Noncovalent Dualism in Perylene-Diimide-Based Keggin Anion Complexes: Theoretical and Experimental studies

We report the synthesis and comprehensive characterization of organic-inorganic hybrid salts formed by bis-cationic N,N'-bis(2-(trimethylammonium)ethylene)perylene-3,4,9,10-tetracarboxylic acid bisimide (PTCD2+) and Keggin-type [XW12O40]n- (X = Si, n = 4; X = P, n = 3) polyoxometalates. (PTCD)3[PW12O40]2·3DMSO·2H2O (2) and (PTCD)2[SiW12O40]·DMSO·2H2O (3) were structurally characterized by single crystal X-ray diffraction. The cations in both structures exhibited infinite chainlike arrangements through π-π interactions, contrasting with the previously reported cation-anion stacking observed in naphthalene diimide derivatives. A detailed theoretical study employing topological analysis of the electron density distribution within the quantum theory of atoms in molecules approach provided further insights into this structural dualism. Atomic force microscopy analyses revealed the formation of self-assembled supramolecular structures on graphite from molecular monolayers (3 nm of thick) to submicrometer aggregates for 2. Hyperspectral Raman spectroscopy imaging revealed that such heterostructures are likely formed by an enhanced π-π interactions. Both complexes demonstrated interesting electrochemical behavior, photoluminescence and X-ray-induced luminescence. Electron spin resonance analysis confirmed charge separation in both compounds, with enhanced efficiency observed in compound 2. Our findings of these perylene-based organic-inorganic hybrid salts offer the potential for their application in optoelectronic devices and functional materials.

Effects of Bis(imino)acenaphthene (Bian)-Derived Ligands on the Cytotoxicity, DNA Interactions, and Redox Activity of Palladium(II) Bipyridine Complexes

A series of heteroleptic bipyridine Pd(II) complexes based on 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-Bian) or 1,2-bis[(2,4,6-trimethylphenyl)imino]acenaphthene (tmp-Bian) were prepared. All complexes were fully characterized by spectrochemical methods, and their crystal structures were confirmed by X-ray diffraction analysis. The 72 h stability of heteroleptic bipyridine Pd(II) complexes with Bian ligands under physiological conditions was investigated using ¹H NMR spectroscopy. The anticancer activity of all complexes was assessed in a panel of cancer cell lines in comparison with uncoordinated ligands and clinically used drugs cisplatin and doxorubicin. The ability of the complexes to bind DNA was investigated using several methods, including EtBr replacement assay, density functional theory calculations, circular dichroism spectroscopy, DNA gel electrophoresis, and TUNEL assay. The electrochemical activity of all complexes and the uncoordinated ligands was studied using cyclic voltammetry, and reactive oxygen species production in cancer cells was investigated using confocal microscopy. Heteroleptic bipyridine Pd^II-Bian complexes were cytotoxic in a low micromolar concentration range and showed some selectivity toward cancer cells in comparison with noncancerous MRC-5 lung fibroblasts.

Not So Similar: Different Ways of Nb(V) and Ta(V) Catecholate Complexation

The reactions between catechol (H₂cat) and niobium(V) or tantalum(V) precursors in basic aqueous solutions lead to the formation of catecholate complexes of different natures. The following complexes were isolated and characterized by single-crystal X-ray diffraction (SCXRD): (1) (NH₄)₃[NbO(cat)₃]∙4H₂O; (2) K₂[Nb(cat)₃(Hcat)]·2H₂cat·2H₂O; (3) Cs₃[NbO(cat)₃]·H₂O; (4) (NH₄)₄[Ta₂O(cat)₆]·3H₂O; (5) Cs₂[Ta(cat)₃(Hcat)]·H₂cat; (6) Cs₄[Ta₂O(cat)₆]·7H₂O. The isolated crystalline products were characterized by elemental analysis, X-ray powder diffraction (XRPD), FTIR, and TGA. The structural features of these complexes, such as {Ta₂O} unit geometry, Cs-π interactions, and crystal packing effects, are discussed.

Chromium-Lanthanide Complexes Containing the Cr═P═Cr Fragment: Synthesis, Characterization, and Computational Study

Heterometallic complexes [Cp*₂Ln(μ-^isoCO)₂{Cr₂(μ-P)Cp₂(CO)₂}] [Ln = Yb (1), Sm (2)] were obtained in reactions of [Cp*₂Ln(thf)₂] (Ln = Sm, Yb) with [{CpCr(CO)₂}₂(μ,η^2:2-P₂)] (4). An analogous yttrium compound [Cp*₂Y(μ-^isoCO)₂{Cr₂(μ-P)Cp₂(CO)₂}] (3) was synthesized using a three-component reaction between [Cp*₂Y(BPh₄)], 4, and KC₈. Compounds 1-3 were isolated as solvent-free crystalline phases; in the case of 2, the 2·0.5C₇H₈ solvate was also obtained. The structures of all crystalline phases were determined by single-crystal X-ray diffraction analysis. All compounds contain a unique {((CO)₂CpCr═P═CrCp(CO)₂)}^- unit, which is linked to Ln³⁺ ions through CO ligands in the isocarbonyl mode. Compounds 1 and 3 have a molecular structure, while compound 2 contains polymeric chains of triangular [Cp*₂Sm(μ-^isoCO)₂{Cr₂(μ-P)Cp₂(CO)₂}] units linked by μ-^isoCO-ligands. ³¹P NMR studies demonstrated similar dramatic downfield shifts for complexes 1-3. To realize the electronic structure of 1-3 and to elucidate the nature of the high downfield chemical ³¹P shift, quantum chemical calculations were performed both for 1-3 and for related Cr- and Fe-phosphido complexes. Calculations show that the anomalously high downfield chemical shifts for 1-3 are due to the anisotropic effect of the Cr═P double bonds.

