Supramolecular Dimers Research Articles

Synthesis, characterization and computational studies of the triangle shape complex of silver nitrate with 2-amino-1,3,4-thiadiazole

A new mononuclear salt-like silver(I) complex [AgL3]NO3 (Complex 1), which was readily fabricated from 2-amino-1,3,4-thiadiazole (L), is reported. Complex 1 was analyzed by elemental analysis, FT-IR and UV–vis spectroscopy, and single crystal X-ray diffraction. Intermolecular contacts for the cation [AgL3]+ in the crystal structure of Complex 1 were examined using the Hirshfeld surface analysis. The DFT-based calculations were additionally applied to reveal electronic features of Complex 1. The molecular structure of Complex 1 exhibits a mononuclear planar cation [AgL3]+ of the triangle shape with three ligands L being monocoordinated through thiadiazole the nitrogen atom, located at the third position. Two cations [AgL3]+, which, in turn, are stabilized by three NH⋯N hydrogen bonds, are stacked through a rich variety of noncovalent interactions formed by the thiadiazole π-system, yielding a supramolecular dimer {[AgL3]2}2+. These dimers are linked through Ag⋯Ag interactions with the formation of a 1D supramolecular cationic pillar {[AgL3]n}n+. A solution of Complex 1 in EtOH absorbs in the UV region due to intraligand transitions within L. Theoretical calculations revealed a strong electrophilic nature of the optimized structure of Complex 1.

Crystal structure and supra-molecular features of a host-guest inclusion complex based on A1/A2-hetero-difunctionalized pillar[5]arene.

A host-guest supra-molecular inclusion complex was obtained from the co-crystallization of A1/A2-bromo-but-oxy-hy-droxy difunctionalized pillar[5]arene (PilButBrOH) with adipo-nitrile (ADN), C47H53.18Br0.82O10·C6H8N2. The adipo-nitrile guest is stabilized within the electron-rich cavity of the pillar[5]arene host via multiple C-H⋯O and C-H⋯π inter-actions. Both functional groups on the macrocyclic rim are engaged in supra-molecular inter-actions with an adjacent inclusion complex via hydrogen-bonding (O-H⋯N or C-H⋯Br) inter-actions, resulting in the formation of a supra-molecular dimer in the crystal structure.

Supramolecular Assemblies in Mn(II) and Zn(II) Metal–Organic Compounds Involving Phenanthroline and Benzoate: Experimental and Theoretical Studies

Two new Mn(II) and Zn(II) metal–organic compounds of 1,10-phenanthroline and methyl benzoates viz. [Mn(phen)2Cl2]2-ClBzH (1) and [Zn(4-MeBz)2(2-AmPy)2] (2) (where 4-MeBz = 4-methylbenzoate, 2-AmPy = 2-aminopyridine, phen = 1,10-phenanthroline, 2-ClBzH = 2-chlorobenzoic acid) were synthesized and characterized using elemental analysis, TGA, spectroscopic (FTIR, electronic) and single crystal X-ray diffraction techniques. The crystal structure analysis of the compounds revealed the presence of various non-covalent interactions, which provides stability to the crystal structures. The crystal structure analysis of compound 1 revealed the formation of a supramolecular dimer of 2-ClBzH enclathrate within the hexameric host cavity formed by the neighboring monomeric units. Compound 2 is a mononuclear compound of Zn(II) where flexible binding topologies of 4-CH3Bz are observed with the metal center. Moreover, various non-covalent interactions, such as lp(O)-π, lp(Cl)-π, C–H∙∙∙Cl, π-stacking interactions as well as N–H∙∙∙O, C–H∙∙∙O and C–H∙∙∙π hydrogen bonding interactions, are found to be involved in plateauing the molecular self-association of the compounds. The remarkable enclathration of the H-bonded 2-ClBzH dimer into a supramolecular cavity formed by two [Mn(phen)2Cl2] complexes were further studied theoretically using density functional theory (DFT) calculations, the non-covalent interaction (NCI) plot index and quantum theory of atoms in molecules (QTAIM) computational tools. Synergistic effects were also analyzed using molecular electrostatic potential (MEP) surface analysis.

