A novel Schiff base macrocycle based on 1,1'-binaphthyl for fluorescence recognition

Regio- and Enantioselective Macrocyclization from Dynamic Imine Formation: Chemo- and Enantioselective Fluorescent Recognition of Lysine

The dynamic covalent chemistry of imines is utilized to conduct a regioselective as well as enantioselective synthesis of an unsymmetric (C1) chiral macrocycle from the reaction of an unsymmetric (C1) chiral dialdehyde, (S)-4, that contains a salicylaldehyde unit and a benzaldehyde unit, with lysine, an unsymmetric (C1) chiral diamine. The enantioselectivity is further enhanced in the presence of Zn2+. Compound (S)-4 in combination with Zn2+ is found to be a highly chemoselective as well as enantioselective fluorescent probe for lysine. It can be used to detect specific enantiomers of this amino acid.

New Dinuclear Macrocyclic Copper(II) Complexes as Potentially Fluorescent and Magnetic Materials

Two dinuclear copper(II) complexes with macrocyclic Schiff bases K1 and K2 were prepared by the template reaction of (R)-(+)-1,1'-binaphthalene-2,2'-diamine and 2-hydroxy-5-methyl-1,3-benzenedicarboxaldehyde K1, or 4-tert-butyl-2,6-diformylphenol K2 with copper(II) chloride dihydrate. The compounds were characterized by spectroscopic methods. X-ray crystal structure determination and DFT calculations confirmed their geometry in solution and in the solid phase. Moreover, intermolecular interactions in the crystal structure of K2 were analyzed using 3D Hirshfeld surfaces and the related 2D fingerprint plots. The magnetic study revealed very strong antiferromagnetic CuII-CuII exchange interactions, which were supported by magneto-structural correlation and DFT calculations conducted within a broken symmetry (BS) framework. Complexes K1 and K2 exhibited luminescent properties that may be of great importance in the search for new OLEDs. Both K1 and K2 complexes showed emissions in the range of 392-424 nm in solutions at various polarities. Thin materials of the studied compounds were deposited on Si(111) by the spin-coating method or by thermal vapor deposition and studied by scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM), and fluorescence spectroscopy. The thermally deposited K1 and K2 materials showed high fluorescence intensity in the range of 318-531 nm for K1/Si and 326-472 nm for the K2/Si material, indicating that they could be used in optical devices.

Porous organic cage for enantiomeric fluorescence recognition of amino acid and hydroxy acid

A new method based on the enantioselective recognition of porous organic cages CC3-R was established for the first time. Porous organic cages are widely used for separation, adsorption and host-guest interaction sensing, but are rarely used for fluorescence sensing. Based on the inherent chiral environment of CC3-R and the inherent fluorescence properties of the organic ligands constituting the cage, when different chiral monomers diffuse into the cage, different effects occur to produce changes in fluorescence. We found for the first time that the fluorescence of CC3-R can be enhanced and quenched by tyrosine and mandelic acid, respectively, and that different chiral monomers are enhanced or quenched differently at the same concentration. Unlike the chiral recognition of other composite luminescent materials, the chiral porous organic cage not only utilizes its own host-guest effect for chiral recognition, but also utilizes the organic ligands constituting the cage for luminescence recognition. This work provides an alternative method to accomplish chiral recognition other than chromatography, that is using porous organic cages (POC), but it can show the advantages of simplicity, low cost and high sensitivity. We believe this work could provide valuable thoughts in the exploration of POC in chiral recognition as new FL probes for the future.