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Six new complexes [Cd(tpy)(pfb)2] (1, tpy = 2,2′:6′,2″-terpyridine), [Ln2Cd2(tpy)2(pfb)10] (Ln = Eu (2Eu), Tb (2Tb)), [Ln2Cd2(tbtpy)2(pfb)10]·2MeCN (Ln = Eu (3Eu), Tb (3Tb), tbtpy = 4,4′,4″-tri-tert-butyl-2,2′:6′,2″-terpyridine), [Eu2Cd2(tppz)(pfb)10]n (4, tppz = 2,3,5,6-tetra-(pyridin-2-yl)pyrazine) based on pentafluorobenzoic acid (Hpfb) have been prepared and investigated. The effect of tridentate ligands on geometry heterometallic scaffolds synthesized complexes is discussed. The supramolecular crystal structures of the new compounds are stabilized by π-π, C-F···π, C-H···O, C-H...F, F….F interactions. Non-covalent interactions have been studied using Hirschfeld surface analysis. The obtained compounds were characterized by single-crystal and powder X-ray diffraction, luminescence spectroscopy, IR spectroscopy, CHN analysis. Complexes 2Ln and 3Ln exhibit metal-centered photoluminescence, but the presence of ligand luminescence bands indicates incomplete energy transfer from the d-block to the lanthanide ion.

The systematic series of trinuclear carboxylate complexes [Zn2Ln(NO3)(phbz)6(L)2] (Ln = Eu, Gd, and Tb, where phbz is the anion of 4-biphenylcarboxylic acid, and L is pyridine, 2,3-lutidine or 2,2′-bipyridine) were synthesized. Luminescence properties were investigated in detail.

The mononuclear title complex, [Eu(C24H34O4P)3(CH4O)5]·CH4O, (1), has been obtained as a minor product in the reaction between EuCl3(H2O)6 and lithium bis(2,6-diisopropylphenyl) phosphate in a 1:3 molar ratio in a methanol medium. Its structure exhibits monoclinic (P21/c) symmetry at 120 K and is isostructural with the La, Ce and Nd analogs reported previously [Minyaev et al. (2018a). Acta Cryst. C74, 590–598]. In (1), all three bis(2,6-diisopropylphenyl) phosphate ligands display the terminal κ1 O-coordination mode. All of the hydroxy H atoms are involved in O—H...O hydrogen bonding, exhibiting four intramolecular and two intermolecular hydrogen bonds. Photophysical studies have demonstrated luminescence of (1) with a low quantum yield.

A series of heterometallic carboxylate 1D polymers of the general formula [LnIIICd2(piv)7(H2O)2]n·nMeCN (LnIII = Sm (1), Eu (2), Tb (3), Dy (4), Ho (5), Er (6), Yb (7), piv = anion of trimethylacetic acid) was synthesized and structurally characterized. The use of CdII instead of ZnII under similar synthetic conditions resulted in the formation of 1D polymers, in contrast to molecular trinuclear complexes with LnIIIZn2 cores. All complexes 1–7 are isostructural. The luminescent emission and excitation spectra for 2–4 have been studied, the luminescence decay kinetics for 2 and 3 was measured. Magnetic properties of the complexes 3–5 and 7 have been studied, 4 and 7 exhibited the properties of field-induced single-molecule magnets in an applied external magnetic field. Magnetic properties of 4 and 7 were modelled using results of SA-CASSCF/SO-RASSI calculations and SINGLE_ANISO procedure. Based on the analysis of the magnetization relaxation and the results of ab initio calculations, it was found that relaxation in 4 predominantly occurred by the sum of the Raman and QTM mechanisms, and by the sum of the direct and Raman mechanisms in the case of 7.

