Ternary Europium Complexes Research Articles

Luminescence enhancement of Europium(III) complexes by an ionic liquid

Europium(III) complexes are urgently needed in practical application of optoelectronic devices. Here, strongly red-light emitting ternary europium(III) complexes have been successfully synthesized through the co-chelating effect of hfa and bidentate organophosphine-functionalized ionic liquid. The ionic liquid can increase the luminescence performance and thermal stability of complexes effectively. Based on the good dissolving ability of the obtained Europium(III) complexes and poly(methylmethacrylate) in dimethylformamide, a flexible and transparent film was constructed via solution casting method, and revealed great potential application value in collapsible optoelectronic devices.

Utilization of Ternary Europium Complex for Organic Electroluminescent Devices and as a Sensitizer to Improve Electroluminescence of Red-Emitting Iridium Complex.

Two new lanthanide complexes [Ln(hfaa)3(Py-Im)] [hfaa = hexafluoroacetylacetone, Py-Im = 2-(2-pyridyl)benzimidazole and Ln = Eu(III) (1) and Tb(III) (2)] were synthesized and characterized. An X-ray crystal structure determination confirms that complex 1 is eight-coordinate with a distorted trigonal dodecahedral geometry. It shows typical vivid red Eu(III) emission in the solid state, in solution, and in a polymer matrix. The observed lifetime (τobs) of complex 1 in the solid state, in dichloromethane (DCM) solution, and in thin films is 833.01, 837.95, and 626.16-715.69 μs, respectively, with a photoluminescence quantum yield QEuL ≈ 33% in DCM solution. Complex 2 displays a yellowish-green emission in the solid state (τobs ≈ 36.99 μs), while a near white-light emission in solution (x; 0.2574: y; 0.3371) and in thin films. Therefore, it is a potential candidate for generating single-component white light-emitting materials for solid-state lighting applications. The kinetic scheme for modeling energy-transfer processes shows that the main donor state for 1 is the ligand triplet state (T1) and that energy transfer occurs to both the 5D1 (56.55%) and 5D0 (40.58%) levels. We fabricated a series of single- and double-layer organic light-emitting devices using complex 1. The luminance of the optimized double-layer electroluminescence (EL) device was 373 cd/m2 with very low turn-on voltage of ∼4.2 V. Complex 1 was further utilized as a sensitizer to improve the EL of a red-emitting iridium complex PQ2Ir(dpm) (PQ = phenylquinoly-N,C2', dpm = dipivaloylmethane). The codoped device achieved a maximum brightness and maximum current efficiency (ηc) of 93 224 cd/m2 and 36.38 cd/A, respectively.

Preparation and Luminescence Properties of Europium(III) Ternary Complex-modified Poplar Wood-based Materials

Inspired by the ultraviolet induced properties of biological materials, we developed fluorescent wood as a new type of functional material which can be applied to anti-counterfeit label technology and wood-emitting artwork. This study discusses the influence of temperature, time, ligand ratio, and reactant concentration on the structure and properties of fluorescent wood with europium(III) ternary complexes. The surface morphology and fluorescent properties of the modified wood were characterized by scanning electron microscopy (SEM) and fluorescence spectrometry. The results showed that a high reaction temperature of 75 oC was beneficial in obtaining stronger fluorescent wood; a reaction time of 8 h exerted a significant influence on fluorescent wood when the reactant concentration of the sample was 0.03 mol/L. In addition, the results of infrared spectroscopy, X-ray photoelectron spectroscopy, and energy-dispersive X-ray analysis showed that modification of wood takes place through the Si-OH groups of the silane coupling agent, which link to the surface of wood. After 120 hours of UV light irradiation, the surface fluorescence intensity of the modified wood can reach 500 arb. units. It can be considered that the modified wood has better anti-ultraviolet aging properties, thereby prolonging the life of poplar.

Fluorescent ternary complexes of some biogenic amines and their metabolites with europium and oxytetracycline for applications in the chemical analysis

New ternary complexes of europium with oxytetracycline possessing the intense fluorescence have been obtained for prospective applications in the high-sensitive detection of biogenic amines and their metabolites in biological fluids. Their stability constants have been determined using the Foster–Hammick–Wardley method based on the fluorescent spectroscopy data. The dependence between structure differences, stability constants of ternary complexes of europium–oxytetracycline with biogenic amines, and their metabolites, and sensitivity of their determination has been established.

