Precise analysis of thyroxine enantiomers in pharmaceutical formulation by mobility difference based on cyclodextrin

Identification and determination of chiral pharmaceutical residues is still a challenging analytical puzzle. In this work, a simple, rapid, and effective method for chiral D/L-tetraiodothyronine (T4) separation and quantitative was developed based on host–guest recognition using ion mobility spectrometry-mass spectrometry (IMS-MS). The D/L-T4 enantiomers were mobility separated by their diastereomeric complexes through mixing with cyclodextrin (CD) and metal ions. D/L-T4 was first separated by complexing with host molecule (α-, β-, γ-CD), observing weak peak-to-peak resolution (R_p-p) by the formed binary complex [CD + D/L-T4-H]⁺, and the R_p-p decreased with the CD size increasing. However, the separation effect of D/L-T4 was much improved with the addition of divalent metal ions (G²⁺) by the formed ternary complex [CD + D/L-T4 + G]²⁺. In comparison, α-CD related complexes can possess the best separation effect for D/L-T4 in most cases. Considering the high selectivity, non-toxic, and chemically stable of β-CD, [β-CD + D/L-T4 + Ca]²⁺ was selected for D/L-T4 analysis (R_P-P = 0.764). Whereafter, chemical theoretical conformations for [β-CD + D/L-T4 + H]⁺ and [β-CD + D/L-T4 + Ca]²⁺ were optimized, discovering similar micro-interaction modes between [β-CD + D-T4 + H]⁺ and [β-CD + L-T4 + H]⁺; while with the addition of Ca²⁺, significantly different interaction modes were observed between [β-CD + D-T4 + Ca]²⁺ and [β-CD + L-T4 + Ca]²⁺. And theoretical collision cross section (CCS) trends for the complexes were consistent with that of the experimental results. Additionally, calibration curves were linear within 1.00 to 10⁴ ng mL^?1 with coefficient (R² > 0.99), gaining the limit of detection (LODs) calculation of 0.11 ng mL^?1, and the detection range between D-T4 and L-T4 of 45.6:1 to 1:59.8. Finally, the method was applied for D/L-T4 detection in Levothyroxine tablets, the detection content has good consistency on drug labeling. Because the proposed method exhibited good analytical performance in terms of speed, selectivity, sensitivity, and reproducibility of the measurements, that can be a promising strategy for effective D/L-T4 detection in pharmaceutical industries or other practical samples.     

Rare-earth metal derivatives supported by aminophenoxy ligand: Synthesis,characterization and catalytic performance in lactide polymerization

A library of rare-earth metal derivatives supported by an aminophenoxy ligand was prepared and their catalytic performance in lactide polymerization was investigated. It was found that the synthetic strategy had a profound effect on the formation of aminophenoxy rare-earth metal complexes. Amine elimination between Ln[N(SiMe₃)₂]₃(μ-Cl)Li(THF)₃ (Ln = Yb, Y) and 1 equiv. of the aminophenol [HONH] ([HONH] = ο-OCH₃-C₆H₄NHCH₂(3,5-^tBu₂-C₆H₂-2-OH)) in toluene gave the unexpected heterobimetallic bis(aminophenoxy) rare-earth metal complexes [ON]₂LnLi(THF)₂ (Ln = Yb ( 1 ), Y ( 2 )). When the reactions were carried out in THF and TMEDA, amine elimination produced the aminophenoxy rare-earth metal amide complexes {[ON]LnN(SiMe₃)₂}₂ (Ln = Yb ( 5 ), Y ( 6 )) in ca 85% isolated yields. Complexes 5 and 6 could also be obtained from salt metathesis reaction of {[ON]LnCl(THF)}₂ (Ln = Yb ( 3 ), Y ( 4 )) with NaN(SiMe₃)₂ in a 1:2 molar ratio. In addition, treatment of complexes 3 and 4 with NaOAr (Ar = &bond;C₆H₄-4-^tBu) and (SiMe₃)₂NC(NPrⁱ)₂Na in 1:4 and 1:2 molar ratios provided the corresponding aminophenoxy rare-earth metal derivatives {[ON](μ-OAr)Ln(μ-OAr)Na(THF)₂}₂ (Ln = Yb ( 7 ), Y ( 8 )) and {[ON]Ln[(ⁱPrN)₂CN(SiMe₃)₂]}₂ (Ln = Yb ( 9 ), Y ( 10 )), respectively. These complexes were fully characterized, and their molecular structures were determined using single-crystal X-ray diffraction. Polymerization experiments showed that complexes 1 , 2 , 5 , 6 , 9 and 10 were highly active for the ring-opening polymerization of l -lactide in toluene, and complex 1 promoted l -lactide polymerization in a controlled fashion. The polymerization of rac-lactide initiated by the neutral aminophenoxy rare-earth metal complexes 5 , 6 , 9 and 10 in THF afforded heterotactic polymers.     

