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Dual emission is a reality in many, but not all, ruthenium complex ions, even at room temperature and in fluid solution. It requires significantly different ligands and is more obvious in rigid media such as glasses at low temperature and crystalline powders. However, there are not just two unique lifetimes. Rather, there is a continuum of similar but slightly different lifetimes drawn from a bimodal distribution. In some of the cases that do not show dual emission, there still seems to be a continuum within a unimodal distribution. After reviewing a wide range of data, we describe possible interpretations. Most novel, but in our view most attractive, is a major role for ion pairing. If one admits that ions near charge transfer orbitals should have a stabilizing effect, and if one doubts that there would be any unique configuration for ion pairs, then it would seem that a continuous variation of excited state behavior is mandatory. This mechanism accounts for the fact that highly asymmetric substitutions at the 4-position of the phen ligand that most affects charge transfer always show dual emission and offer the most exaggerated differences between the two emissions. Other possibilities remain, given the data available at this time.

A family of dendritic tris-bipyridyl ruthenium coordination complexes incorporating two or four carboxylate groups for binding to a TiO(2) surface site and another dendritic linker between the metal complex and highly absorptive dyes were formulated as thin films on TiO(2) coated glass. The family included phenothiazine-substituted dendrons of increasing structural complexity and higher optical density. The dye-loaded films were characterized by steady-state emission and absorption measurements and by kinetic studies of luminescence and transient absorption. Upon photoexcitation of the bound dyes, rapid electron injection into the metal oxide film was the dominant observed process, producing oxidized dye that persisted for hundreds of milliseconds. Complex decay profiles for emission, transient absorption, and optical bleaching of the dendritic dyes point to highly heterogeneous behavior for the films, with observed persistence lifetimes related directly to structurally enhance electronic coupling between the metal oxide support and the dendritic dyes.

© 2015 Elsevier B.V. Dual emission is a reality in many, but not all, ruthenium complex ions, even at room temperature and in fluid solution. It requires significantly different ligands and is more obvious in rigid media such as glasses at low temperature and crystalline powders. However, there are not just two unique lifetimes. Rather, there is a continuum of similar but slightly different lifetimes drawn from a bimodal distribution. In some of the cases that do not show dual emission, there still seems to be a continuum within a unimodal distribution. After reviewing a wide range of data, we describe possible interpretations. Most novel, but in our view most attractive, is a major role for ion pairing. If one admits that ions near charge transfer orbitals should have a stabilizing effect, and if one doubts that there would be any unique configuration for ion pairs, then it would seem that a continuous variation of excited state behavior is mandatory. This mechanism accounts for the fact that highly asymmetric substitutions at the 4-position of the phen ligand that most affects charge transfer always show dual emission and offer the most exaggerated differences between the two emissions. Other possibilities remain, given the data available at this time.

The effect of pressure on the recombination kinetics of small ligands binding to sperm whale myoglobin, protoheme dimethyl ester, and monochelated protoheme was studied with use of laser flash photolysis. The volumes of activation observed indicate that in both the protein and the models bond formation is the rate-determining step only for carbon monoxide, while for oxygen, isocyanides, and 1-methylimidazole almost no bond formation occurs in the transition state of the observed reaction. The effect of pressure on the escape of carbon monoxide, oxygen, and methyl isocyanide from the heme pocket of sperm whale myoglobin was also investigated

A family of heteroleptic RuII coordination complexes containing substituted 1,10-phenanthroline (phen) ligands with extended conjugation was found to exhibit two simultaneously emissive excited states at room temperature in fluid solution. These systems demonstrate a breakdown of the standard non-radiative decay pathways that normally lead to a single, dominant, lowest energy emissive excited state in RuII complexes and most other chromophores. The structural requirements for dual emission were explored through the synthesis and characterization of isomeric systems. Two features were found to be primarily responsible for resolvable dual emission. Extended conjugation at the 4-position of the 1,10-phenanthroline ligand was identified as an essential feature, and asymmetry in the phenanthroline ligand substitutions appears to greatly facilitate the production of these two non-equilibrated emissive states. Additional complexes were studied which displayed “tunable” emissive characteristics for the two excited states as a function of covalent and non-covalent modification.

