Search

[Display omitted] A new cubane cluster [Cu 4 I 4 (AsAn 3) 4 ] was synthesized in 82% yield by the reaction of tris(p -anisyl)arsine (AsAn 3) with CuI. At ambient temperature, this cluster exhibits bright yellow-green phosphorescence (λ max = 546 nm) with the quantum yield of 35% and 4.1 μs decay time. [ABSTRACT FROM AUTHOR]

[Display omitted] 1D coordination polymers [Cu 2 I 2 (AsPh 3) 2 (L)] n (L = 4,4 ' -bi-pyridine, pyrazine) were synthesized via the reaction of CuI with AsPh 3 and N , N' -ditopic co-ligand s L. At ambient temperature, these polymers exhibit short-lived (2.3–3.2 μs) thermally activated delayed fluorescence (TADF) with max at 530 nm (L = 4,4 ' -bipyridine) and 605 nm (L = pyrazine) and quantum efficiency up to 45%. [ABSTRACT FROM AUTHOR]

[Display omitted] Reactions of zinc nitrate with 2-iodobenzoic acid (2-IBA) and different pyridines result in binuclear Znii carboxylate complexes [Zn 2 (2-IBA) 4 L 2 ], where L = Py, 3-MePy and 3,5-Me 2 Py, while in the case of 2,4,6-Me 3 Py, trinuclear (2,4,6-Me 3 PyH) 2 [Zn 3 (2-IBA) 6 (OH) 2 ] is formed. [ABSTRACT FROM AUTHOR]

A series of yellow cuboid diamonds from alluvial placers in the north-eastern Siberian platform have been examined with Fourier-transform infrared (FTIR) absorption spectroscopy, photoluminescence (PL) and electron paramagnetic resonance (EPR). All crystals having characteristic FTIR spectra with predominantly C and A centres belong to mixed type IaA/Ib with small total nitrogen content (up to 330 ppm). PL is characterized by many bands with two bands related to the NV0 and NV-centres common to all the samples. The FTIR spectra are also characterized by deformation-induced 'amber' centers. Some of the yellow diamonds studied show new bands at 4272, 4548, and 5960 cm-1 instead of the bands at 4060 and 4170 cm-1 common for 'amber' centres. An EPR study has revealed the presence of OK1 centres associated with titanium impurity. The plastic deformation of the studied diamonds is expressed as a 'tatami' strain pattern in the features of their internal structure. [ABSTRACT FROM AUTHOR]

Mononuclear zinc(II) and cadmium(II) complexes, ZnLCl2 (1), CdLCl2 (2), ZnL1Cl2·2H2O (3), and CdL1Cl2·2H2O (4), with chiral ligands containing a 2,2′-bipyridine moiety and natural terpene (+)-limonene (L) or (+)-3-carene (L1) moieties were synthesized. In these complexes the L and L1 ligands are shown to coordinate Zn2+ and Cd2+ ions through the 2,2′-bipyridine moiety. The acetamide group of the ligands interacts with M2+ ions by forming N⋯M2+ and C＝O⋯M2+ contacts and N–H⋯Cl hydrogen bonds with coordinated Cl− ions. In solutions the complexes have several conformers differing by the degree of the turn of the acetamide moiety relative to the ligand core and the type of its interaction with the coordination core. The ligands and complexes exhibit luminescence with the quantum yield increasing in the order: ligand < cadmium(II) complex < zinc(II) complex. The complexes 3 and 4 demostrate excitation wavelength independent single-channel fluorescence. As opposed to 3 and 4, the complexes 1 and 2 demonstrate excitation wavelength dependent emission with nanosecond and microsecond lifetimes of the excited states. According to our TD-DFT calculations, an interplay of ligand centered and halide to ligand transitions facilitates two deactivation channels in 1 and 2: S1–S0 and T1–S0. [ABSTRACT FROM AUTHOR]

