CO-actuated spin transition tuning in an interdigitated Hofmann-type coordination polymer.

The increased anthropogenic emission level of CO urges the development of CO-responsive materials, but is it possible to regulate the inherent electronic properties through weak physisorption of a ubiquitous gas such as CO? Herein, we intended to answer this imperative question by the first case of CO-actuated variable spin-state stabilisation in an interdigitated Hofmann-type coordination polymer [FePd(CN)L] (1, L = methyl isonicotinate), showing a wide shift in transition temperature ( ) from 178 K at = 0 kPa to 229 K at = 100 kPa. Interestingly, the emergence of a stepped behaviour in the heating process below = 10 kPa and overlapping magnetic susceptibility values above = 10 kPa elucidate the selective LS state stabilisation solely correlated with the extent of CO accommodation. Based on the magnetic response and phase transition diagrams obtained under respective , a plausible scenario of the spin-state switching can be interpreted as (1 + ) → (1 + ) → 1 at ≤ 10 kPa, → 1 at 100 kPa < ≥ 32 kPa and → → 1 at 100 kPa, where 1 and 1' represent CO-free and CO-encapsulated states, respectively.