Near-Infrared Luminescence from Visible-Light-Sensitized Ruthenium(II)‑Neodymium(III) Heterobimetallic Bridged Complexes Containing Alkoxy(silyl) Functional Groups

Abstract

New infrared emitting d-f (ruthenium(II)-neodymium(III)) heterobimetallic complexes with alkoxy(silyl) functional groups have been prepared. Visible excitation evidenced energy transfer processes from the ruthenium(II) donor to neodymium(III) acceptors leading to infrared emission. Energy transfer rates (k EnT) and efficiency of energy transfer (η EnT) are, respectively, 0.61 × 10 7 s-1 and 44% for RuL 1-NdL 3 complex. Larger values of k EnT (3.04 × 10 7 s-1) and η EnT (84%) were detected for RuL 2-NdL 4 complex. RuL 1-NdL 3 and RuL 2-NdL 4 complexes were fully characterized by elementary analysis (EA), mass spectrometry (MS), Fourier transform infrared spectroscopy (FTIR) and Fourier transform Raman spectroscopy (FT-Raman). Total correlation spectroscopy (TOCSY1D), 1 H{ 13 C} heteronuclear single quantum correlation (HSQC) and 1 H{ 13 C} heteronuclear multiple bond correlation (HMBC) nuclear magnetic resonance (NMR) analyses were also carried out to characterize NdL 3 and RuL 1-NdL 3 complexes. The presence of trialkoxysilyl-substituted ligands would allow further grafting onto any silica or silicated surface aiming at applications as new luminescent near infrared (NIR)-emitting biosensors or biomarkers.

Luminescent nanohybrids based on silica and silylated Ru(II)—Yb(III) heterobinuclear complex: new tools for biological media analysis

“…The emission spectra (figure 3(a4)) display similar profiles relating to the free RuL 2 YbL 4 complex. By monitoring the excitation up to 400 nm, the broad emission bands observed at 980 nm were ascribed to Yb(III) 2 F 5/2 → 2 F 7/2 transitions [19,26,29,30]. It is worth emphasizing that monitoring excitation up to 400 nm a split of 2 F 5/2 → 2 F 7/2 transitions could be detected as exhibited in figure 3(a4), red line).…”

“…For the SiO 2 -RuL 2 YbL 4 nanohybrid, the excitation spectrum (figure 3(a3)) displays a broad excitation band from 270 to 400 nm assigned to ligands transitions (TTA, bpy-Si and bpmd) [17,21,27,28]. Bands above 400 nm were ascribed to Ru(II) 3 MLCT transition [19,26]. The emission spectra (figure 3(a4)) display similar profiles relating to the free RuL 2 YbL 4 complex.…”

“…By monitoring the luminescence properties of Ru(II) moieties in the nanohybrids the emission levels were determined as shown in figures 3(a1) and (b1). A broad emission band was observed and it can be ascribed to the Ru(II) 3 MLCT emission to the ground state [19,26] at 610 and 614 nm for SiO 2 -RuL 2 YbL 4 and SiO 2 d-RuL 2 YbL 4 , respectively. The excitation spectra for both nanohybrids, obtained by monitoring the Ru(II) 3 MLCT emission, show bands assigned to the d → π * 1 MLCT (MLCT) transitions and transitions centered on ligands, as π→π * transitions [19,26].…”

“…For the SiO 2 d-RuL 2 YbL 4 nanohybrid, the excitation spectrum ( figure 3(b3)) displays a broad band at 345 nm resulting from ligands transitions (TTA, bpy-Si and bpmd) [17,21,27,28] and a low intensity band above 400 nm assigned to the Ru(II) 3 MLCT transitions [19,26]. By monitoring the excitation up to 400 nm, the broad emission bands (figure 3(b4)) centered at 979 nm were ascribed to Yb(III) 2 F 5/2 → 2 F 7/2 transitions [19,26,29,30]. When the excitation was monitored on the Ru(II) 1 MLCT transition, the similar broad band was also detected [19,26,29,30].…”

“…This approach prevents nonhomogeneous embedding and leaching of luminescent probe from host matrix [16,17]. In our previous work [18,19], bipyridine and diketone derivative ligands such as bpy-Si and TTA-Si appropriately substituted by a trialkoxysilyl groups were successfully isolated and used to synthetize silylated d f heterobinuclear complexes. Previously, we have described the synthesis of highly luminescent silylated [Eu(TTA-Si) 3 ] and [Eu(TTA) 3 (bpy-Si)] complexes grafted onto mesoporous and dense silica nanoparticles [17,20].…”