Iridium Complexes with BIAN-Type Ligands: Synthesis, Structure and Redox Chemistry

A series of iridium complexes with bis(diisopropylphenyl)iminoacenaphtene (dpp-bian) ligands, [Ir(cod)(dpp-bian)Cl] (1), [Ir(cod)(NO)(dpp-bian)](BF₄)₂ (2) and [Ir(cod)(dpp-bian)](BF₄) (3), were prepared and characterized by spectroscopic techniques, elemental analysis, X-ray diffraction analysis and cyclic voltammetry (CV). The structures of 1-3 feature a square planar backbone consisting of two C = C π-bonds of 1,5-cyclooctadiene (cod) and two nitrogen atoms of dpp-bian supplemented with a chloride ion (for 1) or a NO group (for 2) to complete a square-pyramidal geometry. In the nitrosyl complex 2, the Ir-N-O group has a bent geometry (the angle is 125°). The CV data for 1 and 3 show two reversible waves between 0 and -1.6 V (vs. Ag/AgCl). Reversible oxidation was also found at E_1/2 = 0.60 V for 1. Magnetochemical measurements for 2 in a range from 1.77 to 300 K revealed an increase in the magnetic moment with increasing temperature up to 1.2 μ_B (at 300 K). Nitrosyl complex 2 is unstable in solution and loses its NO group to yield [Ir(cod)(dpp-bian)](BF₄) (3). A paramagnetic complex, [Ir(cod)(dpp-bian)](BF₄)₂ (4), was also detected in the solution of 2 as a result of its decomposition. The EPR spectrum of 4 in CH₂Cl₂ is described by the spin Hamiltonian Ĥ = gβHŜ with S = 1/2 and g_xx = g_yy = 2.393 and g_zz = 1.88, which are characteristic of the low-spin 5d⁷-Ir(II) state. DFT calculations were carried out in order to rationalize the experimental results.

Signatures of pancake bonding in hydrated eumelanin

Pancake bonding phenomenology is applied for the first time in a bioorganic system, the pigment eumelanin, via a hydration-induced decrease of the interplanar distance down to 3.19 Å. The observation explains the long-term inconsistency between electron paramagnetic resonance and muon spin relaxation data for eumelanin.

Novel Route to Cationic Palladium(II)-Cyclopentadienyl Complexes Containing Phosphine Ligands and Their Catalytic Activities

The Pd(II) complexes [Pd(Cp)(L)_n]_m[BF₄]_m were synthesized via the reaction of cationic acetylacetonate complexes with cyclopentadiene in the presence of BF₃∙OEt₂ (n = 2, m = 1: L = PPh₃ (1), P(p-Tol)₃, tris(ortho-methoxyphenyl)phosphine (TOMPP), tri-2-furylphosphine, tri-2-thienylphosphine; n = 1, m = 1: L = dppf, dppp (2), dppb (3), 1,5-bis(diphenylphosphino)pentane; n = 1, m = 2 or 3: 1,6-bis(diphenylphosphino)hexane). Complexes 1-3 were characterized using X-ray diffractometry. The inspection of the crystal structures of the complexes enabled the recognition of (Cp^-)⋯(Ph-group) and (Cp^-)⋯(CH₂-group) interactions, which are of C-H…π nature. The presence of these interactions was confirmed theoretically via DFT calculations using QTAIM analysis. The intermolecular interactions in the X-ray structures are non-covalent in origin with an estimated energy of 0.3-1.6 kcal/mol. The cationic palladium catalyst precursors with monophosphines were found to be active catalysts for the telomerization of 1,3-butadiene with methanol (TON up to 2.4∙10⁴ mol 1,3-butadiene per mol Pd with chemoselectivity of 82%). Complex [Pd(Cp)(TOMPP)₂]BF₄ was found to be an efficient catalyst for the polymerization of phenylacetylene (PA) (catalyst activities up to 8.9 × 10³ g_PA·(mol_Pd·h)^-1 were observed).

