Six new compounds of general formula [Fe₃O(A)₆(H₂O)₃]NO ₃·nH₂O, where A = Gly^-, n = 3 (I); A = Ala^-, n = 4 (II); A = Val^-, n = 2 (III); A = Met^-, n = O (IV); A = Leu^-, n = 1 (V); and A = Trp^-, n = 5 (VI), are synthesized by substituting the acetate radicals in (μ₃-oxo)hexakis(μ-acetato-O,O')-triaquotriiron(III) nitrate with anions of various α-amino acids. The Mössbauer parameters of the complexes (T = 300 K, δ_Na+ = 0.63-0.64 mm/s, ΔE_Q = 0.62-0.76 mm/s; and T = 80 K, δ_Na+ = 0.71-0.74 mm/s, ΔE_Q = 0.73-0.82 mm/s) are indicative of the presence of the iron(III) ions in high-spin state. The temperature dependence (300-102 K) of magnetic susceptibility of I-VI satisfactorily fits the Heisenberg-Dirac-van Vleck model for the three iron ions (S₁ = S₂ = S₃ = 5/2) occupying vertices of the isosceles triangle (C_2v symmetry) and coupled to one another through the exchange interaction with parameters (cm^-1): J₁ = -37.36 and J₂ = -51.42 (I); J₁ = -16.18 and J₂ = -28.42 (II); J₁ = -17.74 and J₂ = -36.45 (III); J₁ = -16.51 and J₂ = -33.93 (IV); J₁ = -12.97 and J₂ = -27.11 (V); and J₁ = -27.08 and J₂ = -39.27 (VI). The thermal analysis data suggest the low thermal stability of the compounds (T_onset = 30-60°C with following stepwise decomposition).