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Issue 1, 2015
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Spin-crossover in phenylazopyridine-functionalized Niporphyrin: trans–cis isomerization triggered by π–π interactions

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Abstract

Reversible, room-temperature light-induced spin-crossover has been reported in a Niporphyrin functionalized with a phenylazopyridine (PAPy) ligand (Venkataramani et al., Science, 2011, 331, 445). Upon light irradiation (500 nm), the azopyridine moiety induces a change in the Ni(II) coordination sphere from square planar (n = 4) to square pyramid (n = 5), leading to a change in the total spin of the molecule from S = 0 to S = 1. The trans–cis isomerization in the azopyridine ligand has been proposed to trigger the spin-crossover effect. However, the radiation used to induce the HS state is about 135 nm red-shifted with respect to the radiation used for trans–cis isomerization of the N[double bond, length as m-dash]N double bond in other compounds. To elucidate the light-induced spin-crossover mechanism of this Ni(II) compound, a combined DFT/CASSCF/CASPT2 study has been performed to determine the most stable cis and trans conformers with n = 4 or n = 5, and to characterize the excitation that triggers the SCO process. ππ interactions between porphyrin and PAPy are shown to play an essential role in the spin crossover.

Graphical abstract: Spin-crossover in phenylazopyridine-functionalized Ni–porphyrin: trans–cis isomerization triggered by π–π interactions

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Publication details

The article was received on 29 Sep 2014, accepted on 30 Oct 2014 and first published on 03 Nov 2014


Article type: Paper
DOI: 10.1039/C4CP04402A
Author version available: Download Author version (PDF)
Citation: Phys. Chem. Chem. Phys., 2015,17, 217-225
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    Spin-crossover in phenylazopyridine-functionalized Niporphyrin: trans–cis isomerization triggered by π–π interactions

    G. Alcover-Fortuny, C. de Graaf and R. Caballol, Phys. Chem. Chem. Phys., 2015, 17, 217
    DOI: 10.1039/C4CP04402A

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