Guest Removal and External Pressure Variation Induce Spin Crossover in Halogen-Functionalized 2-D Hofmann Frameworks

Ashley T Brennan, Katrina A Zenere, Helen E A Brand, Jason R Price, Mohan M Bhadbhade, Gemma F Turner, Stephen A Moggach, Francisco J Valverde-Muñoz, Jose A Real, Jack K Clegg, Cameron J Kepert, Suzanne M Neville

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17 Citations (Scopus)

Abstract

The effect of halogen functionalization on the spin crossover (SCO) properties of a family of 2-D Hofmann framework materials, [FeIIPd(CN)4(thioX)2]·2H2O (X = Cl and Br; thioCl = (E)-1-(5-chlorothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine) and thioBr = (E)-1-(5-bromothiophen-2-yl)-N-(4H-1,2,4-triazol-4-yl)methanimine)), is reported. Inclusion of both the chloro- and bromo-functionalized ligands into the Hofmann-type frameworks (1 Cl ·2H 2 O and 2 Br ·2H 2 O) results in a blocking of spin-state transitions due to internal chemical pressure effects derived by the collective steric bulk of the halogen atoms and guest molecules. Cooperative one-step SCO transitions are revealed by either guest removal or the application of external physical pressure. Notably, removal of solvent water reveals a robust framework scaffold with only marginal variation between the solvated and desolvated structures (as investigated by powder and single crystal X-ray diffraction). Yet, one-step complete SCO transitions are revealed in 1 Cl and 2 Br with a transition temperature shift between the analogues due to various steric, structural, and electronic considerations. SCO can also be induced in the solvated species, 1 Cl ·2H 2 O and 2 Br ·2H 2 O, with the application of physical pressure, revealing a complete one-step SCO transition above 0.62 GPa (as investigated by magnetic susceptibility and single crystal X-ray diffraction measurements).

Original languageEnglish
Pages (from-to)14296-14305
Number of pages10
JournalInorganic Chemistry
Volume59
Issue number19
DOIs
Publication statusPublished - 5 Oct 2020

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