Predicting the spin state of paramagnetic iron complexes by DFT calculation of proton NMR spectra

Many transition-metal complexes easily change their spin state S in response to external perturbations (spin crossover). Determining such states and their dynamics can play a central role in the understanding of useful properties such as molecular magnetism or catalytic behavior, but is often far from straightforward. In this work we demonstrate that, at a moderate computational cost, density functional calculations can predict the correct ground spin state of Fe(ii) and Fe(iii) complexes and can then be used to determine the (1)H NMR spectra of all spin states. Since the spectral features are remarkably different according to the spin state, calculated (1)H NMR resonances can be used to infer the correct spin state, along with supporting the structure elucidation of numerous paramagnetic complexes.

Towards an accurate and computationally-efficient modelling of Fe(ii)-based spin crossover materials

A theoretical approach is proposed to accurately calculate the LS–HS energy gap of SCO complexes in the solid state.

Monte-Carlo simulations of spin-crossover phenomena based on a vibronic Ising-like model with realistic parameters

A new vibronic Ising-like model considering harmonic stretching-and-bending intermolecular interactions with realistic parameters describes thermal hysteresis in spin-crossover phenomena well.

Valence tautomeric dinuclear adducts of Co(ii) diketonates with redox-active diquinones for the design of spin qubits: computational modeling

DFT calculations performed on dinuclear adducts of Co(ii) diketonates with redox-active diquinones showed that with the proper structural tuning of the ligands, these paramagnetic complexes possess the properties required in a 2-qubit molecular system.

Spin crossover with thermal hysteresis: practicalities and lessons learnt

Memory applications of spin crossover require bistability: magnetic data must be appropriately collected and reported, and consideration given to lifetimes.

The effect of nitrido, azide, and nitrosyl ligands on magnetization densities and magnetic properties of iridium PNP pincer-type complexes

The magnetisation density of different iridium PNP pincer-type complexes depends on the chosen quantum chemistry method.

Charge transport properties of spin crossover systems

The study of spin crossover compounds by means of theoretical or experimental approaches has provided interesting results in recent decades. The main feature of such compounds is the change in the spin state induced by many different external stimuli, i.e. temperature, light, pressure, solvent coordination and the electric field. Spin crossover systems are potentially more useful than other magnetic molecules because their switching behaviour can occur closer to room temperature, and they are thus candidates for use in spintronic devices. Here, I review the state of the art in quantum chemical approaches to the study of such systems and discuss experiments that have focused on transport properties in single-molecule, nano-objects or thin-film spin crossover systems.

Spin-crossover behavior in two new supramolecular isomers

Two spin-crossover (SCO) supramolecular isomers formulated as [Fe(Mebpt){Au(CN)2}]n·xH2O (1, x = 0, and 2·H2O, x = n, MebptH = 3-(5-methyl-2-pyridyl)-5-(2-pyridyl)-1,2,4-triazole) have been successfully isolated and characterized by single-crystal X-ray crystallography, thermogravimetric analysis, differential scanning calorimetry, variable-temperature powder X-ray diffraction, and magnetic measurements. Structural analysis reveals that 1 is a two-dimensional coordination layer and 2·H2O is a one-dimensional coordination ladder structure, in which the Mebpt(-) ligands are coordinated in trans and cis bridging mode in 1 and 2·H2O, respectively. Dramatically, their SCO properties are further influenced by the octahedral coordination configuration of Fe(II). In 1, only the Fe(II) centers in trans configuration exhibit spin transition (Tc = 303 K), while in 2·H2O and the dehydrated 2, gradual two-step SCO (Tc1 = 235 K, Tc2 = 313 K) and one-step SCO behaviors (Tc = 315 K) occur, respectively.

Predicting paramagnetic 1H NMR chemical shifts and state-energy separations in spin-crossover host–guest systems

The behaviour of metal–organic cages upon guest encapsulation can be difficult to elucidate in solution.