Magneto-structural studies of two new cobalt(ii)-N,N-diisobutylisonicotinamide compounds: [CoLCl2]nand [Co(L)2(H2O)4][CoLBr3]2·2H2OElectronic supplementary information (ESI) available: CCDC reference numbers 808174–808175. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c1dt10991j

Two similar synthetic pathways using the ligand N,N-diisobutylisonicotinamide (L) with anhydrous CoX2salts (being X = Cl−, Br−) led to different species: a one-dimensional system, [CoLCl2]n, 1, and an ionic product [Co(L)2(H2O)4][CoLBr3]2·2H2O, 2, respectively. Compound 1is a polymer in which ligand L coordinates to tetrahedral CoIIions in a bidentate bridging fashion using the pyridine nitrogen and carbonyl oxygen atoms. Compound 2consists of one octahedral cationic [Co(L)2(H2O)4]2+entity and two tetrahedral anionic [CoLBr3]−units. In this system, the ligand molecules coordinate only through the pyridine nitrogen atoms. The magnetic properties of 1and 2were investigated in the temperature range of 2.0 to 300.0 K and correlations between both (due to the existence of similar features) examined. The study of the magnetic properties of 1was carried out by considering each CoIIion as a perfectly isolated system, hence, J= 0, but taking into account a significant zero-field splitting contribution due to distortions on the tetrahedral environment of the cobalt atoms. The fit of the magnetic susceptibility data together with reduced magnetization vs H/Tmeasurements provided similar parameters (D = 10.8 cm−1, g= 1.92, g= 2.92 for the former and D = 11.04 cm−1and g= 2.05 for the latter, respectively). On the other hand, the magnetic response of compound 2has been analyzed using a model which considers the presence of two tetrahedral and one octahedral Co(ii) ions (CoTdand CoOh). The study was carried out in two separated blocks, above and below 80 K, where only the most significant effects at each interval of temperature were considered. As a result, the analysis of the magnetic data shows weak antiferromagnetic interactions between the CoOhand the two CoTdions (J= −0.41 cm−1) in 2. The best fit parameters were gCoTd= 2.89, gCoOh= 3.50, DCoTd = 10.62 cm−1, ECoTd = 2.95 cm−1, Δ = 240.9 cm−1and JL-S= −107.1 cm−1, from where λwas calculated with a final value of −144.8 cm−1(JL-S= Aκλ). The approximations performed to obtain these values provide reasonable results in agreement with compound 1and also to other systems in the literature. [ABSTRACT FROM AUTHOR]