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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]

[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]

[Display omitted] • Photochemistry of light-activated antitumor agent cis -[Rh(dppz)(phen)Cl 2 ]Cl is studied. • Photoaquation is the primary photochemical process. • Two excited states, 1LMCT and 1IL, are initially formed. • Photoaquation occurs via lowest 3MC excited state. The photoactivated drug usage in anti-cancer therapy, the working mechanism of which doesn't rely on the formation of reactive oxygen species, allows reducing damage to healthy tissue by controlling toxicity. For instance, light-activated Rh(III) complexes show nuclease activity after irradiation with UV and visible light. However, literature analysis shows a lack of descriptions of basic photochemical mechanisms. Here we report the study of cis-[Rh(dppz)(phen)Cl 2 ]Cl (DPPZPHEN, dppz is dipyrido[3,2-a:2′,3′-c]phenazine, phen is 1,10-phenanthroline) photochemistry in water solutions using stationary photolysis, nanosecond laser flash photolysis and ultrafast pump–probe spectroscopy. After the irradiation with 308 nm light, DPPZPHEN undergoes aquation, which results in the substitution of one chloride ligand by a water molecule and leads to the formation of [Rh(dppz)(phen)(H 2 O)Cl]Cl 2. UV–vis spectra of complex and capillary electrophoresis data were collected and discussed. Laser flash photolysis (355 nm) demonstrates intermediate absorption attributed to the lowest electronic excited state (triplet) of the initial complex. The study of primary photophysical processes showed a rather complicated behavior of transient absorption, which could be described by a set of four exponential functions. The early photophysical processes were described by the scheme including the formation of two excited states of different natures, namely a dppz-based IL state and an LMCT state. [ABSTRACT FROM AUTHOR]

The photophysical and photochemial properties of dipyrido[3,2-a:2′,3′- c phenazine (dppz) in acetonitrile have been investigated by laser flash photolysis and ultrafast pump-probe spectroscopy. The excitation of dppz to the first singlet excited state was followed by vibrational cooling with solvent relaxation for ∼3 ps and then intersystem crossing for ∼50 ps. Spectral and kinetic characteristics of the triplet excited state have been determined. [ABSTRACT FROM AUTHOR]

Early processes in photochemistry of 2,3-bis(2,5-dimethylthiophen-3-yl)cyclopent-2-enone were explored using the ultrafast pump-probe spectroscopy. The photocyclization occurs from the antiparallel conformation of an open form on a time scale of 7 ps, while the parallel conformation exhibits an intersystem crossing within 130 ps. The mechanism and timescales were revealed as typical of other thiophene-containing diarylethenes. [ABSTRACT FROM AUTHOR]