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Three dinuclear lanthanide complexes are achieved by using H2salen or H2salen/acac ligands (H2salen = N,N′-ethylenebis(salicylideneimine), acac = acetylacetonate). They are homodinuclear [Er2(salen)3] (1), [Yb2(salen)2(acac)2] (2), and heterodinuclear geometrical [ErYb(salen)2(acac)2] (3). The structures of complexes were determined by single crystal X-ray crystallographic studies and their photophysical properties were investigated. The homonuclear Yb2 complex exhibits characteristic metal-centered NIR emission. The geometric ErYb isomer exhibits ‘dual emissions’ from both erbium(iii) and ytterbium(iii) ions. There was no detectable photoluminescence in the Er2 complex, not only in solid state but also in solvent. [ABSTRACT FROM AUTHOR]

Herein, a series of ionic mononuclear Cu(I) complexes, [Cu(phen)(bdppmapy)]Cl (1a), [Cu(phen)(bdppmapy)]Br (2a), [Cu(phen)(bdppmapy)]I (3a), [Cu(phen)(bdppmapy)]SCN (4a), [Cu(Dpq)(bdppmapy)]Cl (1b), [Cu(Dpq)(bdppmapy)]Br (2b), [Cu(Dpq)(bdppmapy)]I (3b) and [Cu(Dpq)(bdppmapy)]SCN (4b) {phen = [1,10]phenanthroline; Dpq = pyrazino[2,3-f][1,10]-phenanthroline; bdppmapy = N,N-bis((diphenylphosphino)methyl)-2-pyridinamine} have been synthesized and characterized by using IR, NMR, elemental analysis, single crystal X-ray diffraction analysis, fluorescence spectroscopy methods, and UV-vis and terahertz (THz) time-domain absorption spectroscopy. Their crystal structures were elucidated by X-ray crystallography and their photophysical properties were investigated in detail. All the above complexes exhibit a 1D to 3D supramolecular structure which is linked together by intermolecular weak interaction forces and hydrogen bonds. By regulating ligands and anions, the emission wavelengths of these complexes are quite different in the range from 533 nm to 604 nm. Theoretical calculations and photophysical properties indicate that luminescence is derived from metal-to-ligand charge transfer (MLCT) excited states. In the meantime, the results of calculations show that the stabilization of the increased conjugation of the ligand-based π* orbital is ascribed to the observed bathochromic-shift in the MLCT transitions. [ABSTRACT FROM AUTHOR]

Herein, six new [Cu(N^N)(P^P)]+/0 complexes with different N-ligands and counteranions, [Cu2(dmp)2(bdppmapy)I2] (1), [Cu2(dmp)2(bdppmapy)(CN)2]·3CH3OH (2), [Cu(dmp)(bdppmapy)](BF4) (3), [Cu(dmp)(bdppmapy)](ClO4) (4), [Cu(phen)(bdppmapy)](BF4) (5), and [Cu(phen)(bdppmapy)](ClO4) (6), have been synthesized and characterized (bdppmapy = N,N-bis[(diphenylphosphino)methyl]-2-pyridinamine, phen = 1,10-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline). Single-crystal X-ray diffraction showed that different counteranions help to construct various stacking modes 1D–3D via weak interactions, such as π–π, C–H⋯π and C–H⋯X (X = F, O). Photophysical analysis showed they have yellow-green to yellow-orange emission within a range of 504–569 nm, and excellent photophysical properties with quantum yields from 2.6% (2) to 77% (4). In this study, these results indicate that the π–π stacking and C–H⋯X (X = O, F) weak interactions help to enhance the rigidity of these structures and further improve their luminescence quantum yields. In addition, we have explored the nature of the complexes emission mechanism through theoretical calculations. According to DFT/TD-DFT calculations, the luminescence behavior of the six complexes is ascribed to MLCT or (M + X)LCT. THz spectra were applied to explore the relationship between weak interactions and luminescence. These results have opened up a new direction in the characterization of the properties of luminescent materials. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs), self-assembled from metal ions with organic ligands, are well known for their intriguing framework topology, permanent porosity, and tunable optical properties and have shown great promise for a good number of applications. Over the past few years, luminescent MOFs have attracted growing attention, especially for developing various luminescent sensors, by virtue of their excellent selectivity and high sensitivity. In this feature article, we highlight some of the recent significant progress in this active research field, and provide a comprehensive review on luminescent MOFs as sensory materials for diverse sensing applications including for metal ions, anions, small molecules and gases, nitroaromatics and explosives, temperature, as well as other aspects. [ABSTRACT FROM AUTHOR]

