Explaining How α-Hydroxamate Ligands Control the Formation of Cu(II)-, Ni(II)-, and Zn(II)-Containing Metallacrowns

Abstract

Four different crystal structures for quinolinehydroxamic acid (QuinHA) and picolinehydroxamic acid (PicHA) MCs with Cu­(II) and Ni­(II), and solution studies on the formation of Cu­(II), Ni­(II), and Zn­(II) MC complexes with QuinHA, PicHA, and pyrazylohydroxamic acid (PyzHA) are described. In polynuclear complex 1, [Cu5(QuinHA-2H)4(NO3)­(DMSO)4]­(NO3), the metallamacrocyclic cavity is formed by four Cu­(II) ions and four doubly deprotonated hydroximate ligands, and the center of the cavity is occupied by the fifth Cu­(II) ion coordinated by four hydroximate oxygen atoms. The complex 2, [Cu10(PicHA-2H)8(H2O)4(ClO4)3]­(ClO4)·4H2O, exhibits a dimeric structure based on two pentanuclear collapsed 12-MC-4 Cu4(PicHA-2H)4 fragments united by two chiral capping Cu­(II) ions exo-coordinated to the peripheral vacant (O,O′) chelating units of each tetranuclear collapsed MC moiety. 3, [CaNi5(QuinHA-2H)5(H2O)2(Py)10]­(NO3)2, and 4, [CaNi5(PicHA-2H)5(DMF)2(Py)8]­(NO3)2, are planar 15-membered rings consisting of a PicHA or QuinHA ligand, respectively. To understand fully the correlation between species isolated in the solid state and those presented in solution, the solution equilibria were investigated, showing the dependence of the MCs topologies and stability constants (log β) on the ligand structure and metal ion.

Thermodynamic Stability and Speciation of Ga(III) and Zr(IV) Complexes with High-Denticity Hydroxamate Chelators

“…The stoichiometry of the complexes was evaluated by ESI-MS, frequently used as the first step in the determination of metal complex stoichiometry and already previously employed. ,, When the fact that ESI-MS is not able to distinguish the ionizable protons in the species is taken into account, this method can be successfully applied to evaluate the metal to ligand stoichiometry directly from the m / z values. For all of the investigated systems, an analysis of the ESI-MS data (collected for various metal to ligand molar ratios) revealed only mononuclear complexes (for details see Figure S3 and Table S1 in the Supporting Information).…”

Quadruple bridged-carbonate supported dodecanuclear [Ni8Ca4] coordination cluster

“…The Ni1 atom shows a distorted octahedral environment (as shown by the SHAPE analysis, see Table S1 in the ESI †) 61 where the equatorial positions are occupied by two phenoxide O atoms (O1a, O2a) from the L 2À ligand, one carbonate O atom (O11) and the imine N atom (N1) from the L 2À ligand. The axial positions are occupied by one phenoxide O atom (O6) from the L 2À ligand and one O atom (O16) from the coordinated dmf molecule (Fig.…”

“…The Ni2 atom also adopts a distorted octahedral geometry (as shown by the SHAPE analysis, see Table S1 in the ESI †) 61 with the equatorial positions occupied by two phenoxide O atoms (O6a and O7) from the L 2À ligand, one O atom (O12) from the coordinated carbonate anion and the imine nitrogen atom (N3) from the L 2À ligand. The axial positions are occupied by an oxygen atom (O13) from another coordinated carbonate ion and a phenoxide O atom (O1a) from a L 2À ligand.…”

“…In fact, a search in the CCDC database (July 2023) shows that there are only eight examples with a Ni II -O-Ca II moiety. [56][57][58][59][60][61][62] Among these eight complexes, there are four NiCa dimers, 56,58,59,62 one Ni 2 Ca trimer, 57 one Ni 3 Ca tetramer 60 and two Ni 5 Ca hexamers, 61 showing that the field of polynuclear Ni-Ca clusters remains almost unexplored.…”

Synthesis, Structural and Physicochemical Characterization of a Titanium(IV) Compound with the Hydroxamate Ligand N,2-Dihydroxybenzamide

“…The organic molecule N,2-dihydroxybenzamide (H2dihybe) (Scheme 1A) incorporates a hydroxamate group in addition to the phenoxy group in the ortho-position and exhibits a rich coordination chemistry with many transition metals [31][32][33][34][35][36][37][38][39][40] with potential applications in various fields ranging from medicine [41][42][43] to materials [44], and physical sciences [40,45]. Scheme 1.…”