A new spin crossover Fe^II coordination environment in a two-fold interpenetrated 3-D Hofmann-type framework material

Abstract

Spin-crossover is observed for the first time in a FeII(py)3(NC⋯)3 coordination environment which arises in a two-fold interpenetrated 3-D Hofmann-like framework.

Spin-Crossover 2-D Hofmann Frameworks Incorporating an Amide-Functionalized Ligand: N-(pyridin-4-yl)benzamide

“…These water molecules were engaged in a range of host-guest hydrogen-bonding interactions with the amide group of the benpy ligands ( Figure 7). Similar arrays of host-guest interactions involving amide functional groups have been observed in other SCO frameworks [26][27][28][29][30]. Figures S18 and S19) matched the transition temperature anticipated from magnetic susceptibility.…”

“…We utilized the ligand N-(pyridin-4-yl)benzamide (benpy; Figure 1) [25] to facilitate SCO cooperativity via both hydrogen bonding from the amide functional group and aromatic contacts via the aromatic rings ( Figure 1). Amide-functionalized ligands were successfully applied to a range of SCO framework previously, resulting in a range of interesting structures and SCO features [26][27][28][29][30] based on interaction with the amide group. Here, we report the structure and SCO properties of the 2-D Hofmann frameworks' analogues [Fe II (benpy)2(M(CN)4)] (M = Pd and Pt) with an interest in the impact of amide group contacts on the structure and cooperativity of the spin-state transition.…”

Guest-Induced Multistep-to-One-Step Reversible Spin Transition with Enhanced Hysteresis in a 2D Hofmann Framework

“…The largest Raman shift between the different spin states was observed in the range of ν CN = ∼2160−2210 cm −1 , which agrees well with literature reports on the Hofmann framework. 71,72 The well-resolved doublet peaks corresponding to the symmetric and asymmetric stretching modes of the CN groups in the 2D Hofmann layer 54 (Figure 6) shift to lower wavenumber, while the spin states change from 60% LS/ 40% HS state (red, 100 K) to 100% HS state (orange, 300 K) with an increase in the temperature. The relative intensity of the band peaks also decreased with a change in the spin state from a fractional HS/LS state (green, 140 K) to a completely HS state (red, 300 K) (Figure S21).…”

Guest-Induced Multistep to Single-Step Spin-Crossover Switching in a 2-D Hofmann-Like Framework with an Amide-Appended Ligand

“…Motivated by these findings, here, we use a functionalized 4-pyridyl ligand with tailored supramolecular contact sites via an amide functional group, N -(pyridin-4-yl)­furan-2-carboxamide (furpy; see Figure ). The use of amide functional groups to support hydrogen bonding in SCO frameworks has been reported previously, in some cases, the amide-driven supramolecular network improves SCO cooperativity, , and, in another recent case, drove the formation of an irregular 3-D Hofmann framework and a novel Fe II SCO coordination environment . Previous studies including amide ligands have focused on 3-D frameworks, in this study, we present a 2-D Hofmann framework that shows substantial structural flexibility in both the framework components and the guest, allowing a detailed investigation of guest-induced multistep on–off switching.…”

“…The furpy ligand was used to prepare a 2-D Hofmann framework with an array of host–host and host–guest interactions, because of the presence of an amide group. Amide bonds are known to induce hydrogen bonding and have been employed in several studies of SCO frameworks to this end . The presence of competing host–host and host–guest interactions has been a successful approach to inducing structural distortion in Hofmann frameworks and a range of multistep SCO behaviors …”