The Ho-(DBM) 3 • H 2 O complex was synthesized by modification of the method used in a previous report. Sodium ethoxide (82.6 mg, 1.2 mmol) in ethanol (10 ml) was added to dibenzoylmethane (1.60 g, 1.2 mmol) in ethanol (50 ml). The mixture was stirred for 30 min at 78 • C, and HoCl 3 • 6 H 2 O (0.11 g, 0.30 mmol) in ethanol (10 ml) was added. After stirring for a further 30 min, the solvent was removed by decantation. The crude product was purified by reprecipitation using n-hexane and chloroform to give Ho-(DBM) 3 • H 2 O (0.10 g, yield: SC-XRD measurements were made using a Bruker AXS SMART APEX II with Cu K α radiation (1.541 78 Å), and the obtained crystalline data are presented in the Supporting Information. The crystalline structure (space group, atomic positions, and lattice constants) is in good agreement with the results of a previous study. A Crystallographic Information File (CIF) obtained from the SC-XRD analysis is also provided in the Supporting Information.