Supramolecular Metal Research Articles

Self‐Induced Radioluminescence in Supramolecular Metal Halide Doped with Radioactive Isotope Strontium‐90

AbstractMetal halides have recently garnered significant attention in developing functional materials, predominantly utilizing elements with stable isotopes as chemical components. However, the exploration of metal halides containing radioisotopes remains in its infancy, and their potential functionalities are not yet well understood. Herein, the synthesis and characterization of the first radionuclide‐doped supramolecular metal halide that displays unprecedented self‐induced radioluminescence are reported. The complex of 90Sr@[Sr2(18‐crown‐6 ether)2(H2O)2Cl2)]SbCl5, designated 90Sr‐(18C6@Sr)SbCl5, is synthesized by assembling both stable Sr2+ ions and millicurie‐level radioactive 90Sr2+ ion, co‐crystallized with SbCl52− anions. The inherent beta decays (β− particles) of 90Sr2+ ions from cationic supramolecular scaffoldings continuously ionize the SbCl52− anions, enabling self‐induced radioluminescence. Monte Carlo calculations reveal that ionization and bremsstrahlung processes predominantly generate secondary electrons, contributing to self‐induced radioluminescence. The self‐induced radioluminescence intensity of 90Sr‐(18C6@Sr)SbCl5 is measured to be 5.06 × 1012 counts•s−1•g−1•Ci−1, ≈18 times greater than that of the benchmark Th(NO3)4•5H2O compound. This discovery sheds light on the development of a new class of radioactive decay energy‐converting materials based on organo‐metal halides.

Emergence of Exotic Spin Texture in Supramolecular Metal Complexes on a 2D Superconductor.

Designer heterostructures have offered a very powerful strategy to create exotic superconducting states by combining magnetism and superconductivity. In this Letter, we use a heterostructure platform combining supramolecular metal complexes (SMCs) with a quasi-2D van der Waals superconductor NbSe_{2}. Our scanning tunneling microscopy measurements demonstrate the emergence of Yu-Shiba-Rusinov bands arising from the interaction between the SMC magnetism and the NbSe_{2} superconductivity. Using x-ray absorption spectroscopy and x-ray magnetic circular dichroism measurements, we show the presence of antiferromagnetic coupling between the SMC units. These result in the emergence of an unconventional 3×3 reconstruction in the magnetic ground state that is directly reflected in real space modulation of the Yu-Shiba-Rusinov bands. The combination of flexible molecular building blocks, frustrated magnetic textures, and superconductivity in heterostructures establishes a fertile starting point to fabricating tunable quantum materials, including unconventional superconductors and quantum spin liquids.

Bending, Twisting, and Propulsion of Photoreactive Crystals by Controlled Gas Release

AbstractThe rapid release of gas by a chemical reaction to generate momentum is one of the most fundamental ways to elicit motion that could be used to sustain and control the motility of objects. We report that hollow crystals of a three‐dimensional supramolecular metal complex that releases gas by photolysis can propel themselves or other objects and advance in space when suspended in mother solution. In needle‐like regular crystals, the reaction occurs mainly on the surface and results in the formation of cracks that evolve due to internal pressure; the expansion on the cracked surface of the crystal results in bending, twisting, or coiling of the crystal. In hollow crystals, gas accumulates inside their cavities and emanates preferentially from the recess at the crystal terminus, propelling the crystals to undergo directional photomechanical motion through the mother solution. The motility of the object which can be controlled externally to perform work delineates the concept of “crystal microbots”, realized by photoreactive organic crystals capable of prolonged directional motion for actuation or delivery. Within the prospects, we envisage the development of a plethora of light‐weight, efficient, autonomously operating robots based on organic crystals with high work capacity where motion over large distances can be attained due to the large volume of latent gas generated from a small volume of the crystalline solid.

Bending, Twisting, and Propulsion of Photoreactive Crystals by Controlled Gas Release.