NMR-Relaxometric Investigation of Mn(II)-Doped Polyoxometalates in Aqueous Solutions

Solution behavior of K;₅[(Mn(H₂O))PW₁₁O₃₉]·7H₂O (1), Na_3.66(NH₄)_4.74H_3.1[(Mn^II(H₂O))_2.75(WO(H₂O))_0.25(α-B-SbW₉O₃₃)₂]·27H₂O (2), and Na_4.6H_3.4[(Mn^II(H₂O)₃)₂(WO₂)₂(β-B-TeW₉O₃₃)₂]·19H₂O (3) was studied with NMR-relaxometry and HPLC-ICP-AES (High Performance Liquid Chromatography coupled with Inductively Coupled Plasma Atomic Emission Spectroscopy). According to the data, the [(Mn(H₂O))PW₁₁O₃₉]^5- Keggin-type anion is the most stable in water among the tested complexes, even in the presence of ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA). Aqueous solutions of 2 and 3 anions are less stable and contain other species resulting from dissociation of Mn²⁺. Quantum chemical calculations show the change in Mn²⁺ electronic state between [Mn(H₂O)₆]²⁺ and [(Mn(H₂O))PW₁₁O₃₉]^5-.

The influence of copper ions on the transport and relaxation properties of hydrated eumelanin

Eumelanin, the human skin pigment, is a poly-indolequinone material possessing a unique combination of physical and chemical properties. For numerous applications, the conductivity of eumelanin is of paramount importance. However, its hydration dependent conductivity is not well studied using transport-relaxation methods. Furthermore, there is no such work taking into account the simultaneous control of humidity as well as metal ion concentration. Here we present the first such study of the transport and relaxation characteristics of synthetic eumelanin doped with various Cu ion concentrations while controlling the humidity with a frequency range of 10^-3 Hz-1 MHz. We found that Cu ions do not cause the appearance of additional relaxation processes, but partially slow down those present in neat eumelanin. In addition, considering previously published work, the key relaxation process observed in doped and undoped materials is associated with the moisture-induced synthesis of uncharged semiquinones and a corresponding increase in the overall aromaticity of the material.

Halogen Bonding Channels for Magnetic Exchange in Cu(II) Complexes with 2,5-Di(methylthio)-1,3,4-thiadiazole

Copper(II) complexes with 2,5-bis(methylthio)-1,3,4-thiadiazole (tda) formulated as [Cu(tda)_n X₂ ] (n=2, X=Cl^- , Br^- , C₂ N₃ ^- ; n= 1, X=C₂ N₃ ^- ) have been isolated and fully characterized. The crystal structures of all compounds have been determined using single-crystal X-ray diffraction (SCXRD). A study of the magnetic susceptibility in the range 1.77-300 K has shown that magnetic properties of the [Cu(tda)₂ Cl₂ ] and [Cu(tda)₂ Br₂ ] complexes match those of 1D chains of antiferromagnetically-coupled Cu²⁺ ions. The intrachain interaction J in [Cu(tda)₂ Cl₂ ] turns out to be ∼1.2 times weaker than in its bromide analogue. In its turn, [Cu(tda)₂ (C₂ N₃ )₂ ] exhibits J being an order of magnitude smaller and of the opposite ferromagnetic sign. Halogen bonding (HB) between adjacent complexes is much stronger than the H-bonds or π-π interactions between tda ligands according to the DFT calculations.

One-Dimensional Iodoantimonate(III) and Iodobismuthate(III) Supramolecular Hybrids with Diiodine: Structural Features, Stability and Optical Properties

Two isostructural pairs of supramolecular iodoantimonate(III) and iodobismuthate(III) complexes with I₂ units "trapped" in solid state via halogen bonding-Cat₃[[M₂I₉](I₂)} (Cat = tetramethylammonium and 1-methylpyridinium, M = Sb(III) and Bi(III)) were prepared. For all compounds, values of optical band gaps were determined, together with thermal stability; the complexes were additionally characterized by Raman spectroscopy.

Proton Affinity in the Chemistry of Beta-Octamolybdate: HPLC-ICP-AES, NMR and Structural Studies

The affinity of [β-Mo₈O₂₆]^4- toward different proton sources has been studied in various conditions. The proposed sites for proton coordination were highlighted with single crystal X-ray diffraction (SCXRD) analysis of (Bu₄N)₃[β-{Ag(py-NH₂)Mo₈O₂₆]}] (1) and from analysis of reported structures. Structural rearrangement of [β-Mo₈O₂₆]^4- as a direct response to protonation was studied in solution with ⁹⁵Mo NMR and HPLC-ICP-AES techniques. A new type of proton transfer reaction between (Bu₄N)₄[β-Mo₈O₂₆] and (Bu₄N)₄H₂[V₁₀O₂₈] in DMSO results in both polyoxometalates transformation into [V₂Mo₄O₁₉]^4-, which was confirmed by the ⁹⁵Mo, ⁵¹V NMR and HPLC-ICP-AES techniques. The same type of reaction with [H₄SiW₁₂O₄₀] in DMSO leads to metal redistribution with formation of [W₂Mo₄O₁₉]^2-.

