6533b7d5fe1ef96bd12645fa

RESEARCH PRODUCT

{CoIIIMnIII}ncorrugated chains based on heteroleptic cyanido metalloligands

subject

description

The use of the cyanide-bearing complexes PPh4[CoIII(4,4′-dmbipy)(CN)4] and PPh4[CoII(dmphen)(CN)3] as metalloligands towards [Mn(salen)(H2O)]ClO4 affords one-dimensional coordination polymers with the formulas {[MnIII(salen)(μ-NC)2CoIII(4,4-dmbipy)(CN)2]·H2O}n (1) and {[MnIII(salen)(μ-NC)2CoIII(dmphen)(CN)2]}n (2) [PPh4+ = tetraphenylphosphonium cation, 4,4′-dmbipy = 4,4′-dimethyl-2,2′-bipyridine, dmphen = 2,9-dimethyl-1,10-phenanthroline and H2salen = N,N′-ethylenebis(salicylideneimine)]. Compounds 1 and 2 were structurally characterized. Their structures consist of neutral chains with regular alternating [Mn(salen)]+ and [CoIII(4,4′-dmbipy)(CN)4]− (1)/[CoIII(dmphen)(CN)4]− (2) moieties, the latter ones acting as bis-monodentate ligands towards the Mn(III) units through two of their four cyanide groups. During the synthesis, the cobalt(II) ion of the starting [CoII(dmphen)(CN)3]− metalloligand is oxidized to Co(III) and it takes an additional cyanide ligand to transform into {CoIII(dmphen)(CN)4} in 2. Magnetic studies have been carried out on 1 and 2 in the temperature range 1.9–300 K which yielded local negative zero-field splitting parameters of −3.26 (1) and −4.38 cm−1 (2). Frequency-dependent alternating current susceptibility signals under an external applied magnetic field (dc) were clearly observed for 1 and 2 indicating slow magnetic relaxation, that is, Single Ion Magnet (SIM) behaviour. The energy barriers (Ea) to reverse the magnetization direction under an applied dc magnetic field of 2000 Oe were 12.0(2) (1) and 9.4(3) cm−1 (2), whereas the values of the pre-exponential factor (τo) were 1.40(2) × 10−8 (1) and 2.5(2) × 10−8 s (2).