This work describes the synthesis and characterization of two new compounds with ligand opy (N-(2-pyridyl)oxamate): the copper(II) precursor [Me4N]2[Cu(opy)2].5H2O and CoII CuII coordination polymer {[CoCu(opy)2]}n×4nH2O. This latter compound was obtained by reaction of [Me4N]2[Cu(opy)2].5H2O and CoCl2.6H2O in water. The heterobimetallic CoII CuII chain was characterized by elemental analysis, IR spectroscopy, thermogravimetry and magnetic measurements. Magnetic characterization revealed typical behavior of one-dimensional (1D) ferrimagnetic chain as shown in the curves of temperature (T) dependence of magnetic susceptibility (χM), in the form of χMT versus T, and dependence of magnetization (M) with applied field (H).

Um precursor inédito de sistemas magnéticos moleculares, [Fe(H2opba-i)(dmso)2]Cl (1), onde opba = orto-fenilenobis(oxamato) na forma tautomérica iminoálcool, foi obtido como produto da reação entre H4opba e FeCl3. Os dados de análise elementar, espectroscopias de absorção no infravermelho e Mössbauer e medidas magnéticas indicam que este precursor é constituído por uma mistura de isômeros trans (83%) e cis (17%). O valor de chiMT a 298 K (2,1 emu K mol-1) corresponde ao FeIII com estado de spin (S) entre 3/2 e 5/2. Cálculos teóricos (PBE/DZVP2) de trans- e cis-[Fe(H2opba-i)(dmso)2 ]+ mostram que ambos os isômeros têm spin S = 1/2 no estado fundamental e S = 3/2 para o trans e S = 5/2 para o cis no primeiro estado excitado. A combinação destes resultados leva a valores de chiMT de 0,375 emu K mol-1 e 2,3 emu K mol-1 a baixas e altas temperaturas, respectivamente, os quais são concordantes com os dados experimentais para 1.

A new precursor of molecule-based magnetic systems, [Fe(H2opba-i)(dmso)2]Cl (1), with opba = ortho-phenylenebis(oxamato) in an iminoalcohol tautomeric form, was obtained as a product from the reaction between H4opba and FeCl3. Data from elemental analysis, IR and Mössbauer spectroscopies and magnetic measurements indicate that this precursor is composed of a mixture of trans (83%) and cis (17%) isomers. The chiMT value at 298K (2.1 emu K mol-1) corresponds to FeIII with spin state (S) between 3/2 and 5/2. Theoretical calculations (PBE/DZVP2) of trans- and cis-[Fe(H2opba-i)(dmso)2 ]+ show that both isomers have spin S = 1/2 in the ground state and S = 3/2 for the trans and S = 5/2 for the cis in the first excited state. The combination of these results leads to chiMT values of 0.375 and 2.3 emu K mol-1, at low and high temperature respectively, which are in accordance with the experimental data for 1.