A New 3D Iodoargentate Hybrid: Structure, Optical/Photoelectric Performance and Theoretical Research

The explorations of new three-dimensional (3D) microporous metal halides, especially the iodoargentate-based hybrids, and understanding of their structure-activity relationships are still quite essential but full of great challenges. Herein, with the aromatic 4,4'-dpa (4,4'-dpa = 4,4'-dipyridylamine) ligands as the structural directing agents, we solvothermal synthesized and structurally characterized a novel member of microporous iodoargentate family, namely [H2-4,4'-dpa]Ag6I8 (1). Compound 1 possesses a unique and complicated 3D [Ag6I8]n2n- anionic architecture that was built up from the unusual hexameric [Ag6I13] secondary building units (SBUs). Research on optical properties indicated that compound 1 exhibited semiconductor behavior, with an optical band gap of 2.50 eV. Under the alternate irradiation of light, prominent photoelectric switching abilities could be achieved by compound [H2-4,4'-dpa]Ag6I8, whose photocurrent densities (0.37 μA·cm-2 for visible light and 1.23 μA·cm-2 for full-spectrum) compared well with or exceeded those of some high-performance halide counterparts. Further theoretical calculations revealed that the relatively dispersed conduction bands (CBs) structures in compound 1 induced higher electron mobilities, which may be responsible for its good photoelectricity. Presented in this work also comprised the analyses of Hirshfeld surface, powder X-ray diffractometer (PXRD), thermogravimetric measurement, energy-dispersive X-ray spectrum (EDX) along with X-ray photoelectron spectroscopy (XPS).

2-D Heterometallic Pb-Iodoargentate Framework [PbAg2I6]n with a Diskoid [Pb(18-crown-6)]2+ Linker and Cocatalyst for Synergistically Enhanced Photocatalytic Properties via g-C3N4 Doping

The heterometallic Pb-iodoargentate hybrid [Pb(18-crown-6)(PbAg₂I₆)]_n (1; 18-crown-6 = 1,4,7,10,13,16-hexaoxacyclooctadecane) was prepared via self-assembly of the tetrahedal AgI₄ and octahedral PbI₆ primary units using crown ether 18-crown-6 as an organic ligand in DMF solvent. The hybrid heterocomposite cocatalyst based on 1 and graphitic carbon nitride (g-C₃N₄) was prepared by a facile solvothermal method. In 1, the dimeric units Ag₂I₆ and Pb₂I₁₀ are joined via face sharing, leading to a ternary heterometallic 1-D [PbAg₂I₆^2-]_n chain containing novel Ag₂Pb₂I₄ cubes. The 1-D chains are joined by the discoid [Pb(18-crown-6)]²⁺ complex cations, forming the 2-D [Pb(18-crown-6)(PbAg₂I₆)]_n hybrid with the skeleton of [Pb₂Ag₂I₆]_n. Compound 1 shows photocatalytic activity in the degradation of MB at room temperature under visible-light irradiation. The photoelectric response measurement showed that the photocurrent of 1 increased from 1.41 to 2.43 μA/cm^-2 when g-C₃N₄ was loaded, indicating that the introduction of a certain amount of g-C₃N₄ on the surface of 1 improves the separation and migration rate of photoinduced electrons and holes. The 1/g-C₃N₄ composite showed much higher photocatalytic efficiency in comparison to pristine 1 and g-C₃N₄ for MB degradation, which suggests the synergistic effect between 1 and g-C₃N₄ toward visible-light-driven photocatalytic performance. Meanwhile, the 1/g-C₃N₄ composite exhibited good reusability and stability in the photocatalytic reaction. Free radical quenching experiments showed that the ^•O₂^- radical is the main reactive substance over catalyst 1, while h⁺, ^•OH, and ^•O₂^- species have synergistic effects over the 1/g-C₃N₄ composite catalyst in the process of photodegradation.

