•Relaxation pathways of the LMCT-excited Cu(II) Cl-complexes in CH3CN were revealed.•Combination of the steady-state photolysis and ultrafast spectroscopy was used.•Major part of the LMCT-excited ...complexes relaxes to ground state parent complex.•Minor fraction of the LMCT-excited complexes dissociates into photoproducts.•CuIICln2−n photodissociate into CuIICln−13−n+Cl− and CuICln−12−n+Cl.
Photochemistry of Cu(MeCN)3Cl+, Cu(MeCN)Cl3−, and CuCl42− copper(II) chlorocomplexes in acetonitrile solution is studied by means of the combination of the steady-state photolysis and ultrafast transient absorption methods. The main relaxation pathways of the initially excited ligand-to-metal charge transfer states are internal conversion to the ground state, ionic dissociation without (photo)reduction of copper(II), and radical dissociation with (photo)reduction of copper(II). The copper(II)-to-copper(I) photoreduction quantum yields obtained from steady-state photolysis correlate with ultrafast spectroscopy data. The presence of oxygen does not affect the photoreduction quantum yields, which do not exceed 7% for the complexes studied and decrease in the series: Cu(MeCN)3Cl+>Cu(MeCN)Cl3−>CuCl42−.
The series of luminescent NaYF
:Sm
nano- and microcrystalline materials co-doped by La
, Gd
, and Lu
ions were synthesized by hydrothermal method using rare earth chlorides as the precursors and ...citric acid as a stabilizing agent. The phase composition of synthesized compounds was studied by PXRD. All synthesized materials except ones with high La
content (where LaF
is formed) have a β-NaYF
crystalline phase. SEM images demonstrate that all particles have shape of hexagonal prisms. The type and content of doping REE significantly effect on the particle size. Upon 400 nm excitation, phosphors exhibit distinct emission peaks in visible part of the spectrum attributed to
G
→
H
transitions (J = 5/2-11/2) of Sm
ion. Increasing the samarium (III) content results in concentration quenching by dipole-dipole interactions, the optimum Sm
concentration is found to be of 2%. Co-doping by non-luminescent La
, Gd
and Lu
ions leads to an increase in emission intensity. This effect was explained from the Sm
local symmetry point of view.
The series of luminescent NaYFsub.4:Smsup.3+ nano- and microcrystalline materials co-doped by Lasup.3+, Gdsup.3+, and Lusup.3+ ions were synthesized by hydrothermal method using rare earth chlorides ...as the precursors and citric acid as a stabilizing agent. The phase composition of synthesized compounds was studied by PXRD. All synthesized materials except ones with high Lasup.3+ content (where LaFsub.3 is formed) have a β-NaYFsub.4 crystalline phase. SEM images demonstrate that all particles have shape of hexagonal prisms. The type and content of doping REE significantly effect on the particle size. Upon 400 nm excitation, phosphors exhibit distinct emission peaks in visible part of the spectrum attributed to sup.4Gsub.5/2→sup.6Hsub.J transitions (J = 5/2-11/2) of Smsup.3+ ion. Increasing the samarium (III) content results in concentration quenching by dipole-dipole interactions, the optimum Smsup.3+concentration is found to be of 2%. Co-doping by non-luminescent Lasup.3+, Gdsup.3+ and Lusup.3+ ions leads to an increase in emission intensity. This effect was explained from the Smsup.3+ local symmetry point of view.
The ultrafast photochemistry of the Cr(NCS)63– complex upon excitation to the 4T2 ligand-field (LF) state was studied in dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) in a wide temporal ...range (100 fs to 9 ms) by a combination of femtosecond and nanosecond transient absorption spectroscopy techniques and supported by quantum-chemical DFT/TD-DFT calculations. The initially excited 4T2 state undergoes intersystem crossing to the vibrationally hot 2E state with time constants of 1.1 ± 0.2 and 1.8 ± 0.1 ps in DMSO and DMF, respectively. Vibrational relaxation occurs in the same time scale and takes 1–5 ps. A major part of the Cr(NCS)63– complex in the 2E state undergoes intersystem crossing to the ground state with time constants of 65 ± 5 and 85 ± 5 ns in DMSO and DMF, respectively. A minor part of electronically excited Cr(NCS)63– undergoes irreversible photochemical decomposition. In DMSO, the photolysis of the Cr(NCS)63– complex results in single or double isothiocyanate ion release followed by the coordination of the solvent molecules with a time constant of 1 ± 0.2 ms.
A rare layered Zn(II) terephthalate metal–organic framework with 6-connected hxl topology, stacking along the a axis in an eclipsed arrangement giving shape to triangular channels. Display omitted
► ...A 2D Zn(II) terephthalate metal–organic framework has been prepared. ► The structure shows rare layered structure with 6-connected hxl topology. ► The vibrational properties were studied by Raman and infrared spectroscopy. ► Thermal gravimetric analysis together with photoluminescence properties have been discussed in detail.
