title: Revisited photophysics and photochemistry of a Ru-TAP complex using chloride ions and a calix[6]crypturea.
abstract: The effects of the nonprotonated and protonated calix[6]crypturea 1/1(•)H(+) on the PF6(-) and Cl(-) salts of a luminescent Ru-TAP complex (TAP = 1,4,5,8-tetraazaphenanthrene) were investigated. Thus, the phototriggered basic properties of this complex were examined with 1(•)H(+) in acetonitrile (MeCN) and butyronitrile (BuCN). The Ru excited complex was shown to be able to extract a proton from the protonated calixarene, accompanied by a luminescence quenching in both solvents. However, in BuCN, the Cl(-) salt of the complex exhibited a surprising behavior in the presence of 1/1(•)H(+). Although an emission decrease was observed with the protonated calixarene, an emission increase was evidenced in the presence of nonprotonated 1. As the Cl(-) ions were shown to inhibit the luminescence of the complex in BuCN, this luminescence increase by nonprotonated 1 was attributed to the protection effect of 1 by encapsulation of the Cl(-) anions into the tris-urea binding site. The study of the luminescence lifetimes of the Ru-TAP complex in BuCN as a function of temperature for the PF6(-) and Cl(-) salts in the absence and presence of 1 led to the following conclusions. In BuCN, in contrast to MeCN, in addition to ion pairing, because of the poor solvation of the ions, the luminescent metal-to-ligand charge transfer ((3)MLCT) state could reach two metal-centered ((3)MC) states, one of which is in equilibrium with the (3)MLCT state during the emission lifetime. The reaction of Cl(-) with this latter (3)MC state would be responsible for the luminescence quenching, in agreement with the formation of photosubstitution products.
authors.affiliation: Chimie Organique et Photochimie, Université Libre de Bruxelles , CP 160/08, 50 Avenue Franklin Roosevelt, B-1050 Brussels, Belgium.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Rebarz
authors.forename: Lionel
authors.initials: L
authors.lastname: Marcélis
authors.forename: Mickaël
authors.initials: M
authors.lastname: Menand
authors.forename: Damien
authors.initials: D
authors.lastname: Cornut
authors.forename: Cécile
authors.initials: C
authors.lastname: Moucheron
authors.forename: Ivan
authors.initials: I
authors.lastname: Jabin
authors.forename: Andrée
authors.initials: A
authors.lastname: Kirsch-De Mesmaeker