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The ultrafast processes caused by photoexcitation of (n-Bu4N)2[Pt(NO3)6] complex in acetonitrile were studied by means of transient absorption (TA) pump-probe spectroscopy and verified by quantum chemical calculations. The primary photochemical process was found to be an inner-sphere electron transfer followed by an escape of an •NO3 radical to the bulk solution. The reaction occurs via the dissociative triplet excited LMCT state of the initial complex. Based on the experimental data and quantum chemical calculations, the mechanism of ultrafast photophysical and photochemical processes is proposed. [ABSTRACT FROM AUTHOR]

A study of luminescence and photochromic properties of (E)-2,3-bis(2,5-dimethylthiophen-3-yl)-5-(4-(pyrrolidin-1-yl)benzylidene)cyclopent-2-en-1-one, which is a diarylethene with a push–pull system between carbonyl and dimethylamino groups, was performed using time-resolved methods. The intramolecular charge transfer (ICT) process as well as 6π-electrocyclization and E-/Z-isomerization contribute to the complex light-induced properties of this molecule. Formation of unexpected short-lived intermediates was detected in the time range from 100 fs to 100 μs. A model based on two processes (additional photocyclization and interconversion between conformers) was proposed to rationalize this result. The key intermediates existing in the picosecond time domain are so-called precursors, which are proposed for both parallel (p) and anti-parallel (ap) isomers of the open form. In general, fast light-induced processes for the fluorescent diarylcyclopentenones are much more complicated than for the parent cyclopentenone-based DAE. [ABSTRACT FROM AUTHOR]

Herein we report the synthesis, characterization, photophysical and theoretical study of the luminescent dyad Ir‐RhB containing two emissive centers: The first fluorescent (RhB=rhodamine B) and the second phosphorescent (Ir=orthometalated iridium complex), bound with an aliphatic bridge. These nearly independent chromophores have triplet excited states which are very close in terms of energy, allowing for reversible energy transfer between them. The observed transient absorption spectra and their time dependent variations were interpreted in terms of a relatively simple kinetic model, where selective excitation of the iridium‐based chromophore affords the corresponding emissive triplet state, followed by its equilibration with the rhodamine based triplet state and simultaneous emissive relaxation to the dyad ground state. This model allows for analytical solution to give key characteristics of the dyad excited‐state dynamics, including the energy gap between these triplets (ΔE=0.017 eV) and the rate constant of energy transfer (k(Ir‐RhB)=6.0 ⋅ 108 s−1). These data were also verified by quantum chemical DFT and TD‐DFT calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] Using ultrafast transient absorption spectroscopy, primary photophysical processes in aqueous and acetonitrile solutions of the trans , trans , trans -[Ptiv (N 3) 2 (py) 2 (OH) 2 ] complex, which is interesting as a potential light-activated anticancer drug, were investigated. A mechanism for early photoprocesses has been proposed, including ultrafast intersystem crossing and reductive dissociation. [ABSTRACT FROM AUTHOR]