Photoinduced Significant Magnetization Enhancement in a Viologen-Based Photochromic Compound

Large enhancement of magnetization at room temperature (RT) is highly desirable for real application of photomagnets, but only one known example shows remarkable enhancement of magnetization at room temperature (>30%). This work has successfully obtained a viologen-based complex which exhibited room temperature photochromism and photomagnetism and realized remarkable enhancement of magnetization at room temperature by photoinduced electron transfer. The present viologen-based complex exhibits the second largest magnetization increasing amplitude of 31.1% at room temperature among electron transfer photochromic systems

A New Strategy of Designing New Crystal Structures Based on Topological Structure: Syntheses and Crystal Structures of Five Coordination Polymers with (4,4) Topology

Five coordination polymers <b>1</b>–<b>5</b> with four types of (4,4) layers have been synthesized through a new strategy of designing their crystal structures based on (4,4) topology. Compound [Co­(adc)­(bpp)­(H₂O)]_<i>n</i> (<b>1</b>) presents a 2-D structure with 2-fold homointerpenetration of layer <b>A</b>, while the 2-D compound {[Ni­(adc)­(bpp)₂­(H₂O)]₂·bpp}_<i>n</i> (<b>2</b>) presents 2-fold heterointerpenetration of layer <b>B</b> and layer <b>C</b>. Compound [Zn­(adc)­(bpp)·DMF]_<i>n</i> (<b>3</b>) displays a typical 2-D → 3-D parallel interpenetrating structure of layer <b>D</b>. Compounds [Ni­(Cladc)­(bpp)­(H₂O)]_<i>n</i> (<b>4</b>) and [Co­(Cladc)­(bpp)­(H₂O)]_<i>n</i> (<b>5</b>) are isomorphous and display similar structures to <b>1</b>. (H₂adc = 4,4′-azodibenzoic acid, ClH₂adc = 3,3′-dichloro-4,4′-azodibenzoic acid, bpp = 1,3-di­(4-pyridyl)­propane, DMF = <i>N</i>,<i>N</i>-dimethyl­formamide). Luminescence properties and thermal stabilities of <b>1</b>–<b>5</b> have been explored

Two New Coordination Compounds with a Photoactive Pyridinium-Based Inner Salt: Influence of Coordination on Photochromism

The past years have evidenced the rapid development of photochromic coordination compounds; however, the impact of coordination on the photochromic behavior of organic dyes has never been explored in the pyridinium derivative photochromic system. In this work, two new coordination compounds with a photoactive pyridinium-based inner salt, [Zn­(H₂O)₆]­(PTA)·​(CEbpy)₂·​2H₂O (<b>1</b>, PTA = terephthalate, CEbpy = 1-carboxy­ethyl-4,4′-bipyridine) and [Zn­(H₂O)₂­(CEbpy)₂]_<i>n</i>­Br_2<i>n</i>·​[Zn­(H₂O)₄­(PTA)]_<i>n</i> (<b>2</b>), were selected as model compounds for this purpose. Compound <b>1</b> features an isolated structure, where uncoordinated photoactive CEbpy ligands connect to hexahydrated zinc ions through hydrogen bonds. Compound <b>2</b> features a 1-D chain structure with CEbpy ligands coordinating to zinc ions. Compound <b>1</b> shows faster coloration speed upon irradiation than <b>2</b>, demonstrating that coordination of the electron donor in CEbpy is not in favor of photochromic behavior. Both compounds show significant photoluminescence quenching after coloration, and the intensity contrast before and after coloration for <b>1</b> is larger than that for <b>2</b>. This finding will help to design and synthesize new photochromic compounds with high performance

A New Strategy of Designing New Crystal Structures Based on Topological Structure: Syntheses and Crystal Structures of Five Coordination Polymers with (4,4) Topology

Five coordination polymers <b>1</b>–<b>5</b> with four types of (4,4) layers have been synthesized through a new strategy of designing their crystal structures based on (4,4) topology. Compound [Co­(adc)­(bpp)­(H₂O)]_<i>n</i> (<b>1</b>) presents a 2-D structure with 2-fold homointerpenetration of layer <b>A</b>, while the 2-D compound {[Ni­(adc)­(bpp)₂­(H₂O)]₂·bpp}_<i>n</i> (<b>2</b>) presents 2-fold heterointerpenetration of layer <b>B</b> and layer <b>C</b>. Compound [Zn­(adc)­(bpp)·DMF]_<i>n</i> (<b>3</b>) displays a typical 2-D → 3-D parallel interpenetrating structure of layer <b>D</b>. Compounds [Ni­(Cladc)­(bpp)­(H₂O)]_<i>n</i> (<b>4</b>) and [Co­(Cladc)­(bpp)­(H₂O)]_<i>n</i> (<b>5</b>) are isomorphous and display similar structures to <b>1</b>. (H₂adc = 4,4′-azodibenzoic acid, ClH₂adc = 3,3′-dichloro-4,4′-azodibenzoic acid, bpp = 1,3-di­(4-pyridyl)­propane, DMF = <i>N</i>,<i>N</i>-dimethyl­formamide). Luminescence properties and thermal stabilities of <b>1</b>–<b>5</b> have been explored