Conformation-Associated C···dz2-PtII Tetrel Bonding: The Case of Cyclometallated Platinum(II) Complex with 4-Cyanopyridyl Urea Ligand.

The nucleophilic addition of 3-(4-cyanopyridin-2-yl)-1,1-dimethylurea (1) to cis-[Pt(CNXyl)2Cl2] (2) gave a new cyclometallated compound 3. It was characterized by NMR spectroscopy (1H, 13C, 195Pt) and high-resolution mass spectrometry, as well as crystallized to obtain two crystalline forms (3 and 3·2MeCN), whose structures were determined by X-ray diffraction. In the crystalline structure of 3, two conformers (3A and 3B) were identified, while the structure 3·2MeCN had only one conformer 3A. The conformers differed by orientation of the N,N-dimethylcarbamoyl moiety relative to the metallacycle plane. In both crystals 3 and 3·2MeCN, the molecules of the Pt(II) complex are associated into supramolecular dimers, either {3A}2 or {3B}2, via stacking interactions between the planes of two metal centers, which are additionally supported by hydrogen bonding. The theoretical consideration, utilizing a number of computational approaches, demonstrates that the C···dz2(Pt) interaction makes a significant contribution in the total stacking forces in the geometrically optimized dimer [3A]2 and reveals the dz2(Pt)→π*(PyCN) charge transfer (CT). The presence of such CT process allowed for marking the C···Pt contact as a new example of a rare studied phenomenon, namely, tetrel bonding, in which the metal site acts as a Lewis base (an acceptor of noncovalent interaction).

Halogen Bond-Assisted Supramolecular Dimerization of Pyridinium-Fused 1,2,4-Selenadiazoles via Four-Center Se2N2 Chalcogen Bonding.

The synthesis and structural characterization of α-haloalkyl-substituted pyridinium-fused 1,2,4-selenadiazoles with various counterions is reported herein, demonstrating a strategy for directed supramolecular dimerization in the solid state. The compounds were obtained through a recently discovered 1,3-dipolar cycloaddition reaction between nitriles and bifunctional 2-pyridylselenyl reagents, and their structures were confirmed by the X-ray crystallography. α-Haloalkyl-substituted pyridinium-fused 1,2,4-selenadiazoles exclusively formed supramolecular dimers via four-center Se···N chalcogen bonding, supported by additional halogen bonding involving α-haloalkyl substituents. The introduction of halogens at the α-position of the substituent R in the selenadiazole core proved effective in promoting supramolecular dimerization, which was unaffected by variation of counterions. Additionally, the impact of cocrystallization with a classical halogen bond donor C6F3I3 on the supramolecular assembly was investigated. Non-covalent interactions were studied using density functional theory calculations and topological analysis of the electron density distribution, which indicated that all ChB, XB and HB interactions are purely non-covalent and attractive in nature. This study underscores the potential of halogen and chalcogen bonding in directing the self-assembly of functional supramolecular materials employing 1,2,4-selenadiazoles derived from recently discovered cycloaddition between nitriles and bifunctional 2-pyridylselenyl reagents.

Supramolecular networks featuring diverse array of noncovalent interactions in crystals of hydrazinylidene-benzothiazinediones: X-ray crystallographic, DFT and biochemical analysis

