CATIONIC CONTROL OF SPIN DIMENSIONALITY IN INFINITE CHAINS OF (CATION)2[MNIII(SALICYLATE)2(CH3OH)2][MNIII(SALICYLATE)2]

Abstract

X-ray structure analysis demonstrates that alternating AB type chains of general composition (cat)2[MnIII(sal)2(CH3OH) 2]-[MnIII(sal)2] [cat = Na+ (1), K+ (2), NH4 + (3); sal = salicylate] can be prepared by the reaction of MnCl2 with salicylic acid and the appropriate base. The molecular structures are composed of three parts: (i) the polyhedron of Mn1 in MnIII(sal)2(CH3OH)2 (the A unit), (ii) the polyhedron of Mn2 in MnIII(sal)2 (the B unit), which is bridged to the A structure by two carboxylates, and (iii) the monovalent cation coordination environment. Varying the cation causes increases in Mn1-Mn2 separations (Na+, 5.347 A; K+, 5.520 A; NH4 +, 5.561 A) and relative tilting of the tetragonal planes of the two metals [Mn2-O3-C7 angles: Na+, 134.3 (4)°; K+, 139.8 (3)°; NH4 +, 140.3 (2)°]. Variable-temperature magnetic susceptibilities of 1-3 were measured to determine the type and magnitude of magnetic exchange in these S = 2 chains. The exchange interaction is weakly antiferromagnetic, with all three salts behaving as one-dimensional magnets and the Na+ salt showing three-dimensional exchange. The observations are rationalized by a spin-exchange model. Crystal data are as follows. 1: triclinic, P1, a = 7.725 (2) A, b = 10.596 (3) A, c = 12.892 (3) A, α = 102.75 (2)°, β = 104.64 (2)°, γ = 110.59 (2)°, Z = 1, V = 898.2 (4) A3; for 2366 data collected in the range 3 ≤ 2θ ≤ 45° and 1791 data with I > 3σ(I), R = 0.056 (Rw = 0.060). 2: triclinic, P1, a = 8.060 (3) A, b = 10.784 (3) A, c = 12.778 (3) A, α = 103.40 (2)°, β = 104.15 (2)°, γ = 109.96 (2)°, Z = 1, V = 949.8 (5) A3; for 2497 data collected in the range 3 ≤ 2θ ≤ 45° and 1885 data with I > 3σ(I), R = 0.035 (Rw = 0.034). 3: triclinic, P1, a = 8.246 (3) A, b = 10.805 (3) A, c = 13.080 (4) A, α = 68.42 (2)°, β = 96.80 (3)°, γ = 69.97 (3)°, Z = 1, V = 977.6 (6) A3; for 2534 data collected in the range 3 ≤ 2θ ≤ 45° and 2180 data with I > 3σ(I), R = 0.030 (Rw = 0.031).