Monoalkylated 4'-aryl-substituted terpyridines.

1-Methyl-2-[4-phenyl-6-(pyridinium-2-yl)pyridin-2-yl]pyridinium diperchlorate, C 22 H 19 N 3 2+ .2ClO 4 - , (I), and 2-[4-(methoxyphenyl)-2,2'-bipyridin-6-yl]-1-methylpyridinium iodide, C 23 H 20 N 3 O + .I - , (II), both crystallize in the monoclinic space group P2 1 /c. In contrast with the monocharged molecule of (II), the doubly charged molecule of (I) contains an additional protonated pyridine ring. One of the two perchlorate counter-anions of (I) interacts with the cation of (I) via an N-H...O hydrogen bond. In (II), two molecules related by a centre of symmetry are connected by weak π-π interactions, forming dimers in the crystal structure.