The intricate role of noncovalent interactions in numerous fields including chemistry, biology, catalysis, material science, and medicinal chemistry provides a continuous impetus towards the discovery of new synthons that stabilize the supramolecular architectures. In this regard, the current work presents a series of five hydrazinylidene-benzothiazinedione derivatives encompassing a wide plethora of noncovalent interactions. Despite the configurational similarity of their hydrazinylidene-benzothiazinedione component, the five crystallographic packing arrangements of 7a–c and 9a,b are unique. The principal intermolecular interactions are CH⋯O hydrogen bonds and weak CH···π interactions (Malone Type III). Inversion dimers based on CH⋯Cl interactions form for 7b while CH⋯N and CH⋯S interactions in 9a were also observed. Furthermore, the energetic properties of the supramolecular dimers, centrosymmetric (antiparallel oriented) arrangements in 7a and 7b while parallel oriented arrangements in 9a and 9b have been examined using a combined QTAIM/NCI plot methods. The medicinal chemistry potential against urease enzyme revealed compound 9b as the lead inhibitor with strong efficacy (IC50 = 0.92 ± 0.03 µM). In vitro results were complemented with molecular docking revelations where several key interactions were observed between the potent ligand and active site amino acids. ADMET profile also described compounds 7b and 9b as the best molecules with promising druglike profile.

Heterometallic AuI 6 AgI 6 Macrocyclic Cluster Templated by a Supramolecular Melamine Dimer.

The application of supramolecular templates in aligning atomically precise heterometal arrays is important for pursuing functional materials. Herein, we report that a bilayered supramolecular tri-deprotonated melamine dimer functions as an effective template in the construction of a heterometallic gold(I)-silver(I) macrocyclic cluster [μ6 -(C3 N6 H3 )3- ]2 -AuI 6 AgI 6 . X-ray single crystal structural analysis showed that a crown-like AuI 6 AgI 6 macrocycle is aligned around two parallelly stacked μ6 -(C3 N6 H3 )3- moieties hold together with π-π interactions. Theoretical calculations revealed that the [μ6 -(C3 N6 H3 )3- ]2 motif dominantly contributes to the near-occupied orbitals in the electronic structure, which is closely related to its luminescence properties. This work demonstrates that the supramolecular templates containing multiple symmetric binding sites may present a facile approach in the construction of functional metal clusters.

Engineered π⋯π interactions favour supramolecular dimers X@[FeL3]2 (X = Cl, Br, I): solid state and solution structure.

Ditopic bis-pyrazolylpyridine ligands usually react with divalent metal ions (M2+) to produce dinuclear triple-stranded helicates [M2L3]4+ or, via π⋯π interactions, dimers of monoatomic complexes ([ML3]2)4+. The introduction of an additional benzene ring at each end of ligand L increases the number of aromatic contacts within the supramolecular aggregate by 40%, driving the self-recognition process in an irreversible manner. Consequently, the mixing of new bis-pyrazolylquinoline L2 with FeX2 salts leads to crystallization of the tripartite high-spin assemblies (X@[Fe(L2)3]2)3+ (X = Cl, Br or I). The aggregates exhibit exceptional stability, as confirmed by a combination of paramagnetic 1H NMR techniques, demonstrating their persistence in solution. Our investigations further reveal that the guests Br- and I- are retained inside the associate in solution but Cl- is immediately released, resulting in the formation of the empty supramolecular dimer ([Fe(L2)3]2)4+.

A library of vinyl phosphonate anions dimerize with cyanostars, form supramolecular polymers and undergo statistical sorting.

Supramolecular dimers are elementary units allowing the build-up of multi-molecule architectures. New among these are cyanostar-stabilized dimers of phosphate and phosphonate anions. While the anion dimerization at the heart of these assemblies is reliable, the covalent synthesis leading to this class of designer anions serves as a bottleneck in the pathway to supramolecular assemblies. Herein, we demonstrate the reliable synthesis of 14 diverse anionic monomers by Heck coupling between vinyl phosphonic acid and aryl bromide compounds. When this synthesis is combined with reliable anion dimerization, we show formation of supramolecular dimers and polymers by co-assembly with cyanostar macrocycles. The removal of the covalent bottleneck opened up a seamless synthetic route to iterate through three monomers affording the solubility needed to characterize the mechanism of supramolecular polymerization. We also test the idea that the small size of these vinyl phosphonates provide identical dimer stabilities across the library by showing how mixtures of anions undergo statistical (social) self-sorting. We exploit this property by preparing soluble copolymers from the mixing of different monomers. This multi-anion assembly shows the utility of a library for programming properties.

