Molecular Spin Crossover Materials: Review of the Lattice Dynamical Properties

Abstract

Dedicated to the memory of Prof. John J. McGarveyThe lattice dynamical aspects of the spin crossover phenomenon in molecular solids-displaying intricate couplings between the electronic spin state of the molecules and the lattice properties-are reviewed. Emphasis is on experimental and theoretical approaches giving access to the vibrational spectra and to key properties, such as the heat capacity, vibrational entropy and enthalpy, lattice rigidity, elastic constants, and elastic interactions. Recent results in relation to surface and finite size effects as well as with ultrafast out-of-equilibrium phenomena are also covered.

Thermal spin crossover in Fe(ii) and Fe(iii). Accurate spin state energetics at the solid state

“…Some organometallic complexes based on d6-d9 transition metal ions undergo a spin-state switch in the presence of an external perturbation. [1][2][3][4][5][6][7][8] These molecules, called Spin Crossover (SCO), are prototypical class of molecular magnetic switches, 9 and are regarded as interesting for a range of technological applications. [10][11][12][13] A key property of SCO materials is the temperature at which the spin transition occurs, called transition temperature ( 1/2 ), as it defines their potential applicability in real-life devices operating at mild temperatures.…”

“…With this in mind, the motivation of the present paper is, first, to (i) benchmark U under an improved dispersion correction scheme (D3 and D3-BJ) and, second, to (ii) extend the application of the PBE+U scheme to the family of Fe III SCO compounds. To do so, we have benchmarked the U parameter for five Fe II compounds (1)(2)(3)(4)(5), and four Fe III SCO compounds (6)(7)(8)(9). This benchmark is then complemented with gas-phase computations employing a range of DFT functionals.…”

Biased Spin-State Energetics of Fe(II) Molecular Complexes within Density-Functional Theory and the Linear-Response HubbardUCorrection

“…[1][2][3][4][5][6][7][8] Achieving such a description with chemical accuracy appears today as a significant challenge for ab initio methods with strong implications in future assistance and guidance of experimental efforts devoted to the (i) development and optimization of catalytic reactivity and the (ii) design of novel spin crossover (SCO) complexes. The vast majority of SCO materials, which are of great interest for applications such as molecular spintronics, molecular electronics, sensors and actuators, [9][10][11][12] are octahedrallycoordinated Fe(II)-based molecular complexes. For these complexes, the thermodynamics of the spin transition (i.e.…”

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

“…However, for Pd(benpy) the degree of distortion was seen to increase over the HS to LS transition (HS = 8.16° and LS = 13.20°) and for Pt(benpy) there was no substantial change over the SCO transition. This is often an indicator of elastic frustration [46][47][48][49][50], which arises from a competition between interactions and the volumetric change over the spin-state transition. In most cases, this results in multi-stepped SCO transitions, but here the cooperative one-step transition suggests that there was a degree of elastic frustration.…”