Development of biradical ligands toward [2×2] molecular grids

Abstract

Abstract. Introduction of 2p spins into molecular grids is rare. We prepared 4,6-bis{3-(4,4,5,5-tetramethylimidazolin-1-yloxyl-3-oxido-2-yl)-1H-pyrazol-1-yl}pyrimidine (bis'nitronyl nitroxide') and its bisdeoxygenated derivative (bis'imino nitroxide') as a building block for [2×2] molecular grids. Electron spin resonance spectra were satisfactorily simulated with the corresponding biradical models. The magnetic susceptibility measurements revealed the presence of two radical groups in a molecule. X-Ray crystal structure analysis of the bis'nitronyl nitroxide' derivative clarified the molecular structure constructed as designed. However, the geometries around the single bonds between pyrimidine and pyrazole rings were configured to be transoid (anti) in the crystal. A dichloromethane molecule was incorporated as a guest.

N^N^C-Cyclometalated rhodium(iii) complexes with isomeric pyrimidine-based ligands: unveiling the impact of isomerism on structural motifs, luminescence and cytotoxicity

“…HL 2,5 and HL 2,6 belong to pyrazolyl-pyrimidine ligands 23,69–76 and contain the pyrazolyl group at the position 4 of the pyrimidine ring. Aided by the N 3 pyrimidinic atom, this group forms the N^N-chelating site of the ligand molecule.…”