Monomeric Complexes Research Articles

Uranium-Mediated Thiourea/Urea Conversion on Chelating Ligands

2,6-Dipicolinoylbis(N,N-dialkylthioureas) and H2LR2 react with uranyl salts and a supporting base (e.g., NEt3) under formation of monomeric or oligomeric complexes of the compositions [UO2(LR2)(solv)] (solv = donor solvents) or [{UO2(LR2)(µ2-OMe)}2]2–. In such complexes, the uranyl ions are commonly coordinated by the “hard” O,N,O or N,N,N donor atom sets of the central ligand unit and the lateral sulfur donor atoms remain uncoordinated. Their individual structures, however, depend on the reaction conditions, particularly on the equivalents of NEt3 used. An unprecedented, selective hydrolysis of the uranium-coordinating bis(thioureato) ligands results in an S/O donor atom exchange at exclusively one thiourea side-arm, when an excess of NEt3 is used. The resulting trimeric uranyl complexes are isolated in fair yields and have a composition of [(UO2)3(L2Et2)2(µ2–OR)(µ3-O)]–. H2L2Et2 represents the newly formed 2,6-dipicolinoyl(N,N-diethylthiourea)(N,N-diethylurea) and R = H, Me, or Et. {L2Et2}2– binds to the uranyl units via the pyridine ring, the dialkylurea arm, and the central carbonyl groups, while the thiourea unit remains uncoordinated. The central cores of the products consist of oxido-centered triangular {(UO2)3O}4+ units. The observed reactivity is metal-driven and corresponds mechanistically most probably to a classical metal-catalyzed hydrodesulfurization. The hydrolytic thiourea/urea conversion is only observed in the presence of uranyl ions. The products were isolated in crystalline form and studied spectroscopically and by X-ray diffraction. The experimental findings are accompanied by DFT calculations, which help to understand the energetic implications in such systems.

Efficacy and Safety of Rivaroxaban, Apixaban, and Edoxaban for Nonvalvular Atrial Fibrillation Based on Blood Coagulation Activity and Drug Plasma Concentration: SETtsu and North Osaka Multicenter Direct Oral AntiCoagulant (SET DOAC) Registry

Background: The therapeutic effects of oral anticoagulant drugs for nonvalvular atrial fibrillation (NVAF) suggest that the three factor Xa (FXa) inhibitors may have distinct safety profiles, though this is not yet fully conclusive. This study investigated the current dosing of rivaroxaban, apixaban, and edoxaban by monitoring drug plasma concentration (PC) and coagulation activity from the viewpoint of the safety. Methods and results: This multicenter clinical study monitored the drug PC and two coagulation biomarkers (fibrinogen and fibrin monomer complex [FMC]) at peak and trough timing in 268 outpatients taking rivaroxaban (n = 72), apixaban (n = 71), and edoxaban (n = 125) for NVAF. Doses were adjusted based on the dose-adjustment criteria of each drug. Referencing our previous study, peak drug PC remained below the cut-off level for predicting bleeding events except in eight patients (rivaroxaban, n = 3; apixaban, n = 2; edoxaban, n = 3) in whom bleeding events occurred. Among them, two (one each on rivaroxaban and edoxaban) had a peak drug PC below the cut-off level. Drug PCs widely varied from peak to trough, whereas FMC levels, reflecting thrombin activity, remained within the normal range (<6.1 µg/mL) regardless of PC variations. These results indicated that the anticoagulant effects of these drugs persisted throughout the day regardless of the drug PC levels, dosage, and dosing frequency. Regarding the change over time in peak PC, the elevation over time developed more in rivaroxaban (29/57; 50.9%, p < 0.05) than in edoxaban (32/101; 31.7%), and rivaroxaban tended to accumulate more than edoxaban. Conclusions: Although drug PC levels of once-daily FXa inhibitors widely varied from peak to trough, FMC levels were maintained within the normal range without daily variations. Rivaroxaban also tended to accumulate over time. The results indicate the low risk of thrombotic events with once-daily FXa inhibitors and its correspondence to the twice-daily regimen.

