Towards white light emission from a hybrid thin film of a self-assembled ternary samarium(iii) complex

A new samarium complex [Sm(hfaa)₃(Py-Im)] (ML) was synthesized by utilizing hexafluoroacetylacetone (hfaa) and 2-(2-pyridyl)benzimidazole (Py-Im) as coordinating ligands. Single crystal X-ray analysis shows that in the solid-state the complex dimerizes through intermolecular hydrogen-bonding with N-H⋯O (2.127 Å) and N-H⋯F (2.576 Å) interactions. The complex in the solid-state displayed highly monochromatic brilliant red emission with Commission International de I'Eclairage (CIE) color coordinates of 0.6532; 0.3336, with a remarkably long luminescence lifetime (τ_exp. ≈ 204.47 ± 4.043 μs) and a high intrinsic quantum yield (QSmSm ≈ 6.60%). Furthermore, the complex in different organic media displayed color tunability from orange (CIE; 0.6071; 0.3568) to violet (CIE; 0.3634; 0.2144) with τ_exp. from 105.50 ± 0.143 to 14.27 ± 0.033 μs. Hybrid and flexible thin films obtained by doping different concentrations (1%, 2%, 4% and 6%) of the complex into the poly(urethane) (PU) polymer matrix also exhibited color tunability from violet (CIE; 0.3380; 0.2162) to light orange (CIE; 0.5666; 0.3408). White light emission from a 1% doped thin film of the complex was realized by changing the excitation wavelength. Thus, the new material could be a potential candidate for the fabrication of full-color display devices and for solid-state lighting (SSL) applications.