Photoinduced Low Spin to High Spin Transition in a [2x2] Fe(II) Metallogrid: Diode Laser-Pumped Photocrystallography at the P11 Beamline in PETRA III, DESY

TL;DR

This study demonstrates the first use of beamline P11 at PETRA III for photocrystallography to observe photoinduced spin state transitions in a Fe(II) metallogrid, utilizing a compact diode laser system for precise photoexcitation.

Contribution

It introduces a novel experimental setup combining a compact diode laser with synchrotron photocrystallography to study photoinduced spin crossover in molecular crystals.

Findings

Successful observation of spin crossover from 2HS-2LS to 3HS-1LS states.

Significant changes in Fe-N bond lengths consistent with spin state transition.

Demonstration of a portable laser setup suitable for synchrotron photocrystallography.

Abstract

We report on the photoinduced spin crossover (SCO) transition from a 2HS-2LS to a 3HS-1LS state in a [2x2] Fe(II) metallogrid complex using molecular crystals with static photocrystallography at a first ever attempt in the beamline P11 of the PETRA III synchrotron, DESY. A class 3B diode laser was used to induce the transition under controlled irradiation conditions. Structural characterization was achieved through single-crystal X-ray diffraction (SCXRD) measurements post-irradiation, revealing significant changes in average Fe-N distances, consistent with SCO behavior. Our experimental setup enables precise alignment necessary for photo-excitation using a class 3B diode laser along with a compact focusing optics. The longest dimension of the combined setup of the diode head and the focusing optics is not more than 32cm. The setup showcasing the utility of a compact diode laser system which can even be conveniently used in synchrotron-based pump-probe photocrystallography experiments for a wide range of molecular crystals.