EPR and UV-vis study on solutions of Cu(II) dmit complexes and the complexes entrapped in zeolite A and ZIF-Cu(IM)2

摘要

The l,3-dithiole-2-thione-4,5-dithiolate (C3S5~(2-) = dmit) complexes with Cu(II) in solutions and deposited into zeolite NaA and into metal-organic framework (MOF) with zeolitic imidazole structure ZlF-Cu(IM)2B were studied by UV-vis and EPR spectroscopy. UV-vis spectra show that intermolecular π-π transitions existing in the visible region can be used for an identification of the molecules deposited in solid matrices. EPR of Cu(dmit)2 complexes in frozen (77 K) DMF (dimethylformamide) solution indicates tetrahedral CuS4 coordination with compressed structure of D_(2d) symmetry and EPR parameters g_(II) = 2.089, g_I = 2.0257, A_(II) = 145.4 x 10~(-4) and A_(I) = 29.8 x 10"4 cm"1. We were looking for such complexes after impregnation of the zeolites NaA with dmit solutions. We found that the Cu(dmit)2 complex in zeolite NaA appears together with Cu(II) complexes being coordinated by host oxygen atoms. The Cu(dmit)2 complexes are, however, deformed to the elongated D_(2d) symmetry. In ZIF-Cu(IM)2B the slightly more axi-ally compressed tetrahedral Cu(dmit)2 complexes appear as a result of coordination of the host Cu(II) ions with captured dmit molecules. The host structure is preserved, exchange coupling between host Cufjmid-azole)4 complexes is strongly weakened and separated Cu-imidazole and Cu(dmir)2 complexes can be distinguished.