Coordination of Pt(IV) by {P8W48} Macrocyclic Inorganic Cavitand: Structural, Solution, and Electrochemical Studies

Hydrothermal reaction of a macrocyclic inorganic POM cavitand Li₁₇(NH₄)₂₁H₂[P₈W₄₈O₁₈₄] with [Pt(H₂O)₂(OH)₄] results in coordination of up to six {Pt(H₂O)_x(OH)_4-x} fragments to the internal surface of the polyoxoanion. The product was isolated as K₂₂(NH₄)₉H₃[{Pt(OH)₃(H₂O)}₆P₈W₄₈O₁₈₄]·79H₂O (1) and characterized by multiple techniques in the solid state (SCXRD, XRPD, XPS, FTIR, and TGA) and in solution (NMR, ESI-MS, and HPLC-ICP-AES). Electrochemical properties were studied both in solution and as components of the paste electrode. The complex shows electrocatalytic activity in water oxidation.

Supramolecular Diiodine-Bromostannate(IV) Complexes: Narrow Bandgap Semiconductors

Three supramolecular bromostannates(IV) with "trapped" diiodine molecules, Cat₂{[SnBr₆](I₂)} (Cat = Me₄N⁺ (1), 1-MePy⁺ (2) and 4-MePyH (3)), were synthesized. In all cases, I₂ linkers are connected with bromide ligands via halogen···halogen non-covalent interactions. Articles 1-3 were studied using Raman spectroscopy, thermogravimetric analysis, and diffuse reflectance spectroscopy. The latter indicates that 1-3 are narrow band gap semiconductors.

Heteroleptic Pd(II) and Pt(II) Complexes with Redox-Active Ligands: Synthesis, Structure, and Multimodal Anticancer Mechanism

A series of heteroleptic square-planar Pt and Pd complexes with bis(diisopropylphenyl) iminoacenaphtene (dpp-Bian) and Cl, 1,3-dithia-2-thione-4,5-dithiolate (dmit), or 1,3-dithia-2-thione-4,5-diselenolate (dsit) ligands have been prepared and characterized by spectroscopic techniques, elemental analysis, X-ray diffraction analysis, and cyclic voltammetry (CV). The intermolecular noncovalent interactions in the crystal structures were assessed by density functional theory (DFT) calculations. The anticancer activity of Pd complexes in breast cancer cell lines was limited by their solubility. Pd(dpp-Bian) complexes with dmit and dsit ligands as well as an uncoordinated dpp-Bian ligand were devoid of cytotoxicity, while the [Pd(dpp-Bian)Cl₂] complex was cytotoxic. On the contrary, all Pt(dpp-Bian) complexes demonstrated anticancer activity in a low micromolar concentration range, which was 8-20 times higher than the activity of cisplatin, and up to 2.5-fold selectivity toward cancer cells over healthy fibroblasts. The presence of a redox-active dpp-Bian ligand in Pt and Pd complexes resulted in the induction of reactive oxygen species (ROS) in cancer cells. In addition, these complexes were able to intercalate into DNA, indicating the dual mechanism of action.

Сu(II) 3,5-diiodosalicylate complexes: precursor-dependent formation of mono-, di-, tri- and tetranuclear compounds and 1D coordination polymers

Reactions of CuCl2·2H2O or Cu(NO3)2·6H2O with 3,5-diiodosalicylic acid (DISA) in presence of different amines result in structurally diverse products. Overall, we isolated 14 complexes of various nuclearity (1, 2, 3...

Structural features of selenate based {Mo132} keplerate capsules

A new structural feature and significant stabilizing effect were found for keplerate-type nanospherical polyoxometalates.

Dichlorine-containing chlorobismuthate(iii) supramolecular hybrid: structure and experimental studies of stability

The chlorine-rich complex (Me4N)3{[Bi2Cl9](Cl2)} (1) features dichlorine units incorporated into a chlorometalate matrix via halogen bonding.

Self-assembly patterns of non-metalloid silver thiolates: structural, HR-ESI-MS and stability studies

Screening of AgNO₃/AgS^tBu solutions in DMF, DMSO and NMP resulted in the isolation of three novel nanosized silver/thiolate complexes with a torus-like {Ag₂₀(S^tBu)₁₀} core. The structures of [NO₃@Ag₂₀(S^tBu)₁₀(NO₃)₉(DMF)₆] (1) and [NO₃@Ag₂₀(^tBuS)₁₀(NO₃)₈(NMP)₈][NO₃@Ag₁₉(^tBuS)₁₀(NO₃)₈(NMP)₆]₂(NO₃) (2) were studied by single crystal X-ray diffraction (SCXRD). The self-assembly process leading to 1 can be switched to a different outcome using Br^-, resulting in [Br@Ag₁₆(S^tBu)₈(NO₃)₅(DMF)₃](NO₃)₂ (3), which is the one of the few genuine host-guest complexes in the silver/thiolate systems. Solutions of the individual complexes in CH₃CN were studied by HR-ESI-MS techniques, which revealed a dynamic behavior for each complex, driven by a redistribution of the {AgNO₃} units. This dynamics results in the appearance of both cationic and anionic species, based on unchanged silver-thiolate cores. Daylight causes degradation of 3 with the formation of a composite material based on defective orthorhombic Ag₂S with a porous morphology, as observed using the SEM technique. The electrocatalytic HER activity of such a material was studied.