In the recent decade, various potential applications of the luminescence of nanosized ZrO 2 :Eu3+ have been demonstrated. However, the particle size effect on the luminescence properties of ZrO 2 :Eu3+ still requires intensive investigation. To this end, a series of tetragonal ZrO 2 :Eu3+ nanopowders with the europium concentration of 4 wt% and particle size of 3.0 ± 0.7 to 12.0 ± 4.8 nm was synthesized by laser vaporization. It was shown that the dominant role in the optical properties of ZrO 2 :Eu3+ nanoparticles belongs to OH groups, oxygen vacancies, and Eu3+ ions. It was found that a decrease in the particle size is accompanied by a significant increase in the emission intensity in the region of ∼440 nm. Based on the results of thermal analysis, IR and UV–vis DR spectroscopies, it was concluded that this luminescence is due to the emission of adsorbed OH groups. At the same time, a decrease in the number of vacancies with a decrease in the particle size leads to a change in the absolute quantum yield QY from ∼7 to 3.5%. In addition, despite the overall decrease in the intensity of the red luminescence of Eu3+, a decrease in the particle size leads to the appearance and increase in the emission intensity of the surface Eu3+. Thus, changing the particle size from 12.0 to 3.0 nm leads to a twofold decrease in the luminescence efficiency of ZrO 2 :Eu3+ and a shift in the color of its emission from pink-red (0.36, 0.26) to blue (0.19, 0.10). The results obtained are expected to be useful for further optimization of the luminescence properties of nanosized ZrO 2 :Eu3+ in numerous applications. [ABSTRACT FROM AUTHOR]

Reactions between 1,2-bis(pyridinium)ethane bromide ((BPE)Br 2 ) and [BiCl 6 ] 3− /[BiBr 6 ] 3− in HCl or HBr results in isostructural binuclear complexes (BPE) 2 [Bi 2 X 10 ] (X = Cl ( 1 ) and Br ( 2 )) which were characterized by X-ray diffractometry, IR and Raman spectroscopy. Both complexes manifest orange-red luminescence in solid state. [ABSTRACT FROM AUTHOR]

Nanosized zirconia doped with europium (ZrO 2 :xEu3+, x = 0.07–9.95 wt%) and represented by weakly agglomerated spherical particles with the size of 9.7 ± 4.3 nm was synthesized by laser vaporization in an argon atmosphere using a cw CO 2 laser. The specific surface area of the obtained nanoparticles is 92 ± 4 m2/g. The XRD study with Rietveld refinement revealed that the phase composition of the samples is represented predominantly by the tetragonal phase with a small content of monoclinic phase. At the concentrations above 4.57 wt%, stabilization of the cubic phase also occurs. The dependence of the PL intensity, PL lifetime, absolute quantum yield, and color coordinates of ZrO 2 :Eu3+ on the Eu concentration was studied. It was shown that the maximum PL intensity is observed at the concentration of 8.39 wt%. The Eu3+ lifetime decreases from 5.60 to 3.21 ms with a growth of the Eu content. Aging of the samples due to the adsorption of OH groups was revealed. The absolute quantum yield QY was measured for the 575–725 nm region corresponding to the luminescence of europium, and for the 410–725 nm region, which also includes the emission of oxygen vacancies. The QY was found to increase with the growth of Eu concentration, reaching the highest values for ZrO 2 :8.39Eu3+; it is equal to 1.6 and 17.6% for 575–725 and 410–725 nm regions, respectively. It was shown that variation of the Eu3+ concentration and excitation wavelength makes it possible to obtain color coordinates with red and close to white light. Along with the high QY for the region of 410–725 nm, this indicates that it is more promising to use ZrO 2 :Eu3+ as the white phosphor rather than the red one. [ABSTRACT FROM AUTHOR]

Reactions between Zn(II) dihalides and 2-halogen-substituted pyridines 2-XPy result in a series of heteroleptic molecular complexes [(2-XPy)2ZnY2] (Y = Cl, X = Cl (1), Br (2), I (3); Y = Br, X = Cl (4), Br (5), I (6), Y = I, X = Cl (7), Br (8), and I (9)). Moreover, 1–7 are isostructural (triclinic), while 8 and 9 are monoclinic. In all cases, halogen bonding plays an important role in formation of crystal packing. Moreover, 1–9 demonstrate luminescence in asolid state; for the best emitting complexes, quantum yield (QY) exceeds 21%. [ABSTRACT FROM AUTHOR]