The rapid release of gas by a chemical reaction to generate momentum is one of the most fundamental ways to elicit motion that could be used to sustain and control the motility of objects. We report that hollow crystals of a three-dimensional supramolecular metal complex that releases gas by photolysis can propel themselves or other objects and advance in space when suspended in mother solution. In needle-like regular crystals, the reaction occurs mainly on the surface and results in the formation of cracks that evolve due to internal pressure; the expansion on the cracked surface of the crystal results in bending, twisting, or coiling of the crystal. In hollow crystals, gas accumulates inside their cavities and emanates preferentially from the recess at the crystal terminus, propelling the crystals to undergo directional photomechanical motion through the mother solution. The motility of the object which can be controlled externally to perform work delineates the concept of "crystal microbots", realized by photoreactive organic crystals capable of prolonged directional motion for actuation or delivery. Within the prospects, we envisage the development of a plethora of light-weight, efficient, autonomously operating robots based on organic crystals with high work capacity where motion over large distances can be attained due to the large volume of latent gas generated from a small volume of the crystalline solid.

Tracing the genealogy of research on the mechanism of blue flower coloration by anthocyanin based on Keita Shibata's work.

K. Shibata is the ancestor of the research on anthocyanins in Japan and proposed metal complex theory against the pH theory by R. Willstätter. Shibata's successors, S. Hattori and K. Hayashi, made efforts to clarify blue flower coloration by metal complexation and found commelinin, a self-assembled supramolecular metal complex pigment, in blue dayflower, Tsuyukusa. The author introduces two key reports on blue flower coloration published in the Proceedings of the Japan Academy and describes the subsequent development of the study.

Platelet Membrane-Enclosed Bioorthogonal Catalysis for Combating Dental Caries.

Platelets have shown promise as a means to combat bacterial infections, fostering the development of innovative therapeutic approaches. However, several challenges persist, including cargo loading issues, limited efficacy against biofilms, and concerns regarding the impact of payloads on the platelet carriers. Here, human platelet membrane vesicles (h-PMVs) encapsulating supramolecular metal catalysts (SMCs) as "nanofactories" to convert prodrugs into antimicrobial compounds within close proximity to bacteria are introduced. Having established the feasibility and effectiveness of the SMCs within h-PMVs, referred to as the PLT-reactor, to activate pro-antibiotic drugs (pro-ciprofloxacin and pro-moxifloxacin) using model organisms (Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923), the investigation is subsequently extended to oral biofilms, with a particular emphasis on Streptococcus mutans 3065. This "bind and kill" strategy demonstrates the potent antimicrobial specificity of the PLT-reactor through localized antibiotic production. h-PMVs play a pivotal role by enabling precise targeting of pathogenic biofilms on natural teeth while minimizing potential hemolytic effects. The finding indicates that platelet membrane-cloaked surfaces exhibit robust, multifaceted, and pathogen-specific binding affinity with excellent biocompatibility, making them a promising alternative to antibody-based therapies for infectious diseases.

Crystal structure and photocatalytic activity of luminescent 3D-Supramolecular metal organic framework of dysprosium

A 3D supramolecular metal organic framework of dysprosium has been fabricated through a facile hydrothermal procedure with the ligand, 2,6-naphthalene disulphonic acid and the co-ligand, 4,4′-bipyridine. The MOF has been characterized as [C60H81DyN8O30S4] by routine analytical procedures. SXRD studies of the MOF show the existence of a hydrogen-bonded 3D supramolecular structure with high porosity. It crystallizes in monoclinic space group P21/n with unit cell parameters, a = 16.5424(6) Å, b = 37.0052(14) Å, c = 24.4361(9) Å, β = 100.7410°, α = γ = 90°. The Dy-MOF has eight coordinated water molecules around the metal centre and exhibits square anti-prismatic geometry. The band gap is 3.11 eV. The degradation experiments under visible light confirmed that Dy-MOF can act as a photocatalyst. Addition of hydrogen peroxide remarkably increases the degradation efficiency of the MOF through an advanced oxidation process. The newly synthesized MOF produced sharp emission peaks characteristic of dysprosium ion.

Visualization of domain structure and piezoelectric energy harvesting in a ferroelectric metal-ligand cage.

The ferroelectric behaviour of an octahedral cage [[Ni6(H2O)12(TPTA)8]·(NO3)12·36H2O] (1) exhibiting high remnant polarization of 25.31 μC cm-2 is discovered. For the first time, clear domain structures and the characteristic electromechanical responses are demonstrated using piezoresponsive force microscopy for a thin film of 1. Owing to its mechanical energy conversion capability, polymer composites of 1 were employed as efficient piezoelectric nanogenerators.