Transition-Metal-Complex-Directed Synthesis of Hybrid Iodoargentates with Single-Crystal to Single-Crystal Structural Transformation and Photocatalytic Properties

We synthesized and characterized three types of isostructural iodoargentates, [TM(phen)₃]Ag₂I₄·3DMF (TM = Co (1), Ni (2), Zn (3)), [TM(phen)₃]Ag₃I₅·DMF (TM = Co (4), Ni (5), Zn (6)), and [TM(phen)₃]₂Ag₈I₁₂·7DMF (TM = Co (7), Ni (8), Zn (9)) (phen = 1,10-phenanthroline, DMF = dimethylformamide) using transition-metal (TM) complexes as the structure-directing agents. Compounds 1-3 and compounds 4-6 feature zero-dimensional anionic [Ag₄I₈]^4- and [Ag₆I₁₀]^4- clusters, respectively. All of the [TM(phen)₃]²⁺ cations in compounds 1-6 are arranged into a two-dimensional (2D) (6,3) net layer. Interestingly, compounds 1-3 are kinetically unstable in the mother solution, and they can be converted to compounds 4-6 via irreversible single-crystal to single-crystal transformation processes, respectively, with distinct changes in the crystal morphology and structure. Compounds 7-9 feature one-dimensional (1D) zigzag chains constructed from [Ag₈I₁₂]^4- units. The UV-vis diffuse reflectance measurements demonstrate that compounds 1-9 possess the characteristics of semiconductors with band gaps of 2.58-2.71 eV and visible-light-irradiation-induced photocatalytic activities. Especially, compound 3 possesses higher photocatalytic degradation activity toward crystal violet (CV) and rhodamine B (RhB) in comparison to P25 under identical conditions. Moreover, the mechanism study reveals that the TM complex cations make a great contribution to the photocatalytic activity.

Luminescent Thermochromic Silver Iodides as Wavelength-Dependent Thermometers

Luminescent thermochromic materials with a dramatic shift of emission band under different temperatures are highly desirable in temperature sensing fields. However, the design of the synthesis of such compounds remains a great challenge. In this work, two new luminescent thermochromic silver iodides, (emIm)Ag₃I₄ (1) and (emIm)Ag₂I₃ (2) (emIm = 1-ethyl-3-methyl imidazole), have been synthesized under solvothermal conditions. Compound 1 features a [Ag₃I₄]^- anionic layer, while compound 2 possesses an infinite [Ag₂I₃]^- chain structure, both of which are charge balanced by emIm⁺ cations. Particularly, they display luminescent thermochromism with a significant wavelength shift of emission maximum with temperature change. They represent rare examples of infinite layered or chain silver iodides that show luminescent thermochromism. Furthermore, the results indicate that compounds 1 and 2 are promising wavelength-dependent luminescent thermometers.

Semiconducting crystalline inorganic-organic hybrid metal halide nanochains

One-dimensional (1D) inorganic-organic metal halide hybrids at the molecular level, which can be considered as arrays of nanochains isolated by organic components, have shown remarkable optical and electric properties. This review summarizes their reported structural types and shows how to modify their band gaps and optical and electric properties.

The engineering of stilbazolium/iodocuprate hybrids with optical/electrical performances by modulating inter-molecular charge transfer among H-aggregated chromophores

Good electrical bistability performances in stilbazolium/iodocuprate hybrids stem from the better face-to-face π⋯π stacking interactions induced by the substituents with appropriate lengths and electronic natures.

Bisimidazole-based phosphorescent thiocyanatocadmates

Simple room-temperature self-assemblies between Cd2+ salts, SCN- and bisimidazole molecules at pH = 2 created three new organically templated thiocyanatocadmates [H2(L1)][Cd(SCN)4]·H2O (L1 = 1,4-bis(1H-imidazol-1-yl)benzene) 1, [H2(L2)][Cd(SCN)4] (L2 = 1,3-bis(2-methylimidazol-1-yl)propane) 2, and [H2(L3)][Cd2(SCN)6] (L3 = 1,4-bis(2-methyl-1H-imidazol-1-yl)butane) 3. X-ray single-crystal diffraction analysis reveals that (i) in 1-3, the SCN- groups doubly bridge the Cd2+ centers to form different thiocyanatocadmates: a linear chain in 1; a zigzag chain in 2; and a 2-D layer network (63 net) in 3; and (ii) in 1, via Nbase-HNSCN interactions, the L1 molecules extend the thiocyanatocadmate chains into a 2-D supramolecular layer, whereas in 2, the zigzag thiocyanatocadmate chains self-assemble into a 3-D supramolecular network via weak SS interactions. Photoluminescence analysis indicates that the three title compounds all emit light: blue light for 1 and 2 and green light for 3. At low temperatures, the emission positions of the three compounds hardly change, but the emission intensities are largely enhanced. Interestingly, after turning off the UV lamp, 1 and 2 still briefly emit light (ca. 2 s), which means that 1 and 2 possess phosphorescence properties. Phosphorescence lifetimes at 77 K are 1619 ms for 1 and 247 ms for 2.

