New unsymmetrical μ-phenoxo bridged binuclear copper(II) complexes

A series of binuclear Cu^II complexes [Cu₂XL] ⁿ⁺ having two copper(II) ions bridged by different motifs (X = OH^–, MeCO₂ ^–, or Cl^–) have been prepared using the ligands: H₂L¹ = 4-methyl-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L² = 4-nitro-2-[N-(2-{dimethylamino}ethyl-N-methyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol, H₂L³ = 4-methyl-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol and H₂L⁴ = 4-nitro-2-[N-(2-{diethylamino}ethyl-N-ethyl)aminomethyl]-6-[(prolin-1-yl)methyl]phenol. The complexes have been characterized by spectroscopic, analytical, magnetic and electrochemical measurements. Cryomagnetic investigations (80–300 K) revealed anti-ferromagnetic exchange between the Cu^II ions (–2J in the range –50 to –182 cm^–1). The strength of anti-ferromagnetic coupling lies in the order: OAc > OH > Cl. Cyclic voltammetry revealed the presence of two redox couples, assigned to Cu^II/Cu^II/Cu^II/Cu^I/Cu^I/Cu^I. The first reduction potential is sensitive to electronic effects from the aromatic ring substituents and steric effect on the donor nitrogens (side arm) of the ligand systems.     

Synthesis of flexible ligands for assembling two metals in close proximity. Magnetic,electrochemical and spectral properties of binuclear copper (II) complexes with different exogenous bridging motifs

Binuclear Cu^II complexes having new flexible heptadentate ligands 2,6-bis{[bis(3,3-N,N-dimethylaminopropyl)amino]methyl}-4-bromophenol [HL¹], 2,6-bis(3,3-N,N-dimethylaminopropyl)amino]methyl}-4-methylphenol [HL²], and 2,6-bis{[bis(3,3-N,N-dimethylaminopropyl)amino]methyl}-4-methoxyphenol [HL³], capable of assembling two copper ions in close proximity have been synthesized. Comparisons of the charge-transfer (CT) features, observed in electronic spectra of these complexes, are correlated with the electronic effect on the aromatic ring of the ligand systems. Cyclic voltammetry has revealed the existence of two reduction couples,

Exogenous bridging and nonbridging in Cu(II) complexes of Mannich base ligands: Synthesis and physical properties

Preparation of pentadentate ligands L¹, L², L³ and L⁴, where L¹ = 4-chloro-3-methyl-2[(prolin-1-yl)methyl]-6-[N-phenyl piperazin-1-yl)methyl]phenol, L² = 4-ethyl-2-[(prolin-1-yl)methyl]-6-[(N-phenyl piperazin-1-yl)methyl]phenol, L³ = 4-chloro-3-methyl-2-[(prolin-1-yl)methyl]-6-[N-methyl piperazin-1-yl]methyl phenol, L⁴ = 4-methoxy-2-[(prolin-1-yl)methyl]-6-[(N-phenyl piperazin-1-yl)methyl]phenol is described together with that of the corresponding Cu(II) complexes with various bridging motifs like OH, OAc and NO₂. The complexes are characterized by elemental analysis, electrochemical and electron paramagnetic spectral studies. Redox properties of the complexes in acetonitrile are highly quasireversible due to the chemical or/and stereochemical changes subsequent to electron transfer. The complexes show resolved copper hyperfine EPR at room temperature, indicating the presence of weak antiferromagnetic coupling between the copper atoms. Strengths of the antiferromagnetic interactions are in the order NO₂>OAc>OH.     

