Two-dimensional Supramolecular Network Research Articles

Assembly-Driven Oxidative Degradation of Melarsomine Triggered by Cyanuric Acid.

Molecular self-assembly can trigger or regulate specific chemical reactions that would otherwise be infeasible when molecules exist individually. Supramolecular structures can significantly affect the rate of chemical reactions; therefore, optimizing supramolecular structures by manipulating intermolecular interactions is crucial for achieving the desired reactivity. Melamine is known to form hydrogen bonds with cyanuric acid, resulting in the formation of a supramolecular network. Melarsomine, an effective medication for heartworm treatment in dogs, contains a melamine moiety. It has yet to be studied how the chemical stability of melarsomine is affected by its interaction with other molecules. Herein, we report the formation of a two-dimensional supramolecular network between melarsomine and cyanuric acid via hydrogen bonds. This network structure captures dissolved oxygen in an aqueous solution, accelerating the oxidative degradation of melarsomine.

Syntheses and photochemically antibiotic degradation of two Co(II)-based coordination polymers

Two new Co(II)-based coordination polymers (CPs), designated as [Co2(bbp)4(1,3-bdc)4]n(1) and [Co(bbp)3(NO3)2(H2O)]n(2) (bbp = 3,5-bis(benzoimidazo-1-ly) pyridine; 1,3-H2bdc = 1,3-benzenedicarboxy acid), were synthesized using a dual ligand approach. The characterization of these CPs involved single- crystal -XRD, UV–visible, FT-IR, and TGA analysis. Both CPs 1 and 2 exhibit a distorted octahedral geometry. Both 1 and 2 show a 1D ladder chain, and this chain-like structure undergoes further development into a more intricate two-dimensional (2D) supramolecular network. The thermal stability analysis revealed that 1 and 2 are stable at temperatures of 119 °C and 286 °C, respectively, with no significant mass loss. Notably, both CPs displayed semiconducting properties. The photocatalytic degradation capabilities of CPs 1 and 2 were investigated against antibiotics such as metronidazole (MDZ), Tinidazole (TDZ), ornidazole (ODZ), and furazolidone (FZD). CP 1 exhibits exceptional photocatalytic activity against FZD. A dosage of 5 mg/L of CP 1 resulted in a remarkable degradation efficiency of 92.2 % for 40 ppm FZD. Additionally, a proposed photodegradation mechanism was investigated through radical trapping experiments.

Syntheses, structures and luminescent properties of five new Ag(I)-based coordination polymers

In this work, five Ag(I)-based coordination polymers (CPs), namely, [Ag(HL)(H2L)]n (1), [Ag(HL)(2,2′-bpy)(H2O)0.5] (2), [Ag(HL)(phen)(H2O)0.5] (3), {[Ag2(HL)2(4,4′-bpy)(H2O)2]∙H2O} (4) and [Ag(HL)(thpy)]n (5), were synthesized under hydrothermal conditions (H2L = 1-(3-carboxybenzyl)-1H-pyrazole-4-carboxylic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, 4,4′-bpy = 4,4′-bipyridine and thpy = 2-(2-thienyl)pyridine). These coordination polymers were characterized by single-crystal X-ray diffraction, elemental analyses, infrared spectroscopy, thermogravimetric analyses and powder X-ray diffraction. Compound 1 displays a one-dimensional (1D) chain structure which can be further extended into a three-dimensional (3D) supramolecular structure via intermolecular hydrogen bond. In compounds 2 and 3, the binuclear zero dimensional (0D) units are extended to 3D supramolecular frameworks by intermolecular hydrogen bond and π–π stacking interaction. In compound 4, the 0D units constructed by HL− anions, 4,4′-bpy and metal ions are expanded to form a two-dimensional (2D) supramolecular network. Compound 5 shows a different 2D supramolecular structure extended from 1D chain by intermolecular hydrogen bond. The results suggest that organic ligand plays a key role in the formation of the final structures. The solid-state luminescent properties of compounds 1–5 were studied in detail. The results show that the luminescent color of compounds 1–5 can be tunable by varying excitation wavelengths.