Complexes [(1,2,4-Ph3C5H2)2NdCl2K(THF)2]2 (Nd1), {[1,2-Ph2-4-(4-MeOC6H4)C5H2]2NdCl2K(THF)2}2 (Nd2), {[1,2-Ph2-4-(2-MeOC6H4)C5H2]2NdCl2[K(THF)4]}(THF)0.5 (Nd3), and [(1,2,4-Ph3C5H2)2TbCl2K]2 (Tb1) h...

A procedure for the chemical immobilization of a new ZnII–EuIII heterobimetallic complex in the SiO2 aerogel matrix has been developed. In this Zn–Eu complex, a peripheral non-luminescent Zn ion acts as a binder to a silica matrix and prevents direct interaction of rare-earth ions with OH− and NH− groups in the silica matrix, which would have a detrimental effect on the luminescence of lanthanides. The procedure includes the synthesis of complexes, co-gelation of the obtained complex with SiO2 sol, the washing of lyogels, and their subsequent supercritical drying in CO2. The composition and properties of the obtained aerogels were investigated using a low-temperature nitrogen adsorption technique, helium pycnometry, FTIR, Raman, UV–visible, and luminescence spectroscopy, XPS, PXRD, SEM, TEM, TGA combined with mass spectrometry, and small-angle neutron scattering. The aerogels modified with the ZnII–EuIII complex demonstrated strong red luminescence upon excitation with UV light.

Novel mononuclear lanthanide thiocyanates with 2,2′;6′,2″-terpyridine (terpy), namely isomorphic complexes [Ln(terpy)2(NCS)3] (Ln = Y, Eu, Tb and Dy) were prepared and studied. The effective luminescence sensitization of the Eu, Tb and Dy ions owing to the terpy ligands was observed and corresponding values of the absolute quantum yields were determined. The influence of structural features of the complexes studied on their luminescent properties was analyzed. Slow magnetic relaxation indicating SMM behavior was found for Dy complex.

A series of bis-cyclometalated iridium(III) complexes with 2-arylphenanthroimidazole “antenna” ligands containing electron-donor or withdrawing substituents and a more flexible ancillary aromatic β-diketone bearing the “anchoring” carboxymethyl function has been prepared. Thorough X-ray study of the complexes revealed significant structural strains caused by bulky cyclometalated 2-arylphenanthroimidazoles resulting in dramatic distortions of the iridium octahedron and even in twist of the phenanthrene fragment. The crystal data were corroborated by gas-phase DFT calculations whereby the geometry of the complexes was distorted in the same way. While redox potentials, absorption and emission maxima of the complexes displayed expected change upon the variation of the electron-donating ability of the cyclometalated ligands, the complexes readily exchanged the bidentate ancillary ligand in the presence of a negligible amount of protons that was inspected in solution by UV-Vis spectroscopy. Moreover, after hydrolysis of the carboxymethyl group the resulting complexes readily react with the surface of titanium dioxide giving unique binuclear structures in which the deprotonated carboxy group of the coordinated β-diketonate binds the second bis-cyclometalated unit by forming a four-membered metallacycle. Though the enhanced reactivity of the complexes is contrary to the common idea of the high inertness of iridium(III) compounds it can be seen as a consequence of the interplay between the steric hindrance induced by the ligands and the strong preference of the iridium(III) ion for octahedral geometry. This study demonstrates that the use of bulky ligands provides access to light-harvesting iridium(III) complexes with required extent of lability which may be promising as photocatalysts and biologically active molecules.

Heterometallic {Zn-Ln}-complexes [Zn2Ln(OH)(Piv)4(NO3)2(pyzphen)2], where Ln is Eu (1), Gd (2) or Tb (3), Piv- is an anion of pivalic acid and pyzphen is pyrazino[2,3-f][1,10]phenanthroline, were synthesized. Crystallographic cell parameters and XRPD study show the compounds to be isostructural. The crystal structure of 3 was determined by single crystal X-ray analysis. The complexes contained two pyzphen ligands coordinated by Zn ions. Inter- and intra-molecular interactions between aromatic fragments of pyzphen resulted in the formation of a stack structure. The triplet state energy of pyzphen in complex 2 is 22200 cm−1. Analysis of the luminescence of 1 and 3 showed a low efficiency of ligand-to-metal energy transfer.

