The Impact of Crystal Packing and Aurophilic Interactions on the Luminescence Properties in Polymorphs and Solvate of Aroylacetylide–Gold(I) Complexes

The influence of the chemical substitution, crystal packing, and aurophilic interactions of the gold(I) acetylide complexes of the type (ArCOC≡C)_nAuPEt₃ (n=1,2) on their luminescent properties were examined. All described complexes undergo ligand scrambling in solution, which results in the formation of stable, easily isolated crystals that contain [ArCO(C≡C)_n]₂Au⁻(Et₃P)₂Au⁺ homoleptic species. In particular, we observed that the (benzoylacetylide)gold(I) complex yields three crystal forms with strikingly different luminescence properties. We monitored the conversion pathway for these forms: an orange luminescent form of homoleptic complex upon drying undergoes spontaneous transformation to bright green fluorescent form and finally to the weakly blue emissive one. In addition, we report a rare example of a helical arrangement of Au⋅Au⋅Au chains that are observed for the first time in acetylide gold(I) complexes in the case of heteroleptic (benzoylacetylide)gold(I) complex. This is a very rare case in which crystal structures and ensuing electronic properties of the heteroleptic and Au^I complexes could be directly compared.     

Carbon–Fluorine Reductive Elimination from Nickel(III) Complexes

We report a C−F reductive elimination from a characterized first-row aryl metal fluoride complex. Reductive elimination from the presented nickel(III) complexes is faster than C−F bond formation from any other characterized aryl metal fluoride complex.     

Studies on Alkyl?Nitrogen Bond Formation via Reductive Elimination from Monomeric Palladium Complexes in High Oxidation State

Oxidation of a series of defined palladium(II) complexes bearing a bidentate ligand, and a methyl and an amidato substituent was carried out with the aim to gain a better understanding of the inherent requirements for C? N bond‐formation from Pd complexes in high oxidation state. This work clarified the role of the individual nitrogen sources and has important implication for alkyl? nitrogen bond‐forming reactions catalyzed by Pd.     

Reductive Elimination or C−C Bond Activation with Model Ni,Pd, Pt Complexes? A High-Accuracy Comparative Computational Analysis of Reactivity

The development of Pd- and Ni-catalyzed reactions for C−C bond formation is one of the primary driving forces in modern organic synthesis and the fine chemical industry. However, understanding the role of conformational mobility in reaction mechanisms is a long-standing challenge. We highlight the effect of a multirotamer (multiconformer) system on the effective Gibbs free energy of activation in the key C−C coupling process and promote the use of a simplified version of multiconformer transition state theory that is straightforward to apply. Multivariate regression helped to quantitatively map the effect of coupled organic substituents (their structural and electronic parameters), as well as to determine the relative activity of metals. We provide computational evidence for solvent control of the equilibrium in RE/C−C-bond activation for some model complexes. We also demonstrate that Ni complexes, being unique in the catalysis of sp³-sp³ couplings, can be more challenging for machine learning and computational chemistry. The modeling was performed at an exceptionally high level, DLPNO-CCSD(T)/CBS//RIJCOSX-PBE0-D4/def2-TZVP. The Conclusions section contains an infographic summarizing the key findings related to the fields of cross-coupling catalysis, machine learning in catalysis, and computational chemistry.     

Studies on Thermodynamics of Micellization and Solvophobic Interactions of Novel Surfactant–Cr(III) Complexes in Non-aqueous Solvents

The critical micelle concentration (CMC) of surfactant–Cr(III)–dodecylamine complexes of the type cis-α-[Cr(trien)(C₁₂H₂₅NH₂)X]²⁺ (where trien = triethylenetetramine; X = F⁻, Cl⁻, Br⁻) has been studied in n-alcohol and in formamide at different temperatures, by electrical conductivity measurements. From the CMC values as a function of temperature, various thermodynamic properties have been evaluated: standard Gibbs energy changes (Δ_mic G ⁰), standard enthalpy changes (Δ_mic H ⁰) and standard entropy changes (Δ_mic S ⁰) for micellization. Critical micelle concentrations have also been measured as a function of the percentage composition of alcohol added. The solvent composition dependences of these thermodynamic parameters were determined. It is suggested that alcohol addition leads to an increase in formamide penetration into the micellar interface that depends on the alcohol’s chain length. The results are discussed in terms of an increased hydrophobic effect, dielectric constant of the medium, the chain length of the alcohols, and the surfactant in the solvent mixture.     