Synthesis,DNA interaction and photocleavage studies of ruthenium(II) complexes with 2-(pyrrole) imidazo[4,5-f]-1,10-phenanthroline as an intercalative ligand

Three Ru(II) complexes, namely [Ru(bipy)₂PRIP]²⁺ (1), [Ru(dmb)₂PRIP]²⁺ (2), and [Ru(phen)₂PRIP]²⁺ (3) (dmb = 4,4′-dimethyl-2,2′-bipyridine; PRIP = 2-(pyrrole) imidazo [4,5-f]-1,10-phenanthroline) have been synthesized and characterized by elemental analysis, mass spectra, IR, ¹H NMR and ¹³C NMR. The DNA-binding properties of the three complexes with calf-thymus DNA (CT-DNA) were investigated by spectrophotometry, fluorescence methods and viscosity measurements. The results suggest that all three complexes bind to CT-DNA through intercalation. Also, when irradiated at 365 nm, the three complexes promote the photocleavage of plasmid pBR-322 DNA. Under comparable experimental conditions, complex 3 cleaves DNA more effectively than complexes 1 and 2.     

Zinc(II) complexes of Triaza and Amidinate ligands: Efficient initiators for the ring‐opening polymerization of ε‐Caprolactone and rac‐Lactide

Zinc complexes supported by tertiary 1,3,5‐triazapenta‐1,3‐dienate ligand (L¹) and N ‐benzoyl‐N′ ‐arylbenzamidinate [aryl =2,6‐diisopropylphenyl (L²), phenyl (L³)] ligands have been synthesized and characterized. The reaction of L¹H with ZnEt₂ affords a mononuclear zinc complex [L¹ZnEt] ( 1 ) in good yield. Tetra nuclear zinc complex [(L¹)₂Zn₄O(OAc)₄] ( 2 ) is prepared by treating L¹H with one equivalent of Zn(OAc)₂ in toluene. Further, dinuclear zinc complexes [L²ZnEt]₂ ( 3 ) and [L³ZnEt]₂ ( 4 ) are obtained in good yields from L²H and L³H with ZnEt₂ in toluene respectively_. The complexes 1–4 have been characterized by ¹H/¹³C NMR spectroscopy and single crystal X‐ray diffraction studies. All of the complexes have been explored for their catalytic activity toward the ring‐opening polymerization (ROP) of ε ‐caprolactone. It has been found that complex 1 is an active catalyst for the polymerization of ε ‐caprolactone in presence of a cocatalyst benzyl alcohol (BnOH). While complex 2 is as active as 1 there is no need for a cocatalyst for the polymerization to proceed. Dinuclear zinc complexes 3 and 4 show very high activity for the ROP of ε ‐caprolactone (CL) and rac ‐lactide (LA) without requiring a cocatalyst. The resultant polymers are found to have very high molecular weight (M _n = 296 X 10³ g mol⁻¹) and relatively narrow polydispersity index compared to 1 and 2 .     

