Photoinduced spin crossover in Fe-picolylamine complex: A farinfrared study on single crystals

TL;DR

This study uses far-infrared spectroscopy with synchrotron radiation to investigate molecular vibrational changes in Fe-picolylamine crystals during photoinduced and temperature-induced spin crossovers, revealing ligand involvement.

Contribution

It provides new insights into the microscopic differences between photoinduced and temperature-induced high-spin states through vibrational analysis.

Findings

FeN6 cluster vibrations change with spin state transitions.

Ligand vibrations differ markedly between the two high-spin states.

Ligand interactions likely influence the spin crossover mechanism.

Abstract

Far-infrared spectroscopy has been performed on [Fe(2-picolylamine)3]Cl2EtOH (Fe-pic) single crystals, to probe changes in the molecular vibrations upon the photoinduced and temperature-induced spin crossovers. Synchrotron radiation has been used as the farinfrared source to overcome the strong absorption and the small sizes of the samples. Absorption lines due to FeN6 cluster vibrations, observed below 400 cm-1, show strong intensity variations upon the crossover due to the deformation of FeN6 between high-spin and low-spin states. However, they remain almost unchanged between the photo- and temperature-induced high-spin states. This is in sharp contrast to the lines at 500-700 cm-1 due to intramolecular vibrations of the picolylamine ligands, which show marked variations between the two high-spin states. It is concluded that the most important microscopic difference between the two high-spin states arises from the ligands, which is likely to reflect different states of intermolecular bonding between them.