Search Results (7)

Hexaazamacrocyclic Schiff bases have been extensively combined with lanthanoid (Ln) ions to obtain complexes with a highly axial geometry. However, the use of flexible hexaazatetraamine macrocycles containing two pyridines and acyclic spacers is rather uncommon. Accordingly, we obtained [DyL(OAc)₂]OAc·7H₂O·EtOH and [DyL^Me2(Cl)₂]Cl·2H₂O, where L and L^Me2 are the 18-membered macrocycles 3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane and 3,10-dimethyl-3,6,10,13-tetraaza-1,8(2,6)-dipyridinacyclotetradecaphane, respectively, which contain ethylene and methylethylene spacers between their N₃ moieties. [DyL(OAc)₂]OAc·7H₂O·EtOH represents the first crystallographically characterized lanthanoid complex of L, while [DyL^Me2(Cl)₂]Cl·2H₂O contributes to increasing the scarce number of Ln^III compounds containing L^Me2. Furthermore, the crystal structure of L·12H₂O was solved, and it was compared with those of other related macrocycles previously published. Likewise, the crystal structures of the Dy^III complexes were compared with those of the lanthanoid and d-metal complexes of other 18-membered N₆ donor macrocycles. This comparison showed some effect of the spacers employed, as well as the influence of the size of the ancillary ligands and the metal ion. Additionally, the distinct folding behaviors of these macrocycles influenced their coordination geometries. Moreover, the luminescent properties of [DyL(OAc)₂]OAc·7H₂O·EtOH and [DyL^Me2(Cl)₂]Cl·2H₂O were also investigated, showing that both complexes are fluorescent, with the emission being sensitized by the ligands. Full article

The reaction of [GeF₄L₂], L = dmso (Me₂SO), dmf (Me₂NCHO), py (pyridine), pyNO (pyridine-N-oxide), OPPh₃, OPMe₃, with Me₃SiO₃SCF₃ (TMSOTf) and monodentate ligands, L, in a 1:1:1 molar ratio in anhydrous CH₂Cl₂ formed the monocations [GeF₃L₃][OTf]. These rare trifluoro-germanium (IV) cations were characterised by microanalysis, IR, ¹H, ¹⁹F{¹H} and, where appropriate, ³¹P{¹H} NMR spectroscopy. The ¹⁹F{¹H} NMR data show that in CH₃NO₂ solution the complexes exist as a mixture of mer and fac isomers, with the mer isomer invariably having the higher abundance. The X-ray structure of mer-[GeF₃(OPPh₃)₃][OTf] is also reported. The attempts to remove a second fluoride using a further equivalent of TMSOTf and L were mostly unsuccessful, although a mixture of [GeF₂(OAsPh₃)₄][OTf]₂ and [GeF₃(OAsPh₃)₃][OTf] was obtained using excess TMSOTf and OAsPh₃. The reaction of [GeF₄(MeCN)₂] with TMSOTf in CH₂Cl₂ solution, followed by the addition of 2,2′:6′,2”-terpyridine (terpy) formed mer-[GeF₃(terpy)][OTf], whilst a similar reaction with 1,4,7-trimethyl-1,4,7-triazacyclononane (Me₃-tacn) in MeCN solution produced fac-[GeF₃(Me₃-tacn)][OTf]. Dicationic complexes bearing the GeF₂²⁺ fragment were isolated using the tetra-aza macrocycles, 1,4,7,10-tetramethyl-1,4,7,10-tetra-azacyclododecane (Me₄-cyclen) and 1,4,8,11-tetramethyl-1,4,8,11-tetra-azacyclotetradecane (Me₄-cyclam), which reacted with [GeF₄(MeCN)₂] and two equivalents of TMSOTf to cleanly form the dicationic difluoride salts, cis-[GeF₂(Me₄-cyclen)][OTf]₂ and trans-[GeF₂(Me₄-cyclam)][OTf]₂. The ¹⁹F{¹H} NMR spectroscopy shows that in CH₃NO₂ solution there are four stereoisomers present for trans-[GeF₂(Me₄-cyclam)][OTf]₂, whereas the smaller ring-size of Me₄-cyclen accounts for the formation of only cis-[GeF₂(Me₄-cyclen)][OTf], and is confirmed crystallographically. New spectroscopic data are also reported for [GeF₄(L)₂] (L = dmso, dmf and pyNO). Density functional theory calculations were used to probe the effect on the bonding as fluoride ligands were sequentially removed from the germanium centre in the OPMe₃ complexes. Full article

