Cu(II)–N6-Alkyladenine Complexes: Synthesis, X-ray Characterization and Magnetic Properties

Abstract

Three new dinuclear copper(II) complexes [Cu 2 (µ-HL n) 2 (µ-Cl) 2 Cl 2 ]Cl 2 (1-3) have been synthesized and structurally characterized by single-crystal X-ray diffraction, where HL x , (HL 1 = N 6-propyladeninium, HL 2 = N 6-butyladeninium and HL 3 = N 6-isobutyladeninium) are N 6-alkyl bidentate NN donor adenine bases. Complexes 1-3 exhibit a coplanar arrangement of both N 6-alkyladeninium moieties with UD conformation, with the terms U(up) or D(down) referring to the coordination of each pyrimidinic N 3 atoms to the upper or lower metal center. In the three complexes, both copper atoms are five-coordinated (N 2 Cl 3 donor set), resembling a compressed trigonal bipyramid. Each adenine moiety is protonated in N 1 and the positive charge balanced by chloride counterions. Magnetic measurements of complexes 1 and 3 in the 2-300 K temperature range indicate antiferromagnetic coupling with J = −156.1(7) and J = −151(2) cm −1 , respectively. Density functional theory calculations have also been performed in order to estimate the exchange coupling constants in these complexes. The theoretically calculated J values are in good agreement with the experimental values.