Synthesis,electrochemical and e.p.r. spectral studies of binuclear copper(II) complexes with new pentadentate L-proline-based binucleating ligands

The synthesis, reduction, optical and e.p.r. spectral properties of a series of new binuclear copper(II) complexes, containing bridging moieties (OH^–, MeCO₂ ^–, NO₂ ^–, and N₃ ^–), with new proline-based binuclear pentadentate Mannich base ligands is described. The ligands are: 2,6-bis[(prolin-1-yl)methyl]4-bromophenol [H₃L¹], 2,6-bis[(prolin-1-yl)methyl]4-t-butylphenol [H₃L²] and 2,6-bis[(prolin-1-yl)methyl]4-methoxyphenol [H₃L³]. The exogenous bridging complexes thus prepared were hydroxo: [Cu₂L¹(OH)(H₂O)₂] · H₂O (1a), [Cu₂L²(OH)(H₂O)₂] · H₂O (1b), [Cu₂L³(OH)(H₂O)₂] · H₂O (1c), acetato [Cu₂L¹(OAc)] · H₂O (2a), [Cu₂L²(OAc)] · H₂O (2b), [Cu₂L³(OAc)] · H₂O (2c), nitrito [Cu₂L¹(NO₂)(H₂O)₂] · H₂O (3a), [Cu₂L²(NO₂)(H₂O)₂] · H₂O (3b), [Cu₂L³(NO₂)(H₂O)₂] · H₂O (3c) and azido [Cu₂L¹(N₃)(H₂O)₂] · H₂O (4a), [Cu₂L²(N₃)(H₂O)₂] · H₂O (4b) and [Cu₂L³(N₃)(H₂O)₂] · H₂O (4c). The complexes were characterized by elemental analysis and by spectroscopy. They exhibit resolved copper hyperfine e.p.r. spectra at room temperature, indicating the presence of weak antiferromagnetic coupling between the copper atoms. The strength of the antiferromagnetic coupling lies in the order: NO₂ N₃ OH OAc. Cyclic voltammetry revealed the presence of two redox couples Cu^IICu^II Cu^IICu^I Cu^ICu^I. The conproportionality constant K _con for the mixed valent Cu^IICu^I species for all the complexes have been determined electrochemically.     

Synthesis,Characterization, Electrochemical and Spectroscopic Properties of [Ru(dppt)(bpy)Cl]+ and [Ru(pta)(bpy)Cl]+

Two novel Ru^II complexes [Ru(dppt)(bpy)Cl]ClO₄ (1) and [Ru(pta)(bpy)Cl]ClO₄ (2)[dppt, pta and bpy = 3-(1,10-phenanthrolin-2-yl)-5,6-diphenyl-as-triazine, 3-(1,10-phenanthrolin-2-yl)-as-triazino[5,6-f]acenaphthylene and 2,2-bipyridine, respectively] were synthesized and characterized by elemental analysis and electrospray mass spectrometry, ¹H-n.m.r., and u.v.–vis spectroscopy. The redox properties of the complexes were examined using cyclic voltammetry. Due to the strong -accepting character of asymmetric ligands, the MLCT bands of (1) and (2) are shifted significantly to lower energies by comparison with [Ru(tpy)(bpy)Cl]⁺.     

Substitutions of organopalladium(II) species with benzimidazole derivatives

The [Pd(cod)(cotl)]ClO₄ complex (cod = cycloocta-1,5-diene; cotl = cyclooctenyl, C₁₈H₁₃ ^–) undergoes substitutions with new Schiff base ligands containing benzimidazole L [L = 2-(2-N-n-propylidenephenyl)benzimidazole (L¹); 2-(2-N-i-propylidenephenyl)benzimidazole (L²); 2-(2-N-n-butylidenephenyl)benzimidazole (L³); 2-(2-N-i-butylidenephenyl)benzimidazole (L⁴)]. Facile displacement of cod by L occurs to produce complexes of the type [Pd(cotl)L]ClO₄· nMe₂CO (n= 0; L = L¹, L² or L³; n= 2, L = L⁴). Dihalobridge complexes of the type [Pd(cotl)X]₂(X = Cl or Br) undergo halogen-bridge cleavage with L¹–L⁴ to give mononuclear complexes of the type Pd(cotl)LX · nH₂O (n= 2, X = Cl, L = L¹; n= 0, X = Br, L = L¹; n= 0, X = Cl, L = L²; n= 0, X = Cl or Br, L = L³; n= 0, X = Cl, L = L⁴; n= 2, X = Br, L = L⁴) and a binuclear complex [Pd(cotl)Br]₂L². The complexes were characterised by physical properties, i.r., ¹H- and ¹³C-n.m.r. spectral techniques and by mass spectra. Probable structures have been proposed.     

