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Equipping metallo-supramolecular macrocycles with functional groups: Assemblies of pyridine-substituted urea ligands

2012

A series of di-(m-pyridyl)-urea ligands were prepared and characterized with respect to their conformations by NOESY experiments and crystallography. Methyl substitution in different positions of the pyridine rings provides control over the position of the pyridine N atoms relative to the urea carbonyl group. The ligands were used to self-assemble metallo-supramolecular M(2)L(2) and M(3)L(3) macrocycles which are generated in a finely balanced equilibrium in DMSO and DMF according to DOSY NMR experiments and ESI FTICR mass spectrometry. Again, crystallography was used to characterize the assemblies. Methyl substitution in positions next to the pyridine nitrogen prevents coordination, while …

2017

The title compound, C12H9BrN2O3, was prepared in two steps from 2-chloro-3-nitropyridine. The nitrobiaryl unit is twisted, with dihedral angles of 35.4 (5)° between the nitro substituent and the pyridine ring to which it is bound, and 51.0 (5)° between the nitro group and the benzene ring. In the crystal, the molecules are connectedviaC—H...O hydrogen bonds, forming strands along theb-axis direction.

Linking PO43− and HAsO42− anions with a dinuclear [ZnII2] complex: Formation and stabilization of novel decanuclear metallomacrocyclic [ZnII10] and t…

2017

The linkage of PO43- and HAsO42--anions with a newly synthesized five-coordinate dinuclear zinc complex, Zn-2(cpdp)(H2O)(2)]Cl (1) H(3)cpdp =N,N'-bis2-carboxybenzomethyl]-N,N'-bis2-pyridylmethyl]-1,3diamino propan-2-ol], has been explored. In methanol-water, the reaction of 1 with Na2HPO4 center dot 2H(2)O and Na2HAsO4 center dot 7H(2)O/NaBr separately, at ambient temperature, yielded the novel phosphate-bridged decanuclear zinc cluster, (H3O)(4)Zn-10(cPdP)(4)(mu(5)-PO4)(2)(H2O)(6)](6 center dot Cl)center dot 53H(2)O (2) and hydrogen arsenate bridged tetranuclear zinc cluster, Na-2Zn-4(cpdp)(2)(mu(4)-HAsO4)]ClBr center dot 13H(2)O (3), respectively. Analysis of the single crystal X-ray stru…

Regio-, Diastereo-, and Enantioselective Organocatalytic Addition of 4-Substituted Pyrazolones to Isatin-Derived Nitroalkenes

2019

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Enhanced Interplay between Host–Guest and Spin-Crossover Properties through the Introduction of an N Heteroatom in 2D Hofmann Clathrates

2021

Controlled modulation of the spin-crossover (SCO) behavior through the sorption-desorption of invited molecules is an extensively exploited topic because of its potential applications in molecular sensing. For this purpose, understanding the mechanisms by which the spin-switching properties are altered by guest molecules is of paramount importance. Here, we show an experimental approach revealing a direct probe of how the interplay between SCO and host-guest chemistry is noticeably activated by chemically tuning the host structure. Thus, the axial ligand 4-phenylpyridine (4-PhPy) in the 2D Hofmann clathrates {Fe(4-PhPy)2[M(CN)4]} (PhPyM; M = Pt, Pd) is replaced by 2,4-bipyridine (2,4-Bipy),…

Recent studies on RR′S·C2B9H11 charge-compensated ligands

2002

Abstract In this paper we report the synthesis of three new carborane derivatives of the series 7,8-R,R′-10-L-7,8-C2B9H9 (R=R′=H, L=SEtPh; R=CH3, R′=H, L=SMe2 and L=SEt2) along with the enhanced characterization of formerly described compounds 7,8-R,R′-10-L-7,8-C2B9H9 (R=R′=H, L=SMe2 (1), L=SEt2 (2) and L=S(CH2)4 (3)). They have been fully characterised using 1H-, 11B- and 13C-NMR spectroscopy. Their bridging proton resonances have been located for the first time. Individual sulfonium substituent contributions have been calculated that have permitted to establish a rule to predict its position in the 1H-NMR spectrum. The crystal structures of 1 and 3 have been resolved for the first time. T…

Preparative-Scale Synthesis of Vedejs Chiral DMAP Catalysts

2018

A scalable synthesis of chiral Vedejs-type DMAP catalysts is reported. The key step of the synthesis is amination of the enantiomerically pure 4-chloropyridine derivative using well-defined ZnCl2(amine)2 complexes. A series of Zn(II)–amine complexes have been synthesized to explore the scope of the ZnCl2-mediated amination of 4-halopyridines. Mechanistic studies support a Zn(II)-facilitated nucleophilic aromatic substitution as a plausible mechanism for the chlorine-to-amine exchange.

Influence of Substituent and Benzoannulation on Photophysical Properties of 1-Benzoylmethyleneisoquinoline Difluoroborates

2015

A series of 1-benzoylmethyleneisoquinoline difluoroborates were synthesized, and their photophysical properties were determined. The effect of the substituent and benzoannulation on their properties was investigated to make a comparison with recently published results focused on related quinolines. The photophysical properties of isoquinoline derivatives differ from those of quinolines, and the most pronounced differences are found for the fluorescence quantum yields. Both experimental and theoretical approaches were used to explain the observed photophysical properties.

Cobaltocenium substituents as electron acceptors in photosynthetic model dyads

2017

Abstract Cobaltocenium carboxylic acid hexafluorophosphate has been attached to a zinc(II) meso-tetraphenyl porphyrin chromophore via an amide linkage. Optical and electrochemical studies reveal that the metallocene and the porphyrin interact only negligibly in the ground state of the dyad. Photoinduced charge-shift from the zinc porphyrin to the cobaltocenium substituent to give the zinc porphyrin radical cation and the cobaltocene occurs upon exciting the porphyrin with light. Steady state emission, time-resolved fluorescence and transient absorption pump–probe spectroscopy in addition to density functional theory calculations suggest that the charge shift to the cobaltocenium substituent…

First titanium-catalyzed 1,4-hydrophosphination of 1,3-dienes

2010

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