An enantiomeric pair of 3d-3d heterometallic clusters of {MnIIMnIII12CuII8} has been synthesized in an aqueous solution without heating. The crystal structures reveal a five-layered core of {MnIIMnIII12CuII8}, which is a slightly distorted {MnIIMnIII12} tetradecahedron with its eight triangular faces capped by a CuII ion respectively. The magnetic measurement results establish that anisotropic MnIII atom-containing clusters L-1 and D-1 exhibit slow relaxation of their magnetization vectors.