Chemical Conversion of a Coumarin Derivative Containing Arylhydrazono: Crystal Structures and Fluorescence Properties

An arylhydrazono-containing coumarin derivative(1) can undergo chemical conversions in two modes. When in the presence of Cu^(2+), a Cu^(2+)-promoted cyclization reaction was observed in aqueous acetonitrile and gives compound 2, while a ring-opening reaction occurs to give compound 3 in the absence of Cu^(2+). Both 2 and 3 were characterized by single-crystal X-ray diffraction. Compound 2 crystallizes in monoclinic C2/c space group with a = 26.606(5), b = 5.8142(12), c = 26.906(5) ?, β = 103.41(3)°, Z = 8, F(000) = 1696, μ = 0.186 mm^(-1), R = 0.0487 and wR = 0.1129. Compound 3 crystallizes in monoclinic P21/n space group with a = 9.917(2), b = 13.644(3), c = 15.912(3) ?, β = 95.38(3)°, Z = 4, F(000) = 896, μ = 0.182 mm^(-1), R = 0.0769 and w R = 0.1617. The spectroscopic studies show that compound 2 exhibits strong fluorescence emission.