Selective derivatisation of aza macrocycles

Abstract

A range of selectively functionalised compounds derived from 1,4,7-triazacyclononane ([9]aneN₃), including 4,7-bis(2-hydroxy-2-methylpropyl)-1,4,7-triazacyclononane-1-carbaldehyde (H₂L¹), 1-benzyl-4,7-bis(2-hydroxy-2-methylpropyl)-1,4,7-triazacyclononane (H₂L²) and 1,4-bis(2-hydroxy-2-methylpropyl)-1,4,7-triazacyclononane (H₂L³), has been prepared. The structure of H₂L³·CHCl₃ shows a disordered macrocyclic ring with the major conformer refining to a site occupancy of 0.663(8), and both disordered rings adopting a [333] conformation. The pendant alcohol arms were not disordered and were found to be hydrogen bonded to a CHCl₃ solvate molecule with H ⋯ O(1) and H ⋯ O(4) distances of 1.73 and 1.81 Å respectively. The structure of Na[Cu(H₂L¹)(NCMe)][BF₄]₂[NO₃] shows the copper(II) centre in the [Cu(H₂L¹)(NCMe)]²⁺ cation bound to two amine donors and two alcohol donors of H₂L¹ and to a MeCN molecule. The Cu–N bond lengths lie in the range 1.984(3)–2.015(3)Å. Both alcohol donors are protonated, with one short Cu–O(16) bond of 1.963(3)Å and one long Cu–O(21) bond of 2.252(3)Å. There is also a sixth longer-range interaction of the copper(II) centre with the amide N [N(1)] of H₂L¹ at a distance of 2.611(5)Å, confirmed by the loss of planarity of the C(2)–C(9)–N(1)–C(10)–O(11)–H(10) amide fragment to give a dihedral angle between the planes defined by C(2)–C(9)–N(1) and N(1)–C(10)–O(11)–H(10) of 27.1(4)°. The structure is completed by interaction of O(11) with a Na⁺ion which itself bridges to BF₄^– counter anions leading to a central infinite core of [Na(BF₄)₂]^– aggregates onto which are attached the [Cu(H₂L¹)(NCMe)]²⁺ cations. The complex [Cu(H₂L²)(OH₂)][NO₃]₂ shows the six-co-ordinate copper(II) centre bound to the three amine and two alcohol donors of H₂L² and to one water molecule. There are four short bonds [to N(7), N(4), O(40) and O(1)] in the range 1.961(5)–2.073(6)Å and two longer bonds to N(1) and O(70) at 2.308(5) and 2.313(5)Å respectively. The H atoms of the water molecule [O(1)] and one of the pendant arms [O(40)] also make hydrogen-bonding contacts with the nitrate counter ions.