On the basis of the 3-(pyrazin-2-yl)-1H-pyrazole-5-carboxylic acid (H2L) ligand, four new polymers [Cu2(L2−)2] (1), [Zn3(L2−)2(H2O)4Cl2]n (2), [Pb(HL−)Cl]n (3), and {[Ni(L2−)(H2O)]·(H2O)}n (4) have been synthesized under solvothermal conditions. Polymer 1 possesses a discrete (0D) binuclear structure, which is further formed into a three-dimensional (3D) supramolecular structure by hydrogen bonding and π⋯π stacking interactions. Polymers 2 and 3 display one-dimensional (1D) infinite chain structures, which further extend into 3D supramolecular structures through hydrogen bonding interactions. Polymer 4 features two-dimensional (2D) layers which can form a 3D supramolecular architecture via interlayer hydrogen bonds. The ligand in the four polymers adopts different coordination modes for constructing versatile structures. Moreover, luminescence sensing study shows that polymer 2 is a promising luminescent sensor for the detection of Cu2+, Co2+ and Fe3+via drastic luminescence quenching in aqueous solution with high efficiency. The quenching constants KSV for Cu2+, Co2+ and Fe3+ are 6.35 × 103 M−1, 8.70 × 103 M−1 and 1.62 × 104 M−1, respectively. What's more, 1–4 with electrochemical luminescence (ECL) properties show high intensity in N,N-dimethylformamide (DMF) solution and high thermal stability. [ABSTRACT FROM AUTHOR]

In this paper, a series of Eu3+/Tb3+ doped La3Ga5SiO14 (LGS:Eu3+, Tb3+) phosphors with excellent performance have been synthesized by high-temperature solid-phase method. The effects of Eu3+ and Tb3+ doping in LGS on the host lattice were analyzed by X-ray diffraction (XRD). X-ray photoelectron spectroscopy (XPS) proved that the Eu3+ and Tb3+ ions were successfully doped into the LGS host. The doped Eu3+/Tb3+ ions only occupy the eight-coordinated La3+ sites. The concentration quenching points of LGS:Eu3+ and LGS:Tb3+ phosphors were determined to be 0.16 and 0.18, respectively. The luminescence performance and fluorescence lifetime of LGS:Eu3+, Tb3+ were studied. LGS:Eu3+, Tb3+ phosphors successfully realized Tb3+ → Eu3+ energy transfer to enhance Eu3+ luminescence. The energy transfer mechanism is speculated on using the experimental results. The energy transfer efficiency from Tb3+ to Eu3+ is about 66.83% in La2.46Tb0.18Eu0.36Ga5SiO14. The LGS:Eu3+, Tb3+ phosphors can achieve tunable luminescence by controlling the doping concentrations of Eu3+ and Tb3+. The ΔE is calculated to be 0.2567 eV for the La2.70Eu0.12Tb0.18Ga5SiO14 phosphor. [ABSTRACT FROM AUTHOR]

The synthesis of four heteroleptic dinuclear Cu(I) complexes bearing tetraphosphine and diimine ligands was reported. Complexes 1–3 were successfully obtained through microwave synthesis while complex 4 was synthesized through traditionally stirring at room temperature. These complexes are listed as follows: [Cu2(Dpq)2(dppeda)](ClO4)2·1.5CH2Cl2 (1), [Cu2(neo)2(dppeda)](ClO4)2·1.3CH2Cl2·1.7C4H10O (2), [Cu2(batho)2(dppeda)](ClO4)2·C4H10O (3), and [Cu2(batho)2(dpppda)](ClO4)2·3CH2Cl2 (4) {(Dpq = pyrazino[2,3-f][1,10]phenanthroline, batho = 4,7-diphenyl-1,10-phenanthroline, neo = 2,9-dimethyl-1,10-phenanthroline, dppeda = N1,N1,N2,N2-tetrakis[(diphenylphosphino)methyl]-1,2-ethanediamine, and dpppda = N1,N1,N4,N4-tetrakis[(diphenylphosphino)methyl]-1,4-benzenediamine}. Their crystal structures have been elucidated by X-ray crystallography and their photophysical properties have been investigated in detail. Photophysical studies and time domain density functional theory (TD-DFT) calculations show that the luminescence performance of these four complexes is ascribed to metal-to-ligand charge transfer (MLCT) mixed with ligand-to-ligand charge transfer (LLCT), and complex 2 shows green emission at 574 nm with the highest quantum yield of up to 52.80%. In addition, the research of photoluminescence properties under the guidance of terahertz spectroscopy technology leads to the preliminary discovery of a correlation between crystal packing and luminescence. It is found that the terahertz spectrum and absorption peak are strongly interdependent on C–H⋯π and π⋯π interactions, and the external weak interactions have negative effects on the luminescence performance. Herein, we predict that the terahertz spectroscopy analysis establishes a bridge between weak interactions (C–H⋯π and π⋯π interactions) and the photoluminescence properties, and puts forward a problem that should be noticed in designing Cu(I) complexes. [ABSTRACT FROM AUTHOR]

