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

Abstract

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, [Zn L aldi (Cl)] or [Zn L aldi ](BF 4 ). 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(BF 4 ) 2 to form the five coordinated complex [Zn II L 2 ](BF 4 ), while the reaction of L 1 , L 3 and L 4 with ZnCl 2 yields the mononuclear five coordinated complexes [Zn II L aldi (Cl)] with an uncoordinated alcohol donor group. X-ray crystal structure determinations of [Zn L 1 (Cl)], [Zn L 4 (Cl)] and [Zn L 2 ](BF 4 ) confirmed they are mononuclear. The Zn(II) ion in [Zn L 4 (Cl)] is in a distorted square pyramidal environment whilst Zn(II) is almost exactly between square pyramidal and trigonal bipyramidal distorted geometry in [Zn L 1 (Cl)] CH 3 OH and [Zn L 2 ](BF 4 ). Computational investigations of studied complexes are performed at B3LYP/6-31G (d,p) (LANL2DZ) in vacuum.