Trinuclear complexes and coordination polymers of redox-active guanidino-functionalized aromatic (GFA) compounds with a triphenylene core.

Abstract

Herein, we report on the synthesis, redox activity, and coordination chemistry of 2,3,6,7,10,11-hexakis(tetramethylguanidino)triphenylene. CV measurements indicated that the new compound could be oxidized in three separate reversible two-electron oxidation events. The HOMO and LUMO energies were estimated from the oxidation wave and the onset of absorption in the UV/vis spectrum. Our discussion also includes the related new compound 2,3,6,7,10,11-hexakis(N,N'-dimethylethyleneguanidino)triphenylene. Then trinuclear Cu(I) and Cu(II) complexes of the new triphenylene ligands were characterized, and their electronic properties are discussed. In contrast to previously studied redox-active GFA ligands, oxidation of trinuclear copper(I) iodide complexes with I2 leads to copper instead of ligand oxidation. In the tetra-coordinated Cu(II) complexes, the coordination mode is intermediate between tetrahedral and square planar. The optical properties of the complexes were studied, and low-energy electronic transitions were assigned to ligand-to-metal charge-transfer (LMCT) excitations. We then extended our analysis to trinuclear Ni(II) and Co(II) complexes. The magnetic coupling mediated through the triphenylene ligand in the trinuclear Cu(II) and Co(II) complexes was studied by SQUID magnetometry, revealing ferromagnetic coupling of the spin centers and different degrees of spin delocalization into the guanidino groups. Finally, we show that the GFA ligands could be linked to one- or two-dimensional coordination polymers and porous materials with a layer structure by reaction with silver halides.