Structural characterization of alachlor complexes with transition metal ions by electrospray ionization tandem mass spectrometry

Electrospray ionization mass (ESI-MS) spectrometry was used to investigate the nature of metal complexes of alachlor and their dissociations on activation. Ions of the first row transition metal series were employed to react with alachlor and the products were subjected to collision-induced dissociation (CID) for further structural characterization. The formation of diverse complex ions including doubly charged metal/alachlor complexes; [3L + M]²⁺ and [4L + M]²⁺ (L: alachlor and M: transition metal ions) were observed depending on the experimental conditions including the tube lens offset voltage (TLOV) and relative concentrations of alachlor and transition metal ions. It is clear that complexation with transition metal ions alters the reactive site of alachlor, promoting the loss of chlorine over the loss of CH₃OH that is the major reaction pathway in uncomplexed system. Direct elimination of chlorine from alachlor molecule was confirmed by the use of MnBr₂ instead of MnCl₂. These evidences clearly illustrate the catalytic activities of the metal ions through insertion mechanism. The function of transition metal ions in complexation was emphasized comparing the fragmentation patterns with those of protonated molecule. A change in the oxidation state of copper from + 2 to + 1 during the dissociation of metal complex was observed in company with elimination of radicals which is specific for the copper complex ions.     

Effects of the ancillary ligands of polypyridyl cobalt(II) complexes on pH-induced spectral properties and DNA binding properties

Abstract  

Two new Co(II) complexes [Co(ipH)₂(bdipH)]²⁺ and [Co(8-HQ)₂(bdipH)] (ipH = imidazo[4,5-f][1,10]phenanthroline, bdipH = 2-(benzo[d][1,3]dioxol-4-yl)-1H-imidazo[4,5-f][1,10]phenanthroline, 8-HQ = 8-hydroxyquinoline) were synthesized and characterized in detail by elemental analysis, IR, and UV–Vis spectroscopic techniques. The effects of pH on the UV–Vis absorption and emission spectra of the complex were studied. The interaction of the two complexes with calf thymus DNA was explored by using viscosity measurements, electronic absorption titration, competitive binding experiments, and cyclic voltammetry. The experimental results show that complex [Co(ipH)₂(bdipH)]²⁺ exhibits pH-sensitive emission, the two complexes can bind to DNA in an intercalation mode, and the DNA binding affinity of complex [Co(ipH)₂(bdipH)]²⁺ (K _b = 2.11 × 10⁵ M⁻¹) is greater than that of complex [Co(8-HQ)₂(bdipH)] (K _b = 1.76 × 10⁵ M⁻¹). The results show that the size and shape of the ancillary ligand have significant effects on the binding affinity of DNA and complexes.     

Synthesis of O6‐Corona[3]arene[3]pyridazines and Their Molecular Recognition Property in Organic and Aqueous Media

O₆‐Corona[3]arene[3]pyridazines were synthesized from the one‐pot macrocyclic condensation reaction of 3,6‐dichlorotetrazine with 1,4‐dihydroquinone derivatives followed by the inverse electron demand Diels‐Alder reaction of the tetrazine rings with a cyclopentanone‐derived enamine. Conversion of six ester groups within macrocycle into all sodium acetate moieties afforded a water soluble O₆‐corona[3]arene[3]pyridazine. The coronary macrocycle host formed complexes selectively with organic ammoniums and dinitrile guests in a 1: 1 stoichiometric ratio in organic solvents with association constants ranging from (2.96 ± 0.10) × 10¹ to (2.53 ± 0.33) × 10⁵ L·mol⁻¹. Water soluble O₆‐corona[3]arene[3]pyridazine was also able to complex strongly with organic ammoniums in water to give an association constant up to (2.67 ± 0.21) × 10⁴ L·mol⁻¹. The pseudo‐rotaxane and inclusion structures of the host‐guest complexes were revealed by the X‐ray crystallography.     

