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•The spectroscopic data are essential for the use of the theoretical model.•The energy gap between the ligand and Yb excited states is large.•The theoretical model shed light on the ...ligand-to-Yb energy transfer phenomenon.•The theoretical model used allows to estimate the quantum yield of the Yb emission.•The charge transfer state plays an important role in the energy transfer process.
We present the experimental and theoretical results that made it possible to propose the energy transfer mechanism for a Yb complex with a large energy gap between the ligand and Yb excited states using a theoretical model and experimental data. Absorption and emission spectroscopy in the 300–4 K range is used for the study of the Yb3+ compound with N-phosphorylated sulfonamide (NaYbL4), which, despite the large energy gap, is characterized by high emission sensitization efficiency (ηsens = 40%) and relatively long Yb3+ emission lifetime (27 μs). The crystal structure of NaYbL4, radiative lifetime (930 μs), refractive index (1.46), intrinsic (3.0%), and overall (1.3%) emission quantum yield were determined. To obtain the electronic properties of the NaYbL4, a time-dependent density functional theory (TD-DFT) was performed. The intramolecular energy transfer (IET) rates from the excited states S1 and T1 to the Yb3+ ion as well as between the ligand and the ligand-to-metal charge transfer (LMCT) states were calculated. Once the intersystem crossing S1 → T1 is not so effective due to a large energy gap between S1 and T1 (≈10000 cm−1), it has been shown that the LMCT state acts as an additional channel to feed the T1 state. Then, the T1 can transfer energy to the Yb3+ 2F5/2 energy level (WT), where WT is dominated by the exchange mechanism. Based on IET and a rate equation model, the overall emission quantum yield QLLn was simulated with and without the LMCT, this also confirmed that the pathway S1 → LMCT → T1 → Yb3+ is more likely than the S1 → T1 → Yb3+ one.
Lanthanide complexes with efficient antenna effect and multifunctional optical-magnetic activity are very appropriate for potential applications. Multidentate ligands efficiently sensitizing emission ...of different lanthanide ions are rare and complexes often suffer from bleaching. Presented here are photostable lanthanide complexes with single-magnet behavior as the first example in which, using the same sensitizer and the same excitation wavelength, extremely high overall emission quantum yields are achieved for various lanthanide ions ( Q LEu = Q LTb = 98%, Q LSm = 11%, Q LDy = 17%). This is confirmed through computational and experimental analyses. We rationalize the process of energy transfer from the ligand to Eu 3+ , which was firstly understood in lanthanide compounds with N -phosphorylated carboxamides. The results revealed that in addition to the refractive index, the energy of the ligand triplet state and donor–acceptor distance, overall emission quantum yield is also a function of triplet state lifetime. It is demonstrated how proper design of the energetic and structural properties of the sensitizer and the introduction of excess Na ions into the structure of Ln complexes allow obtaining extremely efficient light converting molecular devices with single-ion magnet behavior.
Two series of rare earth coordination compounds have been synthesized (NaRE(L4) (labeled as 1RE) and PPh4RE(L4) (labeled as 2RE), where RE = Y3+, Eu3+, Tb3+, ...L = 2,2,2-trichloro-N-(diphenylphosphoryl)acetamide) to determine the possibility of modifying their photophysical and magnetical properties by changing the counterion. The crystal structure of 1RE was determined based on the single-crystal X-ray diffraction and the crystal structure of 2RE was determined based on quantum chemistry computational procedures. Characterization of the physicochemical properties of the compounds was carried out using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), 1H and 31P NMR spectroscopy as well as FT-IR, absorption and luminescence spectroscopy in the temperature range of 300 - 77 K. The rate constants of radiative (Arad) and non-radiative (Anrad) transitions, intrinsic (QLnLn) and overall (QLnL) emission quantum yields, sensitization efficiency (ηsens), the experimental and theoretical intensity parameters (Ωλ), the forward (WS, WT) and backward (WbS, WbT) intramolecular energy transfer (IET) rates were determined. Magnetic properties of Tb3+ compounds were studied in a constant field of 0.5 T in the temperature range of 1.8–300 K. Dynamic AC magnetic susceptibility measurements were carried out as a function of temperature and frequency for 1Tb and 2Tb. Only in the case of 2Tb, in the presence of an external DC field, a slight temperature dependence of in-phase χ′ and out-of-phase χ'' susceptibility was recorded. Based on experimental and theoretical results, the significant effect of counterion on the photophysical and magnetic properties of RE chelates has been demonstrated and clarified, providing valuable guidance for the design of bifunctional electromagnetic radiation converters.
