Vielzähnige nichtcyclische Neutralliganden und ihre Komplexierung

Vögtle, Fritz; Weber, Edwin

doi:10.1002/ange.19790911007

Cited by 113 publications

(11 citation statements)

References 236 publications

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“…Solid-state [43,44] Usually only the 139 La central transi- [33] square antiprism OB, OU Ln acac derivatives used as NMR shift reagents; [6][7][8] analogous Nd complex [75] 2 [La(bipyO) 4 [35] tricapped trigonal prism OU, OB numerous similar compounds [35] 4 [La(mal) 2 [36] monocapped square antiprism OB, OU polymeric carboxylate; similar Nd, [77,78] Eu, [79] and Gd [80] [40] monocapped pentagonal antiprism OM, OB crown-ether ligand used to complex metals; [90] analogous Ce, [91] Eu, [92] and Pr [93] [42] bicapped pentagonal prism NM, OB numerous similar complexes [95][96][97][98] [a] acac = acetylacetonate, bipyO = 2,2'-bipyridine-1,1'-dioxide, phen = 1,10-phenanthroline, mal = malonic acid, glut = glutamic acid, TEG = tetraethyleneglycol, N-macro = di(ethane-1,2-diyl)bis(pyridine-2,6-diacetimine).…”

Section: Resultsmentioning

confidence: 99%

An Investigation of Lanthanum Coordination Compounds by Using Solid‐State ¹³⁹La NMR Spectroscopy and Relativistic Density Functional Theory

Willans

Feindel

Ooms

et al. 2005

Chemistry A European J

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Lanthanum-139 NMR spectra of stationary samples of several solid La(III) coordination compounds have been obtained at applied magnetic fields of 11.75 and 17.60 T. The breadth and shape of the 139La NMR spectra of the central transition are dominated by the interaction between the 139La nuclear quadrupole moment and the electric field gradient (EFG) at that nucleus; however, the influence of chemical-shift anisotropy on the NMR spectra is non-negligible for the majority of the compounds investigated. Analysis of the experimental NMR spectra reveals that the 139La quadrupolar coupling constants (C(Q)) range from 10.0 to 35.6 MHz, the spans of the chemical-shift tensor (Omega) range from 50 to 260 ppm, and the isotropic chemical shifts (delta(iso)) range from -80 to 178 ppm. In general, there is a correlation between the magnitudes of C(Q) and Omega, and delta(iso) is shown to depend on the La coordination number. Magnetic-shielding tensors, calculated by using relativistic zeroth-order regular approximation density functional theory (ZORA-DFT) and incorporating scalar only or scalar plus spin-orbit relativistic effects, qualitatively reproduce the experimental chemical-shift tensors. In general, the inclusion of spin-orbit coupling yields results that are in better agreement with those from the experiment. The magnetic-shielding calculations and experimentally determined Euler angles can be used to predict the orientation of the chemical-shift and EFG tensors in the molecular frame. This study demonstrates that solid-state 139La NMR spectroscopy is a useful characterization method and can provide insight into the molecular structure of lanthanum coordination compounds.

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Section: Resultsmentioning

confidence: 99%

An Investigation of Lanthanum Coordination Compounds by Using Solid‐State ¹³⁹La NMR Spectroscopy and Relativistic Density Functional Theory

Willans

Feindel

Ooms

et al. 2005

Chemistry A European J

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“…In order to favor dimeric association as in the [Cu2(pQP)2]2+ complex (8), the bridge should be short enough to hinder tetrahedral binding of an ion by more than one bipyridine unit of the same ligand molecule and flexible enough to allow strain-free coordination in dimeric fashion. The simple -CH20CH2-group appeared to fulfill these requirements; note also that oligoethyleneglycol ligands may wrap around bound metal ions in a helical fashion (11,12).…”

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confidence: 99%

Spontaneous assembly of double-stranded helicates from oligobipyridine ligands and copper(I) cations: structure of an inorganic double helix.