Impact on Morphological Characterization and Emulsion Stability of Lactoferrin–Beet Pectin Electrostatic Complexes

Interfacial protein–polysaccharide complexes can be utilized in emulsion-based delivery system and contained functional component or medical ingredient. In the present work, the interaction of lactoferrin (LF, 0.2 wt%) with beet pectin (BP, 0–0.15 wt%) was researched in aqueous solutions at different pH (2–9) and ionic strength (0–800 mM) to provide the information about properties of complexes. A simulative environment was created to explore the optimal concentration of BP to formulate LF-coated stabilized emulsion and how the emulsion responded to the changing environmental pH (2–9) and ionic strength (0–500 mM). Particle size, particle distribution index, zeta-potential, turbidity, Turbiscan stability index,, and peak thickness were used to characterize the physical stability of emulsions. The confocal laser scanning microscopy was used to derive the microscopy images of droplets. The results indicated that 0.4 wt% was the optimal concentration to formulate emulsions, and the LF-BP-coated bilayer emulsion has a preferable stability in more extensive range than the pure LF-stabilized emulsions under the environmental stresses through electrostatic interactions. The results of this study will play an important role in facilitating the utilization of LF-BP complexes as an emulsifier in the development of incorporating functional component or medical ingredient into commercial products.     

Impact of Group 10 Metals on the Solvent-Induced Disproportionation of o-Semiquinonato Complexes

The oxidation of [M^II(3,5-DTBCat)(DTBbpy)] (M=Ni ( [Ni] ), Pd ( [Pd] ), and Pt ( [Pt] ); 3,5-DTBCat=3,5-di-tert-butylcatecholato; DTBbpy=4,4′-di-tert-butyl-2,2′-bipyridine) afforded the dimeric {[Ni^II(3,5-DTBSQ)(DTBbpy)](PF₆)}₂ ( {[Ni](PF₆)}₂ ; 3,5-DTBSQ=3,5-di-tert-butylsemiquinonato) and monomeric semiquinonato (SQ) complexes [M^II(3,5-DTBSQ)(DTBbpy)](PF₆) (M=Pd ( [Pd](PF₆) ) and Pt ( [Pt](PF₆) )). The negative solvatochromic properties of the SQ complexes allowed us to estimate the relative order of their dipole moments: [Pd](PF₆) > [Pt](PF₆) > {[Ni](PF₆)}₂ . The complexes [Pd](PF₆) and [Pt](PF₆) adopt monomeric structures and are stable in CH₂Cl₂ and toluene, whereas they gradually disproportionate at room temperature to [M] and 3,5-di-tert-butylbenzoquinone (3,5-DTBBQ) in polar solvents such as THF, MeOH, EtOH, DMF, or DMSO. The results of spectroscopic studies suggested that the oxidized nickel complex adopts a monomeric structure ( [Ni](PF₆) ) in CH₂Cl₂, but a dimeric structure ( {[Ni](PF₆)}₂ ) in the other investigated solvents. In polar solvents, {[Ni](PF₆)}₂ may disproportionate to [Ni] and 3,5-DTBBQ at 323 K, thereby demonstrating a significant solvent- and metal-dependence in temperature. The relative activities of {[Ni](PF₆)}₂ and [M](PF₆) toward disproportionation are related to the electrochemically estimated K_dis values in CH₂Cl₂ and DMF. The present work demonstrates that solvent polarity and the dipole moments of the SQ complexes promote disproportionation, which can be controlled by a judicious choice of the metal ion, solvent, and temperature.     

Probiotics—Interactions with Bile Acids and Impact on Cholesterol Metabolism

The use of probiotics, alone or in interaction with bile acids, is a modern strategy in the prevention and treatment of hypercholesterolemia. Numerous mechanisms for hypocholesterolemic effect of probiotics have been hypothesized, based mostly on in vitro evidence. Interaction with bile acids through reaction of deconjugation catalyzed by bile salt hydrolase enzymes (BSH) is considered as the main mechanism of cholesterol-lowering effects of probiotic bacteria, but it has been reported that microbial BSH activity could be potentially detrimental to the human host. There are several approaches for prevention of possible side effects associated with BSH activity, which at the same time increase the viability of probiotics in the intestines and also in food matrices. The aim of our study was to summarize present knowledge of probiotics??bile acids interactions, with special reference to cholesterol-lowering mechanisms of probiotics, and to report novel biotechnological approaches for increasing the pharmacological benefits of probiotics.     

