Ferric complexes of acetoacetyl derivatives of poly(L-lysine), poly(L-ornithine), and poly(L-diaminobutyric acid). II. Conformational properties in solution. Evidence for a stereospecific complex formation

The conformational properties of ferric complexes of poly(N^ε-acetoacetyl-L -lysine), poly(N^δ-acetoacetyl-L -ornithine), and poly(N^γ-acetoacetyl-L -diaminobutyric acid) were investigated in 1:1 water/dioxane by CD techniques. Optical activity was found in the visible and in the uv absorption region of the polymeric complexes. The conformation of the peptide backbone was always that of a right-handed α-helix, and was found independent of the degree of complexation, at least up to a degree of binding of 20%. In the absorption region of the side-chain chromophores the optical activity is substantially affected by complex formation. In all three cases a splitting of the ligand π → π* transition centered at 257 nm is observed. These data suggest a stereospecific complex formation. From the signs of the splitting it also appears that the chirality of the poly(N^δ-acetoacetyl-L -ornithine) complex is opposite that of the other two polymers.     

Ferric complexes of acetoacetyl derivatives of poly(L-lysine), poly(L-ornithine), and poly(L-diaminobutyric acid). I. Preparation and absorption properties in solution

Poly(N^ε-acetoacetyl-L -lysine), poly(N^δ-acetoacetyl-L -ornithine) and poly(N^γ-acetoacetyl-L -diaminobutyric acid) form colored complexes with ferric ions in water/dioxane solutions. These complexes are soluble at pH values lower than 2.8 and show their maximum absorption at 257 nm in the uv and at 478 nm in the visible region; whereas the ferric complex of the model compound n-hexylacetoacetamide exhibits absorptions centered at 258 and 536 nm, respectively. It is shown that in the complex of the model compound one metal ion is bound per acetoacetamide group, while in the complexes of the three polymers two β-ketoamides side chains are bound per ferric ion under the same solvent, pH, concentration, and ionic strength conditions. The binding constants of ferric ions to the three polymers, and the formation constant of the ferric complex of the model compound are also evaluated.     

Spectroscopic and equilibrium dialysis studies of poly(α-L-glutamic acid)–Cu(II) complexes in the pH range 4–7

The formation of complex between the Cu²⁺ ion and poly(α-L -glutamic acid) [poly(Glu)] in 150 mM NaCl solutions was studied by uv–visible absorption and equilibrium dialysis methods at the mixing ratios of Glu residues to Cu²⁺, R, of 32, 16, and 8 and in the pH range 4–7. The results showed that more than 90% of Cu²⁺ ions bind to the poly(Glu) at pH > 4.9, but the bound Cu(II) begins to dissociate with a decrease in pH. The absorption spectra of bound Cu(II) varied with pH and R in a complicated manner. Three different component spectra were disclosed from the analysis of the pH dependence of the bound spectra. We concluded that poly(Glu)–Cu(II) complexes fall into three classes in the pH range 4–7, with the proportions of these complexes varying with both pH and R. The three complexes predominate either in the helix or extended-coil region, in the helix–coil transition region, or in the helix-aggregate region. The stability constant and binding mode of each Cu(II)–Glu complex were estimated from the dialysis data. With these results, the possible structure of each complex is discussed.     

Free metal ion depletion by "Good's" buffers. I. N-(2-acetamido)iminodiacetic acid 1:1 complexes with calcium(ii). magnesium(II), zinc(II), manganese(II), cobalt(II), nickel(II), and copper(II).

Formation (affinity) constants for 1:1 complexes of N-(2-acetamido)iminodiacetic acid (ADAH₂) with Ca(II), Mg(II), Mn(II), Zn(II), Co(II), Ni(II), and Cu(II) have been determined. Probable structures of the various metal chelates existing in solution are discussed. Values for the deprotonation of the amide group in [Cu(ADA)] and subsequent hydroxo complex formation are also reported. The use of ADA as a buffer is considered in terms of metal buffers complexes which can be formed at physiological pH, i.e., at pH 7.0 there is essentially no free metal ion in 1:1 M²⁺ to ADA solutions.     

Cupric complexes of poly(L-Lysine,L-Tyrosine): Spectroscopic determination of structure in aqueous solution

The formation and structure of two Cu(II)-(L-Lys, L-Tyr)_n complexes have been investigated using potentiometric, absorption, circular dichroism (CD), and resonance Raman measurements. Two complexes have been detected. The first, which is fully defined at pH 7.8, contains four nitrogens-two from amino groups of lateral chains and two from peptide groups-and a phenolate oxygen, presumably in apical position, bound to the metal. The second complex that forms at pH 11.6–12.2 contains a cupric ion coordinated to four peptide nitrogens.     

