Cation-/Ligand-Induced Solvent-Assisted Transformations of Zn(II) and Cu(II) Complexes Featuring Single-Pocket Multidentate Chelating Members

A new family of single-pocket metal complexes bearing O,N,O-tridentate and O,N-bidentate chelating members {Cu, 1b (P21/n); Ni, 1c (C2/c); Mn, 1d (I2/a); Cu, 2b; 2c (both P21/c)}, starting from synthesized fully characterized Zn(II) (1a; I2/a) Cu(II) (2a; C2) precursors, were conveniently prepared via cation-induced solvent-assisted ligand-induced transformations. Herein, we show multistep transformations cis-1a → trans-1b cis-1c cis-1d, as well all-trans 2a 2b 2c. All processes are one-way irreversible, substantiated by thermodynamic aspects (enthalpies based on Gibbs free energies) derived density functional theory calculations. On the other hand, complex 2a′ (C2/c; a polymorphic form 2a) was obtained through routine synthetic procedure. The compounds have been established various spectroscopic techniques (infrared, UV–vis, ESI-MS, 1H, 13C NMR), elemental analysis, X-ray crystallography. Single-crystal studies reveal that 1a–d exhibit pseudo-octahedral geometry around each center, with displaying four-coordinate seesaw sphere (Addison parameter; τ = 0.42), while (τ 0.00), 0.00) possess perfect square-planar configuration center. Furthermore, distortion is stabilized presence peripheral O-donor atoms bulky −OMe group, virtue its size, increased bond lengths angles accommodated. Ligand substitution induced coordination transformation quasi-square-planar to 2b. Assessment metric parameter shows distances between two Cu–Omethoxy all largely positive due Jahn–Teller distortion, indicating an unprecedented tetragonal bipyramidal in 1b.