Synthesis, characterization and pH-sensitivity of AIE emitters obtained by RAFT polymerization of Pt(II) pincer complexes with polyvinylpyrrolidon

Two phosphine substituted Pt(II) pincer complexes (Pt1 and Pt2) containing NNC ligands: methyl 6-phenyl-[2,2′-bipyridine]-5-carboxylate (C1) and methyl 6-(4-fluorophenyl)-[2,2′-bipyridine]-5-carboxylate (C2), and diphenyl(vinyl)phosphine were obtained and characterized using mass spectrometry, NMR spectroscopy and XRD crystallography. The complexes are weakly phosphorescent in acetonitrile solution but display stronger emission in solid state, which is critically determined by the mode of molecular packing in crystal cell. Pt1 and Pt2 readily take part in RAFT copolymerization with polyvinylpyrrolidon to give amphiphilic P1 and P2 copolymers containing 6–7 and 3–5 units of the corresponding complexes in the polymeric chains. In DMFA, P2 forms nanospecies where the platinum chromophores aggregate to give strong emission red shift compared to the monomeric complexes due to Pt–Pt bonding in the aggregates. In aqueous solutions P1 and P2 form micelles with the hydrophobic core containing aggregated platinum chromophores emitting in the NIR spectral region. Hydrolysis of the ester group in the NNC ligand in P2 gives a water-soluble phosphorescent emitter with high lifetime sensitivity to pH in biologically relevant interval (pKa = 6.06).

Bimetallic Uranium Complexes with 2,6-Dipicolinoylbis(N,N-Dialkylthioureas).

2,6-Dipicolinoylbis(N,N-dialkylthioureas), H2LR, readily react with uranyl salts under formation of monomeric or dimeric complexes of the compositions [UO2(LR)(solv)] (solv = donor solvents such as H2O, MeOH or DMF) or [{UO2(LR)(µ-OMe)}2]2- (1). In such complexes, the uranyl ions are exclusively coordinated by the "hard" O,N,O or N,N,N donor atom sets of the central ligand unit and the lateral sulfur donor atoms do not participate in the coordination. Different conformations have been found for the dimeric anions. The bridging methanolato ligands and the four uncoordinated sulfur atoms can adopt different orientations with respect to the equatorial coordination spheres of the uranyl units. The presence of non-coordinated sulfur atoms offers the opportunity for the coordination of additional, preferably "soft" metal ions. Thus, reactions with [AuCl(PPh3)], lead acetate or acetates of transition metal ions such as Ni2+, Co2+, Fe2+, Mn2+, Zn2+, or Cd2+, were considered for the syntheses of bimetallic complexes. Various oligometallic complexes with uranyl units were prepared: [{UO2(LR)(μ-OMe)(Au(PPh3)}2] (2), [(UO2)3Pb2(LR)4(MeOH)2(μ-OMe)2] (3), [M{UO2(LR)(OAc)}2] (M= Zn, Ni, Co, Fe, Mn or Cd) (R = Et: 5, RR = morph: 6), or [(UO2)(NiI)2(LR)2] (7). The products were extensively studied spectroscopically and by X-ray diffraction.

Synthesis and Characterization of Monomeric Triarylbismuthine Oxide.

The synthesis and isolation of a bismuth-based analogue of the venerable triphenylphosphine oxide (Ph3PO) has remained a chimera to synthetic chemists for many years, due to its predicted high reactivity and instability. Through the hydrolysis of a cationic fluorotriarylbismuthonium(V) salt, we report here the isolation of unique hydroxytriarylbismuth(V) complexes, which served as precursor for the formation of the elusive monomeric triarylbismuthine oxide Dipp3Bi═O. Combined spectroscopic, crystallographic and computational studies provided insight into the bonding situation of the first monomeric triorganobismuth oxide complex. The Dipp3Bi═O and Mes3BiO·LiBArF complex exhibits O-atom transfer reactivity, an uncommon reactivity feature for Ar3Pn=O.

