Structural Diversity of Coordination Polymers Based on a Heterotopic Ligand: Cu(II)-Carboxylate vs Cu(I)-Thiolate

Effect of the 1D/2D dimensionality in copper and silver thiolate coordination polymers on their photophysical properties

A series of four new copper and silver-thiolate, [M(m-SPhCO2R)]n (M = Cu, Ag and R = H, Me), coordination polymers is reported. The study shows that the hydrogen bonding between the carboxylic acids directs the formation of a 2D structure associated with poor photoemission, while the steric hindrance of the ester groups allows the assembly of a 1D network coupled with bright luminescence.

Single Crystal to Single Crystal Transformation of Porous Materials Based on Zinc Nodes and Mercaptobenzoic Acid

Porous coordination polymers (PCPs) are an excellent class of porous crystalline materials with tunable properties and intriguing potential applications spanning multiple disciplines. In this work, we report the synthesis and characterization of a PCP (HI-103) based on 4,4'-dithiodibenzoic acid ligand and zinc nitrate with two DMF molecules residing in the porous network. The stability of the porous network was analyzed by heating the compound at 60.0 °C for two days, and the structural analysis revealed a new PCP (HI-104) was formed with one of the DMF molecules, indicating a single-crystal to single-crystal (SCSC) transformation. The solvent molecules were completely removed by extensive drying (HI-103-dry), and the integrity of the porous network was verified by powder X-ray diffraction (PXRD) and thermogravimetric analysis. The reversibility of SCSC transformation was confirmed by treating HI-103-dry with DMF molecules, resulting in HI-103 after five days. The adsorption studies of HI-103-dry with other solvents revealed that SCSC transformation was not observed for DMA and DEA, but some structural changes were observed in the presence of DMSO. The adsorption studies performed in the presence of an equimolar mixture of DMF, DMA, and DMA indicated that HI-103-dry could selectively adsorb DMF molecules from the analogous mixture.

Light Emission in 2D Silver Phenylchalcogenolates

Silver phenylselenolate (AgSePh, also known as "mithrene") and silver phenyltellurolate (AgTePh, also known as "tethrene") are two-dimensional (2D) van der Waals semiconductors belonging to an emerging class of hybrid organic-inorganic materials called metal-organic chalcogenolates. Despite having the same crystal structure, AgSePh and AgTePh exhibit a strikingly different excitonic behavior. Whereas AgSePh exhibits narrow, fast luminescence with a minimal Stokes shift, AgTePh exhibits comparatively slow luminescence that is significantly broadened and red-shifted from its absorption minimum. Using time-resolved and temperature-dependent absorption and emission microspectroscopy, combined with subgap photoexcitation studies, we show that exciton dynamics in AgTePh films are dominated by an intrinsic self-trapping behavior, whereas dynamics in AgSePh films are dominated by the interaction of band-edge excitons with a finite number of extrinsic defect/trap states. Density functional theory calculations reveal that AgSePh has simple parabolic band edges with a direct gap at Γ, whereas AgTePh has a saddle point at Γ with a horizontal splitting along the Γ-N₁ direction. The correlation between the unique band structure of AgTePh and exciton self-trapping behavior is unclear, prompting further exploration of excitonic phenomena in this emerging class of hybrid 2D semiconductors.

Mercury removal efficiency of disulfide- and thiol-functionalized lanthanide coordination polymers

To compare efficiency of disulfide and thiol groups in removing mercury from aqueous medium without noteworthy influence from structural differences, a series of new [Ln^III(dtba)_1.5(H₂O)₂] (Ln^III = Eu^III (I), Gd^III (II) and Tb^III (III), H₂dtba = 4,4'-dithiobenzoic acid) were synthesized and characterized. The single crystal structure of I was elucidated and is described. Reaction of II with hydrazine gave II^SH containing disulfide and thiol groups. Experimental data confirmed the preserved framework structure and the co-existing of disulfide and thiol groups in II^SH. Robustness of II and II^SH over a wide range of pH (2-10) was confirmed and their mercury removal performances at different pH were evaluated in terms of removal efficiencies (%R), equilibrium uptake capacities (q_e) and distribution constant (K_d). The dependence of these parameters on pH is reported. The best values of %R, q_e and K_d could be achieved at pH 10 at which surfaces of the adsorbents were negatively charged; 86%R, 429 mg g^-1, and 6.04 × 10³ mL g^-1 (II), and 98%R, 490 mg g^-1 and 5.08 × 10⁴ mL g^-1 (II^SH). At pH 7, influences of the initial concentration of mercury on performances of the adsorbents as well as the adsorption isotherms and kinetics were examined from which the better performance of II^SH has been concluded. The characterization of the adsorptions by the Langmuir model and the pseudo-second-order kinetic as well as their excellent consistency with the experimental data are included. At neutral pH, selectivity to the adsorption of mercury and tolerance to common anions were illustrated. The better affinity between mercury and thiol group and therefore its contribution to the better performance of II^SH was then ascertained by a computational study.

