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We report that the tail modulation of Stokes pulses in the high-energy stimulated Brillouin scattering pulse compression can be suppressed by controlling effective pulse width of the pump. It is shown through numerical simulations and validated experimentally that the effective pulse width is an appropriate parameter, which determines the generation of tail modulation. The effective pulse width broaden as the increase of energy. This mechanism leads to the amplification of Stokes tail edge and it is the cause of tail modulation.

We propose a method based on Brillouin amplification, which reshapes the Gaussian pulse generated from a $Q$ -switched laser into the flat-top waveform. The numerical simulations show that the reshaped waveform depends on Stokes pulse width and energy, and optimum conditions for a flat waveform are also investigated. It is demonstrated experimentally by the independent two-cell filled with FC-40 liquid. In the experiment, the flat-top waveform pulses with width from 9.1 to 13.3 ns and continuously adjustable energy from 90 to 210 mJ are obtained at the wavelength of 1064 nm. The pulses with flat-top waveform and high energy are achieved by injecting a small Stokes seed into the Brillouin amplifier, which is a novel method to obtain high-energy flat-top laser pulses.

Based on azabicyclo ligands, four 3D supramolecular lanthanide complexes have been synthesized through hydro(solvo)thermal reactions, generally formulated as [Dy(bipy) (NO3)3]2 (1·Dy), [Dy(bipy)2(NO3)3] (2·Dy), [Dy2(bpdc)3(DMF)(H2O)]2·(DMF)10(H2O) (3·Dy) and [Eu4(bpdc)6(CH3NH2)3(DMSO)(H2O)] (4·Eu) (Bipy = 2,2′-bipyridine; H2bpdc = 2,2′-bipyridine-5,5′-dicarboxylic acid, DMF = N,N-dimethylformamide), and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis and powder X-ray diffraction (PXRD). There are three kinds of hydrogen bonding, C2–H2A⋯O6, C4–H4A⋯O4 and C8–H8A⋯O8 along the a/c, b, c axis, respectively in complex 1·Dy. They connect the 1·Dy complex into a 3D 6-connected pcu supramolecular network. 2·Dy is connected into a 3D network with 8–connected bcu architecture by two kinds of hydrogen bonding: C2–H2A⋯O1 and C9–H9A⋯O3. In order to connect the polymer to form a 3D complex, H2bpdc has been chosen in the synthesis and design of the crystal. In the network of 3·Dy, two kinds of Dy(III) cations in different coordination models construct the different binuclear [Dy2O14(DMF)2] and [Dy2O12(H2O)2], and further form the (4,4,6)-connected 3D architecture. The isostructural complex 4·Eu has been synthesised simultaneously. The property of luminescence in solid state or different solvents of the four complexes has been studied in detail. The four complexes show the unique emission peaks of lanthanide cations. Futhermore, in 3·Dy and 4·Eu, the ligand shows a rare bimodal emission, which can sensitize the emission of europium cations as an “antenna effect”, and the shorter one keeps its blue emission though coordinated with Dy(III) cations. Based on the synthesis of green or red color materials, multicolored photoluminescence tuning has been studied in detail through growth of a series of bimetallic complexes, the crystal formula as [Dy2nEu′2−2n(bpdc)3(DMF)(H2O)] (M-1–M-9; 0 < n < 1). We achieved dichromatic fine-tuning among the triangle region of red, green and white. The linear dependence of the emissions has been analyzed, and the mathematical matrix model is useful to calculate the ratio and excitation wavelength for a given color in need.