Synthesis and Characterization of Monomeric Triarylbismuthine Oxide

The synthesis and isolation of a bismuth‐based analogue of the venerable triphenylphosphine oxide (Ph3PO) has remained a chimera to synthetic chemists for many years, due to its predicted high reactivity and instability. Through the hydrolysis of a cationic fluorotriarylbismuthonium(V) salt, we report here the isolation of unique hydroxytriarylbismuth(V) complexes, which served as precursor for the formation of the elusive monomeric triarylbismuthine oxide Dipp3Bi═O. Combined spectroscopic, crystallographic and computational studies provided insight into the bonding situation of the first monomeric triorganobismuth oxide complex. The Dipp3Bi═O and Mes3BiO·LiBArF complex exhibits O‐atom transfer reactivity, an uncommon reactivity feature for Ar3Pn=O.

Room-Temperature Synthesis of a Fluorine-Functionalized Nanoporous Organic Polymer for Highly Efficient SF6 Adsorption and Separation.

Sulfur hexafluoride (SF6) is widely used in the power industry and significantly contributes to the greenhouse effect, necessitating the development of efficient materials for SF6 capture, particularly fluorine-containing materials. However, existing fluorine-containing materials often require complex monomers and high synthesis temperatures. Herein, we report the synthesis of a fluorine-functionalized carbazole-based nanoporous organic polymer (CNOP-7) at room temperature, using commercially available 4,4'-bis(9H-carbazole-9-yl)-1,1'-biphenyl and 1,1,1-trifluoroacetone. CNOP-7 contains 14.7% fluorine atoms and exhibits a high specific surface area of 1270 m2·g-1, demonstrating excellent SF6 adsorption and separation performance. The SF6/N2 selectivity of CNOP-7 reaches 107 at 273 K and 73 at 298 K. Furthermore, dynamic breakthrough experiments confirm that CNOP-7 can efficiently and repeatedly separate SF6 from SF6/N2 mixtures. Molecular simulations reveal the mechanism behind its efficient separation. This work offers fresh perspectives on the development and fabrication of adsorbents for efficient SF6 sequestration.

Novel Ag(I)‐based 1,2,4‐Oxadiazole Complexes: Synthesis, X‐Ray Crystal Structure, and Biological Evaluation as Anticancer Candidates

ABSTRACTThe 3,5‐diaryl‐1,2,4‐oxadiazole scaffolds 2 and 3 were synthesized and used as ligands to obtain three novel Ag(I) complexes 4–6. The structure of the Ag(I) complexes 4–6 has been confirmed by single crystal X‐ray diffraction. Complex 4 has the dinuclear formula [Ag(2)(NO3)]2. 5 and 6 are monomeric complexes having the formula [Ag(3)2(NO3)] and [Ag(3)2]ClO4, respectively. In vitro, trypsin, ALDH2, and iNOS inhibition activities were assessed for the free ligands and their Ag(I) complexes. Interestingly, Ag(I) complexes 4–6 revealed more prominent trypsin inhibitory activity than the ligands 2 and 3. The oxadiazole derivative 3 and its Ag(I) complex (6) showed significant ALDH2 inhibition (45% and 55%, respectively). Complex 6 (IC50 = 35.61 μM) surpassed its 1,2,4‐oxadiazole ligand 3 (IC50 = 88 μM) and evidenced the most prominent ALDH2 inhibitory activity. The oxadiazole derivative 3 and its corresponding Ag(I) complexes 5 and 6 showed significant iNOS inhibition (77.77%, 84.12%, and 84.15%, respectively). With IC50 values of 18.13, 18.15, and 13.96 μM, respectively, complex 6 is the most potent against iNOS, surpassing the reference standard.

