How do low spin complexes generally relate to the spectrochemical series?

Low spin complexes are associated with ligands that are high in the spectrochemical series. This is because high-field ligands, such as CN⁻, CO, and NH₃, generate a strong crystal field splitting energy (Δ). When these strong field ligands surround a metal ion in a complex, they cause the d-orbitals of the metal to split into different energy levels significantly. This results in a larger energy difference between the lower-energy and higher-energy d-orbitals.

In the presence of a sufficiently large Δ, the energy required to pair electrons in the lower-energy orbitals is less than the energy required to promote electrons to the higher-energy orbitals. Therefore, electrons will fill the lower-energy orbitals completely before any are promoted to the higher ones, leading to a low spin configuration.

This relationship underscores the importance of the nature of the ligands in determining the electronic structure of the complex. So, low spin complexes are characterized by having strong field ligands present, which aligns with their position at the higher end of the spectrochemical series.