Stars and stripes: hexatopic tris(3,2′:6′,3″- terpyridine) ligands that unexpectedly form onedimensional coordination polymers


Stars and stripes: hexatopic tris(3,2′:6′,3″-terpyridine) ligands that unexpectedly form one-dimensional coordination polymers The preparation of a series of arene-centred tris(4,2′:6′,4″-terpyridine) and tris(3,2′:6′,3″-terpyridine) ligands provides an entry into hexatopic building blocks for coordination assemblies. The reaction of 1,3,5-trimethyl-2,4,6-tris{4-(3,2′:6′,3″-terpyridin-4′-yl)phenyl}-benzene with [Cu(hfacac)2]·H2O leads, not to an extended network, but to an unusual 1D-coordination polymer consisting of a series of alternating single and double loops.

The hexatopic ligands 1,3,5-tris(4,2′:6′,4″-terpyridin-4′-yl)benzene (1), 1,3,5-tris(3,2′:6′,3″-terpyridin-4′-yl)benzene (2), 1,3,5-tris{4-(4,2′:6′,4″-terpyridin-4′-yl)phenyl}benzene (3), 1,3,5-tris{4-(3,2′:6′,3″-terpyridin-4′-yl)phenyl}benzene (4) and 1,3,5-trimethyl-2,4,6-tris{4-(3,2′:6′,3″-terpyridin-4′-yl)phenyl}benzene (5) have been prepared and characterized. The single crystal structure of 1·1.75DMF was determined; 1 exhibits a propeller-shaped geometry with each of the three 4,2′:6′,4″-tpy domains being crystallographically independent. Packing of molecules of 1 is dominated by face-to-face π-stacking interactions which is consistent with the low solubility of 1 in common organic solvents. Reaction of 5 with [Cu(hfacac)2]·H2O (Hhfacac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) under conditions of crystal growth by layering resulted in the formation of [Cu3(hfacac)6(5)]n·2.8nC7H8·0.4nCHCl3. Single-crystal X-ray diffraction reveals an unusual 1D-coordination polymer consisting of a series of alternating single and double loops. Each of the three crystallographically independent Cu atoms is octahedrally sited with cis-arrangements two N-donors from two different ligands 1 and, therefore, cis-arrangements of coordinated [hfacac]− ligands; this observation is unusual among compounds in the Cambridge Structural Database containing {Cu(hfacac)2-N2} coordination units in which the two N-donors are in a non-chelating ligand.

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