Tweezers-like aromatic molecules and their luminescent properties depending on the structures

Di(hydroxyphenyl)pyrimidine with two anthryl substituents 1a was synthesized and characterized by X-ray crystallography and NMR spectroscopy. The molecule prefers ‘U’-shaped conformation supported by intramolecular O–H···N hydrogen bonds in the solid state and in solution. The CHCl3-solvated compound binds two CHCl3 molecules between the two parallel anthryl planes. Hexylation of the OH groups of 1a produces 1c whose diarylpyrimidine core contains these aromatic planes with O···H–C interaction and helical alignment. Compound 1c shows strong emission from the anthryl groups (410 nm, φ = 0.39), while luminescence is not observed for 1a partly due to quenching via PET (photo-induced electron transfer) process.