Synthesis, X-Ray Structure, and Characterization of Catena-bis(benzoate)bis{N,N-bis(2-hydroxyethyl)glycinate}cadmium(II)

The reaction of N, N-bis(2-hydroxyethyl)glycine (bicine; bicH3) with Cd(O2CPh)2 · 2H2O in MeOH yielded the polymeric compound [Cd2(O2CPh)2(bicH2)2]n(1). The complex crystallizes in the tetragonal space group P41212. The lattice constants are a = b = 12.737(5) and c = 18.288(7) Å. The compound contains chains of repeating {Cd2(O2CPh)2(bicH2)2} units. One CdII atom is coordinated by two carboxylate oxygen, four hydroxyl oxygen, and two nitrogen atoms from two symmetry-related 2.21111 (Harris notation) bicH2− ligands. The other CdII atom is coordinated by six carboxylate oxygen atoms, four from two bicH2− ligands and two from the monodentate benzoate groups. Each bicinate(-1) ligand chelates the 8-coordinate, square antiprismatic CdII atom through one carboxylate oxygen, the nitrogen, and both hydroxyl oxygen atoms and bridges the second, six-coordinate trigonal prismatic CdII center through its carboxylate oxygen atoms. Compound 1 is the first structurally characterized cadmium(II) complex containing any anionic form of bicine as ligand. IR data of 1 are discussed in terms of the coordination modes of the ligands and the known structure

Smart Ligands for Efficient 3d-, 4d- and 5d-Metal Single-Molecule Magnets and Single-Ion Magnets

There has been a renaissance in the interdisciplinary field of Molecular Magnetism since ~2000, due to the discovery of the impressive properties and potential applications of d- and f-metal Single-Molecule Magnets (SMMs) and Single-Ion Magnets (SIMs) or Monometallic Single-Molecule Magnets. One of the consequences of this discovery has been an explosive growth in synthetic molecular inorganic and organometallic chemistry. In SMM and SIM chemistry, inorganic and organic ligands play a decisive role, sometimes equally important to that of the magnetic metal ion(s). In SMM chemistry, bridging ligands that propagate strong ferromagnetic exchange interactions between the metal ions resulting in large spin ground states, well isolated from excited states, are preferable; however, antiferromagnetic coupling can also lead to SMM behavior. In SIM chemistry, ligands that create a strong axial crystal field are highly desirable for metal ions with oblate electron density, e.g., TbIII and DyIII, whereas equatorial crystal fields lead to SMM behavior in complexes based on metal ions with prolate electron density, e.g., ErIII. In this review, we have attempted to highlight the use of few, efficient ligands in the chemistry of transition-metal SMMs and SIMs, through selected examples. The content of the review is purely chemical and it is assumed that the reader has a good knowledge of synthetic, structural and physical inorganic chemistry, as well as of the properties of SIMs and SMMs and the techniques of their study. The ligands that will be discussed are the azide ion, the cyanido group, the tris(trimethylsilyl)methanide, the cyclopentanienido group, soft (based on the Hard-Soft Acid-Base model) ligands, metallacrowns combined with click chemistry, deprotonated aliphatic diols, and the family of 2-pyridyl ketoximes, including some of its elaborate derivatives. The rationale behind the selection of the ligands will be emphasized

A Missing Nuclearity in the Co(III)/Ln(III)/2-Pyridyladoxime Chemistry: Tetranuclear Compounds Using the “Assisted Self-Assembly” Approach (Ln = Rare Earth Metals)

By employing the HSAB principle and the “assisted self-assembly” approach and using 2-pyridylaldoximate (pao−) as the primary ligand and pivalate (piv−) as the ancillary co-ligand, tetranuclear [CoIII2LnIII2(NO3)4(pao)4(piv)4] complex polynuclear compounds were isolated (Ln = Dy, Gd, Tb, Pr, Y). The structure of the Dy(III) complex was determined via single-crystal X-ray crystallography, revealing a metal topology of two {CoIIIDyIII2} triangles that shared a common DyIII…DyIII edge. Microanalytical, PXRD (for the two first members)d and spectroscopic (IR, EDX) data for all complexes provided strong evidence that the complexes were isostructural. The nuclearity and metal topology of the crystallographically characterized [CoIII2LnIII2(NO3)4(pao)4(piv)4] are new in the previously investigated CoIII/LnIII/pao− chemistry emphasizing utility of the “assisted self-assembly” approach

Synthesis, structural study and topological analysis of Zn/Aib and Aib-based small peptide complexes (H-Aib-OH = alpha-aminoisobutyric acid)

The systematic investigation of the coordination chemistry of alpha-aminoisobutyric acid (H-Aib-OH) and Aib-based small peptides is continued. The solid complexes [Zn-3(H-Aib-O)(6)]center dot MeCOOH center dot H2O (1 center dot MeCOOH center dot H2O), ([Zn(H-2-Aib-L-Ala-O)(2)]center dot H2O](n) (2 center dot H2O) and [Zn(H-2-Aib-Aib-Aib-O)(4)](ClO4)(2)center dot 5.8H(2)O (3 center dot 5.8H(2)O) have been isolated and characterized by single-crystal X-ray crystallography. In the structure of complex 1 center dot MeCOOH center dot H2O, three Zn-II ions and six H-Aib-O- ligands have assembled to form a trinuclear cluster. All three Zn-II centers are in a very distorted trigonal bipyramidal coordination. The trinuclear units assemble through a network of hydrogen bonds to form a 2D framework with a (3.6.3.6) topology, while the lattice acetic acid and water molecule connect the layers to create a 3D framework with a fcu topology. Complex 2 center dot H2O is a two-dimensional coordination polymer. The deprotonated dipeptide behaves as a eta(1):eta(1):eta(1):mu(2) ligand binding one Zn-II atom through its amino nitrogen and peptide oxygen, and an adjacent Zn-II atom through one of its carboxylate oxygen. In the crystal lattice, the layers are connected in the third direction through hydrogen bonds and the resulting framework conforms to a tfa net. Complex 3 center dot 5.8H(2)O consists of mononuclear [Zn(H-2-Aib-Aib-Aib-O)(4)](2+) cations, CLO4- and lattice water molecules. The tripeptide ligands are in their zwitterionic form and coordinate through one of the carboxylate oxygen atom to the metal ion, while they are participating in a network of intra- and intermolecular hydrogen bonds forming a 3D framework that adopts the bcu network. (c) 2009 Elsevier Ltd. All rights reserved

