New fluorescent [Ag(I)(Schiff base)] complexes derived from 9-anthracenecarboxaldehyde and their application in thin layers deposition

New Ag(I) complexes with Schiff bases derived from 9-anthracenecarboxaldehyde and 2-thiopheneethylamine thet(9-anthraceneca) (L1) or (1R,2R)(+)-diphenylethylenediamine (1R,2R)(+)-diphenen(9-anthraceneca) (L2) were obtained and characterized by 1H, 13C, 15N NMR, 1H differential Nuclear Overhauser Effect (NOE diff.) NMR technique, UV–Vis, CD and IR spectroscopy in solution and in the solid phase. X-ray crystal structure of [Ag(thet(9-anthraceneca))2]NO3] (1), revealed silver(I) linearly coordinated by the ligand imine nitrogen atoms. X-ray crystal structure detremination and DFT calculations for complexes and ligands, related confirming their geometry in solution and in the solid phase. 1H NMR NOE diff. spectra indicate that both Schiff bases adopt different conformation in solution and in the solid state. For Ag complexes with (L1) and (L2) the significant NOE enhacement between the imine hydrogen atoms and hydrogen of the aromatic rings was observed, indicating changes of the silver ion coordination sphere in solution. The highest quantum yield of the fluorescence was achieved for (2) with φ2 = 0.52 (λex = 347 nm). For all investigated compounds the fluorescence is related to the excitation HOMO → LUMO + 1 or HOMO → LUMO in the anthracene moiety. The homogeneous layers of complexes uniformly covering the silicon substrate have been obtained with a spin- or dip-coating techniques and characterized by scanning electron microscopy (SEM/EDS) and atomic force microscopy (AFM). The complex [Ag2((1R,2R)(+)-diphenen(9-anthraceneca))(NO3)2] (2) was deposited on Si(1 1 1) covered with PMMA. Fluorescence spectra of [Ag(thet(9-anthraceneca))2]NO3] (1)/Si materials exhibit emission at 480 nm from intra-ligand transitions (λex = 360 nm) and differ slightly from the spectra obtained for the solid complexes or their solutions. The highest fluorescence intensity was noted for the layers obtained by a multistage deposition at variable spin rates and deposition time 5 s.