The crystal structure of the complex {Eu[O2P(O-2,6-iPr2C6H3)2]3(CH3OH)5}·CH3OH, which exhibits intra- and inter­molecular O—H⋯O hydrogen bonding, and its luminescent properties have been studied., The mononuclear title complex, [Eu(C24H34O4P)3(CH4O)5]·CH4O, (1), has been obtained as a minor product in the reaction between EuCl3(H2O)6 and lithium bis­(2,6-diiso­propyl­phen­yl) phosphate in a 1:3 molar ratio in a methanol medium. Its structure exhibits monoclinic (P21/c) symmetry at 120 K and is isostructural with the La, Ce and Nd analogs reported previously [Minyaev et al. (2018a ▸). Acta Cryst. C74, 590–598]. In (1), all three bis­(2,6-diiso­propyl­phen­yl) phosphate ligands display the terminal κ1 O-coordination mode. All of the hy­droxy H atoms are involved in O—H⋯O hydrogen bonding, exhibiting four intra­molecular and two inter­molecular hydrogen bonds. Photophysical studies have demonstrated luminescence of (1) with a low quantum yield.

A new approach to design “antenna-ligands” to enhance the photoluminescence of lanthanide coordination compounds has been developed based on a π-type ligand—the polyphenyl-substituted cyclopentadienyl. The complexes of di-, tri-, and tetraphenyl cyclopentadienyl ligands with Tb and Gd have been synthesized and all the possible structural types from mononuclear to di- and tetranuclear complexes, as well as a coordination polymer were obtained. All types of the complexes have been studied by single-crystal X-ray diffraction and optical spectroscopy. All terbium complexes are luminescent at ambient temperature and two of them have relatively high quantum yields (50 and 60%). Analysis of energy transfer process has been performed and supported by quantum chemical calculations. The role of a low-lying intraligand charge transfer state formed by extra coordination with K+ in the Tb3+ ion luminescence sensitization is discussed. New aspects for design of lanthanide complexes containing π-type ligands with desire...

A series of complexes [(4,4′-diMe-2,2′-bpy)2Zn2Eu2(NO3)4(naphac)6] (1), [(4,4′-dtb-2,2′-bpy)2Zn2Ln2(NO3)2(naphac)8] Ln = Eu (2), Tb (3), [(Py)2Zn2Ln2(naphac)10] Ln = Eu (4), Nd (5), Gd (6), Tb (7), Dy (8), [(Py)2Zn2Tm2(NO3)2(naphac)8] (9) (where naphac is the anion of 1-naphthylacetic acid, 4,4′-diMe-2,2′-bpy = 4,4′-dimethyl-2,2′-bipyridine, 4,4′-dtb-2,2′-bpy = 4,4′-di-tert-butyl-2,2′-bipyridine, Py = pyridine) were synthesized and structurally characterized. Capabilities of several synthetic routes for obtaining the title compounds were evaluated. Molecular and crystal structures as well as luminescence properties of obtained heterometallic complexes are reported and discussed in detail.

A family of brightly luminescent dinuclear complexes of [Cu(μ2-X)(N^N)]2 type (X = I or SCN) has been synthesized in 76–90% yields by the reaction of bis(2-pyridyl)phosphine oxides (N^N) with the corresponding Cu(I) salts. The X-ray diffraction study reveals that the Cu2I2 core of the [Cu(μ2-I)(N^N)]2 complexes has either a butterfly- or rhomboid-shaped structure, while the eighth-membered [Cu(SCNNCS)Cu] ring in the [Cu2(SCN)2(N^N)]2 complexes is nearly planar. In the solid state, these compounds exhibit a strong green-to-yellow emission (λemmax = 536–592 nm) with high PLQYs (up to 63%) and short lifetimes (1.9–10.0 μs). The combined photophysical and DFT study indicates that the ambient-temperature emission of the complexes obtained can be assigned to the thermally activated-delayed fluorescence (TADF) from the 1(M + X)LCT excited state, while at 77 K, phosphorescence from the 3(M + X)LCT state is likely observed.

