Supramolecular Framework Research Articles

Comprehensive structural characterization and Quantum mechanical exploration of o-phenylenediamine Dihydrogenphosphate: An integrated theoretical and experimental approach

Inorganic-organic hybrid materials merge the best of both inorganic and organic properties, enabling enhanced performance in diverse applications. The present study elucidates the crystallographic attributes of O-Phenylenediamine Dihydrogenphosphate (OPDP; C6H11N2O4P), crystallized in an ethanol medium. Characterized by a triclinic lattice, the asymmetric unit contains a single molecule (Z'=0), while the unit cell is comprised of eight molecules (Z = 2). The overall architecture is connected by intermolecular NH···O hydrogen bonds, which give rise to a bi-dimensional supramolecular framework. To substantiate the experimental findings and to probe the molecule's particular attributes, Fourier Transform Infrared Spectroscopy was deployed, owing to its sensitivity to inter/intra-molecular interactions within crystal systems. Density Functional Theory (DFT) calculations were performed using B3LYB functional, yielding molecular structure optimization, vibrational frequencies, and molecular properties such as Mulliken atomic charge distribution and frontier molecular orbital. Functional groups were discerned using FTIR spectroscopy and compared with theoretical predictions. The molecule features fourteen HH and three OH bonds. Natural Bond Analysis (NBO) was conducted to evaluate stabilization energy in donor–acceptor transitions. Surface morphology was examined using Scanning Electron Microscopy (SEM) in conjunction with Energy-Dispersive X-ray Spectroscopy (EDX). This comprehensive study advances our understanding of the unique structural and molecular properties of OPDP, demonstrating its potential for multifaceted applications.

Lysophosphatidic acid responsive photosensitive supramolecular organic frameworks for tumor imaging, drug loading, and photodynamic therapy

Supramolecular organic frameworks have been widely applied for biological detection and drug delivery. In this study, a supramolecular organic framework (SOF) is constructed through the self-assembly of a highly photosensitive triarylphosphine oxide guest molecule, OTPP-6-Methyl, with cucurbit [8] uril (CB [8]). The formation of the SOF gradually enhances the weak fluorescence of OTPP-6-Methyl owing to the restriction of the molecular folding motion. Although the high positive charge of OTPP-6-Methyl facilitates binding to various negatively charged substances, the SOF system only demonstrated an obvious fluorescence response to LPA, a biomarker of ovarian cancer, via the disassembly of SOF and subsequent binding of OTPP-6-Methyl with LPA. The fluorescence changes during the entire process are insufficient to allow the sensitive detection of LPA; thus, we further designed a FRET system by introducing Cy5, which can act as an energy receptor to achieve a ratiometric readout for LPA. The tumor-targeting cRGD group was introduced into the SOF system as part of another guest molecule, OTPP-5-M−1−cRGD, to improve the tumor-targeting ability of the SOF system. The SOF system further improves the photosensitivity of guest molecules, and is therefore used in the in vivo imaging of ovarian cancer subcutaneous tumors and as a DDS for loading DOX for the combined in vivo chemotherapy and photodynamic treatment of tumors.

Self-assembled Supramolecular Frameworks and Interaction Energy Studies of Acridine and Dihydroxynaphthalene based Cocrystals

Three cocrystals of acridine with 2,7-dihydroxynaphthalene (Ia and Ib) in two different polymorphs and 1,5-dihydroxynaphthalene (II) have been synthesized and characterized by single crystal x-ray diffraction method. Two polymorphs of acridine,2,7-dihydroxynaphthalene cocrystal crystallizes in same sapcegroup P-1 with different unit-cell parameters. In (Ia) the O‒H group form a syn-anti conformation whereas in (Ib) the O‒H group form an anti-anti conformation leads to the polymorphic structure of acridine, 2,7-dihydroxynaphthalene. This study reveals that the influence of π…π and C‒H…π interactions in the formation of one-, two-, and three-dimensional supramolecular frameworks when the classical hydrogen bonds such as O‒H…N and C‒H…O are limited to discrete motifs. The acridine molecules form continuous π…π stacking in the crystal structure of (Ia) and discrete π…π stacking in the crystal structure of (Ib) and (II). The conformational flexibility of the substituted hydroxy group has an influence in the supramolecular frameworks of the three-dimensional crystal structure. The intermolecular interaction energy calculation between the molecular pairs has been carried out to study the strength of the interaction and its dependence on the geometrical parameters.

