Synthesis, Spectroscopic and Electrochemical Studies of Mononuclear Fe(II) and Ni(II) Complexes Containing a Macrocyclic Ligand Derived from Pyridine-2,6-dicarboxaldehyde and 1,2-Bis(2-aminoethoxy) Ethane

The cyclic (2+2) template condensation of 2,6-pyridinedicarboxaldehyde with 1,2-bis(2-aminoethoxy) ethane using Pb(SCN)2 as the metal source gave dinuclear lead(II) complex, Pb2L1(SCN)4 (1), where L1 is tetra-Schiff-base macrocycle. The transmetallation treatment of 1 with suitable metal perchlorate yield [FeL1](ClO4)2 (2) and [NiL1](ClO4)2 (3). The complexes (2 & 3) have been characterized by elemental analyses, IR, UV-visible, and ESI-MS spectroscopy. Based on spectral data, octahedral geometry may be proposed for these complexes. The electrochemical behavior of iron and nickel complexes is reported.Keywords: Macrocyclic complexes; Spectroscopic studies; 1,2-Bis(2-aminoethoxy) ethane; Charge transfer.© 2011 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: 10.3329/jsr.v3i3.7231 J. Sci. Res. 3 (3), 609-617 (2011)

Pyridine-Derived Tetrapodal Ligands with NO4 and NN4 Donor Sets

The Mg2+ assisted synthesis of a pyridine-derived tetraalcohol ligand with an NO4 donor set is described. 2,6-Diethylpyridine reacts cleanly with aqueous formaldehyde solution in the presence of 1 equivalent of MgSO4 hydrate in a pressurised vessel to give the quadruply hydroxymethylated product 2,6 -C5H3N[CMe(CH2OH)2]2 (1) as a crystalline solid. Two alkali/alkaline earth metal perchlorate adducts of 1 have been structurally characterised, viz. [(1)2 • LiClC4] (6) and [(1)2 • Ba(ClO4)2 ] (7). The ligand adopts a bridging coordination mode in both 6 (distorted tetrahedral coordination of Li+) and 7 (square prismatic coordination of Ba2+). The further derivatization of 1 leads to the tetratosylate (2) and the tetraazide (3), both of which have been obtained in pure form for the first time. Reduction of 3 gives the pentaamine ligand 2,6-C5H3N[CMe(CH2NH2)2]2 (4), isolated as the tetrakis(hydrobromide) salt 4 • 4 HBr. The presence of four ammonio substituents and an unprotonated pyridine nitrogen atom in the solid state has been unequivocally established by an X-ray structural analysis.