Abstract: Magnetic susceptibility measurement of metal complexes is a classic experiment in undergraduate physical chemistry courses, traditionally performed using a Gouy magnetic balance to determine the electron configuration of the central ion. This process is closely related to the theoretical framework of crystal field theory. To enhance students’ understanding of the impact of electronic structure on the the microstructure and stability of the complexes, computational chemistry methods have been integrated into this experiment. Using Gaussian software, the high-spin and low-spin electronic configurations of the central ions in FeSO₄·7H₂O and K₄Fe(CN)₆·3H₂O were calculated. This approach transforms the abstract and complex concept of electronic arrangements into a tangible comparison of energy and bond length, where the lower energy configuration corresponds to the more favorable spin state. Additionally, the optimized geometries from the calculations were compared with single-crystal X-ray diffraction data to validate the stable structures. By bridging experimental results, computational findings, and theoretical knowledge, this improved experiment cultivates students' ability to integrate experimental and theoretical approaches and to connect macroscopic observations with microscopic insights. Furthermore, it inspires senior undergraduates to engage more deeply in experimentation and enhances their comprehensive experimental skills.

Key words: Crystal field theory, Metal complexes, Gouy method, Computational chemistry, Experimental improvement