Near-Infrared and Visible Luminescence from Terphenyl-Based Lanthanide(III) Complexes Bearing Amido and Sulfonamido Pendant Arms

Abstract

A series of m‐terphenyl‐based ligands bearing three coordinating oxyacetate and two amido or two sulfonamido groups, (1a‐b)H3 and (2)H3, respectively, have been synthesized and characterized. The structures of the corresponding neutral complexes have been studied using 1H‐NMR spectroscopy and luminescence experiments. The photophysical properties of the (1a‐b)Eu, (2)Eu, (1a)Tb, and (2)Tb complexes have been studied to determine the structure of the first coordination sphere in methanol. The first coordination sphere consists of eight donor atoms provided by the ligand (three chelating oxyacetate groups and two amide or sulfonamide oxygens), and one methanol molecule. The (1a)Dy and (1a)Sm complexes exhibited sensitized luminescence in the visible spectral region, but the luminescence intensity was very sensitive to quenching by C‐H groups. The near‐infrared emitting (1a)Ln and (2)Ln complexes exhibited sensitized luminescence at wavelengths (at 880, 1060, and 1330 nm for Nd3+, at 980 nm for Yb3+, and at 1550 nm for Er3+) of interest for applications in optical telecommunication devices. The luminescence lifetimes of these complexes in DMSO and [D6]DMSO are in the range of microseconds. The luminescent state of the NIR emitting lanthanide ions is very efficiently quenched by high frequency oscillators (such as C‐H groups) in the solvent and the ligand.

Highly Emitting Near-Infrared Lanthanide “Encapsulated Sandwich” Metallacrown Complexes with Excitation Shifted Toward Lower Energy

“…It is known that f-f transitions have very low molar absorption coefficients, and we only could succeed in measuring the absorption spectrum of the 2 F 5/2 ← 2 F 7/2 transition in Yb 3+ [Zn(II)MC quinHA ] ( Figure S5 ). A value of τ rad = 0.68(7)ms was found for Yb 3+ [Zn(II)MC quinHA ] , which is shorter than the radiative lifetimes reported for Yb 3+ (diethylenetriaminepentaacetate) 2- and Yb 3+ (dipicolinate) 3- complexes (1.2–1.3 ms) 77 , 78 or for Yb 3+ with terphenyl-based ligands, ∼2 ms, 79 but close to the values found for Yb 3+ complexes with benzoxazole-substituted 8-hydroxyquinolines (0.7–0.75 ms) which exhibit high quantum yields. 44 Using eq 1 and taking into account τ obs and Q Ln L of Yb 3+ [Zn(II)MC quinHA ] in methanol (Table 1 ), we have been able to obtain quite modest values of the intrinsic quantum yield, 2.2(3)%, and of the sensitization efficiency of the ligand, 12(3)%.…”

Highly near-IR emissive ytterbium(iii) complexes with unprecedented quantum yields

“… 7 Despite a high sensitization efficiency (close to 100%) being achieved, the overall luminescence quantum yields of Yb porphyrinates are still low (<5%), 8 most likely due to detrimental C–H oscillators in the vicinity of the Yb ion lowering the intrinsic quantum yields. 9 …”

Strong erbium luminescence in the near-infrared telecommunication window

“…However, the presently known luminescent inorganic erbium compounds or glasses are not compatible with polymeric matrices, due to their very low solubility in a polymer matrix and the difficulties to disperse them in a polymer. On the other hand, erbium coordination compounds can show luminescence and are compatible with polymers [4][5][6][7][8][9][10][11].…”