Hydrogen-bonded supramolecular biohybrid frameworks for protein biomineralization constructed from natural phenolic building blocks.

Hydrogen bond-mediated supramolecular crystalline materials, such as hydrogen-bonded organic frameworks, offer a promising strategy for protein biomineralization, yet the intricate design and multi-step synthesis of specific orthogonal units in molecular building blocks pose a significant synthetic challenge. Identifying new classes of natural building blocks capable of facilitating supramolecular framework construction while enabling stable protein binding has remained an elusive goal. Here, we introduce a versatile assembly strategy enabling the organization of diverse proteins and phenolic building blocks into highly crystalline hydrogen-bonded supramolecular phenolic frameworks (ProteinX@SPF). The natural ellagic acid (EA) exhibits a centrosymmetric structure with catechol groups on each molecular side, facilitating hydrogen bonding with protein amino acid residues for primary nucleation. Subsequently, EA self-assembles into ProteinX@SPF through hydrogen bonding and π-π interactions. The multiple hydrogen-bonding interactions impart structural rigidity and directional integrity, conferring ProteinX@SPF biohybrids with remarkable resistance to harsh conditions while preserving protein bioactivity. Additionally, the supramolecular stacking induced by π-π interactions endows ProteinX@SPF with long-range ordered nanochannels, which can serve as the gating to sieve the catalytic substrate and thus enhance the biocatalytic specificity. This work sheds light on biomineralization with natural building blocks for functional biohybrids, showing enormous potential in biocatalysis, sensing, and nanomedicine.

Construction of a novel pyrene-based two-dimensional supramolecular organic framework and the selective regulation of reactive oxygen species for photocatalysis

We report herein a novel pyrene-based two-dimensional supramolecular organic framework (SOF) in water via host–guest interactions, which exhibits regulation of ROS and high photocatalytic efficiency.

"Gear-driven"-type chirality transfer of tetraphenylethene-based supramolecular organic frameworks for peptides in water.

Chirality transfer for natural chiral biomolecules can reveal the indispensable role of chiral structures in life and can be used to develop the chirality-sensing biomolecular recognition. Here, we report the synthesis and characterization of a series of achiral supramolecular organic frameworks (SOF-1, SOF-2, and SOF-3), constructed from cucurbit[8]uril (CB[8]) and tetraphenylethene (TPE) derivatives (1, 2, and 3), respectively, as chirality-sensing platforms to explore their chirality transfer mechanism for peptides in water. Given the right-handed (P) and left-handed (M) rotational conformation of TPE units and the selective binding of CB[8] to aromatic amino acids, these achiral SOFs can be selectively triggered in water by peptides containing N-terminal tryptophan (W) and phenylalanine (F) residues into their P- or M-rotational conformation, exhibiting significantly different circular dichroism (CD) spectra. Although various peptides have the same l-type chiral configuration, they can induce positive CD signals of SOF-1 and negative CD signals of SOF-2 and SOF-3, respectively. Based on the structural analysis of the linkage units between CB[8] and TPE units in these SOFs, a "gear-driven"-type chirality transfer mechanism has been proposed to visually illustrate the multiple-step chirality transfer process from the recognition site in the CB[8]'s cavity to TPE units. Furthermore, by utilizing the characteristic CD signals generated through the "gear-driven"-type chirality transfer, these SOFs can serve as chiroptical sensor arrays to effectively recognize and distinguish various peptides based on their distinctive CD spectra.

Tetraphenylethylene-based photoresponsive supramolecular organic framework and its metallization for photocatalytic redox reactions

A tetraphenylethylene-based supramolecular organic framework and its nickel-coordinated analogue were assembled, and both exhibited high efficiency in photocatalytic oxidation reactions.

Crystalline nanosheets of three-dimensional supramolecular frameworks with uniform thickness and high stability

A gas- and heat-yielding solidliquid chemical reaction, affords a 3D supramolecular framework with uniform thickness and Pt nano-crystals immobilized on the surface, exhibiting excellent photo-/thermo-catalytic CO oxidation performance.