Large Mid-IR Second-Order Nonlinear-Optical Effects Designed by the Supramolecular Assembly of Different Bond Types without IR Absorption

Two new different-bond-type hybrid compounds, (Hg₆P₄Cl₃)­(PbCl₃) (<b>1</b>) and (Hg₂₃P₁₂)­(ZnCl₄)₆ (<b>2</b>), with supramolecular interactions between host and guest moieties, which based on metal–pnicogen, pnicogen–pnicogen, and metal–halogen bonds were obtained by solid-state reactions. Compounds <b>1</b> and <b>2</b> show large second-harmonic-generation (SHG) activity and are transparent in the wide mid-IR region, providing an effective route for searching new IR nonlinear-optical material systems by combining two or more different bond types with no IR absorption within a single compound through supramolecular assembly. Theory predications based on first-principles calculations are also performed on the SHG properties of <b>1</b> and <b>2</b>

A Highly Stable 3D Acentric Zinc Metal–Organic Framework Based on Two Symmetrical Flexible Ligands: High Second-Harmonic-Generation Efficiency and Tunable Photoluminescence

A 3D metal–organic framework (MOF), [Zn­(BPHY)­(SA)]_<i>n</i> (<b>1</b>; BPHY = 1,2-bis­(4-pyridyl)­hydrazine, H₂SA = succinic acid), which crystallizes in a noncentrosysmmetric space group (<i>Cc</i>), has been solvothermally obtained and testified to be a good nonlinear-optical material with the largest second-harmonic-generation response among the known MOFs based on sysmmetric ligands and high stability. Ultraviolet-to-visible tunable emission for <b>1</b> is observed

Large Mid-IR Second-Order Nonlinear-Optical Effects Designed by the Supramolecular Assembly of Different Bond Types without IR Absorption

Two new different-bond-type hybrid compounds, (Hg₆P₄Cl₃)­(PbCl₃) (<b>1</b>) and (Hg₂₃P₁₂)­(ZnCl₄)₆ (<b>2</b>), with supramolecular interactions between host and guest moieties, which based on metal–pnicogen, pnicogen–pnicogen, and metal–halogen bonds were obtained by solid-state reactions. Compounds <b>1</b> and <b>2</b> show large second-harmonic-generation (SHG) activity and are transparent in the wide mid-IR region, providing an effective route for searching new IR nonlinear-optical material systems by combining two or more different bond types with no IR absorption within a single compound through supramolecular assembly. Theory predications based on first-principles calculations are also performed on the SHG properties of <b>1</b> and <b>2</b>

Structural Diversity, Optical and Magnetic Properties of a Series of Manganese Thioarsenates with 1,10-Phenanthroline or 2,2′-Bipyridine Ligands: Using Monodentate Methylamine as an Alkalinity Regulator

The exploration in two hydro­(solvo)­thermal reaction systems As/S/Mn²⁺/phen/methylamine aqueous solution and As/S/Mn²⁺/2,2′-bipy/H₂O affords five new manganese thioarsenates with diverse structures, namely, (CH₃NH₃)­{[Mn­(phen)₂]­(As^VS₄)}·phen (<b>1</b> and <b>1′</b>), (CH₃NH₃)₂{[Mn­(phen)]₂(As^VS₄)₂} (<b>2</b>), {[Mn­(phen)₂]­(As^III₂S₄)}_<i>n</i> (<b>3</b>), {[Mn­(phen)]₃(As^IIIS₃)₂}·H₂O (<b>4</b>), and {[Mn­(2,2′-bipy)₂]₂(As^VS₄)}­[As^IIIS­(S₅)] (<b>5</b>). Compound <b>1</b> comprises a {[Mn­(phen)₂]­(As^VS₄)}⁻ complex anion, a monoprotonated methylamine cation and a phen molecule. Compound <b>2</b> contains a butterfly like {[Mn­(phen)]₂(As^VS₄)₂}^2– anion charge compensated by two monoprotonated methylamine cations. Compound <b>3</b> is a neutral chain formed by a helical ¹_∞(As^IIIS₂^–) <i>vierer</i> chain covalently bonds to [Mn^II(phen)]²⁺ complexes via all its terminal S atoms. Compound <b>4</b> features a neutral chain showing the stabilization of noncondensed (As^IIIS₃)^3– anions in the coordination of [Mn^II(phen)]²⁺ complex cations. Compound <b>5</b> features a mixed-valent As^III/As^V character and an interesting chalcogenidometalates structure, where a polycation formed by the connection of two [Mn­(2,2′-bipy)₂]²⁺ complex cation and a (As^VS₄)^3– anion acts as a countercation for a polythioarsenate anion, [As^IIIS­(S₅)]⁻. The title compounds exhibit optical gaps in the range 1.58–2.48 eV and blue photoluminescence. Interestingly, compound <b>1</b> displays a weak second harmonic generation (SHG) response being about 1/21 times of KTP (KTiOPO₄). Magnetic measurements show paramagnetic behavior for <b>1</b> and dominant antiferromagnetic behavior for <b>2</b>–<b>5</b>. Of particular interest is <b>4</b>, which is the first manganese chalcogenide showing spin-canting characteristic