The mononuclear Zn(Ⅱ) complex [Zn(2,6-PDA)(phen)H2O]·H2O (1) and binuclear Cu(Ⅰ) complex{[Cu(μ-Ⅰ)(phen)H2O]·H2O}2 (2) (2,6-H2PDA=2,6- pyridinedicarboxylic acid，phen=1,10- phenanthroline monohydrate) have been prepared with hydro-thermal synthesis method. These complexes have been characterized with single-crystal X-ray, elemental analysis, and IR spectroscopy. The fluorescence spectra of 1 and 2 are studied in solid-state and dimethyl sulfoxide (DMSO) solution. The maximum absorption peak of 1 and 2 are at 253 nm and 242 nm respectively, which are red shift to that of the phen ligand with inceased intensity. It may be assigned to the intraligand π→π* transition of the phen ligand that is modified by the Zn(Ⅱ) or Cu(Ⅰ) ions. On the basis of the coordination, the absorption of organic ligands in the ultraviolet region is increased, which is better for the energy absorption of the ligand. 1 and 2 all showed blue light emission. The emission peak of 1 and 2 have experienced a red shift (ca. 55 and 23 nm) in the solid state (λem = 407, 434, 467 nm for 1, 442, 469, 501 nm for 2) compared to in DMSO solution (λem = 361, 379, 392 nm for 1, 422, 443, 461 nm for 2). The red shift phenomenon can be attributed to the π-stacking of the aromatic rings and other intermolecular Interactions in these molecules in the solid state. Especially, the strong Cu(Ⅰ)…Cu(Ⅰ) interaction of 2 can decrease the HOMO—LUMO energy gap with the red-shifted emission wavelength.

This work reports on two new complexes with the general formula [Cd3(IBA)3(Cl)2(HCOO)(H2O)]n (1) and {[Cd1.5(IBA)3(H2O)6]·3.5H2O}n (2), which can be synthesized by the reaction of Cd(II) with rigid linear ligand 4-HIBA containing imidazolyl and carboxylate functional groups [4-HIBA = 4-(1H-imidazol-1-yl)benzoic acid]. Single-crystal X-ray diffraction analyses indicate that complex 1 is a 2D "wave-like" layer structure constructed from trinuclear units and complex 2 is just a mononuclear structure. Surprisingly, both complexes 1 and 2 appear as a 3D supramolecular network via intermolecular hydrogen bonding interactions. What's more, due to their strong UV-visible absorption, 1 and 2 can be employed as co-sensitizers in combination with N719 to enhance dye-sensitized solar cell (DSSC) performance. Both of them could overcome the deficiency of the ruthenium complex N719 absorption in the region of ultraviolet and blue-violet, and the charge collection efficiency is also improved when 1 and 2 are used as co-sensitizers, which are all in favor of enhancing the performance. The DSSC devices using co-sensitizers of 1/N719 and 2/N719 show an overall conversion efficiency of 8.27% and 7.73% with a short circuit current density of 17.48 mA cm(-2) and 17.39 mA cm(-2), and an open circuit voltage of 0.75 V and 0.74 V, respectively. The overall conversion efficiency is 27.23% and 18.92% higher than that of a device solely sensitized by N719 (6.50%). Consequently, the prepared complexes are high efficiency co-sensitizers for enhancing the performance of N719 sensitized solar cells.

We design two novel d10 metal complexes [Zn(3-qlc)2]n (Zn1), [Cd(3-qlc)2]n (Cd1) (3-Hqlc = quinoline-3-carboxylic acid), which display similar 2D layer structures, and further form 3D 6-connected primitive cubic (pcu) network topology via π⋯π stacking interactions with the point symbol {412·63}. Complexes Zn1 and Cd1 exhibit tunable luminescence and photovoltaic properties as a new type of multifunctional materials. Zn1 and Cd1 show tunable luminescence from blue to green by varying the temperature in the solid state. What's more, both of them exhibit excellent aggregation-induced emission (AIE) properties in DMSO/water mixtures. Encouraged by the UV-visible absorption in an ethanol solution result, Zn1 and Cd1 can be considered as co-sensitizers in combination with N719 to investigate their effect on enhancing the dye-sensitized solar cells (DSSCs) performance. Zn1 and Cd1 could overcome the deficiency in the ruthenium complex N719 absorption in the ultraviolet and blue-violet region, offsetting competitive visible light absorption of I3− and reducing the charge recombination of injected electrons. After being co-sensitized with Zn1 and Cd1, the devices co-sensitized by Zn1/N719 and Cd1/N719 yield an overall efficiency of 7.75% and 7.70%, which are 44.59% and 43.66% higher than that of the device sensitized only by N719 (5.36%).

