Synthesis and Characterisation of Macrocycles Containing both Tetrazole and Pyridine Functionalities

The syntheses of tetra-tetrazole macrocycles containing at least one 2,6-bis(tetrazole)pyridine unit, linked by a variety of n-alkyl (n = 3, 5, 7 or 9 carbon atoms) chain lengths, are described. There has been no previous incorporation of the pyridine moiety into a tetra-tetrazolophane macrocycle. The crystal structure of one such tetra-tetrazole macrocycle has also been structurally characterised and revealed a bowl-shaped conformation

Coordination Studies of Copper(II), Cobalt(II) and Iron(II) with Isomeric Pyridyl-Tetrazole Ligands

The reaction of 2-(2H-tetrazol-5-yl)pyridine (L1) with 1,6-dibromohexane results in formation of the isomers 2-(6′′-bromohexyl-(1-tetrazol-5-yl)pyridine (L2) and 2-(6′′-bromohexyl-(2-tetrazol-5-yl)pyridine (L3). Coordination reactions of L2 and L3 with CuCl2·2H2O, Co(SCN)2 and Fe(ClO4)2·H2O yielded the strongly coloured solids [Cu(II)(L2)Cl2]2 (1), [Cu(II)(L3)Cl2]2 (2), [Co(II)(L2)2(NCS)2] (3), [Co(II)(L3)2(NCS)2] (4), [Fe(II)(L2)2(H2O)2](ClO4)2 (5) and [Fe(II)(L3)2(H2O)2](ClO4)2 (6), containing high-spin metal centres for the Co(II) and Fe(II) compounds. X-ray crystal structures were obtained for complexes 1–5. In each complex, ligands L2 and L3 coordinate to the metal centre through the pyridyl N atom and the 1-N site of the tetrazole ring, and the pyridyl-tetrazole ligand remains planar in all cases except 3. Complexes 1 and 2 comprise a central Cu2Cl2 dimeric core with Cu(II) in an essentially square-pyramidal coordination environment. Complexes 3 and 4 contain Co(II) in a distorted octahedral coordination environment. In 3, the pyridyl and tetrazole rings of L2 are twisted with respect to each other and the complex adopts a puckered conformation in its equatorial plane. Complex 5 contains water molecules coordinated to Fe(II) in the axial sites, which form hydrogen bonds to the perchlorate counter anions

Coordination Studies of Copper(II), Cobalt(II) and Iron(II) with Isomeric Pyridyl-Tetrazole Ligands

The reaction of 2-(2H-tetrazol-5-yl)pyridine (L1) with 1,6-dibromohexane results in formation of the isomers 2-(6′′-bromohexyl-(1-tetrazol-5-yl)pyridine (L2) and 2-(6′′-bromohexyl-(2-tetrazol-5-yl)pyridine (L3). Coordination reactions of L2 and L3 with CuCl2·2H2O, Co(SCN)2 and Fe(ClO4)2·H2O yielded the strongly coloured solids [Cu(II)(L2)Cl2]2 (1), [Cu(II)(L3)Cl2]2 (2), [Co(II)(L2)2(NCS)2] (3), [Co(II)(L3)2(NCS)2] (4), [Fe(II)(L2)2(H2O)2](ClO4)2 (5) and [Fe(II)(L3)2(H2O)2](ClO4)2 (6), containing high-spin metal centres for the Co(II) and Fe(II) compounds. X-ray crystal structures were obtained for complexes 1–5. In each complex, ligands L2 and L3 coordinate to the metal centre through the pyridyl N atom and the 1-N site of the tetrazole ring, and the pyridyl-tetrazole ligand remains planar in all cases except 3. Complexes 1 and 2 comprise a central Cu2Cl2 dimeric core with Cu(II) in an essentially square-pyramidal coordination environment. Complexes 3 and 4 contain Co(II) in a distorted octahedral coordination environment. In 3, the pyridyl and tetrazole rings of L2 are twisted with respect to each other and the complex adopts a puckered conformation in its equatorial plane. Complex 5 contains water molecules coordinated to Fe(II) in the axial sites, which form hydrogen bonds to the perchlorate counter anions

First X-ray structural characterisation of host-guest interactions in tetra-tetrazole macrocycles

The syntheses of tetra-tetrazole macrocycles, containing two 1,3-bis(tetrazole)benzene units linked by a variety of n-alkyl (n = 3, 5, 7 or 9 carbon atoms) chain lengths, are described. The crystal structures of two 1,3-bis(tetrazole)benzenes containing pendant bromoalkyl chains (n = 3 or 5) are reported. A tetra-tetrazole macrocycle has also been structurally characterised and contains an unexpected “host-guest” interaction through binding of a chloroform solvent molecule. The resulting deviation of the macrocycle from planarity results from a combination of the “host-guest” interaction and strong intermolecular interactions between adjacent tetrazole and phenylene rings