A Luminescent pH‐Responsive Ternary Europium(III) Complex of β‐Diketonates and Terpyridine Derivatives as Sensitizing Antennae – Photophysical Aspects, Anion Sensing, and Biological Interactions

The highly luminescent stable Eu3+ complex [Eu(tta)3(naptpy)] [1, tta = 2‐thenoyltrifluoroacetone, naptpy = 2‐{4‐[(2,2′:6′,2′′‐terpyridin)‐4′‐yl]phenyl}‐6‐bromo‐1H benzo[de]isoquinoline‐1,3(2H)‐dione] was designed as a pH‐responsive anion‐sensing probe. Complex 1 was synthesized and characterized by various physicochemical and spectral methods such as FTIR spectroscopy, 1H NMR spectroscopy, ESI‐MS, UV/Vis spectroscopy, and emission spectroscopy. A photosensitization mechanism occurs through two antennae (tta and naptpy) for Eu luminescence by energy transfer to the emissive 5D0 states of the Eu3+ ion through the corresponding excited triplet states of the ligands. Complex 1 displays strong luminescence, remarkable photostability, a long luminescence lifetime (τ = 0.365 ms) in H2O, and no coordinated inner‐sphere water molecules (q < 1). The pH‐dependent study showed that the emission intensity of 1 was quenched or “switched off” upon the displacement of the β‐diketonate antenna owing to the acid sensitivity of the α‐proton of tta and a subsequent ligand‐exchange reaction. The anion sensitivity of the probe was evaluated for a series of anions in aqueous N,N‐dimethylformamide (DMF). In the presence of citrate, F–, and HCO3– ions, the luminescence of 1 was quenched, whereas only minor luminescence changes were observed in the presence of other anions owing to the oxophilicity or stronger binding affinity of the hard oxoanions with the hard Lewis acidic Eu3+ ions. The probe shows efficient DNA (Kb = 6.53 × 104 m–1) and bovine serum albumin (BSA, KBSA = 5.09 × 105 m–1) binding affinities under physiological conditions. The quenching of the luminescence intensity of 1 upon interaction with calf thymus DNA (CT‐DNA) suggests that it could be used for luminescence‐based sensing applications.

Comparison of Luminescent Properties in Solid-State and Polymer Films of Eu(III) Complexes Containing 2-Acylindandione Ligands

The Europium(III) ternary complexes Eu(BID)3(PHEN) and Eu(MBID)3(PHEN) (BID – 2-benzoyl-1,3-indandione, MBID - 2-(4-methylbenzoyl)-1,3-indandione and PHEN – 1,10-Phenantroline) were synthesized, characterized and incorporated into poly methyl methacrylate (PMMA) and poly-N-vinylcarbazole (PVK) matrixes. Emission properties in solid-state and polymer films were investigated through excitation spectra, emission spectra and absolute photoluminescence quantum yields (PLQY). Both complexes in their solid-state and films exhibited red-light luminescence with narrow bands corresponding to Eu(III) ion emission. In solid-state complexes were characterized with PLQY of 6% and 10%, in PVK matrixes quantum yield dropped down to 4%, however, in PMMA films exhibited similar luminescence PLQY than in solid-state.

Luminescence Properties of SiO2@Eu(phen-Si) (sulphoxide) Core-Shell Nanometer Composite

A novel ternary europium complex Eu(Phen-Si)·(H2L)2·(ClO4)3·6H2O was prepared using (phen)-N-(CONH(CH2)3Si(OCH2CH3)3)2 (Phen-Si) as the first ligand and 2-carboxyphenyl carboxymethyl sulphoxide (H2L) as the second ligand. The corresponding different thickness core-shell structure SiO2@Eu(phen-Si)·L nano composites were synthesized, with silica spheres as core, ternary europium complex (Eu(Phen-Si)·(H2L)2·(ClO4)3) as shell. The ternary europium complex has been characterized by element analysis, molar conductivity, and IR spectra. The SiO2@Eu(phen-Si)·L core-shell structure composite was characterized by TEM and IR spectra. Core-shell structure composites exhibited stronger fluorescence properties than that of the ternary europium complex. The emission intensity of the two core-shell composites was 1.79, 3.99 times stronger than the ternary europium complex, respectively. The fluorescence lifetime of the core-shell structure composites were longer than the ternary europium complex.