Copper(i)-polymers and their photoluminescence thermochromism properties

Under hydro(solvo)thermal conditions, four organic bidentate bridging N,N'-donor ligands 1,3-bis(2-methylimidazol-1-yl)propane (L1), 4,4'-di(1H-imidazol-1-yl)-1,1'-biphenyl (L2), 1,2-bis(2-methyl-1H-imidazol-1-ylmethyl)benzene (L3) and 5,6,7,8-tetrahydroquinoxaline (L4) were employed to react with CuBr/CuI, generating four 2-D layered copper(i)-polymer coordination polymer materials [Cu2Br2(L1)] 1, [CuI(L2)] 2, [CuI(L3)] 3 and [CuI(L4)0.5] 4. In 1-4, different Cu-X motifs are found: a cubic Cu4Br4 core in 1; a castellated Cu-I single chain in 2; a rhombic Cu2I2 core in 3; and a staircase-like Cu-I double chain in 4. The 2-D layer networks of 1-3 can all be simplified into a simple 44 topology (planar for 1 and 3; wave-like for 2), while the 2-D layer network of 4 has a 63 topology. The photoluminescence behaviors of 1-4 under a UV lamp suggest that 1 and 2 possess fluorescence thermochromism properties. Under the UV lamp, with the decrease in temperature, (i) 1 exhibits a yellow-to-red emission; (ii) 2 exhibits a yellow-to-green emission; (iii) 3 always emits green light; and (iv) 4 never emits light. These are further confirmed by their emission spectra. From 297 K to 77 K, the emission of 1 exhibits a large red shift from 561 nm to 623 nm; the emission of 2 exhibits a large blue shift from 571 nm to 515 nm; only a minor red shift is observed for the emission of 3; and no peaks appear in the emission spectra of 4. The crystal data of 1 and 2 at different temperatures have been collected for revealing the origination of their fluorescence thermochromism properties. Based on the above investigations, the effect of the rigidity/flexibility of the organic ligand on the fluorescence thermochromism properties of copper(i)-polymer coordination polymer materials is discussed. The quantum yields at 297 K and the photoluminescence lifetimes at 297 K and 77 K for 1-3 were also measured for better understanding their photoluminescence properties.

A unique formyl iodoargentate exhibiting luminescent and photocurrent response properties

A unique formyl iodoargentate contains an unprecedented CHO⁻ link mode, which exhibits luminescent and photocurrent response properties.

Two photochromic iodoargentate hybrids with adjustable photoresponsive mechanism

Two photochromic hybrid iodoargentates with adjustable photoresponsive mechanism have been synthesized and exhibit fast response and wide color range.

New photoluminescent iodoargentates with bisimidazole derivatives as countercations

In this article, three bisimidazole derivatives (1,4-bis(2-ethylimidazol-1-yl)butane, L1; 4,4′-di(1H-imidazol-1-yl)-1,1′-biphenyl, L2′; and 1,3-bis(2-ethylimidazol-1-yl)propane, L3) were employed to solvothermally react with AgI in an acidic environment, creating three new 1-D chained iodoargentates [H(L1)][Ag₅I₆]·DMF (DMF = N,N′-dimethylformamide) 1, [L2][Ag₃I₅] (L2²⁺ = 4,4′-di(1H-imidazol-1-ium)-1,1′-biphenyl) 2, and [H₂(L3)][Ag₂I₄] 3. L2²⁺ in 2 originated from the in situ N-alkylation of L2′ with the CH₃OH solvent. X-ray single-crystal diffraction analysis reveals that (i) in 1, Ag⁺ and I⁻ aggregate to form a 1-D tube-like iodoargentate, which exhibits the same topology as the carbon tube; (ii) the chain structure of the iodoargentate in 2 is based on a kind of trinuclear Ag–I cluster, which can be viewed as a segment of the classical cubic M₄I₄ cluster; (iii) the chain structure of the iodoargentate in 3 is simple, which can be described as a linear arrangement of the AgI₄ tetrahedra by sharing edges. The photoluminescence analysis reveals that at 77 K, (i) 1 and 2 emit strong yellow light with ms-grade photoluminescence lifetimes (5.460 ms for 1, 6.931 ms for 2); (ii) 3 possesses photochromic luminescence properties. Upon excitation at 254 nm, it emits blue-green light, whereas upon excitation at 365 nm, it emits yellow light.