Based on a new design of 4-cyanobenzyl-based 1,2,4-triazole ligand 4-(1,2,4-triazolylmethyl) cyanobenzene (TMCB), a series of cadmium complexes 1–5′ from a mononuclear to three-dimensional (3D) structure have been synthesized through hydro(solvo)thermal reactions; they were generally formulated as [Cd(TMCBA)2]n (1), [Cd(TMCB)(1,4-bda)(H2O)]n (2), {[Cd2(TMCB)4(1,4-bda)2(H2O)2]n·3H2O}n (3), {[Cd(TMCB)4(H2O)2]·(NO3)2·(H2O)2}n (4), [Cd1.5(1,4-bda)1.5(DMF)2]2n (5) and [Cd1.5(1,4-bda)1.5(DMF)2]2n (5′) (TMCBA = 4-(1,2,4-triazolylmethyl) benzoic acid, which is formed from the hydrolysis of TMCB; 1,4-H2bda = 1,4-benzenedicarboxylic acid; the difference between two genuine supramolecular isomers of 5 and 5′ is the use of TMCB as the additive agent for the reaction). Complexes 1–5′ exhibit tunable luminescence with emission maxima containing deep blue, blue, light blue, green and deep green region at 298 K or 77 K in both different solvents (polarity: DMSO > CH3OH > CHCl3) and solid state. Interestingly, the good thermal stability accompanied by their compensated adsorption to ruthenium complex N719 in the region of low wavelength, enabled 1 and 4 to serve as co-sensitizers in combination with N719 in dye sensitized solar cells (DSSCs). After co-sensitization with N719, the overall conversion efficiency of 1 and 4 were found to be 7.68% and 6.85%, which are 40.40% and 25.23% higher than that for DSSCs only sensitized by N719 (5.47%) under the same conditions, respectively. The improvement in efficiency is attributed to the fact that complexes 1 and 4 overcome the deficiency of N719 absorption in the low wavelength region of ultraviolet and blue-violet, offset competitive visible light absorption of I3− and reduce charge recombination due to the formation of an effective cover layer of the dye molecules on the TiO2 surface. As a result, the synthesized complexes are promising candidates as co-adsorbents and co-sensitizers for highly efficient DSSCs.

Through loading of TiO2 on the surface of K6SiW11O39Co(II)(H2O)·xH2O (SiW11Co), a novel photoanode material has been created for dye-sensitized solar cells (DSSC). The absorbing band as well as photoelectricity response range of TiO2@SiW11Co is extended to the visible range. In addition, the absorption in the UV range is enhanced notably compared with P25 (raw TiO2). More importantly, the recombination of the TiO2 network is avoided. TiO2@SiW11Co is mixed with P25 powder (wt ∼1 : 1) to assemble dye-sensitized (N719) solar cells, which exhibit a short-circuit photocurrent density as high as 18.05 mA cm(-2), which is 64% higher than blank samples under the standard AM1.5G global solar irradiation. In addition, the mechanisms for SiW11Co in DSSC are proposed.

Planar heterojunction perovskite solar cells (PHJ-PSCs) constructed with one-step precursor solution spin-coating deposition (OPSSD) usually give an extremely low performance mainly due to the poor morphology and low crystallinity of the perovskite films. In this work, by incorporating a suitable HONH

