Elucidating the 2D Magnetic Topology of the 'Metal-Radical' TTTACu(hfac)2 System

The TTTACu(hfac)2 polymer (1; in which TTTA=1,3,5-trithia-2,4,6-triazapentalenyl, and hfac=(1,1,1,5,5,5)-hexafluoroacetylacetonate) is one of the most prominent examples of the rational use of the metal-radical' synthetic approach to achieve ferromagnetic interactions. Experimentally, the magnetic topology of 1 could not be fully deciphered. Herein, the first-principles bottom-up procedure was applied to elucidate the nature and strength of the magnetic JAB exchange interactions present in 1. The computed JAB values give rise to a 2D magnetic topology of ferromagnetic dimers (+11.9cm-1) coupled through weaker antiferromagnetic interactions (-3.0 and -3.2cm-1) in two different spatial directions. The hitherto unknown origin of the antiferromagnetic interdimer interactions is thus unveiled. By using the 2D magnetic topology, the agreement between calculated and experimental T(T) data is extraordinary. In the metal-radical TTTACu(hfac)2 compound, the computational model transcends the local dimer cluster model owing to strong interactions between metal centers and organic radicals, thereby creating a de facto biradical. In addition, it is shown that the magnetic topology cannot be inferred from the polymeric [TTTACu(hfac)2]n crystal motif, that is, from its chemical coordination pattern. Instead, one should think in terms of magnetic building blocks, namely, the de facto biradicals. El polimer TTTACu(hfac)2 (1; on TTTA=1,3,5-tritia-2,4,6-triazapentalenil, hfac=(1,1,1,5,5,5)-hexafluoroacetilacetonat) es un dels exemples mes prominents de l'us racional de l'aproximacio de sintesi metall-radical' per tal d'obtenir interaccions ferromagnetiques. Experimentalment, la topologia magnetica d'1 no s'ha pogut desxifrar completament. En aquest treball, el procediment de treball bottom-up basat en primers principis s'aplica per tal de dilucidar la naturalesa i forca de les interaccions magnetiques de bescanvi JAB presents a 1. Les JAB calculades donen lloc a una topologia magnetica 2D que consisteix en dimers ferromagnetics (+11.9cm-1) acoblats a traves d'interaccions antiferromagnetiques mes debils (-3.0 and -3.2cm-1) al llarg de dues direccions diferents. Per tant, hem donat a coneixer l'origen fins ara desconegut de les interaccions antiferromagnetiques entre dimers. Fent servir la topologia magnetica 2D, la concordanca entre dades calculades i experimentals de T(T) es extraordinaria. En el compost metall-radical' TTTACu(hfac)2, el model computacional transcendeix el model local de dimer a causa de les fortes interaccions que s'estableixen entre centres metallics i radicals organics donant lloc a un biradical de facto com a resultat. A mes, es demostra que la topologia magnetica no es pot deduir a partir del motiu polimeric [TTTACu(hfac)2]n del cristall, es a dir, a partir del seu patro de coordinacio quimica. Aixi doncs, s'ha de pensar en termes de blocs de construccio magnetics, es a dir, de biradicals de facto.