An investigation of the positional isomeric effect of terpyridine derivatives:: Self-assembly of novel cadmium coordination architectures driven by N-donor covalence and π...π non-covalent interactions

Four cadmium compounds based on two pyridyl substituted terpyridine isomers, namely {[Cd-3(L1)(2)(SCN)(6)](THF)(2)}(n) (1), [Cd-2(L1)(CH3OH)Cl-4](n) (2), [Cd-2(L-2)(2)(N-3)(4)] (3) and [Cd-2(L-2)(2)(SCN)(4)] (4) (L1 = 4'-(3-pyridyl)-2,2':6',2 ''-terpyfidine, L2 = 4'-(2-pyridyl)-2,2':6',2 ''-terpyridine) have been synthesized and characterized by IR, elemental analyses, and luminescent spectroscopy with the purpose of investigating the influence of isomeric effect on network assembly. In compounds 1 and 2, L1 as a mono-tridentate bridging ligand links Cd-11 atoms into ID grid-like and 2D wave-like polymers. In contrast, in compounds 3 and 4, L2 as a chelating ligand forms Cd-II dimeric structures. The different coordination behaviors and the positional isomer effect were discussed under the same reaction conditions. In addition, three kind of pi...pi interactions in the four compounds were summarized, two of which could not be observed on tpy-based complexes. (C) 2008 Elsevier Ltd. All rights reserved.