Lanthanide coordination polymers with the formula [Ln (pydc) 2]

A new metal-valence tuning synthetic approach has been utilized to generate two new mixed-valence Cu (I, II) coordination polymers Cu2 (im) 3 and Cu3 (im) 4 (Him=imidazole), which are an unprecedented uninodal 4-connected 4.85 topological net and a 4-connected (4, 4) net, respectively.

A predesigned metal-organic building-block [CuI (2-pytz)] (2-Hpytz=3, 5-di-2-pyridyl-1, 2, 4-triazole) has been successfully used to synthesize four genuine supramolecular isomers.

The solvent effect of different polarities in hydro (solvo) thermal reaction of CuII and 2-ethylimidazole leads to the generation of two supramolecular isomers of triple-stranded helical and zigzag chain-like structures of CuI 2-ethylimidazolate.

[M2L2] 2 structures by varying the d10 metal and/or the ligand (M=CuI or AgI, L=ophen or obpy; Hobpy=1H-[2, 2'] bipyridinyl-6-one), and have successfully obtained three dimers-of-dimers: [Ag2 (ophen) 2] 2·6H2O (2), [Cu2 (obpy) 2] 2 (3), and [Ag2 (obpy) 2] 2·4.5H2O·0.5DMF (4). X-ray analyses of these structures show that interdimer M-M separations in [Ag2-(ophen)2]2 (3.199Å) are remarkably shorter than those in [Cu2 (ophen) 2] 2 (3.595Å). Shorter interdimer M-M separations are found in the structures of [M2 (obpy) 2] 2 (2.986 and 2.993Å in [Cu2 (obpy) 2] 2, 3.037 to 3.093Å in [Ag2 (obpy) 2] 2), in which the p systems are smaller than in the complexes with the ophen ligand. Detailed structural comparison of these dimers-of-dimers indicates that the interdimer, face-toface π-π interactions repulse rather than support the interdimer metal-metal attractive interactions. This study also yields qualitative comparison of the strengths between argentophilic, cuprophilic, and face-to-face π-π interactions. DFT calculations on the four dimers-of-dimers further support the above deduction. The structure of a trimer-of-dimers [Ag2 (obpy) 2] 3 (Ag-Ag 3.171 to 3.274Å) is further evidence that the oligomerization of the [M2L2] molecules is favored by stronger metallophilic and weaker face-to-face π-π interactions.