Syntheses,crystal structures and magnetic properties of two cyano-bridged two-dimensional assemblies [Fe(salpn)]2 [Fe(CN)5NO] and [Fe(salpn)]2[Ni(CN)4]

Two cyano-bridged assemblies, [Fe^III(salpn)]₂[Fe^II(CN)₅NO] (1) and [Fe^III (salpn)]₂[Ni^II(CN)₄] (2) [salpn = N, N-1,2-propylenebis(salicylideneiminato)dianion], have been prepared and structurally and magnetically characterized. In each complex, [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– coordinates with four [Fe(salpn)]⁺ cations using four co-planar CN^– ligands, whereas each [Fe(salpn)]⁺ links two [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– ions in the trans form, which results in a two-dimensional (2D) network consisting of pillow-like octanuclear [—M^II—CN—Fe^III—NC—]₄ units (M = Fe or Ni). In complex (1), the NO group of [Fe(CN)₅NO]^2– remains monodentate and the bond angle of Fe^II—N—O is 180.0°. The variable temperature magnetic susceptibilities, measured in the 5–300 K range, show weak intralayer antiferromagnetic interactions in both complexes with the intramolecular iron(III)iron(III) exchange integrals of –0.017 cm^–1 for (1) and –0.020 cm^–1 for (2), respectively.     

Binuclear complexes with uranyl ions in non-equivalent coordination environments: synthesis and electrochemistry of complexes with binucleating aroyl hydrazones and 2,2′-bipyridine

The binuclear complexes [(UO₂bipy)₂L^1–3]NO₃, (1–3), {H₃L^1–3=1-(2-hydroxybenzoyl)-2-(2-hydroxy-benzal/3-methoxybenzal/naphthal)hydrazine}, and [(UO₂bipy)₂L^4–5](AcO)₂, (4–5), [H₂L^4–5 = 1-(2-aminobenzoyl)-2-(2-hydroxy-benzal/naphthal)hydrazine], have been synthesised. Complexes (4–5) possess longer O=U=O bonds than those in the complexes (1–3) as the strong -donating phenolate is replaced by the amino group. The spectral data and electrochemical behaviour confirm the electronic nonequivalence of the coordination environments around the two uranyl ions in these complexes.     

Bis[N-(2,6-di-t-butyl-1-hydroxyphenyl)salicylideneaminato]palladium(II) complexes and their radical intermediates generated by PbO2 and PPh3

New bis[N-(2,6-di-t-butyl-1-hydroxyphenyl)salicylideneminato]palladium(II) [Pd(L ^x )₂] complexes bearing HO and MeO substituents on the salicyaldehyde moiety were prepared, and their spectroscopic properties, as well as redox reactivity towards PbO₂ and PPh₃, examined by e.s.r. and u.v. spectroscopy. The complexes display charge-transfer bands in the 670–692 nm range in polar solvents, which are assigned to the d(Pd) * (chelated quinoid) transition. One-electron oxidation of Pd(L ^x )₂ produces Pd^II-stabilized radicals in which the unpaired electrons are localized on the phenoxy fragments and do not couple with the two radical centers. The complexes are easily reduced with PPh₃ via intramolecular electron-transfer from ligand to metal to give various radical intermediates and Pd. All detected radical species have been characterized by e.s.r. spectroscopy.     

