3D Supramolecular Assembly Research Articles

An insight into the non-covalent Cl•••Cl interaction in the solid state structure of carboxylate bridged trinuclear mixed valence cobalt(III/II/III) complexes with tetradentate N2O2 donor reduced Schiff base ligands

Two mixed-valence trinuclear cobalt(III)-cobalt(II)-cobalt(III) complexes, [CoII{(μ-L1)(μ-OOCC6H5NO2)CoIII(N3)}2] (1) and [CoII{(μ-L2)(μ-OOCC6H4NO2CH3)CoIII(N3}2] (2) have been synthesized using two tetradentate N2O2 donor 'reduced Schiff base' ligands, H2L1 {2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis(4-chlorophenol}, and H2L2{2-hydroxy-1,3-propanediyl)bis(iminomethylene)bis(4-chlorophenol}, and 3-nitrobenzoic benzoic acid or 4-methyl 3-nitrobenzoic benzoic acid as anionic co-ligands. The complexes have been characterized by spectroscopic measurements and their solid state structures have been determined by single crystal X-ray diffraction analysis. The trinuclear cobalt(III)-cobalt(II)-cobalt(III) skeleton of both the complexes are linear and centrosymmetric. Both the central cobalt(II) and terminal cobalt(III) of both the complexes are hexa-coordinated. DFT calculations have been used to analysed some supramolecular assemblies of the complex that have been observed in the solid state, specifically the Cl···Cl interactions that result in the creation of a stable 2D supramolecular assembly in the solid state. QTAIM and NCI Plot computational tools have been used to characterize the interactions. Thermo-gravimetric (TG) analysis was used to examine the thermal behaviour of both complexes. The redox behaviors of both the complexes were studied by using Cyclic Voltammetry (CV).

Structural elucidation and interpretation of 2D‒3D supramolecular assemblies featuring lone-pair···π interaction in two Cu(II)‒PDA complexes: Experimental and computational assessment

The structural study of two synthesized Cu-PDA (Cu = Copper(II), PDA = deprotonated Pyridine-2,6-dicarboxylic acid) complexes has been carried out using single-crystal X-ray diffraction where complex (1) [Cu(PDA)(H2O)2] exhibits one-dimensional (1D) and two-dimensional (2D) supramolecular assemblies and complex (2) [Cu(PDA)(H2PDA)]·H2O exhibits 1D, 2D, and 3D (three-dimensional) supramolecular networks in their solid-state structure with the aid of intermolecular noncovalent interactions. Lone pair···π/π···lone pair networks are exclusively found in both complex (1) and (2). The intermolecular interactions are characterized through Hirshfeld surface analysis and quantified by 2D fingerprint plot. The noncovalent interactions are further characterized by Bader's theory of ‘Atoms in Molecules’ (AIM) and ‘noncovalent interaction’ (NCI) plot and the topological parameters at bond critical points (BCPs) have been evaluated. Therefore, the energetic factors to the stabilization of the crystal structure observed experimentally have been obtained by the computational calculations.

Altering the structures of 3D supramolecular assemblies from melamine and cyanuric acid derivatives in water.

Herein, we obtained two supramolecular assemblies with layered structures from melamine, N-methylmelamine, and hexynyl-cyanuric acid in water. By combination of X-ray diffraction, electron microscopy, and molecular dynamics studies, we found that introducing one methyl group in melamine alters the arrangement of the layers in these structures.

Crystal structures and syntheses of four novel Cu(I)-MOFs with in-situ reduced of Cu(II) and highly efficient fluorescent sensor for trace nitroaromatics

Four novel Cu(I)-based metal-organic frameworks, [Cu3(p-IPIB)(CN)Cl2]n (Cu(I)-MOF-7), [Cu3(p-IPIB)(CN)Cl2]n (Cu(I)-MOF-8), [Cu3(p-IPIB)Cl3]n (Cu(I)-MOF-9) and [Cu2(p-IPIB-Cl)1/2Cl2(H2O)]n (Cu(I)-MOF-10) where ligand p-IPIB is 1,4-bis[(2-(4-(1H-imidazol -1-yl)-phenyl)-1H-imidazole-1-yl)-methyl]-benzene, have been successfully synthesized by in-situ reduction of Cu(II) under solvothermal reaction condition. Single X-ray diffraction analysis shown that Cu(I)-MOF-7 and 8 are not only structural supramolecular isomerism containing cyano-bridge which was in situ obtained from the cleavage of the CCN bond of acetonitrile solvent, but also a 3D twofold interpenetration metallo-supramolecular assembly for Cu(I)-MOF-7 and a 3D porous supramolecular assembly containing the macrometallacyclic box structure for Cu(I)-MOF-8, respectively. Cu(I)-MOF-9 is a 1D channel polymeric chain motif with macrometallacyclic structure containing [Cu3Cl3] cluster of μ3- and μ2-chloride bridge. And Cu(I)-MOF-10 is also a 3D twofold interpenetration metallo-supramolecular assembly with [Cu4Cl3(H2O)2] cluster of μ4-chloride bridge. They are thermally stable and exhibit apparent porous properties with adsorption of N2 and CO2 gas. The fluorescence sensing experiment indicated that Cu(I)-MOF 7–10 can be used for detecting nitroaromatic explosives through fluorescence quenching in the solution and they have the best sensing effects on the detection of 2,4,6-Trinitrophenol (TNP). Especially, Cu(I)-MOF-9 has the best sensing property towards TNP with a higher quenching constant of 4.53 × 104 L/mol and a lower detection limit of 1.21 ppm.