The coordination behavior of tris(2-pyridyl)arsine (Py3As) has been studied for the first time on the example of the reactions with CuI, CuBr and AgClO4. When treated with CuI in CH2Cl2 medium, Py3As unexpectedly affords the scorpionate complex [Cu(Py3As)I]∙CH2Cl2 only, while this reaction in MeCN selectively leads to the dimer [Cu2(Py3As)2I2]. At the same time, the interaction of CuBr with Py3As exclusively gives the dimer [Cu2(Py3As)2Br2]. It is interesting to note that the scorpionate [Cu(Py3As)I]∙CH2Cl2, upon fuming with a MeCN vapor (r.t., 1 h), undergoes quantitative dimerization into the dimer [Cu2(Py3As)2I2]. The reaction of Py3As with AgClO4 produces complex [Ag@Ag4(Py3As)4](CIO4)5 featuring a Ag-centered Ag4 tetrahedral kernel. At ambient temperature, the obtained Cu(I) complexes exhibit an unusually short-lived photoluminescence, which can be tentatively assigned to the thermally activated delayed fluorescence of (M + X) LCT type (M = Cu, L = Py3As; X = halogen). For the title Ag(I) complexes, QTAIM calculations reveal the pronounced argentophilic interactions for all short Ag∙∙∙Ag contacts (3.209–3.313 Å). [ABSTRACT FROM AUTHOR]

Four new coordination polymers based on Ln3+ and 2,5-diiodoterephthalates (2,5-I-bdc) {[Ln 2 (2,5-I-bdc) 3 (DMF) 4 ]} —were prepared and characterized. Their luminescent properties were compared with other Ln3+ 2,5,-I-bdc complexes; it was shown that these compounds can be used as highly effective sensors on chloro- and nitrobenzene with detection limits of 0.22 mM and 0.16 mM, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

The impact of isomerism of pyrimidine-based ligands and their rhodium(III) complexes with regard to their structures and properties was investigated. Two isomeric ligands, 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2,5-diphenylpyrimidine (HL2,5) and 4-(3,5-dimethyl-1H-pyrazol-1-yl)-2,6-diphenylpyrimidine (HL2,6), were synthesized. The ligands differ by the degree of steric bulk: the molecular structure of HL2,5 is more distorted due to presence of pyrazolyl and phenyl groups in the neighbouring positions 4 and 5 of the pyrimidine ring. The complexation of HL2,5 and HL2,6 with RhCl3 leads to the sp2 C–H bond activation, resulting in the isolation of two complexes, [RhL2,5(Solv)Cl2]·nEtOH and [RhL2,6(Solv)Cl2]·nEtOH (Solv = H2O, EtOH), with the deprotonated forms of the pyrazolylpyrimidine molecules which coordinate the Rh3+ ion as N^N^C-tridentate ligands. According to DFT modelling, the mechanism of the deprotonation involves (i) the C–H bond breaking in the 2-phenyl group followed by the coordination of the C atom to the Rh atom, (ii) the protonation of coordinated chlorido ligand, (iii) the ejection of the HCl molecule and (iv) the coordination of the H2O molecule. The ligand isomerism has an impact on emission properties and cytotoxicity of the complexes. Although the excited states of the complexes effectively deactivate through S0/T1 and S0/S1 crossings associated with the cleavage of the weak H2O ligands upon excitation, the [RhL2,5(Solv)Cl2]·nEtOH complex appeared to be emissive in the solid state, while [RhL2,6(Solv)Cl2]·nEtOH is non-emissive at all. The complexes show significant cytotoxic activity against cancerous HepG2 and Hep2 cell lines, with the [RhL2,6(Solv)Cl2]·nEtOH complex being more active than its isomer [RhL2,5(Solv)Cl2]·nEtOH. On the other hand, noticeable cytotoxicity of the latter against HepG2 is supplemented by its non-toxicity against non-cancerous MRC-5 cells. [ABSTRACT FROM AUTHOR]

Rare‐earth element‐free materials that exhibit strong room temperature phosphorescence (RTP) and X‐ray scintillation properties are gaining global interest incessantly in the recent years. This work reports a series of easily synthesizable cubane Cu4I4‐triarsenic clusters [Cu4I4(R3As)3L] (L = none or nitrile), that exhibit a strong yellow‐green RTP with quantum efficiencies up to 100% and short decay times (4.4–4.9 µs). The title cluster complexes display X‐ray scintillation properties with a record ultralow detection limit (18.1 nGy s−1) and a perfectly linear dose rate response within a remarkably wide dose rate window (0–640 µGyair s−1). The cluster [Cu4I4(Ph3As)3] is highlighted as an efficient phosphor for UV‐pumped white and yellow LED devices, demonstrating an excellent white spectrum with a CIE index of (0.32,0.33) and bright yellow emission, respectively. These results may stimulate the future efforts in designing highly efficient arsenic‐based RTP materials and enriching the Cu4I4 cluster family. [ABSTRACT FROM AUTHOR]