Channel confinement and separation properties in an adaptive supramolecular framework using an adamantane tecton

A supramolecular framework with adaptive channels based on an adamantane tecton enables confinement and separation of small molecules and petrochemicals.

Development of a Ru-porphyrin-based supramolecular framework catalyst for styrene epoxidation.

A new microporous supramolecular-framework Ru(II)-porphyrin catalyst containing non-covalent interactions between pyrenylphenyl moieties at the meso-position of the porphyrin ring is synthesised and structurally characterised. This recyclable catalyst expedites styrene epoxidation more efficiently than homogeneous Ru-porphyrin catalytic systems.

Enantioselective assembly of tetrahedral Zr4(embonate)6 cages in zeolitic frameworks for synergetic circularly polarized luminescence

The chiral resolution of Zr4L6 cages has been achieved using enantiopure coordination cations, and an cage-supported SOD-type supramolecular zeolite framework was prepared, which demonstrates synergistic CPL output with glum values of 1.5 × 10−2.

CB[8]- and triarylboron-based supramolecular organic framework for microRNA detection, tumor-targeted drug delivery, and photodynamic therapy.

Supramolecular organic frameworks (SOFs) are widely used for biological detection and drug delivery. In this study, a SOF system was fabricated through the self-assembly of photosensitive triarylboron (TAB), TAB-6-methyl, and CB[8]. The maximum fluorescence emission of TAB-6-methyl was greatly enhanced and red-shifted from 560 nm to 610 nm after SOF formation. The SOF can specifically respond to a microRNA by dissembling and then combining with microRNA, which is accompanied by a fluorescence shift from 610 nm to 560 nm, thus providing a ratiometric readout for microRNA detection. The photosensitivity of TAB-6-methyl can be further improved by forming a SOF, which can be used in photodynamic therapy. By constructing another guest molecule, TAB-5-1-cRGD, we successfully embedded cRGD in the SOF system to improve its tumor-targeting ability. Moreover, we used this SOF system as a fluorescence imaging probe for targeted tumor imaging and as a drug carrier system for loading DOX to achieve combined photodynamic and chemotherapy treatment of tumors.

Nature of cyanoargentate bridges defining spin crossover in new 2D Hofmann clathrate analogues.

Chemical composition is leading among the numerous factors that determine the spin transition properties of coordination compounds. Classic dicyanometallic bridges {M(CN)2}- are commonly used to build Hofmann-like spin-crossover frameworks, but some extended bridges are also synthetically available. In this paper, we describe a successful synthesis of two very similar spin-crossover frameworks that differ in the cyanometallic bridges involved, namely [Fe(etpz)2{Ag(CN)2}2] (1) and {Fe(etpz)2[Ag2(CN)3][Ag(CN)2]} (2) (where etpz = 2-ethylpyrazine). Magnetic and Mössbauer studies demonstrated the occurrence of abrupt one-step high-spin (HS) ↔ low-spin (LS) transitions for both complexes. The spin transition temperatures are T1/2 ↓ = 233 K and T1/2 ↑ = 243 K for 1 and T1/2 ↓ = 188 K and T1/2 ↑ = 191 K for 2 with thermal hysteresis loops of 10 K for 1 and 3 K for 2. The bridging mononuclear [Ag(CN)2]- units and FeII cations assemble to form infinite 2D layers in the structure of 1. Interestingly, compound 2 forms 2D layers of FeII cations bridged by both binuclear [Ag2(CN)3]- and mononuclear [Ag(CN)2]- units. The structures of 1 and 2 comprise different types of intermolecular interactions including Ag⋯Ag and Ag⋯Netpz, which induce the creation of supramolecular 3D frameworks. The synergy between metallophilic interactions and the spin transition is also confirmed by the variation of Ag⋯Ag distances during spin crossover. The characterization of such analogues allowed us to analyze in detail the effect of the cyanometallic bridge on the structure of new frameworks and on the bistability in Hofmann-like complexes.

Drug-delivery and biological activity in colorectal cancer of a supramolecular porous material assembled from heptameric chromium-copper-adenine entities.