Impact of the Aliphatic Dicarboxylate Chain of Novel Dinuclear Palladium(Ⅱ) Complexes: Synthesis and Biological Evaluation

Five dinuclear palladium(II) complexes with HOOC(CH₂)_nCOOH (n=2–6) and 2,2′‐bipyridine ligands were synthesigned by a reaction with K₂PdCl₄. To prepare such complexes with different aliphatic dicarboxylate chain lengths was in an attempt to correlate this length factor, which influences the biological activity of the complexes, with fluorescence spectra, DNA cleavage and cytotoxic activity. The results indicate that the complexes bind to fish sperm DNA (FS‐DNA) in an intercalative mode via fluorescence spectra, and the five complexes show different cleavage of supercoiled DNA, and then a cytotoxicity assay of these dinuclear palladium(II) complexes on human tumor cell lines was performed. In most of the cell lines, complex 5 (n=6) and 4 (n=5) showed much higher cytotoxicity than cis‐platin. On the other hand, complex 3 (n=4) was found to be moderately active, and complex 1 (n=2), complex 2 (n=3) were found only marginally cytotoxic. Implications of these findings were discussed from a structure‐activity relationship.     

Tandem Pd/C‐Catalyzed Reductive Coupling and Dehalogenation of Benzylic Halides

High‐yield reductive homocoupling of benzotrichloride and benzal chloride followed by consecutive reductive dechlorination to 1,2‐dichlorostilbene and stilbene is effected in the presence of sodium formate as the reducing agent and Pd/C catalysts.     

π-Electronic Charge-Transfer Interactions in Inclusion Complexes of Fullerenens with Cyclic Dimers of Metalloporphyrins

Spectroscopic and voltammetric analyses on inclusion complexes of a fullerene such as C₆₀ with a cyclic dimer of a free-base porphyrin (1-M; M = 2H) and its metal complexes (M = Co, Ag, and Zn) showed that a charge-transfer interaction is partly responsible for the complexation.     

Investigation on the Thermostability of Germanium and Elimination of Chloride and Sulfate.Interference on Germanium in Graphite Furnace Atomic Absorption Spectrometry

TheadvantageofdeterminationoftraceGebyGF.AASisthatonlyafewmicrolitersofsampleisused.Butthematrixinterference,especiallychlorideionandsulfateionisveryseriousl.Sothereisanimportantsubjectforfurtherinvestigatingtoeliminatetheseinterferences.Nitricacidisanoxidant.ThetetravalentGeisstabilizedowingtoitsoxidation.ThemagnitudeoftheGesignalvarieswiththeconcentrationofnitricacidandthemaximumoftheGesignalisobservedwith0.6mol/Lnitricacid.Theactionofsomenitratesissimilarbuttheconcentrationofvariousnit…     

Reconciling Electrostatic and n→π* Orbital Contributions in Carbonyl Interactions

Interactions between carbonyl groups are prevalent in protein structures. Earlier investigations identified dominant electrostatic dipolar interactions, while others implicated lone pair n→π* orbital delocalisation. Here these observations are reconciled. A combined experimental and computational approach confirmed the dominance of electrostatic interactions in a new series of synthetic molecular balances, while also highlighting the distance-dependent observation of inductive polarisation manifested by n→π* orbital delocalisation. Computational fiSAPT energy decomposition and natural bonding orbital analyses correlated with experimental data to reveal the contexts in which short-range inductive polarisation augment electrostatic dipolar interactions. Thus, we provide a framework for reconciling the context dependency of the dominance of electrostatic interactions and the occurrence of n→π* orbital delocalisation in C=O⋅⋅⋅C=O interactions.     

Synthesis and Biological Evaluation of Pyranone Analogues of Territrem B

As a highly selective and potent acetylcholinesterase(AChE)inhibitor,territrem B wasisolated by Ling et al.from a strain of Aspergillus terreus in19791,2.Zhao et alreported mimic preparation of territrem B analogues from triterpenoids and found thatthe enone moiety and aromatic ring played important roles in their syntheticcompounds3,4.To further detect essential pharmacophors for AChE inhibitors,wesimplified the A/B ring system of territrem B and synthesized a number of pyranonepharmacop…     

Weak Interactions Involving Fluorine in Suppramolecular Assemblies of Cu(Ⅱ)Complexes

Syntheses and X‐ray structural characterizations of two new Cu(II) complexes Cu(tfbz)₂(Htfbz)₂(phen) ( 1 ) (Htfbz=2,4,5‐trifluorobenzoic acid, phen=1,10‐phenanthroline) and [Cu(pfbz)₂(phen)]₂(Hpfbz)₂ ( 2 ) (Hpfbz=pentafluorobenzoic acid) are reported. The first complex crystallizes in the monoclinic space group C2/c with the crystal cell parameters a=1.9903(4) nm, b=1.3688(3) nm, c=1.3623(3) nm, β=97.90(3)°, V=3.6762(13) nm³ and Z=4. The second complex crystallizes in the triclinic space group P‐1 with the crystal cell parameters a=1.7965(4) Å, b=1.9236(2) Å, c=2.0916(2) Å, α=110.156(2) °, β=105.040(3) °, γ=98.123(3) °, V=6.3372(17) nm³ and Z=4. The crystallographic analyses revealed that F···H–C hydrogen bonds in both complexes lead to formation of infinite three‐dimensional supramolecular networks. A large number of F···F interactions in complex 2 ensure the stability of intricate crystal structure.     

