Structural influences on the lanthanide-actinide selectivity of some aminocarboxylates

Data for the resolution of americium from europium and terbium using 2,2′-diaminodiethylether-N,N,N′,N′-tetraacetate and 1,5-diaminopentane-N,N,N′,N′-tetraacetate are reported along with values of the formation constants of the La-Lu and Y chelates of the latter. It is shown that the minimum single-stage separation factor for Am³⁺ from Ln³⁺ cations, using 2,2′-diaminodiethylether-N,N,N′,-N′-tetraacetate with Dowex 50 resin, exceeds 1.7 for all Am-Ln pairs, and runs as high as 350 in the case of Am³⁺, La³⁺. The minimum of 1.7 occurs at Eu³⁺ in the lanthanon sequence. A novel separation of Am³⁺, Cm³⁺ and heavier actinons from each other and from all the lanthanons and yttrium appears to be feasible.     

The lack of intramolecular carbonyl ligand rearrangement in the stereospecifically 13co labelled (diamine)molybdenum tetracarbonyl derivatives

The preparation and spectral characterization of stereospecifically, axially labelled Mo(CO)₃(¹³CO)(diamine) complexes (diamine  N,N,N′,N′-tetramethylethylenediamine and N,N,N′,N′-tetramethyl-1,3-diaminopropane) and the rigidity (or lack of fluxionality) of the carbonyl ligands during subsequent thermal reactions of these derivatives are reported.     

The Complexation Reactions of N-methylated Polyamines with Silver(I) in Dimethylsulfoxide

Abstract

The thermodynamic parameters for the complex formation reactions in dimethylsulfoxide (dmso) between Ag(I) and the following polyamines: N,N′-dimethylethylenediamine (dmen), N,N,N′,N′-tetramethylethylenediamine (dmen), N,N″-dimethyl-diethylenetriamine (dmdien) and N,N,N′,N″, N″-pentamethyldiethylenetriamine (pmdien) have been determined by potentiometric and calorimetric techniques at 298 K and 0.1 mol dm^?3 ionic strength (NEt₄ClO₄). Only mononuclear complexes are formed (AgL_j ⁺ j = 1,2) where the ligands act prevalently as chelate agents. All the complexes are enthalpy stabilized whereas the entropy changes counteract the complex formation. The results are discussed in terms of different basicities and steric requirements of both the ligands and the complexes formed.     

Synthesis,characterization, and evaluation of biological activities of new 4′‐substituted ruthenium (II) terpyridine complexes: Prospective anti‐inflammatory properties

The synthesis and characterization of Ru (II) terpyridine complexes derived from 4′ functionalized 2,2′:6′,2″‐terpyridine (tpy) ligands are reported. The heteroleptic complexes comprise the synthesized ligands 4′‐(2‐thienyl)‐ 2,2′:6′,2″‐terpyridine) or (4′‐(3,4‐dimethoxyphenyl)‐2,2′:6′,2″‐terpyridine and (dimethyl 5‐(pyrimidin‐5‐yl)isophthalate). The new complexes [Ru(4′‐(2‐thienyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)Cl₂] ( 9 ), [Ru(4′‐(3,4‐dimethoxyphenyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)Cl₂] ( 10 ), and [Ru(4′‐(2‐thienyl)‐2,2′:6′,2″‐terpyridine)(5‐(pyrimidin‐5‐yl)‐isophthalic acid)(NCS)₂] ( 11 ) were characterized by ¹H‐ and ¹³C‐NMR spectroscopy, C, H, N, and S elemental analysis, UPLC‐ESI‐MS, TGA, FT‐IR, and UV‐Vis spectroscopy. The biological activities of the synthesized ligands and their Ru (II) complexes as anti‐inflammatory, antimicrobial, and anticancer agents were evaluated. Furthermore, the toxicity of the synthesized compounds was studied and compared with the standard drugs, namely, diclofenac potassium and ibuprofen, using hemolysis assay. The results indicated that the ligands and the complex 9 possess superior anti‐inflammatory activities inhibiting albumin denaturation (89.88–100%) compared with the standard drugs (51.5–88.37%) at a concentration of 500 μg g^?1. These activities were related to the presence of the chelating N‐atoms in the ligands and the exchangeable chloro‐ groups in the complex. Moreover, the chloro‐ and thiophene groups in complex 9 produce a higher anticancer activity compared with its isothiocyanate derivative in the complex 11 and the 3,4‐dimethoxyphenyl moiety in complex 10 . Considering the toxicity results, the synthesized ligands are nontoxic or far less toxic compared with the standard drugs and the metal complexes. Therefore, these newly synthesized compounds are promising anti‐inflammatory agents in addition to their moderate unique broad antimicrobial activity.     