Photoluminescence of ternary europium complexes based on unsymmetrical diketone

In order to investigate the influence of doping samarium (III) (Sm3+) ions on the photoluminescence properties of ternary europium complexes, Eu1−x Sm x (NPPD)3·(DPQ) and Eu1−x Sm x (NPPD)3·(NPT) (HNPPD, 1-(naphthalen-2-yl)-3-phenylpropane-1,3-dione; DPQ, dipyridobenzoquinone; NPT, 5-nitro-1,10-phenanthroline; x = 0·0, 0·1, 0·3, 0·5, 0·7, 0·9, 1·0) were synthesized by the reaction of lanthanide chloride with ligands in stoichiometry. The obtained complexes were characterized by elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, ultraviolet/visible spectroscopy and luminescence spectroscopy. The study of photoluminescence properties showed intensely red emission due to the 5D0 → 7Fj transitions of the central europium (III) (Eu3+) ions, indicating that the triplet state energy of ligands is suitable for sensitizing the luminescence of europium (III) ions. Furthermore, the emission efficiency varied with doping of samarium (III) ions due to energy transfer from samarium (III) ions to europium (III) ions. The photoluminescene intensity of Eu1−x Sm x (NPPD)3·(DPQ) were obviously higher than those of Eu1−x Sm x (NPPD)3·(NPT). Among all the prepared complexes, Eu0·7Sm0·3(NPPD)3·(DPQ) shows the highest photoluminescene quantum yield, which would have the potential application for organic light-emitting diodes.

EuIII‐Based Nanolayers as Highly Efficient Downshifters for CIGS Solar Cells

We report herein on the use of 13 ternary europium(III) complexes as downshifting (DS) material for copper indium gallium selenide (CIGS) solar cells. Their general formulae are [Eu(β‐Dik)3(NL)x] and [Eu(L)3], in which β‐Dik = 2‐thenoyltrifluoroacetonate, 4,4,4‐trifluoro‐1‐phenyl‐1,3‐butanedione and 4,4,4‐trifluoro‐1‐(2‐naphthyl)‐1,3‐butanedione and NL = diphenyl sulfoxide (x = 2), triphenylphosphine oxide (x = 2), bis[2‐(diphenylphosphino)phenyl] ether (x = 1), 5,6‐epoxy‐5,6‐dihydro‐1,10‐phenanthroline (x = 1) and 2‐(N,N‐diethylanilin‐4‐yl)‐4,6‐bis(3,5‐dimethylpyrazol‐1‐yl)‐1,3,5‐triazine (x = 1) and L = 4‐(4′‐tert‐butylbiphenyl‐4‐yl)‐2,2′‐bipyridine‐6‐carboxylate. Tris(β‐diketonate) ternary EuIII complexes are very good candidates for DS applications, and some of them have shown very promising results when embedded in a host organic polymer matrix typically used for solar cell encapsulations. Herein we report a new method for the direct deposition of luminescent nanolayer films on CIGS solar cells. Highly luminescent nano‐ and microlayer films with a thickness in the range of 150 nm to 10 µm have been obtained and characterized by optical microscopy, profilometry, spectrofluorimetry and external quantum efficiency (EQE) measurements. The efficient conversion of incident photons into red light was observed for films with a thickness of 400–600 nm, leading to a significant improvement in the EQE and short‐circuit current density (Jsc) in the UV region up to 0.81 mA/cm2. The absolute conversion efficiency increased by up to 0.8 %. The nanofilms, with the exception of those containing naphthyl derivatives, were found to be photostable and therefore represent a competitive alternative to doped polymer encapsulants.

Versatile Luminescent Europium(III)-β-Diketonate-imidazo-bipyridyl Complexes Intended for White LEDs: A Detailed Photophysical and Theoretical Study.

