The synthesis, crystal structure, and magnetic properties of a one-dimensional compound, {[Mn(hfac)(2)](2)(biradical)}(n) (1), resulting from the coordination of bis(hexafluoroacethylacetonato)manganese(II) [Mn(hfac)2] with a biradical obtained by grafting two nitronyl nitroxide radicals in the 5 and 5' positions of a 2,2'-bipyridine ligand are described. Compound 1 crystallizes in the triclinic P1 P(1) over bar space group with the following parameters: a = 11.905(2) Angstrom, b = 12.911(2) Angstrom, c = 20.163(3) Angstrom, alpha = 73.556(3)degrees, beta = 80.850(3)degrees, gamma = 82.126(3)degrees, Z = 2. The bipyridyl moiety acts as a chelate toward one [Mn(hfac)2] unit, while the pendent nitronyl nitroxide radicals are symmetrically bound in trans-configuration to additional [Mn(hfac)2] units. The result is infinite chains running along the c axis direction with the biradical bridging [Mn(hfac)(2)]units with pending bipyridine/Mn(hfac)(2) cores. The magnetic behavior is characteristic of ferrimagnetic chains. Qualitatively we observe first the antiferromagnetic coupling (J(2)) of each manganese(II) center with two nitronyl nitroxide moieties, leading to a minimum in the chiT product of 6.63 emu K mol(-1) observed at 70 K and corresponding to a ground spin state S = 3/2 plus one extra spin S = 5/2 coming from the pending manganese(II) center. The increase of chiT at lower temperature is understood as a fictive ferromagnetic coupling related to the true antiferromagnetic coupling J(1) of the pseudospin S = 3/2 with spin S = 5/2 of the pending manganese(II). Along this approach (H = -JS(i)S(j)) the best fit (300-8 K) of the experimental data leads to J(1) = -0.622 +/- 0.022 cm(-1) and J(2) = -203 +/- 3 cm(-1) with g(Rad) = 2.0017 +/- 0.0015 and g(Mn) = 2.0017 +/- 0.0015.