A supramolecular dimer strategy for enhancing the selective generation of sulfides and sulfoxides by visible-light induced photoredox thiol-ene cross-coupling reactions of anthraquinone

Enhancing the photocatalytic efficiency of organic photocatalysts and increasing the generation capacity of reactive oxygen species (ROS) have consistently been substantial obstacles. In this study, we designed and synthesized a...

Oxazoline amino acid bioconjugates: one-pot synthesis and analysis of supramolecular interactions

Oxazoline amino acid bioconjugates were synthesized; the relative stability of a supramolecular dimer of a tris-derivative was investigated using mean absolute error values (MAE), derived from 1H NMR experiments and DFT calculations.

Supramolecularly Dimeric Assemble of Planar Cu13 Clusters Controlled by the Length of Spacers of Diphosphine.

The controlled formation of dimeric clusters is challenging. Three copper(I) clusters, labeled as {Cu13[o-Ph(C≡C)2]6(L)4}(ClO4), were synthesized by using three different ligands, including 1,4-bis(diphenylphosphino)butane (dppb), 1,5-bis(diphenylphosphino)pentane (dpppe), and bis(diphenylphosphino)hexane (dpph). By increasing the flexibility of alkyl spacers in the diphosphine ligands, the relative positions of the phenyl rings could be optimized to achieve efficient packing with maximized intercluster interactions. In the crystal structures, cluster 1 with dppb ligands did not display interlocked structures. In contrast, cluster 2 with dpppe ligands formed supramolecularly interlocked polymers through weak π-π interactions and C-H···π interactions, while cluster 3 employing dpph ligands formed supramolecularly interlocked dimers with strong π-π interactions and C-H···π interactions. The supramolecular dimer of 3 was also evidenced by analyses through electrospray ionization mass spectrometry and transmission electron microscopy. Density functional theory calculation was used to understand the electronic structure and transitions. Supramolecularly interlocked polymers/dimers with rigid structures exhibited higher quantum efficiency. The solution of these clusters demonstrated remarkable aggregation-induced emission enhancements. This study presents unique examples of planar luminescent copper clusters, featuring the first serial dialkynyl-protected cluster. It underlines the importance of ligand flexibility in creating supramolecular cluster dimers.

Construction of supramolecular dimer based on benzothiazole derivative through host–guest interaction for photocatalysis

AbstractIn recent years, the development of photocatalysts based on noncovalent strategies has shown an important role in medical and organic materials. Herein, an organic fluorescent dye benzothiazole derivative (2‐(N,N‐diethylanilin‐4‐yl)‐4,6‐bis(3‐methylpyrazol‐1‐yl)‐1,3,5‐triazine [MPBT]) was designed and synthesized. It was encapsulated in the cavity of cucurbit[8]uril (CB[8]) to form a supramolecular dimer through host–guest interaction, which converted the dye into a highly efficient photocatalyst. With the formation of 2MPBT‐CB[8] supramolecular dimer, the emergence of host‐enhanced charge transfer interactions could significantly facilitate singlet to triplet through intersystem crossing. At the same time, the alternating structure of 2MPBT‐CB[8] facilitated the triplet states for further energy transfer and electron transfer. In addition, the electron transfer process with electron donor generated cationic free radical and photocatalyst negative ion free radical (), which in turn reacted with oxygen (O2) to form superoxide anion radical (). The generated could be used to catalyze the oxidative hydroxylation of aryl boronic acid. Therefore, the 2MPBT‐CB[8] had become a highly efficient photocatalyst for the oxidative hydroxylation of aryl boronic acid. This strategy of supramolecular dimerization provides a new strategy for the development of new photocatalysts based on noncovalent interactions.