Three ancillary ligands based on imidazo-bipyridyl with phenyl (Ph), naphthyl (Np), and triphenylamine (TPA) substitution were synthesized and secondhand to formulate the consistent europium(III) ternary complexes using thenoyltrifluoroacetone as an anionic ligand. The complete investigation of spectroscopic, photophysical, and electrochemical properties was carried out. The attained results for all the ancillary ligands and their corresponding Eu complexes were compared with one another. All the Eu complexes reveal a broad excitation band ranging from the near-UV to blue region, along with high intense emission and apposite color purity. To further understand the ligand-to-metal energy transfer (ET) process, the geometry of the ligand was optimized and the energy level location (singlet and triplet) was calculated by using DFT and TD-DFT calculations. On the basis of the theoretical calculation, the ET mechanism was proposed. From PL emission spectra in the solid state, complete ET occurs from Ph, Np based ancillary ligands to the Eu3+ ion, which yields a pure red emission, whereas the TPA functionalized based Eu complex shows incomplete ET. Fortunately, white emission was observed in the TPA based Eu complex in the solid state. The white LED was fabricated by using a white emitting complex integrated with 395 nm emitted LED (InGaN) chips under 20 mA forward-bias current. The excitation source from LED was fully observed by the complex shown for 3Eu and showed yellowish emission in different concentrations (the similar observation also reflected in solid). However, in the case of 1Eu and 2Eu complexes, they showed close to white emission. The Commission International de I'Eclairage (CIE) chromaticity coordinates are close to the National Television Standard Committee standard value for white emission, and in addition, the complex 3Eu coated with the blue LED chip (460 nm) by PMMA (1:10) showed bright white emission with CIE x, y values of 0.30, 0.33, respectively.

Synthesis, photoluminescence features with intramolecular energy transfer and Judd–Ofelt analysis of highly efficient europium(III) complexes

The luminescent binary and ternary europium(III) complexes were prepared by employing ethyl-(3-fluorobenzoyl) acetate (m-EFBA) as primary ligand and neocuproine (neo), bathophenanthroline (batho), 1,10-phenanthroline (phen) and 2,2-bipyridyl (bipy) as secondary ligands. The synthesized complexes Eu(m-EFBA)3·(H2O)2 (C1), Eu(m-EFBA)3·neo (C2), Eu(m-EFBA)3·batho (C3), Eu(m-EFBA)3·phen (C4), Eu(m-EFBA)3·bipy (C5) were characterized by the means of elemental analysis (C, H and N), nuclear magnetic resonance spectroscopy (1H-NMR), infrared spectroscopy (IR), thermogravimetric analysis (TG/DTG), UV–visible and photoluminescence (PL) spectroscopy. The photoluminescence spectra of complexes exhibit the characteristic emission band at 613 nm assigned to hypersensitive 5D0 → 7F2 transition, responsible for the red color emission of complexes. The higher photoluminescence intensity of ternary europium(III) complexes C2–C5 as compared to binary complex C1, suggest that ancillary ligands neo, batho, phen and bipy enhance the process of sensitization from ligand (m-EFBA) to europium(III) ion. The luminescence decay time and quantum efficiencies of the complexes were determined to estimate the efficiency of energy transfer from ligand to metal ion. In addition, the Judd–Ofelt intensity parameters (Ω2, Ω4) were calculated from the emission intensities of 5D0 → 7F2 and 5D0 → 7F4 transitions of europium(III) ion respectively. The intramolecular energy transfer mechanism of the complexes were also investigated and results indicate that the ligand (m-EFBA) and ancillary ligands effectively transfer the energy to that of Eu(III) ion.

Enhancement of Copper Indium Gallium Selenide Solar Cells Using Europium Complex as Photon Downshifter

This work reports on the use of a ternary europium (III) complex as downshifting (DS) material for copper indium gallium selenide (CIGS) solar cells, [Eu(tta)3(tppo)2] (tta = 2‐thenoyltrifluoroacetonate and tppo = triphenylphosphine oxide). It is synthesized by one‐pot reaction and embedded into poly(ethylene‐co‐vinyl acetate) (EVA), poly(methyl methacrylate) (PMMA), and poly(vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate) (PVB) matrices. Their photophysical properties are investigated and compared with the complex alone. No significant variations in transmittance, emission, excitation spectra, and quantum yield are detected between [Eu(tta)3(tppo)2] alone and embedded into EVA, PMMA, and PVB. CIGS solar cells are encapsulated using these compounds, leading to an improvement of the external quantum efficiency (EQE) mostly in UV region. The EQE at 360 nm increases up to 56% compared to 14% without the encapsulant. The luminescent downshifting (LDS) material is responsible for an increase in the short‐circuit current (Jsc) calculated from the EQE in the 300–420 nm region, by 0.55 mA cm−2 compared to the value of 0.59 mA cm−2 obtained from theoretical prediction. In the best case, an increase of the CIGS solar cell conversion efficiency by 0.8% absolute is observed thanks to the LDS material.