New 1D polymers with general formula [Ln(4-phbz)3]n, where Ln = Sm, Eu, Gd, Tb, Dy, Ho, and 4-phbz is the 4-phenylbenzoate anion, were synthesized by the reaction of Ln(NO3)3∙xH2O, 4-phenylbenzoic acid and dry KOH. Thermal analysis shows that [Eu(4-phbz)3]n is thermally stable in an inert atmosphere up to 350 oC and melts at 297 oC. It was shown that the 4-phenylbenzoate anion (E(T1) ~ 22500 cm-1) in [Ln(4-phbz)3]n can play the role of an antenna and sensitize the luminescence of Eu3+ and Tb3+ ions. Analysis of magnetic data of the [Gd(4-phbz)3]n complex reveals weak antiferromagnetic coupling between Gd3+ ions (J = -0.053 cm-1). The [Dy(4-phbz)3]n compound shows noticeable frequency-dependent χ'' signals indicating slow magnetic relaxation and single-molecule magnet behavior with the energy barrier of ΔEeff/kB = 5 K.

Luminescent composite materials based on linear polyethylene doped by a well dispersed tetrakis dibenzoylmethanate europium complex have been developed. The anion of the latter serves as an efficient light harvesting antenna and possesses the desired photophysical properties. The targeted modification of the Eu complex, namely introduction of a long hydrocarbon chain into the tetraalkylammonium cation [RNEt3]+, has ensured the compatibility of the complex with the polyethylene matrix. The [RNEt3]+ cation has been obtained by using long-chained 1-iodoalkanes synthesized via the Nd-catalyzed ethylene oligomerization process. The photophysical properties and the homogeneity of the obtained composites have been controlled by optical spectroscopy, luminescence intensity mapping as well as scanning electron microscopy.

The possibility of using a single light-emitting layer consisting of newly synthesized fluorescent small organic molecules of D–A–π–A type incorporated into a conductive matrix together with an electron conductive Alq3 layer in order to form radiation in candle light-style OLEDs was shown for the first time. A record low color temperature of 1722 K OLED radiation was achieved, which is by 80 K lower than that of the best devices reported previously.

The systematic series of Zn–Ln trinuclear carboxylate molecular complexes of general formula [Zn2Ln(NO3)(phbz)6(L)2] (Ln = Eu, Gd, and Tb, where phbz is the anion of 4-biphenylcarboxylic acid, and L is pyridine, 2,3-lutidine or 2,2′-bipyridine) were synthesized. It was found that [Zn2Eu(NO3)(phbz)6(py)2] can be obtained in two phases, crystallized in the triclinic P and monoclinic P21/n space groups, and solvated acetonitrile molecules are able to prevent the formation of intermolecular π–π stacking interactions between the aromatic fragments of [Zn2Eu(NO3)(phbz)6(py)2]. Heterometallic Zn2Eu and Zn2Tb compounds possess bright metal-centered luminescence with quantum yields up to 62%. The influence of an N-donor ligand type on the efficiency of luminescence sensitization was studied.

