EPR and UV–vis study on solutions of Cu(II) dmit complexes and the complexes entrapped in zeolite A and ZIF-Cu(IM) 2 S.K. Hoffmann a,⇑ , J. Goslar a , S. Lijewski a , K. Tadyszak a , A. Zalewska b , A. Jankowska b , P. Florczak b , S. Kowalak b a Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznan, Poland b Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland article info Article history: Received 13 June 2013 Received in revised form 12 November 2013 Accepted 19 November 2013 Available online 28 November 2013 Keywords: Dmit compounds Zeolite NaA ZIFCu UV–vis Electron paramagnetic resonance abstract The 1,3-dithiole-2-thione-4,5-dithiolate (C 3 S 5 2–  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) 2 B were studied by UV–vis and EPR spectroscopy. UV–vis spectra show that intermolecular p–p ⁄ 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 CuS 4 coordination with compressed structure of D 2d symmetry and EPR parameters g || = 2.089, g \ = 2.0257, A || = 145.4  10 4 and A \ = 29.8  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) 2 B 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 Cu(imid- azole) 4 complexes is strongly weakened and separated Cu-imidazole and Cu(dmit) 2 complexes can be distinguished. Ó 2014 Published by Elsevier Inc. 1. Introduction The C 3 S 5 2– (1,3-dithiole-2-thione-4,5-dithiolate called briefly dmit) anion is of interest as a precursor of photonic and electronic materials. Transition metal complexes of dmit are molecular con- ductors showing metallic behavior [1,2] and nickel and palladium dmit complexes are superconductors [3]. The dmit complexes show useful optical non-linear properties [2] owing to extensive overlap of the p sulfur orbitals and metal ions d-orbitals. The dmit can be easily synthesized by reductive cyclization of carbon disulfide with the alkali metal (M = Na + ,K + , Cs + ) in the presence of DMF. The resulting DMF product solution is a mixture of the dmit 2 and trithiocarbonate ions. The dmit-molecules absorb the light in the visible region and solutions of M 2 dmit display sol- vatochromic behavior [4]. The color of Na 2 dmit is bright red in methanol and in DMF with excess of CS 2 , whereas is deep blue for free dmit 2 in DMF, and becomes yellow after oxidation in air. Usually, dmit 2- anions are stabilized by coordination of transi- tion metal ions (Fig. 1), and the color complexes, as a red Zn(dmit) 2 complex, suggest possibility of an application of dmit compounds as pigments. A stabilization of the pigments can be achieved by encapsulation in voids of zeolite structures as we suggested re- cently for Na 2 dmit in MOF-5 and ZIF-8 zeolites [5]. In this paper we describe effects of encapsulation of Zn(dmit) 2 and Cu(dmit) 2 into zeolite NaA and into zeolitic imidazole frame- work ZIF-Cu(IM) 2 . The dmit complexes were generated in zeolite NaA by impregnation with Na 2 dmit solution and further treatment with respective cations (i.e. Cu, Zn) or by using zeolite NaA par- tially modified with Cu cations (labeled Cu,NaA) as a matrix that provides the Cu cations to form the complex. In case of ZIF- Cu(IM) 2 B solution of Na 2 dmit was used for modification treatment. The effects were observed by UV–vis spectra as well as by electron paramagnetic resonance (EPR) of Cu 2+ ions. 2. Experimental 2.1. Synthesis 2.1.1. Solutions of dmit Na 2 dmit has been obtained from CS 2 in DMF (1:1 volume ratio) at room temperature in presence of metallic sodium as a red solu- tion due to CS 2 excess. The Zn(dmit) 2 or Cu(dmit) 2 complexes were formed by adding 0.1 M solutions of ZnCl 2 or CuCl 2 2H 2 O in DMF, respectively. 1387-1811/$ - see front matter Ó 2014 Published by Elsevier Inc. http://dx.doi.org/10.1016/j.micromeso.2013.11.029 ⇑ Corresponding author. Tel.: +48 61 8695207; fax: +48 61 8684524. E-mail address: skh@ifmpan.poznan.pl (S.K. Hoffmann). Microporous and Mesoporous Materials 186 (2014) 57–64 Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso