Haldane Gap Systems

Abstract Haldane gap compounds with S =1 formulated as [Ni(AA) 2 X]Y ((AA) 2 =(diamines) 2 , linear-tetramines, N 4 -macrocycles; X=NO 2 and N 3 ; Y=ClO 4 , BF 4 and PF 6 ) and (CH 3 ) 4 N[Ni(NO 2 ) 3 ], and with S =2 formulated as [Mn(AA) 2 Cl 3 ] (AA=bipy and phen) are described. They have one-dimensional structures with bridging ligands. The Haldane conjecture was proven by magnetic susceptibility and high-field magnetization measurements. The magnitudes of the Haldane gap with S =1 can be controlled by combination of the bridging ligands, in-plane ligands, and counteranions as follows: X, N 3 >NO 2 ; AA, en≧tn>linear-tetramines>dmpn>Me 6 [14]aneN 4 ≧[15]aneN 4 ; Y, ClO 4 >PF 6 . In spite of a similar structure to Haldane gap compounds, the [Ni([15]aneN 4 )N 3 ]PF 6 and [Ni(en) 2 (NO 2 )]BF 4 species show spin-glass behavior, which is very novel in one-dimensional spin systems. The [Mn(bipy)Cl 3 ] is regarded as the first example of the Haldane gap system with S =2.