Heteroleptic Zn(II) 3,5-iodosalicylate (DISA) complexes [Py 2 ZnDISA 2 ] (Py = substituted pyridine) were prepared and characterized. All complexes demonstrate luminescence in blue region with quantum yields varying in 1.45–2.6% range. • Heteroleptic 3,5-diiodosalicylate complexes of Zn(II) • Halogen bonding in solid state. • Weak blue luminescence. Heteroleptic Zn(II) 3,5-iodosalicylate (DISA) complexes of general formula [Py 2 ZnDISA 2 ] (Py = 3-methyl (1), 4-methyl (2), 3,5-dimethyl (3), 3,4-dimethyl (4) and 3-bromopyridine (5), respectively) were prepared and characterized by X-ray diffractometry and thermogravimetric analysis. All complexes demonstrate luminescence in blue region with quantum yields varying in 1.45–2.6% range. [ABSTRACT FROM AUTHOR]

A series of red-emissive {Cu4I6} clusters have been synthesized from alkyl-tris(2-pyridyl)phosphonium halides, [R-PPy3]Hal, and CuI. The size of the alkyl substituent (R) has a dramatic impact on the structure of the clusters assembled. [Me-PPy3]I salt reacts with CuI (1 : 2) to give the ionic [Cu(Me-PPy3)I]2Cu2I4 complex consisting of the scorpionate [Cu(N,N′,N′′-Me-PPy3)I]+ cation. Under similar conditions, [Pr-PPy3]I forms the zwitterionic [Cu4I6(Pr-TPP)2] complex containing an unusual stepwise [Cu4I6] cluster core. The use of [Bu-PPy3]I or [Bn-PPy3]I in this reaction leads to zwitterionic [Cu4I6(R-TPP)2] complexes, in which a linear-shaped [Cu4I6] module appears. Photophysical studies supported by TD-DFT computations have revealed that the title complexes in the solid state at 298 K exhibit a red photoluminescence (λemmax = 620–650 nm) with short lifetimes (0.04–2.10 μs), which are assigned to the thermally activated delayed fluorescence (TADF) mixed with the cluster centered (3CC) phosphorescence. The compounds synthesized are the first red-emitting representatives of the recently discovered family of zwitterionic CuI-based complexes (so-called “AIO” structures). [ABSTRACT FROM AUTHOR]

Tris(2-pyridyl)phosphine oxide reacts with CuSCN to form a variety of luminescent complexes, depending on the specified metal-to-ligand ratio and the solvent used, viz. mononuclear [Cu(N,N′,N′′-Py3P=O)(NCS)], dinuclear (N,N′-Py3P=O)Cu(SCNNCS)Cu[(N,N′-Py3P=O)], their co-crystal (2 : 1, correspondingly) and trinuclear {Cu(NCS)[SCNCu(N,N′,N′′-Py3P=O)]2}. In the solid state, these complexes feature red-orange emission upon UV photoexcitation. The reaction of tris(2-pyridyl)phosphine with CuSCN quantitatively produces an almost insoluble coordination polymer, [Cu(Py3P)NCS]n, which exhibits bright green emission. The synthesized compounds are the first members of the hitherto unknown family of Cu(i) thiocyanate complexes supported by tripodal ligands. [ABSTRACT FROM AUTHOR]

Five new coordination polymers based on Ln3+ and 2,5-diiodoterephthalates (2,5-I-bdc)— {[La2(2,5-I-bdc)3(DMF)4]}·2DMF (1) and {[Ln2(2,5-I-bdc)3(DMF)4]} (Ln = La (2), Nd (3), Sm (4) and Eu (5))—were prepared and characterized by single crystal and powder X-ray diffractometry. Luminescent behavior was examined (the highest quantum yield is 4.5%); thermal stability was examined using thermogravimetric analysis. [ABSTRACT FROM AUTHOR]