In this work, a rare 2D → 3D single-crystal-to-single-crystal transformation (SCSC) is observed in metal-organic coordination complexes, which is triggered by thermal treatment. The 2D two-fold interpenetrating square lattice layer [Cd(IBA)2]n (1) is irreversibly converted into a 3D four-fold interpenetrating diamond framework {[Cd(IBA)2(H2O)]·2.5H2O}n (2) (HIBA = 4-(1H-imidazol-1-yl)benzoic acid). Consideration is given to these two complexes with different interpenetrating structures and dimensionality, and their influence on photovoltaic properties are studied. Encouraged by the UV-visible absorption and HOMO-LUMO energy states matched for sensitizing TiO2, the two complexes are employed in combination with N719 in dye-sensitized solar cells (DSSCs) to compensate absorption in the ultraviolet and blue-violet region, offset competitive visible light absorption of I3(-) and reducing charge the recombination of injected electrons. After co-sensitization with 1 and 2, the device co-sensitized by 1/N719 and 2/N719 to yield overall efficiencies of 7.82% and 8.39%, which are 19.94% and 28.68% higher than that of the device sensitized only by N719 (6.52%). Consequently, high dimensional interpenetrating complexes could serve as excellent co-sensitizers and have application in DSSCs.

The performances of stimulated Brillouin scattering (SBS) media with short phonon lifetimes on temporal compression are studied in this paper. In the experiment, FC-72, HT-135 and FC-40 (phonon lifetimes are 1.2 ns, 0.4 ns and 0.2 ns, respectively) are used to study the influence of phonon lifetime on pulse compression in a compact two-cell SBS system. High pulse compression ratio is obtained by a medium with a short phonon lifetime when input energy is high. These results are useful in the generation of picoseconds pulse for Shock Ignition of thermonuclear fuel for ICF.

Three new complexes [Cd(H2pimda)2(H2O)2]·4H2O (1), [Zn(H2pimda)2(H2O)2]·3.5H2O (2) and [Cd2(Hpimda)2(DMF)2]n (3) (H3pimda = 2-propyl-1H-imidazole-4,5-dicarboxy acid, DMF = N,N′-dimethylformamide) have been synthesized under hydrothermal or solvothermal conditions, respectively. Crystal structures of complexes 1–3 were determined by single crystal X-ray diffraction. Crystallographic studies on 1 and 2 reveal that both complexes are six-coordinated, whose geometries can be best described as distorted octahedron. Complex 3 was synthesized based on that of complexes 1 and 2. We change the coordination environment of H3pimda during the synthesis process of complex 3 using organic acid and organic solvent, accordingly, result in different structures ranging from 0D molecule (for 1 and 2) to infinite 2D network (for 3). Complexes 1–3 have blue fluorescent emissions at room temperature in the dimethylsulfoxide (DMSO) solution, which indicate they are potential blue luminescence materials. The blue fluorescent emissions of complexes 1–3 are due to the π∗ → π transitions of intra-ligand.

Two novel complexes [Cd(phen)(NO3)(NO2)(H2O)]n (1) and Cd(phen)2(NO3)(NO2) (2) (phen = 1,10-phenanthroline) have been synthesized by the reductive reaction of metal source Cd(NO3)2·4H2O with phen and benzidine in the mixed solution of DMF, ethanol and water. Crystal structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Complex 1 is a one-dimensional (1D) zig-zag infinite chain in which (phen)Cd(II) units were bridged by two O atoms of NO2−. The three-dimensional (3D) supramolecular structure of 1 is constructed through hydrogen-bond and aromatic π–π stacking interactions between adjacent metal–organic polymeric coordination chains. Complex 2 is a mononuclear structure, and self-assembled through π–π stacking interactions to form a three-dimensional (3D) supramolecular structure. The complex 1 exhibits luminescent property in the near-UV at room temperature in solutions of DMSO and DMF with the emission energy following the order DMF

A method of generating flat-top waveform in the time-domain based on stimulated Brillouin scattering (SBS) using medium with short phonon lifetime is proposed. In theory, the transmitted pulse is simulated in the case of several media with different phonon lifetime. In experiment, FC-72 and HT-270, which differ significantly in the phonon lifetime, are exploited in the experiment. Both the theoretical and experimental results indicate that, when choosing medium with short phonon lifetime, the top is almost a platform, while there is a peak in the front and a platform thereafter when choosing medium with long phonon lifetime.

