Preparation of a chiral, 2-dimensional network containing metallacrown and copper benzoate building blocks

Synthesis and crystal structure of a penta-copper(II) 12-metallacrown-4: cis-di-aqua-tetra-kis-(di-methyl-formamide-κO)manganese(II) tetra-kis-(μ3-N,2-dioxido-benzene-1-carboximidate)penta-copper(II) di-methyl-formamide monosolvate

The title compound [Mn(OH₂)₂(C₃H₇NO)₄][Cu₅(C₇H₄NO₃)₄]·C₃H₇NO or cis-[Mn(H₂O)₂(DMF)₄]{Cu[12-MC_Cu(II)N(shi)-4]}·DMF, where MC is metallacrown, shi³⁻ is salicyl­hydroximate, and DMF is N,N-di­methyl­formamide, consists of a penta­copper(II) 12-metallacrown-4 anion that is charged-balanced with the cis-[Mn(DMF)₄(OH₂)₂]²⁺ cation. In the {Cu[12-MC_Cu(II)N(shi)-4]}²⁻ anion, all four Cu^II ions of the metallacrown ring and the one Cu^II ion of the central cavity are four-coordinate with a square-planar geometry. The Mn^II counter-cation is six-coordinate with an octa­hedral geometry.

The title compound, [Mn(C₃H₇NO)₄(H₂O)₂][Cu₅(C₇H₄NO₃)₄]·C₃H₇NO or cis-[Mn(H₂O)₂(DMF)₄]{Cu[12-MC_Cu(II)N(shi)-4]}·DMF, where MC is metallacrown, shi³⁻ is salicyl­hydroximate, and DMF is N,N-di­methyl­formamide, crystallizes in the monoclinic space group P2₁/n. Two crystallographically independent metallacrown anions are present in the structure, and both anions exhibit minor main mol­ecule disorder by an approximate (non-crystallographic) 180° rotation with occupancy ratios of 0.9010 (9) to 0.0990 (9) for one anion and 0.9497 (8) to 0.0503 (8) for the other. Each penta­copper(II) metallacrown contains four Cu^II ions in the MC ring and a Cu^II ion captured in the central cavity. Each Cu^II ion is four-coordinate with a square-planar geometry. The anionic {Cu[12-MC_Cu(II)N(shi)-4]}²⁻ is charged-balanced by the presence of a cis-[Mn(H₂O)₂(DMF)₄]²⁺ cation located in the lattice. In addition, the octa­hedral Mn^II counter-cation is hydrogen bonded to both MC anions via the coordinated water mol­ecules of the Mn^II ion. The water mol­ecules form hydrogen bonds with the phenolate and carbonyl oxygen atoms of the shi³⁻ ligands of the MCs.

22-Azametallacrown-8 complex with a triazole-bridged ligand: synthesis, structure and magnetic properties

Reaction of Mn(OAc)2·4H2O with the H2L ligand affords a new manganese 22-MC-8 azametallacrown [Mn8(μ3-O)2(μ3-OH)2(μ2-OH)2(L)6(OAc)2(OH2)4]·2DMF (H2L = 3-(2-oxyphenyl)-5-(pyrazin-2-yl)-1,2,4-triazole). The structural analysis of the complex reveals that the azaMC ring possesses -[Mn-O-Mn-N-N-Mn-N-N-Mn-N-N]- connectivity. The magnetic behavior of the complex shows the dominant antiferromagnetic interactions between the manganese ions with S = 4 and the frequency-dependent out-of-phase signal.