A series of Ag(I), Au(I), Ag(I)-Au(I) and Cu(I)-Au(I) complexes has been synthesized using tris(6-methyl-2-pyridyl)phosphine as an efficient P , N , N ′, N ″ - bridging ligand. Room temperature phosphorescence has been revealed for the obtained compounds. [Display omitted] Tris(6-methyl-2-pyridyl)phosphine (L) has been highlighted as a promising multidentate ligand for design of original clusters based on group 11 metals. The interaction of this ligand with Au(tht)Cl and Au(tht)Cl-KPF 6 system affords complexes [Au(L)Cl] and [AuL 2 ]PF 6 , in which a linear P–Au–P coordination is realized. Complex [AuL 2 ]PF 6 , upon treatment with AgPF 6 or CuPF 6 , unexpectedly forms penta-nuclear clusters [Au@Ag 4 L 4 ](PF 6) 5 and [Au@Cu 4 L 4 ](PF 6) 5 , respectively, showing Au-centered tetrahedral Ag 4 /Cu 4 kernel supported by four L ligands in P , N , N ′, N ″ - bridging manner. The structurally similar all-silver cluster [Ag@Ag 4 L 4 ](BF 4) 5 has been assembled by the direct reaction of L with AgBF 4. According to X-ray crystallography data and QTAIM study, the synthesized clusters {Au@Ag 4 }, {Au@Cu 4 } and {Ag@Ag 4 } feature the pronounced attractive metallophilic d10-d10 interactions between the central (Au/Ag) and peripherical (Cu, Ag) metal atoms. At ambient temperature, the title complexes exhibit room-temperature phosphorescence at λ max = 501–572 nm with emission lifetimes of microsecond order (τ = 0.86–20 µs) and the quantum yields of up to 23 %. [ABSTRACT FROM AUTHOR]

Here we present a new family of seven Sc(III) complexes with a tetrafluoroterephthalate ligand (tFBDC2−), having non-polymeric and polymeric 2D and 3D structures. These complexes are characterized by SC XRD, PXRD, FT-IR, elemental analysis, and TGA. Among these complexes, 3D coordination polymers [Sc(H2O)(tFBDC)1.5]·H2O (1), [Sc2(H2O)2(tFBDC)3]·2H2O (2), and [Sc(H2O)(tFBDC)1.5]·4H2O (3) are supramolecular isomers. Complex 1 is obtained as a phase pure material, while 2 and 3 are found as admixtures. The reaction of Sc(CF3SO3)3 with H2tFBDC in the presence of NH3 as a base produces layered coordination polymer [Sc(H2O)(OH)(tFBDC)] (4). Complexes (NH4)[Sc(H2O)4(tFBDC)2]·5H2O (5), [K(H2O)2Sc(H2O)4(tFBDC)2]·3H2O (6) and [Cs(H2O)4Sc(H2O)4(tFBDC)2]·0.5H2O (7) based on the same [Sc(H2O)4(tFBDC)2]− anionic unit are obtained by precipitation with NH3, KOH or CsOH. Coordination polymers 1 and 4 are stable in an aqueous solution in the range of pH 2–12. Solid complexes 1, 4–7 show ligand-centred purple/blue photoluminescence, with 1 and 4 having high quantum yields of 28 and 34% at room temperature. [ABSTRACT FROM AUTHOR]

Mononuclear copper(I) complexes [CuL2]I (1), [CuL2]2[Cu2I4]·2MeCN (2) and [CuL2]PF6 (3) with a new chelating pyrazolylpyrimidine ligand, 2-(3,5-dimethyl-1H-pyrazol-1-yl)-4,6-diphenylpyrimidine (L), were synthesized. In the structures of complex cations [CuL2]+, Cu+ ions coordinate two L molecules (N,N-chelating coordination). Extended π-systems of the L molecules in [CuL2]+ favor the formation of paired π–π stacking intramolecular interactions between the pyrimidine and phenyl rings leading to significant distortions of tetrahedral coordination cores, CuN4. The free ligand L demonstrates dual excitation wavelength dependent luminescence in the UV and violet regions, which is attributed to S1 → S0 fluorescence and T1 → S0 phosphorescence with intraligand charge transfer character. The complexes 1–3 demonstrate T1 → S0 phosphorescence in the near-infrared region. Theoretical investigations point to its ligand-to-metal charge transfer (LMCT) origin. Large Stokes shifts of emission (ca. 200 nm) are the result of notable planarizations of CuN4 cores in the T1 state as compared to the S0 state. Spin–orbit coupling computations revealed that the most effective intersystem crossing channels for [CuL2]+ appear in high-lying excited states, while the S1 → T1 transition is unfavourable according to El-Sayed's rule and the energy gap law. Electron-vibration coupling calculations showed that the C–C and C–N stretching vibrations of the pyrimidine and phenyl moieties, the asymmetric Cu–N stretching vibrations and the wagging motions of phenyl rings contribute the most to the non-radiative deactivation of L and [CuL2]+. [ABSTRACT FROM AUTHOR]

