Influence of O-H⋅⋅⋅Pt interactions on photoluminescent response in the (Et4N)2{[Pt(bph)(CN)2][phenylene-1,4-diresorcinol]} framework

Tunable photoluminescence (PL) is one of the hot topics in current materials science, and research performed on the molecular phases is at the forefront of this field. We present the new (Et4N)2[PtII(bph)(CN)2]⋅rez3⋅1/3H2O (Pt2rez3) (bph=biphenyl-2,2'-diyl; rez3=3,3",5,5"-tetrahydroxy-1,1':4',1"-terphenyl, phenylene-1,4-diresorcinol coformer, a linear quaternary hydrogen bond donor) co-crystal salt based on the recently appointed promising [PtII(bph)(CN)2]2- luminophore. Within the extended hydrogen-bonded subnetwork [PtII(bph)(CN)2]2- complexes and rez3 coformer molecules form two types of contacts: the rez3O-H⋅⋅⋅Ncomplex ones in the equatorial plane of the complex and non-typical rez3O-H⋅⋅⋅Pt ones along its axial direction. The combined structural, PL, and DFT approach identified the rez3O-H⋅⋅⋅Pt synthons to be crucial in promoting the noticeable uniform redshift of bph ligand centered (LC) emission compared to the LC emission of the (Et4N)2[PtII(bph)(CN)2]⋅H2O (Pt2) precursor, owing to the direct interference of the phenol group with the PtII-bph orbital system via altering the CT processes within. The high-resolution emission spectra for Pt2 and Pt2rez3 were successfully reproduced at 77 K by using the Franck-Cordon expressions. The possibility to tune PL properties along the plausible continuum of rez3O-H⋅⋅⋅Pt synthons is indicated, considering various scenarios of molecular occupation of the space above and below the complex plane.

Polyoxometalate-Viologen Thermochromic Hybrids for Organic Amine Detectors and Memristors with Temperature-Regulating Resistance Switching Characteristics

There are relatively few reports on the combination of viologen and polyoxometalates (POMs). Herein, we successfully synthesized three viologen-POM-based compounds by in situ transformation of ligands under hydrothermal conditions, namely, {M^II(1,4-cby)₂[H₂(γ-Mo₈O₂₆)]}·nH₂O (1: M = Ni, n = 4; 2: M = Co, n = 6), and [Ni^II(1,3-cby)(H₂O)₄(β-Mo₈O₂₆)_0.5]·2H₂O (3) (1,4-cby·Cl = 1-(4-carboxy-benzyl)-[4,4']bipyridinyl-1-ium, 1,3-cby·Cl = 1-(3-carboxy-benzyl)-[4,4']bipyridinyl-1-ium). Isostructural compounds 1 and 2 exhibit two-dimensional (2D) layer structures with POMs as linking nodes, while compound 3 shows a one-dimensional (1D) metal-organic chain with dissociative POM anions. When the temperature increases, compounds 1-3 show good reversible thermochromism properties and also have a fluorescence quenching effect. Moreover, compounds 1-3 can also be used as detectors for organic amines, especially in the atmosphere of ammonia, ethylenediamine, and diethylamine with an obvious discoloration effect. In addition, compound 1 was used as a material for the preparation of memristors with superior properties (distinct temperature-adjusted resistive switching properties). It shows bipolar resistive switching (RS) behavior at different temperatures of 20, 50, and 100 °C. The results show that the 1-based memristor has good thermal stability, which is important for high-temperature environment applications. It also shows that crystalline viologen-POM-based compounds are ideal candidates for making memristors.

Photochromic Polyoxometalate/Perylenediimide Donor-Acceptor Hybrid Crystals with Interesting Luminescent Properties

The self-assembly of electron-deficient protonated N, N'-dipyridyltetrachloroperylenediimide (4Cl-DPPDI) and electron-rich polyoxometalate acids H_nXM₁₂O₄₀ (POMs; X = P or Si; M = W or Mo) resulted in four isomorphous donor-acceptor hybrid crystals 1-4 with segregated POM anions and one-dimensional racemic hydrogen-bonded 4Cl-DPPDI networks as electron-donor and -acceptor components, respectively. Because of the compact contacts between the POM anions and 4Cl-DPPDI tectons induced by anion-π interactions, besides enhanced photochromism, these four unique isostructural hybrids exhibited unusual room-temperature phosphorescence (RTP) emissions. More interestingly, owing to the facial compact contacts of two racemic 4Cl-DPPDI tectons induced by lone pair-π-assisted π-π interactions, they also showed unprecedented photon upconversion by triplet-triplet annihilation (TTA).

