Tetranuclear Manganese(II) Complexes of Thiacalixarene Macrocycles with Trigonal Prismatic Six-Coordinate Geometries: Synthesis, Structure, and Magnetic Properties

Two tetranuclear manganese(II) complexes [MnII4(thiaS)2] (1) and [MnII4(thiaSO)2] (2) have been synthesized under
solvothermal conditions in methanol with p-tert-butylthiacalix[4]arene (thiaS) and p-tert-butylsulfinylthiacalix[4]arene
(thiaSO). For both complexes, the structure has been established from single-crystal X-ray diffraction. [Mn4(thiaS)2]·H2O (1) crystallizes in the orthorhombic Immm (No. 71) space group with the following parameters:  a = 18.213
(5) Å, b = 19.037 (5) Å, c = 29.159 (5) Å, V = 10110 (4) Å3, and Z = 4. [Mn4(thiaSO)2]·H2O (2) crystallizes in
the monoclinic C2/m (No. 12) space group with the following parameters:  a = 33.046(1) Å, b = 19.5363 (8) Å,
c = 15.7773 (9) Å, β = 115.176 (2)°, V = 9218.3 (8) Å3, and Z = 4. The two complexes are neutral and are best
described as manganese squares sandwiched between two thiacalixarene macrocycles. In both complexes, each
manganese center is six-coordinated in a trigonal prismatic geometry with four phenoxo oxygen atoms plus two
sulfur atoms for 1 or two oxygen atoms from SO groups for 2. The two tetranuclear complexes exhibit identical
magnetic behaviors resulting from antiferromagnetic interactions between the four manganese centers. The simulation
of the magnetic susceptibility was done considering a single exchange-coupling constant between the manganese(II)
ions, J (H = −J(S1S2 + S2S3 + S3S4 + S1S4)). The best fits give the same result for the two complexes:  g = 1.94
and J = −5.57 cm-1.