The synthesis of Al 2 O 3 :Tb3+ (0.019–0.62 mol%) nanoparticles by laser vaporization of α-Al 2 O 3 :Tb3+ ceramic targets using a cw CO 2 laser in flowing helium at a pressure of 0.1 bar is reported. HRTEM, XRD and BET studies revealed that under the indicated conditions the produced Al 2 O 3 :Tb3+ nanoparticles have faceted and nearly a spherical shape with the average size below 10 nm. As shown by XRD, the phase composition of the synthesized nanoparticles is represented mostly by the low-temperature γ-Al 2 O 3. Photoluminescence (PL) spectra were obtained for Tb3+ ions in γ-Al 2 O 3 nanoparticles upon excitation to the 4f8 → 4f75d (λ ex = 230 nm), 7F 6 → 5H 7 (λ ex = 315 nm) and 5D 3 → 7F 3 (λ ex = 458 nm) transitions, and PL excitation spectra – for the most intense 5D 4 → 7F 5 (λ max = 543 nm) transition. The lifetime of the excited 5D 4 state was found to be ca. 2.9 ms. The obtained values of the chromaticity coordinate and absolute quantum yield were (0.299, 0.509) and 12.6% at λ ex = 315 nm, respectively. • Terbium doped Al 2 O 3 nanoparticles were obtained via laser vaporization. • Al 2 O 3 :Tb3+ nanophosphor with photoluminescent properties was achieved. • CIE coordinates and high QY are suitable for use Al 2 O 3 :Tb3+ as a green phosphor. [ABSTRACT FROM AUTHOR]

A series of mononuclear heteroleptic copper(I) halide complexes, [CuL(PPh3)X] (X = Cl, Br, I), based on 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L) and triphenylphosphine, have been synthesized by reaction between CuX (X = Cl, Br, I), L and PPh3 in a molar ratio of 1/1/1 in MeCN solutions. The copper atom, showing the distorted tetrahedral environment, is bound by the N,N-chelating ligand L, triphenylphosphine and a halide ion. The complexes [CuL(PPh3)Cl] and [CuL(PPh3)Br] are isostructural. In CH2Cl2 solutions, L and the complexes [CuL(PPh3)X] (X = Cl, Br, I) display a luminescence band with λmax = 377 nm and a lifetime of 1.9 ns (ligand-based luminescence (LL*)). However, the complex [CuL(PPh3)I] has an additional weak luminescence band with λmax = 681 nm and a lifetime of 96 ns of 3MLCT origin. In the solid state, L shows the splitting of the luminescence band to λmax = 365 and 384 nm and a slight increase of the lifetime to 2.66 ns. Solid samples of the complexes [CuL(PPh3)X] demonstrate 3MLCT luminescence bands at 620 nm (X = Cl), 605 nm (X = Br) and 559 nm (X = I) with lifetimes in the range 3.6-11.2 μs, whereas the LL* band (377 nm) is absent. Quantum yields and rate constants of radiative and nonradiative processes were determined in CH2Cl2 solutions and in the solid state for all complexes. The luminescence quantum yield and lifetimes for the solid samples increase in the order [CuL(PPh3)Cl] < [CuL(PPh3)Br] < [CuL(PPh3)I]. This is due to the increase of radiative decay and simultaneous suppression of nonradiative decay. The complex [CuL(PPh3)I] shows a high quantum yield of 29.4% and an excited state lifetime of 11.2 μs. [ABSTRACT FROM AUTHOR]

