Synthesis of the macrotricyclic ligands 8,18 dioxa-1,5,11,15-tetraaza-[13.5.2.25,11]-eicosane (L1) and 7,16 dioxa-1,4,10,13-tetraaza-[11.5.3.34,10]-octadecane (L2). Crystal structures of the copper(II) complexes, [Cu(L1)](ClO₄)₂ and [Cu(L2)](ClO₄)₂·CH₃NO₂

摘要

Two isomeric polymacrocyclic ligands, L1 and L2 have been synthesized and the corresponding copper(II) complexes prepared. Reaction of the macrobicycle 15-oxa-1,5,8,12-tetraazabicyclo[10.5.2]nonadecane (L3) with diglycolyl chloride in base, yielded a diamide and following reduction, led to formation of the tricyclic ligand L1. A single crystal X-ray study of the blue, [Cu(L1)](ClO₄)₂, (C2/c monoclinic, a = 33.518(4), b = 16.3778(18), c = 13.7391(19) Å, β = 90.56(3)°, V = 7541.8 (16) Å3, Z = 12, R (F₀) = 0.065, R_w = 0.066) reveals the presence of two independent [Cu(L1)]2+ cations displaying either five- or six- coordinate geometry. In the former distorted square pyramid, only one of the ether oxygens of the ligand is bound to the copper center, Cu–N₁ = 2.083(7), Cu–N₂ = 2.076(9), Cu–O₁ = 2.276(11) Å and the Cu–O bond is at the longer end of axial distances of this type. However, the six-coordinate species is considerably more distorted, with in equivalence in both the metal-nitrogen and -oxygen bonds, Cu–N₁ = 2.082(7), Cu–N₂ = 2.096(7), Cu–N₃ = 2.103(7), Cu–N₄ = 2.068(7), Cu–O₁ = 2.597(7), Cu–O₂ = 2.427(7) Å, N(1)–Cu–O(1) = 71.0(2), N(3)–Cu–O(1) = 71.6(2), O(1)–Cu–O(2) = 64.6(2). The ligand L2 has been synthesized by reaction of the ten-membered macrocycle 1-oxa-4,8-diaza decane, (10-N₂O) in dichloromethane with two moles of chloroacetyl chloride. The bis-pendant-armed product was further reacted with another mole of 10-N₂O to yield a tricyclic diamide. The crystal structure of the intermediate diamide (Pnam, no.62 orthorhombic, a = 13.712(9), b = 9.111(5), c = 15.110(7) Å, V = 1887.6 Å3, Z = 8, R = 0.103, R_w = 0.103) has been determined. Subsequent reduction led to the formation of L2. The ligand is readily protonated to give a diammonium cation, [H₂L2]2+. A single crystal structure of the [Cu(L2)](ClO₄)₂·CH₃NO₂ complex (P2₁/c, monoclinic a = 9.731(3), b = 16.065(5), c = 18.076(6) Å, β = 91.627(7)°, V = 2824.5 (15) Å3, Z = 4, R₁ = 0.090, wR₂ = 0.215) indicates considerable asymmetry in the cyclam plane (Cu–N₁ = 2.099(11), Cu–N₂ = 2.061(10), Cu–N₃ = 2.065(10), Cu–N₄ = 2.111(11), Cu-O₁₂ = 2.410(7) Å) with one of the ether oxygens is coordinated to the metal, while the other is unbound. The ligand adopts a syn-configuration with both the attached macrocyclic units on the same side of the cyclam ring. Spectroscopic studies are reported.