Intraligand Charge Transfer in the Pd(II) Oxinate Complex Pd(qol)2. Site-Selective Emission, Excitation, and Optically Detected Magnetic Resonance
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- 作者：Hartmut Yersin ; Dirk Donges ; Jeffrey K. Nagle ; Rolf Sitters ; and Max Glasbeek
- 刊名：Inorganic Chemistry
- 出版年：2000
- 出版时间：February 21, 2000
- 年：2000
- 卷：39
- 期：4
- 页码：770 - 777
- 全文大小：108K
- 年卷期：v.39,no.4(February 21, 2000)
- ISSN：1520-510X
文摘
The first spectroscopic investigation of Pd(qol)2 (qol- = 8-quinolinolato-N,O = oxinate) dissolved in an n-octanematrix (Shpol'skii matrix) is reported. Application of several spectroscopic methods at liquid helium temperatures(typically, T = 1.2 K), such as site-selective and highly resolved luminescence and excitation spectroscopy, time-resolved emission spectroscopy, optically detected magnetic resonance, microwave recovery, phosphorescencemicrowave double-resonance, and magnetic fields, allows us to characterize the lowest excited electronic statesin detail. In accord with previous assignments for the related Pt(qol)2 it is shown that these lowest states representintraligand charge-transfer states, namely, 1ILCT and 3ILCT. The electronic origin of the 1ILCT state lies at20 617 cm-1 (site A). It exhibits a nearly homogeneous line width with a half-width of about 80 cm-1 (fwhm),which corresponds to a lifetime of 
(1ILCT) 
2 × 10-13 s. This value is even shorter than that found for Pt(qol)2, presumably due to intersystem crossings and relaxations to dd* states. The electronic origin of the 3ILCTstate lies at 16 090 cm-1 (site A), and its zero-field splittings (zfs) into three sublevels are 2E = 2356 MHz(0.0785 cm-1) and D - E = 5241 MHz (0.175 cm-1). The emission decay times of the three sublevels aredetermined as I = 90 ± 30 ms, II = 180 ± 10 
s, and III = 80 ± 10 s. (Slightly different values are foundfor a second site B at 16 167 cm-1.) From the small values of zfs and the long emission decay times it is concludedthat metal-d or MLCT admixtures to 3ILCT are very small. This result clearly reflects the ligand-centered characterof the transition. The assignment as an ILCT transition is supported by the occurrence of relatively strong vibrationalsatellites of Pd-N and Pd-O character in highly resolved emission spectra. Although the transition is ascribedto a charge-transfer process, the geometry changes between the ground state and 3ILCT are very small. Theresults found for Pd(qol)2 are compared to those of companion studies of Pt(qol)2 and Pt(qtl)2 (qtl- =8-quinolinethiolato-N,S).
(1ILCT) 2 × 10-13 s. This value is even shorter than that found for Pt(qol)2, presumably due to intersystem crossings and relaxations to dd* states. The electronic origin of the 3ILCTstate lies at 16 090 cm-1 (site A), and its zero-field splittings (zfs) into three sublevels are 2E = 2356 MHz(0.0785 cm-1) and D - E = 5241 MHz (0.175 cm-1). The emission decay times of the three sublevels aredetermined as I = 90 ± 30 ms, II = 180 ± 10 s, and III = 80 ± 10 s. (Slightly different values are foundfor a second site B at 16 167 cm-1.) From the small values of zfs and the long emission decay times it is concludedthat metal-d or MLCT admixtures to 3ILCT are very small. This result clearly reflects the ligand-centered characterof the transition. The assignment as an ILCT transition is supported by the occurrence of relatively strong vibrationalsatellites of Pd-N and Pd-O character in highly resolved emission spectra. Although the transition is ascribedto a charge-transfer process, the geometry changes between the ground state and 3ILCT are very small. Theresults found for Pd(qol)2 are compared to those of companion studies of Pt(qol)2 and Pt(qtl)2 (qtl- =8-quinolinethiolato-N,S).