[Er III (BHT)3(THF)] (26.9 mg, 0.030 mmol) was dissolved in 3.8 g of pentane. 4,4'-azopyridine (azopy) (5.5 mg, 0.030 mmol) was also dissolved in n-pentane, 4.5 g. The orange solution of the ligand was added dropwise to the solution of the complex. Clear, dark brown solution was sealed in a vial and left for crystallization at room temperature. The identity and purity of product was confirmed by PXRD measurements (Figure ). Yield: 15 mg (43%).