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

Abstract The cyanide-bridged tetranuclear bimetallic rectangles ( XPh 4 ) 4 [ Fe 2 III Cu 2 II ( μ - CN ) 4 ( CN ) 8 ( L ) 2 ] · n H 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 ) · S Cu ( 1 ) + S Fe ( 1 a ) · S Cu ( 1 a ) ] − J 2 [ S Fe ( 1 ) · S Cu ( 1 a ) + S Fe ( 1 a ) · S Cu ( 1 ) ] + D [ S Fe ( 1 ) z 2 + S Fe ( 1 a ) z 2 ] ) leading to a low-lying S  = 2 spin state.