Hoogspin

Hoogspin is a term used in Dutch to describe a high-spin electronic configuration in atoms or coordination complexes. It indicates that the electrons occupy a larger number of unpaired spins than in a low-spin state, usually because the ligand field is weak or the exchange energy is dominant. Hoogspin is commonly discussed in contrast with laagspin, where electrons pair up in lower-energy orbitals, resulting in fewer unpaired spins.

In coordination chemistry, hoogspin most often appears in octahedral or other coordination environments of transition metals when ligands exert a weak crystal-field splitting. For example, certain first-row transition metals with weak-field ligands can adopt hoogspin configurations, leading to higher magnetic moments and different bond lengths compared with their laagspin counterparts. The specific spin state has consequences for reactivity, color, and spectroscopic properties of the complex.

Magnetic and spectroscopic implications are central to the concept. Hoogspin species typically exhibit higher paramagnetic moments due to unpaired electrons and can show characteristic electronic transitions in their UV–visible spectra that differ from laagspin complexes. In some materials and complexes, temperature- or pressure-induced transitions between hoogspin and laagspin states occur, a phenomenon studied under spin crossover.

Outside coordination chemistry, hoogspin terms are also used in solid-state chemistry and physics to describe high-spin states of ions in lattices or clusters, where collective magnetic behavior is of interest.