Substitution of the organic cation X in the 1D polymer, (X)(2)[Mn(acacen)Fe(CN)(6)], leads to an essential change in magnetic behavior. Due to the presence of more voluminous Ph4P+ cations, the polyanion has a more geometrically distorted chain skeleton and, as a consequence, enhanced single chain magnet (SCM) characteristics compared to those for Et4N+. The Arrhenius relaxation energy barriers, the exchange interaction constant and the zero-field splitting anisotropy of Mn-III are determined from the analysis of magnetic measurements. The discussion is supported with ligand field calculations for [Fe(CN)(6)](3-) that unveils the significant anisotropy of Fe magnetic moments.