Water-Activated Semiquinone Formation and Carboxylic Acid Dissociation in Melanin Revealed by Infrared Spectroscopy

Eumelanin is a widespread biomacromolecule pigment in the biosphere and has been widely investigated for numerous bioelectronics and energetic applications. Many of these applications depend on eumelanin's ability to conduct proton current at various levels of hydration. The origin of this behavior is connected to a comproportionation reaction between oxidized and reduced monomer moieties and water. A hydration-dependent FTIR spectroscopic study on eumelanin is presented herein, which allows for the first time tracking the comproportionation reaction via the gradual increase of the overall aromaticity of melanin monomers in the course of hydration. We identified spectral features associated with the presence of specific "one and a half" C𝌁O bonds, typical for o-semiquinones. Signatures of semiquinone monomers with internal hydrogen bonds and that carboxylic groups, in contrast to semiquinones, begin to dissociate at the very beginning of melanin hydration were indicated. As such, we suggest a modification to the common hydration-dependent conductivity mechanism and propose that the conductivity at low hydration is dominated by carboxylic acid protons, whereas higher hydration levels manifest semiquinone protons.

Intramolecular aurophilic interactions in dinuclear gold(I) complexes with twisted bridging 2,2'-bipyridine ligands

Elimination of the chloride ion from the [(PPh₃)AuCl] complex using silver triflate (AgOTf) in the presence of 2,2'-bipyridine R₂bpy (the Au : R₂bpy molar ratio is 2 : 1) in dichloromethane at room temperature leads to dinuclear gold(I) complexes [(PPh₃Au)₂(μ-R₂bpy)](OTf)₂ (R₂bpy = bpy (1), dbbpy (2), CH₃Obpy (3), 3-CO₂CH₃bpy (4), 4-CO₂CH₃bpy (5)) in high yields. The crystal structures for all compounds were determined using X-ray diffraction analysis. In all structures, gold ions are in a typical linear environment, and the bipyridine molecule is twisted, which allows intramolecular aurophilic interactions. Relatively short Au(I)⋯Au(I) contacts (3.1262 (2)-3.400 (1) Å) are found in structures 3-5. DFT calculations show the presence of bond critical points (3, -1) for aurophilic interactions in these structures. In structures 1 and 2, the Au(I)⋯Au(I) distances are noticeably larger and equal to 4.479 (1) and 4.589 (1) Å respectively; there are no bond critical points (3, -1) for aurophilic interactions. All complexes show photoluminescence in solid state at room temperature when excited at 300 nm in a wide spectral range: from blue or blue-green emission (400-460 nm) for 1-4 to orange emission (580 mn) for 5. The lifetimes of the excited state are in the microsecond range which is characteristic of phosphorescence. TD-DFT calculations reveal that electronic transitions of different nature are responsible for the photoluminescence of these compounds.

Oxochloroselenate(IV) with Incorporated {Cl2 }: The Case of Strong Cl⋅⋅⋅Cl Halogen Bonding

Reaction of SeO₂ , tetramethylammonium (TMA) chloride, aqueous HCl and Cl₂ yields oxochloroselenate with incorporated Cl₂ units, TMA₃ {[Se₂ O₂ Cl₇ ](Cl₂ )}. The main feature of this compound is the strong (up to 3.5 kcal mol^-1 , according to DFT calculations) Cl⋅⋅⋅Cl bonding, which is also detected by Raman spectroscopy.

Keggin-type polyoxometalate 1 : 1 complexes of Pb(II) and Bi(III): experimental, theoretical and luminescence studies

Bi3+ and Pb2+ uptake by a monolacunary Keggin-type [PW11O39]7- anion leads to the formation of [PW11O39Bi]4- and [PW11O39Pb]5- complexes with a stereochemically active lone pair at the incorporated heterometal. The two complexes were isolated as (TBA)4[PW11O39Bi] (1) and (TBA)5[PW11O39Pb] (2) and characterized by 31P and 183W NMR spectroscopy, high-resolution electrospray mass-spectrometry (HR-ESI-MS) and cyclic voltammetry (CV). EXAFS and XANES data confirm the unchanged oxidation state and ψ-square pyramidal geometry of Bi3+ and Pb2+ in 1 and 2. DFT calculations were used in order to (i) confirm the absence of ligands attached to the heterometal sites in both complexes and localize the lone pair, and (ii) assign all signals in the 183W NMR spectra. Complexes 1 and 2 demonstrate photoluminescence (PL). A reversible change in the PL spectra of both complexes in the presence of water vapor has been detected. On the contrary, PL data for sandwich-type ((CH3)4N)4K3[H4(PW11O39)2Bi]·25H2O (3) do not show sensitivity to water vapor.