Ionic iron(III) complexes bearing a dialkylbenzimidazolium cation: Efficient catalysts for magnesium‐mediated cross‐couplings of aryl phosphates with alkyl bromides

A series of ionic iron(III) complexes of general formula [HLⁿ ][FeX₄] (HL¹ = 1,3‐dibenzylbenzimidazolium cation, X = Cl, 1 ; HL¹, X = Br, 2 ; HL² = 1,3‐dibutylbenzimidazolium cation, X = Br, 3 ; HL³ = 1,3‐bis(diphenylmethyl)benzimidazolium cation, X = Br, 4 ) were easily prepared in high yields by the direct reaction of FeX₃ with 1 equiv. of [HLⁿ ]X under mild conditions. All of them were characterized using elemental analysis, Raman spectroscopy and electrospray ionization mass spectrometry, and X‐ray crystallography for 1 and 4 . In the presence of magnesium turnings and LiCl, these air‐ and moisture‐insensitive complexes showed high catalytic activities in direct cross‐couplings of aryl phosphates with primary and secondary alkyl bromides with broad substrate scope, wherein complex 4 was the most effective.     

Novel Dendritic PNP Chromium Complexes: Synthesis,Characterization, and Performance on Ethylene Oligomerization

Three dendritic PNP ligands with ethylenediamine, 1,4‐butanediamine, 1,6‐diaminohexane as bridged groups are synthesized in good yields, respectively. Three dendritic PNP chromium complexes ( C1  –  C3 ) are prepared with the ligands and chromium(III ) chloride tetrahydrofuran complex (CrCl₃(THF )₃) as materials. The dendritic PNP ligands and the synthetic chromium complexes are fully characterized by spectroscopic and analytical methods. All chromium complexes activated with methylaluminoxane (MAO ) exhibited moderate activities on ethylene oligomerization (7.90 × 10⁴ – 2.15 × 10⁵ g (mol Cr h)⁻¹] and had better selectivity for C₆ and C₈ oligomer, reaching up to 81%. The chromium complex ( C1 ) activated with diethylaluminium chloride (Et₂AlCl) has higher catalytic activity than the chromium complex C1 activated with MAO , although the chromium complex ( C1 ) activated with Et₂AlCl had lower selectivity for C₆ and C₈ oligomer. The effects of solvent and reaction parameters on ethylene oligomerization are also studied using the chromium complex C1 as pre ‐ catalyst and MAO as co ‐ catalyst. Under optimized conditions ([complex] = 2 μmol, Al/Cr = 500, 25 °C, 0.9 MP a ethylene, 30 min), the catalytic activity of complex C1 in toluene is 2.15 × 10⁵ g (mol Cr h)⁻¹ and the selectivity for C₆ and C₈ oligomer is 36.76%. In addition, the structure of complexes significantly affects both the catalytic activity and the selectivity on ethylene oligomerization.     

Synthesis,crystal structure,DNA/bovine serum albumin binding and antitumor activity of two transition metal complexes with 4‐acylpyrazolone derivative

Two new complexes, namely [Cu₆L₆] ( 1 ) and [Zn(HL)₂] ( 2 ) (H₂L = N‐(1‐phenyl‐3‐methyl‐4‐propenylidene‐5‐pyrazolone)‐2‐furancarboxylic acid hydrazide), have been synthesized and characterized. Single crystal X‐ray analysis indicates that complex 1 has a hexanuclear structure and complex 2 exhibits a mononuclear structure. The DNA/bovine serum albumin (BSA) binding properties of complexes 1 and 2 were investigated by absorption spectroscopy and fluorescence quenching. Both complexes could effectively intercalate to DNA with calculated quenching constants of 2.6 × 10⁵ and 1.25 × 10⁵ M^?1, respectively. The quenching mechanism of the intrinsic fluorescence of BSA by the complexes was found to be a static one. The cytotoxicities of 1 and 2 were investigated in two human tumor cell lines, human esophageal cancer cells (Eca‐109) and cervical cancer cells (HeLa). Complex 1 exhibits higher antitumor activity than 2 . Furthermore, 1 can inhibit HeLa cells by inducing apoptosis and G0/G1 phase cell cycle arrest. All results demonstrate that 1 and 2 both have DNA/BSA binding capacity and antitumor activity.     