Halogen Bond-Involving Self-Assembly of Iodonium Carboxylates: Adding a Dimension to Supramolecular Architecture.

We designed 0D, 1D, and 2D supramolecular assemblies made of diaryliodonium salts (functioning as double σ-hole donors) and carboxylates (as σ-hole acceptors). The association was based on two charge-supported halogen bonds (XB), which occurred between IIII sites of the iodonium cations and the carboxylate anions. The sequential introduction of the carboxylic groups in the aryl ring of the benzoic acid added a dimension to the 0D supramolecular organization of the benzoate, which furnished 1D-chained and 2D-layered structures when terephthalate and trimesate anions, correspondingly, were applied as XB acceptors. The structure-directing XB were studied using DFT calculations under periodic boundary conditions and were followed by the one-electron-potential analysis and the Bader atoms-in-molecules topological analysis of electron density. These theoretical methods confirmed the existence of the XB and verified the philicities of the interaction partners in the designed solid-state structures.

2D coordination polymers based on the interaction between cucurbit[5]uril and light lanthanide metal ions in the presence of copper salts, and use for the detection of nitrogenous bases

The coordination of cucurbit[5]uril (Q[5]) with lanthanide cations (Ln3+), in the presence of Cu2+ cations, led to the formation of 2D-network coordination polymers, which have been investigated using single crystal X-ray diffraction. Experimental results revealed that crystals were only readily affordable for the systems involving the lighter lanthanide cations (La3+, Ce3+, Pr3+, Sm3+, Eu3+ and Tb3+), with all six Ln3+- Q[5] complexes (1 ∼ 6) exhibiting similar coordination mode at the cucurbit[5]uril (Q[5]), and forming 2D-network coordination polymers with a 2D supramolecular assembly. One complex was found to detect Adenine (A) and Uracil (U) with high selectively.

Novel Insight into the Photophysical Properties and 2D Supramolecular Organization of Poly(3,4-ethylenedioxythiophene)/Permodified Cyclodextrins Polyrotaxanes at the Air-Water Interface.

Two poly(3,4-ethylenedioxythiophene) polyrotaxanes (PEDOT∙TMe-βCD and PEDOT∙TMe-γCD) end-capped by pyrene (Py) were synthesized by oxidative polymerization of EDOT encapsulated into TMe-βCD or TMe-γCD cavities with iron (III) chloride (FeCl3) in water and chemically characterized. The effect of TMe-βCD or TMe-γCD encapsulation of PEDOT backbones on the molecular weight, thermal stability, and solubility were investigated in depth. UV-vis absorption, fluorescence (FL), phosphorescence (PH), quantum efficiencies, and lifetimes in water and acetonitrile were also explored, together with their surface morphology and electrical properties. Furthermore, dynamic light scattering was used to study the hydrodynamic diameter (DH) and z-potential (ZP-ζ) of the water soluble fractions of PEDOT∙TMe-βCD and PEDOT∙TMe-γCD. PEDOT∙TMe-βCD and PEDOT∙TMe-γCD exhibited a sharp monodisperse peak with a DH of 55 ± 15 nm and 122 ± 32 nm, respectively. The ZP-ζ value decreased from -31.23 mV for PEDOT∙TMe-βCD to -20.38 mV for PEDOT∙TMe-γCD, indicating that a negatively charged layer covers their surfaces. Surface pressure-area isotherms and Brewster angle microscopy (BAM) studies revealed the capability of the investigated compounds to organize into sizeable and homogeneous 2D supramolecular assemblies at the air-water interface. The control of the 2D monolayer organization through the thermodynamic parameters of PEDOT∙TMe-βCD and PEDOT∙TMe-γCD suggests potential for a wide range of optoelectronic applications.

