The slow dynamics (10⁻⁶ s–10⁴ s) of the magnetization in the paramagnetic phase, predicted by Glauber for the 1d Ising model, has been observed with ac susceptibility and SQUID magnetometry measurements in a molecular chain comprising alternating Co²⁺ spins and organic radical spins strongly antiferromagnetically coupled to give a 1d ferrimagnet. An Arrhenius behavior with activation energy Δ = 152 K has been observed for ten decades of relaxation time and found to be consistent with the Glauber model. We have extended this model to take into account the ferrimagnetic nature of the chain as well as its helicoidal crystal structure.

Reactions of Mn sources with di-2-pyridyl ketone, (2-py)₂CO, and phenyl 2-pyridyl ketone oxime, (ph)(2-py)CNOH, give the novel clusters [Mn₁₀ ^IIMn₄ ^IIIO₄(O₂CMe)²⁰{(2-py)₂C(OH)O}₄] 1 and [Mn₄ ^IIMn₄ ^IIIO₂(OH)₂(O₂CPh)₁₀{(ph)(2-py)CNO}₄] 2, respectively, which possess low-spin ground states; the observed tetradecanuclearity in 1 is extremely rare in 3d-metal chemistry, while the core of 2 has a unique topology consisting of two linked {Mn₂ ^IIMn₂ ^IIIO(OH)} units.