Nuclease activity of mixed ligand complexes of copper(II) with heteroaromatic derivatives and picoline

New picoline adducts with carbamic acid [(furan-2-yl)methylene]hydrazide–Cu^II (CFMH) (1); thiocarbamic acid [(furan-2-yl)methylene]hydrazide–Cu^II (TFMH) (2); carbamic acid [(furan-2-yl)ethylidene]hydrazide–Cu^II (CFEH) (3), thiocarbamic acid [(furan-2-yl)ethylidene]hydrazide–Cu^II (TFEH) (4); carbamic acid [(thiophene-2-yl) methylene]hydrazide–Cu^II (CTMH) (5), thiocarbamic acid [(thiophene-2-yl)methylene]hydrazide–Cu^II (TTMH) (6), carbamic acid [(thiophene-2-yl)ethylidene]hydrazide–Cu^II (CTEH) (7), thiocarbamic acid [(thiophene-2-yl)ethylidene]hydrazide–Cu^II (TTEH) (8) have been prepared and characterized by analytical, i.r., electronic, e.s.r. and c.v. spectral data. The electronic spectra suggest distorted octahedral geometry for all the picoline adducts. E.s.r. g values lie between 2.251–2.286 at l.n.t. All the adducts undergo a quasi-reversible one-electron reduction in the range +0.47 to +0.51 V versus s.c.e., attributable to the Cu^III/Cu^II redox couple. The electron transfer is much faster in the semicarbazone complexes than in the thiosemicarbazone complexes. All adducts showed increased nuclease activity in the presence of oxidant; the nuclease activity is compared with that of the parent copper(II) complexes.     

Thiazolidine-2,4-dione derivatives with an so group outside the ring

The condensation of the potassium salt of thiazolidine-2,4-dione with bis(-chloro-ethyl) sulfide leads to bis[-(thiazolidine-2,4-dion-3-yl)ethyl]sulfide, which is readily oxidized by H₂O₂ to bis[-(thiazolidine-2,4-dion-3-yl)ethyl]sulfoxide. Products of condensation of the latter with oxo compounds were obtained. The structures of the synthesized compounds were proved by their UV and IR spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 48–50, January, 1981.     

New copper(II), manganese(III), nickel(II) and zinc(II) complexes with a chiral quadridentate Schiff base

A chiral Schiff base ligand (H₂L) was obtained by condensing 2-hydroxynaphthalene-1-carbaldehyde with substituted (1R,2R)-(–)-diaminocyclohexane. Chiral Schiff base complexes [CuL], [NiL], [ZnL] and [MnLOH] have been synthesized and characterized by elemental analyses, _M, i.r., u.v.–vis. and ¹H-n.m.r. and magnetic measurements.     

Synthesis of new condensed heterocyclic systems

Two new diamines — [1,3-bis(5-phenyl-1,2,4-triazol-3-yl)-4,6-diamino]benzene and [1,3-di-(2-benzimldazolyl)-4,6-diamino]benzene — were synthesized from 4,6-dinitroisophthalic acid. Newheterocyclic systems — 3,5,9,11-tetraphenyl[benzo[1,2-a; 4,5-a]bis(1,2,4-triazolo[4,3-c]pyrimidine)] and 2,16-diphenyl[benzo[1,2-a;4,5-a']bis(pyrimido[1,6-a]benzimidazole)]—were obtained by reaction of the diamines with benzoyl chloride and subsequent cyclization.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1274–1277, September, 1977.     

The preparation and characterisation of chromium(III) complexes of C-meso-5, 12-dimethyl-1, 4, 8, 11-tetraazacyclotetradecane (LM). Aquation and base hydrolysis kinetics ofcis- andtrans-[CrLMCl2]+

Summary The reaction of [CrCl₃(DMF)₃] with C-meso-5, 12-dimethyl-1, 4, 8, 11-tetra-azacyclotetradecane(L_M) in DMF gives a mixture ofcis-[CrL_MCl₂]Cl (ca. 90%) andtrans-[CrL_MCl₂]Cl (ca. 10%). These complexes are readily separated, as thecis-isomer is insoluble in warm methanol while thetrans-isomer is soluble. Using the dichlorocomplexes as precursors it has been possible to prepare a range ofcis-[CrL_MX₂]⁺ complexes (X=Br^–, NO ₃ ^– , N ₃ ^– , NCS^– and X₂=bidentate oxalate) and alsotrans-[CrL_MX₂]⁺ complexes (X=Br^–, H₂O or NCS^–). The spectroscopic properties and detailed stereochemistry of the complexes are discussed.The aquation and base hydrolysis kinetics ofcis- andtrans-[CrL_MCl₂]⁺ have been studied at 25° C. Base hydrolysis of thecis-complex is extremely rapid with K_OH =1.46×10⁵ dm³ mol^–1 at 25° C. This unusual reactivity appears to be associated with thetrans II stereochemistry of thesec-NH centres of the macrocycle. Base hydrolysis of thetrans complex with thetrans III chiral nitrogen stereochemistry is quite normal with k_OH =1.1 dm³ mol^–1 s^–1 at 25° C.     