Photochromic and Room Temperature Phosphorescent Donor-Acceptor Hybrid Crystals Regulated by Core-Substituted Naphthalenediimides

Donor-acceptor (D-A) hybrid crystals are an emerging kind of crystalline hybrid material composed of semiconductive inorganic donors and organic acceptors. Except for the intrinsic photochromism, recently we have reported that the anion-π polyoxometalate (POM)/naphthalenediimide (NDI) hybrid crystals could produce an interesting room temperature phosphorescence (RTP) quantum yield up to 7.2%. Herein, we extended into core-substituted NDIs and anticipated the regulation of their photochromic and RTP properties. Thus, two hybrid crystals, namely (H₄BDMPy-Br₂NDI)·(NMP)₄·(HPW₁₂O₄₀) (1) and (H₄BDMPy-I₂NDI)·(HPW₁₂O₄₀) (2) (H₂BDMPy-Br₂NDI: N,N'-bis(3,5-dimethylpyrazolyl)-2,6-dibromo-1,4,5,8-naphthalenediimide and H₂BDMPy-I₂NDI: N,N'-bis(3,5-dimethylpyrazolyl)-2,6-diiodide-1,4,5,8-naphthalenediimide), have been synthesized from phosphotungstic anions (PW₁₂O₄₀^3-) and Br or I core-substituted NDIs. Compared to the core-unsubstituted analogues (H₄BDMPy-NDI)·(NMP)₄·(HPW₁₂O₄₀) (3), 2 with photosensitive iodine substituents is more sensitive to light, which can become discolored under natural light. As a result of the heavy-atom effect, hybrid 1 exhibits remarkable RTP with the quantum yield up to 10.2% and a lifetime of 1.14 ms.

Exploring the structure-property schemes in anion-π systems of d-block metalates

Anion-π based compounds, materials, and processes have gained significant interest due to the diversity of their aesthetic non-covalent synthons, and thanks to their significance in biological systems, catalytic processes, anion binding and sensing, or the supramolecular organization of hierarchical architectures. While systems based on typical inorganic anions or organic residues have been widely reviewed in recent years, those involving anionic d metal comlexes as the main components have been treated with a rather secondary interest. However, actively exploring the new systems of the latter type we have recognized systematic advances in the field. As a result, in the current review we describe the landscape that has recently emerged. Focusing on the established groups of π-acidic species, i.e. polycarbonitirles, polyazines, polyazine N-oxides, diimide derivatives, fluoroarenes, and nitroarenes, we explore and discuss anion-π crystal engineering together with the structure-property schemes important from the standpoint of charge transfer (CT) and electron transfer (ET), magnetism, luminescence, reactivity and catalysis, and the construction of core-shell crystalline composites.

Impact of diffusion methods and metal cations on photochromic three-component D-A hybrid heterostructures

D-A hybrid heterostructures are an attractive class of hybrid complexes composed of semiconducting organic and inorganic components, which make them potential candidates for applications in the photoelectric fields, particularly as photochromic materials. Herein, we report that the combination of metal cations (M = Zn2+ or Cd2+), silicomolybdic anions, and N,N-di(4-pyridyl)-1,4,5,8-naphthalene diimide (DPNDI) via two diffusion methods (A and B) led to four three-component D-A hybrid heterostructures with silicomolybdic anions as electron donors, and one-dimensional (1-D) naphthalenediimide coordination networks of different metal cations, [Zn2(DPNDI)2(H2O)4]·(SiMo12O40) (1-A and 1-B) and [Cd2(DPNDI)2(H2O)4]·(SiMo12O40) (2-A and 2-B), as electron acceptors. Although the different diffusion methods, 1-B, 2-A and 2-B, are isostructures with close cell parameters. Due to the different ionic radii and electronegativity of metal cations in isostructural 1-B and 2-B, they exhibit different electron-transfer photochromic behaviors. This study paves a new path for designing novel photochromic materials through such third-component metal cations.

Semiconductive donor promoted photochromism of iodoplumbate hybrids

The entirely different photochromic behaviors of two iodoplumbate hybrids indicate the driving role of excitation of the PbI₃⁻ chain donor and the negative role of charge transfer in photoinduced electron transfer and photochromism.