Correction: An in solution adsorption characterization technique based on the response to an external magnetic field of porous paramagnetic materials: application on supramolecular metal–adenine frameworks containing heterometallic heptameric clusters

Correction for ‘An in solution adsorption characterization technique based on the response to an external magnetic field of porous paramagnetic materials: application on supramolecular metal–adenine frameworks containing heterometallic heptameric clusters’ by Jon Pascual-Colino et al., Inorg. Chem. Front., 2023, https://doi.org/10.1039/d2qi01994a.

An in solution adsorption characterization technique based on the response to an external magnetic field of porous paramagnetic materials: application on supramolecular metal–adenine frameworks containing heterometallic heptameric clusters

Magnetic sustentation experiments are employed to monitor the adsorption process of a supramolecularly assembled MOF in solution.

Synthesis, crystal structure, DFT calculations, Hirshfeld surface analysis and molecular docking studies of a new manganese complex

• Metal complexes with Schiff base ligands are interesting for biological and pharmacological applications. • A new manganese complex ( 3 ) has been synthesized and characterized. • Interesting hydrogen-bonding supramolecular synthons are present in ( 3 ) • Intermolecular electrostatic interactions play a crucial role in building supramolecular metal complexes. • Complementary experimental and theoretical methods are used for the study of (3) • Schiff base of (3) has an interesting biological activity. Mn II -based coordination compound [Mn II (L) 2 (NO 3 )(H 2 O) 3 ]NO 3 (3) has been synthesized with Shiff’s base N 2 -benzylidenyl isonicotinic acid hydrazide (2) and (Mn(NO 3 ) 2 ⋅4H 2 O). The compound is new and has been fully characterized by FT-IR, UV-visible, 1H and 13 C NMR spectroscopic techniques and single-crystal X-ray diffraction complemented with a quantum chemical study performed with DFT method. The compound crystallized in the monoclinic centrosymmetric P2 1 /n space group. The crystal structure of (3) exhibits a nitrate anion and a non-centrosymmetric complex cation [Mn II (L) 2 (NO 3 )(H 2 O) 3 ] + . In the molecular packing, the different entities are held together through intermolecular strong, weak and non-conventional O/N/C–H ···O hydrogen bonds, that found to be effective in stabilizing the three-dimensional network. Furthermore, the crystal structure of ( 3 ) contains interesting cyclic supramolecular homo and heterosynthons. Moreover, π–π stacking and N lone-pair …C–H intermolecular electrostatic interactions play a crucial role in building a supramolecular layered network. To better understand the contribution of different intermolecular interactions to the supramolecular assembly, Hirshfeld surface analysis was performed. The obtained results indicate that the main contributions are attributed to O—H···O, N—H···O and C—H···O interactions which are the primary giver the stabilisation in the crystal. The theoretical achievements were found in a good relation with the experimental structural analysis. The HOMO and LUMO energies and molecular electrostatic potential surface were derived from the same basis and the natural population Mulliken charge distribution analysis showed the different electron donors which coordinate with manganese. In addition to that, the molecular docking for (2) and (3) investigation with the 2X22 enzyme involved in Mycobacterium tuberculosis H37Rv have been conducted in order to check the biological activity of the Schiff base and its complex.

Metal–Organic Cages: Applications in Organic Reactions

Supramolecular metal–organic cages, a class of molecular containers formed via coordination-driven self-assembly, have attracted sustained attention for their applications in catalysis, due to their structural aesthetics and unique properties. Their inherent confined cavity is considered to be analogous to the binding pocket of enzymes, and the facile tunability of building blocks offers a diverse platform for enzyme mimics to promote organic reactions. This minireview covers the recent progress of supramolecular metal–organic coordination cages for boosting organic reactions as reaction vessels or catalysts. The developments in the utilizations of the metal–organic cages for accelerating the organic reactions, improving the selectivity of the reactions are summarized. In addition, recent developments and successes in tandem or cascade reactions promoted by supramolecular metal–organic cages are discussed.

