission Mechanism and Raman Spectra of Cyclometalated Ir(III) Complexes with Imidazolyl, Pyrazolyl, and Pyridyl-based Ligands

蔡惠如(Huei-Ru Tsai)

指導教授 ： 陳益佳

國立清華大學/理學院/化學系/碩士(2011年)

https://doi.org/10.6843/NTHU.2011.00239

摘要

我們由紫外-可見吸收、放光和激發光譜配合TD-DFT計算結果，研究錯合物fac-tris(1-(4-fluorophenyl)-3-methylimidazolin-2-ylidene-C,C2')
iridium(III)，fac-Ir(fpmi)3，和fac-tris(1-(2,4-fluorophenyl)-3-methylimidazolin-
2-ylidene-C,C2')iridium(III)，fac-Ir(dfpmi)3，的放光機制；及配位基1-(4-
fluorophenyl)-3-methyl-1H-imidazol-3-ium iodide (H2fpmi+I-)、1-(2,4-
difluorophenyl)-3-methyl-1H-imidazol-3-ium iodide (H2dfpmi+I-)、1-(4-
fluorophenyl)-3-methyl-1H-imidazol-3-ium hexafluorophosphate (H2fpmi+PF6-) 和1-(2,4-difluorophenyl)-3-methyl-1H-imidazol-3-ium hexafluorophosphate
(H2dfpmi+PF6-) 之結構與放光行為。由拉曼和紅外光譜結果配合DFT計算結果，指認fac-Ir(fpmi)3、fac-Ir(dfpmi)3、fac-Ir(ppz)3及FIrpic振動光譜。　　常溫下四個配位基在320 ~ 440 nm均有放光，指認為1π-π* 之能階的放光，但可能具有較高的位能障礙，故在低溫下無法觀測到。常溫和低溫下錯合物的在370 ~ 500 nm處由3π-π* 而來的磷光具有振動精細結構。低溫激發光譜指出錯合物在240 ~ 270 nm處之激發態為配位基而來之1π-π*，在280 ~ 340 nm處之激發態為1MLCT及3MLCT，均造成3π-π* 的放光。拉曼光譜中，我們指認6個金屬和配位基之間的伸張振動，fac-Ir(fpmi)3之ν(Ir-C) 和ν(Ir-C:) 各在286/303和332 cm-1；fac-Ir(dfpmi)3之ν(Ir-C) 及ν(Ir-C:) 各在283/299及377 cm-1；fac-Ir(ppz)3之ν(Ir-N) 與ν(Ir-C) 各在229/243與270/321 cm-1。FIrpic的ν(Ir-Npic)、ν(Ir-Nph)、ν(Ir-O) 和ν(Ir-C)，各在267、282、304和321 cm-1。雙氟fac-Ir(dfpmi)3比單氟fac-Ir(fpmi)3之ν(Ir-C:) 藍位移45 cm-1；雙氟的FIrpic比fac-Ir(ppy)3之ν(Ir-N) 與ν(Ir-C) 亦有明顯的藍位移，顯示較強之銥-配位基鍵結。

關鍵字

拉曼 ； 碳烯 ； 銥金屬錯合物 ； 放光機制

並列摘要

We recorded the UV-vis absorption, emission and excitation spectra for complexes fac-tris(1-(4-fluorophenyl)-3-methylimidazolin -2-ylidene-C,C2') iridium(III), fac-Ir(fpmi)3, and fac-tris(1-(2,4–fluorophenyl)-3-methyl imidazolin-2-ylidene-C,C2')iridium (III), fac-Ir(dfpmi)3 and their ligands 1-(4-fluorophenyl)-3-methyl-1H-imidazol-3-ium iodide (H2fpmi+I-), 1-(2,4- difluorophenyl)-3-methyl-1H-imidazol-3-ium iodide (H2dfpmi+I-), 1-(4- fluorophenyl)-3-methyl-1H-imidazol-3-ium hexafluorophosphate (H2fpmi+PF6-) and 1-(2,4-difluorophenyl)-3-methyl-1H-imidazol-3-ium hexafluorophosphate (H2dfpmi+PF6-). Using theoretical calculations-density functional theory (DFT) and time-dependent DFT (TD-DFT), we obtained their optimized structures and assigned the emission bands at 320-440 nm and 370-500 nm to 1π-π* and 3π-π* for the ligands and complexes, respectively. For these blue-emission complexes the lowest emission bands are from 3π-π* instead of the triplet metal-ligand charge transfer state. This explains the low photoemission quantum yield for these complexes. We also recorded the Raman and IR spectra. From comparing with the results of DFT calculations, we assigned the vibrational spectra for fac-Ir(fpmi)3, fac-Ir(dfpmi)3, fac-Ir(ppz)3 and FIrpic. We assigned six Ir-ligand stretching, ν(Ir-C) and ν(Ir-C:) to Raman lines 286/303 and 332 cm-1 for fac-Ir(fpmi)3, and 283/299 and 377 cm-1 for fac-Ir(dfpmi)3, ν(Ir-N) and ν(Ir-C) to 229/243 and 270/321 cm-1 for fac-Ir(ppz)3, and ν(Ir-Npic), ν(Ir-Nph), ν(Ir-O) and ν(Ir-C) to 267, 282, 304 and 321 cm-1 for FIrpic. For fac-Ir(dfpmi)3 the ν(Ir-C:) band is blue-shifted 45 cm-1 than that in fac-Ir(fpmi)3. For FIrpic ν(Ir-N) and ν(Ir-C) are also blue-shifted than those for fac-Ir(ppy)3 showing strong Ir-ligand bonding.

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