Organotin compounds bearing C3-symmetric Schiff base: Microwave-assisted multicomponent synthesis and their photophysical properties

Abstract

Two new fluorescent organotin compounds bearing C3-symmetric Schiff base were synthesized by microwave irradiation via multicomponent reaction (3-MCR), in one pot in just 30 mins with excellent yields. Both tin complexes were fully characterized by NMR, IR, UV-vis, fluorescence spectroscopy, high-resolution mass spectrometry and by ciclyc voltametry. The δ 119Sn and 3J(1H,119Sn) of new organotin complexes 4 and 5 showed the high molecular symmetry and the trinuclearity through high resolution mass spectrometry. Both Sn-complexes are thermally stable up to 300°C. The small-wide angle X-ray scattering pattern in powder and the 2D monomolecular film by scanning tunneling microscopy (STM) of 5 showed a lamellar like assembly with dimension of 2.38 and 2.80 nm, respectively, meaning that molecules adopt a face-on arrangement, where molecules are flat-lying on the HOPG surface. Monolayer of 5 is mesoporous and rigid but covers large surface areas. The photophysical, electrochemical, and theoretical studies reveal that the three Sn-nuclei do not electronically interact. Since, both organotin complexes exhibit good quantum yield in solution (Φ 4: 52.4 % and 5: 51.7 %), with lifetimes in the range τ =∼3 ns, their emission properties are appealing for OLED applications.