"Host in Host" Supramolecular Core-Shell Type Systems Based on Giant Ring-Shaped Polyoxometalates

Herein, we show how the chaotropic effect arising from reduced molybdate ions in acidified aqueous solution is able to amplify drastically weak supramolecular interactions. Time-resolved Small Angle X-ray Scattering (SAXS) analysis suggests that molybdenum-blue oligomeric species form huge aggregates in the presence of γ-cyclodextrin (γ-CD) which results in the fast formation of nanoscopic {Mo₁₅₄ }-based host-guest species, while X-ray diffraction analysis reveals that the ending-point of the scenario results in an unprecedented three-component well-ordered core-shell-like motif. A similar arrangement was found by using preformed hexarhenium chalcogenide-type cluster [Re₆ Te₈ (CN)₆ ]^4- as exogenous guest. This seminal work brings better understanding of the self-assembly processes in general and gives new opportunities for practical applications in the design of complex multicomponent materials via the simplicity of the non-covalent chemistry.

Tubular polyoxoanion [(SeMo6O21)2(C2O4)3]10− and its transformations

Tubular [(SeMo₆O₂₁)₂(C₂O₄)₃]¹⁰⁻ polyoxoanion can be assembled from Na₂MoO₄/SeO₂/H₂C₂O₄ system. TBABr precipitates complexes of [Mo₆O₁₉]²⁻ and [β-Mo₈O₂₆Na₂(NO₃)]³⁻ from its aqueous solution. Speciation of [β-Mo₈O₂₆]⁴⁻ and [Mo₆O₁₉]²⁻ has been studied.

Unusual π–π interactions directed by the [{(C6H6)Ru}2W8O30(OH)2]6− hybrid anion

The [{(C₆H₆)Ru}₂W₈O₃₀(OH)₂]⁶⁻ hybrid anion as a new type of π–π stacking induced building block and methanol oxidation precatalyst.

Interactions of aromatic rings in the crystal structures of hybrid polyoxometalates and Ru clusters

Computational analysis for π–π interaction energies of {(arene)Ru}2+ containing complexes and relative group 5 hybrid polyoxometalates reveals different frameworks. Some perspectives on πOF materials processing and crystal engineering were discussed.

Solvatomorphs of (Bu4N)2[{Ag(N2-py)}2Mo8O26]: structure, colouration and phase transition

(Bu4N)2[β-{Ag(N2-py)}2Mo8O26] demonstrates monomer/polymer dualism and a colouration phenomenon. The polymeric phase reveals a Ag assisted phase transition. Such complexes can act as precursors for catalytically active materials.

Coordination capacity of Keggin anions as polytopic ligands: case study of [VNb12O40]15

Reaction of Na9H4[VNb12O40{NbO(CO3)}2] with [(C6H6)RuCl2]2 (molar ratio {VNb12} : {(C6H6)Ru} = 1 : 4) in aqueous solution gives a mixture of [α-{(C6H6)Ru}4VNb12O40]7- and [α-{(C6H6)Ru}3VNb12O40]9-. Direct acetone diffusion into mother liquor leads to crystallization of Na6H[α-{(C6H6)Ru}4VNb12O40]·41.25H2O (1), characterized by single crystal X-ray diffraction (SCXRD). This anion has four organometallic fragments coordinated to the α-Keggin type [VNb12O40]15- backbone in different manner. Three {(C6H6)Ru}2+ groups cap triangular faces and one group a rectangular face of [VNb12O40]15-. Equilibrated mixture of [α-{(C6H6)Ru}4VNb12O40]7- and [α-{(C6H6)Ru}3VNb12O40]9- was studied by 1H DOSY NMR, HPLC-ICP-AES and HPLC-ESI-MS combined techniques. Direct chromatographic separation of these complexes results in unexpected transformation of both species into [α-{(C6H6)Ru}5VNb12O40]5-, isolated and characterized as Na5[α-{(C6H6)Ru}5VNb12O40]·16H2O (2). This anion contains five coordinated organometallic groups occupying both triangular and rectangular faces.

Proton motion inside [(DMF)2H]2[W6Cl14]: structural, Raman and luminescence studies

Protonation of DMF by (H₇O₃)₂[W₆Cl₁₄] results in the appearance of strongly proton coupled [(DMF)₂H]⁺ dimers. Such units are captured as the cationic part of [(DMF)₂H]₂[W₆Cl₁₄] (1). The proton behavior in such dimers was studied for the first time with single crystal X-ray diffraction (XRD) and ¹H MAS NMR, Raman and photoluminescence (PL) spectroscopic techniques. The experimental data reveal the presence of two types of [(DMF)₂H]⁺ dimers in 1 (cisoidal and transoidal, with respect to the mutual orientations of their C-O groups) which differ in terms of the degree to which they interact with the cluster anions as the temperature decreases. At room temperature all the OO distances in the [(DMF)₂H]⁺ dimers are very short (2.375 Å) and almost equal. ¹H MAS NMR spectra show a resonance line at 18.7 ppm which is very close to that observed in sodium hydrogen maleate with a strong hydrogen bond belonging to a single-well potential of proton motion. The temperature decrease leads to the differentiation of [(DMF)₂H]⁺ dimers due to the elongation of the OO distance in one pair while keeping a practically constant OO distance in the second pair. The analysis of the cation-anion interactions reveals a strong difference between these two types of dimers which results from the shifting of one DMF molecule toward a terminal Cl^- ligand of the cluster anion. The DFT calculations were used to show the difference in OH⁺O stretches for two different dimers. Moreover, we have found the PL of such dimeric units in the solid state. The temperature screening of the PL behavior demonstrates two types of luminescent centers at low temperatures which coalesce at 298 K. The proton motion in the hydrogen bond was studied using Raman spectroscopy, which was beneficial to monitor the complex behavior over a very broad temperature range from 5 to 298 K. According to the Raman data, we are dealing with a symmetric double-well potential for the hydrogen bond at room temperature, which becomes a broad single well potential below 110 K for the [(DMF)₂H]⁺ cation with a longer OO distance (the cisoidal isomer) and below 60 K for the [(DMF)₂H]⁺ cation with a shorter OO distance (the transoidal isomer).

