Coordination polymers with 4′-(4-(anthracen-9-yl)phenyl)- and 4′-(4-(naphthalen-1-yl)phenyl)-4,2′:6′,4″-terpyridines: Mono-, di- and heptazinc(II) nodes

Reactions of 4′-(4-(anthracen-9-yl)phenyl)-4,2′:6′,4″-terpyridine (2) with zinc(II) acetate lead to helical one-dimensional polymers [{Zn(OAc)2(2)}n] which crystallize either as racemates or the homochiral polymer containing mononuclear {Zn(OAc)2} nodes linked by divergent 4,2′:6′,4″-terpyridine ligands. In contrast, when 4′-(4-(naphthalen-1-yl)phenyl)-4,2′:6′,4″-terpyridine (3) reacts with zinc(II) acetate, a one-dimensional coordination polymer [{Zn2(μ-OAc)4(3)}n] in which the metal nodes are dinuclear {Zn2(μ-OAc)4} units is formed. This mimics the assembly formed when the ligand is 4′-(4-biphenylyl)-4,2′:6′,4″-terpyridine (1). In addition, crystals of [{Zn7(μ-OAc)10(μ4-O)2(3)}n] were isolated and structural determination reveals a one-dimensional coordination polymer in which each ligand 3 bridges between {Zn7(μ-OAc)10(μ4-O)2} clusters. Ligands 2 and 3 are both emissive in solution and in the solid state. The emission spectra of ethanol solutions of [{Zn(OAc)2(2)}n] and [{Zn2(μ-OAc)4(3)}n] are consistent with dissociation of the complexes, the emission maxima mimicking those of the free ligands. The emission of 2 in the solid state is essentially quenched upon complexation with zinc(II) acetate, whereas on going from 3 to [{Zn2(μ-OAc)4(3)}n], a red-shift is observed (416 to 434 nm) without change in the quantum yield (ca. 1.6%).