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

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 } . 0.6CHCl 3 ] n , [{Co( 3 ) 2 (NCS) 2 } . 4CHCl 3 . 0.25H 2 O] n , [{Co( 4 ) 2 (NCS) 2 } . 4CHCl 3 ] n , [Co 2 ( 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 } . 2.2CHCl 3 ] 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.