ZnLCl and [H2L]2[ZnCl4], based on 2-(1-hydroxy-4,5-dimethyl-1H-imidazol-2-yl)pyridine (HL), have been synthesized. There is a short intraionic O–H···N hydrogen bond between the hydroxyimidazolyl and pyridyl of H2L+cations (N···O 2.608(2) Å) in the structure of [H2L]2[ZnCl4]. The formation of this rather strong hydrogen bond is confirmed by IR spectroscopy through a broad band at 3200–2200 cm−1and a band at 1655 cm−1. HL crystallizes in the form of a hemihydrate, HL·0.5H2O. HL assemble into infinite helical chains due to N–H···O intermolecular hydrogen bonds between the NH of imidazole and O of the N-oxide (O···N 2.623(2) Å). An unusual mid-IR pattern with three broad bands at 3373, 2530, and 1850 cm−1is typical for strong hydrogen bonds, explained by resonance-assisted hydrogen bonding occurring in the helical chains. On cooling to 5 K, noticeable changes in the IR spectra of [H2L]2[ZnCl4] and HL·0.5H2O were observed. ZnLCl and [H2L]2[ZnCl4] exhibit bright photoluminescence with maxima of emission at 458 nm (for ZnLCl) and 490 nm (for [H2L]2[ZnCl4]). [ABSTRACT FROM AUTHOR]

A series of Eu doped ZrO 2 micropowders with different concentration of Eu (0.04–6.85 wt%) was obtained by incipient wetness impregnation followed by annealing at 1200 °C. X-ray diffraction analysis revealed that the phase composition of samples with the minimum Eu concentrations in the series is represented predominantly by the monoclinic phase. An increase in the Eu content leads to proportional stabilization of the tetragonal phase, and at concentrations above 2.00 wt% the cubic ZrO 2 phase is also stabilized. It was shown that red luminescence of the samples is responsible for the radiation transitions 5D 0 → 7F J (J = 0–4) in Eu3+ ions. It was shown that shaping the photoluminescence spectrum of monoclinic ZrO 2 :Eu3+ phosphor depending on Eu concentration is related to the stabilization of ZrO 2 tetragonal and cubic structure by Eu3+. The local symmetry of Eu3+ in each of the detected phases was identified. The lifetime of Eu3+ in the monoclinic phase of ZrO 2 does not depend on the dopant concentration and is in the range of 0.73–0.81 ms, whereas in the tetragonal phase it first increases from 1.7 to 1.85 ms and then reaches a maximum at a concentration of 2.00 wt%. The absolute quantum yield increases from 1.6 to 4.8% over the entire range of Eu concentration. • ZrO 2 :Eu3+ (0.04–6.85 wt%) powders with red emission was achieved. • The local symmetry of Eu3+ in ZrO 2 polymorphs was identified. • Eu content leads to stabilization of the tetragonal and cubic ZrO 2 phase. • Shaping the PL spectrum of ZrO 2 :Eu3+ via polymorphism of the lattice was observed. • QY increases from 1.6 to 4.8% over the entire range of Eu content. [ABSTRACT FROM AUTHOR]

Abstract: A series of zinc(II) and cadmium(II) complexes with 4-(3,5-diphenyl-1H-pyrazol-1-yl)-6-(piperidin-1-yl)pyrimidine (L), ZnLCl2, CdLCl2, ZnL2Cl2, CdL2Cl2, CdL2Cl2·0.5Me2CO·1.5H2O and CdL2Cl2·0.5CHCl3·0.5H2O, have been synthesized. The compounds ZnLCl2 and CdLCl2 were obtained in a M:L=1:1 molar ratio in EtOH solutions, while ZnL2Cl2 and CdL2Cl2 were isolated in a M:L=1:3 molar ratio in EtOH/Me2CO mixtures. Surprisingly, attempts to crystallize CdLCl2 from EtOH/Me2CO mixture afforded single crystals of a compound, having 1:2 metal-to-ligand stoichiometry, CdL2Cl2·0.5Me2CO·1.5H2O, instead of a complex with 1:1 stoichiometry. At the same time, crystallization of CdL2Cl2 from Me2CO/CHCl3 mixture afforded CdL2Cl2·0.5CHCl3·0.5H2O single crystals. According to X-ray crystal structure data, ZnLCl2, ZnL2Cl2, CdL2Cl2·0.5Me2CO·1.5H2O and CdL2Cl2·0.5CHCl3·0.5H2O complexes have molecular mononuclear structures. The molecules of L adopt bidentate chelating binding mode being coordinated to the metal ions through N2 atom of the pyrazole and N3 atom of the pyrimidine rings. The coordination core of zinc atom in ZnLCl2 complex is a distorted ZnN2Cl2 tetrahedron. The coordination cores of metal atoms in the structures of ZnL2Cl2, CdL2Cl2·0.5Me2CO·1.5H2O and CdL2Cl2·0.5CHCl3·0.5H2O are the distorted cis-MN4Cl2 (M=Zn, Cd) octahedra. In the structure of ZnL2Cl2 double lone pair(N(piperidine))–π(pyrimidine) interactions were observed. The photoluminescent properties of L, ZnLCl2, CdLCl2, ZnL2Cl2 and CdL2Cl2 were studied in the solid state under the same experimental conditions. These compounds were found to display bright blue luminescence. Highest relative intensity of emission was detected for ZnL2Cl2. [Copyright &y& Elsevier]