Two new Ni(II) complexes of 2,6-bis[1-(2,6-diethylphenylimino)ethyl]pyridine (L1), 2,6-bis[1-(4-methylphenylimino)ethyl]pyridine (L2 ) have been synthesized and structurally characterized. Complex Ni(L1)Cl2 · CH3CN (1), exhibits a distorted trigonal bipyramidal geometry, whereas complex Ni(L1)(CH3CN)Cl2 (2), is six-coordinate with a geometry that can best be described as distorted octahedral. The catalytic activities of complexes 1, 2, Ni{2,6-bis[1-(2,6-diisopropyl-phenylimino)ethyl]pyridine} Cl2 · CH3CN (3), and Ni{2,6-bis[1-(2,6-dimethylphenylimino) ethyl]pyridine}Cl2 · CH3CN (4), for ethylene polymerization were studied under activation with MAO.

A supramolecular Cd(II) complex[Cd(bpdc) (phen)2 (H2O)] . 6H20 (1) was synthesized with 2, 4'-biphenyldicarboxylic acid (H2bpdc) and 1, 10-phenanthroline (phen) under hydrothermal conditions and characterized by single-crystal X-ray diffraction elemental analysis, and IR spectrum. Single-crystal X-ray analysis reveals complex 1 crystalizes in the triclinic P 1 space group, the metal center Cd(II) ion is six-coordinated and exhibits a distorted octahedron geometry arrangement. 3D supramolecular structure could be formed taking into account two kinds of hydrogen bonds and π--π interactions. At the same time, we discussed the luminescent properties of complex 1 in the solid-state as well as in the solvents at different temperatures. When excited at 350 nm, in the solid state at 298 K, 1 has purple luminescence with emission band at 390 nm; in the solid state at 77 K, 1 displays two emission bands at 380 and 520 nm. Because the vibration structure is more defined at low temperature, at 298 K, 1 also has purple luminescence in DMSO and CH3OH solutions with emission bands at 380 and 375 nm, which are blue-shifted compared with solid-state maximum emission band. These all can be attribute to the π*--π transition based on the coordinate ligands. The fluorescence decay curves of complex 1 indicate that the processes of decay consist of two components. At 298 K, the lifetime of 1 is longer in DMSO solution (τ1 =1. 73 µs and τ2 =14. 07 µs) than that in CH3OH solution (τ1 =1. 21 µs and τ2 = 12. 44 µs). Moreover, the-lifetime of 1 is longer at 77 K (τ1 =1. 96 µs and τ2= 16. 11 µs) than that at 298 K in the solid state (τ1= 1. 20 µs and τ2 =11. 34 µs). The results might be caused by the increase in radiative rate and decrease in non-radiative rate at low temperature.

Two new Zn(II) complexes of, 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine (L1), 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine (L2) were synthesized. These two complexes have the formulas Zn(L1)Cl2 (1) and Zn(L2)Cl2·CH3CN (2), respectively. Crystal structures of complexes 1 and 2 were determined by single-crystal X-ray diffraction. Crystallographic studies on 1 and 2 reveal both complexes to be five-coordinate with geometries that can be best described as distorted trigonal bipyramidal. Complexes 1 and 2 have blue luminescence at room temperature in solution and the solid state. The blue luminescence of the complexes is due to π* → π transition centered on the ligands. The Zn(II) centers play a key role in enhancing fluorescent emission of the ligands.

