Spin State Switching Triggered by Light

The influence of non-coordinating anions and spacer length of the ligand is analysed in extension of the systematic investigations into iron(II) spin cossover coordination polymers. Ditetrazole complexes of iron(II) perchlorate, tetrafluoroborate and hexafluorophosphate where the two tetrazole moieties are separated by alkylene spacers with different number of carbon atoms (n) are presented. Pronounced structural, optical, magnetic and magneto- optical changes are analysed and found in the comparison of the two series.The results allow a deeper insight in coherences between structural changes and electronic occupations, which can be detected as thermal, optical or magnetic spin transitions.