Biological assays and noncovalent interactions of pyridine-2-carbaldehyde thiosemicarbazonecopper(II) drugs with [poly(dA–dT)]2, [poly(dG–dC)]2, and calf thymus DNA

The interaction of the Cu(II) drugs CuL(NO₃) and CuL′(NO₃) (HL is pyridine-2-carbaldehyde thiosemicarbazone and HL′ is pyridine-2-carbaldehyde 4N-methylthiosemicarbazone, in water named [CuL]⁺ and [CuL′]⁺) with [poly(dA–dT)]₂, [poly(dG–dC)]₂, and calf thymus (CT) DNA has been probed in aqueous solution at pH 6.0, I = 0.1 M, and T = 25 °C by absorbance, fluorescence, circular dichroism, and viscosity measurements. The results reveal that these drugs act as groove binders with [poly(dA–dT)]₂, with a site size n = 6–7, whereas they act as external binders with [poly(dG–dC)]₂ and/or CT-DNA, thus establishing overall electrostatic interaction with n = 1. The binding constants with [CuL′]⁺ were slightly larger than with [CuL]⁺. The title compounds display some cleavage activity in the presence of thiols, bringing about the rupture of the DNA strands by the reactive oxygen species formed by reoxidation of Cu(I) to Cu(II); this feature was not observed in the absence of thiols. Mutagenic assays performed both in the presence and in the absence of S9 mix, probed by the Ames test on TA 98, TA 100, and TA 102, were negative. Weak genotoxic activity was detected for [CuL]⁺ and [CuL′]⁺, with a significative dose–response effect for [CuL′]⁺, which was shown to be more cytotoxic in the Ames test and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell proliferation assays. Methylation of the terminal NH₂ group enhances the antiproliferative activity of the pyridine-2-carbaldehyde thiosemicarbazones.     

Equilibrium and structural studies on Co(II), Ni(II), Cu(II) and Zn(II) complexes with N-(2-benzimidazolyl)methyliminodiacetic acid: crystal structures of Ni(II) and Cu(II) complexes

Combined pH-metric, UV-Vis, ¹H NMR and EPR spectral investigations on the complex formation of M(II) ions (M=Co, Ni, Cu and Zn) with N-(2-benzimidazolyl)methyliminodiacetic acid (H₂bzimida, hereafter H₂L) in aqueous solution at a fixed ionic strength, I=10⁻¹ mol dm⁻³, at 25 ± 1 °C indicate the formation of M(L), M(H₋₁L)⁻ and M₂(H₋₁L)⁺ complexes. Proton-ligand and metal-ligand constants and the complex formation equilibria have been elucidated. Solid complexes, [M(L)(H₂O)₂] · nH₂O (n=1 for M = Co and Zn, n=2 for M = Ni) and {Cu (μ-L) · 4H₂O}_n, have been isolated and characterized by elemental analysis, spectral, conductance and magnetic measurements and thermal studies. Structures of [Ni(L)(H₂O)₂] · 2H₂O and {Cu(μ-L) · 4H₂O}_n have been determined by single crystal X-ray diffraction. The nickel(II) complex exists in a distorted octahedral environment in which the metal ion is coordinated by the two carboxylate O atoms, the amino-N atom of the iminodiacetate moiety and the pyridine type N-atom of the benzimidazole moiety. Two aqua O atoms function as fifth and sixth donor atoms. The copper(II) complex is made up of interpenetrating polymeric chains of antiferromagnetically coupled Cu(II) ions linked by carboxylato bridges in syn-anti (apical-equatorial) bonding mode and stabilized via interchain hydrogen bonds and π-π stacking interactions.     

Synthesis and conformational study of poly(N -benzyl-L-lysine) and its benzyloxycarbonyl derivative

The solvent-and pH-induced conformational changes are examined in order to investigate the influence of benzyl group. Polymer was prepared via N^?-benzyloxycarbonyl, N^?-benzyl-N^α-carboxy-L -lysine anhydride. The resulting poly (N^?-benzyloxycarbonyl, N^?-benzyl-L -lysine) was obtained in high yield and had a high molecular weight. The protected polymer was removed into poly (N^?-benzyl-L -lysine) by treating it with hydrogen bromide. From the results of the ORD and CD, the protected polymer has a righthanded α-helix, showing [m′]₂₃₃ = –10,300, [θ]₂₂₀ = –27,600 and [θ]₂₀₇ = –25,100 in dioxane. The breakdown of the helical conformation is found to occur at 8% dichloroacetic acid in chloroform-dichloroacetic acid mixture. In the pH range 3.35–6.90, poly (N^?-benzyl-L -lysine) is in a random coil structure. In the pH range 7.50–13.0, the polypeptide has a right-handed α-helix structure; [m′]₂₃₃ = –12,000, [0]₂₂₀ = –27,200, and [0]₂₀₇ = –27,000. In comparison with poly-L -lysine, the coil-to-helix transition is observed at lower pH range in 50% n-propanol. Above pH 8 by heating, the α ? β transition of poly (N^?-benzyl-L -lysine) is not observed in an aqueous media.     