Design Strategy for Improving Optical and Electrical Properties and Stability of Lead-Halide Semiconductors

Broad absorption, long-lived photogenerated carriers, high conductance, and high stability are all required for a light absorber toward its real application on solar cells. Inorganic–organic hybrid lead-halide materials have shown tremendous potential for applications in solar cells. This work offers a new design strategy to improve the absorption range, conductance, photoconductance, and stability of these materials. We synthesized a new photochromic lead-chloride semiconductor by incorporating a photoactive viologen zwitterion into a lead-chloride system in the coordinating mode. This semiconductor has a novel inorganic–organic hybrid structure, where 1-D semiconducting inorganic lead-chloride nanoribbons covalently bond to 1-D semiconducting organic π-aggregates. It shows high stability against light, heat, and moisture. After photoinduced electron transfer (PIET), it yields a long-lived charge-separated state with a broad absorption band covering the 200–900 nm region while increasing its conductance and photoconductance. This work is the first to modify the photoconductance of semiconductors by PIET. The observed increasing times of conductivity reached 3 orders of magnitude, which represents a record for photoswitchable semiconductors. The increasing photocurrent comes mainly from the semiconducting organic π-aggregates, which indicates a chance to improve the photocurrent by modifying the organic component. These findings contribute to the exploration of light absorbers for solar cells

Structural Diversity, Optical and Magnetic Properties of a Series of Manganese Thioarsenates with 1,10-Phenanthroline or 2,2′-Bipyridine Ligands: Using Monodentate Methylamine as an Alkalinity Regulator

The exploration in two hydro­(solvo)­thermal reaction systems As/S/Mn²⁺/phen/methylamine aqueous solution and As/S/Mn²⁺/2,2′-bipy/H₂O affords five new manganese thioarsenates with diverse structures, namely, (CH₃NH₃)­{[Mn­(phen)₂]­(As^VS₄)}·phen (<b>1</b> and <b>1′</b>), (CH₃NH₃)₂{[Mn­(phen)]₂(As^VS₄)₂} (<b>2</b>), {[Mn­(phen)₂]­(As^III₂S₄)}_<i>n</i> (<b>3</b>), {[Mn­(phen)]₃(As^IIIS₃)₂}·H₂O (<b>4</b>), and {[Mn­(2,2′-bipy)₂]₂(As^VS₄)}­[As^IIIS­(S₅)] (<b>5</b>). Compound <b>1</b> comprises a {[Mn­(phen)₂]­(As^VS₄)}⁻ complex anion, a monoprotonated methylamine cation and a phen molecule. Compound <b>2</b> contains a butterfly like {[Mn­(phen)]₂(As^VS₄)₂}^2– anion charge compensated by two monoprotonated methylamine cations. Compound <b>3</b> is a neutral chain formed by a helical ¹_∞(As^IIIS₂^–) <i>vierer</i> chain covalently bonds to [Mn^II(phen)]²⁺ complexes via all its terminal S atoms. Compound <b>4</b> features a neutral chain showing the stabilization of noncondensed (As^IIIS₃)^3– anions in the coordination of [Mn^II(phen)]²⁺ complex cations. Compound <b>5</b> features a mixed-valent As^III/As^V character and an interesting chalcogenidometalates structure, where a polycation formed by the connection of two [Mn­(2,2′-bipy)₂]²⁺ complex cation and a (As^VS₄)^3– anion acts as a countercation for a polythioarsenate anion, [As^IIIS­(S₅)]⁻. The title compounds exhibit optical gaps in the range 1.58–2.48 eV and blue photoluminescence. Interestingly, compound <b>1</b> displays a weak second harmonic generation (SHG) response being about 1/21 times of KTP (KTiOPO₄). Magnetic measurements show paramagnetic behavior for <b>1</b> and dominant antiferromagnetic behavior for <b>2</b>–<b>5</b>. Of particular interest is <b>4</b>, which is the first manganese chalcogenide showing spin-canting characteristic