Synthesis, structure, and magnetic properties of [Mn < sup > III < /sup > (salpn)NCS] < inf > n < /inf > , a helical polymer

Abstract

Dimeric [Mn(salpn)NCS]2 (1) and polymeric [Mn(salpn)NCS] n (2) are formed by the reaction of Mn(CH3CO2)2· 4H2O, the schiff base, and thiocyanate. The formation of the two polymorphic forms is solvent and temperature dependent. 1: orthorhombic, space group Pbca, with a = 12.573(2) Å, b = 13.970(7) Å, c = 18.891(9) Å, and Z = 8.2: orthorhombic, space group Pna21, with a = 12.5277(14) Å, b = 11.576(2) Å, c = 11.513(2) Å, and Z = 4. The dimers in 1 are held together by weak noncovalent Smellip;π (phenyl) interactions leading to a chain along the a-axis. Each monomeric unit of the polymer in 2 is related to its adjacent ones by a 2-fold screw axis leading to a helix along the c-axis. The exchange coupling is nondetectable in the dimer. The magnetic susceptibility of the helical chain fits a classical chain law with J = -3.2 cm-1 and shows a weak ferromagnetic ordering below 7 K due to spin canting effects.