Selectivity and Cooperativity in the Binding of Multiple Guests to a Pillar[5]arene-Crown Ether Fused Tricyclic Host.

A novel tricylic host molecule 1 that consists of two pillar[5]arene units and a crown ether ring was found to selectively bind two kinds of guest molecules with different shapes, sizes, and electronic constitutions, namely 1,4-dicyanobutane G1 and paraquat G2, with its two macrocyclic subunits, to form a four-component complex 2G1⊂1⊃G2. An (1)H NMR study of stepwise bindings of G1 and G2 to host 1 in CDCl3/DMSO-d6 revealed that the strength of the association between complex 2G1⊂1 and guest G2 was only one-fourth of that between free 1 and G2, demonstrating a negative heterotropic cooperativity of G1 in the binding of G2 to host 1.

[Theoretical studies on the structure, thermodynamics and spectral properties of rhodamine derivatives modified by amino of central ring].

The structures of three rhodamine derivatives were optimized by means of DFT/B3LYP method, and the data of the structural parameters and thermodynamic parameters of the excited state and ground state of the three rhodamine derivatives and their vibrational spectra and frontier molecular orbital energy level were obtained. On the basis of fully optimized structures of excited state and ground state, their gas absorption and emission spectra were studied by time-dependent density functional theory (TD-DFT), while the effects of their structural features on thermal stability, frontier molecular orbital and spectra properties were fully analyzed. The results indicate that the compound a has the lowest reverse movement degree of terminal amino among these molecules, and in contrast, the compound b was better conjugated and planar, the reverse movement degree of terminal amino improved, the gas absorption and emission spectra were red shifted, and it has the longest maximum emission wavelength and the lowest thermal stability among these molecules. The compound c was best conjugated and planar, its thermal stability and energy of HOMO were the highest, its HOMO-LUMO gap was most narrow, and it has the longest maximum absorption wavelength. It was found that the reverse movement degree of terminal amino of compound c improved compared to b, so its maximum emission wavelength was blue shifted.

Orientation-dependent structural and photocatalytic properties of LaCoO3 epitaxial nano-thin films.

LaCoO3 epitaxial films were grown on (100), (110) and (111) oriented LaAlO3 substrates by the polymer-assisted deposition method. Crystal structure measurement and cross-section observation indicate that all the LaCoO3 films are epitaxially grown in accordance with the orientation of LaAlO3 substrates, with biaxial compressive strain in the ab plane. Owing to the different strain directions of CoO6 octahedron, the mean Co-O bond length increases by different amounts in (100), (110) and (111) oriented films compared with that of bulk LaCoO3, and the (100) oriented LaCoO3 has the largest increase. Photocatalytic degradation of methyl orange indicates that the order of photocatalytic activity of the three oriented films is (100) > (111) > (110). Combined with analysis of electronic nature and band structure for LaCoO3 films, it is found that the change of the photocatalytic activity is closely related to the crystal field splitting energy of Co3+ and Co-O binding energy. The increase in the mean Co-O bond length will decrease the crystal field splitting energy of Co3+ and Co-O binding energy and further reduce the value of band gap energy, thus improving the photocatalytic activity. This may also provide a clue for expanding the visible-light-induced photocatalytic application of LaCoO3.