Synthesis and X-ray crystal structures of N,N,N′,N′-tetraalkylpyridine-2,6-dithiocarboxamides (S-dapt) complexes of cobalt(II) and nickel(II)

Reactions of anhydrous CoX₂ (X?=?Br^?, SCN^?) and Ni(ClO₄)₂ with N,N,N′,N′-tetraisobutylpyridine-2,6-dithiocarboxamides (S-dbpt), N,N,N′,N′-tetraisopropyl pyridine-2,6-dithiocarboxamides (S-dppt), and N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamides (S-dept) lead to the formation of [Co(S-dbpt)Br₂] (1), [Co(S-dppt)(SCN)₂] (2), and [Ni(S-dept)₂]·(ClO₄)₂·H₂O (3), respectively. The X-ray crystal structures of the three S-dapt ligands and three complexes along with spectroscopic analyzes are presented. The molecular structure investigations of the S-dapt ligands show that the thiamide planes are twisted with respect to the pyridine ring, which is more in the case of phenyl groups. The structures of the Co(II) complexes reveal that an increase in steric crowding on the amide side arms of the ligands has no substantial effect on the geometry adopted by the corresponding complexes. The Co(II) gives only 1?:?1 five-coordinate, ion-paired complexes with a distorted square pyramidal geometry. Ni(II), on the other hand, prefers an octahedral geometry with 1?:?2 metal–ligand ratio. The coordination behavior of S-dapt has been compared to the analogous oxo(O-daap) ligands. Lesser propensity of S atom to get involved in H-bonding interactions ensures an S-N-S type of tridentate coordination by S-dapt.     

Synthesis and crystal structures of the Zn(II) and Co(II) complexes containing the reduced derivative nitronyl nitroxide

Two complexes of formulas [Zn(Hfac)₂(IM-IMH-Bph)] (I) and [Co(Hfac)₃](IM-Bph) (II), where IM-Bph = 2,2′-bis(1′-oxyl-4′,4′,5′,5′-tetramethylimidazoline-2′-yl)-bis(2-formylphenyl) ether; Hfac = hexafluoroacetylacetonate, have been synthesized and characterized by single-crystal X-ray diffraction. The X-ray analysis demonstrates that both I and II are mononuclear complexes. In I, each zinc ion is five-coordinated with four oxygen atoms from two Hfac ligands and one oxygen atom from nitroxide. Complex II contains one Co(III) atom with six oxygen atoms from three Hfac ligands and uncoordinated IM-Bph diradical, in which the Co²⁺ ion and NIT-Bph biradical can undergo the redox reaction.     

Molekülstrukturen von Kupfer(II)- und Eisen(III)-Chlorokomplexen mit di- und monoprotoniertem N-(Pyrid-2-ylmethyl)ethylendiamin-N,N′,N′-triacetat (H2pedta−; Hpedta2−)