A trinuclear cyanide-bridged luminescent compound, trans-RuII(DMAP)4(CN)2[(PY5Me2)Mn]2[PF6]4 (1-R), and its oxidation product, ferromagnetic trans-RuIII(DMAP)4(CN)2[(PY5Me2)Mn]2-[PF6]5 (1-O), were synthesized and fully characterized. This is the first example of a molecular material showing a redox-controlled transformation between fluorescence and ferromagnetism. [ABSTRACT FROM AUTHOR]

The precise and real-time monitoring of localized pH changes is of great importance in many engineering and environmental fields, especially for monitoring small pH changes in biological environments and living cells. Metal–organic frameworks (MOFs) with their nanoscale processability show very promising applications in bioimaging and biomonitoring, but the fabrication of nanoscale MOFs is still a challenge. In this study, we synthesized a nanoscale mixed-lanthanide metal–organic framework by a microemulsion method. The morphology and size of the NMOF can be simply adjusted by the addition of different amounts of the CTAB surfactant. This NMOF exhibits significant pH-dependent luminescence emission, which can act as a self-referenced pH sensor based on two emissions of Tb3+ at 545 nm and Eu3+ at 618 nm in the pH range from 3.00 to 7.00. The MTT assay and optical microscopy assay demonstrate the low cytotoxicity and good biocompatibility of the nanosensor. [ABSTRACT FROM AUTHOR]

By using different N-donor organic species as additional auxiliary ligands with structure-directing roles, four three-dimensional (3D) calcium-based coordination complexes, [Ca(dbt)(H2O)]n1, [Ca(H-dbt)2(5,5′-dmbpy)2]n2, (4,4′-bpy)0.5[Ca(dbt)(H2O)2]n3, and (H2-dib)[Ca3(dbt)4(H2O)4·2H2O]n4 (H2-dbt = 2,5-dibromoterephthalic acid, 2,2′-bpy = 2,2′-bipyridine, 5,5′-dmbpy = 5,5′-dimethyl-2,2′-bipyridine, 4,4′-bpy = 4,4′-bipyridine, dib = 1,4-di(1H-imidazol-1-yl)benzene), have been successfully synthesized under similar solvothermal conditions and structurally characterized. The organic amine molecules play different roles in the formation of four different metal–organic skeletons with diverse structural topologies, in which complexes 1–3 are neutral, and 4 comprises a negatively charged framework with diprotonated dib as the counterion. Complex 1 features a 3D (6,6)-connected framework structure composed of edge-sharing 1D Ca–O–Ca inorganic chains and dbt ligands. The 2,2′-bpy molecule plays an important role in the synthesis of 1 as the structure-directing agent (SDA). Complex 2 shows a 3D 2-fold interpenetrated diamondoid framework (dia, 66) formed by single metal nodes via linear H-dbt anions and bidentate chelating 5,5′-dmbpy ligands, while complex 3 exhibits a 3D noninterpenetrated pcu network with {412·63} topology constructed from binuclear [Ca2(CO2)4] secondary building units and two types of dbt ligands, in which 4,4′-bpy molecules are ordered within the 3D neutral calcium-based framework as template and space filling agents. Complex 4 is a unique (4,4,4,4,5)-connected 5-nodal topology net, in which the diprotonated dib molecules provide space filling to balance the negatively charged framework. In addition, the thermal stability and the fluorescence properties of complexes 1–4 have been investigated. [ABSTRACT FROM AUTHOR]

A near-infrared luminescent metal–organic framework Nd0.866Yb0.134BTB was developed as a self-calibrated thermometer in the physiological range. Its features include high sensitivity and resolution, and good biocompatibility, making such a material useful for biomedical applications. [ABSTRACT FROM AUTHOR]