Crystal structure elucidation, Hirshfeld surface analysis, lattice energy frame work, and molecular docking studies of copper(II) complex of 1-(3-bromo-5-chloro-2-hydroxyphenyl)ethan-1-one in the presence of solvent pyridine as secondary ligand

Copper(II) complex of 1-(3-bromo-5-chloro-2-hydroxyphenyl)ethan-1-one has been synthesized and crystallized in solvent pyridine as secondary ligand with monoclinic space group P21/n with set of lattice parameters as a = 14.060(3) Å, b = 12.187(2) Å, c = 15.153(3) Å and β = 91.162(4)° having Z = 4. Molecular geometry around metal is distorted octahedral, and all four oxygen of bidentate ligand co-ordinate to metal forming a square planer configuration along with one nitrogen of each solvent molecule pyridine to complete the octahedral sphere. Crystal packing is governed by various intra–inter molecular, π⋅⋅⋅π, and C-H⋅⋅⋅π interactions. Molecules are linked via C-H⋅⋅⋅X (X = Br) intermolecular hydrogen bond with R 2 2 ( 18 ) motif forming 3D architecture, whereas intramolecular forming S(5) graph set motif such as non-covalent interactions provide fundamental role to design supramolecular architectures, either in organic or metal organic complexes. Computational techniques such as Hirshfeld surface analysis, 3D visualization of intermolecular interactions, and molecular docking studies are incorporated to find best binding affinity with receptors, to explore pharmacological activities of complex.

Encapsulating Semiconductor Quantum Dots in Supramolecular Metal‐Organic Frameworks for Superior Photocatalytic Hydrogen Evolution

AbstractSolar‐to‐hydrogen conversion is a sustainable way of producing renewable fuels, yet the efficiency is limited by the poor photo‐induced charge‐carrier separation on electrode surface. Developing active and stable hydrogen evolution photocatalysts is challenging and entails intelligent material structure design and tailoring. Here, a novel water dispersible supramolecular metal organic framework (SMOF) is employed as a general and high‐performance platform to encapsulate CdS quantum dots (QDs) for achieving highly improved solar‐induced H2‐production activity. Particularly, the CdS QDs@SMOF heterostructure exhibits an excellent H2 generation activity of 49.4 µmol h−1 (TOF = 47.0/h), exceeding those of most reported heterogeneous metal organic frameworks‐based photocatalytic systems. Advanced characterizations disclose that the strong electrostatic interaction and light‐induced charge transfer between SMOF and CdS QDs, combined with the high surface area, water dispersible nature, and abundant reactive centers synergistically contribute to this distinguished photocatalytic performance. The work not only demonstrates the water dispersible SMOF can serve as a versatile and effective platform supporting semiconductor to boost the photocatalytic H2‐production performance without co‐catalysts, but also paves avenues to the design and synthesis of SMOF‐based heterostructures for general catalysis applications.

Structure Evolution and Thermal Decomposition of Supramolecular and Lamellar Hybrid Sulfates Templated by 4-Aminopyridinium

The aromatic diamine 4-aminopyridine was used for the synthesis of a series of supramolecular metal–organic sulfate salts. The obtained compounds with the formula (C5H7N2)2[MII(H2O)6](SO4)2 (MII = Fe, Co, Ni, Cu and Zn) and (C5H7N2)2[Mn(H2O)4(SO4)2] crystallize with a triclinic symmetry (S.G. P \(\overline{1 }\)). These complexes possess a hybrid structure type with an interlayer distance that varies from 10 to 12 Å depending on the metal. The supramolecular aspect of the crystal structure is manifested through mineral layers, which are built up uniquely from hydrogen bonds. The interlayer space is filled with aromatic diamines that form chains through π⋯π interactions. The thermal study in-situ of all metal compounds revealed important stability with the formation of crystalline phases during heating. The dehydration proceeds differently according to the metal incorporated into the structure.

A Nanoporous Supramolecular Metal-Organic Framework Based on a Nucleotide: Interplay of the π···π Interactions Directing Assembly and Geometric Matching of Aromatic Tails.