Layered Organic Metal Chalcogenides (OMCs): From Bulk to Two-Dimensional Materials

The modification of inorganic two-dimensional (2D) materials with organic functional motifs is in high demand for the optimization of their properties, but it is still a daunting challenge. Organic metal chalcogenides (OMCs) are a type of newly emerging 2D materials, with metal chalcogenide layers covalently anchored by long-range ordered organic functional motifs, these materials are extremely desirable but impossible to realize by traditional methods. Both the inorganic layer and organic functional motifs of OMCs are highly designable and thus provide this type of 2D materials with enormous variety in terms of their structure and properties. This Minireview aims to review the latest developments in OMCs and their bulk precursors. Firstly, the structure types of the bulk precursors for OMCs are introduced. Second, the synthesis and applications of OMC 2D materials in photoelectricity, catalysis, sensors, and energy transfer are explored. Finally, the challenges and perspectives for future research on OMCs are discussed.

Fluorescence sensing of nitrophenol explosives using a two-dimensional organic-metal chalcogenide fully covered with functional groups

A new 2D fluorescent organic-metal chalcogenide (OMC), CdClHT (HT = 4-hydroxythiophenol), evenly covered with phenol groups is reported. CdClHT represents unparalleled selectivity and the highest sensitivity towards 2,4,6-trinitrophenol (TNP) (K_SV = 2.16 × 10⁷ m^-1, experimental LOD = 2 nM), among all reported 2D conjugated polymer (CP) luminescent detectors.

Rational and site-selective formation of coordination polymers consisting of d10 coinage metal ions with thiolate ligands using a metal ion-doped polymer substrate

Here, we report an interfacial approach for fabricating coordination polymers (CPs) consisting of d10 coinage metal ions with thiolate ligands on a polymer substrate. It was found that CPs were selectively formed on the polymer substrate, resulting in the formation of CP-based thin films. In addition, utilizing a mixed metal ion-doped polymer substrate leads to the formation of mixed-metal CP-based films.

Size and Quality Enhancement of 2D Semiconducting Metal-Organic Chalcogenolates by Amine Addition

The use of two-dimensional (2D) materials in next-generation technologies is often limited by small lateral size and/or crystal defects. Here, we introduce a simple chemical strategy to improve the size and overall quality of 2D metal-organic chalcogenolates (MOCs), a new class of hybrid organic-inorganic 2D semiconductors that can exhibit in-plane anisotropy and blue luminescence. By inducing the formation of silver-amine complexes during a solution growth method, we increase the average size of silver phenylselenolate (AgSePh) microcrystals from <5 μm to >1 mm, while simultaneously extending the photoluminescence lifetime and suppressing mid-gap emission. Mechanistic studies using ⁷⁷Se NMR suggest dual roles for the amine in promoting the formation of a key reactive intermediate and slowing down the final conversion to AgSePh. Finally, we show that amine addition is generalizable to the synthesis of other 2D MOCs, as demonstrated by the growth of single crystals of silver 4-methylphenylselenolate (AgSePhMe), a novel member of the 2D MOC family.

The alloying-induced electrical conductivity of metal-chalcogenolate nanowires

Alloying is one of the most effective strategies to change the properties of inorganic-organic hybrid materials, but there are few reports of the alloying of one-dimensional nanowires with precise atomic structure due to the difficulties in obtaining the single crystals of nanowires themselves. Herein, we describe the synthesis and characterization of an alloyed one-dimensional Ag-Cu nanowire [Ag_2.5Cu_1.5(S-Adm)₄]_n. Compared with the unalloyed [Ag₄(S-Adm)₄]_n, our novel alloyed nanowire exhibits good conductivity, and its resistivity (as a powder) was determined to be 107 Ω m by impedance analysis-consistent with that of a semiconductor. Accordingly, based on these properties combined with its excellent thermal stability and high-yielding, gram-scale synthesis, [Ag_2.5Cu_1.5(S-Adm)₄]_n is proposed for electronic-device applications.

Dynamic porous coordination polymers built-up from flexible 4,4'-dithiodibenzoate and rigid N-based ligands