Rhodium(III) and cadmium(II) complexes based on the polypyridyl ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz)

Tppz (2,3,5,6-tetrakis(2-pyridyl)pyrazine) complexes [Rh(tppz)(bpy)Cl][PF₆]₂.acetylacetone (bpy = 2,2′-bipyridine) and [{CdCl₂}₂(μ-tppz)].ethylene glycol have been synthesized and characterized by elemental analyses, IR, ¹H NMR, cyclic voltammetry, photoluminescence and electronic spectral studies. Solid state structures of both complexes have been determined by single-crystal X-ray crystallography. The structural determination shows that the dinuclear Cd(II) complex, [{CdCl₂}₂(μ-tppz)], is a 1D coordination polymer. An ORTEP drawing of [Rh(tppz)(bpy)Cl][PF₆]₂.acetylacetone shows that the coordination geometry around the Rh(III) center is a distorted octahedron. [{CdCl₂}₂(μ-tppz)] displays intraligand ¹(π–π^*) fluorescence and can potentially serve as a photoactive material. For the mononuclear Rh(III) complex, only a two-electron reduction process occurs at the metal with the elimination of Cl⁻ ligand. The emission of this complex is assigned as πd^* phosphorescence.     

Synthesis, characterization and photophysics of alkyne bridged bimetallic rhenium(I) and ruthenium(II) complexes

Six new homobimetallic and heterobimetallic complexes of rhenium(I) and ruthenium(II) bridged by ethynylene spacer [(CO)₃(bpy)Re(BL)Re(bpy)(CO)₃]²⁺ [Cl(bpy)₂Ru(BL)Ru(bpy)₂Cl]²⁺ and [(CO)₃(bpy)Re(BL)Ru(bpy)₂Cl]²⁺ (bpy = 2,2′-bipyridine, BL = 1,2-bis(4-pyridyl)acetylene (bpa) and 1,4-bis(4-pyridyl)butadiyne (bpb) are synthesized and characterized. The electrochemical and photophysical properties of all the complexes show a weak interaction between two metal centers in heterobimetallic complexes. The excited state lifetime of the complexes is increased upon introduction of ethynylene spacer and the transient spectra show that this is due to delocalization of electron in the bridging ligand. Also, intramolecular energy transfer from *Re(I) to Ru(II) in Re–Ru heterobimetallic complexes occurs with a rate constant 4 × 10⁷ s⁻¹.     

DNA interactions of ruthenium(II) complexes with a polypyridyl ligand: 2-(2, 5-dimethoxyphenyl)-1<Emphasis Type="Italic">H</Emphasis>-imidazo[4,5-<Emphasis Type="Italic">f</Emphasis>]1,10-phenanthroline

This article describes the synthesis of a polypyridyl ligand, namely 2-(2, 5-dimethoxyphenyl)-1H-imidazo[4,5-f]1,10-phenanthroline (DMPIP) and its Ru(II) complexes, namely [Ru(bipy)₂DMPIP]²⁺ (1), [Ru(dmb)₂DMPIP]²⁺ (2) and [Ru(phen)₂DMPIP]²⁺ (3) ((bipy = 2,2′-bipyridine, dmb = 4,4′-dimethyl-2,2′-bipyridine, phen = 1,10-phenanthroline). The complexes were characterized by elemental analysis, plus IR, ¹H-NMR and ¹³C [¹H]-NMR spectra. The interactions of the complexes with calf thymus DNA were investigated. The results indicate that the three complexes can intercalate into DNA. Under irradiation at 365 nm, all three complexes promote the photocleavage of plasmid pBR 322 DNA. Inhibitor studies suggest that singlet oxygen plays a significant role in the cleavage mechanism for the complexes.     