Tris(bipyridyl)ruthenium(II) complexes modified such that one of the bipyridines is appended with a crown ether display luminescence that is responsive to complexation with metal ions. The parent species, Ru(bpy)3(2+), is moderately luminescent, with an emission lifetime of about 1 micros in fluid solution at room temperature. The modified complexes are much less emissive, with lifetimes near 1 ns. Conformational flexibility and distortion in the crown-ether complexes enhance nonradiative decay. Noncovalent binding of metal ions, however, restores luminescence intensity by reducing nonradiative decay and increasing the lifetime 10- to 100-fold. Reported here are the syntheses and steady-state and time-resolved luminescence measurements in addition to other supporting spectroscopic characterization. Seven metals were investigated; significant luminescence enhancements occur in the presence of Mg2+, Ca2+, and Pb2+. Effective concentrations of metal ions range from tens of microM to hundreds of mM. The steady-state enhancements are readily measured, but they are less than would be expected from the lifetime changes, partly because only a portion (not more than 50%) of the fast (1 ns) decay in Ru(bpy)2(bpy-crown) is capable of converting to the conformation possessing the longer lifetime. A photophysical model is proposed to explain these and other observations.

Etude des durees de vie des especes transitoires generees par la photolyse des six complexes: [Cr(NH 3 ) 2 (NCS) 4 ] − ; [Cr(NCS) 6 ] 3− ; [Cr(en) 3 ] 3+ ; [Cr(bpy) 3 ] 3+ ; [Cr(phen) 3 ] 3+ ; [Cr(acac) 3 ] 3+

Laser-excited luminescence lifetimes of lanthanide ions bound to bacteriorhodopsin have been measured in deionized membranes. The luminescence titration curve, as well as the binding curve of apomembrane (retinal-free) with Eu3+, has shown that the removal of the retinal does not significantly affect the affinity of Eu3+ for the two high affinity sites of bacteriorhodopsin. The D2O effects on decay rate constants indicate that Eu3+ bound to the high affinity sites of native membrane or apomembrane is coordinated by about six ligands in the first coordination sphere. Tb3+ is shown to be coordinated by four ligands. The data indicate that metal ions bind to the protein with a specific geometry. From intermetal energy transfer experiments using Eu3+-Pr3+, Tb3+-Ho3+, and Tb3+-Er3+, the distance between the two high affinity sites is estimated to be 7-8 A.

Spectres d'emission et duree de vie a l'etat excite des complexes du type cis- et trans-[Rh(NH 3 ) 4 XY n+ ] (X=Cl − , Br − , H 2 O; Y=X, H 2 O, OH − )

Comparaison des reactions de photosubstitution de Rh(NH 3 ) 5 I 2+ en solutions aqueuses acides et alcalines, indiquant que l'ion OH − arrete la mobilite de NM 3 , mais augmente celle de I − . Mecanismes. Constantes de vitesse

Comparaison des reactions de photosubstitution de Rh(NH 3 ) 5 I 2+ en solutions aqueuses acides et alcalines, indiquant que l'ion OH − arrete la mobilite de NM 3 , mais augmente celle de I − . Mecanismes. Constantes de vitesse

Spectres d'emission et duree de vie a l'etat excite des complexes du type cis- et trans-[Rh(NH 3 ) 4 XY n+ ] (X=Cl − , Br − , H 2 O; Y=X, H 2 O, OH − )

Measurement of the relaxation time for transient bleaching of solutions of bis-(4-dimethylaminodithiobenzil)-nickel (BDN) explains observed Q -switch and mode-locking behavior. A pronounced solvent effect permits varying relaxation time by a factor of 5 down to times short enough to be considered for mode locking in special circumstances.