Synthesis, Crystal Structures, and DNA Binding Properties of Zinc(II) Complexes with 3-Pyridine Aldoxime

The employment of 3-pyridine aldoxime, (3-py)CHNOH, in ZnII chemistry has afforded two novel compounds: [Zn(acac)2{(3-py)CHNOH}]⋅H2O (1⋅H2O) [where acac- is the pentane-2,4-dionato(-1) ion] and [Zn2(O2CMe)4{(3-py)CHNOH}2] (2). Complex 1⋅H2O crystallizes in the monoclinic space group P21/n. The ZnII ion is five-coordinated, surrounded by four oxygen atoms of two acac- moieties and by the pyridyl nitrogen atom of the (3-py)CHNOH ligand. Molecules of 1 interact with the water lattice molecules forming a 2D hydrogen-bonding network. Complex 2 crystallizes in the triclinic P-1 space group and displays a dinuclear paddle-wheel structure. Each ZnII exhibits a perfect square pyramidal geometry, with four carboxylate oxygen atoms at the basal plane and the pyridyl nitrogen of one monodentate (3-py)CHNOH ligand at the apex. DNA mobility shift assays were performed for the determination of the in vitro effect of both complexes on the integrity and the electrophoretic mobility of pDNA

Diorganotin(IV) complexes of dipeptides containing the alpha-aminoisobutyryl residue (Aib): Preparation, structural characterization, antibacterial and antiproliferative activities of [(n-Bu)(2)Sn(H-L-1)] (LH = H-Aib-L-Leu-OH, H-Aib-L-Ala-OH)

Two new organotin(IV) complexes with dianionic dipeptides containing the alpha-aminoisobutyryl residue (Aib) as ligands are described. The solid complexes [(n-Bu)(2)Sn(H-1LA)]center dot 2MeOH (1.2MeOH) (LAH = H-Aib-L-Leu-OH) and [(n-Bu)(2)Sn(H-L-1(B))]. MeOH (2 center dot MeOH) (LBH = H-Aib-L-Ala-OH) have been isolated and characterized by single-crystal X-ray crystallography and spectroscopic techniques (H-1L2- is the dianionic form of the corresponding dipeptide). Complexes 1.2MeOH and 2 center dot MeOH are monomeric with similar molecular structures. The doubly deprotonated dipeptide behaves as a N(amino), N(peptide), O(carboxylate) ligand and binds to the Sn-IV atom. The five-coordinate metal ion has a distorted trigonal bipyramidal geometry. A different network of intermolecular hydrogen bonds in each compound results in very dissimilar supramolecular features. The IR, far-IR, Raman and Sn-119 NMR data are discussed in terms of the nature of bonding and known structures. The antibacterial and antiproliferative activities as well as the effect of the new compounds on pDNA were examined. Complexes I and 2 are active against the gram-positive bacteria Bacillus subtilis and Bacillus cereus. The IC50 values reveal that the two compounds express promising cytotoxic activity in vitro against a series of cell lines. (c) 2008 Elsevier Inc. All rights reserved

One-dimensional cadmium(II)/bicinate(−1) complexes : the role of the alkali metal ion used in the reaction medium

Summarization: The initial employment of N,N-bis(2-hydroxyethyl)glycine (bicine; bicH3) in CdCl2 chemistry is reported, and the syntheses, IR spectra and crystal structures of the 1D coordination polymers [CdCl(bicH2)]n·nH2O (1·H2O) and [CdNaCl2(bicH2)(MeOH)]n (2) are described. The identity of the products depends on the solvent, the reaction temperature and the alkali metal ion of the base used. The structure of 1·H2O consists of zig-zag chains. The 7-coordinate CdII atoms are bridged by η1:η1:μ2 carboxylate groups of the 2.21111 (Harris notation) bicH2− ligand. The coordination geometry of the metal center can be either described as a very distorted pentagonal bipyramidal or as a distorted capped octahedral. In the structure of 2 the CdII atoms form an almost linear chain with neighboring NaI atoms on opposite sites of the chain. Every pair of CdII atoms is linked by two chloro ligands and the two oxygen atoms of the bicinate carboxylate group. The CdII and NaI atoms are bridged by one μ2 carboxylate bicinate oxygen and one μ3 chloro ligand. The 3.21,211121212 coordination mode of bicH2− is unprecedented. The CdCl4(Ocarboxylate)2 and Na(Ohydroxyl)2(Ocarboxylate)(OMeOH)NCl coordination spheres are octahedral and trigonal prismatic, respectively. IR data of the complexes are discussed in terms of the coordination modes of bicH2− and the known structures.Presented on: Polyhedro