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A pyrazine as ancillary ligand coordinated to dysprosium(III) tris-acetylacetonate complex was synthesized and thoroughly characterized. Photophysical properties of the Dy(III) complex were investigated both in solution and solid powder. The quantum yield ( ɸ) of the complex in chloroform is 0.024. The UV excitation of the complex in the solid state generates white light emission which indicates significant energy transfer from the ligands (acetylacetone and pyrazines) to the Dy(III) ion. This could be due to the appropriate balancing of the intensity ratio of the yellow and blue emission bands of the Dy(III) complex. This represents an example of a single component system. The correlated colour temperature (CCT) of this white light is calculated as 5340.21 K which lies in a cool region. The radiative properties of the Dy(III) complex are calculated using Judd-Ofelt analysis and the phenomenological parameters calculated are Ω 2  = 8.07 × 10 −20  cm 2 , Ω 4  = 1.94 × 10 −20  cm 2 and Ω 6  = 1.67 × 10 −20  cm 2 . The branching ratio ( β R ) ratio calculated from the emission spectrum follows the order: 4 F 9/2  →  6 H 13/2  >  4 F 9/2  →  6 H 15/2  >  4 F 9/2  →  6 H 11/2 . The β R for the 4 F 9/2  →  6 H 13/2 transition is highest, and it contributes 83% to the total emission branching and can be considered as a possible transition for laser amplification. The white light emission from the solid powder Dy(III) complex as a single component may possibly find its use in white light emitting devices (WLEDs). [ABSTRACT FROM AUTHOR]

A series of NIR emitting novel ytterbium tris β-diketonate ternary complexes, [Yb(tta) 3 (L)]·H 2 O {tta = thenoyltrifluoroacetylacetone and L = dibenzyl sulphoxide (dbso), diphenyl sulphoxide (dpso) and benzoguinamine (bga)} was synthesised, and the photophysical and optoelectronic properties of their films were studied. Nuclear Magnetic Resonance (NMR) analysis indicates that the complexes are seven-coordinate which is a highly asymmetric structure enhancing the radiative transitions. It is an indicative of efficient energy transfer from coordinated ligands to Yb ion. The complexes were doped in Tris(4-carbazoyl-9-ylphenyl)amine (TcTa) organic matrix and the doped samples were used as the emitting layers to fabricate near-infrared organic light emitting diodes (NIR-OLEDs) with the structure: Indium tin oxide/{N,N′-bis(naphtalen-2-yl)-N,N′-bis(phenyl) benzidine} (25 nm)/[Yb-complexes] (10%): TcTa (40 nm)/(2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline) (15 nm)/tris(8-hydroxy-quinolinato) aluminium (10 nm)/LiF (0.5 nm)/Al (120 nm). The complex, [Yb(tta) 3 (dpso)]·H 2 O shows the highest electroluminescence (EL) efficiency with maximum irradiance of 22.48 μW/cm 2 and current density of 29.5 mA/cm 2 at 15 V. It indicates an improved EL performance over the reported devices based on the Yb (III) complexes. In view of electrical characteristics, the current-voltage responses were interpreted by using Mott–Gurney model which allows us to determine the carrier mobility of the complexes. [ABSTRACT FROM AUTHOR]

This paper presents NIR photoluminescence of nine-coordinate lanthanide complexes, [Ln(hfaa) 3 (tptz)[ hfaa= hexafluoroacetylacetone, tptz= 2, 4, 6-tris-(2-pyridyl)-s-triazine) and Ln= La, Nd, Yb]. [Display omitted] • Photoluminescence of NIR emitting X-ray characterised nine-coordinate complexes is described. • The NMR analysis of the paramagnetic Nd(III) and Yb(III) complexes in two different solvents is presented. • Paramagnetic shifts (δ/Δδ) of the complexes is calculated and discussed. • Calculation of longitudinal relaxation rates (ρ1) of the complexes, [Ln(hfaa) 3 (tptz)]. Three nine-coordinate ternary complexes of La(III), Nd(III) and Yb(III) of general composition, [Ln(hfaa) 3 (tptz)] {hfaa = hexafluoroacetylacetone and tptz = 2, 4, 6-tris-(2-pyridyl)-s-triazine} are synthesised and comprehensively characterised. The X-ray single crystal structure and NMR studies show that the coordination structure of the complexes is nine-coordinate monocapped square antiprismitic in both solid and solution states with LnO 6 N 3 (six oxygen atoms from three hfaa and three nitrogen atoms from one tptz) polyhedra. The complexes are stable in non-coordinating (chloroform) and coordinating (methanol) solvents as indicated by NMR spectrum where no dissociation of any ligand/s is observed. The longitudinal relaxation rate (ρ = 1/T 1) is very fast in the cases of paramagnetic Nd(III) and Yb(III) complexes as compared to their diamagnetic La(III) analogue, suggesting their possible use as a relaxation probe in the magnetic resonance imaging. The complexes, on UV light excitation, show characteristic near infra-red emission transitions; 4F 3/2 →4I j=9/2, 11/2, 15/2 of Nd(III) and 2F 5/2 →2F 7/2 of Yb(III) ions. The tptz ligand has proved very efficient antenna as it increased the photoluminescence quantum yield of Nd(III) complex. The complexes showed considerable improved photophysical properties in NIR region, which could lead them as significant candidates in developing new materials for more efficient laser and optical amplifier systems, and windows transparent to the biological tissues [ABSTRACT FROM AUTHOR]