Cd(ΙΙ) and Mn(ΙΙ) complexes of a new hexadentate Schiff base ligand derived from an asymmetric tripodal tetraamine and 2-pyridinecarboxaldehyde

Two new compounds, [CdL_22pyfp(NO₃)](ClO₄) (1) and [MnL_22pyfpCl](ClO₄) (2), were prepared by the template condensation of a previously known ligand, (L_22py), and 2-pyridinecarboxaldehyde in the presence of Cd(NO₃)₂ · 4H₂O or MnCl₂ · 4H₂O in equimolar ratios. The resulting compounds were characterized by elemental analysis, IR and single crystal X-ray diffraction, and by NMR in the case of the Cd(II) complex. The Cd(II) ion is in an eight-coordinate environment that is best described as a distorted dodecahedron. The environment around the Mn(II) ion may be described as a distorted pentagonal bipyramid. The ¹H NMR spectrum of the cadmium complex shows the signal of the imine proton to have two satellites (³J = 44.4 Hz) with intensities of 1:6:1 due to coupling with the neighboring ^111/113Cd atom. The electronic spectra of both complexes, as well as the ligand, is explained on the basis of TD-DFT calculations.     

Synthesis and characterization of water‐soluble copper(II), cobalt(II) and zinc(II) complexes derived from 8‐hydroxyquinoline‐5‐sulphonic acid: DNA binding and cleavage studies

Three water‐soluble complexes, [Cu₂L₂Cl₂] ( 1 ), [CoL₂(im)₂] ( 2 ) and [ZnLClH₂O] ( 3 ) (HL = 8‐hydroxyquinoline‐5‐sulphonic acid; im = N ‐methylimidazole), were prepared and characterized using various spectral techniques. The DNA binding behaviour of complexes 1 – 3 was studied using UV–visible and circular dichroism (CD) spectra and cyclic voltammetry. All three complexes exhibit hypochromism but complexes 1 and 3 alone give a red shift of 4 nm with a significant binding constant of K _b = 2.1 × 10⁴ and 1.0 × 10⁴ M⁻¹, respectively, but complex 2 shows no red shift with lower K _b of 4.1 × 10³ M⁻¹. The voltammetric E _1/2 of complex 1 on interaction with herring sperm DNA shifts to a more positive potential, as expected, than complex 2 due to higher DNA affinity. Additionally, analysis of electrochemical data yields a value of K ₊/K ₂₊ greater than one suggesting that complex 1 binds to DNA through intercalation in the M(I) state. Evidently in CD spectral analysis, complex 1 exhibits a decrease in molar ellipticity with a red shift of 10 nm and a significant decrease in intensity compared to complexes 2 and 3 . This clearly indicates that complex 1 induces the B → A transition to a greater extent than 2 and 3 . Oxidative cleavage using circular plasmid pUC18 DNA with complex 1 was investigated using gel electrophoresis. Interestingly, complex 1 displays a strong DNA binding affinity and is efficient in cleaving DNA in the presence of H₂O₂ at pH = 8.0 at 37 °C.     