An investigation of mononuclear and binuclear palladium(II) complexes of egta (egta = glycine,N,N′-(1,2-ethanediylbis(oxy-2,1-ethanediyl)bis[N-carboxymethyl]) by 1H-, 13C- and 15N-n.m.r. methods

1:1 and 2:1 palladium(II) complexes of egta^4– (egta^4– = glycine, N,N-(1,2-ethanediylbis)(oxy-2,1-ethanediyl)bis[N-carboxymethyl]) were prepared by 1:1 and 2:1 addition of K₂PdCl₄ to K₄egta, and examined by ¹H-, ¹³C- and ¹⁵N-n.m.r. methods. The 1:1 complex, [Pd(egta)]^2– in solution, utilizes a square-planar coordination comprised of two nitrogen and two glycinato carboxylate donors of egta^4–, leaving two glycinato carboxylates pendant. The complex has a cis-(R,S) stereochemistry which places both pendant carboxylates below the PdN₂O₂ square plane and the tether backbone of egta^4– in the up, up sense above the same plane. The cis-(R,S) assignment was assisted by computer simulations of the ¹³C-n.m.r. spectrum for four possible isomers. Only cis-(R,S) and trans-(R,R) calculated ¹³C-spectra were compatible with the observed ¹³C-n.m.r. pattern. The HH NOESY spectrum of [Pd(egta)]^2– detects long range coupling of the backbone –OCH₂CH₂O– linkage with both coordinated and pendant glycinato CH₂ moieties. The cis-(R,S) isomer's tortional movements allow such contacts whereas a trans-(R,R) isomer does not. The 2:1 complex, [Pd₂(egta)(H₂O)₂] in solution has an extended-chain structure with each palladium(II) center coordinated in the mer-iminodiacetate-like coordination with two bound glycinato-functionalities.     

Kinetics of the oxidation of iodide by copper(III)-imine-oxime complexes

Summary The copper(III)-imine-oxime complexes [Cu^III(Enio)]⁺ and [Cu^III(Pre)]⁺ {EnioH₂ =N,N-ethylene bis(isonitrosoacetylacetoneimine) and PreH₂ = N,N-propylene bis (isonitrosoacetylacetoneimine)} react very rapidly with iodide. The rate law under fixed conditions for the reaction is given by the equation: –d[Cu^III]/dt = (2k₂[I^–] + 2k₃[I^–]²)[Cu^III] The [Cu^III(Enio)]⁺ reaction was pH-independent whereas the [Cu (Pre)]⁺ reaction rate increased with increasing pH. Both the k₂ and the k₃ pathways are believed to involve one-electron transfer. An inner-sphere mechanism may operate in the pathway, first-order in [I^–].     

Preparation,spectroscopic and structural analysis of uranium-arabinose complexes

The reaction betweenL-arabinose and hydrated uranyl salts has been investigated in aqueous solution and the solid complexes of the type UO₂(L-arabinose)X ₂ · 2 H₂O, whereX=Cl^–, Br^–, and NO ₃ ^– , have been isolated and characterized. Due to the marked similarities with those of the structurally known Ca(L-arabinose)X ₂ · 4 H₂O and Mg(L-arabinose)X ₂ · 4 H₂O (X=Cl^– or Br^–) compounds, the UO ₂ ²⁺ ion binds obviously to twoL-arabinose moieties, through O1, O5 of the first and O3, O4 of the second molecule resulting into a six-coordinated geometry around the uranium ion with no direct U-X (X=Cl^–, Br^– or NO ₃ ^– ) interaction. The intermolecular hydrogen bonding network of the freeL-arabinose is rearranged upon uranium interaction. The -anomer configuration is predominant in the freeL-arabinose, whereas the -anomer conformation is preferred in the uranium complexes.

