Abstract: The title complex was synthesized in an aqueous solution and its crystal structure was determined by X-ray diffraction. The crystal crystallizes in a triclinic system, space group P1 with a= 1.3063(2) nm , b=1.3194(4) nm, c=1.9502(4) nm, α=90.597(14)°, β= 93.998(11)° , γ=94.093(13)°, V=3.3441(12) nm³, Z=2, the final Rindices are R 1= 0.0654 , wR 2=0.1262 respectively. The complex contains a novel tetranuclear cluster cation with four Er ³⁺ ions connected by four μ₃-OH ions and six bridging carboxyl groups. Each erbium ion is coordinated by three μ₃-OH, three carboxylic oxygen atoms from three α-alanine and two oxygen atoms from water molecules, forming a square-antiprismatic coordination polyhedron.

Key words: Erbium complex, α-Alanine, Crystal structure, Tetranuclear complex