Dinuclear Copper(II) Complexes Incorporating a New Septadentate Polyimidazole Ligand

Abstract

The dinuclear copper(II) complexes [Cu(2)(tmihpn)(prz)](ClO(4))(2).2CH(3)CN (6) and [Cu(2)(tmihpn)(O(2)CCH(3))](ClO(4))(2).CH(3)CN (7) were prepared, where tmihpn is the deprotonated form of N,N,N',N'-tetrakis[(1-methylimidazol-2-yl)methyl]-1,3-diaminopropan-2-ol and prz is the pyrazolate anion. The crystal structures of 6 and 7 were determined and revealed that both complexes contain bridging alkoxide ligands as well as bridging pyrazolate and acetate ions, respectively. Crystal data: compound 6, triclinic, P&onemacr;, a = 18.089(2) Å, b = 22.948(3) Å, c = 9.597(2) Å, alpha = 93.37(2) degrees, beta = 94.49(2) degrees, gamma = 81.69(2) degrees, V = 3925.1 Å(3), Z = 4; compound 7, triclinic, P&onemacr;, a = 12.417(2) Å, b = 15.012(3) Å, c = 10.699(2) Å, alpha = 104.76(2) degrees, beta = 102.63(2) degrees, gamma = 99.44(2) degrees, V = 1830.1 Å(3), Z = 2. In compound 6, the coordination geometry around both copper centers resembles a distorted square pyramid, while the stereochemistry around the copper centers in 7 is best described as trigonal bipyramidal. Both complexes display well-resolved isotropically shifted (1)H NMR spectra. Selective substitution studies and integration data have been used to definitively assign several signals to specific ligand protons. Results from the solution (1)H NMR studies suggest that the basal and apical imidazole groups do not exchange rapidly on the NMR time scale and the solid state structures of the complexes are retained in solution. In addition, the magnetochemical characteristics of 6 and 7 were determined and provide evidence for "magnetic orbital switching". Antiferromagnetic coupling in 6 (J = -130 cm(-)(1)) is strong, while the copper centers in compound 7 are ferromagnetically coupled (J = +16.4 cm(-1)). Differences in the magnetic behavior of the two copper centers have been rationalized using the "ligand orbital complementary" concept. The ground state magnetic orbitals involved in spin coupling in 6 (d(x)()()2(-)(y)()()2) are different from those in 7 (d(z)()()2).

Special Features of Some Dinuclear Copper (II) Complexes

“…These complexes also display the selective cytotoxic effect against HepG2 cancer cells (2-fold higher) compared to that against the normal cells. Buchanan and co-workers 21 …”

Theoretical study on the magnetic exchange behavior of a hetero-double-bridged binuclear copper(II) complex: orbital complementary effect

“…For instance, in the hetero-bridged l-alkoxy/ hydroxo-l-X complexes (X = N 3 -, NO 2 -, carboxylate, pyrazolate, azaindolate, etc. ), the different l-X ligands result in different magnetic properties [9][10][11][12][16][17][18]. It can be considered that this differentiation of the magnetic properties is derived from the complementarity or countercomplementarity of the highest occupied molecular orbitals (HOMO) of the second bridging ligand (l-X), which was proposed by McKee et al [10] and Nishida et al [11].…”

“…It can be considered that this differentiation of the magnetic properties is derived from the complementarity or countercomplementarity of the highest occupied molecular orbitals (HOMO) of the second bridging ligand (l-X), which was proposed by McKee et al [10] and Nishida et al [11]. Although this theory has been successfully used to explain the magnetic coupling behavior of a series of heterobridged dinuclear metal complexes [9,[16][17][18][19][20], the mechanism of the magnetic exchange interaction in the halogen ligand hetero-bridged systems has been rarely reported. Hence, in this article, the complex [Cu 2 Cl 2 (l-Cl)(l-OCH 3 )(C 10 H 9 N 3 ) 2 ] [21] is studied to investigate the contribution of the bridging ligands to the magnetic interaction.…”

Structural characterization of ferromagnetic bridged-acetato and -dichlorido copper(II) complexes based on bicompartmental 4-t-butylphenol

“…The Cu-N bond lengths vary from 1.984(4) to 2.054(4) Å. The Cu (1) (1) and Cu(1)-Cl(1′) bond distances are: 2.393(4), 2.2718(14), and 2.8649(14) Å; the basal Cu(2)-Cl(2*) bond distance is 2.2501 (12) and the axial Cu(2)-Cl(2) bond distance is 2.7179(13) Å. Four-membered centrosymmetric Cu 2 Cl 2 rings are connected by the μ-L t-Bu -OH-phenolate moieties to generate the polymeric 1D system. The intra-chain metal distances are: Cu (1) Table S3).…”