Insight into the Structural Optimization and Electrical Conductivity of NiII/MnII Bipyridine–Dicyanamide Complexes

AbstractTwo monomeric octahedral complexes {[Ni(N(CN)2)2(bpy)2]2·H2O (1) and [Mn(N(CN)2)2(bpy)2] (2) where bpy = 2,2′‐bipyridine} were synthesized and characterized by single crystal X‐ray diffraction, elemental analysis, UV–visible, and IR spectra. The geometry optimization through DFT measurements predicts that both the complexes have similar monomeric structures with hexa‐coordinated metal centers having a couple of bpy and mononegative dca anions and thus satisfying the octahedral geometry. Moreover, it is found that the HOMO–LUMO energy gaps are ΔE = 4.981 and 5.563 eV for complexes 1 and 2, respectively, which are responsible for the stabilization of the complex formation. The calculated absorption bands are located at 304 and 235 nm, which are in excellent agreement with the experimental result. Moreover, the DFT study of the electronic spectra of both complexes shows that the calculated absorption bands are in well agreement with the experimental results. In the electrical studies, direct current (dc) measurements on the copper/complex (1 or 2)/copper structure confirm a definite development in the device current with applied bias. Complex 1 has shown better electrical conductance compared to complex 2 based on the reduction of device resistance.

Reconstitution of Arp2/3-nucleated actin assembly with proteins CP, V-1, and CARMIL.

Actin polymerization is often associated with membrane proteins containing capping-protein-interacting (CPI) motifs, such as capping protein, Arp2/3, myosin I linker (CARMIL), CD2AP, and WASHCAP/Fam21. CPI motifs bind directly to actin-capping protein (CP), and this interaction weakens the binding of CP to barbed ends of actin filaments, lessening the ability of CP to functionally cap those ends. The protein V-1/myotrophin binds to the F-actin-binding site on CP and sterically blocks CP from binding barbed ends. CPI-motif proteins also weaken the binding between V-1 and CP, which decreases the inhibitory effects of V-1, thereby freeing CP to cap barbed ends. Here, we address the question of whether CPI-motif proteins on a surface analogous to a membrane lead to net activation or inhibition of actin assembly nucleated by Arp2/3 complex. Using reconstitution with purified components, we discovered that CARMIL at the surface promotes and enhances actin assembly, countering the inhibitory effects of V-1 and thus activating CP. The reconstitution involves the presence of an Arp2/3 activator on the surface, along with Arp2/3 complex, V-1, CP, profilin, and actin monomers in solution, recreating key features of cell physiology.

Anticancer behavior of cyclometallated iridium(III)-tributyltin(IV) carboxylate schiff base complexes with aggregation-induced emission

Cyclometallated iridium(III) and organotin(IV) carboxylate complexes have shown potential application value in the field of anticancer. However, the widespread aggregation-caused quenching (ACQ) effect of these complexes is not conducive to the exploration of their targeting and anticancer mechanism, and the idea of aggregation-induced emission (AIE) effect can effectively solve this problem. Then, AIE-activated cyclometallated iridium(III)-tributyltin(IV) carboxylate Schiff base complexes were designed and prepared in this study. Complexes exhibited AIE effect in highly concentrated solution or aggregative state, which facilitated the investigation of subcellular tissue targeting (mitochondria) and cell morphology. Compared with cyclometallated iridium(III) complex and tributyltin(IV) carboxylate monomers, these complexes showed the better in-vitro anti-proliferative activity toward A549 cells, confirming the favorable synergistic anticancer activity. Even for A549/DDP (cisplatin-resistance) cells, these complexes also exhibited the better activity. In addition, complexes showed a mitochondrial apoptotic pathway. Therefore, cyclometallated iridium(III)-tributyltin(IV) carboxylate Schiff base complexes can be used as the potential substitutes for platinum-based drugs and gain further application.

Cryo-EM structures of the Spo11 core complex bound to DNA.

