A hemicryptophane cage bearing amine and amide functions in its three linkers was synthesized in five steps. The X-ray molecular structure of the cage shows a triple-stranded helical arrangement of the linkers stabilized by intramolecular hydrogen bonds between amide and amine groups. The chirality of the cyclotriveratrylene unit controls the propeller arrangement of the three aromatic rings in the opposite part of the cage. H NMR studies suggest that this structure is retained in solution.
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http://dx.doi.org/10.3762/bjoc.14.162 | DOI Listing |
Dalton Trans
November 2024
Department of Inorganic and Analytical Chemistry, University of Geneva, 30 quai E. Ansermet, CH-1211 Geneva 4, Switzerland.
Due to the primogenic effect, the valence shells of divalent iron Fe(II) ([Ar]3d) and trivalent lanthanides Ln(III) ([Xe]4f) are compact enough to induce spin-state equilibrium for the 3d-block metal and atom-like luminescence for the 4f-block partner in Fe(II)-Ln(III) dyads. In the specific case of homoleptic pseudo-octahedral [Fe(II)N] units, programming spin crossover (SCO) around room temperature at normal pressure requires the design of unsymmetrical didentate five-membered ring chelating NN' ligands, in which a five-membered (benz)imidazole heterocycle (N) is connected to a six-membered pyrimidine heterocycle (N'). Benefiting from the influence, the facial isomer -[Fe(II)(NN')] is suitable for inducing SCO properties at room temperature in solution.
View Article and Find Full Text PDFChemistry
November 2024
Faculty of Engineering, Hokkaido University, Kita 13 Nishi 8 Kita-ku, Sapporo, Hokkaido, 060-8628, Japan.
Triple-stranded helical lanthanide MOFs with CO adsorption properties were investigated. Lanthanide MOFs ([EuTb(hfa)(dpa)]) are composed of lanthanide luminophores (Eu(III) and/or Tb(III) ions), fluorinated antenna ligands (hfa: hexafluoroacetylacetonate), and polyamide-type linker ligands (dpa: 4-(diphenylphosphoryl)-N-(4-(diphenylphosphoryl)phenyl)benzamide). The cylindrical structure was characterized by single-crystal X-ray analysis, thermogravimetric analysis, and gas adsorption measurements.
View Article and Find Full Text PDFHighly diastereoselective self-assembly reactions give both enantiomers (Λ and Δ) of anti-parallel triple-stranded bimetallic Co(ii) and Co(iii) cationic helices, without the need for resolution; the first such reaction for Co. The complexes are water soluble and stable, even in the case of Co(ii). Studies in a range of cancer and healthy cell lines indicate high activity and selectivity, and substantial differences between enantiomers.
View Article and Find Full Text PDFJ Am Chem Soc
July 2024
Department of Inorganic and Analytical Chemistry, University of Geneva, 30 Quai E. Ansermet, CH-1211 Geneva 4, Switzerland.
Compared with the ripple of visible Eu-based emission intensity induced by appended [FeN] spin crossover (SCO) units, as detected in the triple-stranded [EuFe()] helicate, the lanthanide-based luminescent detection of Fe spin-state equilibria could be improved significantly if the luminophore emission is shifted toward the near-infrared (NIR) domain. Replacing Eu with Nd in [NdFe()] (i) maintains the favorable SCO properties in acetonitrile [critical temperature = 322(2) K], (ii) saturates nonradiative vibrational relaxation processes in the 233-333 K range, and (iii) boosts the crucial intramolecular Nd → Fe energy transfer rate processes, which are sensitive to the spin state of the Fe metallic center. Consequently, the steady-state NIR Nd(F → I) emission of the luminophore is amplified and linearly correlated with the low-spin-[FeN] and high-spin-[FeN] mole fractions controlled by the SCO equilibrium.
View Article and Find Full Text PDFChem Sci
June 2024
Departament de Química Inorgànica i Orgànica, Secció Química Inorgànica, Universitat de Barcelona Barcelona Spain
Ditopic bis-pyrazolylpyridine ligands usually react with divalent metal ions (M) to produce dinuclear triple-stranded helicates [ML] or, π⋯π interactions, dimers of monoatomic complexes ([ML]). The introduction of an additional benzene ring at each end of ligand L increases the number of aromatic contacts within the supramolecular aggregate by 40%, driving the self-recognition process in an irreversible manner. Consequently, the mixing of new bis-pyrazolylquinoline L2 with FeX salts leads to crystallization of the tripartite high-spin assemblies (X@[Fe(L2)]) (X = Cl, Br or I).
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