Molecular Structures of Copper(II) and Iron(III) Chloro Complexes with di- and monoprotonated N-(pyrid-2-ylmethyl)ethylenediamine-N,N′,N′-triacetate (H₂pedta^?; Hpedta^2?) The molecular structures of two complexes of di- and monoprotonated N-(pyrid-2-ylmethyl)ethylenediamine-N,N′,N′ -triacetate (pedta^3?) with Cu^II and Fe^III as central atoms have been determined by single crystal X-ray diffraction methods. Both complexes have a distorted octahedral coordination with H₂pedta^? and Hpedta^2? as pentadentate ligands and a chloride ion occupying the sixth coordination site. The different oxidation states of the central atoms result in a completely different coordination behaviour of the carboxyl groups. In both complexes one of the ? CH₂? COOH groups is uncoordinated. In the Fe^III complex, the central atom is coordinated by the hydroxylic O atoms of the deprotonated carboxyl groups. Contrary to this in the Cu^II complex, the central atom is coordinated by the carbonylic O atoms. One of the coordinated carboxyl groups is protonated and the other is deprotonated. All protonated carboxyl groups in both complexes form intermolecular hydrogen bonds.     

Electronic structure and luminescent properties of antimony(III) complex compounds with nitrogen containing outer-sphere organic cations

X-Ray photoelectron (XPS) and luminescent spectroscopy have been used to investigate complex compounds of antimony(III) halides with nitrogen containing organic bases. Inequality of bonds of amine and imine groups was found by XPS to disappear when complexes of antimony(III) with N,N′-diphenylguanidine (Dphg) were formed. The appearance of N1s symmetric line when transiting from Dphg to the cation N,N′-diphenylguanidine ( Dphg⁺) in complex compounds of antimony(III) testifies to this. The study performed demonstrates that electron density increment on the antimony(III) central atom (complexing agent) results in the bathochromic shift ³P₁ → ¹ S ₀ of the luminescence band of antimony(III) ion.     

Intricacies of ligand coordination in tricarbonylchromium(0) complexes with ortho‐ and para‐fluorobiphenyls

The steric and electronic factors that influence which of the two rings of a substituted biphenyl ligand coordinates to chromium are of interest and it has been suggested that haptotropic rearrangements within these molecules may be limited if the arene–arene dihedral angle is too large. Two tricarbonylchromium(0) complexes and their respective free ligands have been characterized by single‐crystal X‐ray diffraction. In the solid state, tricarbonyl[(1′,2′,3′,4′,5′,6′‐η)‐2‐fluoro‐1,1′‐biphenyl]chromium(0), [Cr(C₁₂H₉F)(CO)₃], (I), exists as the more stable isomer with the nonhalogenated arene ring ligated to the metal center. Similarly, tricarbonyl[(1′,2′,3′,4′,5′,6′‐η)‐4‐fluoro‐1,1′‐biphenyl]chromium(0) crystallizes as the more stable isomer with the phenyl ring bonded to the Cr⁰ center. The arene–arene dihedral angles in these complexes are 55.77 (4) and 52.4 (5)°, respectively. Structural features of these complexes are compared to those of the DFT‐optimized geometries of ten tricarbonyl[(η⁶‐C₆H₅)(4‐F‐C₆H₄)]chromium model complexes. The solid‐state structures of the free ligands 2‐fluoro‐1,1′‐biphenyl and 4‐fluoro‐1,1′‐biphenyl, both C₁₂H₉F, exhibit arene–arene dihedral angles of 54.83 (7) and 0.71 (8)°, respectively. The molecules of the free ligands occupy crystallographic twofold axes and exhibit positional disorder. Weak intermolecular C—H…F interactions are observed in all four structures.     

Binuclear copper and zinc complexes possessing bio-potential ligands: synthesis,characterization, antimicrobial,SOD mimetic,DNA binding,and cleavage studies