DNA double-strand breaks that initiate meiotic recombination are formed by the topoisomerase-relative enzyme Spo11, supported by conserved auxiliary factors. Because high-resolution structural data have not been available, many questions remain about the architecture of Spo11 and its partners and how they engage with DNA. We report cryo-electron microscopy structures at up to 3.3-Å resolution of DNA-bound core complexes of Saccharomyces cerevisiae Spo11 with Rec102, Rec104 and Ski8. In these structures, monomeric core complexes make extensive contacts with the DNA backbone and with the recessed 3'-OH and first 5' overhanging nucleotide, establishing the molecular determinants of DNA end-binding specificity and providing insight into DNA cleavage preferences in vivo. The structures of individual subunits and their interfaces, supported by functional data in yeast, provide insight into the role of metal ions in DNA binding and uncover unexpected structural variation in homologs of the Top6BL component of the core complex.

Structural Basis for Dimerization and Activation of UvrD-family Helicases.

UvrD-family helicases are superfamily 1A motor proteins that function during DNA replication, recombination, repair, and transcription. UvrD family monomers translocate along single stranded (ss) DNA but need to be activated by dimerization to unwind DNA in the absence of force or accessory factors. However, prior structural studies have only revealed monomeric complexes. Here, we report the first structures of a dimeric UvrD-family helicase, Mycobacterium tuberculosis UvrD1, both free and bound to a DNA junction. In each structure, the dimer interface occurs between the 2B subdomains of each subunit. The apo UvrD1 dimer is observed in symmetric compact and extended forms indicating substantial flexibility. This symmetry is broken in the DNA-bound dimer complex with leading and trailing subunits adopting distinct conformations. Biochemical experiments reveal that the E. coli UvrD dimer shares the same 2B-2B interface. In contrast to the dimeric structures, an inactive, auto-inhibited UvrD1 DNA-bound monomer structure reveals 2B subdomain-DNA contacts that are likely inhibitory. The major re-orientation of the 2B subdomains that occurs upon UvrD1 dimerization prevents these duplex DNA interactions, thus relieving the auto-inhibition. These structures reveal that the 2B subdomain serves a major regulatory role rather than participating directly in DNA unwinding.

Synthesis and Characterization of Copper(II) and Nickel(II) Complexes with 3-(Morpholin-4-yl)propane-2,3-dione 4-Allylthiosemicarbazone Exploring the Antibacterial, Antifungal and Antiradical Properties.

The eleven new copper(II) and nickel(II) coordination compounds [Cu(L)Br]2 (1), [Cu(L)Cl] (2), [Cu(L)NO3] (3), [Ni(L)Cl] (4), [Ni(HL)2](NO3)2 (5), and [Cu(A)(L)]NO3, where A is 1,10-phenanthroline (6), 2,2'-bipyridine (7), 3,4-dimethylpyridine (8), 3-methylpyridine (9), pyridine (10) and imidazole (11) were synthesized with 3-(morpholin-4-yl)propane-2,3-dione 4-allylthiosemicarbazone (HL). The new thiosemicarbazone was characterized by NMR and FTIR spectroscopy. All the coordination compounds were characterized by elemental analysis and FTIR spectroscopy. Also, the crystal structures of HL and complexes 1, 6, 7, and 11 were determined using single-crystal X-ray diffraction analysis. Complex 1 has a dimeric molecular structure with two bromide bridging ligands, while 6, 7, and 11 are ionic compounds and comprise monomeric complex cations. The studied complexes manifest antibacterial and antifungal activities and also have an antiradical activity that, in many cases, surpasses the activity of trolox, which is used as a standard antioxidant in medicine. Copper complexes 1-3 have very weak antiradical properties (IC50 > 100 µM), but nickel complexes 4-5 are strong antiradicals with IC50 values lower than that of trolox. The mixed ligand copper complexes with additional ligand of N-heteroaromatic base are superior to complexes without these additional ligands. They are 1.4-5 times more active than trolox.