Heterometallic complex [Cd2Eu(bzo)6(NO3)(MeCN)2(THF)2].2EtOH was synthesized by the reaction of Cd(NO3)2·4H2O and Eu(NO3)3·6H2O with potassium 3,5-di-tert-butylbenzoate (Hbzo). N-Donors (L) could replace solvents in the Cd coordination environment without modifying the stable metal core {Cd2Eu(bzo)6(X)} (X = NO3 or bzo). The presence of pyrazine (pz) in the reaction mixture could result in the formation of either molecular [Cd2Eu(bzo)6(NO3)(pz)2(EtOH)2] or 1D-polymeric [Cd2Eu(bzo)6(NO3)(pz)(H2O)2]n complex, depending on the Cd : L molar ratio (1 : 15 and 1 : 8, respectively). Addition of bridging N-donors 4,4′-bipyridine (4,4′-bipy) and 1,2-bis(2-pyridyl)ethylene (bpe) (Cd : L = 1 : 2) gave the [Cd2Eu(bzo)7(4,4′-bipy)(H2O)2]n and [Cd2Eu(bzo)7(bpe)(H2O)2]n polymers, respectively. 4-Methyl-2-aminopyridine (ampy) gave only molecular compound [Cd2Eu(bzo)7(ampy)2(EtOH)(H2O)] (Cd : L = 1 : 3). The structures of all the resulting compounds were studied by single crystal X-ray diffraction analysis. Photoluminescent properties were studied for solid samples of the synthesized compounds. The effect of the N-donor ligand geometry and the Eu…Eu distance on the lifetime of the Eu3+ atom’s 5D0 excited state is discussed.

Varying the temperature of the reaction of [{Cd(pfb)(H2O)4}+n·n(pfb)−], [Ln2(pfb)6(H2O)8]·H2O (Hpfb = pentafluorobenzoic acid), and 1,10-phenanthroline (phen) in MeCN followed by crystallization resulted in the isolation of two type of products: 1D-polymers [LnCd(pfb)5(phen)]n·1.5nMeCN (Ln = Eu (I), Gd (II), Tb (III), Dy (IV)) which were isolated at 25 °C, and molecular compounds [Tb2Cd2(pfb)10(phen)2] (V) formed at 75 °C. The transition from a molecular to a polymer structure becomes possible because of intra- and intermolecular interactions between the aromatic cycles of phen and pfb from neighboring tetranuclear Ln2Cd2 fragments. Replacement of cadmium with zinc in the reaction resulted in molecular compounds Ln2Zn2 [Ln2Zn2(pfb)10(phen)2]·4MeCN (Ln = Eu (VI), Tb (VIII), Dy (IX)) and [Gd2Zn2(pfb)10(H2O)2(phen)2]·4MeCN (VII). A new molecular EuCd complex [Eu2Cd2(pfb)10(phen)4]·4MeCN (X)] was isolated from a mixture of cadmium, zinc, and europium pentafluorobenzoates (Cd: Zn:Ln = 1:1: 2). Complexes II-IV, VII and IX exhibit magnetic relaxation at liquid helium temperatures in nonzero magnetic fields. Luminescent studies revealed a bright luminescence of complexes with europium(III) and terbium(III) ions.

Organophosphate-chloride complexes [{(2,6-iPr2C6H3-O)2POO}2LnCl(CH3OH)4]&middot, 2CH3OH, Ln = Nd (1), Eu (2), Gd (3), and Tb (4) have been obtained and structurally characterized. Their reaction with 2,2&prime, 6&prime, 2&Prime, terpyridine leads to the formation of 1:1 adducts ([{(2,6-iPr2C6H3-O)2POO}2LnCl(terpy)(H2O)2(CH3OH)], Ln = Eu (5), Gd (6), Tb (7) with exception of Nd, where tris-diisopropylphenylphosphate complex [{(2,6-iPr2C6H3-O)2POO}3Nd) (terpy)(H2O)(CH3OH)] (8) was obtained due to the ligand metathesis. A bright luminescence observed for the Eu and Tb organophosphate complexes is the first example of an application of organophosphate ligands for 4f-ions luminescence sensitization. Photophysical properties of all complexes were analyzed by optical spectroscopy and an energy transfer scheme was discussed. A combination of two types of ligands into the coordination sphere (phosphate and phenanthroline) allows designing the Eu surrounding with very high intrinsic quantum yield QEuEu (0.92) and highly luminescent Ln complexes for both visible and near-infrared (NIR) regions.