Self-assembly is the most powerful force for creating ordered supramolecular architectures from simple components under mild conditions. π···π stacking interactions have been widely explored in modern supramolecular chemistry as an attractive reversible noncovalent tool for the nondestructive fabrication of materials for different applications. Here, we report on the self-assembly of cytidine 5’-monophosphate (CMP) nucleotide and copper metal ions for the preparation of a rare nanoporous supramolecular metal-organic framework in water. π···π stacking interactions involving the aromatic groups of the ancillary 2,2’-bipyridine (bipy) ligands drive the self-assemblies of hexameric pseudo-amphiphilic [Cu6(bipy)6(CMP)2(µ-O)Br4]2+ units. Owing to the supramolecular geometric matching between the aromatic tails, a nanoporous crystalline phase with hydrophobic and hydrophilic chiral pores of 1.2 and 0.8 nanometers, respectively, was successfully synthesized. The encoded chiral information, contained on the enantiopure building blocks, is transferred to the final supramolecular structure, assembled in the very unusual topology 8T6. These kinds of materials, owing to chiral channels with chiral active sites from ribose moieties, where the enantioselective recognition can occur, are, in principle, good candidates to carry out efficient separation of enantiomers, better than traditional inorganic and organic porous materials.

Construction of Entropically Favored Supramolecular Metal–Ligand Trimeric Assemblies Supported by Flexible Pyridylaminophosphorus(V) Scaffolds

The self-assembly reactions of tetratopic metal acceptors with the flexible bidentate ligands are known to yield self-assembled molecular squares of the type [M4L8], triangles of composition [M3L6], or a mixture of these two. In this work, we demonstrate the preferential formation of a trimeric cage assembly of the formula [Pd3(L1)6·(BF4)6] (1a) over the tetrameric cage [Pd4(L1)8·(BF4)8] (1b) by employing a flexible dipodal phosphoramide ligand, [PhPO(NH(3-Py))2] (L1; 3-Py = 3-aminopyridine), in a reaction with [Pd(CH3CN)4·(BF4)2]. The entropically favored trimeric self-assembly of 1a is the predominant species in the solution [dimethyl sulfoxide (DMSO)-d6] at room temperature. In fact, at higher temperatures, 1a was found to be the only product, as observed from the disappearance of the peak due to 1b in the 31P NMR spectrum. However, in a 1:1 mixture of acetonitrile (MeCN)-d3 and DMSO-d6, the tetrameric species 1b is the preferred species, as revealed by the 31P NMR and electrospray ionization mass spectral analyses. The structure of the molecular trimer 1a has been established in the solid state by using single-crystal X-ray diffraction analysis. Interestingly, treatment of an another flexible ligand, [MePO(NH(3-Py))2] (L2), with the same Pd(II) acceptor resulted in exclusive formation of the trimeric cage [Pd3(L2)6·(BF4)6] (2).

Boosting Enantioselectivity of Chiral Molecular Catalysts with Supramolecular Metal–Organic Cages

The search for new methodologies to tune and control the enantioselectivities of molecular catalysts is of great importance in the field of asymmetric catalysis. Here, we have illustrated that chir...

Iron(ii) pillared-layer responsive frameworks via “kagomé dual” (kgd) supramolecular tessellations

FeII supramolecular metal organic framework was constructed by supramolecular tessellation. Guest respiration provides dual channel for optical and magnetic sensing based on allosteric effect.

Electric‐Field‐Mediated Electron Tunneling of Supramolecular Naphthalimide Nanostructures for Biomimetic H2 Production

AbstractThe design and synthesis of two semiconducting bis (4‐ethynyl‐bridging 1, 8‐naphthalimide) bolaamphiphiles (BENI‐COO− and BENI‐NH3+) to fabricate supramolecular metal–insulator–semiconductor (MIS) nanostructures for biomimetic hydrogen evolution under visible light irradiation is presented. A H2 evolution rate of ca. 3.12 mmol g−1⋅h−1 and an apparent quantum efficiency (AQE) of ca. 1.63 % at 400 nm were achieved over the BENI‐COO−‐NH3+‐Ni MIS photosystem prepared by electrostatic self‐assembly of BENI‐COO− with the opposite‐charged DuBois‐Ni catalysts. The hot electrons of photoexcited BENI‐COO− nanofibers were tunneled to the molecular Ni collectors across a salt bridge and an alkyl region of 2.2–2.5 nm length at a rate of 6.10×108 s−1, which is five times larger than the BENI‐NH3+ nanoribbons (1.17×108 s−1). The electric field benefited significantly the electron tunneling dynamics and compensated the charge‐separated states insufficient in the BENI‐COO− nanofibers.