ESR, UV–vis–NIR and FTIR spectroscopic characterization of charge carriers in copper salen polymeric complexes

In this work, we present spectroscopic investigation of charge carriers in copper(II) salen-type polymeric complexes. The polymers comprising monomeric complexes of copper(II) ion with N2O2 Schiff base ligands are analyzed to understand the influence of the paramagnetic metal center and electron-donating substituents in the ligand on the spectroscopic properties of oxidized polymers. Potential-driven structural changes in the polymeric complexes were monitored using electron spin resonance (ESR), ultraviolet−visible − near infrared (UV−vis − NIR) and Fourier Transform Infrared (FTIR) spectroelectrochemistry. By EPR spectroelectrochemistry, we gained insight into the magnetic properties of charge carriers formed during the initial and deep oxidation of the polymers as well as the interactions between the Cu(II)–ligand spins and ligand–ligand ones. By FTIR spectroelectrochemistry, it has been shown that the charge in the low doped polymers is delocalized within the whole repeat unit.

Rare earth mixed sandwich complexes with tetraalkylphospholide and cyclooctatetraenide ligands

A series of rare earth (mono)phospholide mixed sandwich complexes of the general form [M(PC4R4)(COT)(THF)n] (M = Sc, Y, La, Lu; R = Me, Et; COT = cyclooctatetraenide, {C8H8}2–; n = 0 to 2) have been isolated by the treatment of iodide precursors, [M(COT)(I)(THF)n], (1M, M = Sc, Y, Lu, n = 2; M = La, n = 3) with potassium phospholide salts, [K(PC4R4)]n (R = Me, Et). The solid-state molecular structures and speciation of these sandwich complexes depends upon both the ionic radius of the rare earth metal, along with small steric and solubility differences which arise between the two per-alkylated phospholide ligands. The smaller {PC4Me4} ligand gave monomeric Lewis-base free [M(C8H8)(PC4Me4)] (2M, M = Sc, Lu) with smaller rare earths Sc(III) and Lu(III), but moving to larger ions Y(III) and La(III), the products were poorly soluble and could only be isolated as THF-adducts, [Y(C8H8)(PC4Me4)(THF)] (3) and [La(C8H8)(PC4Me4)(THF)2] (4). The slightly increased steric demands of {PC4Et4} gave monomeric Lewis-base free complexes for Sc(III), Lu(III), and Y(III) in [M(C8H8)(PC4Et4)] (5M, M = Sc, Y, Lu), whereas for La(III) a dimeric complex was isolated, [La(C8H8)(µ-PC4Et4)]2 (6). We also report the synthesis and molecular structures of 1Sc and 1Lu, as well as [LuI3(THF)3] (7) for the first time. All complexes were characterised by single crystal X-ray diffraction, multi-nuclear NMR, UV-Vis-NIR and ATR-IR spectroscopies in addition to elemental analysis.

Degradation of a Wholly Aromatic Main-Chain Thermotropic Liquid-Crystalline Polymer Mediated by Superbases.

Plastic circular economy needs to be established to solve environmental issues related to plastic waste. Superengineering plastics such as liquid-crystalline (LC) polymers exhibit excellent thermal and mechanical properties, resulting in poor degradability in natural environment. Herein, we report the degradation of a wholly aromatic thermotropic LC polyester, poly(4-hydroxybenzoic acid-co-6-hydroxy-2-naphthoic acid) (Vectra) mediated by superbases. Methanolysis and hydrolysis of Vectra yield its monomeric compounds, 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and their methyl esters. Among several transesterification catalysts explored, 1,5,7-triazabicylco[4.4.0]dec-5-ene (TBD) is the most suitable for the methanolysis of Vectra. The complete degradation of Vectra is achieved under reflux. The degradation proceeds heterogeneously via a surface erosion mechanism, preferentially starting from less chain-packed regions. Model reactions using aryl arylates reveal that monomeric compound-superbase complexes could mediate the cleavage of the ester bonds in both homogeneous and heterogeneous systems. The ester bonds of Vectra have inherent poor reactivity and are protected by oriented robust structures of the polymer. Nevertheless, the superbases enable the degradation of Vectra via the cleavage of the ester bonds by methanol. These outcomes open the way for recycling high-performance plastics as well as demonstrate the feasibility of recovering precious aromatic compounds from plastic waste as aromatic feedstock.

