Crystal structures of a series of Co II, Cu II and Zn II complexes of 4′-(3,4-dihydroxyphenyl)-2,2′ : 6′,2″-terpyridine and 4′-(3,4-dimethoxyphenyl)-2,2′:6′,2″-terpyridine

Abstract

The crystal structures of the bis(terpyridyl)-metal(II) complexes (Co(L 1) 2][PF 6] 2 · 2.5MeCN, [Co (L 2) 2][PF 6] 2 · 3dmf, [Cu(L 2) 2][PF 6] 2 · 2.5MeCN, and [Zn(L 2) 2][NO 3] 2 · 3dmf are reported, where L 1 is 4′-(3,4-dihydroxyphenyl)-2,2′ : 6′,2″-terpyridine and L 2 is 4′-(3,4-dimethoxyphenyl)-2,2′: 6′,2″-terpyridine. The two Co II complexes and the Cu II complex all show elongation along one axis in addition to the normal tetragonal compression imposed by terpyridyl chelates; this is ascribed to the Jahn-Teller effect, in the case of the Co II complexes arising from the presence of a significant proportion of the low-spin state being present at the temperature used for the structural determination (173 K). The Zn II complexes are the first structurally characterised bis(terpyridyl)-Zn II compounds. These do not show the elongation along one axis that was apparent in the Co II and Cu II structures. The relatively small bite angles for the terpyridyl chelates (ca. 150°, compared to ca. 160° for the first three complexes), results in a greater distortion away from regular octahedral geometry, reflecting the absence of stereoelectronic requirements for Zn II compared to Co II and Co II.