TY - JOUR

T1 - Spin-state-correlated optical properties of copper(II)-nitroxide based molecular magnets

AU - Barskaya, Irina Yu

AU - Veber, Sergey L.

AU - Suturina, Elizaveta A.

AU - Sherin, Peter S.

AU - Maryunina, Kseniya Yu

AU - Artiukhova, Natalia A.

AU - Tretyakov, Evgeny V.

AU - Sagdeev, Renad Z.

AU - Ovcharenko, Victor I.

AU - Gritsan, Nina P.

AU - Fedin, Matvey V.

N1 - Publisher Copyright: © 2017 The Royal Society of Chemistry.

PY - 2017/10/3

Y1 - 2017/10/3

N2 - Molecular magnets based on copper(ii) ions and stable nitroxide radicals exhibit promising switchable behavior triggered by a number of external stimuli; however, their spin-state-correlated optical properties vital for photoinduced switching have not been profoundly investigated to date. Herein, the electronic absorption spectra of single crystals of three representatives of this unique family are studied experimentally and theoretically in the visible and near-IR regions. We established that the color of the complexes is mainly determined by optical properties of the nitroxide radicals, whereas the Cu(hfac)2 fragment contributes to the near-IR range with the intensity smaller by an order of magnitude. The thermochromism of these complexes evident upon thermal spin state switching is mainly caused by a spectral shift of the absorption bands of the nitroxides. The vibrational progression observed in the visible range for single crystals as well as for solutions of pure nitroxides is well reproduced by DFT calculations, where the C-C stretching mode governs the observed progression. The analysis of the spectra of single crystals in the near-IR region reveals changes in the energy and in the intensity of the copper(ii) d-d transitions, which are well reproduced by SOC-NEVPT2 calculations and owe to the flip of the Jahn-Teller axis in the coordination environment of copper. Further strategies for designing bidirectional magnetic photoswitches using these appealing compounds are discussed.

AB - Molecular magnets based on copper(ii) ions and stable nitroxide radicals exhibit promising switchable behavior triggered by a number of external stimuli; however, their spin-state-correlated optical properties vital for photoinduced switching have not been profoundly investigated to date. Herein, the electronic absorption spectra of single crystals of three representatives of this unique family are studied experimentally and theoretically in the visible and near-IR regions. We established that the color of the complexes is mainly determined by optical properties of the nitroxide radicals, whereas the Cu(hfac)2 fragment contributes to the near-IR range with the intensity smaller by an order of magnitude. The thermochromism of these complexes evident upon thermal spin state switching is mainly caused by a spectral shift of the absorption bands of the nitroxides. The vibrational progression observed in the visible range for single crystals as well as for solutions of pure nitroxides is well reproduced by DFT calculations, where the C-C stretching mode governs the observed progression. The analysis of the spectra of single crystals in the near-IR region reveals changes in the energy and in the intensity of the copper(ii) d-d transitions, which are well reproduced by SOC-NEVPT2 calculations and owe to the flip of the Jahn-Teller axis in the coordination environment of copper. Further strategies for designing bidirectional magnetic photoswitches using these appealing compounds are discussed.

KW - ELECTRON-PARAMAGNETIC-RESONANCE

KW - ZETA VALENCE QUALITY

KW - GAUSSIAN-BASIS SETS

KW - PERTURBATION-THEORY

KW - NITRONYL NITROXIDE

KW - MAGNETOSTRUCTURAL TRANSITIONS

KW - BREATHING CRYSTALS

KW - IRON(II) COMPLEXES

KW - CROSSOVER SYSTEM

KW - ATOMS LI

UR - http://www.scopus.com/inward/record.url?scp=85030720417&partnerID=8YFLogxK

U2 - 10.1039/c7dt02719b

DO - 10.1039/c7dt02719b

M3 - Article

C2 - 28944812

AN - SCOPUS:85030720417

VL - 46

SP - 13108

EP - 13117

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 38

ER -