Nine IIB group complexes, [ZnL1Cl2] (Zn1), [CdL1Cl2]2 (Cd1), [HgL1Cl2] (Hg1), [ZnL2Cl2] (Zn2), [CdL2Cl2] (Cd2), [HgL2Cl2] (Hg2), [ZnL3Cl2] (Zn3), [CdL3Cl2] (Cd3) and [HgL3Cl2] (Hg3), have been synthesized from the corresponding ortho-(6-methoxy-pyridyl)(CH=NAr) (where Ar = 2,6–iPr2C6H3, L1; 4–MeC6H4, L2; 2–OMeC6H4, L3) Schiff base and structurally characterized by elemental analysis, FT-IR, 1H NMR and X-ray single-crystal analysis. Crystallographic studies reveal that the center metal of the complexes adopts a distorted tetrahedron geometry (except for Cd1 and Cd3, which display square pyramidal geometry) and C–H…Cl hydrogen bonds and π…π stacking interactions contribute to three-dimensional supramolecular structures. The series of complexes exhibit tunable luminescence from blue, through green, to light yellow by varying the temperature (298 K and 77 K), both in solution and in the solid state. Moreover, the quantum yields range from 0.027 to 0.422, and decrease according to the order of the periodic table (Zn ＞ Cd ＞ Hg). These results indicate that the center atom of the complexes leads to the geometry differences and hence to the tunable luminescence properties. Because Zn1–Zn3 exhibited higher molar extinction coefficients and a distinct absorption region, they were employed as co-sensitizers in ruthenium dye N719-sensitized photoanodes to deliver light-electricity efficiency enhancement, being assembled with counter-electrodes and electrolyte to prepare ZnX/N719 (where ZnX = Zn1, Zn2 and Zn3) co-sensitized dye sensitized solar cell (DSSC) devices. The prepared co-absorbent could overcome the deficiency of N719 absorption in the low-wavelength region of the visible spectrum, and offset competitive visible-light absorption of I3−. Application of these prepared complexes in N719-sensitized solar cells enhanced their performance by 10–36%, which indicated a potential application of these types of complexes in DSSCs. [ABSTRACT FROM AUTHOR]

Poly(methylmethacrylate) (PMMA) doped with Tb-based imidazole derivative coordination polymer {[Tb3(L)(μ3-OH)7]·H2O}n (1) (L = N,N′-bis(acetoxy)biimidazole) was synthesized and its photophysical properties were studied. The L′ (L′ = N,N′-bis(ethylacetate)biimidazole) ligand was synthesized by an N-alkylation reaction process followed by ester hydrolysis to produce ligand L. Polymer 1 and ligand L′ have been characterized by 1H NMR and IR spectroscopy, elemental analysis, PXRD and X-ray single-crystal diffraction. Coordination polymer 1 is the first observation of a CdCl2 structure constructed with hydroxy groups and decorated by ligand L in lanthanide N-heterocyclic coordination polymers. In the 2D layered structure of 1, each Tb3 metal center is connected with three Tb1 and three Tb2 metal centers by seven hydroxyl groups in different directions, resulting in a six-membered ring. After doping, not only the luminescence intensity and lifetime enhanced, but also their thermal stability was increased in comparison with 1. When 1 was doped into poly(methylmethacrylate) (1@PMMA), polymer film materials were formed with the PMMA polymer matrix (w/w = 2.5%–12.5%) acting as a co-sensitizer for Tb3+ ions. The luminescence intensity of the Tb3+ emission at 544 nm increases when the content of Tb3+ was 10%. The lifetime of 1@PMMA (914.88 μs) is more than four times longer than that of 1 (196.24 μs). All τ values for the doped polymer systems are higher than coordination polymer 1, indicating that radiative processes are operative in all the doped polymer films. This is because PMMA coupling with the O–H oscillators from {[Tb3(L)(μ3-OH)7]·H2O}n can suppress multiphonon relaxation. According to the variable-temperature luminescence (VT-luminescence) investigation, 1@PMMA was confirmed to be a stable green luminescent polymer film material. [ABSTRACT FROM AUTHOR]

Two rare 2D Ga/In-based coordination polymers in which one metal center coexists with three distinct aromatic ligands were synthesized. Helical channels along the 21 screw axis are exhibited to form a hcb net. The compounds exhibit tunable fluorescence from blue, green, white to yellow light by varying the temperature and solvents. [ABSTRACT FROM AUTHOR]