Alanine‐Induced Alteration of Organogelation Properties of Phenylalanine‐Based Shortest Peptide Sequence

AbstractShort peptide based Low‐molecular‐weight‐organogelators (LMWGs), or supramolecular gels have recently gained large attention due to their enormous application in several biophysical and biochemical contexts. Out of the 20 naturally occurring amino acids Phenylalanine (Phe) acts as a good organogelators. Biophysical parameters like heat, pH, and solvent polarity, along with light, ultrasound, ions, can affect in alteration of supramolecular self‐aggregation at the molecular level in moderate length of peptide sequences; however, we focused here on how the conformational characteristics and supramolecular assemblages of the excellent LMWG Phe would be influenced by its substitution with similar hydrophobic amino acids (e.g Ala) in the same organic solvent even in the shortest two residue sequence. Using different microscopic and biophysical techniques, it is observed that the supreme capability of Phe residue as LMWG in the formation of supramolecular self‐aggregation in Hex‐Phe(1)‐Phe(2)‐OMe (FF) in organic solvents has been completely altered from fibrillary dendrimeric network to the crystalline phase by substitution with Ala at the C‐terminal [Hex‐Phe(1)‐Ala(2)‐OMe](FA) in a simple two residue sequence. This demonstrates unequivocally how a little change in the peptide side chain has the unique ability to form a distinct 3D supramolecular assembly and establishes the context‐dependent supramolecular morphology of the peptide‐based LMWG.

A Paradigm Shift from 2D to 3D: Surface Supramolecular Assemblies and Their Electronic Properties Explored by Scanning Tunneling Microscopy and Spectroscopy.

Exploring supramolecular architectures at surfaces plays an increasingly important role in contemporary science, especially for molecular electronics. A paradigm of research interest in this context is shifting from 2D to 3D that is expanding from monolayer, bilayers, to multilayers. Taking advantage of its high-resolution insight into monolayers and a few layers, scanning tunneling microscopy/spectroscopy (STM/STS) turns out a powerful tool for analyzing such thin films on a solid surface. This review summarizes the representative efforts of STM/STS studies of layered supramolecular assemblies and their unique electronic properties, especially at the liquid-solid interface. The superiority of the 3D molecular networks at surfaces is elucidated and an outlook on the challenges that still lie ahead is provided. This review not only highlights the profound progress in 3D supramolecular assemblies but also provides researchers with unusual concepts to design surface supramolecular structures with increasing complexity and desired functionality.

Nearly-freestanding supramolecular assembly with tunable structural properties

The synthesis and design of two-dimensional supramolecular assemblies with specific functionalities is one of the principal goals of the emerging field of molecule-based electronics, which is relevant for many technological applications. Although a large number of molecular assemblies have been already investigated, engineering uniform and highly ordered two-dimensional molecular assemblies is still a challenge. Here we report on a novel approach to prepare wide highly crystalline molecular assemblies with tunable structural properties. We make use of the high-reactivity of the carboxylic acid functional moiety and of the predictable structural features of non-polar alkane chains to synthesize 2D supramolecular assemblies of 4-(decyloxy)benzoic acid (4DBA;C_{17}H_{26}O_{3}) on a Au(111) surface. By means of scanning tunneling microscopy, density functional theory calculations and photoemission spectroscopy, we demonstrate that these molecules form a self-limited highly ordered and defect-free two-dimensional single-layer film of micrometer-size, which exhibits a nearly-freestanding character. We prove that by changing the length of the alkoxy chain it is possible to modify in a controlled way the molecular density of the “floating” overlayer without affecting the molecular assembly. This system is especially suitable for engineering molecular assemblies because it represents one of the few 2D molecular arrays with specific functionality where the structural properties can be tuned in a controlled way, while preserving the molecular pattern.

Controllable 1D, 2D and 3D supramolecular assemblies of Ir(iii) complexes

Size-controllable supramolecular assemblies of 1D nanofibers, 2D nanosheets and 3D nanoblocks were successfully constructed via seeded self-assembly of Ir(iii) complexes.

3D supramolecular assembly of Cu(II) CP containing 1D zig-zag chain and 2D paddle-wheel net: Structural elucidation and investigation of band gap

A new Cu(II) based coordination polymer (CP) [Cu3(ipa)3(4-clpy)(H2O)2][Cu(ipa)(4-clpy)2(CH3OH)]·3CH3OH (1); (H2ipa = isophthalic acid or benzene-1,3-dicarboxylic acid and 4-clpy = 4-chloropyridine) has been synthesized by slow diffusion method in a single pot technique. Single crystal X-ray analysis reveals that compound 1 consists of both one-dimensional (1D) zig-zag chain and two-dimensional (2D) paddle-wheel net, resulting the formation of a three-dimensional (3D) supramolecular architecture via extensive hydrogen bonding, π⋯π stacking and halogen⋯π interactions. The strength of non-covalent interactions in compound 1 has been investigated by Hirshfeld surface analysis. The semiconducting nature of compound 1 was also explored by HOMO-LUMO band-gap calculation using density functional theory (DFT) computation.

