Novel self-assembled supramolecular architectures of Mn(ii) ions with a hybrid pyrazine–bipyridine ligand

Abstract

A new hybrid pyrazine-bipyridine ligand L (C26H20N6) and its complexes with Mn(NO3)2, Mn(ClO4)2, MnCl2 and MnBr2 have been synthesised. By the self-assembly of L and Mn(II) ions three different kinds of supramolecular complexes have been obtained: binuclear baguette complex [Mn2L(H2O)6](NO3)4·2.5H2O 1 and tetranuclear [2 × 2] grid-type complex [Mn4L4](ClO4)8·2.5(CH3CN)·2CH3OH 2 and mononuclear complexes [MnL2]X2 (where X = Cl(-)3 and X = Br(-)4). Crystal structures and magnetic properties of Mn(II) complexes 1 and 2 have been also investigated. The crystal structures reveal that in both 1 and 2 complexes the Mn(II) ions have coordination number 6 and distorted octahedral coordination geometry. In 2 four metal cations and four ligands have assembled into a grid-type [2 × 2] array, with a perchlorate anion occupying the central cavity, with clearly a good fit for the center of the cavity. The perchlorate anion, in contrast to the nitrate anion, probably acts as a template in the formation of tetranuclear grid-type complexes. Magnetic susceptibility measurements indicate that the Mn(II) ions are all high spin, and in both 1 and 2 complexes there are weak antiferromagnetic interactions between Mn(II) ions.

Mono- and Dinuclear Manganese Carbonyls Supported by 1,8-Disubstituted (L = Py, SMe, SH) Anthracene Ligand Scaffolds

“…Indeed, closer inspection of the bond distances surrounding the {Mn(N 3 )(S 3 )} unit reveal bond metricsespecially the Mn−N bondsmore closely associated with high-spin versus low-spin systems. The Mn−N bond lengths of 2.269(10), 2.310(11), and 2.282(8) Å found in the dimer 11 are similar to those in other reported high-spin systems (e.g., Mn−N = 2.2499(16) Å) 41 and are much longer than those in reported low-spin systems (e.g., Mn−N = 2.003(2) Å). 42 To confirm that the spin density was indeed localized on the formally manganese(II) {Mn(N 3 )(S 3 )} unit, a spin density plot was generated from the DFT calculations (Figure 11).…”

A new polymeric complex of silver(i) with a hybrid pyrazine–bipyridine ligand – synthesis, crystal structure and its photocatalytic activity

“…The ligand L upon reaction with manganese(II) ions forms mononuclear, dinuclear baguette and tetranuclear [2 Â 2] grid-type complexes. 34 Unlike the octahedral coordination of manganese ions with this ligand we have observed in a polymeric complex that each Ag(I) is five-coordinated being bound to three nitrogen atoms from one ligand as well as two nitrogen atoms from the second molecule of another ligand. The d 10 configuration of silver(I) is free from crystal field steric constraints and thus allows maximum shell flexibility in forming metal complex species.…”

“…The ligand L has been obtained via Stille-type coupling reaction and described before by us. 34 NMR spectra were recorded on a Varian Gemini 300 MHz spectrometer and calibrated against the residual protonated solvent signals (CD 3 CN d 1.94 ppm) and shifts are given in ppm. ESI mass spectra of B10 À4 M acetonitrile solutions were measured using a Waters Micromass ZQ spectrometer.…”