Obesity and overweight are associated with lethal diseases. In this context, obese and overweight individuals infected by COVID-19 are at greater risk of dying. Obesity is treated by three main pharmaceutical approaches, namely suppressing appetite, reducing energy intake by impairing absorption, and increasing energy expenditure. Most compounds used for the latter were first envisaged for other medical uses. However, several candidates are now being developed explicitly for targeting obesity by increasing energy expenditure. This review analyzes the compounds that show anti-obesity activity exerted through the energy expenditure pathway. They are classified on the basis of their development status: FDA-approved, Withdrawn, Clinical Trials, and Under Development. The chemical nature, target, mechanisms of action, and description of the current stage of development are described for each one.

The electronic and magnetic properties of ferrous iron in the iron(II)‐2,3,9,10,16,17,23,24‐octakis(2,6‐diisopropylphenoxy)phthalocyanine (FePc^OAr), exhibiting a true square‐planar molecular environment, are investigated. Inhibition of intermolecular interactions by steric substituents allows detailed investigation of the electronic structure arising from the planar geometry of the d⁶ electron configuration. Complementary magnetometry, Mössbauer, FD‐FT THz‐EPR (frequency‐domain Fourier‐transform terahertz electron paramagnetic resonance) and pNMR (nuclear magnetic resonance of paramagnetic molecules) spectroscopies show that FePc^OAr has an S = 1 ground state with large positive axial zero‐field splitting (ZFS) and a strongly anisotropic g‐tensor, with two g‐values much larger than the free electron g‐value and one smaller. Correlation between the magnetic properties and the electronic structure is provided by high‐level quantum chemical calculations. The calculations indicate a nearly triply degenerate ground level, in which spin‐orbit coupling mixes the isolated ³A_2g ground state with two excited ³E_g states, whose energy gaps to the ground state are almost identical. These findings provide valuable insights in the electronic structure of iron phthalocyanines and the long‐standing discussion on their true electronic ground level, which has important implications for the application of this important class of complexes in catalysis and magnetic materials.

Magnetic beam deflection shows an enhanced g -factor for Sn ₁₂ Fe. CASSCF calculations reveal the multi-reference character of Sn ₁₂ Fe and charge transfer from Sn 5p to Fe 3d orbitals. Spin–orbit contributions of the Sn atoms enhance the g -factor.

Mössbauer spectroscopy is a key method for characterizing the electronic structures of iron compounds. The resulting Mössbauer parameters show a well-established temperature dependence. For quantum chemical calculations that are often used to aid in the interpretation of Mössbauer spectra, this poses a major challenge: they commonly employ a single, rigid equilibrium structure that is assumed to deliver good results for low temperatures up to ca. 80 K. In this work, we reveal this approach to be a rather severe approximation. We use a structural sampling approach that captures the effect of temperature dependent molecular vibrations on the quadrupole splitting. Even for low temperatures, this approach delivers a significantly improved agreement with experimental data. In addition, the T-dependence of the quadrupole splitting can be qualitatively reproduced for four iron(II) high spin complexes. The results are analyzed in terms of the individual EFG tensor contributions, which shows the origin of the temperature dependence being rooted in different electronic structures with varying contributions at different temperatures. Limitations in the sampling approach and electronic structure method are discussed. The approach presented herein may provide better agreement with experiment in future in situ and operando studies at low, ambient and elevated temperatures.