Morphologically Tunable Supramolecular Rectangular Microsheet and Microsaw Constructed by Hierarchical Self-Assembly Based on Hydrogen Bonds.

An amino acid derivative, thiophene (TDAV),as new building blocks for 2D supramolecular assembly is designed. Various square and rectangular microsheets are achieved and the aspect ratios are precisely regulated by controlling the polarity of cosolvent or water content. By the introduction of chirality, the novel microsaw is also achieved. It provides a new approach to prepare various kinds of unique supramolecular 2D materials with controllable shapes and sizes for future biological applications.

Successive Deprotonation Steering the Structural Evolution of Supramolecular Assemblies on Ag(111).

In this study, we demonstrate the structural evolution of a two-dimensional (2D) supramolecular assembly system, which is steered by the thermally activated deprotonation of the primary organic building blocks on a Ag(111) surface. Scanning tunneling microscopy revealed that a variety of structures, featuring distinct structural, chiral, and intermolecular bonding characters, emerged with the gradual thermal treatments. According to our structural analysis, in combination with density function theory calculations, the structural evolution can be attributed to the successive deprotonation of the organic building blocks due to the inductive effect. Our finding offers a facile strategy towards controlling the supramolecular assembly pathways and provides a comprehensive understanding of the 2D crystal engineering on surfaces.

Structural, spectral, cytotoxic and biocatalytic studies of a dinuclear phenoxo bridged Zn(II) complex from NNO donor tridentate Schiff base

• A zinc(II) complex derived from an NNO donor Schiff base system is discussed. • Complex is a centrosymmetric dinuclear phenoxo bridged compound. • Type I halogen interaction present in the crystal system is investigated. • Complex exhibits in vitro cytotoxicity against Dalton's lymphoma ascites cell lines. • Complex shows catecholase like activity in DMF medium. A zinc(II) complex of an NNO donor tridentate Schiff base, 4‑chloro-2-(((3-(methylamino)propyl)imino)methyl)phenol (HL) was synthesised and characterized by different physicochemical methods including single crystal XRD, elemental analysis, IR and electronic spectral analysis. Zinc(II) complex is a centrosymmetric dinuclear phenoxo bridged compound which crystallized in triclinic P 1 ¯ space group. There are a large number of intermolecular hydrogen bonding interactions present in the crystal system which give rise to the formation of a 2D supramolecular assembly and the visual analysis of those intermolecular interactions was done by Hirshfeld surface analysis. Type I halogen interactions, which are quite uncommon, are also discussed based on angular preference, intermolecular distance, and the size of the Cl atom. Complex exhibited negative solvatochromism. Luminescent properties were investigated and quenching of fluorescence was observed which is supported by the quantum yield values. Cytotoxic activity of the complex has been screened in vitro against lymphoma ascites cell lines. In addition, catecholase activity of the complex has been investigated in DMF medium and found that complex was able to catalyze the aerobic oxidation of 3,5-di‑ tert -butylcatechol (3,5-DTBC) to the corresponding quinone.

Effect of a lone electron pair and tetrel interactions on the structure of Pb(II) CPs constructed from pyrimidine carboxylates and auxiliary inorganic ions

Three new Pb(II) coordination polymers (CPs) of pyrimidine-2-carboxylate ligand and different anionic co-ligands (perchlorate, chloride and nitrate) were synthesized and characterized by physicochemical (CHN, FT-IR, TG) and structural (SC-XRD) methods. Considering only strong primary coordination bonds the Pb(II) centres in all three complexes are hemidirectionally coordinated by organic ligands due to stereochemical activity of a lone electron pair. The Pb nodes and ligand linkers formed single- or double-layered 2D networks with honeycomb-like topology. The primary coordination sphere is sterically suitable for establishing the interactions at longer distances, where Pb centre act as Lewis acid. The MEP calculations confirmed the presence of a σ-hole in the proximity of Pb centres. Thus, all the Pb centres participate in Pb···O or Pb···Cl tetrel interactions with auxiliary inorganic ions, which together with secondary interactions of ligands and water molecules extended the structures into 3D supramolecular assemblies. The QTAIM calculations allowed for estimation of the energy of primary and secondary/tetrel interactions and to propose the theoretical criteria based on the |VBCP|/GBCP, HBCP/ρBCP, and DI parameters for distinguishing among interactions.