Schiff bases (L) viz, N,N′,N′′,N′′′-tetra-3,4-dimethoxybenzalidene-3,3′-diaminobenzidine (TDBD), N,N′,N′′,N′′′-tetra-4-hydroxy-3-methoxybenzalidene-3,3′-diaminobenzidine (THMBD), and N,N′,N′′,N′′′-tetra-3-hydroxy-4-nitrobenzalidene-3,3′-diaminobenzidine (THNBD) afford binuclear [M₂LCl₄] complexes where M = Cu(II) or Zn(II). These Schiff bases and their binuclear complexes have been characterized by analytical and spectral data showing square-planar geometry on metalation with Cu²⁺. Intercalative binding of these complexes with DNA has been investigated by electronic absorption spectroscopy, viscosity measurements, cyclic voltammetry, and differential pulse voltammetry. Control DNA cleavage experiments using pUC19 supercoiled (SC) DNA and minor groove binder distamycin suggest that these synthesized complexes bind to the major groove. In the presence of a reducing agent like 3-mercaptopropionic acid (MPA), they show chemical nuclease activity. They also show an efficient photo-induced DNA cleavage on irradiation with a monochromatic UV light of 360 nm in the presence of inhibitors. Control experiments indicate the inhibition of cleavage in the presence of singlet oxygen quencher like sodium azide and the enhancement of cleavage in D₂O show the formation of singlet oxygen as reactive species. The superoxide dismutase (SOD)-mimetic activity of the synthesized complexes has been assessed for their ability to inhibit the reduction of nitroblue tetrazolium chloride (NBT). The complexes have promising SOD-mimetic activity. The antimicrobial results indicate that the complexes inhibit the growth of bacteria and fungi more than free ligands.     

Metallionen und H2O2. IV. Über Struktur und Aktivität der den H2O2-Zerfall katalysierenden Cu2+-Komplexe. II. Einfluss der Zahl der freien Koordinationsstellen

The Cu²⁺ chelates of the bidentate ligands 2,2′-bipyridine (I; [2]), N, N′-diglycyl-1,5-diaminopentane (VI), ethylenediamine (II; [2]), glycine (V) and pyrophosphate (III; [2]) are found–parallel to the spectrochemical series–to be more active in catalysis of H₂O₂ decomposition than the chelates of the terdentate ligands–antiparallel to the spectrochemical series–iminodiacetic acid (IX), glycylglycine (VIII), 2, 2′-diaminodiethylamine (VII) and 2, 2′, 2″-terpyridine (IV; [2]), the activity decreasing in the given series. If all four coordination positions of Cu²⁺ are engaged (e.g. complex with N, N′-di-(2-aminoethyl)-ethylenediamine (X)) the complex is inactive. The catalytic activity of the Cu²⁺-chelates is parallelled by the tendency to form ternary peroxo complexes.     

Substituent effects in homoleptic iron(II) and ruthenium(II) complexes of 4′-hydrazone derivatives of 2,2′:6′,2″-terpyridine

The synthesis and characterization of eight homoleptic iron(II) and ruthenium(II) complexes containing 4′-hydrazone-substituted 2,2′:6′,2″-terpyridine ligands are described. ¹H NMR spectroscopic data illustrate that the coordinated ligands undergo facile rotation about the C_pyridine–N_hydrazone bond when the N atom is methylated, and hindered bond rotation when the hydrazone NH unit is available for hydrogen bonding to solvent molecules. Detailed structural studies illustrate how the flexibility of the backbone of the complexes leads to significant variation in packing. Throughout the series of solid structures, the packing is dictated by a combination of face-to-face aromatic π-stacking, edge-to-face aromatic interactions and classical and non-classical hydrogen bonding.     

The influence of the ligands on the catalytic activity of a series of RhI complexes in reactions with phenylacetylene: Synthesis of stereoregular poly(phenyl) acetylene

The catalytic activity of a series of [Rh L-L chel]X complexes, in which we have varied the unsaturated ligand [L-L = cis, cis-cycloocta 1,5-diene(cod) or 2,5-norbornadiene(nbd) the nitrogen chelating ligand [chel = 2,2′-bipyridine(bipy), 2,2′-dipyridylamine(dipyam), 2,2′-bipyrazine (bipz), 4,4′-dimethyl-2,2′-bipyridine (4,4′-Me₂bipy)] and the counter ion [X = PF₆, ClO₄, BPh₄], has been examined in reactions with phyenylacetylene (PA). The catalytic behaviour of the [Rh(cod)Cl₂],tmeda (tmeda = N,N,N′,N′tetramethylethylendiamine), [Rh(cod)Cl₂],teda] (teda = triethylendiamine), of the dimer [Rh(cod)Cl]₂, and the use of NaOH as cocatalyst in different reaction conditions was also examined. The influence of the ligands on the catalytic activity of these Rh^I complexes is discussed. ¹H and ¹³C NMR spectra have shown that highly stereoregular polyphenylacetilene can be obtained. Conditions for homogeneous doping of PPA, to obtain materials whose conductivity varies over 10–11 magnitude orders, are proposed. The stability of the doped polymers is also discussed.     