Lehn¹,

Rigault²,

Siegel³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

840

539

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Two oligobipyridine ligands containing two and three 2,2'-bipyridine subunits separated by 2-oxapropylene bridges have been synthesized and some of their complexation properties with metal ions have been investigated. In particular, with copper(I) they form, respectively, a dinuclear and a trinuclear complex containing two ligand molecules and two or three Cu(I) ions. In view of the pseudotetrahedral coordination geometry of Cu(I)-bis(bipyridine) sites and of NMR data indicating that the present complexes are chiral, one may assign to these dinuclear and trinuclear species a double-helical structure in which two molecular strands are wrapped around two or three Cu(I) ions, which hold them together. These complexes may thus be termed "double-stranded helicates." Determination of the crystal structure of the trinuclear species has confirmed that it is indeed an inorganic double helix, possessing characteristic features (helical parameters, stacking of bipyridine bases) reminiscent of the DNA double helix. This spontaneous formation of an organized structure by oligobipyridine ligands and suitable metal ions opens ways to the design and study of self-assembling systems presenting cooperativity and regulation features. Various further developments may be envisaged along organic, inorganic, and biochemical lines.Molecular helicity is a fascinating property displayed by chemical and biological macromolecular structures such as the a-helix of polypeptides and the helical conformation of polymers (1,2). Particularly well known is the double helix present in nucleic acids (3), whose structure, formation, and dissociation have been the subject of very extensive studies. Helicity has been analyzed for twisted chains of atoms (4) and its basic geometrical features are found in several types of small molecules (5, 6).We report here results on a class of organic ligands of poly(2,2'-bipyridine)t nature, which, by binding metal ions of specific coordination geometry, undergo spontaneous organization into a helical double-stranded, polymetallic complex, in effect an inorganic double helix, reminiscent of the double-helical structure of nucleic acids (3, 7). Design Principle. Previous work on the dinuclear Cu(I) complex [Cu2(pQP)2](CI04)2 of a special quaterpyridine ligand, pQP, has shown that in this dimeric species, two pQP molecules bind two Cu(I) ions in a distorted tetrahedral coordination geometry, using a bipyridine subunit from each quaterpyridine chain (8); the two pQP molecules possess a twisted, chiral conformation and are wrapped around the two Cu(I) ions (Fig. 1). Related structural features may be found in some other dinuclear metal complexes (9, 10). Suitable modification of the pQP ligand and extension of its basic features might lead to a general class of ligands capable of forming double-helical complexes. Rather than simply using polypyridine chains, it appeared desirable to preserve the basic bipyridine units in the ligand structure and to link several such groups by a bridge that would isolate the co...

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“…However, their binding efficiency is generally lower than the maternal crown ethers due to their increased structural flexibility. [3] To overcome this drawback, the strategy of preorganization has been developed, which allows for the generation of a variety of rigid "tweezer" or "cleft" receptors for efficient guest binding. [4] The α-helix is the most common secondary structure of natural peptides and proteins and is stabilized mainly by intramolecular hydrogen bonds and hydrophobic packing.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen‐Bonding‐Driven Aromatic Foldamers: Their Structural and Functional Evolution

Zhang

Wang

2014

The Chemical Record

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This Personal Account summarizes the development of the design of hydrogen-bonding-driven aromatic foldamers and their applications in supramolecular chemistry. This account begins with a short, non-exhaustive description of the background in the study of hydrogen-bonded aromatic foldamers. The construction of foldamers from discrete aromatic residues, including amide, urea, hydrazide and 1,2,3-triazole units, is then described. In the following parts, the applications of such compact aromatic oligomers in supramolecular chemistry, including the development of acyclic receptors, the construction of hybrid helical sequences through intramolecular stacking, the promotion of the formation of covalently and noncovalently bonded macrocycles, the tuning of the mechanical properties of copolymers, and the regulation of the shuttling behavior of [2]rotaxanes and the controlled release of dye from reverse vesicles formed from them, are described. In the final part, the binding-induced folding of conformationally flexible aromatic amide oligomers and their self-binding are described.

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Vielzähnige nichtcyclische Neutralliganden und ihre Komplexierung

Cited by 113 publications

References 236 publications

An Investigation of Lanthanum Coordination Compounds by Using Solid‐State ¹³⁹La NMR Spectroscopy and Relativistic Density Functional Theory

An Investigation of Lanthanum Coordination Compounds by Using Solid‐State ¹³⁹La NMR Spectroscopy and Relativistic Density Functional Theory

Spontaneous assembly of double-stranded helicates from oligobipyridine ligands and copper(I) cations: structure of an inorganic double helix.

Hydrogen‐Bonding‐Driven Aromatic Foldamers: Their Structural and Functional Evolution

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Vielzähnige nichtcyclische Neutralliganden und ihre Komplexierung

Cited by 113 publications

References 236 publications

An Investigation of Lanthanum Coordination Compounds by Using Solid‐State 139La NMR Spectroscopy and Relativistic Density Functional Theory

An Investigation of Lanthanum Coordination Compounds by Using Solid‐State 139La NMR Spectroscopy and Relativistic Density Functional Theory

Spontaneous assembly of double-stranded helicates from oligobipyridine ligands and copper(I) cations: structure of an inorganic double helix.

Hydrogen‐Bonding‐Driven Aromatic Foldamers: Their Structural and Functional Evolution

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An Investigation of Lanthanum Coordination Compounds by Using Solid‐State ¹³⁹La NMR Spectroscopy and Relativistic Density Functional Theory

An Investigation of Lanthanum Coordination Compounds by Using Solid‐State ¹³⁹La NMR Spectroscopy and Relativistic Density Functional Theory