Four new CdII complexes of 2,6-bis[1-(phenylimino)ethyl]pyridine (L1), 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine (L2), 2,6-bis[1-(2,6-dimethylphenylimino)ethyl]pyridine (L3), 2,6-bis[1-(2-methylphenylimino)ethyl]pyridine (L4) have been synthesized. These complexes have the formulas [Cd(L1)Cl2]·1.5CH3CN (1), [Cd(L2)Cl2] (2), [Cd(L3)Cl2]·CH3CN (3), and [Cd(L4)Cl2]·CH3CN (4). The molecular structures of complexes 1−4 were determined by single-crystal X-ray diffraction. Crystallographic studies of 1−4 reveal all four complexes to be five-coordinate with geometries that can be best described as distorted trigonal-bipyramidal. All eight compounds (L1−L4 and 1−4) are luminescent at room temperature in solution and the solid state. At 298 K in dichloromethane solution, all compounds have fluorescent emissions at about 368−409 nm. The fluorescent emission of these compounds originates from ligand-centered π*−π transitions. The CdII centers play a key role in enhancing the fluorescent emission of the ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The 3D netlike coordination polymer of Zn II with benzimidazole-5,6-dicarboxylic acid (H3BIDC), [Zn(HBIDC) x H2O]n was synthesized by the hydrothermal method through self-assembling. The crystal structure of complex 1 was characterized by single-crystal X-ray diffraction, elemental analysis and IR spectra, and we also studied the fluorescence properties of complex 1 in DMSO and in the solid state with UV-Vis absorption spectra, fluorescence spectra and fluorescence lifetime. Complex 1 has blue luminescence in solutions of DMSO with emission band at 481 nm; and has blue luminescence in the solid state at room temperature with a strong emission band at 493 nm, and these all can be attributed to the pi* --pi transition based on the benzimidazole-5,6-dicarboxy acid. The experimental results indicate that complex 1 displays higher fluorescence quantum efficiency and can be used as a potential blue luminescence material.

Binuclear complex [Cu2 (mu-I)2 (phen)2] x CH3CN(1)(phen = 1,10-phenanthroline) was synthesized under solvothermal conditions and characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. X-ray diffraction analysis reveals that complex 1 is monoclinic, space group P2(1/n), and the cell parameters are: alpha = 10.505 A, b = 23.628 A, c = 10. 676 A, alpha = 90, beta = 91.40 degrees and gamma = 90 degrees. The authors have studied the luminescence property of 1, Complex 1 has blue-purple luminescence in solutions of DMSO with emission bands at 369, 380 and 460sh nm; and has red luminescence in the solid state at room temperature with a broad emission band at 650-678 nm. These all can be attributed to the pi* --pi transition based on the ligand. In the solid state, the emission frequencies for complex 1 are red-shifted about 280 nm compared with their emission maximum peaks in solutions of DMSO. This red-shift of emission energy from solution to solid is likely to be caused by the intermolecular pi--pi packing interaction in the solid state which effectively decreases the energy gap. The fluorescence decay curve of complex 1 indicated that the processes of decay consists of two components, whose corresponding lifetimes are tau1 = 1.36 micros and tau2 = 5.98 micros, corresponding factors are 50.21% and 49.79% in DMSO solutions, and tau1 = 1.42 micros, tau2 = 8.85 micros, corresponding factors are 51.15% and 48.85% in the solid state.

A supermolecular compound [Zn(H2O)6].(C16H8O8) was synthesized with 3,3', 4,4'-bipthenyltetracarboxylic acid (H4BPTC) and Zn(CH3COO)2.2H2O. Its structure was determined by single crystal X-ray diffraction, IR and element analysis. The crystal belongs to triclinic system with space group and the cell parameters are: a = 0.65484 (13) nm, b = 0.79388 (16) nm, c = 0.96812 (19) nm, alpha = 76.29 (3) degrees, beta = 87.75 (3) degrees, gamma = 86.43 (3) degrees, Z=1, R1 = 0.0665, wR2 = 0.1833, and GOF = 1.021. We have studied the luminescence property of compound 1, The compound 1 has blue-purple luminescence in solutions of DMSO and green luminescence in the solid state at room temperature. In the solid state, the emission frequencies for complex 1 are red-shifted compared with their emission maximum peaks in solutions of DMSO. This red-shift of emission energy from solution to solid is likely to be caused by the intermolecular interaction in the solid state that effectively decreases the energy gap.

