New macrocyclic dioxotetraamines bearing 2-pyridylmethyl as functional donor pendant(s): synthesis, properties and crystal structure of their copper(II) complexes †

Abstract

Two new macrocyclic dioxotetraamines 4-(pyridin-2-ylmethyl)-1,4,7,10-tetraazacyclotridecane-11,13-dione (H 2 L 1 ) and 4,7-bis(pyridin-2-ylmethyl)-1,4,7,10-tetraazacyclotridecane-11,13-dione (H 2 L 2 ) have been synthesized and characterized. The solution behaviors of their copper() complexes have been studied with ESR, UV/VIS and cyclic voltammetric techniques. Reaction of H 2 L 2 with Cu(O 2 CMe) 2 in methanol solution yielded a doubly deprotonated dioxotetraamine copper() complex, [CuL 2 ]ؒ6H 2 O, the structure of which has been determined by X-ray diffraction analysis. The Cu atom is five-co-ordinated by four basal nitrogens and one pendant pyridine nitrogen, forming a distorted square pyramid in which N(21) of the pendant pyridine nitrogen is at the apical site. The Cu᎐N(21) bond distance [2.203(7) Å] is longer than the basal average Cu᎐N bond length [1.985(4) Å] due to the Jahn-Teller effect.