Density functional theory investigation of Eu(III) complexes with beta-diketonates and phosphine oxides: Model complexes of fluorescence compounds for ultraviolet LED devices
ABSTRACT The density functional theory was employed to investigate Eu(III) complexes with three beta-diketonates and two phosphine oxides (complex M1: Eu(bdk)3(TPPO)2, complex M2: Eu(bdk)3(TMPO)2, and complex M3: Eu(bdk)3(TPPO)(TMPO)) deemed to be the model complexes of the fluorescence compounds for the ultraviolet LED devices we have recently developed. For each complex, two minimum energy points corresponding to two different optimized geometries (structures A and B) have been found, and the difference of the energy between two minimum energy points is found to be quite small (less than 1 kcal/mol). Vertical excitation energies and oscillator strengths for each complex at two optimized geometries have been obtained by the time-dependent density functional theory, and the character of the excited states has been investigated. For complex M3, the absorption edge is red-shifted, and the oscillator strengths are relatively large. The efficiency of intersystem crossing and energy transfer from the triplet excited state to the Eu(III) ion is considered by calculating DeltaE(ISC) (the energy difference between the first singlet excited state and the first triplet excited state) and DeltaE(ET) (the difference between the excitation energy of the complex for the first triplet excited state and the emission energy of the Eu(III) ion for 5D to 7F).
- [Show abstract] [Hide abstract]
ABSTRACT: Reaction of a newly designed amide type ligand, benzyl-N,N-bis[(2′-benzylaminofomyl)phenoxyl)ethyl]-amine (L) with lanthanide nitrates and picrates has produced two isostructural series of lanthanide coordination compounds, [Ln2L2(NO3)6(DMF)2]n [series 1, monoclinic P21/c, Ln = Pr (1), Sm (2), Eu (3), Tb (4), and Dy (5)] and [LnL(pic)3(CH3CH2OH)]n [series 2, triclinic P, Ln = Nd (6), Eu (7), Tb (8), and Er (9)]. Series 1 have zero-dimensional (0D) dinuclear rectangular macrocycle architectures, while series 2 exhibit one-dimensional (1D) chain patterns. Meanwhile, the two series of structures are further connected through weak intermolecular hydrogen bonds to yield three-dimensional (3D) supramolecular structures. The variations from zero- to one-dimensional coordination structures are attributed to different steric confinement of the nitrate and picrate anions. In addition, we have studied the luminescent properties of the nitrate and picrate complexes, and found that the picrate complexes give very weak luminescence due to coordinated ethanol molecules existing in complexes, which decrease the luminescence. So, herein the luminescent properties of only the Sm (2), Eu (3), Tb (4), and Dy (5) nitrate complexes are investigated in detail.CrystEngComm 07/2012; 14(15):4989-4996. DOI:10.1039/C2CE25210D · 3.86 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: A novel b-diketone ligand, 4,4,5,5,5-pentafluoro-3-hydroxy-1-(phenanthren-3-yl)pent-2-en-1-one (Hpfppd), which contains a polyfluorinated alkyl group, as well as a conjugated phenanthrene unit, has been synthesized and utilized for the construction of two new europium coordination compounds [Eu(pfppd) 3 (H 2 O) 2 ] 1 and [Eu(pfppd) 3 (tpy)] 2 (where tpy ¼ 2,2 0 :6,6 00 -terpyridine). The designed europium compounds were well characterized and their solid-state photoluminescence (PL) properties were examined. Notably, the introduction of a highly conjugated phenanthrene moiety into the 3-position of the b-diketonate ligand remarkably extends the excitation window of the corresponding Eu 3+ complexes towards the visible region (up to 500 nm). The PL study demonstrated that the replacement of high-energy oscillators O–H (water molecules) in 1 with an ancillary ligand terpyridine leads to an impressive enhancement in both overall quantum yield (from 31 to 75%) and 5 D 0 lifetime (from 0.51 to 1.04 ms) values. To the best of our knowledge, the solid-state quantum yield of 2 is found to be the highest so far reported in the literature under blue-light excitation (415 nm). To gain a wider applicability and also to overcome the poor thermal, photochemical and mechanical stabilities of Eu 3+ –b-diketonate luminophores, in the present study, a nanocomposite material (1@oxMWCNTs) has been fabricated by coupling Eu 3+ complex 1 onto an oxidized multi-walled carbon nanotube (oxMWCNTs) scaffold. Characterization of the new luminescent nanocomposite material was accomplished by means of FT-IR, FT-Raman, XPS, TGA, SEM, TEM, AFM, EDAX and photoluminescence spectroscopic techniques. The designed nanocomposites 1@oxMWCNTs exhibit high thermal stability and luminescence efficiency. Furthermore, the high dispersibility of luminescent 1@oxMWCNTs in a polymer matrix (PMMA) and intense red emissions make it a promising luminophore for applications in polymer optical fibers as well as in light emitting devices.
- [Show abstract] [Hide abstract]
ABSTRACT: A novel amide type ligand benzyl-N,N-bis[(2'-furfurylaminoformyl)phenoxyl)ethyl]-amine (L) has been designed and applied for the self-assembly generation of homodinuclear lanthanide coordination compounds [Ln2(μ2-L)2(NO3)6(EtOH)2] [Ln = Eu (1), Tb (2), and Gd (3)] and a heterodinuclear derivative [EuTb(μ2-L)2(NO3)6(EtOH)2] (4). All the complexes have been characterized by the X-ray single-crystal diffraction analyses. They are isostructural, crystallize in a monoclinic space group P21/c, and form [2 + 2] rectangular macrocycle structures. Compound 4 is the first example of a [2 + 2] rectangular macrocycle heterodinuclear EuTb complex assembled from an amide type ligand. In 4, the discrete 0D dimeric [EuTb(μ2-L)2(NO3)6(EtOH)2] units are extended, via the multiple N-H···O hydrogen bonds, into a 2D supramolecular network that has been topologically classified as a uninodal 4-connected underlying net with the sql [Shubnikov tetragonal plane net] topology. The triplet state ((3)ππ*) of L studied by the Gd(III) complex 3 demonstrated that the ligand beautifully populates Tb(III) emission (Φ = 52%), whereas the corresponding Eu(III) derivative 1 shows weak luminescence efficiency (Φ = 0.7%) because the triplet state of L has a poor match with (5)D1 energy level of Eu(III). Furthermore, the photoluminescent properties of heterodinuclear complex 4 have been compared with those of the analogous homodinuclear compounds. The quantum yield and lifetime measurements prove that energy transfer from Tb(III) to Eu(III) is being achieved, namely, that the Tb(III) center is also acting to sensitize the Eu(III) and enhancing Eu(III) emission in 4.Inorganic Chemistry 01/2014; 53(2). DOI:10.1021/ic402338q · 4.79 Impact Factor