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The crystal structures and magnetic properties of three Mn(III) Schiff-base complexes [Mn(3-OMe-sal-N-1,5,8,12)]AsF 6 ·H 2 O (1) , [Mn(4-OMe-sal-N-1,5,8,12)]AsF 6 ·H 2 O (2) and [Mn(5-OMe-sal-N-1,5,8,12)]AsF 6 (3) have been studied. Complexes 1 and 2 show gradual SCO behavior. The transition temperatures of 2 is 98 K higher than that of 1. Due to the absence of crystallizing solvent water molecule, complex 3 maintains a HS state in the test temperature range. [Display omitted] Spin crossover (SCO), as a molecular bistable phenomenon, has attracted extensive interest. In this paper, the syntheses, crystal structures and magnetic properties of three Mn(III) hexadentate Schiff-base complexes [Mn(3-OMe-sal-N-1,5,8,12)]AsF 6 ·H 2 O (1) , [Mn(4-OMe-sal-N-1,5,8,12)]AsF 6 ·H 2 O (2) and [Mn(5-OMe-sal-N-1,5,8,12)]AsF 6 (3) have been reported. The substituent positions of ligands and solvent molecules have a cooperative effect on SCO behavior. Complex 1 shows a complete SCO between the high-spin (HS, S = 2) and low-spin (LS, S = 1) states without thermal hysteresis, and complex 2 shows a gradual incomplete SCO behavior. The transition temperatures of 2 (T 1/2 = 241 K) is 98 K higher than that of 1 (T 1/2 = 143 K), which indicates that the ligand field strength of (4-OMe-sal-N-1,5,8,12)2– is stronger than that of (3-OMe-sal-N-1,5,8,12)2–. Due to the absence of crystallizing solvent water molecule, complex 3 maintains a HS state in the test temperature range. [ABSTRACT FROM AUTHOR]

In this paper, we introduce the halogen substituents (F, Cl, Br, I) to explore their influence on the structures and SCO properties of the Mn(III) complexes. [Display omitted] Six mononuclear Mn(III) complexes with hexadentate Schiff-base ligand, the products of the reaction between a N,N ′-bis(3-aminopropyl)ethylenediamine or triethylenetetramine and 5-X-salicylaldehyde have been synthesized: the I− salts of complexes 1 – 3 exhibit a gradual SCO behavior, [Mn(5-Cl-sal-N-1,5,8,12)]I (1) shows a nearly complete SCO with T 1/2 = 125 K, whereas [Mn(5-Br-sal-N-1,5,8,12)]I (2) and [Mn(5-I-sal-N-1,5,8,12)]I (3) show a gradual and incomplete SCO above room temperature. [Mn(5-F-sal-N-1,4,7,10)]I (4) predominantly remains HS state at all temperatures. [Mn(5-I-sal-N-1,5,8,12)]NO 3 (5) and [Mn(5-F-sal-N-1,5,8,12)]NO 3 (6) show an almost full conversion to the HS state and a more gradual SCO having the T 1/2 value of 282 K for 5 and 159 K for 6, respectively. [ABSTRACT FROM AUTHOR]