3-Trifluoromethyl-pyrazoles containing strong fluorophore groups: triphenylamine (TPAPz) and carbazole (CarbPz), and their trinuclear silver(I) complexes are found to be emissive in solution and the solid state, giving the first example of silver pyrazolate adducts emissive in solution at room temperature. The electronic coupling was observed for pyrazole with a structurally flexible triphenylamine substituent, determining the intraligand charge-transfer (ILCT) nature of the excited states. The association–dissociation of the trinuclear complex core with the heavy atom effect leads to the intense phosphorescence of the triphenylamine-containing complex. The structural rigidity of the N-ethyl carbazole substituent allows only twisting via the bond to the pyrazolate core leading to typical carbazole-centered (LC) fluorescence in solution. In the solid-state, aggregation plays the primary role in emission properties. The observed behavior is in good agreement with the theoretical calculations.
Photoinitiated solid-state reactions are known to affect the physical properties of coordination polymers, such as fluorescence and sorption behaviour, and also afford extraordinary architectures (e.g. three-periodic structures with polyorganic ligands). However, the construction of novel photo-sensitive coordination polymers requires an understanding of the factors which govern the mutual disposition of reactive fragments. A series of zinc(II) malonate complexes with 1,2-bis(pyridin-4-yl)ethylene and its photo-insensitive analogues has been synthesized for the purpose of systematic analysis of their underlying nets and mutual disposition of N-donor ligands. The application of a big data-set analysis for the prediction of a variety of possible complex compositions, coordination environments and networks for a four-component system has been demonstrated for the first time. Seven of the nine compounds possess one of the highly probable topologies for their underlying nets; in addition, two novel closely related four-coordinated networks were obtained. Complexes containing 1,2-bis(pyridin-4-yl)ethylene and 1,2-bis(pyridin-4-yl)ethane form isoreticular compounds more readily than those with 4,4′-bipyridine and 1,2-bis(pyridin-4-yl)ethylene. The effects of the precursor, either zinc(II) nitrate or zinc(II) acetate, on the composition and dimensionality of the resulting architecture are discussed. For three of the four novel complexes containing 1,2-bis(pyridin-4-yl)ethylene, the single-crystal-to-single-crystal [2 + 2] cycloaddition reactions were carried out. UV irradiation of these crystals afforded either the 0D→1D or the 3D→3D transformations, with and without network changes. One of the two 3D→3D transformations was accompanied by solvent (H2O) cleavage.
13 October 2021 in Organic & Biomolecular Chemistry
An efficient access to new CF3-containing 2-quinolones has been developed via Rh(iii)-catalyzed C–H activation/Lossen rearrangement/annulation cascade of N-pivaloyloxy-arylamides with internal alkynes bearing α-CF3-α-amino acid moiety on triple bond.
We report that three-component systems comprising styryl dyes (1 or 2) and two hosts (hydroxypropyl-β-cyclodextrin (HP-β-CD) and cucurbit[7]uril (CB[7])) undergo photoinduced transformation and translocation of the styryl guest from the cavity of HP-β-CD to CB[7]. We find that the protonation of guest trans-1 or the addition of Ba2+ as competitor for CB[7] triggers dissociation of the container–guest complexes.
1 May 2011 in Protection of Metals and Physical Chemistry of Surfaces
The possibility of describing the isotherms of adsorption on microporous adsorbents at supercritical temperatures using the Dubinin-Radushkevich, Dubinin-Astakhov, and Tolmachev-Aranovich equations, in which the adsorbtive saturated vapor pressures that serve as the standard pressures below critical temperatures are substituted for the standard pressures (Ps* ) found by the linear extrapolation of the dependences of adsorbtive saturated vapor pressure on the inverse temperature to the supercritical region, is shown. The possibility of linear extrapolation is substantiated by the data of a numerical experiment.