Iodine-dense polyiodide phases are interesting materials for a number of potential uses, including batteries and solid-state conductors. The incorporation of transition metal cations is considered a promising way to enhance the stability, tune the properties, and influence the architecture of polyiodides. However, several interesting metals, including Cu(II), may suffer redox processes, which generally make them not compatible with the I₂/I⁻ redox couple. Herein L, a simple derivative of cyclen, is proposed as a Cu(II) ligand capable of protecting the +2 oxidation state of the metal even in the presence of polyiodides. With a step by step approach, we report the crystal structure of free L; then we present spectrophotometric verification of Cu(II) complex stability, stoichiometry, and formation kinetic in DMF solution, together with Cu(II) binding mode elucidation via XRD analysis of [Cu(L)Cl]ClO₄∙CH₃CN crystals; afterwards, the stability of the CuL complex in the presence of I⁻ is demonstrated in DMF solution, where the formation of a Cu:L:I⁻ ternary complex, rather than reduction to Cu(I), is observed; lastly, polyiodide crystals are prepared, affording the [Cu(L)I]₂I₃I₅ crystal structure. This layered structure is highly peculiar due to its chiral arrangement, opening further perspective for the crystal engineering of polyiodide phases. Full article

Tetraaza-macrocyclic pyridinophane L-Ts, decorated with a p-toluenesulfonyl (tosyl; Ts) group, appear to be a useful tool to provide evidence on how the interplay of various supramolecular forces can help stabilise exotic anionic species such as tribromide (Br₃⁻) anions. Indeed, crystals of (H₂L-Ts)(Br₃)_1.5(NO₃)_0.5 unexpectedly grew from an acidic (HNO₃) aqueous solution of L-Ts in the presence of Br⁻ anions. The crystal structure of this compound was determined by single crystal XRD analysis. Hydrogen bonds, salt-bridges, anion-π, π-π stacking, and van der Waals interactions contribute to stabilising the crystal lattice. The observation of two independent Br₃⁻ anions stuck over the π-electron densities of pyridine and tosyl ligand groups, one of them being sandwiched between two pyridine rings, corroborates the significance of anion-π interactions for N-containing heterocycles. We show herein the possibility of detecting anion-π contacts from fingerprint plots generated by Hirshfeld surface analysis, demonstrating the effective usage of this structural investigation technique to further dissect individual contributions of stabilising supramolecular forces. Full article

The compound [Ni(L)(isoph)₂][Ni(L)]·8H₂O (1; L = C-meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane; H₂-isoph = isophthalic acid) has been synthesized and structurally characterized. Complex 1 exhibits a geometrically symmetric core with a {4/6} coordination number set. The coordination environment around the Ni(1) ion is a distorted octahedron, while the geometry around the four-coordinate Ni(2) is depicted as square planar in 1D hydrogen-bonded infinite chain. The compound crystallizes in the triclinic system P-1 with a = 8.602(2), b = 10.684(7), c = 16.550(3) Å, a = 91.04(4), b = 94.09(2), g = 111.09(4)°, V = 1413.9(10) ų, Z = 1. The cyclic voltammogram of 1 undergoes one-electron wave corresponding to Ni^II/Ni^I process. The electronic spectra, electrochemical and TGA behavior of the complex are significantly affected by the nature of the hexamethyltetraaza macrocycle and the axial isoph²⁻ ligand. Full article

A novel family of tetraaza macrocyclic Cu(II) complexes [CuLX₂] (where L = N₄ donor macrocyclic ligands) and (X = Cl⁻, NO₃⁻) have been synthesized and characterized by elemental analysis, magnetic moments, IR, EPR, mass, electronic spectra and thermal studies. The magnetic moments and electronic spectral studies suggest square planar geometry for [Cu(DBACDT)]Cl₂ and [Cu(DBACDT)](NO₃)₂ complexes and distorted octahedral geometry to the rest of the ten complexes. The biological activity of all these complexes against gram-positive and gram-negative bacteria was compared with the activity of existing commercial antibacterial compounds like Linezolid and Cefaclor. Six complexes out of twelve were found to be most potent against both gram-positive as well as gram-negative bacteria due to the presence of thio group in the coordinated ligands. Full article

The reaction of [Ni(L)]Cl₂·2H₂O (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo [14,4,0^1.18,0^7.12]docosane) with trans-1,2-cyclopentanedicarboxylic acid (H₂-cpdc) yields a 1D hydrogen-bonded infinite chain with formula [Ni(L)(H-cpdc^-)₂] (1). This complex has been characterized by X-ray crystallography, spectroscopy and cyclic voltammetry. The crystal structure of 1 exhibits a distorted octahedral geometry about Ni atom with four nitrogen atoms of the macrocycle and two oxygen atoms of the H-cpdc^- ligand at the axial position. Compound 1 crystallizes in the monoclinic system P2₁/c with a = 8.7429(17), b = 10.488(2), c = 18.929(4) Å, β = 91.82(2), V = 1734.8(6) ų, Z = 2. Electronic spectrum of 1 reveals a high-spin octahedral environment. Cyclic voltammetry of 1 undergoes two waves of a one-electron transfer corresponding to Ni^II/Ni^III and Ni^II/Ni^I processes. Full article