STRUCTURE AND THERMAL PROPERTIES OF VOLATILE MIXED-LIGAND MAGNESIUM COMPLEXES: EFFECT OF TERT-BUTYL AND PHENYL SUBSTITUTES IN A FLUORINATED β-DIKETONATE

Journal of Structural Chemistry - Structures of volatile mixed-ligand complexes of magnesium with N,N,N′,N′-tetramethylethylenediamine (tmeda) and fluorinated β-diketonate ligands...     

Pyrrole Ligands. III. The Stability of Dipyrromethenato Complexes of Cu (II) and Ni (II) in Aqueous Solutions

The protonation and complex formation of the new ligand 3,3′, 5,5′-tetramethyl-dipyrromethene-4,4′-dicarboxylate in aqueous solutions was investigated by alkalimetric titrations and spectrophotometric measurements (25°, I = 1 (KNO₃)). The pK values for the N? H groups are 8.03 and 16.1 and logβ₂ of the complexes with Cu (II) and Ni (II) are 31.0 and 24.4, respectively. Comparison with other ligands shows that the dipyrromethenato group acts as a normal rigid aromatic dinitrogen ligand, despite the charge on one nitrogen atom.     

Masking of Lewis acidity trends in the solid‐state structures of trichlorido‐ and tribromido(2,2′:6′,2′′‐terpyridine‐κ3N,N′,N′′)gallium(III)

The molecular structures of trichlorido(2,2′:6′,2′′‐terpyridine‐κ³N,N′,N′′)gallium(III), [GaCl₃(C₁₅H₁₁N₃)], and tribromido(2,2′:6′,2′′‐terpyridine‐κ³N,N′,N′′)gallium(III), [GaBr₃(C₁₅H₁₁N₃)], are isostructural, with the Ga^III atom displaying an octahedral geometry. It is shown that the Ga—N distances in the two complexes are the same within experimental error, in contrast to expected bond lengthening in the bromide complex due to the lower Lewis acidity of GaBr₃. Thus, masking of the Lewis acidity trends in the solid state is observed not only for complexes of group 13 metal halides with monodentate ligands but for complexes with the polydentate 2,2′:6′,2′′‐terpyridine donor as well.     

Metallionen und H2O2. VI. Über Struktur und Aktivität der den H2O2-Zerfall katalysierenden Ni2+-Komplexe

The catalytic properties in H₂O₂ decomposition of Ni²⁺-chelates of the following ligands have been investigated: ethylenediamine, diethylenetriamine, triethylenetetramine, 2,2′-bipyridine, pyrophosphate and ethylenediamine-N, N, N′, N′-tetra-acetic acid, and of the following peptides and peptide-like ligands: glycylglycine, N,N′-diglycyl-ethylenediamine, N, N′-diglycyl-1, 5-diaminopentane and polymyxin B.     

Synthesis,characterization, optical and anti-bacterial properties of benzothiazole Schiff bases and their lanthanide (III) complexes

