EPR, Magnetic, and Computational Characterization of Linear and Zigzag Ladder‐type Chains of Exchange Coupled Cu(II) Complexes with Picolinic and Dipicolinic Acid Ligands

PÉREZ, ANA L.; KEMMERER, AXEL; BAGGIO, RICARDO; RAMOS, CARLOS A.; DALOSTO, SERGIO D.; PASSEGGI, MARIO C. G.; RIZZI, ALBERTO C.; BRONDINO, CARLOS D.

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY

WILEY-V C H VERLAG GMBH

Año: 2021 p. 4183 - 4195

1434-1948

We report magnetic, EPR, and computational studies ontwo representative examples of structurally well-characterized onedimension (1D) molecular systems: the copper complexes catena-[bis(-pyridine-2-carboxylato)-copper dihydrate] and catena-[(2-pyridine-2,6-dicarboxylato)-diaqua-copper(II)], hereafter 1 and 2,respectively. Experimental and theoretical results confirmed that thestructural chains in both compounds behave as magnetic chains inwhich the copper ions are weakly coupled by isotropic exchange.Magnetic susceptibility measurements of 1 suggested that thecopper ions are antiferromagnetically coupled whereas EPRmeasurements suggested ferromagnetic coupling at temperatureabove 100 K which becomes antiferromagnetic at low temperatures.Computational calculations would indicate that the ferromagneticantiferromagneticchange may be due to dCu-Oap shortening onlowering temperature temperature (a fact that was observedexperimentally by XRD at low temperatures), which redistributes thesmall Cu(II) unpaired spin density delocalized on the apical ligand tocopper. The 1D magnetic behavior of the zigzag ladder chain of 2 isless detectable than that of the single chain of 1. Magneticsusceptibility measurements in conjunction with computationalcalculations showed that the pathways that give rise to the 1D laddertransmit ferromagnetic exchange interactions with different strengths,with the stronger interaction being transmitted along the rungs. Therole of the weaker exchange interactions transmitted along the railson the magnetic dimensionality of 2 is analyzed.