Enhanced bistability by guest inclusion in Fe(ii) spin crossover porous coordination polymers

Abstract

Inclusion of thiourea guest molecules in the tridimensional spin crossover porous coordination polymers {[Fe(pyrazine)[M(CN)(4)]} (M = Pd, Pt) leads to novel clathrates exhibiting unprecedented large thermal hysteresis loops of ca. 60 K wide centered near room temperature.

New Hofmann-like spin crossover compound with 3,5-lutidine

“…For material 2c with guest 3,5-lutidine species, another explanation about the outer high spin state sites may be possible such as π − π interactions between the ligands of 3,5-lutidine coordinated to iron(II) atoms and the guest molecules of 3,5-lutidine in 2D and 3D Hofmann-like coordination polymer compounds [10][11][12][13][14][15][16]. While 2c has the 2D host framework, guest 3,5-lutidine molecules probably have π − π interactions with ligand 3,5-lutidine species.…”

“…The related spin crossover coordination compounds have been developed [8][9][10][11][12][13][14][15][16][17][18]. Some of them contain 3D pillared Hofmann-type-organic frameworks [10][11][12][13][14][15][16].…”

High-Temperature Wide Thermal Hysteresis of an Iron(II) Dinuclear Double Helicate

“…There is a need for SCO materials which are capable of abrupt and complete HS-LS interconversion at around room temperature (RT) with wide thermal hysteresis width (∆T) for potential applications in molecular memories, switches, and display devices. As such, various cooperative SCO compounds have been produced with supramolecular assembly via intermolecular hydrogen bonding [8][9][10] and π-π stacking [11][12][13], or coordination polymeric architecture by using bridging ligands [14][15][16][17][18]. Multinuclear clusters have also been widely studied in the hope of developing multistable compounds with more accessible spin states towards denser information storage, or hybrid SCO materials with multifunctional properties (e.g., SCO with charge transfer, magnetic coupling, luminescence, etc.)…”

Disclosing the Ligand- and Solvent-Induced Changes on the Spin Transition and Optical Properties of Fe(II)-Indazolylpyridine Complexes

“…So far, the application of quantum chemistry to aid in this quest has been limited by the lack of an accurate and computationally-efficient methodology to work in the solid state of those compounds and, apart from few exceptions [6,[17][18][19][20], it has been essentially focused on the study of the individual molecules [21]. However, some advances have been made in the field and, especially, in the application of DFT + U to calculate the adiabatic energy difference between the LS and HS phases of SCO compounds in their unit cells, thus, accounting for all the crystal packing effects and weak interactions [22].…”

“…The idea of cooperativity is naively associated to the effect that a transiting SCO unit has on its neighbors during the transition with larger cooperativity values leading to abrupt or even hysteretic transitions. Consequently, dense networks have been designed in order to enhance cooperativity by means of strong covalent [6,7] or van der Waals interactions [8][9][10] between SCO molecules. However, even if few remarkable computational studies have dealt with the effect of crystal packing and cooperativity on SCO materials [11,12], (including phenomenological models [13,14]) progress in the field has been hindered by the difficulty of establishing general structure-function correlations in the solid state, which should incorporate the effect of counterions and solvent molecules beyond the SCO molecules itself (not to mention the importance of polymorphism [15,16]).…”