Features of the Molecular Structure and Luminescence of Rare-Earth Metal Complexes with Perfluorinated (Benzothiazolyl)phenolate Ligands

Abstract

A set of Sc, Nd, Sm, Eu, Ho, Gd, Er, Yb complexes with perfluorinated 2-(benzothiazol-2-yl)phenolate ligands Ln(SONF)3(DME) were synthesized by the reactions of silylamides Ln[N(SiMe3)2]3 with phenol H(SONF). The structure of the initial phenol, Sc, and Er complexes was established using X-ray analysis, which revealed that the obtained compounds are mononuclear, in contrast to the binuclear non-fluorinated analogues [Ln(SON)3]2 synthesized earlier. All the obtained complexes, both in solid state and in tetrahydrofuran (THF) solutions, upon excitation by light with λex 395 or 405 nm show intense luminance of the ligands at 440–470 nm. The Eu complex also exhibits weak metal-centered emission in the visible region, while the derivatives of Sm luminesces both in the visible and in the infrared region, and Nd, Er, and Yb complexes emit in the near IR (NIR) region of high intensity. DFT (density functional theory) calculation revealed that energy of frontier orbitals of the fluorinated complexes is lower than that of the non-fluorinated counterparts. The level of highest occupied molecular orbital (HOMO) decreases to a greater extent than the lowest occupied molecular orbital (LUMO) level.

Synthesis and photophysical properties of rare earth (La, Nd, Gd, Y, Ho) complexes with silanediamido ligands bearing a chelating phenylbenzothiazole chromophore

“…A more efficient sensitization was observed for the Nd complex (at the level 4 G 5/2 , E = 17 135 cm −1 ) with perfluorinated benzothiazolate, the triplet level energy of which was determined as 20 600 cm −1 , but for Ho 3+ this gap appeared too large. 35 All the studies recommend Pbt-derivatives as sensitizers primarily for visible-light emitting lanthanides, and secondary for Nd and Yb in the NIR region. We anticipated that joining two chromophoric fragments with a silylene bridge would result in complexes that are stable in solutions, and aimed to study their structure, determine the triplet level energy, and study luminescence sensitization.…”

Structural and Luminescent Features of Lanthanide Ate Complexes with Polychlorinated 2-Mercaptobenzothiazolate Ligands

“…The polychlorinated 2-mercaptobenzothiazoles were obtained in high yields. The new compound Hmbt Cl4 was characterized by 1 H and 13 C nuclear magnetic resonance (NMR) spectroscopy (Figure S1), mass spectroscopy (Figure S2), and Fourier transform infrared (FTIR) spectroscopy (Figure S3). The synthesized chlorinated mercaptothiazoles were applied to encapsulate lanthanide ions in ate complexes.…”

“…1 H NMR (THFd 8 ): δ (ppm) = 12.88 (N−H, broad). 13 [Na(DME) 3 ] + [Nd(mbt Cl2 ) 4 ] − (1). A mixture of Hmbt Cl2 (0.424 mmol, 100 mg), Nd[N(SiMe 3 ) 2 ] 3 (0.106 mmol, 66.1 mg), and NaN(SiMe 3 ) 2 (0.106 mmol, 19.4 mg) in a DME solution (10 mL) was stirred at room temperature for 10 min.…”

“…Therefore, the generally accepted strategy for designing highly NIR-emissive lanthanide substances is to eliminate O–H and N–H bonds from the ligand structure and to replace C–H bonds with carbon–halogen bonds . Currently, the main focus in this field is to develop a perfluorinated environment for lanthanide-based NIR emitters. − While the application of heavier halogens for this purpose is rare, recent reports suggest that they may increase the sensitization efficiency …”

Recent Advances of Near-Infrared (NIR) Emissive Metal Complexes Bridged by Ligands with N- and/or O-Donor Sites

“…NIR light-emitting metal complexes display unique potential applications in electroluminescence, magnetism, chemosensors, optical telecommunication, and bioimaging. Most of the above-mentioned research on complexes with bridging ligands is based on their near-infrared luminescence properties [68][69][70][71][72][73][74]. Herein, NIR light-emitting metal complexes with bridging ligands in different fields of applications are introduced below.…”