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CONCENTRATION‐DEPENDENT LIFETIMES OF Cu(NN)+ 2 SYSTEMS: EXCIPLEX QUENCHING FROM THE ION PAIR STATE
Author(s) -
Everly R. Michael,
McMillin David R.
Publication year - 1989
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1989.tb02900.x
Subject(s) - quenching (fluorescence) , ion , chemistry , limiting , counterion , excited state , excimer , analytical chemistry (journal) , phenanthroline , inorganic chemistry , atomic physics , fluorescence , physics , chromatography , organic chemistry , mechanical engineering , quantum mechanics , engineering
— The concentration dependence of the lifetimes of the charge transfer excited states of Cu(dmp) + 2 and Cu(dpp) + 2 has been investigated in CH 2 C1 2 solution at 20 ° C. (dmp denotes 2,9‐dimethyf‐1,10‐phenanthroline, and dpp denotes 2,9‐diphenyl‐l,10‐phenanthroline.) In dilute solution (< 30 μM) the lifetime of Cu(dmp) + 2 , is 95 ± 5 ns, independent of the anion. At higher concentrations the lifetime decreases, in most cases, to a limiting value that depends upon the counterion. The measured limiting lifetimes range from 38 ± 3 ns for CIO ‐ 4 to 78 ± 5 ns for PF ‐ 6 . The anion‐induced quenching is attributed to exciplex quenching which is mediated by an ion pair which exists in the ground state. The results imply that the quenching ability of the anions follows the order BPh‐ 4 < PF ‐ 6 , < BF‐ 4 < CIO ‐ 4 < NO‐ 3 which is consistent with previous estimates of donor strength. The lifetime of Cu(dpp) + 2 is also concentration dependent, but the effect is much smaller because the phenyl substituents impede attack by the anion.