Bis(tetra-ethyl-ammonium) bis-(dimethyl-formamide)-tetra-kis-(μ-N,2-dioxido-benzene-1-carboximidato)penta-copper(II)

The title compound, (C₈H₂₀N)₂[Cu₅(C₇H₄NO₃)₄(C₃H₇NO)₂], abbreviated as (TEA)₂[Cu^II(12-MC_Cu^IIN(shi)-4](DMF)₂ [where TEA is tetra­ethyl­ammonium, shi³⁻ is salicyl­hydroximate (or N,2-dioxidobenzene-1-carboximidate) and DMF is N,N-dimethyl­formamide], contains five Cu^II ions. Four of the Cu^II ions are members of a metallacrown ring (MC), while the fifth Cu^II is bound in a central cavity. Two of the ring Cu^II ions are five-coordinate with distorted square-pyramidal geometry. The coordination sphere is composed of two shi³⁻ ligands and one DMF mol­ecule. The other two ring Cu^II ions and the central Cu^II ion are four-coordinate with square-planar geometry. The coordination spheres of these ions are only composed of shi³⁻ ligands. The charge of the [Cu^II(12-MC_Cu^IIN(shi)-4]²⁻ unit is balanced by two uncoordinated TEA⁺ countercations. The structure shows severe static disorder with the metallacrown, the tetra­ethyl­ammonium cations and the DMF solvent mol­ecule all disordered over each of two mutually exclusive sites, with occupancy rates for the major moieties of 0.6215 (6) for the metallacrown, 0.759 (3) for the tetra­ethyl­ammonium ion and 0.537 (6) for the DMF mol­ecules. The metallacrown unit is located on a crystallographic inversion center and disordered about a non-crystallographic twofold axis. The DMF mol­ecule and the tetra­ethyl­ammonium ion are disordered about a non-crystallographic twofold axis and pseudo-inversion center, respectively.

Thermodynamics of core metal replacement and self-assembly of Ca(2+) 15-metallacrown-5

The equilibria for core Ca(2+) replacement by Ln(3+) in copper(II) 15-MC-5 complexes have been investigated using a series of visible spectrophotometric titrations of calcium(II) metallacrowns ({Ca(II)[15-MC(Cu(II)(N)(L))-5]}(2+)) with Ln(3+) ions (H(2)L = pheha, (S)-alpha-phenylalaninehydroxamic acid, or trpha, (S)-alpha-tryptophanhydroxamic acid). These studies allowed the determination of the equilibrium constants for the reaction {Ca(II)[15-MC(Cu(II)(N)(L))-5]}(2+) + Ln(3+) --> {Ln(III)[15-MC(Cu(II)(N)(L))-5]}(3+) + Ca(2+) in methanol/water 9:1 (Ln(3+) = La(3+), Gd(3+), Dy(3+), Er(3+)) or 99:1 (Ln(3+) = La(3+), Nd(3+), Gd(3+), Dy(3+), Er(3+), Yb(3+)), respectively. The log K for these reactions decreases with increasing atomic number of the lanthanide(III), ranging from 6.1 to 3.91 in methanol/water 9:1. The same behavior is observed in methanol/water 99:1, although the constants are uniformly lower (log K = 4.09-2.52). A significant thermodynamic selectivity was observed for the later lanthanides (Gd(3+)-Yb(3+)) while a smaller selectivity is present throughout the beginning of the series (La(3+)-Gd(3+)). This observation has been interpreted on the basis of the size correspondence between the metal ions and the metallacrown cavity. The overall stability of the {Ca(II)[15-MC(Cu(II)(N)(L))-5]}(2+) in methanol/water 9:1 has been determined by pH-spectrophotometric titrations with HCl. The resulting log K values are 63.46(12) and 65.05(13) for pheha and trpha, respectively (Ca(2+) + 5Cu(2+) + 5HL(-) = {Ca(II)[15-MC(Cu(II)(N)(L))-5]}(2+) +5H(+)). The stability of both the La(3+) and Ca(2+) 15-metallacrown-5 complexes in the presence of high Na(+) concentrations has also been demonstrated by spectophotometric studies. Based upon these observations, the preference of the 15-MC-5 for Ca(2+) complexation compared to crown ethers has been quantitatively demonstrated for the first time.