Lanthanide tris(β-diketonate) complexes of variant coordination numbers with the compositions [La(hfaa) 3 (bpy) 2 ] ( 1 ), [Nd(hfaa) 3 (bpy)(H 2 O)]·½bpy ( 2 ), [Sm(hfaa) 3 (bpy)(H 2 O)]·bpy ( 3 ) and [Ln(hfaa) 3 (bpy)] (Ln = Nd ( 4 ), Sm ( 5 ), Eu ( 6 ), Ho ( 7 ), Er ( 8 ) and Yb ( 9 ); hfaa = anion of hexafluoroacetylacetone and bpy = 2,2′-bipyridine) have been synthesized and fully characterized. The single crystal analysis of ( 2 ) and ( 3 ) reveals that Nd and Sm are mononuclear and nine-coordinate (LnO 7 N 2 ) with a monocapped square antiprismatic geometry. The photophysical parameters obtained are lower than their anhydrous eight-coordinated analogues. The complexes show high quantum efficiencies in the both visible and NIR regions, which could be related to the formation of highly protected coordination environments (LnO 6 N 4 or LnO 6 N 2 ) by the hfaa − and bpy ligands around the Ln(III) ions. Finally, these volatile and luminescent complexes were used to fabricate OLEDs. The best Vis–NIR devices with the structures: ITO/CuPc (15 nm)/[Sm(hfaa) 3 (bpy)] or [Nd(hfaa) 3 bpy]:CBP or [Er(hfaa) 3 bpy]:CBP or [Yb(hfaa) 3 bpy]:CBP (50 nm)/BCP (20 nm)/AlQ (30 nm)/LiF (1 nm)/Al (100 nm), show a maximum brightness of 45 cd/m 2 with a current efficiency of 0.19 cd/A for visible devices, while the NIR devices exhibit a maximum NIR irradiance and a maximum external quantum efficiency (EQE) of 28 μW cm −2 and 0.022% for Nd(III), 0.50 μW cm −2 and 0.011% for Er(III) and 93 μW cm −2 and 0.18% for Yb(III), respectively, which indicate highly improved EL performance over devices reported in the literature. [ABSTRACT FROM AUTHOR]

Synthesis, photoluminescence, 4f–4f absorption, and NMR studies of highly volatile nine-coordinate complexes [Ln(hfaa)3(L)3] (Ln = La, Pr, Nd, and Sm; hfaa is the anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and L = 1H-indazole) are described. NMR spectra reveal that three L are attached to the metal. The chemical shifts of β-diketonate and Hind protons are in opposite directions and the lanthanide induced paramagnetic shifts are dipolar. The low molecular symmetry of the complexes leads to intense luminescence with prominent Stark splitting of the bands and high oscillator strength of the hypersensitive transition. The band shape of the 4G5/2, 2G7/2 ← 4I9/2 transition of neodymium is similar to that of nine-coordinate complexes. Coordinating solvents have pronounced effect on the oscillator strength and band shape. The experimental intensity parameter (η Sm) for the samarium complex is calculated and analyzed. The complexes could be used as precursors for high-performance lanthanide-based materials through chemical vapor deposition. [ABSTRACT FROM PUBLISHER]

Abstract: A highly volatile air and moisture stable eight-coordinate samarium complex, [Sm(hfaa)3(pz)2] (hfaa=anion of hexafluoroacetylacetone and pz=pyrazole), has been synthesized and structurally characterized by single crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P21/c and the coordination polyhedron around the samarium ion is best describable as a distorted square antiprism. The NMR spectrum reveals that both the pz units remain coordinated to the samarium in solution. The quantum yield of the complex is determined to be 0.012 in solution. The lifetime of the complex is found to be 0.039ms (χ 2 =1.071). The experimental intensity parameter (η Sm) is calculated for the complex. [Copyright &y& Elsevier]

Abstract: The paper reports the syntheses, 1H NMR spectral and luminescence spectral studies of eight-coordinate Sm, Eu, Tb, Dy and Tm complexes of the type [Ln(hfaa)3(phen)] (hfaa=hexafluoropentanedione and phen=1,10-phenanthroline). These complexes have been synthesized in high yields by modifying a method reported in literature for synthesizing similar complexes. Large up field and downfield shifts were observed in their 1H NMR spectra. The lanthanide induced chemical shifts in these paramagnetic complexes are dipolar in nature. The H(2) and H(4) proton resonances of phen of the thulium complex have been shifted to highfields which is unusual. Inter- and intra-molecular chemical shift ratios are similar for Sm and Eu complexes as these are isostructural in solution. The quantum yields (Φ =46% for Eu, 32% for Tb, 2.7% for Sm and 2.1% for Dy) of the complexes indicate that energy transfer from ligands (hfaa and phen) to Ln(III) is efficient. The luminescence in the Dy(III) complex is the least intense due to poor intramolecular energy transfer match as compared to rest of the complexes. The lanthanide ions in these complexes have low symmetry sites. [Copyright &y& Elsevier]