Stoichiometry-Directed Two-Level Hierarchical Growth of Lanthanide-Based Supramolecular Nanoarchitectures.

The design of a well-ordered arrangement of atoms on a solid surface has long been sought due to the envisioned applications in many different fields. On-surface synthesis of metal-organic networks is one of the most promising fabrication techniques. Hierarchical growth, which involves coordinative schemes with weaker interactions, favours the formation of extended areas with the desired complex structure. However, the control of such hierarchical growth is in its infancy, particularly for lanthanide-based architectures. Here the hierarchical growth of a Dy-based supramolecular nanoarchitecture on Au(111) is described. Such an assembly is based on a first hierarchical level of metallo-supramolecular motifs, which in a second level of hierarchy self-assemble through directional hydrogen bonds, giving rise to a periodic two-dimensional supramolecular porous network. Notably, the size of the metal-organic based tecton of the first level of hierarchy can be tailored by modifying the metal-ligand stoichiometric ratio.

Self-Assembly of Triphenylamine Macrocycles and Co-assembly with Guest Molecules at the Liquid-Solid Interface Studied by STM: Influence of Different Side Chains on Host-Guest Interaction.

The side chains of macrocyclic molecules have a non-negligible effect on the two-dimensional (2D) supramolecular networks at the liquid-solid interface. In this study, we investigate the self-assembly behaviors of two conjugated triphenylamine macrocycles modified with different alkyl chains and construct the host-guest supramolecular nanopatterns on the highly oriented pyrolytic graphite with a scanning tunneling microscope. In combination with density functional theory calculations, how different side chains affect the host-guest interaction is discussed. This work provides insights into constructing a 2D host-guest dynamic co-assembly on the surface.

Field-induced single-ion magnet behavior in a hydrogen-bonded supramolecular cobalt(II) complex

Hydrogen-bonded supramolecular frameworks remain highly interesting for the development of novel porous materials. Herein a hydrogen-bonded supramolecular framework of a cobalt(II) complex, [Co(cpt)2(H2O)2] (Hcpt = 4-(p-carboxyphenyl)-1,2,4-triazole), was synthesized and structurally characterized. A single crystal X-ray diffraction (SC-XRD) study indicates that the monometallic Co2+ ion is located in a distorted octahedral geometry and the complex forms a two-dimensional supramolecular network stabilised by significant intermolecular N···H interactions. Variable-temperature PXRD and TGA analysis experiments revealed considerable thermal stability of the supramolecular framework of the CoII complex. Magnetic studies showed that the distorted octahedral Co2+ ion exhibits considerable easy-plane magnetic anisotropy with D = 22.3 cm−1, while field-induced single-ion magnet (SIM) behavior was evidenced at low temperature. The forgoing results further highlight that the hydrogen-bonded supramolecular framework could be used as a great platform for the development of molecular nanomagnets.

Heterobimetallic metallacrown of EuIIICuII5 with 5-methyl-2-pyrazinehydroxamic acid: Synthesis, crystal structure, magnetism, and the influence of CuII ions on the photoluminescent properties

A 3d-4f heterobimetallic metallacrown with the formula of [EuCu5(5mpzHA)5(NO3)3/2(H2O)6]2·3NO3·4H2O·5CH3OH (MC1) has been prepared using the stirring method from a mixture of 5-methyl-2-pyrazinehydroxamic acid (5mpzHA), Cu(AcO)2·H2O, and Eu(NO3)3·5H2O salts in methanol under reflux, which yielded single crystals after slow solvent evaporation. Single crystal X-ray diffraction analysis shows a crown-like [EuCu5(5mpzHA)5] core with the 15-MC-5 system, with five CuII and one EuIII ions occupying the rim and the dome of the crown, respectively. Water molecules oxygen atoms and one nitrate anion fill the coordination sphere around the EuIII ion, which exhibits a MFF-9 shape. The MC1 is made up of two [EuCu5(5mpzHA)5(NO3)3/2(H2O)6] metallacrown units connected by one coordinated nitrate ion, where intramolecular hydrogen bonding interactions generate aR86(18) supramolecular macrocycle leading a two-dimensional supramolecular network. The emission and excitation spectra of MC1 show the absence of EuIII emission and f-f transitions, probably due to the paramagnetic nature of the CuII ions which play a key role in quenching the fluorescence in MC1. The observed magnetic properties are attributed to antiferromagnetic interactions among the CuII ions within the metallacrown rim plus the depopulation of EuIII excited Stark sublevels. This magnetic behavior was also supported by the EPR spectroscopy which presents a superposition of signals of the termally populated state 7F1 of EuIII and CuII ions at room temperature and a sole signal of CuII ion at 4 K.