Structural and biochemical characterization of cauliflower mosaic virus reverse transcriptase

Reverse transcriptases (RTs) are enzymes with DNA polymerase and RNase H activities. They convert single-stranded RNA into double-stranded DNA and are key enzymes for the replication of retroviruses and retroelements. Caulimoviridae is a major family of plant-infecting viruses. Caulimoviruses have a circular dsDNA genome that is replicated by reverse transcription, but in contrast to retroviruses, they lack integrase. Caulimoviruses are related to Ty3 retroelements. Ty3 RT has been extensively studied structurally and biochemically, but corresponding information for caulimoviral RTs is unavailable. In the present study, we report the first crystal structure of cauliflower mosaic virus (CaMV) RT in complex with a duplex made of RNA and DNA strands (RNA/DNA hybrid). CaMV RT forms a monomeric complex with the hybrid, unlike Ty3 RT, which does so as a dimer. Results of the RNA-dependent DNA polymerase and DNA-dependent DNA polymerase activity assays showed that individual CaMV RT molecules are able to perform full polymerase functions. However, our analyses showed that an additional CaMV RT molecule needs to transiently associate with a polymerase-competent RT molecule to execute RNase H cuts of the RNA strand. Collectively, our results provide details into the structure and function of CaMV RT and describe how the enzyme compares to other related RTs.

New Semicarbazone-Schiff Base Coordination; Synthesis, Characterization and Biological Evaluation

The synthesis and characterisation of a new azo Schiff base ligand generated from a semicarbazone moiety are reported in this study, in addition to its metal complexes. The title ligand, (E)-2-((2-hydroxy-3-((E)-(2-nitrophenyl) diazenyl) naphthalen-1-yl) methylene) hydrazine-1-carboxamide (HL), was synthesised by reacting ((E)-2-hydroxy-3-((2-nitrophenyl) diazenyl)-1-naphthaldehyde) with semicarbazidein a 1:1 molar ratio. Afterward, the interplay between HL and other metal ions (CrШ, MnII, CoII, NiII and CuII) produced monomeric coordination complexes in a 1:1 ligand-to-metal ratio. A range of spectroscopic and analytical techniques, such as magnetic susceptibility, conductance tests, 1H and 13C-NMR, FT-IR, electronic and mass spectroscopy, and elemental microanalysis, were used to extensively characterize these complexes. The synthesis of coordination compounds with six-coordinate geometries was verified by the characterization data. The study also assessed the antimicrobial efficacy of the synthesised compounds against various bacterial and fungal species, revealing that After the complex formed, the ligand's antimicrobial activity was greatly increased.

The galactomannan-EGCG physical complex: Effect of branching degree and molecular weight on structural and physiological properties

Polysaccharides and polyphenols are bioactive components that co-exist in many plant foods. Their binary interaction in terms of the structure-function relationships, however, has not been well clarified. This study elucidated the correlation between the structural and physiological properties of galactomannan (GM) -catechin monomer complexes and GM with different branching or molecular weight (Mw). Results indicated that locus bean gum with lower branching degree (Gal/Man is 0.259) bound more readily to EGCG with adsorption rate of 19.42 %. EGCG and ECG containing galloyl groups were more inclined to form hydrogen bonds with GMs, significantly improving the adsorption by GMs. The introduction of EGCG could enhance the antioxidant activity and starch digestion inhibition of GM, which positively correlated with the adsorption capacity of EGCG. The guar gum (GG) with higher Mw (7384.3 kDa) could transport 71.51 % EGCG into the colon, while the retention rate of EGCG reaching the colon alone was only 46.33 %. Conversely, GM-EGCG complex with lower Mw (6.9 kDa) could be readily utilized by gut microbiota, and increased production of short-chain fatty acids (SCFAs). This study elucidated the structure-properties relationship of GM-EGCG complexes, and provide a new idea for the development and precision nutrition of polysaccharides-polyphenol complexes fortified functional foods.