3d Supramolecular Assembly of Cu(Ii) Cp Containing 1d Zig-Zag Chain and 2d Paddle-Wheel Net: Crystal Structure Determination and Band Gap Study

3d Supramolecular Assembly of Cu(Ii) Cp Containing 1d Zig-Zag Chain and 2d Paddle-Wheel Net: Crystal Structure Determination and Band Gap Study

A 3D supramolecular assembly based on a {AsW12} cluster and in-situ ligand modified metal-organic complexes for photocatalytic properties and electrocatalytic sensing for detection of hydrogen peroxide

A Keggin-type arsenotungstate supramolecular assembly modified with metal-organic complexes, {Zn(dpb)2}2{AsWVI11WV O40}·4H2O (1) (dpb ​= ​2,6-di(2-pyridine)-4,4′-bipyridine), have been synthesized under hydrothermal condition and fully characterized by routine method. In compound 1, each {AsW12O40} cluster is attached to eight Zn(dpb)2 complexes, which are further attracted by four Keggin analogues, forming a tightly packed three-dimensional supramolecular network through strong H-bonds and π-π interactions. It is worth noting that the dpb ligand in the complex {Zn(dpb)2} is produced from the ptz and dpp precursor via under hydrothermal conditions for the first time and its possible assembly path is discussed. The stacking pattern of compound 1 can be simplified to 4,8-connected network with topology {410·610·88}{45·6}2. Compound 1 modified glassy carbon electrode (1-GCE) exhibits significant electrocatalytic reduction activity and outstanding sensing performance for H2O2 with low detection limit (0.43 ​μM) and wide linear range (1.28 μM-2.23 ​mM). Meanwhile, it has high efficiency photocatalytic degradation performance for refractory dyes under ultraviolet irradiation.

Synthesis, Photophysics, and Langmuir Films of Polyfluorene/Permodified Cyclodextrin Polyrotaxanes.

In the present study, we investigated the effect of permodified 2,3,6-tri-O-trimethylsilyl β- and γ-cyclodextrin (TMS·β-CD, TMS·γ-CD) encapsulation on the optical, electrochemical, morphological, and supramolecular arrangements of a poly[2,7'-(9,9-dioctylfluorene-alt-2',7-fluorene)] PF copolymer. For this purpose, the photophysical properties and Langmuir monolayer formation of PF·TMS·β-CD and PF·TMS·γ-CD polyrotaxanes were investigated and compared with those of the reference PF. Surface pressure-area isotherms and Brewster angle microscopy studies indicated the capability of both polyrotaxanes to organize into larger and homogeneous 2D supramolecular assemblies at the air-water interface. The obtained results suggest that the presence of the surrounding TMS·β-CD and TMS·γ-CD macrocycles on the PF backbones leads to changes in the conformation and hydrophobicity of the film surfaces. Our investigation offers a method to assess the impact of TMS-CD encapsulation on the control of 2D monolayer formation, with particular attention on the generation of stable PF monolayers for organic electronic devices.

Facile Synthesis, Spectral and Electrochemical Properties and Catalytic Efficiencies of β-Octabromo Vanadyl Porphyrin

Selective oxidation of olefins to epoxy compounds has always been an interesting area of research for chemists owing to their great importance in the production of highly valued commodity chemicals such as polyurethanes, unsaturated resins, glycols, surfactants, and other products. Further, oxidative bromination of thymol and other phenolic derivatives has industrial importance. Iron and manganese porphyrins have been widely utilized as effective homogeneous catalysts for such oxygenation reactions in the last few decades. The major drawbacks of homogeneous MTPP-based catalysts are the macrocyclic ring which is liable to oxidative self-destruction, aggregation of metalloporphyrins through π–π interactions, lower turnover frequency (TOF) and poor product selectivity. Notably, vanadyl porphyrins have gained significant interest as useful molecules with applications in the fields of therapeutics, catalysis and 3D supramolecular assemblies. Herein, we synthesized vanadyl complex of β-octabromo-meso-tetraphenylporphyrin (VOTPPBr8) by self-catalytic reaction of VOTPP in excellent yield ar room temperature under mild bromination conditions using KBr/H2O2 in presence of HClO4. Further, VOTPPBr8 was utilized as an efficient catalyst for the epoxidation and oxidative bromination reactions. In this presentation, we will present facile synthesis, spectral and electrochemical properties and catalytic efficiencies of VOTPP and VOTPPBr8 in detail.