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

Abstract

The 1,3-dithiole-2-thione-4,5-dithiolate (C3S52–≡dmit) complexes with Cu(II) in solutions and deposited into zeolite NaA and into metal–organic framework (MOF) with zeolitic imidazole structure ZIF-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 (77K) DMF (dimethylformamide) solution indicates tetrahedral CuS4 coordination with compressed structure of D2d symmetry and EPR parameters g||=2.089, g⊥=2.0257, A||=145.4×10−4 and A⊥=29.8×10−4cm−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 D2d symmetry. In ZIF-Cu(IM)2B the slightly more axially 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 Cu(imidazole)4 complexes is strongly weakened and separated Cu-imidazole and Cu(dmit)2 complexes can be distinguished.