Description
This contribution will present applications of soft and tender X
ray absorption
spectroscopy (XAS) and resonant inelastic X ray scattering (RIXS) to small molecules in
solution to probe their electronic charge density by and of quantum chemical modeling. T his
information allows to correlate charge density and molecular structure in order to understand
their interplay and thereby inform on basic principles of chemical bonding as well as light
induced reactions.
Heteroatoms in small organic molecules strongly influence function and chemical
reactivity. Such atoms, thus, present good targets of element specific probes such as X ray
absorption and emission spectroscopy. XAS is not only specific to a chemical element but also
to its chemical environment, allowing to distinguish bon order and valence charge differences
of atoms of a particular element. RIXS as a form of resonant Raman scattering can provide
vibrational and valence excitation spectra from tens of meV to tens of eV. Applications of XAS
and RIXS to core level resonances of nitrogen and sulfur atoms in fully solvated organic
molecules provide observables that can be compared to quantum chemical simulations. In
combination with pulsed ultraviolet (UV) lasers , time resolved spectroscopy enables spectral
measurement of transient photoproducts to study photochemical reaction pathways with
elemental specificity.
The molecules that were studied include formamides
1 (as important solvents and building
blocks of peptides), diazines diazines23 4 5 (as building blocks of molecules important in biological
contexts such as DNA) and disulfides disulfides6 (containing a sulfur sulfur bond which represents an
important bond motif in proteins and materials).