New Silver(I) Complexes of Pyridyl Dithioether Ligands with Ag–Ag Interactions: Effects of Anions and Ligand Spacers on the Framework Formations of Complexes

Three new silver(I) complexes existing Ag–Ag interactions, a trinuclear cluster complex [Ag₃(L ¹)₂(NO₃)₂](NO₃) 1, a dinuclear complex [Ag₂(L ¹)₂](PF₆)₂ 2 and a one-dimensional chain complex [Ag₂ L ²(NO₃)₂] 3, where L ¹ and L ² are two structurally related pyridyl dithioether ligands, bis(2-pyridylthio)methane (L ¹) and 1,3-bis(2-pyridylthio)-propane (L ²), have been synthesized and their structures were determined by single-crystal X-ray diffraction analysis. The striking structural differences of 1 and 2 suggest that counter anions have a profound effect upon the framework formations of silver complexes with pyridyl dithioether ligands, and the differences of 1 and 3 indicate that the subtle changes of the space groups have great influence on the coordination modes of the terminal pyridylsulfanyl groups and the geometries of Ag^I ion and therefore greatly influence the structures of their complexes. The weak AgO interactions in the trinuclear complex 1 and the one-dimensinoal chain complex 3 extend them into quasi two-dimensional networks, and the AgS weak interactions in the dinuclear complex 2 into one-dimensinoal chains, and such weak interactions further stabilized these complexes.     

Electroreduction of Pd(II) Complexes with α-Alanine on a Palladium Electrode

The kinetics of electroreduction of Pd(II) complexes with -alanine, Pd(ala)₂, is studied on a rotating Pd disk electrode in solutions of pH 8–13 containing large excess of -alanine and various supporting electrolytes (NaF, Na₂SO₄, NaClO₄). On a Pd electrode, complexes Pd(ala)₂ undergo reduction at potentials much more negative than on an Hg electrode. This is attributed to the chemisorption of water on the Pd electrode, which hampers adsorption of Pd(ala)₂ that take part in the slow electrochemical stage. As with the Hg electrode, perchlorate ions hinder the Pd(ala)₂ reduction on a Pd electrode. Studying adsorption of Pd(ala)₂ on a Pd electrode is hampered by parallel processes of hydrogen adsorption and absorption.     

Labile Interactions and Inert Entities in Supramolecular Chemistry—the Identification of Recognition Mechanisms for Macrobicyclic Amine Complexes

Consideration of crystallographic data concerning metal complexes of hexa-azabicyclo[6.6.6]icosane, “sarcophagine”, and various derivatives provides evidence for the importance of hydrogen-bonding, labile metal ion coordination, aliphatic- and aromatic-group interactions in determining the lattice structures. These “cage amine” complexes not only involve different metal ions, almost all rendered kinetically inert towards substitution by their complexation, but they can be obtained in conformationally locked forms and with a wide variety of substituents, so that they have considerable potential as supramolecular tectons.     

Porous Solids of Divalent Metal Complexes Assembled Through Hydrogen Bonding and π–π Stacking Interactions

The compound N, N-di(6-methyl-2-pyridyl)formamidine (HDMepyF) has been exploited in preparation of porous materials of divalent metal complexes of the formulae M(HDMepyF)₂(NO₃)₂ (M=Cd, 1; Co, 2; Ni, 3) and M(HDMepyF)₂X₂ (M=Mn, X=Cl, 4; M=Mn, X=Br, 5; M=Ni, X=Cl, 6; M=Ni, X=Br, 7). Their structures have been determined by X-ray crystallography. Each metal center of these complexes is approximately octahedrally coordinated by four nitrogen and two halogen or oxygen donor atoms. Complexes 1– 5 and 7 self-assemble through similar hydrogen bonding motifs which involve the C–HsX (X=Cl, Br or O) hydrogen bondings and – stacking interactions between the HDMepyF ligand and the X atoms to form porous structures.