scholarly journals Emission spectroscopy of a ruthenium(ii) polypyridyl complex adsorbed on calcium niobate lamellar solids and nanosheets

2015 ◽  
Vol 17 (27) ◽  
pp. 17962-17966 ◽  
Author(s):  
Kazuhiko Maeda ◽  
Takayoshi Oshima ◽  
Osamu Ishitani
Keyword(s):  
Excited State ◽  
Conduction Band ◽  
Morphological Feature ◽  
Emission Spectroscopy ◽  
Preparation Method ◽  
Electron Injection ◽  
Polypyridyl Complex ◽  
Calcium Niobate

Electron injection from the excited state of a Ru(ii) polypyridyl complex occurs not only in the conduction band of HCa2Nb3O10 but also surface traps whose density is strongly dependent on both the morphological feature and the preparation method of HCa2Nb3O10.

scholarly journals Photoexcitation of Ge9− Clusters in THF: New Insights into the Ultrafast Relaxation Dynamics and the Influence of the Cation

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2639
Author(s):  
Nadine C. Michenfelder ◽  
Christian Gienger ◽  
Melina Dilanas ◽  
Andreas Schnepf ◽  
Andreas-Neil Unterreiner
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Conduction Band ◽  
Near Infrared ◽  
Transient Absorption ◽  
Time Window ◽  
Excess Electron ◽  
Cluster Core ◽  
Relaxation Dynamics ◽  
Additional Time

We present a comprehensive femtosecond (fs) transient absorption study of the [Ge9(Hyp)3]− (Hyp = Si(SiMe3)3) cluster solvated in tetrahydrofuran (THF) with special emphasis on intra- and intermolecular charge transfer mechanisms which can be tuned by exchange of the counterion and by dimerization of the cluster. The examination of the visible and the near infrared (NIR) spectral range reveals four different processes of cluster dynamics after UV (267/258 nm) photoexcitation related to charge transfer to solvent and localized excited states in the cluster. The resulting transient absorption is mainly observed in the NIR region. In the UV-Vis range transient absorption of the (neutral) cluster core with similar dynamics can be observed. By transferring concepts of: (i) charge transfer to the solvent known from solvated Na− in THF and (ii) charge transfer in bulk-like materials on metalloid cluster systems containing [Ge9(Hyp)3]− moieties, we can nicely interpret the experimental findings for the different compounds. The first process occurs on a fs timescale and is attributed to localization of the excited electron in the quasi-conduction band/excited state which competes with a charge transfer to the solvent. The latter leads to an excess electron initially located in the vicinity of the parent cluster within the same solvent shell. In a second step, it can recombine with the cluster core with time constants in the picosecond (ps) timescale. Some electrons can escape the influence of the cluster leading to a solvated electron or after interaction with a cation to a contact pair both with lifetimes exceeding our experimentally accessible time window of 1 nanosecond (ns). An additional time constant on a tens of ps timescale is pronounced in the UV-Vis range which can be attributed to the recombination rate of the excited state or quasi conduction band of Ge9−. In the dimer, the excess electron cannot escape the molecule due to strong trapping by the Zn cation that links the two cluster cores.

scholarly journals Dynamic solvatochromism in solvent mixtures

2001 ◽  
Vol 73 (3) ◽  
pp. 405-409 ◽  
Author(s):  
Diana E. Wetzler ◽  
Carlos Chesta ◽  
Roberto Fernández-Prini ◽  
Pedro F. Aramendía
Keyword(s):  
Excited State ◽  
Ground State ◽  
Emission Spectroscopy ◽  
Characteristic Time ◽  
Polar Solvent ◽  
Emission Spectra ◽  
Spectral Shift ◽  
Solvent Mixtures ◽  
Time Resolved ◽  
Different Temperatures

Solvatochromism and thermochromism of 4-aminophthalimide and 4-amino-N-methylphthalimide were studied by absorption and steady-state and time-resolved emission spectroscopy in solvent mixtures of toluene­ethanol and toluene­acetonitrile at different temperatures. Emission spectra shift to the red upon addition of a polar solvent (PS) to toluene. Solvent mixtures show a much greater thermochromic shift to the blue in emission than the neat solvents. This is explained by the decrease in temperature of the exothermic association of the polar solvent to the excited state. Emission spectra are time dependent in solvent mixtures in the ns timescale. The time evolution of this emission is interpreted on the basis of the different solvation of the ground state and the emitting excited state. Stern­Volmer plots are obtained for the dependence of the spectral-shift characteristic time with [PS].

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