Selective Pathway toward Heteroleptic Spin-Crossover Iron(II) Complexes with Pyridine-Based N-Donor Ligands

Igor Nikovskiy; Dmitry Yu Aleshin; Valentin V Novikov; Alexander V Polezhaev; Ekaterina A Khakina; Elizaveta K Melnikova; Yulia V Nelyubina

doi:10.1021/acs.inorgchem.2c03270

Selective Pathway toward Heteroleptic Spin-Crossover Iron(II) Complexes with Pyridine-Based N-Donor Ligands

Inorg Chem. 2022 Dec 26;61(51):20866-20877. doi: 10.1021/acs.inorgchem.2c03270. Epub 2022 Dec 13.

Authors

Igor Nikovskiy^{1

2}, Dmitry Yu Aleshin¹, Valentin V Novikov^{2

3}, Alexander V Polezhaev², Ekaterina A Khakina^{1

4}, Elizaveta K Melnikova¹, Yulia V Nelyubina^{1

2}

Affiliations

¹ Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilova Str., 28, 119991Moscow, Russia.
² Bauman Moscow State Technical University, 2nd Baumanskaya Str., 5, 105005Moscow, Russia.
³ Moscow Institute of Physics and Technology, Institutskiy per., 9, 141700Dolgoprudny, Russia.
⁴ HSE University, Miasnitskaya Str., 20, 101000Moscow, Russia.

PMID: 36511893
DOI: 10.1021/acs.inorgchem.2c03270

Abstract

A new synthetic pathway is devised to selectively produce previously elusive heteroleptic iron(II) complexes of terpyridine and N,N'-disubstituted bis(pyrazol-3-yl)pyridines that stabilize the opposite spin states of the metal ion. Such a combination of the ligands in a series of the heteroleptic complexes induces the spin-crossover (SCO) not experienced by the homoleptic complexes of these ligands or shifts it to lower/higher temperatures respective to the SCO-active homoleptic complex. The midpoint temperatures of the resulting SCO span from ca. 200 K to the ambient temperature and beyond the highest temperature accessible by NMR spectroscopy and SQUID magnetometry. The proposed "one-pot" approach is applicable to other N-donor ligands to selectively produce heteroleptic complexes─including those inaccessible by alternative synthetic pathways─with highly tunable SCO behaviors for practical applications in sensing, switching, and multifunctional devices.