4th EucheMs chemistry congress

thursday, 30-Aug 2012
s830
chem. Listy 106, s587–s1425 (2012)
Physical, theoretical and Computational Chemistry
Ultra fast Processes – ii
o - 5 1 0
GAS-SoLid-Shift in MoLeCuLAr inner-SheLL
trAnSitionS
e. ruehL 1 , r. fLeSCh 1 , e. SerdAroGLu 1 ,
P. feuLner 2 , f. BLoBner 2 , n. KoSuGi 3 ,
A.A. PAvLyChev 4 , x. o. BryKALovA 4 , y. zhAnG 1 ,
B. wASSerMAnn 1
1 Freie Universitaet Berlin, Physical and Theoretical Chemistry,
Berlin, Germany
2 TU Munich, Physik Department, Berlin, Germany
3 Institute for Molecular Science, UVSOR, Okazaki, Japan
4 St. Petersburg State University, Institute of Physics, St.
Petersburg, Russia
Clusters and nanoparticles are known to bridge the gap
between the condensed and the gaseous state of matter. Inner-shell
excitation has been shown earlier to be a suitable approach to
probe size effects of matter. However, accurate comparisons of
core-to-valence transitions between gaseous molecules and the
corresponding condensed phase are scarce.
We present results on spectral changes that are observed
between gaseous and condensed molecules in the inner-shell
excitation regime. The experiments are carried out at the electron
storage ring BESSY II (HZB Berlin). Condensed phase spectra
are obtained from multilayers of condensed molecules. Gas phase
spectra are simultaneously recorded, so that the energy scale is
constant within 5 meV.
Specifically, the C 1s-π * transition in benzene (C H ) is 6 6
studied where a red-shift by 60 meV is observed in the condensed
phase relative to the gas phase spectrum. This spectral shift is
slightly smaller than that observed earlier for free benzene
clusters. These findings are discussed in the context of structural
changes occurring between molecular solids and micro-clusters,
which are studied by ab initio calculations.
Spectral shifts upon cluster formation in solution have also
been observed in liquid microdroplets, when they reach
supersaturation. These studies are performed in the hard X-ray
regime, where the formation of Bjerrum pairs as well as solute
clusters are formed in highly concentrated solutions. Structural
information of such clusters is also inferred from model
calculations.
Keywords: clusters; X-ray absorption spectroscopy;
nanoparticles;
Ultra fast Processes – ii
4 th EucheMs chemistry congress
o - 5 1 1
exCited-StAte ProPertieS in Ph-SwitChABLe
rutheniuM dyeS
M. wäChtLer 1 , M. BräutiGAM 1 , S. KuPfer 1 ,
J. GuthMuLLer 2 , S. rAu 3 , J. PoPP 1 , L. GonzALez 4 ,
B. dietzeK 5
1 Friedrich-Schiller University Jena, Institute of Physical
Chemistry and Abbe Center of Photonics, Jena, Germany
2 Gdansk University of Technology, Faculty of Applied Physics
and Mathematics, Gdansk, Poland
3 University of Ulm, Institute of Inorganic Chemistry I, Ulm,
Germany
4 University of Vienna, Institute of Theoretical Chemistry,
Vienna, Austria
5 Institute of Photonic Technology (IPHT) e.V. Jena, Jena,
Germany
Ruthenium polypyridine dyes are amongst the most studied
compounds due to their unique combination of chemical stability
and redox and optical properties, which are exploited in the design
of e.g. artificial light-harvesting systems and molecular sensors.
By incorporating extended ligand structures bearing basic/acidic
positions, complex structures sensitive to environment pH can be
designed. The resulting effects may be useful for pH-sensing
applications and the design of pH-switchable optical devices. By
de(protonation) the character of individual excited states is
influenced, changing not only the absorption properties. Lifetimes
of excited states and general decay mechanisms of the
photoexcited structures may alter significantly. [1]
Here we present a series of pH-sensitive structures which
were investigated combining experimental and theoretical
approaches. Applying resonance Raman spectroscopy and DFT
calculations a detailed picture of the initial excited states and the
changes induced by (de)protonation is developed. [2] Additionally,
a comparison of calculated and experimental absorption and
resonance Raman spectra allows for unambiguous identification
of the protonated species present at certain pH ranges, which is
especially important in the case of multiple positions available for
protonation. [3] Applying time-resolved transient absorption
spectroscopy the interplay between relative energetic positions of
excited states in dependence on the protonation state and the
excite state decay mechanism is revealed.
Acknowledgement: This work was financially supported by the
Studienstiftung des deutschen Volkes (M.W.), the Fonds der
Chemischen Industrie (B.D.) and the Thüringer Ministerium für
Bildung, Wissenschaft und Kultur (Grant-No. B 514-09049,
PhotoMIC).
references:
1. Bräutigam, M.; Wächtler, M.; Rau, S.; Popp, J.; Dietzek,
B. Journal of Physical Chemistry C 2012, 116, 1274.
2. Kupfer, S.; Guthmuller, J.; Wächtler, M.; Losse, S.;
Rau, S.; Dietzek, B.; Popp, J.; Gonzalez, L. Physical
Chemistry Chemical Physics 2011, 13, 15580.
3. Wächtler, M.; Kupfer, S.; Guthmuller, J.; Popp, J.;
Gonzalez, L.; Dietzek, B. Journal of Physical Chemistry C
2011, 115, 24004.
Keywords: Ruthenium; Photophysics; time-resolved
spectroscopy; computational chemistry; protonation;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc