The class of μ3-oxo trinuclear clusters [1,2] is found to be of great scientific interest for various reasons: the diverse architecture and self-assembly in the crystal [3], their optical and catalytic properties [4,5], magnetic behaviour [6], their use as building blocks in polymeric systems [7], as well as for their use as precursors to obtain nanomaterials [8].  In this context we have synthesized and structurally characterized by single crystal X-ray method a new heterotrinuclear cluster with the composition [Fe2IIINiIIO(2-hnapa)6(H2O)3]·0.5DMA·4.5H2O, where 2-hnapa denotes the monodeprotonated 3-hydroxy-2-naphthoic acid and DMA = dimethylacetamide. According to single crystal X-ray studies, the complex has a molecular trinuclear structure (Fig.1) and crystallizes in the triclinic space group P-1 with the following unit cell parameters: a = 13.1774(10), b = 14,0359(8), c = 24,8261(13) (Å), α = 85.447(5)º, β = 88.718(5)º, γ = 62.379(7)º. In the almost molecular structure of the complex two Fe3+ and one Ni2+ ions occupy the vertexes of an equilateral triangle, with metal∙∙∙metal distances range from 3.25851(18) Å to 3.2975(3) Å. The IR spectrum of the [Fe2IIINiIIO(2-hnapa)6(H2O)3]·0.5DMA·4.5H2O complex comprises numerous absorption bands (Fig.2). The coordinated water molecules are characterised by the ν(OH) = 3238.5 cm-1 vibration. Some of the absorption bands in IR spectrum have been attributed as follows: ν(OH, CH) = 3188.2 cm-1, ν(C=O) (DMAA) = 1764.1 cm-1, νas(COO) = 1611.3, νs(COO) = 1464.4 cm-1, δ(OH)(naphthol) = 1349.7 cm-1, ν(C-OH)(naphthol) = 1294.7 cm-1, δ(OH)(R-OH) = 1243.9 cm-1. The absorption band at 670.2 cm-1 can be assigned to ν(FeO) stretching vibrations.