Experimental and computational structural studies of 5-substituted-3-(1-arylmethyl-1,2,3,6-tetrahydropyridin-4-yl)-1H-indoles

Four compounds (1–4) reported in our previous work as potential antipsychotics with affinity for dopamine D2 and serotonin 5-HT1A and 5-HT2A receptors, were now subjected to detailed structural characterization. The X-ray analysis conducted for studied compounds proved that interatomic distances and bond angles in their crystal structures lie within normal values. The indole group in all compounds is planar, whereas tetrahydropyridine moiety exhibits almost ideal or close to half-chair conformation and is slightly or significantly rotated in relation to the indole group plane by 9.49(1)°, 30.24(11)°, 7.43(6)° and 15.98(18)° in compounds 1–4, respectively. The R1 substituents of tetrahydropyridine group in all cases form a dihedral angle with the indole moiety with value ranging from 66.57(14)° (2) to 86.73(17)° (4). The crystal structure of 1 is stabilized by N–H···N hydrogen bonds and C–H···π interactions. The intermolecular C(12)−H(12B)···Cg(2) interactions form a supramolecular two-dimensional network. The molecules in the crystal of 2 are linked by N–H···N. The formed chains are additionally stabilized with C–H···S hydrogen bonds. In case of compound 3, molecule chains are formed by N–H···N hydrogen bonds and are further linked via C–H···O hydrogen bonds into layer. The crystal structure is also stabilized by intermolecular C–H···π interactions. The molecules of compound 4 are linked by N–H···N hydrogen bonds and further stabilized by intermolecular C–H···π interactions. Crystallographic analysis was complemented with computational studies, such as Frontier Molecular Orbital analysis, which indicated that all four compounds display similar chemical reactivity, regardless of different R1 and R2 substituents. In addition, the most reactive parts of the compounds appear to be the indole and double bond located in tetrahydropyridine moiety. Lastly, the calculations of electrostatic potential and non-covalent interactions have been performed.

Syntheses and magnetic properties of a series of discrete Ni(II)-Ln(III) heterometallic complexes based on 2,3-dichlorobenzoate and 2,2′-bipyridine

Herein, a series of zero-dimensional (0D) heterometallic complexes, [Ln2Ni2(2,3-DCB)10(2,2′-bpy)2] [Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Er (7) and Yb (8)], were obtained by the reactions of Ln(NO3)3·nH2O, Ni(NO3)2·6H2O, 2,3-dichlorobenzoic acid (2,3-HDCB), NaOH and 2,2′-bipyridine (2,2′-bpy) under solvothermal conditions. The structures of complexes 1–8 were determined by single-crystal X-ray diffraction and further characterized by elemental analysis, FT-IR, PXRD and TGA. Complexes 1–8 are isostructural, and display discrete linear tetranuclear cluster structures constructed from ten 2,3-DCB anions linking two Ln(III) and two Ni(II) ions by four types of coordination modes. Such linear tetranuclear molecules can be extended into a two-dimensional (2D) supramolecular network through π–π interactions between 2,3-DCB and 2,2′-bpy. The magnetic properties of complexes 1–8 were also studied.

Crystal structure and Hirshfeld surface analysis of trans-2,5-di-methyl-piperazine-1,4-diium tetra-chlorido-cobaltate(II).

In the title mol-ecular salt, (C6H16N2)[CoCl4], the complete dication is generated by crystallographic inversion symmetry and the piperazine ring adopts a chair conformation with the pendant methyl groups in equatorial orientations. The complete dianion is generated by crystallographic twofold symmetry. In the crystal, the (C6H16N2)2+ and [CoCl4]2- ions are linked by N-H⋯Cl and C-H⋯Cl hydrogen bonds, thereby forming a two-dimensional supra-molecular network. The Hirshfeld surface analysis and fingerprint plots reveal that the largest contributions to the crystal stability come from H⋯Cl/Cl⋯H (68.4%) and H⋯H (27.4%) contacts.

