Polynuclear coordination complexes of some polyisoindolines and polyphthalazines

Zhang, Yisheng (1993) Polynuclear coordination complexes of some polyisoindolines and polyphthalazines. Masters thesis, Memorial University of Newfoundland.

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Abstract

In an attempt to enhance the bulk extended magnetic properties of antiferromagnetically coupled Cu(II) complexes a series of tetranuclear, hexanuclear and octanuclear Cu(Il) coordination complexes of some dendritic polyphthalazine ligands was synthesized and studied. The ligands were obtained by reacting various polyalcohols with 4-nitro-1,2-dicyano-benzene to produce a series of polyphthalonitriles, then condensing with 2-aminopyridine to produce the polyisoindoline intermediates and finally ring expanding with aqueous hydrazine to form the polyphthalazines. Dinuclear complexes were also obtained by reacting two dinucleating polyisoindolines with Cu(II) salts. Analytical spectral, X-ray, and magnetic studies on the complexes reveal that the polyphthalazine ligands are able to bind two pairs, three pairs and four pairs of metal ions in triple bridged, spin-coupled dinuclear centers, one on each branch of the extended polyphthalazine ligands. Two tetranuclear Cu(II) nitrate complexes, [Cu₄(C-P)(μ₂-OH)₂(μ2-NO₃)₂(NO₃)₂(H₂O)₂](NO₃)₂4H₂O and [Cu₄(O-P)(μ₂-OH)₂(μ₂-NO₃)₂(NO₃)₂(H₂O)₂] (NO₃)₂10H₂O, of the tetranucleating polyphthalazines (O-P, C-P) have been characterized by single crystal X-ray diffraction. In these dinuclear centres two, five or six-coordinate Cu(II) ions are brought into close proximity and bridged by the phthalazine diazine (N₂) and hydroxide groups equatorially and by a bidentate nitrate group axially. The overall structure of the tetranuclear Cu(II) complex of O-P reveals that the Cu4 complexes are connected through bridging bidentate nitrates and hydrogen bonding interactions, forming a zig-zag, nanometre scaled, molecular tube with hydrophilic groups inside and hydrophobic groups outside. Variable-temperature magnetic susceptibility measurements on some complexes indicate that strong anti ferromagnetic couplings exist within each dinuclear centre, but across the ligand framework coupling is very weak. These polynuclear Cu(II) complexes usually exhibit cyclic voltammograms at positive potentials (V vs SSCE) associated with Cu(II)->Cu(I) reduction. -- Preliminary studies have also been carried out on the synthesis of a 'star-like' lithium phthalocyanine peripherally substituted with isoindoline and phthalazine groups in an attempt to generate a system with spin coupled centres linked to a macrocyclic core with extensive π conjugation.

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