Carbonate-bridged tetranuclear NiII2GdIII2 complex generated by atmospheric CO2 fixation

Atmospheric CO2 fixation by a basic reaction mixture of [NiII(3-MeOsaltn)(H2O)2] and GdIII(NO3)3·6H2O gave a carbonate-bridged tetranuclear NiII2GdIII2 complex, (μ4-CO3)2[NiII(3-MeOsaltn)(MeOH)GdIII(NO3)]2·H2O, where 3-MeOsaltn denotes N,N′-bis(3‐methoxy-2-oxybenzylidene)-1,3-propanediaminato. The tetranuclear structure possessing an inversion center can be described as two [NiIIGdIII] binuclear units bridged by two carbonate CO32 − ions: two oxygen atoms of the carbonate ion bridge the high-spin NiII and GdIII ions of a binuclear unit and the remaining oxygen atom of the carbonate ion coordinates to a GdIII ion of the adjacent binuclear unit. The temperature-dependent magnetic susceptibilities, from 1.9 to 300 K, follow the Curie–Weiss equation of χMT = C / (T − θ) with θ = + 2.3 K and C = 18.24 cm3 K mol− 1, suggesting a ferromagnetic interaction. The magnetic data were well reproduced assuming two independent [NiII–GdIII] binuclear units with the parameters of J(Ni–Gd) = + 1.2 cm− 1 and D = + 2.1 cm− 1.