Infrared study of spin crossover Fe-picolylamine complex

TL;DR

This study uses infrared spectroscopy with synchrotron radiation to analyze microscopic vibrational changes during temperature- and photo-induced spin crossover in Fe-picolylamine, revealing distinct differences in high-spin states.

Contribution

It provides detailed IR spectral analysis of spin crossover in Fe-pic, highlighting microscopic differences between temperature- and photo-induced high-spin states.

Findings

Large IR spectral changes between high-spin and low-spin states.

Distinct IR spectral features differentiate temperature- and photo-induced high-spin states.

Microscopic differences suggest different mechanisms for photo-induced and thermal spin crossover.

Abstract

Infrared (IR) absorption spectroscopy has been used to probe the evolution of microscopic vibrational states upon the temperature- and photo-induced spin crossovers in [Fe(2-picolylamine)3]Cl2EtOH (Fe-pic). To overcome the small sizes and the strong IR absorption of the crystal samples used, an IR synchrotron radiation source and an IR microscope have been used. The obtained IR spectra of Fe-pic show large changes between high-spin and low-spin states for both the temperature- and the photo- induced spin crossovers. Although the spectra in the temperature- and photo-induced high-spin states are relatively similar to each other, they show distinct differences below 750 cm-1. This demonstrates that the photo-induced high-spin state involves microscopically different characters from those of the temperature-induced high-spin state. The results are discussed in terms of local pressure and structural deformations within the picolylamine ligands, and in terms of their possible relevance to the development of macroscopic photo-induced phase in Fe-pic.