Unsymmetrical tripodal amines containing one pyridine-armed with N3O2-donor set: Coordination chemistry with zinc(II) and theoretical studies

Abstract

The synthesis of two known unsymmetrical N-capped tripodal amines, 3-((2-aminoethyl)(pyridin-2-ylmethyl)amino)propan-1-ol (3) and 3-((3-aminopropyl)(pyridin-2-ylmethyl)amino)propan-1-ol (4) is reported. They feature a longer 3-hydroxypropyl arm than in previously employed analogues (2-hydroxyethyl and ethylamino arms or 2-hydroxyethyl and propylamino arms in 1 and 2, respectively). Both of these tripodal amines, 3 and 4, are equipped with a 2-methylpyridyl-arm, a 3-hydroxypropyl arm and either an ethylamino-arm (3) or a propylamino-arm (4). The amines, 3 and 4, have been employed in one pot condensation reactions with salicylaldehyde and its derivative in the presence of zinc salts to generate a series of new mononuclear complexes, [ZnLaldi(Cl)] or [ZnLaldi](BF4). The complexes obtained here aren't exhibit arm-length dependence. The reactivity of the ligands with zinc chloride and zinc bis (tetrafluoroborate) depends on the anion present. Ligand L-2 reacts with Zn(BF4)(2) to form the five coordinated complex [(ZnL2)-L-II](BF4), while the reaction of L-1, L-3 and L-4 with ZnCl2 yields the mononuclear five coordinated complexes [(ZnLaldi)-L-II(Cl)] with an uncoordinated alcohol donor group. X-ray crystal structure determinations of [ZnL1(Cl)], [ZnL4(Cl)] and [ZnL2](BF4) confirmed they are mononuclear. The Zn(II) ion in [ZnL4(Cl)] is in a distorted square pyramidal environment whilst Zn(II) is almost exactly between square pyramidal and trigonal bipyramidal distorted geometry in [ZnL1(Cl)] CH3OH and [ZnL2](BF4). Computational investigations of studied complexes are performed at B3LYP/6-31G (d,p) (LANL2DZ) in vacuum. (C) 2017 Published by Elsevier B.V.