Crystal structure and supramolecular features of a bis-urea-functionalized pillar[5]arene

The crystal structure of a bis-urea derivative based on A1/A2-functionalized pillar[5]arene (DUP) that encapsulates dimethyl formamide (DMF) inside the macrocyclic cavity is reported. The crystal structure of DUP·DMF, C63H70N4O12·C3H7NO, reveals that out of two urea functionalized spacers, one arm is oriented above the macrocyclic cavity with strong hydrogen-bonding interactions between the urea H atoms and DMF guest, whereas, the other arm is positioned away from the macrocycle, leading to intermolecular hydrogen-bonding interactions between the urea H atoms of two adjacent pillar[5]arene macrocycles, resulting in the formation of a supramolecular dimer.

A Modular and Convergent Synthetic Route to Supramolecular Cyclic Dimers Based on Amidinium-Carboxylate Interactions.

We describe herein the optimized design and modular synthetic approach towards supramolecularly programmed monomers that can form discrete macrocyclic species of controllable size and shape through amidinium-carboxylate interactions in apolar and polar media.

A Supramolecular Naphthalene Diimide Radical Anion with Efficient NIR-II Photothermal Conversion for E. coli-Responsive Photothermal Therapy.

We report a supramolecular naphthalene diimide (NDI) radical anion with efficient NIR-II photothermal conversion for E. coli-responsive photothermal therapy. The supramolecular radical anion (NDI-2CB[7])⋅- , which is obtained from the E. coli-induced in situ reduction of NDI-2CB[7] neutral complex, formed by the host-guest interaction between an NDI derivative and cucurbit[7]uril (CB[7]), exhibits unexpectedly strong NIR-II absorption and remarkable photothermal conversion capacity in aqueous solution. The NIR-II absorption is caused by the self-assembly of NDI radical anions to form supramolecular dimer radicals in aqueous solution, which is supported by theoretically predicted spectra. The (NDI-2CB[7])⋅- demonstrates excellent NIR-II photothermal antimicrobial activity (>99 %). This work provides a new approach for constructing NIR-II photothermal agents and non-contact treatments for bacterial infections.

A Supramolecular Naphthalene Diimide Radical Anion with Efficient NIR‐II Photothermal Conversion for E. coli‐Responsive Photothermal Therapy

AbstractWe report a supramolecular naphthalene diimide (NDI) radical anion with efficient NIR‐II photothermal conversion for E. coli‐responsive photothermal therapy. The supramolecular radical anion (NDI‐2CB[7])⋅−, which is obtained from the E. coli‐induced in situ reduction of NDI‐2CB[7] neutral complex, formed by the host–guest interaction between an NDI derivative and cucurbit[7]uril (CB[7]), exhibits unexpectedly strong NIR‐II absorption and remarkable photothermal conversion capacity in aqueous solution. The NIR‐II absorption is caused by the self‐assembly of NDI radical anions to form supramolecular dimer radicals in aqueous solution, which is supported by theoretically predicted spectra. The (NDI‐2CB[7])⋅− demonstrates excellent NIR‐II photothermal antimicrobial activity (>99 %). This work provides a new approach for constructing NIR‐II photothermal agents and non‐contact treatments for bacterial infections.

Three heteroleptic copper(I) complexes with [Cu(P˄P)N2]+ structure and their fluorescence sensing for VOCs

