Zn(II)-histidine: Zn(OH) 2 was prepared by dissolving solid Zn(II) chloride in 1 M NaOH at a 1:2 molar ratio. This solution was stirred for 1 hour at room temperature. Over this time, Zn(OH) 2 had precipitated as a white solid, which was isolated by vacuum filtration, washed with cold water, and air-dried overnight. 2 equiv. L-histidine and 1 equiv. Zn(OH) 2 were dissolved in separate aqueous solutions, then mixed together and stirred at 50 o C for 2 hours. This solution was allowed to evaporate to ⅓ of its original volume, and left at room temperature for crystals to form. Colorless, tetragonal crystals then formed overnight.