Cyclodextrin-Assisted Hierarchical Aggregation of Dawson-type Polyoxometalate in the Presence of {Re6Se8} Based Clusters

The association of metallic clusters (CLUS) and polyoxometalates (POM) into hierarchical architectures is achieved using γ-cyclodextrin (γ-CD) as a supramolecular connector. The new self-assembled systems, so-called CLUSPOM, are formed from Dawson-type polyoxometalate [P₂W₁₈O₆₂]^6- and electron-rich rhenium clusters. It is worth noting that a cluster-based cation [{Re₆Se₈}(H₂O)₆]²⁺ on one hand and a cluster-based anion on the other hand [{Re₆Se₈}(CN)₆]^4- can be associated with the anionic POM. In the absence of the supramolecular connector, a "CLUSPOM salt" was obtained from aqueous solution of the cationic cluster and the polyoxometalate. In this solid, the arrangement between the polymetallic building blocks is mainly governed by long-range Coulombic interactions. In the presence of γ-CD, the Dawson anion and the cationic cluster are assembled differently, forming a hierarchical supramolecular solid, K₂[{Re₆Se₈}(H₂O)₆]₂{[P₂W₁₈O₆₂]@2γ-CD}·42H₂O, where the organic macrocycle acts as a ditopic linker between the inorganic building blocks. In such an edifice, the short-range molecular recognition dominates the long-range Coulombic interactions leading to a specific three-dimensional organization. Interestingly, the assembling of anionic POM [P₂W₁₈O₆₂]^6- with the anionic rhenium cluster [{Re₆Se₈}(CN)₆]^4- is also achieved with γ-CD despite the repulsive forces between the nanosized anions. The resulting solid, K₁₀{[{Re₆Se₈}(CN)₆]@2γ-CD}[P₂W₁₈O₆₂]·33H₂O, is built from 1:2 inclusion complexes {[{Re₆Se₈}(CN)₆]@2γ-CD}^4- linked by a POM unit interacting with the exterior wall of the organic macrocycle. Multinuclear NMR and small-angle X-ray scattering investigations support supramolecular preorganization in aqueous solution prior to crystallization.

Memory devices based on novel alkyl viologen halobismuthate(iii) complexes

Four novel halobismuthate(iii) complexes with alkyl viologen cations: (R2Viol)2[Bi2X10] (R = n-butyl, n-pentyl, X = Cl, Br) have been synthesized. Both chloride complexes revealed photochromic behavior and were successfully utilized for the fabrication of OFET-based memory devices with high switching coefficients and good write-read-erase cycling stability.

From Specific γ-CD/[Nb6 Cl12 (H2 O)6 ]2+ Recognition to Biological Activity Tuning

Specific molecular recognition of γ-cyclodextrin (γ-CD) by the cationic hexanuclear niobium [Nb₆ Cl₁₂ (H₂ O)₆ ]²⁺ cluster complex in aqueous solutions results in a 1:1 supramolecular assembly {[Nb₆ Cl₁₂ (H₂ O)₆ ]@γ-CD}²⁺ . NMR spectroscopy, isothermal titration calorimetry (ITC), and ESI-MS were used to study the interaction between the inorganic cluster and the organic macrocycle. Such molecular association affects the biological activity of [Nb₆ Cl₁₂ (H₂ O)₆ ]²⁺ , decreasing its cytotoxicity despite enhanced cellular uptake. The 1:1 stoichiometry is maintained in solution over a large window of the reagents' ratio, but crystallization by slow evaporation produces a 1:2 host-guest complex [Nb₆ Cl₁₂ (H₂ O)₆ @(γ-CD)₂ ]Cl₂ ⋅20 H₂ O featuring the cluster encapsulated between two molecules of γ-CD. The 1:2 complex was characterized by XRD, elemental analysis, IR spectroscopy, and thermogravimetric analysis (TGA). Quantum chemical calculations were performed to model host-guest interaction.