Dimethyltin(IV) complexes derived from hydroxamic acid and acylhydrazone ligands: Synthesis,DNA/bovine serum albumin interaction and cytotoxicity

Two novel dimethyltin(IV) complexes, Me₂SnL¹(PyCOO)(MeOH) ( 1 ) and Me₂SnL² ( 2 ) (HL¹ = 4‐pyridinehydroxamic acid and H₂L² = 2‐hydroxy‐N′‐[(2‐hydroxy‐5‐chlorophenyl)methylidene]benzoylhydrazone), were synthesized and characterized using elemental analyses, Fourier transform infrared and NMR (¹H, ¹³C) spectroscopies and single‐crystal X‐ray diffraction. In complex 1 the geometry around the tin atom is a six‐coordinated distorted octahedral configuration, while complex 2 exhibits five‐coordinated distorted trigonal bipyramid geometry. Preliminary in vitro cytotoxicity studies with two human cancer cell lines (HeLa and A549) using MTT assay show that complex 1 is more potent than complex 2 . The interactions of the two complexes with calf thymus DNA and bovine serum albumin were also investigated using UV–visible absorption spectral, thermal denaturation and viscosity measurements and docking analysis. Investigations indicate that the structures of the mixed ligands play an important role in the properties of the dimethyltin(IV) complexes, and, to some extent, the antitumor activities of the complexes are partly related to interactions with DNA and some proteins in cancer cells.     

Affinity capillary electrophoresis and density functional theory study of noncovalent interactions of cyclic peptide [Gly6]‐antamanide with small cations

ACE and density functional theory were employed to study the noncovalent interactions of cyclic decapeptide glycine‐6‐antamanide ([Gly⁶]AA), synthetic derivative of native antamanide (AA) peptide from the deadly poisonous fungus Amanita phalloides , with small cations (Li⁺, Rb⁺, Cs⁺, NH₄⁺, and Ca²⁺) in methanol. The strength of these interactions was quantified by the apparent stability constants of the appropriate complexes determined by ACE. The stability constants were calculated using the nonlinear regression analysis of the dependence of the effective electrophoretic mobility of [Gly⁶]AA on the concentration of the above ions in the BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, pH_MeOH 7.8, containing 0–70 mM concentrations of the above ions added in the form of chlorides). Prior to stability constant calculation, the effective mobilities measured at actual temperature inside the capillary and at variable ionic strength of the BGEs were corrected to the values corresponding to the reference temperature of 25°C and to the constant ionic strength of 10 mM. From the above ions, Rb⁺ and Cs⁺ cations interacted weakly with [Gly⁶]AA but no interactions of [Gly⁶]AA with univalent Li⁺ and NH₄⁺ ions and divalent Ca²⁺ ion were observed. The apparent stability constants of [Gly⁶]AA‐Rb⁺ and [Gly⁶]AA‐Cs⁺ complexes were found to be equal to 13 ± 4 and 22 ± 3 L/mol, respectively. The structural characteristics of these complexes, such as position of the Rb⁺ and Cs⁺ ions in the cavity of the [Gly⁶]AA molecule and the interatomic distances within these complexes, were obtained by the density functional theory calculations.     

Mononuclear metal (II) complexes of a Bis(organoamido)phosphate ligand with antimicrobial activities against Escherichia coli

A new tripodal ligand [PO(NH²MePy)₃] ( L ) (²MePy = 2‐(4‐methyl pyridyl)) have been synthesized by treating phosphorous oxychloride with 2‐Amino‐4‐methylpyridine in toluene under refluxing condition. The ligand was appeared as a white solid and characterized by several standard analytical and spectroscopic techniques such as FT‐IR, NMR (¹H, ¹³C{¹H} and ³¹P{¹H}) and ESI‐MS spectroscopy. The ligand ( L ) undergone metal‐assisted hydrolysis of one P–N bond when treated it with hydrated metal nitrates, M(NO₃)₂·xH₂O (M = Zn, Cu, Co and Ni) under hydrothermal reaction condition in DMF‐H₂O (1:1). This results in the formation of four mononuclear complexes [{PO₂(NH²MePy)₂}₂M] [M = Zn ( 1 ), Cu ( 2 ), Co ( 3 ), Ni ( 4 )], where ligand ( L ) hydrolyses to a anionic bis(organoamido)phosphate, [PO₂(NH²MePy)₂]⁻. All complexes were completely characterized by various analytical techniques and their solid state molecular structures were established by single crystal X‐ray diffraction. All complexes are isostructural with a metal (II) ion situating at the centre of a distorted octahedron. Two tridentate [PO₂(NH²MePy)₂]⁻ ligands are coordinated to metal(II) ion through N‐ and O‐donor atoms, thus neutralizing the charge of the complex. Optical properties of all complexes in solid state have been studied. Moreover, antimicrobial activities of complexes 1 – 4 have been explored. To the best of our knowledge, this is the first report of such compounds investigated for their antimicrobial activities.     