The design and research of luminescent and volatile organic compound (VOC) fluorescent sensing materials are of great significance and challenge. We report herein the ligand substitution reaction and VOC sensing of new heteroleptic [Cu(P˄P)N2]+ type copper(I) complexes. Firstly, three new complexes 1–3 were designed by utilizing a chelate diphosphine ligand 4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene (Xantphos) and synthesized by the substitution reaction of different N‐containing ligands of 4‐PBO (1), 3‐PBO (2), and 4,4′‐Bipy (3) (4‐PBO = 2‐(4′‐pyridyl)‐benzoxazole, 3‐PBO = 2‐(3′‐pyridyl)‐benzoxazole, 4,4′‐Bipy = 4,4′‐bipyridine), respectively. Three complexes were characterized by elemental analysis, spectroscopic analysis (IR, UV–Vis), single‐crystal X‐ray diffraction (SCXRD), and photoluminescence study. The SCXRD study revealed that complexes 1 and 2 both exhibit a molecular structure with tetrahedral copper(I) complex cation and hexafluorophosphate anion, while complex 3 differs in that its cation is a binuclear copper(I) structure bridged by 4,4′‐bipyridine. Three complexes 1–3 present supramolecular ribbon, supramolecular dimer, and supramolecular framework structure, respectively. Some differences of their UV–Vis absorption spectra were explained by TD‐DFT calculation and wavefunction analysis. It is found that 1 has an abnormal luminescence blue shift, and a luminescence mechanism through the high‐energy T2 excited state is proposed by TD‐DFT calculation. Based on 3, a fluorescent test strip was developed, and its fast and selective fluorescent sensing of pyridine vapor through quenching mechanism was successfully realized. The fluorescent quenching mechanism of the material was also studied, and it was proposed that the quenching should be attributed to the photoinduced electron transfer (PET) mechanism.

Structural Elucidation of 2-(6-(Diethylamino)benzofuran-2-yl)-3-hydroxy-4H-chromen-4-one and Labelling of Mycobacterium aurum Cells

Trehalose conjugates of 3-hydroxychromone (3HC) dyes have previously been utilized as fluorescence labels to detect metabolically active mycobacteria with a view to facilitating point-of-care detection of mycobacterial pathogens, especially Mycobacterium tuberculosis. We subjected the 3HC dye 2-(6-(diethylamino)benzofuran-2-yl)-3-hydroxy-4H-chromen-4-one (3HC-2) to a combined X-ray crystallography and density functional theory (DFT) study, and conducted preliminary fluorescence labelling experiments with the model organism Mycobacterium aurum. In the crystal, 3HC-2 exhibits an s-cis conformation of the chromone and the benzofuran moieties about the central C–C bond. According to DFT calculations, the s-cis conformer is about 1.8 kcal mol−1 lower in energy than the s-trans conformer. The solid-state supramolecular structure features hydrogen-bonded dimers and π…π stacking. Fluorescence microscopy revealed fluorescence of M. aurum cells treated with the dye trehalose conjugate 3HC-2-Tre in the GFP channel. It was concluded that s-cis is the preferred conformation of 3HC-2 and that the generally considered non-pathogenic M. aurum can be labelled with the fluorescence probe 3HC-2-Tre for convenient in vitro drug screening of new antimycobacterial agents.

Donor-Acceptor Tribenzotriquinacene-Based Molecular Wizard Hats Bearing Three ortho-Benzoquinone Units.

Two π-extended bay-bridged tribenzotriquinacenes ("TBTQ wizard hats") 12 and 16 bearing three mutually conjugated, alternating veratrole-type and ortho-benzoquinone units were synthesized. The electronic properties of these complementarily arranged, nonplanar push-pull systems are affected by the fusion with the rigid, C3 -symmetric TBTQ core to a different extent, as revealed by X-ray structural analysis, UV-vis spectroscopy and cyclovoltammetry. The combination of three quinone units within the original TBTQ core and three veratrole-type bay bridging units in 12 gives rise to a more efficiently π-conjugated chromophore, as reflected by the shallower shape of wizard hat and its absorption in the visible up to 750 nm in comparison to 16. Congener 12 contains an aromatic 18-π electron system in contrast to the cross-conjugated analog 16. X-ray structure analysis of the precursor dodecaether 15 revealed the formation of a cage-like supramolecular dimer, in which the peripheral dioxane-type ether groups interlace by twelve noncovalent C-H⋅⋅⋅⋅⋅O bonds.