Three bisimidazole-based chained iodoargentates were solvothermally synthesized, and their photoluminescent behaviors at different temperatures were investigated. Of those, 3 has been found to possess photochromic luminescence properties.

Iodoargentates from clusters to 1D chains and 2D layers induced by solvated lanthanide complex cations: syntheses, crystal structures, and photoluminescence properties

Lanthanide(iii) iodoargentates [Ln(DMSO)₈]₄Ag₂₂I₃₄·2H₂O (Ln = La (1), Ce (2)), [Ln(DMSO)₈]Ag₇I₁₀(Ln = Eu (3), Tb (4), Dy (5)), and [Yb(DMSO)₇]Ag₅I₈(6) were synthesized by a diffusion method.

Reversible solid-state thermochromism of a 2D organic–inorganic hybrid perovskite structure based on iodoplumbate and 2-aminomethyl-pyridine

An organic–inorganic hybrid solid [(PyCH₂NH₃)₆][Pb₅I₂₂]·3H₂O with a 2D inorganic layer exhibited a reversible color change from orange to red at 80 °C in the solid state.

Relaxor-like and switchable dielectric behavior in a rare noncentrosymmetric 3D iodoargentate hybrid

A rare noncentrosymmetric three-dimensional (3D) iodoargentate hybrid, namely, [Cd(en)₃]Ag₂I₄ (1), was prepared using a simple solution process.

Syntheses, crystal structures and photocatalytic properties of four hybrid iodoargentates with zero- and two-dimensional structures

Four new hybrid iodoargentates have been solvothermally prepared and structurally characterized. The title compounds possess semiconductor characterizations and efficient photocatalytic activities under visible light irradiation.

Stoichiometry-controlled structural and functional variation in two photochromic iodoargentates with a fast and wide range response

Two MCMP⁺/iodoargentate hybrids have been synthesized and they exhibit rare electron transfer photochromsim with a fast response rate, a wide response range and a long-lived charge-separated state, which is largely ascribed to the flexible aggregation of electron-deficient MCMP⁺ counterions.

Symmetrically Related Construction and Optical Properties of Two Noncentrosymmetric 3D Iodides of d(10) Cation (Cu(+), Ag(+)) Based on the N-Benzylpyridinium and Its Supramolecular Interactions

Two noncentrosymmetric compounds, namely, [N-Bz-Py]2[Cu6I8] (1) and [N-Bz-Py]4[Ag9I13] (2) (N-Bz-Py(+) = N-benzylpyridinium), with three-dimensional open frameworks, were synthesized solvothermally via in situ benzylation of pyridine. 1 is constructed from 3-connected Cu3I7 secondary building units (SBUs) with chiral (10,3)-a topology, while the occluded N-Bz-Py(+) forms a complementary supramolecular (10,3)-a net via π-π interactions. 2 is characteristic of acentric connections of trimeric Ag3I8 and hexamer Ag6I12 SBU, while N-Bz-Py(+) in the channels aggregates into asymmetrically supramolecular chains via π-π interactions. Remarkable structural correlations imply the unique amplification and transfer of asymmetric information from V-shaped N-Bz-Py(+) to organic supramolecular nets and inorganic frameworks, which are confirmed by their second harmonic generation responses. Adsorption spectra reveal their semiconductive nature (2.52 eV for 1 and 3.02 eV for 2) and interesting reversible thermochromism for 1 based on the intermolecular charge transfer.