Photophysics of AgCl doped with [Cl5Ir(N-methylpyrazinium)]-: I. EPR, ENDOR and structural calculations
| Autor: | R S Eachus, R C Baetzold, W G McDugle, Thomas D. Pawlik, D A Crosby |
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| Rok vydání: | 2000 |
| Předmět: | |
| Zdroj: | Journal of Physics: Condensed Matter. 12:2535-2553 |
| ISSN: | 1361-648X 0953-8984 |
| DOI: | 10.1088/0953-8984/12/11/318 |
| Popis: | By applying a combination of multi-frequency electron paramagnetic resonance spectroscopy, electron nuclear double resonance spectroscopy and advanced computational techniques, an understanding of the effects of [Cl5 Ir(NMP)]- complexes on the photophysics of AgCl dispersions is emerging (NMP = N-methylpyrazinium). There is indirect spectroscopic evidence that this dopant is incorporated intact during AgCl precipitation. Calculations predict its substitution for an (Ag2 Cl7 )5- sub-unit of the host lattice, with the NMP ring rotated 45? with respect to the equatorial chloride ligands. Calculations also show that, in grains with edge lengths 0.05 ?m, the majority of dopant centres will be fully charge compensated by association with four silver ion vacancies. A (101)( 01)(01 )(0 ) geometry is favoured, where the Cl-Ir-(NMP) axis defines z . Photo-EPR experiments suggest a small population of under-compensated {[Cl5 Ir(NMP)]- 3V} centres also exists in most of the dispersions studied. During exposure to actinic light, these dopant centres trap electrons. Since the dopant's LUMO is primarily a * NMP orbital, the initial photoproducts are ligand-centred, one-electron donors. Experimental 1 H hyperfine data obtained by powder ENDOR spectroscopy for the favoured vacancy geometry of {[Cl5 Ir(NMP)]2- 4V} are consistent with the unpaired electron distribution calculated by Hartree-Fock methods. Vacancy binding energies are so large that the over-compensated donor ionizes before the extra vacancy diffuses away. |
| Databáze: | OpenAIRE |
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