X-ray and FT-IR studies of structures of cyclic oxaalkyl diamide of o-phthalic acid and its complex with lead(II) perchlorate

The crystals of cyclic oxaalkyl diamide of o-phthalic acid (CPhDA) and its complex with lead(II) perchlorate (CPhDA–Pb(ClO4)2–H2O (6:2:3)) were obtained from acetonitrile and were studied using X-ray crystallography and FT-IR spectroscopy. CPhDA crystallises in the centrosymmetric space group (P21/n) of monoclinic system, while its complex with Pb(ClO4)2 in the space group R3¯ of rhombohedral system. The conformation of CPhDA does not change significantly upon coordination of the Pb2+cation. Within the complex structure all six carbonyl oxygen atoms of the three CPhDA ligand molecules coordinate the Pb2+ cation with comparable bond lengths forming a cationic complex [Pb(CPhDA)3]2+. One water molecule occupies the centro-symmetric position in the cationic [(CPhDA)3⋯Pb2+⋯(H2O)⋯Pb2+⋯(CPhDA)3] dimeric structure. The FT-IR spectrum of the complex shows the characteristic shifts of amide I and amide II bands as all oxygen atoms of the carbonyl group are involved in complexation.

Graphical abstractCyclic oxaalkyl diamide of o-phthalic acid (CPhDA) and its complex with lead(II) perchlorate [CPhDA–Pb(ClO4)2–H2O (6:2:3)] in the crystalline form were obtained. The compounds were characterised by single crystal X-ray diffraction and by the FT-IR spectroscopy. The conformation of the CPhDA does not change significantly upon coordination of the Pb2+cation.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The complex formation of lead(II) and macrocyclic amide–ether ligand was studied. ► The crystal structures of the ligand and its complex with Pb2+ were determined. ► The conformation of the ligand did not change upon coordination to Pb2+. ► Six carbonyl oxygen atoms of the three ligand molecules coordinate Pb2+. ► The FT-IR spectrum of the complex shows the shifts of amide I and II bands.