Synthesis, characterization, and single-molecule metamagnetism of new Co(ii) polynuclear complexes of pyridine-2-ylmethanol

Abstract

The reaction between pyridine-2-ylmethanol (HL), anhydrous CoCl2 and NaH afforded polynuclear Co(ii) complexes [Co7(L) 12]Cl2 (1), [Co6Na(L)12]Cl (2) and [Co4Cl2(L)6] (3), depending on the HL:CoCl 2 ratio set in the reaction. The core structures of the centrosymmetric complexes 1 and 2 are of the M@Co6 type (M = Co or Na, respectively) with a coplanar arrangement of the metals whereas that of centrosymmetric 3 is of an incomplete dicubane type. The experimental conditions allowing interconversions between these polynuclear complexes have been determined, which provides a more rational control of their synthesis. Thus, 1 transforms to 3 when reacted with CoCl2 in a 1:1 ratio, whereas the same reaction performed with a large excess of CoCl2 gave the tetranuclear pseudo-cubane complex [Co4(L)4Cl 2(MeOH)4] upon recrystallization. Conversely, 1 was isolated from the reaction of 3 with HL and NaH. The crystal structure of these compounds is reported, along with the magnetic behaviour of 1 and 3. The analysis of the magnetism using the effective spin-1/2 Hamiltonian approach revealed single-molecule metamagnetic behavior in 3. © 2011 The Royal Society of Chemistry.