Visible, Near-Infrared, and Dual-Range Luminescence Spanning the 4f Series Sensitized by a Gallium(III)/Lanthanide(III) Metallacrown Structure

Abstract

Lanthanide(III) ions (Ln 3+ ) in coordination compounds exhibit unique luminescent properties with narrow and characteristic f-f transitions throughout the visible and near-infrared (NIR) ranges. In addition, some Ln 3+ such as Pr 3+ , Sm 3+ , Dy 3+ , Ho 3+ , Er 3+ and Tm 3+ possess an exceptional ability, although less explored, to exhibit dual-range emissions. Such remarkable features allow highly specific use in materials sciences and biology, for example, for the creation of sophisticated barcode modules or for the next generation of optical imaging applications. Herein, a series of Ga 3+ /Ln 3+ metallacrowns (MCs) with the general composition [LnGa8(shi)8(OH)4]Na•xCH3OH•yH2O (Ln-1, Ln = Pr 3+ , Nd 3+ , Sm 3+ -Yb 3+ and analogue Y 3+ ; H3shi = salicylhydroxamic acid) is presented. Ln-1 were obtained by reacting Ga 3+ and Ln 3+ nitrate salts with the H3shi ligand. X-ray single crystal unit cell analysis confirmed that all MCs are isostructural. The crystal structure was solved for the Nd 3+ analogue and revealed that Nd 3+ is centered between two [12-MCGa III N(shi)-4] MC rings and bound to eight hydroximate oxygen ions (four from each ring) in a pseudo-square antiprismatic fashion adopting a pseudo-D4h symmetry. PGSE DOSY 1 H NMR spectroscopy and ESI mass-spectrometry confirmed that the structure of Ln-1 remains intact in methanol solutions while mass spectrometry suggests that four OHbridges are exchanged with CH3O -/CD3O -. An exceptional ability of this series of MCs to sensitize the characteristic emission of Ln 3+ was confirmed with the observation of bright red and green emission signals of Eu-1 and Tb-1, NIR emissions of Yb-1 and Nd-1, and dual-range emissions of Pr-1, Sm-1, Dy-1, Ho-1, Er-1 and Tm-1 in the solid state upon excitation into ligand-centered bands at 340 nm. The luminescence properties of Ln-1 (Ln = Nd 3+ , Sm 3+ , Eu 3+ , Tb 3+ , Dy 3+ , Yb 3+ ) were also investigated in CH3OH and CD3OD solutions. For Eu-1 and Yb-1 MCs, more extensive analyses of the photophysical properties were performed that included the determination of radiative lifetimes, intrinsic quantum yields and sensitization efficiencies. The absolute quantum yields ( ) of Ln-1 in the visible and in the NIR ranges have been determined. In the case of Sm-1 the values of in CH3OH and CD3OD solutions are exceptionally high, i.e. 10.1(5) % and 83(1) %. Values obtained for Yb-1, i.e. 0.78(4) % in CH3OH and 8.4(1)% in CD3OD, are among the highest ones reported today for Yb 3+ complexes formed with non-deuterated and non-halogenated ligands.Absorption spectra. Absorption spectra (Figure S9) were collected on freshly prepared 50 µM solutions of Ln-1 in methanol (Merck, Uvasol®) placed in quartz cuvettes on a Jasco V670 UV-visible spectrophotometer in absorbance mode.Synthesis and characterization. All reagents and chemicals were purchased from commercial sources and used without further purification. All reactions were carried out aerobically under ambient conditions. Elemental analysis was performed by Atlantic Microlabs Inc. ESI-M...

Structure, reactivity and luminescence studies of triphenylsiloxide complexes of tetravalent lanthanides

“…Indeed, it is known that Pr(III) complexes tend to have very low quantum yields. 36 Upon excitation at 307 or 365 nm, 3-Pr MeCN (Fig. 5, Fig.…”

Synthesis, Structural and Physicochemical Characterization of a Titanium(IV) Compound with the Hydroxamate Ligand N,2-Dihydroxybenzamide

“…The organic molecule N ,2-dihydroxybenzamide (H 2 dihybe) ( Scheme 1 A) incorporates a hydroxamate group in addition to the phenoxy group in the ortho-position and exhibits a rich coordination chemistry with many transition metals [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ] with potential applications in various fields ranging from medicine [ 41 , 42 , 43 ] to materials [ 44 ], and physical sciences [ 40 , 45 ].…”

Dy3+ White Light Emission Can Be Finely Controlled by Tuning the First Coordination Sphere of Ga3+/Dy3+ Metallacrown Complexes

“…21 4). 20 The structure was solved for isostructural [NdGa8(shi)8(OH)4]Na. (D) [DyGa4(shi)4(H2shi)2(NO3)] (2).…”

“…Each of the presented MCs shares a common 12metallacrown-4 motif based on diamagnetic Ga 3+ ring metals and salicylhydroxamic acid (H 3 shi) ring ligands, [12-MC Ga III N(shi) -4]; 15,16 (3), 19 [DyGa 8 (shi) 8 (OH) 4 ]Na ( 4) 20 (bz − = benzoate, pyH + = pyridinium, ip 2− = isophthalate). In addition, the novel MC [DyGa 4 (shi) 4 (bz) 4 ]Na (5) has been synthesized and fully characterized (Figure 1, Scheme S1).…”

“…Each of the presented MCs shares a common 12-metallacrown-4 motif based on diamagnetic Ga 3+ ring metals and salicylhydroxamic acid (H 3 shi) ring ligands, [12-MC Ga III N(shi) -4]; , however, the geometry about the Dy 3+ and the counter cations balancing charges in the structures are varied. Four MCs that we have previously described are newly analyzed for WLE: [DyGa 4 (shi) 4 (bz) 4 ]­(pyH) ( 1 ), [DyGa 4 (shi) 4 (H 2 shi) 2 (NO 3 )] ( 2 ), [Dy 2 Ga 8 (shi) 8 (ip) 4 ]­(NH 4 ) 2 ( 3 ), [DyGa 8 (shi) 8 (OH) 4 ]Na ( 4 ) (bz – = benzoate, pyH + = pyridinium, ip 2– = isophthalate). In addition, the novel MC [DyGa 4 (shi) 4 (bz) 4 ]Na ( 5 ) has been synthesized and fully characterized (Figure , Scheme S1).…”