Structures of N,N′,N′′-tris(3-pyridinyl)-1,3,5-benzenetricarboxamide and its nano-scopic zinc(II) coordination ring and their interaction with calf thymus DNA

N,N′,N′′-tris(3-pyridinyl)-1,3,5-benzenetricarboxamide monohydrate 3-TPB·H2O and an unprecedented cyclic dimeric oligoamide zinc complex [Zn2(3-TPB)2Cl4]·2H2O (1) have been synthesized and their crystal structure were reported. Different from anhydrous 3-TPB, which is s-conformation, 3-TPB·H2O adopts aas-conformation. All amide hydrogen form H-bonds. Zn ion in dimeric [Zn2(3-TPB)2Cl4]·2H2O located in a tetrahedron coordination environment. Two 3-TPB ligands and two Zn(II) ions link alternatively to form a 28-membered ring. The Zn⋯Zn distance in the ring is 11.162(5) Å. One pyridine nitrogen atom is free. The nano-size macrocyclic framework of 1 is stable up to 390 °C. 3-TPB·H2O and complex 1 have similar fluorescence emission ∼450 nm. Fluorescence titration shows that calf thymus DNA can quench the fluorescence 3-TPB in aqueous solution. However, calf thymus DNA has no interaction with complex 1.