A heterometallic D–A hybrid heterostructural framework with enhanced visible-light photocatalytic properties

A heterometallic D–A hybrid heterostructural framework from the ternary combination of CuI, lanthanide cations and viologen tectons exhibited enhanced photocatalytic activities for degradation of organic dyes.

Bifunctional photo- and vapochromic behaviors of a novel porous zwitterionic metal–organic framework

A novel porous zwitterionic metal–organic framework shows photo- and vapochromic behaviors with high sensitivity for sensing NH₃, ethylamine, and n-propylamine.

Reunderstanding the photoinduced charge transfer process of ammonium polyoxomolybdate

Protonation of 4-phenylpyridine can realize photoinduced electron transfer from the carboxyl group to 4-phenylpyridine and photochromism of ammonium polyoxomolybdate without proton transfer.

The impact of metal cations on the photochemical properties of hybrid heterostructures with infinite alkaline-earth metal oxide clusters

Two hybrid heterostructures with infinite alkaline-earth metal oxide clusters exhibited diametrically opposite photochromic sensitivities and photocatalytic activities, which are mainly related to the HOMO levels of inorganic clusters.

A novel photochromic metal-organic framework with good anion and amine sensing

A novel metal-organic hybrid photochromic compound [Zn (CV) (L2)]·2H2O (1) (CV = N,N'-4,4'-bipyridiniodipropionate, H2L2 = isophthalic acid) has been synthesized solvothermally. Compound 1 features a two-dimensional (2D) framework structure, exhibiting photochromic properties under sunlight and UV irradiation with an obvious color change from colorless to dark blue. Meanwhile, the luminescence properties of 1 were investigated, and the results suggested that 1 has good properties of detecting dichromate ions. Furthermore, compound 1 shows different color changes when exposed to different alkyl-amines, and 1 can also be deposited into paper to use as portable test strips. This work can be applied to practical applications as a multifunctional detector against light and chemicals.

Unprecedented five-fold interpenetrated donor–acceptor hybrid heterostructure induced by anion–π interactions

An unprecedented five-fold interpenetrated D–A hybrid heterostructural complex has been constructed, wherein anion–π interactions play a key role in its interpenetration and photoinduced electron transfers.

A novel multifunction photochromic metal–organic framework for rapid ultraviolet light detection, amine-selective sensing and inkless and erasable prints

The system shows efficient and fast low intensity ultraviolet light detection, amine-selective sensing and also be used as inkless and erasable print.

A bicontinuous donor–acceptor hybrid heterostructure based on coordination and cation–π interactions

A bicontinuous donor–acceptor hybrid heterostructure based on metal pseudohalides exhibits enhanced efficient photocatalytic degradation activities towards organic pollutants upon visible light irradiation.

Anion–π interactions of highly π-acidic dipyridinium-naphthalene diimide salts

A highly π-acidic dipyridinium-naphthalene diimide acceptor shows anion–π interactions with halides and PF₆⁻.

The impact of metal ions on photoinduced electron-transfer properties: four photochromic metal–organic frameworks based on a naphthalenediimide chromophore

Four photochromic MOFs show that electron-withdrawing capabilities of metal ions play a significant role in tuning the photosensitivity of photochromic MOFs.

Exceptional photosensitivity of a polyoxometalate-based charge-transfer hybrid material

Exceptional light sensitivity was realized in a polyoxometalate-based hybrid material due to cooperative multicomponent molecular charge-transfer interactions taking place in this material. The π-acidic NDI linkers and POM clusters in the hybrid material were designed as photosensors and electronic reservoirs, respectively.

Experimental investigation of anion–π interactions – applications and biochemical relevance

Anion–π interactions, intuitively repulsive forces, turned from controversial to a well-established non-covalent interaction over the past quarter of a century.

Crystal-to-crystal transformation of fishnet-like layered compounds: a self-locking structure with position-variable intercalated molecules

Fishnet-like layered compounds crystallized with anthracene (ANT) molecules between their layers and crystallization solvents at their hexagonal columnar pores; these complexes undergo a solvent-release crystal-to-crystal transformation involving the migration of a portion of the ANT molecules from between the layers to the hexagonal pores.

The impact of lone pair–π interactions on photochromic properties in 1-D naphthalene diimide coordination networks

Due to the different lone pair–π interactions between the capped halogen atoms and electron-deficient naphthalene diimide moieties in three isostructural coordination networks, they exhibit different electron-transfer photochromic behaviours upon irradiation.