The crystal structure and vibrational spectra of a new Zn(II) terephthalate 2D metal–organic framework, Zn3(tp)3(DMSO)2)n (H2tp=terephthalic acid; DMSO=dimethyl sulfoxide), together with its thermal behavior and photoluminescence properties have been studied. The structure shows a rare layered structure with 6-connected hxl topology, constructed from trinuclear Zn3C14H8O14S2 units, and crystallizes in the monoclinic system, space group P21/c (No. 14). The asymmetric units consist of two crystallographically independent Zn(II) ions, one and a half tp ligands and one disordered DMSO molecule. One of the Zn(II) ions adopts a disordered tetrahedral geometry, coordinated by four O atoms from three different tp ligands and one terminal disordered DMSO ligand, while the other is surrounded by six oxygen atoms from six tp ligands to form an octahedral geometry configuration. The tp2− ligands act as μ4-bridges linking four Zn(II) centers through different coordination modes. IR and Raman vibrational spectra were recorded and the full assignment of the vibrational frequencies is proposed.
In this work, three series of micro-sized heterometallic europium-containing terephthalate MOFs, (Eu
Ln
)
bdc
·nH
O (Ln = La, Gd, Lu), are synthesized via an ultrasound-assisted method in an aqueous ...medium. La
and Gd
-doped terephthalates are isostructural to Eu
bdc
·4H
O. Lu
-doped compounds are isostructural to Eu
bdc
·4H
O with Lu contents lower than 95 at.%. The compounds that are isostructural to Lu
bdc
·2.5H
O are formed at higher Lu
concentrations for the (Eu
Lu
)
bdc
·nH
O series. All materials consist of micrometer-sized particles. The particle shape is determined by the crystalline phase. All the synthesized samples demonstrate an "antenna" effect: a bright-red emission corresponding to the
D
-
F
transitions of Eu
ions is observed upon 310 nm excitation into the singlet electronic excited state of terephthalate ions. The fine structure of the emission spectra is determined by the crystalline phase due to the different local symmetries of the Eu
ions in the different kinds of crystalline structures. The photoluminescence quantum yield and
D
excited state lifetime of Eu
are equal to 11 ± 2% and 0.44 ± 0.01 ms, respectively, for the Ln
bdc
·4H
O structures. For the (Eu
Lu
)
bdc
·2.5H
O compounds, significant increases in the photoluminescence quantum yield and
D
excited state lifetime of Eu
are observed, reaching 23% and 1.62 ms, respectively.
Solvation of europium ions in mixed aqueous-organic solvents was studied in the solutions of europium(III) triflate and chloride. Europium ions are preferentially solvated by organic solvent only in ...water-dimethylsulfoxide systems. In aqueous dimethylformamide and dimethylacetamide preferential hydration in water-deficient region was observed. The total solvation number was proved to decrease from 9 in neat water to 8 in neat dimethylsulfoxide and dimethylformamide and to 7 in neat dimethylacetamide. The formation of chlorocomplexes in neat water and aqueous dimethylacetamide was observed.
•The composition of europium(III) ions first solvation sphere was determined by using TRLF spectroscopy.•The strongest preferential solvation is observed in aqueous-DMSO systems.•Complexation with chlorides leads to the decrease of Eu(III) total coordination number.•The formation of 8- and 7-coordinated (only in aqueous DMA with Xdma>0,9) species was proved.
Display omitted
•Electronic spectra of the copper(II) halide complexes in acetonitrile were obtained.•Stability constants of the copper(II) halide complexes were calculated.•The lowest-energy forms ...of copper(II) halide complexes were determined.•Copper(II) coordination number decreases upon increase the number of halide ions.•Experimental electronic absorption spectra are consistent with TD-DFT calculations.
The results of spectrophotometric study and quantum chemical calculations for copper(II) chloro- and bromocomplexes in acetonitrile are reported. Electronic spectra of the individual copper(II) halide complexes were obtained in a wide spectral range 200–2200 nm. Stability constants of the individual copper(II) halide complexes in acetonitrile were calculated: log β1 = 8.5, log β2 = 15.6, log β3 = 22.5, log β4 = 25.7 for CuCln2−n and log β1 = 17.0, log β2 = 24.6, log β3 = 28.1, log β4 = 30.4 for CuBrn2−n. Structures of the studied complexes were optimized and electronic spectra were simulated using DFT and TD-DFT methodologies, respectively. According to the calculations, the more is the number of halide ligands the less is coordination number of copper ion.
A method is presented for isolating iodine isotopes from aqueous coolant of the nuclear power plants’ first circuit. At first, all forms of iodine radionuclides are converted into molecular form by ...the sequential addition of a carrier–potassium iodide, as well as hydroxylamine chloride, nitric acid and potassium nitrite. Then molecular iodine is transferred into the gas phase and volatile iodine radionuclides are immobilized on a membrane impregnated with metallic silver. The main advantage of the method is high selectivity of iodine release in relation to radionuclides interfering with the measurement of its activity.
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