A Three‐Dimensional Structural Model for Predicting Magnetic Exchange and Hydrogen Positions in Bis‐μ‐Hydroxido Cu(II) Dimers

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The magnetic properties of bis‐μ‐hydroxido copper(II) complexes were investigated with a focus on the correlation between structural parameters and exchange coupling constants ( J ). Beyond the classical Cu‐O‐Cu bridging angle ( θ ), we examined the hydroxido hydrogen out‐of‐plane angle ( α ) as a critical parameter. Using BS‐DFT calculations and J ‐decomposition analysis on a benchmark complex, we showed that the kinetic exchange contribution governs the α‐dependence of magnetic coupling. A three‐dimensional magneto‐structural correlation incorporating both θ and α was developed and validated against 22 structurally diverse dimers spanning ferromagnetic to antiferromagnetic regimes. Our model achieved a 15‐fold improvement in predictive accuracy and correctly reproduced the sign of J in all cases. Notably, it enables estimation of the out‐of‐plane angle α , and thus the bridging hydrogen positions, often unresolved in X‐ray diffraction data. Our findings highlight that bridging hydrogen position uncertainties are a major error source in computational magnetochemistry, offering a refined approach to predict magnetic behavior and enhance computational accuracy.

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