Structural dynamics upon photoexcitation-induced charge transfer in a dicopper(i)-disulfide complex
Artikel i vetenskaplig tidskrift, 2018

The structural dynamics of charge-transfer states of nitrogen-ligated copper complexes has been extensively investigated in recent years following the development of pump-probe X-ray techniques. In this study we extend this approach towards copper complexes with sulfur coordination and investigate the influence of charge transfer states on the structure of a dicopper(i) complex with coordination by bridging disulfide ligands and additionally tetramethylguanidine units [Cu I 2 (NSSN) 2 ] 2+ . In order to directly observe and refine the photoinduced structural changes in the solvated complex we applied picosecond pump-probe X-ray absorption spectroscopy (XAS) and wide-angle X-ray scattering (WAXS). Additionally, the ultrafast evolution of the electronic excited states was monitored by femtosecond transient absorption spectroscopy in the UV-Vis probe range. DFT calculations were used to predict molecular geometries and electronic structures of the ground and metal-to-ligand charge transfer states with singlet and triplet spin multiplicities, i.e. S 0 , 1 MLCT and 3 MLCT, respectively. Combining these techniques we elucidate the electronic and structural dynamics of the solvated complex upon photoexcitation to the MLCT states. In particular, femtosecond optical transient spectroscopy reveals three distinct timescales of 650 fs, 10 ps and > 100 ps, which were assigned as internal conversion to the ground state (S n → S 0 ), intersystem crossing 1 MLCT → 3 MLCT, and subsequent relaxation of the triplet to the ground state, respectively. Experimental data collected using both X-ray techniques are in agreement with the DFT-predicted structure for the triplet state, where coordination bond lengths change and one of the S-S bridges is cleaved, causing the movement of two halves of the molecule relative to each other. Extended X-ray absorption fine structure spectroscopy resolves changes in Cu-ligand bond lengths with precision on the order of 0.01 Å, whereas WAXS is sensitive to changes in the global shape related to relative movement of parts of the molecule. The results presented herein widen the knowledge on the electronic and structural dynamics of photoexcited copper-sulfur complexes and demonstrate the potential of combining the pump-probe X-ray absorption and scattering for studies on photoinduced structural dynamics in copper-based coordination complexes.

Författare

M. Naumova

Universität Paderborn

Universität Hamburg

Deutsches Elektronen-Synchrotron (DESY)

Dmitry Khakhulin

European XFEL

Universität Hamburg

Mateusz Rebarz

Czech Academy of Sciences

Martin Rohrmüller

Universität Paderborn

B. Dicke

Deutsches Elektronen-Synchrotron (DESY)

Universität Hamburg

M. Biednov

Deutsches Elektronen-Synchrotron (DESY)

Universität Hamburg

Alexander Britz

Universität Hamburg

European XFEL

Shirly Espinoza

Czech Academy of Sciences

B. Grimm-Lebsanft

Universität Hamburg

Deutsches Elektronen-Synchrotron (DESY)

Miroslav Kloz

Czech Academy of Sciences

Norman Kretzschmar

European Synchrotron Radiation Facility (ESRF)

Adam Neuba

Universität Paderborn

Jochen Ortmeyer

Max Planck-institutet

Universität Paderborn

Roland Schoch

Universität Paderborn

Jakob Andreasson

Chalmers, Fysik, Kondenserade materiens fysik

Uppsala universitet

Czech Academy of Sciences

Matthias Bauer

Universität Paderborn

C. Bressler

European XFEL

Universität Hamburg

Wolf Gero Schmidt

Universität Paderborn

Gerald Henkel

Universität Paderborn

M. Rübhausen

Deutsches Elektronen-Synchrotron (DESY)

Universität Hamburg

Physical Chemistry Chemical Physics

1463-9076 (ISSN) 1463-9084 (eISSN)

Vol. 20 9 6274-6286

Ämneskategorier

Oorganisk kemi

Atom- och molekylfysik och optik

Teoretisk kemi

DOI

10.1039/c7cp04880g

PubMed

29431759