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Intermolecular Interaction Tuning of Spin-Crossover Iron(III) Complexes with Aromatic Counteranions

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journal contribution
posted on 2018-02-20, 18:43 authored by Asami Tsukiashi, Manabu Nakaya, Fumiya Kobayashi, Ryo Ohtani, Masaaki Nakamura, Jack M. Harrowfield, Yang Kim, Shinya Hayami
Iron­(III) spin-crossover (SCO) complexes [Fe­(qsal)2]­BS·MeOH·H2O (1), [Fe­(qsal)2]­(NS)·MeOH (2), [Fe­(qnal)2]­(NS) (3), and [Fe­(qnal)2]­PS·MeOH·CH2Cl2 (4) (Hqsal, N-(8-quinolinyl)­salicylaldimine; Hqnal, N-(8-quinolinyl)-2-hydroxy-1-naphthaldimine; BS, benzenesulfonate; NS, 1-naphthalenesulfonate; PS, 1-pyrenesulfonate) have been synthesized and characterized by X-ray structure determinations and temperature-dependent magnetic susceptibility measurements. The aromatic counteranions BS, NS, and PS can be used for the tuning of intermolecular coupling through a variety of weak interactions. All of the complexes show temperature-dependent SCO behavior. but the light-induced excited spin-state trapping (LIESST) effect was observed only for 1, 3, and 4 when the samples were illuminated (λ 808 nm) for 1 h at 5 K. In particular, 59% of the LS form of 1 was converted to the metastable HS state by illumination, equal to the highest degree of conversion yet known for LIESST in [Fe­(qsal)2]+ derivatives. The lack of a LIESST effect for 2 may be due to the relatively limited degree of interaction between the cations and anions in the lattice, reflected in a much longer minimum Fe···Fe separation in this complex in comparison to the others.

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