•Two series of lanthanide chelates with N-phosphorylated acetamide were synthesized.•Replacing Na+ with PPh4+ reduces 4f levels splitting and 5D0, 5D4 emission lifetime.•The PPh4+ electron density participates in S1 and T1 excited states.•Singlet and triplet energy transfer mediated mainly by an exchange mechanism.•The choice of counterion is crucial to the efficiency of ligand-metal energy transfer.
The increased interest in designing bifunctional magnetic-luminescent compounds stems from their promising application potential. Appropriately designed lanthanide coordination compounds were found ...suitable for this purpose. This work describes the structural, optical and magnetic properties of photostable lanthanide coordination compounds (Nd, Yb) with N-(diphenylphosphoryl)pyrazine-2-carboxamide (HL) acting as an antenna. Optical properties of the compounds were characterized by IR, high-resolution absorption and emission spectroscopies at 300, 77 and 5 K. The trinuclear coordination compounds (labeled as Na2LnL4), with a crystal structure stiffened by eight oxygen bridges with eight-coordinated lanthanide ion, as well as six- and seven-coordinated Na ions, were found to be excellent converters of UV radiation into the NIR. The ligand-to-metal energy transfer mechanisms in Na2NdL4 were discussed. Na2YbL4 reached the highest (QYbL = 5.8%) overall emission quantum yield among the coordination compounds of Yb3+ with organic ligands in solid state. The static and dynamic magnetic properties of Na2NdL4 and Na2YbL4 were studied, revealing that the compounds exhibit behavior of field-induced Single Ion Magnets (SIMs) with the effective energy barrier value of 27.4 K (Na2NdL4) and 26.2 K (Na2YbL4). The anisotropic barrier was extracted from static magnetism and optical properties analysis, giving an insight into the magneto-optical correlation. We demonstrated that proper design of ligand structure and coordination compound architecture allows to obtain molecular magnets with optimized infrared emission.
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•Nd and Yb complexes with a carboxamide derivative were obtained as single crystals.•Crystal structure is stiffened by numerous bridges and non-covalent interactions.•The Nd and Yb complexes exhibit a strong antenna effect and SIM behavior.•Bifunctionality of the complexes results from their structural and energetic factors.•Dipole and exchange mechanisms take part in the ligand-to-metal energy transfer.
In the title complex, Cu(C8H11NO5PS)(C18H15P)2, the Cu(I) ion is coordinated by two tri-phenyl-phosphane mol-ecules and two O atoms of the chelating dimeth-yl(phenyl-sulfon-yl)amido-phosphate anion, ...generating a squashed CuO2P2 tetrahedron. In the six-membered chelate ring, the Cu, P and O atoms are almost coplanar (r.m.s. deviation = 0.024 Å), with the N and S atoms displaced in the same direction, by 0.708 (5) and 0.429 (2) Å, respectively.
In the molecular structure of the title compound, NaNi(C18H18N2O4)(NO3)(CH3OH), the Ni(2+) ion has a slightly distorted square-planar coordination environment defined by two N and two O atoms which ...belong to a Schiff base ligand, viz. 6,6'-dimeth-oxy-2,2'-ethane-1,2-diylbis(nitrilo-methanylyl-idene)diphenolate. Seven O atoms form the coordination environment of the Na(+) ion: four from the Schiff base ligand, two from a bidentate chelating nitrate anion and one O atom from a coordinating methanol mol-ecule. In the crystal, the bimetallic complexes are assembled into chains along the b-axis direction via weak C-H⋯O hydrogen-bond inter-actions. Neighbouring chains are in turn connected through bifurcated O-H⋯O hydrogen bonds that involve the coordinating methanol mol-ecules and the nitrate anions, and through π-π stacking inter-actions between phenyl rings of neighbouring mol-ecules.