Synthesis, crystal structure and photophysical properties of chlorido-[2-(2',6'-di-fluoro-2,3'-bipyri-din-6-yl-κN 1)-6-(pyridin-2-yl-oxy-κN)phenyl-κC 1]platinum(II).

The title compound, [Pt(C21H12F2N3O)Cl], crystallizes with two crystallographically independent mol-ecules (A and B) in the asymmetric unit, which adopt similar conformations. The PtII atoms in both mol-ecules adopt distorted square-planar geometries, coordinated by one C and two N atoms from the tridentate 2',6'-di-fluoro-6-[3-(pyridin-2-yl-oxy)phen-yl]-2,3'-bi-pyridine ligand and a chloride anion: the C and Cl atoms are trans. In the crystal, C-H⋯Cl/F hydrogen bonds, F⋯π and weak π-π stacking inter-actions between adjacent A and B mol-ecules and between pairs of inversion-related B mol-ecules lead to the formation of a two-dimensional supra-molecular network lying parallel to the ab plane. The sheets are stacked along the c-axis direction and linked by F⋯π and weak π-π stacking inter-actions between pairs of inversion-related A mol-ecules, forming a three-dimensional supra-molecular network. The photoluminescence quantum efficiency of the title compound in the blue-green region of the visible region (λmax = 517 and 544 nm) is estimated to be ∼0.2-0.3, indicating that the title compound could be a suitable candidate as the emitting material in organic light-emitting diode (OLED) applications.

Synthesis, structure, fluorescence, electrochemical, and antioxidant studies of a new silver(I) complex with 2,6-bis(N-methylbenzimidazol-2-yl)pyridine

A new silver(I) complex of the type [Ag2(mbbp)2](pic)2·DMF·CH3OH [mbbp = 2,6-bis( N-methylbenzimidazol-2-yl)pyridine] is synthesized and analyzed using a range of spectroscopic and crystallographic techniques. This compound contains cationic Ag2(mbbp)2 dimers, in which the crossed eight-shaped structure is formed by two mbbp ligands bridging two silver(I) centers and Ag–Ag bonds. Two-dimensional supramolecular networks of the silver(I) complex are connected by π···π interactions and hydrogen bonds. Hirshfeld analyses are performed to support the aforementioned intermolecular interactions. The effect of π···π stacking interactions on the fluorescence properties of the complex is investigated. Cyclic voltammetry indicates two irreversible redox processes. In addition, an antioxidant assay in vitro demonstrates that the silver(I) complex displays excellent scavenging activity toward hydroxyl radicals.

Crystal structures, Hirshfeld atom refinements and Hirshfeld surface analyses of tris-(4,5-di-hydro-furan-2-yl)methyl-silane and tris-(4,5-di-hydro-furan-2-yl)phenyl-silane.

The title compounds, C13H18O3Si (1) and C18H20O3Si (2), represent functional-izable di-hydro-furan-ylsilanes, which permit substitution by a variety of nucleophiles. The crystal structures of 1 and 2 display weak inter-molecular C-H⋯O hydrogen-bonding inter-actions (qu-anti-fied by Hirshfeld surface analysis), leading to a two-dimensional supra-molecular network for 1 and a one-dimensional supra-molecular network for 2. The crystal structures of 1 and 2 were refined both on the basis of the independent atom model (IAM) and the Hirshfeld atom refinement (HAR) approach, and the results are comparatively discussed.

