Design of single cyanide-bridged tetranuclear bimetallic rectangles exhibiting ferromagnetic coupling

The cyanide-bridged tetranuclear bimetallic rectangles (XPh4)(4)[(Fe2Cu2II)-Cu-II(mu-CN)(4)(CN)(8)(L)(2)] center dot nH(2)O [X = P (1) and As (2); L = bpcam (1) and bpca (2); n = 4 (1) and 0 (2)] have been prepared and their, crystal structures were characterized by single crystal X-ray diffraction; 1 exhibits intramolecular ferromagnetic interactions (J(1) = +3.7 cm(-1) and J(2) = +7.0 cm(-1), H = -J(1) [S-Fe(1) center dot S-Cu(I)+ S-Fe(1a) center dot S-Cu(1a)] - J(2)[S-Fe(1) center dot S-Cu(1a) + S-Fe(1a) center dot S-Cu(1)] + D[S-Fe(1)z(2) + S-Fe(1a)z(2)]) leading to a low-lying S = 2 spin state. (c) 2005 Elsevier B.V. All rights reserved.