The central role of the metal ion for photoactivity: Zn- Ni-Mabiq.

Photoredox catalysts are integral components of artificial photosystems, and have recently emerged as powerful tools for catalysing numerous organic reactions. However, the development of inexpensive and efficient earth-abundant photoredox catalysts remains a challenge. We here present the photochemical and photophysical properties of a Ni-Mabiq catalyst ([Ni(Mabiq)]OTf (); Mabiq = 2-4:6-8-bis(3,3,4,4-tetramethyldihydropyrrolo)-10-15-(2,2-biquinazolino)-[15]-1,3,5,8,10,14-hexaene1,3,7,9,11,14-N)-and of a Zn-containing analogue ([Zn(Mabiq)OTf] ())-using steady state and time resolved optical spectroscopy, time-dependent density functional theory (TDDFT) calculations, and reactivity studies.

Tuning the Ground and Excited State Dynamics of Hemithioindigo Molecular Motors by Changing Substituents.

Efficiency and performance of light triggered molecular motors are crucial features that need to be mechanistically understood to improve the performance and enable conscious property tailoring for specific applications. In this work, three different hemithioindigo-based molecular motors are investigated and all four steps in their complete unidirectional rotation are unraveled fully quantitatively. Transient absorption spectroscopy across twelve orders of magnitude in time is used to probe the fs nuclear motions up to the ms thermal kinetics, covering the timeframe of the whole motor rotation.

Icelike Vibrational Properties of Strong Hydrogen Bonds in Hydrated Lithium Nitrate.

The hydrogen bond network accounts for many of the extraordinary physical properties of liquid water and ice. Its vibrational dynamics are quite complex in their entirety but can be accessed in detail by investigating small groups of only a few water molecules. Here, aqueous salt hydrates turned out to be an exceptional model system for water molecules arranged in well-defined geometrical structures that can be accessed by means of femtosecond spectroscopy of the OH stretching vibration.

Space- and time-resolved UV-to-NIR surface spectroscopy and 2D nanoscopy at 1 MHz repetition rate.

We describe a setup for time-resolved photoemission electron microscopy with aberration correction enabling 3 nm spatial resolution and sub-20 fs temporal resolution. The latter is realized by our development of a widely tunable (215-970 nm) noncollinear optical parametric amplifier (NOPA) at 1 MHz repetition rate. We discuss several exemplary applications.

Octave-spanning single-cycle middle-infrared generation through optical parametric amplification in LiGaS.

We report the generation of extremely broadband and inherently phase-locked mid-infrared pulses covering the 5 to 11 µm region. The concept is based on two stages of optical parametric amplification starting from a 270-fs Yb:KGW laser source. A continuum seeded, second harmonic pumped pre-amplifier in β-BaBO (BBO) produces tailored broadband near-infrared pulses that are subsequently mixed with the fundamental pump pulses in LiGaS (LGS) for mid-infrared generation and amplification.