Multi-responsive luminescence sensing behaviour of a pair of temperature-dependent Cd(II) coordination polymers

Adopting the temperature-controlling synthesis strategy, a pair of temperature-dependent Cd(II) coordination polymers (CPs) with the mixed 5-amino-2,4,6-tribromoisophthalic acid (H2ATBIP) and 1,4-bis(triazol-1-ylmethyl)benzene (bbtz), {[Cd(HATBIP)2(bbtz)(H2O)2]·2H2O}n (1) and {[Cd(HATBIP)2(bbtz)2]·2H2O}n (2), were obtained using the typical solution-evaporation method at room temperature and under hydrothermal condition at 100 °C, respectively. The ligand bbtz in 1 exhibits a TT (trans–trans) conformation and links the adjacent Cd(II) atoms into a chain polymer. The hydrogen-bonded centrosymmetric ring R22(8) further holds the neighbouring chains into a two-dimensional (2D) supramolecular network. With the aid of the interlayer hydrogen and halogen bonding, a 3D supramolecular network with the “ABAB” packing mode is formed. In 2, the bbtz ligand bridges the adjacent Cd(II) ions, resulting in a 2D sql topological network with the Schläfli symbol of (44.62), in which the HATBIP− ligand arranges alternatingly on both sides of the layer. The ligand HATBIP− shows monodentate coordination mode in 1 and 2. The indirect band gap exists in 1 and 2. Both 1 and 2 show multi-responsive luminescence sensing behaviour toward the Fe3+ ion, the Cr(VI) (Cr2O72−/CrO42−) anions and some NACs. Interestingly, 1 and 2 demonstrate distinct structure-dependent tuneable sensing sensitivities for these analytes. 1 has higher sensing sensitivity with lower limit of detection (LOD) than that of 2 for the same analyte. The sensing mechanisms have been illustrated.

Structural Phase Transitions of Molecular Self-Assembly Driven by Nonbonded Metal Adatoms.

The involvement of metal atoms in molecular assemblies has enriched the structural and functional diversity of two-dimensional supramolecular networks, where metal atoms are incorporated into the architecture via coordination or ionic bonding. Here we present a temperature-variable study of the self-assembly of the 1,3,5-tribromobenzene (TriBB) molecule on Cu(111) that reveals the involvement of nonbonded adatoms in the molecular matrix. By means of scanning tunneling microscopy and noncontact atomic force microscopy, we demonstrate the molecular-level details of a phase transition of TriBB assembly from the close-packed to porous honeycomb structures at 78 K. This is an unexpected transformation because the close-packed phase is thermodynamically favored in view of its higher molecular density and more intermolecular bonds as compared to the honeycomb lattice. A comprehensive density functional theory calculation suggests that Cu adatoms should be involved in the formation of the honeycomb network, where the Cu adatoms help stabilize the molecular assembly via enhanced van der Waals interactions between TriBB molecules and the underlying substrate. Both calculation and experimental results suggest no chemical bonding or direct charge transfer between the adatoms and the molecules, thus the electronic characteristics of the Cu adatoms trapped in the molecular confinement are close to the intrinsic ones on a clean metal surface and different from those in the traditional coordination-bonded framework. The nonbonded metal adatoms embedded self-assemblies may complement the metal-organic coordination system and can be used to tailor the chemical reactivity and electronic properties of supramolecular structures.

C–H···π(metal–ligand ring) interaction in a mesaconate bridged Cd(II) 1-D coordination polymer: structural elucidation, theoretical study, and photophysical properties

A Cd(II)-based one-dimensional coordination polymer (1-D CP), [Cd2(mes)2(4-phpy)4] (1), was prepared using mesaconic acid (H2mes) and 4-phenyl pyridine (4-phpy) mixed ligand system. Compound 1 has been characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD) pattern and single crystal X-ray diffraction (SCXRD) techniques. Structural elucidation reveals a 1-D chain which contains a 14-membered metal-ligand ring composed of two mes ligands and two Cd(II) centers. Further, the 1-D chains are assembled into a two-dimensional (2-D) supramolecular network by C–H···π(metal-ligand ring) interactions. The fluorescence lifetime of 1 shows a good range of average lifetime. The theoretical band gap has also been calculated by density functional theory (DFT) computations, which shows that 1 may possess semiconducting properties.