The therapeutic application of drugs often faces challenges due to non-specific distribution, inadequate dosification and degradation, which limits their efficacy. Two primary strategies are employed to overcome these issues: the use of derivatives of the active substances and incorporation of those into porous materials. The latter, involving materials such as zeolites, metal-organic frameworks (MOFs), and hydrogels, has shown promising results in protecting the active ingredients from degradation and enabling a controlled release. This study focuses on supramolecular metal-organic frameworks (SMOFs), which leverage supramolecular interactions for enhanced pore size control. [Cu6Cr(μ-adeninato-κN3:κN9)6(μ3-OH)6(μ-OH2)6](SO4)1.5·nH2O (Cu6Cr) was chosen for its flexible porous structure, water-stability, and paramagnetic properties. Magnetic sustentation studies showed that this compound was able to capture several drug molecules: 5-fluorouracil (5-FU), 5-aminosalicylic acid (5-ASA), 4-aminosalicylic acid (4-ASA) and theophylline (THEO). Their release follows a pseudo-first-order kinetics with desorption half-lives ranging from 2.2 to 4.7 hours. In this sense, a novel approach is proposed using bulkier raffinose and cholesterol as pore-blocking molecules. Cholesterol exhibited the best performance as a blocking molecule increasing the desorption half-life up to 8.2 hours. Cytotoxicity and RNA-seq transcriptomic assays carried out on human colorectal cancer cell cultures showed, on one hand, that the Cu6Cr porous material exhibits a proliferative effect, probably coming from the over-expression of MIR1248 and SUMO2 genes, and on the other hand, that there is a delay in the emergence of the cytotoxicity of 5-FU as expected for a slower release.

Synthesis of highly dispersed carbon-encapsulated Ru–FeNi nanocatalysts by a lignin–metal supramolecular framework strategy for durable water-splitting electrocatalysis

The construction strategy of designable metal–polyphenol coordination polymers has the potential to be generally applicable to produce a range of interesting metal/carbon composite catalysts.

Methoxylated Quinoline-Chalcones with Potential Pesticidal Activity: From Synthesis to Supramolecular Framework

In this work, the molecular properties of the (E)-3-(4-nitrobenzylidene)-2-(4-methoxyphenyl)- 2,3-dihydro-1-(phenylsulfonyl)-quinolin-4(1H)-one were studied, both in a solid and isolated state. The effect of changing the substituent groups –OCH3 and –Cl in the phenyl portion was verified, where the structural and electronic properties were compared. The density functional theory was employed using the hybrid exchange-correlation functional with long-range correction M06-2X, combined with the polarized and diffuse basis set 6-311++G(d,p), in the gas phase. The electronic structure was also analyzed by frontier molecular orbitals and molecular electrostatic potential maps, where information about its chemical reactivity was obtained. Also, the supramolecular arrangement was analyzed by Hirshfeld surface (HS), 2D fingerprint plots, and quantum theory of atoms in molecules (QTAIM). The natural bond orbitals (NBO) calculations were carried out to analyze the stability and hyperconjugation energy. Finally, molecular docking was carried out to investigate the affinities of the quinoline-chalcone with a bacterial protein (Agrobacterium pathogens) and an ecdysone receptor-potential pesticidal activity. The results encourage further in vitro and in vivo analyses of the two kinds of organisms investigated.

A square planar copper(II) complex noncovalently conjugated with a p-cresol for bioinspired catecholase activity

This work presents the synthesis of an unprecedented p-cresol-conjugated copper(II) complex as a p-cresol-coupled polydentate ligand, its crystal structure, and catecholase activity. X-ray crystallography reveals that the Cu(II) centre adopts a nearly planar coordination geometry. Crystal data for C14H13Cu0.5O3: Monoclinic, space group P21/c (no. 14), a = 5.9204(2) Å, b = 21.5615(10) Å, c = 9.0715(4) Å, β = 91.266(4)°, V = 1157.72(8) Å3, Z = 4, μ(MoKα) = 0.987 mm-1, Dcalc = 1.498 g/cm3, 12647 reflections measured (6.884° ≤ 2Θ ≤ 63.42°), 3233 unique (Rint = 0.0618, Rsigma = 0.0512) which were used in all calculations. The final R1 was 0.0710 (I > 2σ(I)) and wR2 was 0.2173 (all data). The crystallized p-cresol was localized in complex units through intermolecular O···H interactions and formed a 3D supramolecular framework employing short-ranged O···H and C-H···π interactions in the solid state. The copper(II) complex has been evaluated as a bioinspired catalyst in the oxidative transformation of 3,5-di-tert-butylcatechol (DTBC) to o-benzoquinone in acetonitrile with a high turnover number, 2.26´104 h–1. Electrochemical analysis of the copper(II) complex in the presence of DTBC recommends the generation of a catechol/o-benzosemiquinone redox couple during catalytic oxidation with the generation of hydrogen peroxide as a byproduct.