Lanthanide coordination compounds of the formula NaLn(L)4 (1Ln), where Ln = La3+, Eu3+, Gd3+, Tb3+, L = L− and HL = dimethyl(4-methylphenylsulfonyl)amidophosphate, were synthesized. Their structural ...and spectroscopic properties were discussed in detail based on X-ray diffraction measurements, IR spectroscopy, absorption and emission spectroscopy at 293 and 77 K and theoretical calculations of the intramolecular energy transfer (IET) rates. DFT calculations were used to investigate the 1Ln electronic properties required to calculate the transition rates. 30 and 22 pathways of intramolecular nonradiative energy transfer were examined in the case of 1Eu and 1Tb, respectively. It is shown that the main pathway for sensitization of the lanthanide emission is either the triplet (1Eu) or singlet (1Tb) transfer, occurring mainly through the exchange mechanism. The energy rates for energy transfer from S1 and T1 equal WS=1.53×105s−1 (1Eu), WT=5.14×106s−1 (1Eu) and WS=4.09×107s−1 (1Tb), WT=6.88×105s−1 (1Tb). The crucial role of the 7F5 level in the energy transfer process of 1Tb and the participation of the LMCT state in the depopulation of the ligand singlet state of 1Eu were demonstrated. The influence of the resonance effect on the splitting of the 7F1 level in 1Eu was analyzed. By comparing the properties of 1Ln with the properties of 2Ln coordination compounds, sharing the same ligand and crystallizing in the same crystallographic system (monoclinic), but with a different space group, it is demonstrated how slight structural changes can affect the photophysical properties of Ln compounds.
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Two series of the Ln complexes with the same first coordination sphere were obtained. It was shown how minor structural changes cause major consequences in their photophysical properties. The crucial role of the 7F5 level and the LMCT state in the energy transfer process was demonstrated. The main pathways for sensitization of the lanthanide emission are the triplet (1Eu) and singlet (1Tb) transfer occurring mainly through the exchange mechanism.
•Two series of the Ln complexes with the same first coordination sphere were obtained.•It was shown how minor structural changes cause major consequences in their photophysical properties.•The crucial role of the 7F5 level and the LMCT state in the energy transfer process was demonstrated.•The main pathways for sensitization are the triplet (1Eu) and singlet (1Tb) transfer occurring mainly through the exchange mechanism.
Lanthanide complexes with efficient antenna effect and multifunctional optical-magnetic activity are very appropriate for potential applications. Multidentate ligands efficiently sensitizing emission ...of different lanthanide ions are rare and complexes often suffer from bleaching. Presented here are photostable lanthanide complexes with single-magnet behavior as the first example in which, using the same sensitizer and the same excitation wavelength, extremely high overall emission quantum yields are achieved for various lanthanide ions (
Q
L
Eu
=
Q
L
Tb
= 98%,
Q
L
Sm
= 11%,
Q
L
Dy
= 17%). This is confirmed through computational and experimental analyses. We rationalize the process of energy transfer from the ligand to Eu
3+
, which was firstly understood in lanthanide compounds with
N
-phosphorylated carboxamides. The results revealed that in addition to the refractive index, the energy of the ligand triplet state and donor-acceptor distance, overall emission quantum yield is also a function of triplet state lifetime. It is demonstrated how proper design of the energetic and structural properties of the sensitizer and the introduction of excess Na ions into the structure of Ln complexes allow obtaining extremely efficient light converting molecular devices with single-ion magnet behavior.
Well-designed Ln compounds are UV converters with extremely high, triplet lifetime dependent emission QY, and show SIM behavior.
The crystal structure of the title compound, NaNd(C8H11NO5PS)4n, is composed of two types of crystallographically independent polymeric chains, A and B, respectively, which are formed by alternating ...anions and sodium cations. In both polymeric chains, NdIII ions are eight‐coordinated by O atoms belonging to the sulfonyl and phosphoryl groups of four bidentate chelate ligands. In chain A, the coordination polyhedron of the NdIII ion has a conformation intermediate between bicapped trigonal‐prismatic and square‐antiprismatic, and the NaI ion is coordinated by two N and four O atoms in a distorted octahedral geometry. In chain B, the coordination polyhedron of Nd is a slightly distorted square antiprism, and Na is coordinated by four O atoms in a distorted tetrahedral geometry.
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