Directing 2D-Coordination Networks: Combined Effects of a Conformationally Flexible 3,2':6',3″-Terpyridine and Chain Length Variation in 4'-(4-n-Alkyloxyphenyl) Substituents.

Abstract

The synthesis and characterization of 4′-(4-n-propoxyphenyl)-3,2′:6′,3″-terpyridine is described. Five 2D-coordination networks have been isolated by crystal growth at room temperature from reactions of Co(NCS)2 with 4′-(4-n-alkyloxyphenyl)-3,2′:6′,3″-terpyridines in which the n-alkyl group is ethyl, n-propyl, n-butyl, n-pentyl and n-hexyl in ligands 2–6, respectively. The single-crystal structures of [{Co(2)2(NCS)2}.0.6CHCl3]n, [{Co(3)2(NCS)2}.4CHCl3.0.25H2O]n, [{Co(4)2(NCS)2}.4CHCl3]n, [Co2(5)4(NCS)4]n and [Co(6)2(NCS)2]n have been determined, and powder X-ray diffraction has demonstrated that the single-crystal structures are representative of the bulk materials. Each compound possesses a (4,4) net with Co centres as 4-connecting nodes. For the assemblies containing 2, 3 and 4, the (4,4) net comprises two geometrically different rhombuses, and the nets pack in an ABAB... arrangement with cone-like arrangements of n-alkyloxyphenyl groups being accommodated in a similar unit in an adjacent net. An increase in the n-alkyloxy chain length has two consequences: there is a change in the conformation of the 3,2′:6′,3″-tpy metal-binding domain, and the (4,4) net comprises identical rhombuses. Similarities and differences between the assemblies with ligands 2–6 and the previously reported [{Co(1)2(NCS)2}.3MeOH]n and [{Co(1)2(NCS)2}.2.2CHCl3]n in which 1 is 4′-(4-methoxyphenyl)-3,2′:6′,3″-terpyridine are discussed. The results demonstrate the effects of combining a variable chain length in the 4′-(4-n-alkyloxyphenyl) substituents of 3,2′:6′,3″-tpy and a conformationally flexible 3,2′:6′,3″-tpy metal-binding domain.