Complexes with furyl-substituted 3-hydroxychromone: synthesis, characterization and fluorescence studies

2-(2-Furyl)-3-hydroxychromone (HL) reacts with M^II ions in the formation of quadratic [Cu(L)₂] (3), octahedral [M(L)₂(OH₂)₂] (M = Co (1), Ni (2), Zn (4), Mn (5)) and seesaw [M(L)₂] (M = Sn (6), Pb (7)) complexes. Recrystallization of complexes 1-3 in presence of pyridine lead to [M(L)₂(py)₂] (1a-3a) adducts. All compounds were characterized by Fourier transform infrared spectroscopy (FTIR). Complexes 1-7 were analyzed by UV-Vis and diffuse reflectance spectroscopies. The estimated band gap energies range from 2.90-3.15 eV. The crystal structure of complexes 6 and 7 revealed the influence of the stereochemically active lone pair due to their electronic configuration ns² . An intense fluorescence emission band centered at approximately 600 nm (λ_exc centered at 340 nm) has been observed for complex 6 in the solid state. In N,N-dimethylformamide (DMF) solution, complex 6 showed two emission bands (468 and 538 nm) when excited from 300 to 380 nm, and only one emission band (468 nm) when excited from 385 to 420 nm. (author)