5 research outputs found
Interligand Electron Transfer in Heteroleptic Ruthenium(II) Complexes Occurs on Multiple Time Scales
The
time-dependent localization of the metal-to-ligand charge transfer
(MLCT) excited states of rutheniumĀ(II) complexes containing 2,2ā²-bipyridine
(bpy) and 1,10-phenanthroline (phen) ligands was studied by femtosecond
transient absorption spectroscopy. Time-resolved anisotropy measurements
indicate that the excited state hops randomly among the three ligands
of each complex by subpicosecond interligand electron transfer (ILET).
Although the bpy- and phen-localized <sup>3</sup>MLCT states have
similar energies and steady-state emission spectra, pronounced differences
in their excited-state absorption spectra make it possible to observe
changes in excited state populations using magic angle transient absorption
measurements. Analysis of the magic angle signals shows that the excited
electron is equally likely to be found on any of the three ligands
approximately 1 ps after excitation, but this statistical distribution
subsequently evolves to a Boltzmann distribution with a time constant
of approximately 10 ps. The apparent contradiction between ultrafast
ILET revealed by time-dependent anisotropy measurements and the slower
ILET seen in magic angle measurements on the tens of picoseconds time
scale is explained by a model in which the underlying rates depend
dynamically on excess vibrational energy. The insight that ILET can
occur over multiple time scales reconciles contradictory literature
observations and may lead to improved photosensitizer performance
Site-Directed Coordination Chemistry with P22 Virus-like Particles
Protein cage nanoparticles (PCNs) are attractive platforms for developing functional nanomaterials using biomimetic approaches for functionalization and cargo encapsulation. Many strategies have been employed to direct the loading of molecular cargos inside a wide range of PCN architectures. Here we demonstrate the exploitation of a metal-ligand coordination bond with respect to the direct packing of guest molecules on the interior interface of a virus-like PCN derived from Salmonella typhimurium bacteriophage P22. The incorporation of these guest species was assessed using mass spectrometry, multiangle laser light scattering, and analytical ultracentrifugation. In addition to small-molecule encapsulation, this approach was also effective for the directed synthesis of a large macromolecular coordination polymer packed inside of the P22 capsid and initiated on the interior surface. A wide range of metals and ligands with different thermodynamic affinities and kinetic stabilities are potentially available for this approach, highlighting the potential for metal-ligand coordination chemistry to direct the site-specific incorporation of cargo molecules for a variety of applications.close