Self-Assembly of Ag+/[PW11NbO40]4- Complexes in Nonaqueous Solutions

Self-assembly between Ag⁺ and [PW₁₁NbO₄₀]^4- in N- and O-donor solvents (nitriles and amides) has been studied. In the case of dimethylformamide (DMF), formation of a yellow [Ag₄(DMF)₁₂][PW₁₁NbO₄₀] (1a) metastable phase and a colorless [Ag₄(DMF)₁₀][PW₁₁NbO₄₀] (1) stable phase was observed. In acetonitrile (CH₃CN), the product was [Ag(CH₃CN)₄]₂{[Ag(CH₃CN)₃]₂[PW₁₁NbO₄₀]} (2a). By contrast, [SiW₁₂O₄₀]^4- of the same size and charge as [PW₁₁NbO₄₀]^4- produces [Ag(CH₃CN)₃]₄[SiW₁₂O₄₀] (3a). Partial desolvation of 2a and 3a leads to Ag₄[PW₁₁NbO₄₀]·7.5CH₃CN (2) and Ag₄[SiW₁₂O₄₀]·7.5CH₃CN (3), respectively. The CH₃CN molecules in the structure of 2 are labile, and this compound was used as the starting material to study solvent-exchange processes in N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMA), diethylformamide (DEF), and benzonitrile (PhCN) solutions. These solvent reactions yield [Ag(DMA)₄][Ag₃(DMA)₆][PW₁₁NbO₄₀] (4), [Ag₂(NMP)₄(CH₃CN)]₂[PW₁₁NbO₄₀]·1.3NMP (5a), [Ag₂(NMP)₅]₂[PW₁₁NbO₄₀] (5b), Ag₄[PW₁₁NbO₄₀]·9.5DEF (6), and [Ag(PhCN)₄]₂[{Ag(PhCN)₃}₂PW₁₁NbO₄₀] (7). All products were isolated and characterized by single-crystal X-ray diffraction (except for 2 and 3), IR, elemental analysis, and thermogravimetric analysis techniques. The O-donor solvents favor polynuclear, solvent-bridged cationic aggregates. In the case of DMF, DMA, and DEF discrete, tri- and tetranuclear polycations are observed, while in the case of NMP, the formation of infinite polycationic structures takes place. By contrast, the N-donor solvents (CH₃CN and PhCN) favor mononuclear cations, which can exist either as distorted tetrahedral, isolated [Ag(Solv)₄]⁺ cations or as pseudotriangular {Ag(Solv)₃}⁺ units, additionally coordinated to a polyoxometalate. Screening of the luminescent properties for solid samples of 1-7 revealed that only 5a/5b and 7 are emissive. In particular, the sample containing 5a and 5b demonstrates long-lived phosphorescence with a 30 ms lifetime.

[{AgL}2Mo8O26]n– complexes: a combined experimental and theoretical study

Two sets of silver–molybdate complexes with L = XR₃ (X = P, As, Sb; R₃ = Ph₃, Ph₂Py) and functionalized pyridine-based ligands have been studied with different techniques.

Chlorotellurate(iv) supramolecular associates with “trapped” Br2: features of non-covalent halogen⋯halogen interactions in crystalline phases

Reactions of chlorotellurates(iv) and Br₂ afford formation of supramolecular complexes Cat₂{[TeCl₆](Br₂)} (Cat = Me₃N⁺ (1), PyH⁺ (2), 4-MePyH⁺ (3) and 1-MePy⁺ (4)) where dibromine fragments are “trapped” by [TeCl₆]³⁻via Br⋯Cl halogen bonding.

Reactions of [Ru(NO)Cl5]2- with pseudotrilacunary {XW9O33}9- (X = AsIII, SbIII) anions

Reactions of [Ru(NO)Cl₅]^2- with pseudotrivacant B-α-[XW₉O₃₃]^9- (X = As^III, Sb^III) at 160 °C result in the rearrangement of polyoxometalate backbones into {XM₁₈} structures. In the case of arsenic, oxidation of As^III to As^V takes place with the formation of a mixture of plenary and monosubstituted Dawson [As₂W₁₈O₆₂]^6- and [As₂W₁₇Ru(NO)O₆₁]^7- anions, of which the latter was isolated as Me₂NH₂⁺ (DMA-1a and DMA-1b) and Bu₄N⁺ (Bu₄N-1) salts and fully characterized. Both α₁ and α₂ isomers of [As₂W₁₇Ru(NO)O₆₁]^7- were present in the reaction mixture; pure [α₂-As₂W₁₇Ru(NO)O₆₁]^7- was isolated as the Bu₄N⁺ salt. In the case of antimony, [SbW₉O₃₃]^9- is converted into a mixture of [SbW₁₈O₆₀]^9- and [SbW₁₇{Ru(NO)}O₅₉]^10-. The formation of trisubstituted [SbW₁₅{Ru(NO)}₃O₅₇]^12- as a minor byproduct was detected by HPLC-ICP-AES. The monosubstituted [SbW₁₇{Ru(NO)}O₅₉]^10- anion was isolated as DMAH⁺ (DMA-2) and mixed inorganic cation (CsKNa-2) salts and characterized by XRD, HPLC-ICP-AES, EA and TGA techniques. X-ray analysis shows the presence of the {Ru(NO)}-group in the 6-membered ("equatorial") belt of the Sb-free hemisphere. The experimental findings were confirmed and interpreted by means of quantum chemical calculations.