Zirconia-based luminescent organic-inorganic hybrid materials with ternary europium (III) complexes bonded

In this work, a novel red-emitting organic-inorganic hybrid material with europium (III) lanthanide β-diketonate complexes linked to a zirconia was reported, which was realized by adduct formation with zirconia-tethered terpyridine moieties. Luminescence enhancement of the hybrid material has been observed compared with pure Eu(tta)3·2H2O. Transparent and strongly luminescent thin films based on PMMA were also prepared at room temperature, which are highly luminescent under UV-light irradiation and possess a promising prospect in the area of optics.

Chemical Partition of the Radiative Decay Rate of Luminescence of Europium Complexes

The spontaneous emission coefficient, Arad, a global molecular property, is one of the most important quantities related to the luminescence of complexes of lanthanide ions. In this work, by suitable algebraic transformations of the matrices involved, we introduce a partition that allows us to compute, for the first time, the individual effects of each ligand on Arad, a property of the molecule as a whole. Such a chemical partition thus opens possibilities for the comprehension of the role of each of the ligands and their interactions on the luminescence of europium coordination compounds. As an example, we applied the chemical partition to the case of repeating non-ionic ligand ternary complexes of europium(III) with DBM, TTA, and BTFA, showing that it allowed us to correctly order, in an a priori manner, the non-obvious pair combinations of non-ionic ligands that led to mixed-ligand compounds with larger values of Arad.

Substantial luminescence enhancement in ternary europium complexes by coordination of different ionic ligands

We demonstrate in a general and comprehensive manner that a substantial enhancement of luminescence in europium complexes can be achieved by increasing ionic ligand diversity. The measured boosts in quantum efficiency ranged from 100% to 543%.

Faster Synthesis of Beta-Diketonate Ternary Europium Complexes: Elapsed Times & Reaction Yields.

β-diketonates are customary bidentate ligands in highly luminescent ternary europium complexes, such as Eu(β-diketonate)3(L)2, where L stands for a nonionic ligand. Usually, the syntheses of these complexes start by adding, to an europium salt such as EuCl3(H2O)6, three equivalents of β-diketonate ligands to form the complexes Eu(β-diketonate)3(H2O)2. The nonionic ligands are subsequently added to form the target complexes Eu(β-diketonate)3(L)2. However, the Eu(β-diketonate)3(H2O)2 intermediates are frequently both difficult and slow to purify by recrystallization, a step which usually takes a long time, varying from days to several weeks, depending on the chosen β-diketonate. In this article, we advance a novel synthetic technique which does not use Eu(β-diketonate)3(H2O)2 as an intermediate. Instead, we start by adding 4 equivalents of a monodentate nonionic ligand L straight to EuCl3(H2O)6 to form a new intermediate: EuCl3(L)4(H2O)n, with n being either 3 or 4. The advantage is that these intermediates can now be easily, quickly, and efficiently purified. The β-diketonates are then carefully added to this intermediate to form the target complexes Eu(β-diketonate)3(L)2. For the cases studied, the 20-day average elapsed time reduced to 10 days for the faster synthesis, together with an improvement in the overall yield from 42% to 69%.

Synthesis and photoluminescent behavior of Eu(III) complexes with 4,4,4-trifluoro-1-(6-methoxy-naphthalen-2-yl)-butane-1,3-dione

The fluorinated β-diketone ligand, 4,4,4-trifluoro-1-(6-methoxy- naphthalen-2-yl)-butane-1,3-dione (HL), and its ternary europium (III) complexes using water (H2O), 2,2-dipyridine (Bipy), 1,10-phenanthroline (Phen) and 4′-phenyl-terpyridine (Phterpy) as the secondary ligand were synthesized and characterized by elemental analysis, FT-IR, 1H NMR, UV–vis absorption, ESI–MS and fluorescence spectroscopic techniques. All these europium complexes exhibited the characteristic emission bands that arise from the 5D0→7FJ (J=0–4) transitions of the europium ion in solid state. Based on their emission spectra and lifetimes, the Judd–Ofelt intensity parameters (Ω2 and Ω4), the radiative decay rate Arad, the nonradiative rates Anrad, and the quantum efficiency (η) were determined and compared. The ternary complexes, EuL3·Bipy, EuL3·Phen and EuL3·Phterpy, exhibited much higher quantum efficiencies and lifetime values, which can be attributed to the displacement of water molecules from the coordination sphere by the heterocyclic nitrogen donors. Especially, the complex EuL3·Phen exhibited the longest lifetime τ (0.704ms) and the highest luminescence quantum efficiency η (47.9%) among these complexes. Meanwhile, complexes EuL3·Bipy, EuL3·Phen and EuL3·Phterpy also displayed higher Ω2 values than the complex EuL3·2H2O, indicating their hypersensitive character of the 5D0→7F2 transition and a highly polarizable chemical environment around the europium(III) ion.