---

Darstellung, spektroskopische und Strukturanalyse von Uran-Arabinose Komplexen

Zusammenfassung Es wurde die Reaktion zwischenL-Arabinose und hydratisierten Uranylsalzen in wäßriger Lösung untersucht und kristalline Komplexe des Typs UO₂(L-Arabinose)X ₂ · 2 H₂O mitX=Cl^–, Br^– und NO ₃ ^– isoliert und charakterisiert. Wie aus markanten Ähnlichkeiten der Komplexe mit den bekannten Verbindungen Ca(L-Arabinose)X ₂ · 4 H₂O und Mg(L-Arabinose)X ₂ · 4 H₂O (X=Cl^– oder Br^–) abzuleiten ist, bindet das UO ₂ ²⁺ -Ion mit zweiL-Arabinose Einheiten, wobei sich durch die O1,O5-Koordination des ersten und die O3,O4-Koordination des zweiten Moleküls eine sechs-koordinierte Geometrie um das Uranylion [ohne direkte U-X (X=Cl^–, Br^– oder NO ₃ ^– ) Wechselwirkung] ausbildet. Die intermolekularen Wasserstoffbrücken zeigen nach der Wechselwirkung mit dem Uranylion eine Umgruppierung. In der freienL-Arabinose ist das -Anomere vorherrschend, in den Urankomplexen hingegen das -Anomere.

     

Synthesis and characterization of four new manganese(III) complexes and amino acid (L-aspartic acid, L-asparagine, L-glutamic acid, L-glutamine) Schiff bases

New series of manganese(III) complexes and amino acid Schiff bases have been prepared from 2-hydroxy-1-naphthaldehyde and α-amino acids [L-aspartic acid (Asp), L-asparagine (Asn), L-glutamic acid (Glu) and L-glutamine (Gln)]. The structures of the ligands and manganese complexes were identified using elemental analyses, i.r, electronic spectra, ¹H-n.m.r spectra, magnetic moment measurements and thermogravimetric analyses (t.g.a). The results suggest that H₂L¹: [N-(2-hydroxy-1-naphthylidene) aspartic acid] and H₂L³: [N-(2-hydroxy-1-naphthylidene)glutamic acid] Schiff bases behave as trianionic tetradentate species and coordinate to Mn(III) ion according to the general formula [MnL] · xH₂O complexes. But, H₂L²: [N-(2-hydroxy-1-naphthylidene) asparagine] and H₂L⁴: [N-(2-hydroxy-1-naphthylidene)glutamine] Schiff bases behave as dianionic tridentate and coordinate to Mn(III) ion in the general formula for [MnL(OOCH₃)] · xH₂O complexes.     

Synthesis, Spectral and Magnetic Characterisation of Copper(II) Dinuclear and Polynuclear Complexes with a Macrocyclic 34-Membered Hexaamine

34-Membered macrocyclic hexaamine containing two independent N₃ donor sets forms homodinuclear copper(II) complexes. Displacements of anions within the copper(II) chloride complexes occurred easily upon addition of different anions to the CuCl₂ complex. All new complexes were characterised by elemental analysis, IR, UV/VIS spectroscopy, and magnetic susceptibility measurements. Tetranuclear complexes indicate relation _Cu ^–1 vs. T in agreement with the Curie–Weiss law. A behaviour anomalous in relation to the phthalate complexes is shown by the [Cu₄L₂Cl₄(ox)₂] complex in which an antiferromagnetic coupling (J = - 53.9 cm^–1) between the Cu²⁺ ions through the C₂O ₄ ^2– bridge is observed.