2-D layered Dy coordination polymer [Dy(PDA) (HPDA)I]n (1)(H2PDA = pyridine-2,6-dicarboxylic acid) with (4.8(2)) topological network was synthesized under hydrothermal conditions and was characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. X-ray diffraction analysis reveals that compound 1 is monoclinic, space group P2(1)/c. In the structure of compound 1, metal-centered Dy is connected via O atoms of H2PDA ligands to form a (4.82) topology network. The 3-D supramolecular structure of 1 is constructed through pi--pi stacking interactions between the adjacent layers. The luminescence properties of 1 were determined by UV-Vis and fluorescence spectrum in solid state at room temperature. The H2PDA and 1 exhibit the similar broad maximum absorption peak at 280 nm, which are attributed to ligand-centered pi--pi* transition. The fluorescence emission band based on ligand-center and characteristic emission of Dy3+ at the same maximum excitation wavelength of 280 nm were observed in 1. The fluorescence decay curve of complex 1 indicated that the processes of decay consists of two components, of which corresponding lifetimes tau1 = 3.61 micros and tau2 = 12.81 micros.

In the title centrosymmetric dinuclear complex, [Eu(2)(CH(3)CO(2))(6)(C(12)H(8)N(2))(2)], the Eu(III) atom is nine-coordinated by two N atoms from a 1,10-phenanthroline ligand and seven O atoms from five acetate ligands (two bidentate, three monodentate). The crystal structure is stabilized by π-π stacking inter-actions between the pyridine and benzene rings of adjacent mol-ecules, with a centroid-centroid distance of 3.829 (2) Å.

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.

Three series of two-dimensional and three-dimensional lanthanide coordination polymers {[Ln(ox)1.5(H2O)3]·mH2O}n [Ln = Ce (1), m = 2 and Pr (2), m = 3, H2ox = oxalic acid], {[Ln(ox)2(H3O)]·EtOH·3H2O}n [Ln = Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10) and Yb (11), EtOH = ethanol] and {[Ln2(IMDC)2(H2O)3]·mH2O}n [Ln = Sm (12), Eu (13), Gd (14), Tb (15) and Dy (16), where m = 2.25 except for 15 where m = 1.75, H3IMDC = imidazole-4,5-dicarboxylic acid] have been synthesized under hydrothermal conditions. All the coordination polymers have been characterized by elemental analysis, IR spectroscopy and X-ray single-crystal diffraction. Coordination polymers 1–11 exhibit two different structural types: the 2-D structure of coordination polymers 1–2 are a (6,3)-connected hcb network, coordination polymers 3–11 appear as a 3-D diamond structure with 66-network topology. Coordination polymers 12–16 are 3-D structures constructed from the bridged carboxyl group of IMDC3−, in which IMDC3− bridged the DNA-like double-helix line and the triple-helix line, intertwined and connected into a 1-D chain and then conformed into a 3-D structure along the ab plane. The different structures of the two dicarboxylate ligands (oxalic acid as a flexible ligand and imidazole-4,5-dicarboxylic acid as a rigid planar ligand) were described and discussed. Furthermore, the luminescent properties in the visible region and the fluorescence lifetimes of the coordination polymers exhibited the characteristic transitions of the corresponding lanthanide ions. It was noted that coordination polymers 5 and 7 have long solid-state fluorescence lifetimes of 824.84 and 733.87 μs, respectively. The NIR emission spectra of the Nd (3), Sm (4 and 12), Dy (8 and 16) and Yb (3) coordination polymers in the solid-state were measured. The singlet excited state (30 842 cm−1 for oxalic acid, 32 258 cm−1 for H3IMDC) and the lowest triplet state energy level (23 753 cm−1 for oxalic acid and 22 371 cm−1 for H3IMDC) of the H2ox and H3IMDC ligand were calculated on the basis of the UV-Vis absorbance edges of the ligand and the phosphorescence spectrum of the Gd(III) coordination polymers 6 and 14 at 77 K, respectively. The relationship between the lowest triplet state energy level of the two dicarboxylate ligands and lowest resonance energy levels of the Sm(III), Eu(III), Tb(III) and Dy(III) ions were described and discussed. The results showed that the energy transfer from the oxalic acid ligands is much more effective than H3IMDC.