Synthesis, characterization, enhanced photoluminescence and biological activity of Eu(III) complexes with organic ligands

Six new europium(III) ternary complexes were synthesized with β-hydroxyketone, 2-hydroxy-4,6-dimethoxyacetophenone (HDAP) and 1,10-phenanthroline (phen) or 5,6-dimethyl-1,10-phenanthroline (dmph) or bathophenanthroline (bath) or 2,2-bipyridine (bipy) or 2,2-biquinoline (biq) or neocuproin (neo) as secondary ligand. The ligand and synthesized complexes, Eu(HDAP)3.phen(1), Eu(HDAP)3.dmph(2), Eu(HDAP)3.bath(3), Eu(HDAP)3.bipy(4), Eu(HDAP)3.biq(5) and Eu(HDAP)3.neo(6) were characterized by elemental analysis, infrared spectra, 1H-NMR spectra and powder XRD measurement. The photoluminescence behaviours of these complexes were checked by the excitation and emission spectra. The life time (τ) and quantum efficiency (η) of the complexes were determined based on the emission spectra and luminescence decay curve in solid state. The introduction of secondary ligands results in longer life time (τ) and higher quantum efficiency (η) in europium ternary complexes due to extended π-conjugation. All these europium ternary complexes exhibited highest excitation intensity at 395 nm, which perfectly matched with the emission spectra of commercial 395 nm emitting InGaN chips. These complexes emitted bright red luminescence (616 nm) corresponding to electric dipole transition 5D0 → 7F2 of Eu3+ ion, on exposure to UV source at 395 nm. Thus these complexes might be promising candidates for bright red light-emitting diodes used in display devices. In addition, in vitro antimicrobial and in vitro antioxidant properties of these complexes are reported. The results revealed that all these ternary complexes are excellent antimicrobial agents while are moderate antioxidant agent, except complex (3) which showed very high antioxidant power.

Transparent and luminescent ionogels composed of Eu(3+)-coordinated ionic liquids and poly(methyl methacrylate).

We report here on transparent and luminescent ionogels that consist of ionic ternary europium (III) complexes and the inexpensive non-toxic compound, poly(methyl methacrylate) (PMMA) and that were formed by dissolving these complexes in methacrylate (MMA) monomers followed by in situ polymerization. The resulting ionogels show a bright red emission under near-UV light irradiation. Luminescence data confirm the energy transfer from terpyridine-functionalized ionic liquid to Eu(3+) ions.

Enhanced optoelectronics properties of europium(III) complexes with β-diketone and nitrogen heterocyclic ligands

Preparation and photoluminescence behavior of six new europium complexes with β-diketone 1-(2-hydroxy phenyl)-3-phenylpropane-1,3-dione (HPPP) and bathophenanthroline (batho), 2,2′-bipyridyl (bipy), 2,2′-biquinoline (biq), neocuproin (neo) and 1,10-phenanthroline (phen) are reported in solid state. The ligand (HPPP) and complexes Eu(HPPP)3·H2O (1), Eu(HPPP)3·phen (2), Eu(HPPP)3·batho (3), Eu(HPPP)3·bipy (4), Eu(HPPP)3·biq (5) and Eu(HPPP)3·neo (6) were characterized by means of elemental analysis, infrared spectroscopy, proton nuclear magnetic resonance (1H-NMR). The optical properties, thermal stability and crystalline nature were investigated by photoluminescence spectroscopy, thermogravimetric analysis and XRD respectively. The emission spectra show narrow intense emission band of central europium (III) metal ion that arise from the high intense 5D0 → 7F0 transition. The introduction of ancillary ligands like batho, bipy, biq, neo, phen enlarged the π-conjugation system in complexes as a result higher luminescence intensity, longer life time (τ) and higher quantum efficiency (η) observed in europium ternary complexes in comparison to Eu(HPPP)3·H2O (1). Based on the emission spectra, the luminescence decay curve was measured which indicated that the transfer of energy from HPPP ligand to the europium metal is more efficient in complexes 2–6 than complex 1.