Abstract
The reaction of trivalent Dy super(III)/Ho super(III), 2,2':6',2''-terpyridine (terpy), and hexacyanometallate [M super(III)(CN) sub(6)] super(3-) (M = Fe super(III) and Co super(III)) leads to the formation of a series of cyano-bridged complexes (1-4). In the case of Dy super(III), one-dimensional (1-D) alternating chains [Dy super(III)(terpy)(DMF) sub(2)(H sub(2)O) sub(2)][M super(III)(CN) sub(6)].3H sub( 2)O (M = Fe super(III) for 1 and Co super(III) for 2) were obtained, where each [M super(III)(CN) sub(6)] super(3-) entity acts as a bis-monodentate bridging ligand towards two Dy super(III) ions through two of its six cyanide groups in cispositions, respectively. Contrarily, in the case of Ho super(III), a molecular rectangle {[Ho super(III)(terpy)(DMF)(H sub(2)O) sub(2)][M super(III)(CN) sub(6)]} sub(2).nH sub(2)O.2CH sub(3)OH {(M = Fe super(III) (3) and Co super(III) (4); and n= 6 or 7} has been formed although the synthesis method is same as for 1 and 2. Interestingly, solid-state direct-current magnetic susceptibility analyses demonstrate competing ferromagnetic interactions for 1 while complex 3 shows antiferromagnetic interactions. The variable-temperature magnetic behaviours observed for 2 and 4 only originate from isolated Dy and Ho ions, since a diamagnetic Co super(III) metal ion links the magnetic Ln super(III) ions.