Structures and Magnetic Properties of an Antiferromagnetically Coupled Polymeric Copper(II) Complex and Ferromagnetically Coupled Hexanuclear Nickel(II) Clusters

Reactions between 2,6-diformyl-4-methylphenol (DFMF) and tris­(hydroxymethyl) aminomethane (THMAM = H₃L2) in the presence of copper­(II) salts, CuX₂ (X = CH₃CO₂^–, BF₄^–, ClO₄^–, Cl^–, NO₃^–) and Ni­(CH₃CO₂)₂ or Ni­(ClO₄)₂/NaC₆H₅CO₂, sodium azide (NaN₃), and triethylamine (TEA), in one pot self-assemble giving a coordination polymer consisting of repeating pentanuclear copper­(II) clusters {[Cu₂(H₅L^2–)­(μ-N₃)]₂[Cu­(N₃)₄]·2CH₃OH}_<i>n</i> (<b>1</b>) and hexanuclear Ni­(II) complexes [Ni₆(H₃L1^–)₂(HL2^2–)₂(μ-N₃)₄(CH₃CO₂)₂]·6C₃H₇NO·C₂H₅OH (<b>2</b>) and [Ni₆(H₃L1^–)₂(HL2^2–)₂(μ-N₃)₄(C₆H₅CO₂)₂]·3C₃H₇NO·3H₂O·CH₃OH (<b>3</b>). In <b>1</b>, H₅L^2– and in <b>2</b> and <b>3</b> H₃L1^– and HL2^2– represent doubly deprotonated, singly deprotonated, and doubly deprotonated Schiff-base ligands H₇L and H₄L1 and a tripodal ligand H₃L2, respectively. <b>1</b> has a novel double-stranded ladder-like structure in which [Cu­(N₃)₄]^2– anions link single chains comprised of dinuclear cationic subunits [Cu₂(H₅L^2–)­(μ-N₃)]⁺, forming a 3D structure of interconnected ladders through H bonding. Nickel­(II) clusters <b>2</b> and <b>3</b> have very similar neutral hexanuclear cores in which six nickel­(II) ions are bonded to two H₄L1, two H₃L2, four μ-azido, and two μ-CH₃CO₂^–/μ-C₆H₅CO₂^– ligands. In each structure two terminal dinickel (Ni₂) units are connected to the central dinickel unit through four doubly bridging end-on (EO) μ-azido and four triply bridging μ₃-methoxy bridges organizing into hexanuclear units. In each terminal dinuclear unit two nickel centers are bridged through one μ-phenolate oxygen from H₃L1^–, one μ₃-methoxy oxygen from HL2^2–, and one μ-CH₃CO₂^– (<b>2</b>)/μ-C₆H₅CO₂^– (<b>3</b>) ion. Bulk magnetization measurements on <b>1</b> show moderately strong antiferromagnetic coupling within the [Cu₂] building block (<i>J</i>₁ = −113.5 cm^–1). Bulk magnetization measurements on <b>2</b> and <b>3</b> demonstrate that the magnetic interactions are completely dominated by ferromagnetic coupling occurring between Ni­(II) ions for all bridges with coupling constants (<i>J</i>₁, <i>J</i>₂, and <i>J</i>₃) ranging from 2.10 to 14.56 cm^–1 (in the <i>Ĥ</i> = –<i>J</i>₁(<i>Ŝ</i>₁<i>Ŝ</i>₂) – <i>J</i>₁(<i>Ŝ</i>₂<i>Ŝ</i>₃) – <i>J</i>₂(<i>Ŝ</i>₃<i>Ŝ</i>₄) – <i>J</i>₁(<i>Ŝ</i>₄<i>Ŝ</i>₅) – <i>J</i>₁(<i>Ŝ</i>₅<i>Ŝ</i>₆) – <i>J</i>₂(<i>Ŝ</i>₁<i>Ŝ</i>₆) – <i>J</i>₃(<i>Ŝ</i>₂<i>Ŝ</i>₆) – <i>J</i>₃(<i>Ŝ</i>₂<i>Ŝ</i>₅) – <i>J</i>₃(<i>Ŝ</i>₃<i>Ŝ</i>₅) convention)