Self-recognition behavior of novel frameworks containing both urea and carboxylate anion motifs

Tetraphenylene-Coated Near-Infrared Benzoselenodiazole Dye: AIE Behavior, Mechanochromism, and Bioimaging

A D-π-A-π-D type of tetraphenylene-coating benzoselenodiazole fluorescence dye with near-infrared emission has been designed and constructed. This dye shows an obvious aggregation-induced-emission behavior. In the solid state, it exhibits a reversible mechanochromism with the changes of near-infrared emission. Furthermore, this dye can be used to track the lysosomes of living cells and images in vivo.

Crystal structure of a host-guest complex of the tris-urea receptor, 3-(4-nitro-phen-yl)-1,1-bis-{2-[3-(4-nitro-phen-yl)ureido]eth-yl}urea, that encapsulates hydrogen-bonded chains of di-hydrogen phosphate anions with separate tetra-n-butyl-ammonium counter-ions

The title compound, C25H25N9O9·C16H36N+·H2PO4 - (I) or (C25H25N9O9)·(n-Bu4N+)·(H2PO4 -) (systematic name: 3-(4-nitro-phen-yl)-1,1-bis-{2-[3-(4-nitro-phen-yl)ureido]eth-yl}urea tetra-butyl-ammonium di-hydrogen phosphate), comprises a tris-urea receptor (R), a di-hydrogen phosphate anion and a tetra-n-butyl-ammonium cation. It crystallizes with two independent formula units in the asymmetric unit. The conformations of the two tris-urea receptors are stabilized by N-H⋯O and C-H⋯O intra-molecular hydrogen bonds. Each di-hydrogen phosphate anion has two O-H⋯O inter-molecular hydrogen-bonding inter-actions with the other di-hydrogen phosphate anion. Inversion-related di-anion units are linked by further O-H⋯O hydrogen bonds, forming a chain propagating along the a-axis direction. Each di-hydrogen phosphate anion makes a total of four N-H⋯O(H2PO4 -) hydrogen bonds with two ureido subunits from two different tris-urea receptors, hence each tris-urea receptor provides the two ureido subunits for the encapsulation of the H2PO4 - hydrogen-bonded chain. There are numerous inter-molecular C-H⋯O hydrogen bonds present involving both receptor mol-ecules and the tetra-n-butyl-ammonium cations, so forming a supra-molecular three-dimensional structure. One of the butyl groups and one of the nitro groups are disordered over two positions of equal occupancy.

Visible colorimetric fluoride and hydroxide sensing by asymmetric tris-urea receptors: combined experimental and theoretical studies

A series of asymmetric tris-urea receptors with electron withdrawing group (EWG) or electron donating group (EDG), L1–L4, were synthesized and characterized by HRMS, NMR and single-crystal X-ray diffraction techniques.