Structural and magnetic characterization of manganese(III) complexes of 1,4,8,11-Tetraazacyclotetradecane (Cyclam)

Abstract

The syntheses and structural and magnetic properties of a series of complexes of the type [Mn(cyclam)X2]Y (where cyclam is 1,4,8,11-tetraazacyclotetradecane, C10)H24N4, and X and Y are monoanionic species) are described. The new complex [Mn(cyclam)(NO3)2]NO3, (1), MnC10H24N7O9, crystallizes in the monoclinic space group C2/c with four molecules in a cell of dimensions a = 12.977(2), b = 8.904(2), c = 15.562(2) Å, β = 106.76(1)°. The structure has been refined to a final R-factor of 0.0369 based on 930 observed data. The dichloro complex [Mn(cyclam)Cl2]NO3, (2), MnC10H24N5O3Cl2, crystallizes in the monoclinic space group P21/n with two molecules in a cell of dimensions a = 6.547(2), b = 13.698(4), c = 9.376(2) Å, β = 101.70(2)°. The structure has been refined to R = 0.0255 based on 1909 observed data. The dibromo species [Mn(cyclam)Br2]Br, (3), MnC10H24N4Br3, crystallizes in the tetragonal space group P42/m with two molecules in a cell of dimensions a = 7.971(2), c = 13.002(4) Å. The structure has been refined to R = 0.0589 based on 664 observed intensities. The thiocyanato complex [Mn(cyclam)(NCS)2]NCS, (4), MnC13H24N7S3, crystallizes in the monoclinic space group P21/c with four molecules in a cell of dimensions a = 10.767(2), b = 12.940(2), c = 14.441(3) Å, β = 99.004(16)°. The structure has been refined to R = 0.0349 based on 1764 observed intensities. All four of these structures adopt the expected trans geometry, and all exhibit the axial elongation expected for d4 complexes. In addition, another new trans complex, of formulation trans-[Mn(cyclam)(CN)2]ClO4, has been synthesized, as has the new cis complex ds-[Mn(cyclam)Br2]Br. The magnetic properties of the complexes are all consistent with their formulation as monomeric high-spin d4 systems, all exhibiting room-temperature moments in the vicinity of the spin-only value of 4.9 μB. In the case of 2 there is a significant magnetic interaction between adjacent manganese centers, which can be explained in the light of the structure.