One-dimensional to three-dimensional lanthanide coordination polymers 1–8 based on benzimidazole-5,6-dicarboxylic acid (H3BIDC) have been synthesized under hydrothermal conditions at different pH values, generally formulated as {[Pr(HBIDC)(ox)0.5(H2O)]·H2O}n (1), [Yb(HBIDC)(ox)0.5(H2O)2]n (2), and [Ln(HBIDC)(ox)0.5(H2O)3]n [Ln = Ho (3), and Tb (4)] and {[Ln(H2BIDC)(HBIDC)(H2O)3]·3H2O}n [Ln = Tb (5), Sm (6), Dy (7), and Gd (8), H2ox = oxalic acid]. All coordination polymers have been characterized by elemental analysis, infrared spectra and single-crystal X-ray diffraction. The structural diversity, luminescence and thermal properties of all coordination polymers have been investigated. Coordination polymers 1–8 exhibit four different structural types: topological analysis has given the 3-D pcu network, with the point symbol of {412·63} in coordination polymer 1. Coordination polymer 2 exhibits a 4-connected 44 topology, and coordination polymers 3–4 appear as 2-D (6,3)-connected hcb network topology. The 1-D helical infinite chain of coordination polymers 5–8 around the crystallographic 21 axis spread along the b axis direction, with different 1-D helical infinite chains forming 3-D supramolecular framework via hydrogen bonds and π–π stacking interactions. The coordination polymers 4 and 5 could be triggered to have intense characteristic lanthanide-centered green luminescence under UV excitation in the solid state at room and liquid nitrogen temperature, or dispersed in CH2Cl2 at 77 K. In coordination polymers 4 and 5, the oxalic acid introduced into coordination polymer 4 as a second ligand further sensitized the trivalent terbium ion, and resulted in longer fluorescence lifetimes of coordination polymer 4 (1058.58 μs at 298 K, 679.42 μs at 77 K in the solid-state, 867.82 μs in CH2Cl2 at 77 K) than coordination polymer 5 (595.06 μs at 298 K, 583.19 μs at 77 K in the solid-state, 584.38 μs in CH2Cl2 at 77 K). In coordination polymers 6 and 7, we not only measured emission spectra in the visible region, but also detected the infrequent NIR emission spectra in the near infrared region of samarium and dysprosium ions. The singlet excited state (30 303 cm−1) and the lowest triplet state energy level (24 390 cm−1) of H3BIDC ligand were calculated based on the UV-vis absorbance edges of ligand and the phosphorescence spectrum of Gd(III) coordination polymer (8) at 77 K, showing that the effective extent of energy transfer from H3BIDC ligand to lanthanide ions follows the sequence of Tb3+, Dy3+ > Sm3+. Finally, thermal behaviors of all coordination polymers were studied by thermogravimetric analysis, which exhibited high thermal stability.

Two lanthanide complexes, Ln(HPDA)(3)·4EtOH (Ln = Tb, Dy) (H(2)PDA = pyridine-2,6-dicarboxylic acid, EtOH = ethanol), have been successfully synthesized using hydrothermal or solvothermal methods, and their crystal structures were analyzed by single crystal XRD. Both crystals have orthorhombic symmetry with space group Pbcn, exhibiting three-dimensional (3D) supramolecular architecture through hydrogen bonding interactions. The metal center was coordinated to nine atoms by three pyridine-2,6-dicarboxylic acid ligands. The nine-coordinated lanthanide metal complexes were assembled onto a nanocrystalline TiO(2) film to form co-sensitized photoelectrodes with N719 for dye-sensitized solar cells, and their photoelectrochemical performance was studied. In the tandem structure of composite electrodes, the energy levels of lanthanide metal complexes are reorganized in their single-crystal form, as verified by ab initio calculations. The co-sensitized systems are far superior for electron-injection and hole-recovery compared with single N719-sensitized systems. Luminescence properties were measured and electrochemical analysis was also performed on these complexes.