Two new Schiff base ligands comprising benzothiazole derivatives, namely (N,N′,E,N,N′E)-N,N′-(1,3-phenylenebis(methanylylidene))bis(5-nitrobenzo[d]thiazoL2-amine (L1) and (N,N′,E,N,N′E)-N,N′-(1,3-phenylene-bis(methanylylidene))bis(5-methylthiazo-L2-amine (L2), have been synthesized and thoroughly characterized using FTIR, ¹H NMR, mass UV/vis and fluorescence spectral techniques. Further, L1 and L2 lead to the formation of lanthanide complexes 1–6 with Ce(III), Nd(III), and Pr(III) ions in 1:2 (metal:ligand) stoichiometry. UV/vis spectra of L1, L2 and 1–6 exhibit characteristic ligand centered absorptions in the range of 230–350 nm. Besides, both ligands and complexes show significant emissions and good anti-bacterial activity against pathogenic bacteria. Ligands and complexes display anti-bacterial activity against bacteria Staphylococcus aureus (S. aureus) (MTCC 1144) causing skin infection and food poisoning and pimple-causing bacteria propionic bacteria acnes (P. acnes) (MTCC 1951).     

Iridium(III) Complexes with Sulfonyl and Fluorine Substituents: Synthesis,Stereochemistry and Effect of Functionalisation on their Photophysical Properties

The synthesis and photophysical and electrochemical characterisation of new heteroleptic iridium complexes with electron‐withdrawing sulfonyl groups and fluorine atoms bound to phenylpyridine ligands are reported. The emission energy of these materials strongly depends on the position of the sulfonyl groups and on the number of fluorine substituents. A 90 nm wide tuning range of photoluminescence from the blue‐green (λ_em=468 nm) of iridium(III)bis[2‐(4′‐benzylsulfonyl)phenylpyridinato‐N,C2′][3‐(pentafluorophenyl)‐pyridin‐2‐yl‐1,2,4‐triazolate] to the orange (λ_em=558 nm) of iridium(III)bis[2‐(3′‐benzylsulfonyl)phenylpyridinato‐N,C2′](2,4‐decanedionate) has been achieved. Emission quantum yields ranging from 47 to 71 % have also been found for degassed solutions of the complexes, and a surprisingly high value of 16 % was recorded for iridium(III)bis[2‐(5′‐benzylsulfonyl‐3′,6′‐difluoro)phenylpyridinato‐N,C2′](2,4‐decanedionate) in air‐equilibrated dichloromethane. A unusual stereochemistry of the benzylsulfonyl‐substituted dimer and heteroleptic complexes has been detected by ¹H NMR spectroscopy, and is characterised by the mutual cis disposition of the pyridyl nitrogen atoms of the phenylpyridine ligands, which differs from the most common trans arrangement reported in the literature.     

[2]Catenanes Built Around Octahedral Transition‐Metal Complexes that Contain Two Intertwined Endocyclic but Non‐sterically Hindering Tridentate Ligands

Sterically hindering bidentate chelates, such as 2,9‐diphenyl‐1,10‐phenanthroline, form entwined complexes with copper(I) and other tetrahedrally coordinated transition‐metal centres. To prepare octahedral complexes containing two entwined tridentate ligands and thus apply a strategy similar to that used for making catenanes with tetrahedral metal centres, the use of the classical terpy ligand (terpy=2,2′:6′,2′′‐terpyridine) appears to be attractive. In fact, 6,6′′‐diphenyl‐2,2′:6′,2′′‐terpyridine (dp‐terpy) is not appropriate due to strong “pinching” of the organic backbone by coordination to the metal and thus stable entwined complexes with this ligand cannot be obtained. Herein, we report the synthesis and coordination properties of a new family of tridentate ligands, the main features of which are their endocyclic nature and non‐sterically hindering character. The coordinating fragment consists of two 8′‐phenylisoquinolin‐3′‐yl groups attached at the 2 and 6 positions of a pyridine nucleus. Octahedral complexes containing two such entangled ligands around an octahedral metal centre, such as Fe^II, Ru^II or Co^III, are highly stable, with no steric congestion around the metal. By using functionalised ligands bearing terminal olefins, double ring‐closing metathesis leads to [2]catenanes in good yield with Fe^II or Co^III as the templating metal centre. The X‐ray crystallography structures of the Fe^II precursor and the Fe^II catenane are also reported. These show that although significant pinching of the ligand is observed in both Fe^II complexes, the system is very open and no steric constraints can be detected.