Template synthesis and characterisation of a copper(II) complex of a half-cyclised tetraaza ligand derived from 1,8-diaminonaphthalene, nitroethane and formaldehyde

Abstract

Reaction of Cu(BF₄)₂.xH₂O with 1,8-diaminonaphthalene, nitroethane and formaldehyde in ethanol in the presence of triethylamine yields an air sensitive copper(II) complex of 1,3-bis (8-aminonaphthyl-1-amino)- 2-methyl-2-nitropropane (L) as Cu(L)-(BF₄)₂.C₂H₅OH, <b style="mso-bidi-font-weight:normal">1</b>. Molecular mechanics calculations coupled with the solution conductivity data indicate a

<span style="font-size:12.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:="" calibri;mso-fareast-theme-font:minor-latin;mso-ansi-language:en-in;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="">distorted square pyramidal N₄F coordination sphere for the copper atom in <b style="mso-bidi-font-weight:normal">1</b> with the fluorine atom occupying the apical position and the metal atom lifted a bit from the N₄ plane. This is supported by the rhombic EPR spectra of <b style="mso-bidi-font-weight: normal">1</b>(g₃= 2.389, g₂= 2.069 and g₁ = 2.023 ; <i style="mso-bidi-font-style:normal">A</i>₃ = 137.9 × 10^-4 cm^-1, <i style="mso-bidi-font-style:normal">A</i>₂ = 18.1 x 10^-4 cm^-1 and <i style="mso-bidi-font-style:normal">A</i>₁ = 17.7 x 10.4 cm^-1). The complex <b style="mso-bidi-font-weight: normal">1</b> undergoes a somewhat irreversible two-electron ligand oxidation at 0.36 V vs SCE in dimethylformanide. The cyclic counterpart of <b style="mso-bidi-font-weight:normal">1</b> is not at all formed in the synthetic scheme adopted here.</span>