A heterospin dinuclear complex [Dy(0.87)Yb(1.13)(H(2)cht)(2)Cl(4)(H(2)O)(MeCN)]·MeCN shows shifts of the relaxation barriers with respect to the barriers observed in homospin Dy(2) and Yb(2) isostructural complexes. The origin of slow relaxation in the latter two compounds was elucidated by ab initio calculations.