Crystal structure and single crystal EPR of (NH4)2(15-crown-5)3[Cu(mnt)2] and (NH4)2(benzo-15-crown-5)4[Cu(mnt)2]·0.5H2O

Abstract

The X-ray crystal structures of (NH 4 ) 2 (15-crown-5) 3 [Cu(mnt) 2 ] (1) and (NH 4 ) 2 (benzo-15-crown-5) 4 -[Cu(mnt) 2 ]·0.5H 2 O (2) were determined. Two single crystals are composed of distinct structures of ammonium-crown ether supramolecular cation and [Cu(mnt) 2 ] 2− anion. The triple-decker dication in complex 1 and a sandwich dimmer in complex 2 were observed. X-Band EPR studies on the single crystals of both complex 1 and complex 2 have been carried out at room temperature, which revealed that complex 2 showed a perfect hyperfine structure of Cu whereas that of complex 1 could not be observed. The principal values and direction cosines of the principal axes of the g and A tensors were computed by a least-squares fitting procedure. The spin density of Cu(II) was estimated according to the principal values of the A tensors and compared well with the results calculated based on DFT method. supramolecular cation, H-bonding interaction, EPR, g and A tensors, DFT In order to prepare novel molecular materials, many dithiolene compounds were investigated during decades [1][2][3] . The molecular materials based on M(mnt) 2 (M= Ni, Pd or Pt) have increasingly attracted attention because of their novel magnetic property [4][5][6][7] . In this paper, the crystal structure and single-crystal EPR of ion-pair complex which consists of supramolecular cation of ion-crown ether and [Cu(mnt) 2 ] 2− anion were studied on two salts, (NH 4 ) 2 (15-crown-5) 3 [Cu(mnt) 2 ] (1) and (NH 4 ) 2 (benzo-15-crown-5) 4 [Cu(mnt) 2 ]·0.5H 2 O (2). The clear EPR spectra of two single crystals were observed. Many EPR data were collected in three orthogonal planes. g 2 and A 2 tensor have been rigorously calculated using a least-squares-fitting technique [8] , specially adapted to non-coincident g and A tensor systems. The principle values of g and A, as well as the direction cosines of their principal axes with respect to the reference system, are obtained. The spin density of Cu(II) were estimated according to the principal values of the A tensors and compared well with the results calculated based on DFT calculation.