The title compound Mn3Sb2S6(C6H18N4) (C6H18N4 = triethylenetetramine) was obtained under solvothermal conditions by reacting Mn, Sb, S,and the amine at 140 degrees C for 7 days. The compound crystallizes in the triclinic space group P (1) over bar with a = 6.645(1) angstrom, b = 8.667(1) angstrom, c = 9,660(1) angstrom, alpha = 90.82(2)degrees, beta = 109.70(2)degrees, gamma = 110.68(2)degrees, Z = 1, and V = 484.4(1) angstrom(3). The Mn4Sb2S6 double-heterocubane unit is the main motif in the structure of the title compound, which results from the interconnection of two SbS3 trigonal pyramids, two MnS6 octahedra, and two MnS4N2 octahedra. The two N atoms completing the environment of the latter Mn2+ ions belong to the tetradentate amine; i.e., the amine acts in a bidentate manner. The Mn4Sb2S6 groups are joined by corner sharing of the MnS6 octahedra, yielding one-dimensional linear Mn3Sb2S6 rods along [100]. The two other N atoms of the amine molecule act in a bidentate manner to Mn2+ ions of neighboring rods, thus producing layers within the (010) plane. Within the rods, the arrangement of the Mn2+ ions in triangles leads to a chain of Mn2+ diamonds connected via opposite corners. For the magnetic properties, each edge connecting the Mn2+ ions represents a superexchange path due to coupling of the Mn2+ centers via S bridges. The resulting Mn2+ triangles give rise to substantial competing interaction and magnetic frustration. Below about 100 K, a gradual buildup of short-range antiferromagnetic correlations is observed. At lower temperatures, long-range antiferromagnetic interactions occur with T-N = 2.90 K, as indicated by a lambda-type anomaly in the heat capacity curve, The analysis of the magnetic and heat capacity data evidences that the magnetic properties are essentially determined by the one-dimensional character of the Mn3Sb2S6 chain. In addition, significant magnetic frustration due to the arrangement of the Mn2+ ions in a triangular configuration cannot be neglected.