Lewis, J.D., Perutz, R.N. and Moore, J.N. (2004) Light-controlled ion switching: direct observation of the complete nanosecond release and microsecond recapture cycle of an azacrown-substituted [(bpy)Re(CO)3L]+ complex. Journal of Physical Chemistry A, 108 (42). pp. 9037-9047. ISSN 1089-5639
A [(bpy)Re(CO)3L]+ complex (bpy = 2,2‘-bipyridine) in which L contains an azacrown ether (MacQueen, D. B.; Schanze, K. S. J. Am. Chem. Soc. 1991, 113, 6108) acts as a reversible light-controlled switch of alkali and alkaline earth metal cations bound to the azacrown, as observed directly by time-resolved UV−vis spectroscopy. Excitation to the metal-to-ligand charge-transfer (MLCT) state of the metal-complexed form, [(bpy)Re(CO)3L]+-Mn+, results in cation release on the nanosecond time scale for Mn+ = Li+, Na+, Ca2+, and Ba2+, with Li+ and Na+ being released more rapidly than Ca2+ and Ba2+; by contrast, Mg2+ is not released. After decay to the ground state, [(bpy)Re(CO)3L]+ recaptures metal cations on the microsecond time scale to restore the starting thermal equilibrium. A multistep rebinding mechanism is observed for Li+ and Na+, in which the cation attaches initially to the azacrown nitrogen atom before binding to the equilibrium position within the azacrown ring. The excited states and other intermediates in the cation release-and-recapture cycle have been observed directly in real time, and their decay rate constants have been determined as a function of cation identity, enabling a generalized light-controlled cation-switching mechanism to be developed for this generic molecular design.
|Institution:||The University of York|
|Academic Units:||The University of York > Chemistry (York)|
|Depositing User:||York RAE Import|
|Date Deposited:||20 Apr 2009 13:23|
|Last Modified:||20 Apr 2009 13:23|
|Publisher:||American Chemical Society|