Abstract: Synthesis of four nine-coordinate lanthanide (III) complexes of the type, [Ln(hfaa)3(tptz)], where Ln=La, Nd, Sm and Tb; hfaa=the anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and tptz=2,4,6-tris(2-pyridyl)-1,3,5-triazine, by a new modified one pot in situ method is reported. The lanthanide ions are coordinated to three N-atoms of three 2-pyridyl units of tptz besides six O-atoms of three hfaa units. The formation of these volatile complexes is confirmed by molecular ion peak in ESI-MS, IR and NMR. The hypersensitive 4G5/2, 2G7/2 ← 4I9/2 transition displays distinct band shape which is different from the band shape of known eight- and ten-coordinate complexes. The samarium and terbium complexes emit pink and green luminescence due to 4G5/2 → 6Hj (j=5/2, 7/2, 9/2) and 5D4 → 7F j (j=3-6) transitions, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Solution studies on the complexes of the type [Ln(hfaa)3(phen)2] (Ln=La, Pr and Nd) and [Ln(hfaa)3phen] (Ln=Nd, Ho, Er and Yb; hfaa stands for the anion of 1,1,1,5,5,5-hexafluoro-2,4-pentanedione and phen stands for 1,10-phenanthroline) are presented. These complexes are synthesized in high yields by an in situ method in which hfaa, ammonium hydroxide, lanthanide chlorides and phen were allowed to react in 3:3:1:1 molar ratio in ethanol. In the case of neodymium both eight- and ten-coordinate complexes are isolated. The paramagnetic shifts of the methine protons of β-diketone have their sign opposed to those of paramagnetic shifts of phen protons and the shifts are dominated by dipolar interactions. The inter- and intramolecular shift ratios have been calculated and discussed. The 4f–4f absorption spectra of the complexes of Pr, Nd, Ho and Er are analyzed. The eight- and ten-coordinate neodymium complexes display distinctively different band shapes of the 4G5/2,2G7/2 ← 4I9/2 hypersensitive transition. The efficient energy transfer from ligand to Pr(III) is reflected by strong red luminescence of this complex at room temperature. [ABSTRACT FROM AUTHOR]

This paper reports synthesis, characterisation and photophysical properties of the visible and NIR emitting distorted square antiprismatic (C 4V) ternary [Ho(hfaa) 3 (H ind) 2 ] and [Tm(hfaa) 3 (H ind) 2 ], complexes. • Visible and NIR luminescence. • Blue emission. • Luminescence from Ho and Tm complexes. • Potential candidates for optical communications and of broadening amplification band. A sensitizer ligand, 1,1,1,5,5,5-Hexafluoro-2,4-pentandione (Hhfaa) is employed to synthesize two new ternary–lanthanide(III) complexes, [Ho(hfaa) 3 (H ind) 2 ] and [Tm(hfaa) 3 (H ind) 2 ], in which the monodentate N-donor indazole (H ind) was used as the antenna ligand. Both the complexes were characterised thoroughly. The single-crystal XRD suggests that the complexes are eight-coordinate where the metal ions are coordinated to three hfaa̶ and two H ind ligands making the coordination polyhedra as LnO 6 N 2 with distorted square antiprismatic geometries. The one- and two-dimensional NMR analyses confirm the eight-coordinate structures and show that the complexes are isostructural in the solution. The complexes are thermally stable up to 200 °C, which is quite suitable to find the potential application in the optoelectronic devices. Furthermore, the UV-excitation of the complexes led to characteristic emission transitions in the visible and NIR regGive a space between NIR and region on from the [Ho(hfaa) 3 (H ind) 2 ] and [Tm(hfaa) 3 (H ind) 2 ] complexes. The NIR luminescence, particularly 1.5 μm from the Ho complex and 1.4 μm from the Tm complex makes them potential candidates for optical communications and of broadening amplification band from C– band (1530–1560 nm) to S + band (1450–1500 nm) in optical fibre, respectively. [ABSTRACT FROM AUTHOR]

Dual detection systems are of interest for rapid, accurate data collection in sensing systems and in vitro testing. We introduce an IrIII complex with a boronic acid receptor site attached to the 2‐phenylpyridine ligand as an ideal probe with photo‐ and electrochemical signals that is sensitive to monosaccharide binding in aqueous solution. The complex displays orange luminescence at 618 nm, which is reduced by 70 and 40 % upon binding of fructose and glucose, respectively. The electro‐chemiluminescent signal of the complex also shows a direct response to monosaccharide binding. The IrIII complex shows the same response upon incorporation into hydrogel matrices as in solution, thus demonstrating the potential of its integration into a device, as a nontoxic, simple‐to‐use tool to observe sugar binding over physiologically relevant pH ranges and saccharide concentrations. Moreover, the complex's luminescence is responsive to monosaccharide presence in cancer cells. [ABSTRACT FROM AUTHOR]