Study of supramolecular organic frameworks for purification of hydrogen through molecular dynamics simulations

The efficiency of proton exchange membrane fuel cells (PEMFCs) is heavily dependent on hydrogen purity. The production of hydrogen using methanol releases gases such as CO2 and CO, and hydrogen purification is particularly important. In this study, the performance of hydrogen purification (H2/CO2, H2/CO, and H2/CO2/CO) of three supramolecular organic frameworks (SOF-8, SOF-9a, and SOF-10a) with similar structures and different pore sizes and dimensions (two-dimensional (2D) and three-dimensional (3D)) were comprehensively investigated by molecular dynamics simulations and Grand Canonical Monte Carlo simulations. The monolayer, AA and AB stacked SOFs membranes were investigated. The results show that monolayer membranes exhibited high H2 permeability but low CO2 interception. AA-stacked SOF-10a and AB-stacked SOF-8 and SOF-10a can achieve 100 % separation of H2 from both CO2 and CO, with a minimum H2 permeability of 0.3 × 106 GPU and a maximum of up to 0.66 × 106 GPU in the H2/CO2 separation system, which is nearly 5 orders of magnitude higher than the industry standard. Microscopic analyses indicate that 3D SOFs (SOF-9a and SOF-10a) exhibit stronger interactions with CO2, while still maintain high H2 permeability in different stacking modes.

Superoxide radical generator based on triphenylamine-based supramolecular organic framework for green light photocatalysis

Supramolecular organic frameworks (SOFs) mostly require high-energy purple or blue light for photocatalytic reactions, while highly abundant and low-energy light systems have rarely been explored. Therefore, it is necessary to construct 2D SOFs for low-energy light-induced photocatalysis. This study describes the design and synthesis of a water-soluble two-dimensional (2D) supramolecular organic framework (TP-SOF) using the host–guest interaction between a triphenylamine derivative (TP-3Py) and cucurbit[8]uril (CB[8]). The formation of the 2D SOF can be attributed to the synergistic impact resulting from the orientated head-to-tail superposition mode between the vinylpyridine arms of TP-3Py and CB[8], which results in a significant redshift in the UV–vis absorption spectrum, especially displaying a strong absorption band in the green light region. The monomeric TP-3Py can effectively produce singlet oxygen (1O2) and realize the photocatalytic oxidation of thioanisole in the aqueous solution. In comparison to monomeric TP-3Py, the confinement effect of CB[8] results in a notable enhancement in the production efficiency of superoxide anion radicals (O2•−), exhibiting promising prospects in the field of photocatalytic oxidation reaction, which facilitates the application of TP-SOF as a very efficient photosensitizer for the promotion of the oxidative hydroxylation of arylboronic acids under green light in the aqueous solution, giving a high yield of 91%. The present study not only presents a compelling illustration of photocatalysis utilizing a 2D SOF derived from triphenylamine, but also unveils promising avenues for the photocatalytic oxidation of SOF employing low-energy light systems.

A novel guanidine-containing polyoxotantalate with reversible thermochromism property

A novel guanidine-containing polyoxotantalate (POTa), H12[CN3H6]12Na2(H2O)6[Cu(en)2(H2O)]3[Ta6O19]4·32H2O (1) has been synthesized by adding the CH6N3+ as counter cations. The [Ta6O19]8− clusters in compound 1 are connected by sodium ions to form a 2-D layered structure, which is further connected through [Cu(en)2(H2O)]2+ to form a 3-D supramolecular framework structure. Moreover, it is demonstrated that compound 1 exhibits reversible thermochromism behavior, changing from purple to dark blue upon heating and dehydration, which endows it with potential application in the field of anti-counterfeiting functional materials.