Engenharia de cristais aplicada na modulação de propriedades de magnetos moleculares

Abstract

This work features the application of crystal engineering and magnetochemistry studies of compounds containing oxamate and oxalate ligands. This work is divided in two parts. In the first one are presented compounds containig oxamate ligands and the building block [Cu(bpca)]+. In this part it is described the influence of crystallization solvents and the complex [{K4(H2O)2}{Pd2(ppba)2] (1) on the synthesis of ferromagnetic coordination polymer [{Cu(bpca)}2(H2ppba)]n1.33ndmf0.66ndmso (2), and in themagnetically isolated systems [{Cu(bpca)(H2O)}2(H2ppba)] (3), [{Cu(bpca)}2(H2ppba)]2dmso (4) and [{Cu(bpca)}2(H2ppba)]6H2O (5). Also, it was analyzed the obtention of single crystals dependening on cooling rate of solutions containing [Cu(bpca)]+ and [Pd(opba)]2, arising the discrete trinuclear system [{Cu(bpca)}2{Pd(opba)}]·1,75dmso·0,25H2O (6) when was fast cooled, and the coordination polymer [{Cu(bpca)}2{Pd(opba)}]n·ndmso (7), when was slow cooled, both exhibiting magnetic isolated copper(II)ions. It was proposed two new oxamic ligands containing pyrazol (EtH2Pyox) and isoxazol (EtHIsoox) groups, which ability of molecular recognition trough hydrogen bonds depends on pH. Starting from the reaction of these compounds with [Cu(bpca)]+ building block it were obtained three coordination isomers [Cu(bpca)(H2Pyox)]nndmso3nH2O (8) [Cu(bpca)(H2Pyox)]n2nCH3OH (9) and [{Cu(bpca)2(H2Pyox)}(H2Pyox)]n1/2neg7/2nH2O (10), besides the homobimetallic compound [{Cu(bpca)}2(Isoox)]2H2O0,33eg (11), all exhibiting antiferromagnetic coupling [Hbpca = bis(pyridilcarbonyl)amide, H4ppba = 1,4-phenylenobis(N-oxamic acid), H4opba = 1,2-phenylenobis(N-oxamic acid), EtH2Pyox = Ethyl 4-(1-H-pyrazol-4-il)phenylene-N-oxamato, EtHIsoox = Ethyl 4-(isoxazol-4-il)phenylen-N-oxamato, dmf = dimethylfomarmide, dmso = dimethylsulfoxide, eg = ethyleneglicol]. In the second part are presented works involving the oxalate ligand coordinated to NbV ion in thecomplex [NbO(C2O4)3]3. It was investigated the use of [NbO(C2O4)3]3 as building block, as well as controllable oxalate-delivery in aqueous or methanolic solution. As a building block it was converted to cis-[Nb(O)2(C2O4)2]3 in the presence of chromium(III) perchlorate leading to the molecular square [{Cr(dmso)4}2--{Nb(O)2(C2O4)2}2]2dmso (13) together with (NH4)(Hneo)2[NbO(C2O4)3] (14). Starting from the anion of (AsPh4)3[NbO(C2O4)3]9H2O (15) and in the presence of [Co(terpy)2]2+ it was produced a spin crossover system dependent on temperature [Co(terpy)2]3[NbO(C2O4)3]23CH3OH4H2O (16). As oxalate-delivery ions were synthesized building blocks [Cu(neo)(C2O4)(H2O)] (17) and [Cu2(neo)2(C2O4)(CH3OH)2](ClO4)2 (18), which were used to synthesize the heterometallic complex [{Fe(tpb)(CN)3}2{Cu2(neo)2(C2O4)}]xCH3OH (2,0 x 2,4) (19), as well as systems such as MII2(neo)4(C2O4)](ClO4)22dmso (M = Fe (20), Co (21) and Ni(22)). Magnetic studies revealed that in 13 the ion NbV is able to transmit magnetic moment between the CrIII ions, and in 18, 20-22 was observed that intensity of antiferromagnetic coupling increases when atomic number increases ( J = 5.4 cm1 (Fe) to J = 340 cm1 (Cu)) [C2O4 = oxalate, neo = 2,9-dimethyl-1,10-phenantroline, tpb = trispyrazilborate anion].