Giant thermal expansion of a two-dimensional supramolecular network triggered by alkyl chain motion

Thermal expansion, the response in shape, area or volume of a solid with heat, is usually large in molecular materials compared to their inorganic counterparts. Resulting from the intrinsic molecule flexibility, conformational changes or variable intermolecular interactions, the exact interplay between these mechanisms is however poorly understood down to the molecular level. Here, we investigate the structural variations of a two-dimensional supramolecular network on Au(111) consisting of shape persistent polyphenylene molecules equipped with peripheral dodecyl chains. By comparing high-resolution scanning probe microscopy and molecular dynamics simulations obtained at 5 and 300 K, we determine the thermal expansion coefficient of the assembly of 980 ± 110 × 10−6 K−1, twice larger than other molecular systems hitherto reported in the literature, and two orders of magnitude larger than conventional materials. This giant positive expansion originates from the increased mobility of the dodecyl chains with temperature that determine the intermolecular interactions and the network spacing.

Hydrogen-Bonded Supramolecular Framework, Hirshfeld Surface Analysis and Interaction Energy Studies on 2-Amino-5-Chloropyridinium P-Toluenesulfonate

In title compound, 2-amino-5-chloropyridinium p-toluenesulfonate C7H7SO3− C5H5N2Cl+ (I), the anions and cations form an 22 (8) heteromeric dimer through N-H…O hydrogen bonds. 2-Amino-5-chloropyridinium cations and p-toluenesulfonate anions are interlinked through N-H…O and C-H…O hydrogen bonds to develop a two-dimensional supramolecular grid in the crystal structure parallel to the (0 0 1) plane. The formation of π…π and π…Cl interactions bridges the two-dimensional supramolecular network developing a three-dimensional packing of the crystal structure. The Hirshfeld surface analysis of the title molecule is carried out to understand various aspects of the intermolecular interaction. Interaction energies are calculated at the dispersion-corrected CE-B3LYP/6–31G(d,p) level of quantum theory for N-H…O, C-H…O, π…π interactions and the effect of interaction energies in the formation of a supramolecular network is studied.

Hydrogen-bonded supramolecular framework, Hirshfeld surface analysis and interaction energy studies on 2-amino-5-chloropyridinium p-toluenesulfonate

In title compound, 2-amino-5-chloropyridinium p-toluenesulfonate C7H7SOC5H5N2Cl+ (I), the anions and cations form an R22 (8) heteromeric dimer through N—H…O hydrogen bonds. 2-Amino-5-chloropyridinium cations and p-toluenesulfonate anions are interlinked through N—H…O and C—H…O hydrogen bonds to develop a two-dimensional supramolecular grid in the crystal structure parallel to the (0 0 1) plane. The formation of π…π and π…Cl inter­actions bridges the two-dimensional supramolecular network developing a three-dimensional packing of the crystal structure. The Hirshfeld surface analysis of the title molecule is carried out to understand various aspects of the intermolecular interaction. Interaction energies are calculated at the dispersion-corrected CE-B3LYP/6-31G(d,p) level of quantum theory for N—H…O, C—H…O, π…π interactions and the effect of interaction energies in the formation of a supramolecular network is studied.

Conversion of kinetically stable metal-organic product to thermodynamically stable one approved by thermal treatment and sonochemical reaction

A new nickel-based metal-organic compound [Ni(3-Clb)2.4H2O]n (1), (3-HClb = 3-chlorobenzoic acid), has been synthesized and structurally characterized by single crystal X-ray crystallography. One type of Ni(II) ion is present in 1 and two oxygen atoms from two 3-Clb‾ ligand and four oxygen atoms of four water molecules coordinate to each Ni(II) ion. Secondary hydrogen bonding interactions between primary structural building unit results in formation of two-dimensional supramolecular network. After thermal treatment of 1 at 130 °C, the coordinated water molecules were removed from 1 and compound [Ni(3-Clb)2]n (2) was formed. Irreversible desorption of water in this nickel coordination polymer were studied by IR spectroscopy, thermogravimetric and differential thermal analyses (TG-DTA), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). On the other hand, the sonochemical reactions between 3-HClb and Ni(NO3)2·6H2O in the presence of water resulted in formation of 2. Compound 1 is the kinetically stable product and compound 2 is the thermodynamically stable product. In addition to thermal treatment, ultrasonic irradiation also can provide the necessary activation energy for formation of thermodynamically stable product.