Unique luminescence of non-conventional luminophores derived from space conjugation (SC) has recently attracted extensive interest. However, it is difficult to achieve highly efficient emission (especially white light one) from SC,...
A methylation reagent for compounds bearing NÀ H, OÀ H, and SÀ H functionalities was developed. Methyl trifluoroacetate (MTFA) was commonly considered as trifluoroacetylating reagent or trifluoromethylating reagent. In this work, we report the methylation behavior of MTFA under mild conditions with good functional group tolerance, allowing the transformation of a wide range of substrates, including N,H-heteroaromatic compounds, phenolic compounds, carboxylic acids, thiophenols, secondary amides and imides, in high yields. This method was preliminarily applied to the chemoselective methylation of bifunctionalized secondary amide.
Study of artificial tubular assemblies as a useful host scaffold for size-selective recognition and release of guest molecules is an important subject in host-guest chemistry. We describe well-defined self-assembled nanotubes (NT6mer) formed from π-conjugated m-phenylene-pyrimidinylene alternated macrocycle 16mer that exhibit size-selective recognition toward a specific aromatic acid. In a series of guest molecules, a size-matched trimesic acid (G3) gives inclusion complexes (NT6mer⊃G3) in dichloromethane resulting in an enhanced and red-shifted fluorescence. (1)H nuclear magnetic resonance (NMR) titration experiments indicated that the complex was formed in a 1:1 molar ratio. Density functional theory (DFT) calculations and the binding constant value (K = 1.499 × 10(5) M(-1)) of NT6mer with G3 suggested that the complex involved triple hydrogen-bonding interactions. The encapsulated guest G3 molecules can be readily released from the tubular channel through the dissociation of hydrogen bonding by the addition of a polar solvent such as dimethylsulfoxide (DMSO). In contrast, 16mer could not form self-assembled nanotubes in CHCl3 or tetrahydrofuran (THF) solution, leading to weak or no size-selective recognizability, respectively.
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