Theoretical study of the geometry and electronic structure of the trinuclear [AunAgm (HNCOH)3] (m + n = 3) complex

The structures and properties of different gold and silver mixed-metal trinuclear complexes, [Au_nAg_m(HNCOH)₃] (m + n = 3), were investigated theoretically. The computed properties were compared with those of the [Au₃(HNCOH)₃] complex. The geometries of all complexes were optimized at the B3LYP level of theory using the GEN basis set. The optimization results revealed that the most stable structures of pure Au and Ag complexes are almost similar. In addition, all complexes are flat and highly symmetric. It was shown that the silver substitution had a significant influence on the electronic properties. The metal–metal distances were in the order of: Au–Au < Au–Ag < Ag–Ag. The ionization potential and hardness were found to be decreased while the electron affinity, HOMO–LUMO gap and chemical potential were found to be increased from the [Au₃(HNCOH)₃] to the [Ag₃(HNCOH)₃] complex. The [Au₃(HNCOH)₃] complex was the least reactive in the studied series with the electronic chemical potential equal to −3.98 eV. On the other hand, the value of the chemical potential characterizing the most reactive complex, [Ag₃(HNCOH)₃], was −3.80 eV.     

Silver alkoxide and amino N-heterocyclic carbenes; syntheses and crystal structures

Silver(I) complexes of heterobidentate ligands that incorporate one or two N-heterocyclic carbene moieties coupled with an alcohol or amine group have been made by direct deprotonation of ligands of the form [HOCR¹R²CH₂(1-HC{NCHCHNR})][X], H₂L¹X (X = Br, I), [H₂NR¹CHR²CHR²(1-HC{NCHCHNR})][Br]₂ H₃L²X₂ (X = Cl, Br), and [H₂N{CH₂CH₂(1-HC[NCHCHNMes])}₂][X]₃ H₄L³X₃ (X = Cl, Br). Silver(I) oxide is sufficiently basic to deprotonate both the imidazolium and the alcohol functional groups of all but one of the L¹ ligand precursors, to afford rare examples of silver alkoxide complexes [Ag(L¹)], stabilised by the soft donor carbene. Another complex of L¹ is characterised as the carbene alcohol adduct [Ag(HL¹)₂I]. The analogous reactions of silver(I) oxide with the amino imidazolium precursors afford silver amino-carbenes [Ag(HL²)Br] with the potentially bidentate L² ligand, and [Ag(HL³)X] (X = Cl, Br) with the potentially tridentate L³ ligand. A single crystal X-ray diffraction study of the latter complex confirms that the neutral amine of the potentially tridentate L³ ligand is unco-ordinated; instead the structure contains discrete chains of T-shaped silver bis(carbene) halide moieties that bridge to form a zig-zag 2-connected polymer. Protonolysis of two of the silver alkoxide and amino adducts, [Ag(L^1a)] and [Ag(HL^2a)Br], affords imidazolium complexes salts [H₂L^1a][AgCl₂] and [Ag(H₂L^2a)Br][AgBr₂] that retain the Ag(I) centre as complex counterions. The single crystal X-ray structures of these salts have been determined and show the silver(I) cations are now incorporated into ladders or chains as silver(I) halo-anions, and a silver amine dative bond is present in the latter complex.