Abstract
Three new dinuclear copper(II) complexes [Cu2(μ–HLn)2(μ-Cl)2Cl2]Cl2 (1–3) have been synthesized and structurally characterized by single-crystal X-ray diffraction, where HLx, (HL1 = N6-propyladeninium, HL2 = N6-butyladeninium and HL3 = N6-isobutyladeninium) are N6-alkyl bidentate NN donor adenine bases. Complexes 1–3 exhibit a coplanar arrangement of both N6-alkyladeninium moieties with UD conformation, with the terms U(up) or D(down) referring to the coordination of each pyrimidinic N3 atoms to the upper or lower metal center. In the three complexes, both copper atoms are five-coordinated (N2Cl3 donor set), resembling a compressed trigonal bipyramid. Each adenine moiety is protonated in N1 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.
Highlights
The chemistry of transition metal coordination to purine nucleobases has been extensively studied, paying special attention to its structural diversity, biological importance and molecular recognition [1,2]
Density functional theory calculations have been performed in order to estimate the exchange coupling constants in these complexes
The adenine moiety is protonated in N1 and the chloride counterions are coplanar to the adenine rings, interacting with N6–H and N3–H groups to establish
Summary
The chemistry of transition metal coordination to purine nucleobases has been extensively studied, paying special attention to its structural diversity, biological importance and molecular recognition [1,2]. Coordination compounds involving nucleobases have interesting potential applications as advanced functional materials [3,4,5]. Upon the formation of the metal−adenine complex, the remaining non-coordinated N-atoms’ donor sites are good hydrogen bond acceptors, conferring the ability to form supramolecular assemblies [8,9]. The ability of purine ligands to form dinuclear complexes via the N3 and N9 bridging mode is well known [10,11,12,13].
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