The synthesis, crystal growth, magnetic susceptibility, and polarized optical absorption spectra in the visible and near UV of (Et4N)(3)Fe2F9, are,reported. From single-crystal magnetic susceptibility data and high-resolution absorption spectra in the region of the (6)A(1) --> (4)A(1) spin-flip transition, exchange splittings in the ground and excited states are derived. Ferro,magnetic ground and excited state exchange parameters J(GS) = -1.55 cm(-1) and J(ES) = -0.53 cm(-1) are determined, respectively, and the relevant orbital contributions to the net exchange are derived from the spectra. The results are compared with those reported earlier for the structurally and electronically analogous [Mn2X9](5-) pairs in CsMgX3:Mn2+ (X = Cl-, Br-), in which the splittings are antiferromagnetic. This major difference is found to be due to the increased metal charge of Fe3+ compared to Mn2+, leading to orbital contraction nd thus to a strong decrease of the orbital overlaps and hence the antiferromagnetic interactions.