Chiral Tetraarylmethane Derivative with Metal-Coordinating Ability

Phenyl-pyrazinyl-2-pyridyl-2-pyrimidinylmethane (1) has been synthesized in four steps from 2-(chloromethyl)pyridine. This compound is chiral and expected to show metal-coordinating ability because three of four aryl groups have the nitrogen atom at ortho-position with respect to the central carbon atom. The X-ray crystallographic analysis of rac-1 unambiguously revealed the tetraarylmethane framework, but the nitrogen atoms could not be assigned. The optical resolution of 1 was achieved by chiral HPLC. Besides the CD spectra of the two fractions exhibited opposite signs as expected, the solvent effect on the CD spectra was also observed. According to the calculated CD curve based on time-dependent density functional theory (TDDFT) method, the first eluted fraction is the R isomer in terms of absolute configuration. It should be noted that the CD spectrum of 1 was also changed by the addition of the transition metal ions because of the formation of the metal complexes of 1. The Job plot and the electrospray ionization (ESI) mass spectrum of the solution of rac-1 in the presence of Cu2+ ion revealed that the stoichiometry of 1 and Cu2+ was 2 : 1.