Abstract: Zinc(II) and cadmium(II) complexes, ZnL2 ⋅0.5H2O, ZnL2 ⋅2MeOH and CdL2 ⋅1.5H2O, based on a new hybrid compound, 2-(3,5-dimethyl-1 H-pyrazol-1-yl)-6-(4-methoxyphenyl)pyrimidine-4-carboxylic acid (HL), have been synthesized. They are the first examples of metal complexes with pyrazolylpyrimidinecarboxylates. The complex ZnL2 ⋅2MeOH was structurally characterized. It has mononuclear structure; zinc atom is in the distorted octahedral coordination polyhedron 4N+2O formed by donor atoms of two coordinated L− ions. The compounds HL, ZnL2 ⋅0.5H2O and CdL2 ⋅1.5H2O manifest bright blue photoluminescence. [Copyright &y& Elsevier]

Europium doped Gd 2 O 3 sphere-like nanoparticles with d m = 9.3 ± 3.5 nm were synthesized by cw CO 2 laser vaporization technique in a flowing mixture of argon and oxygen. According to XRD data, the Eu:Gd 2 O 3 nanoparticles crystallize in the monoclinic symmetry class (C2/m space group). High-resolution luminescence spectroscopy study showed that the ultra-narrow 5D 0 → 7F 0 transition of Eu3+ demonstrates only two peaks corresponding to two inequivalent C s positions of Eu3+ ion in monoclinic Gd 2 O 3 lattice that is explained by the peculiarities of local environment of Eu3+ ion at these sites. The hypersensitive transition 5D 0 → 7F 2 dominates in the spectrum and is expanded to the red part of the spectrum in comparison with cubic Eu:Gd 2 O 3 due to intense transitions terminating at higher-lying components of the crystal-field-split 7F 2 state. In the luminescence spectrum, an additional weak band with the maximum at 407 nm corresponding to the electronic transitions 4f65 d1(7F J) → 4f7(8S 7/2) of Eu2+ was detected. The obtained values of chromaticity coordinates and absolute quantum yield are (0.644; 0.325) and ca. 1%, respectively. The phase transformations have been investigated using differential scanning calorimetry and thermogravimetry (50–1400 °C). After annealing in air at 700 °C, the monoclinic symmetry class of the Eu:Gd 2 O 3 nanoparticles is preserved and the particle size increases to d m = 17.8 ± 6.1 nm. After annealing, the chromaticity coordinates (0.659; 0.334) and absolute quantum yield (ca. 4%) can be obtained using red phosphor based on monoclinic Gd 2 O 3 :Eu3+. The lifetime of the excited 5D 0 state of Eu3+ in the annealed nanoparticles is longer than that in the as-synthesized nanoparticles, due to the suppression of nonradiative decay after annealing. [Display omitted] • Monoclinic Eu doped Gd 2 O 3 nanoparticles are obtained by laser vaporization technique. • Simultaneous observation of Eu3+ and Eu2+ emissions through PL spectroscopy is reported. • CIE coordinates are suitable for using monoclinic Gd 2 O 3 :Eu3+ as a red phosphor. [ABSTRACT FROM AUTHOR]