Herein we report the design, synthesis, structural characterisation and functional testing of a series of Cu(ii) coordination polymers containing flexible 4,4'-dithiodibenzoate ligand (4,4'-DTBA), with or without auxiliary N-donor ligands. Reaction of Cu(ii) with 4,4'-DTBA yielded a 1D coordination polymer (1) based on Cu(ii) paddlewheel units connected by 4,4'-DTBA, to form cyclic loop chains with intramolecular voids that exhibit reversible structural transformations upon subsequent solvent exchange in methanol to afford a new, crystalline, permanently-porous structure (1'). However, when the same reaction was run with pyridine, it formed a porous 2D coordination polymer (2). We have attributed the difference in dimensionality seen in the two products to the coordination of pyridine on the axial site of the Cu(ii) paddle-wheel, which forces flexible 4,4'-DTBA to adopt a different conformation. Reactions in the presence of 4,4'-bipyridine (4,4'-bpy) afforded two new, flexible, 2D coordination polymers (3 & 4). Lower concentrations of 4,4'-bpy afforded a structure (3) built from 1D chains analogous to those in 1 and connected through 4,4'-bpy linkers coordinated to the axial positions. Interestingly, 3 showed reversible structural transformations triggered by either solvent exchange or thermal treatment, each of which yielded a new crystalline and permanently porous phase (3'). Finally, use of higher concentrations of 4,4'-bpy led to a coordination polymer (4) based on a distorted CuO₃N₂ trigonal bipyramid, rather than on the Cu(ii) paddlewheel. The connection of these motifs by 4,4'-DTBA resulted in a zig-zag 1D chain connected through 4,4'-bpy ligands to form a porous 2D network. Interestingly, 4 also underwent reversible thermal transformation to yield a microporous coordination polymer (4').

Transparent and luminescent glasses of gold thiolate coordination polymers

Obtaining transparent glasses made of functional coordination polymers (CPs) represents a tremendous opportunity for optical applications. In this context, the first transparent and red-emissive glasses of gold thiolate CPs have been obtained by simply applying mechanical pressure to amorphous powders of CPs. The three gold-based CP glasses are composed of either thiophenolate [Au(SPh)] n , phenylmethanethiolate [Au(SMePh)] n or phenylethanethiolate [Au(SEtPh)] n . The presence of a longer alkyl chain between the thiolate and the phenyl ring led to the formation of glass with higher transparency. The glass transitions, measured by thermomechanical analysis (TMA), occurred at lower temperature for CPs with longer alkyl chains. In addition, all three gold thiolate glasses exhibit red emission at 93 K and one of them, [Au(SMePh)] n , remains luminescent even at room temperature. An in-depth structural study of the amorphous gold thiolates by XRD, PDF and EXAFS analysis showed that they are formed of disordered doubly interpenetrated helical chains. These d10 metal-based compounds represent the first examples of transparent and luminescent CP glasses.

Solvent-Induced Structural Diversity and Magnetic Research of Two Cobalt(II) Complexes

The solvent-induced topological and structural diversities of two Co(II) complexes, namely, [Co(L)₂(SCN)₂] (Co1) and [Co₂(L)₂(SCN)(OAc)₃] (Co2) (L = 8-methoxyquinoline), were comparatively analyzed. Certain proportions of L, Co(OAc)₂·4H₂O, and NaSCN were mixed and dissolved in CH₃OH at 60 °C to obtain complex Co1. Complex Co2, an asymmetric dinuclear compound, was obtained by simply replacing CH₃OH with CH₃CN as the solvent. The Co(II) ion in complex Co1 was coordinated by the N₄O₂ mode provided by two L ligands and two SCN^- anions. The two Co(II) ions in Co2 were in the N₂O₄ and NO₅ coordination environment and were linked by two μ₂-OAc^- bridges and one rare μ₃-OAc^- bridge. Weak interaction analysis revealed that complexes Co1 and Co2 exhibited 6-connected shp and 14-connected fcu nets, respectively. Magnetic studies showed that Co1 demonstrated single-ion magnet behavior under 2000 Oe. These behaviors are indicative of clearly field-induced single-ion magnetic behavior with U _eff = 34.7(2) K and τ₀ = 2.7(2) × 10^-7 s under 2000 Oe dc field, respectively. By contrast, Co2 lacked frequency dependence under zero-field conditions. Electrospray ionization mass spectrometry indicated that two complexes were stable in N,N-dimethylformamide.

New Lamellar Silver Thiolate Coordination Polymers with Tunable Photoluminescence Energies by Metal Substitution

The structures of two lamellar silver thiolate coordination polymers [Ag( p-SPhCO₂H)] _n (1) and [Ag( p-SPhCO₂Me)] _n (2) are described for the first time. Their inorganic part is composed of distorted Ag₃S₃ honeycomb networks separated by noninterpenetrated thiolate ligands. The main difference between the two compounds arises from dimeric hydrogen bonds present for the carboxylic acids. Indepth photophysical studies show that the silver thiolates exhibit multiemission properties, implying luminescence thermochromism. More interestingly, the synthesis of a heterometallic lamellar compound, [Ag_0.85Cu_0.15( p-SPhCO₂H)] _n (3), allows to obtain mixed metal thiolate coordination polymers and to tune the photophysical properties with the excitation wavelengths from a green vibronic luminescence to a single red emission band.

Synthesis of a Cd(ii) based 1D coordination polymer by in situ ligand generation and fabrication of a photosensitive electronic device

A 1D coordination polymer, which has optoelectronic device applications, has been synthesized by in situ ligand formation.