Synthesis and Molecular Structure of the First Metallamacrocyclic Bi(III)-Cu(II) 15-MC-5 Complex Derived from Pyrazinohydroxamic Acid

Abstract

Polynuclear metallamacrocyclic complexes named as metallacrowns are considered as a promising exceptional class of macroheterocyclic compounds that structurally resembles crown ethers. In this communication, we report a general synthetic approach and characterization of the first metallamacrocyclic Bi(III)-Cu(II) 15-MC-5 complex derived from pyrazinohydroxamic acid. The molecular and crystal structures of complex were determined from single-crystal X-ray diffraction studies. The single-crystal structure reveals the classic metallamacrocyclic 15-MC-5 configuration. The Bi(III) ion is located at the center of the 15-MC-5 ring consisting of five [Cu(II)-N-O] repeat units. Detailed NBO and QTAIM studies based on DFT calculations were carried out for {Bi[15-MC Cu(II)Pyzha-5]} 3+ species.

Water-Soluble Bismuth(III) Polynuclear Tyrosinehydroximate Metallamacrocyclic Complex: Structural Parallels to Lanthanide Metallacrowns

“…Energies of copper(II) bonds with the oxime and carbonyl oxygen atoms are closer: 35.9–40.4 and 46.3–47.0 kcal/mol, respectively. In general, the bonding situation in the hydroximate chelates of the [M(15-MC Cu(II)Tyrha -5)] 3+ complexes is similar to that in the 15-metallacrowns-5 analyzed by us earlier with use of QTAIM in conjunction with the hybrid functionals τ-HCTHhyb [ 33 ] and M06 [ 29 , 42 , 43 ]. This makes the SR-PBE/rL2 calculations appropriate for description of the hydroximate 15-metallacrowns-5.…”

“…A comparison of the related complex of bismuth with pyrazinohydroxamic acid [ 29 ] reveals significant differences in the crystal packing between these two compounds. The molecules of the bismuth complex with pyrazinohydroximate ligands form an infinite three-dimensional (3D) network due to N ... H interactions and π ... π stacking.…”

“…On the basis of our calculations, one can conclude that accumulation of the density at the axial positions of the Bi 3+ ion together with its decreased positive charge prevents filling the Bi 3+ coordination sphere by the solvent molecules. This leads to the more effective bonding with the HO − negative ion in 1 (as well with Cl − in the pyrazinohydroximate complex [ 29 ]). As a result, the Bi 3+ ion in the complex is characterized by the lower coordination number as compared with the La(III) 15-metallacrowns-5 where the La 3+ central ion bears four H 2 O molecules at the axial positions [ 33 ].…”

“…A relevant aspect of this structure is that the ligand scaffold prefers early lanthanides characterized by the same charge and similar ionic radii as Bi 3+ . Recently, we have demonstrated the first metallamacrocyclic 15-MC-5 complex constructed from Cu 2+ and Bi 3+ metal centers and pyrazinohydroxamic moieties [ 29 ]. The single-crystal structure reveals the classic metallamacrocyclic 15-MC-5 configuration.…”