Synthesis, structural and corrosion inhibition studies on cobalt(II), nickel(II), copper(II) and zinc(II) complexes with 2-acetylthiophene benzoylhydrazone

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes with 2-acetylthiophene benzoylhydrazone have been synthesized and characterized by elemental analyses, magnetic susceptibility measurements, electronic, IR, NMR and ESR spectral techniques. The molecular structures of ligand and its copper(II) complex have been determined by single crystal X-ray diffraction technique. The Cu(II) complex possesses a CuN₂O₂ chromophore with a considerable delocalization of charge. The structure of the complex is stabilized by intermolecular π–π stacking and C–H?π interactions. Hatbh acts as a monobasic bidentate ligand in all the complexes bonding through a deprotonated C–O⁻ and >CN groups. Electronic spectral studies indicate an octahedral geometry for the Ni(II) complex while square planar geometry for the Co(II) and Cu(II) complexes. ESR spectrum of the Cu(II) complex exhibits a square planar geometry in solid and in DMSO solution. The trend g_|| > g_⊥ > 2.0023 indicates the presence of an unpaired electron in the d_x²-y² orbital of Cu(II). The electro-chemical study of Cu(II) complex reveals a metal based reversible redox behavior. The Ni(II) complex shows exothermic multi-step decomposition pattern of the bonded ligand. The ligand and its most of the metal complexes show appreciable corrosion inhibition properties for mild steel in 1 M HCl medium. [Co(atbh)₂] complex exhibited the greatest impact on corrosion inhibition among the other compounds.     

Synthetic, EPR spectroscopic, magnetic and X-ray crystallographic structural studies on copper(II) complexes of the tridentate N2S donor ligand formed from 6-methyl-2-formylpyridine and S-methyldithiocarbazate (Hmpsme)

New copper(II) complexes of general empirical formula, Cu(mpsme)X · xCH₃COCH₃ (mpsme = anionic form of the 6-methyl-2-formylpyridine Schiff base of S-methyldithiocarbazate; X = Cl, N₃, NCS, NO₃; x = 0, 0.5) have been synthesized and characterized by IR, electronic, EPR and susceptibility measurements. Room temperature μ_eff values for the complexes are in the range 1.75-2.1 μ_B typical of uncoupled or weakly coupled Cu(II) centres. The EPR spectra of the [Cu(mpsme)X] (X = Cl, N₃, NO₃, NCS) complexes reveal a tetragonally distorted coordination sphere around the mononuclear Cu(II) centre. We have exploited second derivative EPR spectra in conjunction with Fourier filtering (sine bell and Hamming functions) to extract all of the nitrogen hyperfine coupling matrices. While the X-ray crystallography of [Cu(mpsme)NCS] reveals a linear polymer in which the thiocyanate anion bridges the two copper(II) ions, the EPR spectra in solution are typical of a magnetically isolated monomeric Cu(II) centres indicating dissociation of the polymeric chain in solution. The structures of the free ligand, Hmpsme and the {[Cu(mpsme)NO₃] · 0.5CH₃COCH₃}₂ and [Cu(mpsme)NCS]_n complexes have been determined by X-ray diffraction. The {[Cu(mpsme)NO₃] 0.5CH₃COCH₃}₂ complex is a centrosymmetric dimer in which each copper atom adopts a five-coordinate distorted square-pyramidal geometry with an N₂OS₂ coordination environment, the Schiff base coordinating as a uninegatively charged tridentate ligand chelating through the pyridine and azomethine nitrogen atoms and the thiolate, an oxygen atom of a unidentate nitrato ligand and a bridging sulfur atom from the second ligand completing the coordination sphere. The [Cu(mpsme)(NCS)]_n complex has a novel staircase-like one dimensional polymeric structure in which the NCS⁻ ligands bridge two adjacent copper(II) ions asymmetrically in an end-to-end fashion providing its nitrogen atom to one copper and the sulfur atom to the other.     

Conformational properties of poly[d(G-T)].poly[d(C-A)] and poly[d(A-T)] in low- and high-salt solutions: NMR and laser Raman analysis

³¹P- and ¹H-nmr and laser Raman spectra have been obtained for poly[d(G-T)]·[d(C-A)] and poly[d(A-T)] as a function of both temperature and salt. The ³¹P spectrum of poly[d(G-T)]·[d(C-A)] appears as a quadruplet whose resonances undergo separation upon addition of CsCl to 5.5M. ¹H-nmr measurements are assigned and reported as a function of temperature and CsCl concentration. One dimensional nuclear Overhauser effect (NOE) difference spectra are also reported for poly[d(G-T)]·[d(C-A)] at low salt. NOE enhancements between the H8 protons of the purines and the C5 protons of the pyrimidines, (H and CH₃) and between the base and H-2′,2″ protons indicate a right-handed B-DNA conformation for this polymer. The NOE patterns for the TH3 and GH1 protons in H₂O indicate a Watson–Crick hydrogen-bonding scheme. At high CsCl concentrations there are upfield shifts for selected sugar protons and the AH2 proton. In addition, laser Raman spectra for poly[d(A-T)] and poly[d(G-T)]·[d(C-A)] indicate B-type conformations in low and high CsCl, with predominantly C2′-endo sugar conformations for both polymers. Also, changes in base-ring vibrations indicate that Cs⁺ binds to O2 of thymine and possibly N3 of adenine in poly[d(G-T)]·[d(C-A)] but not in poly[d(A-T)]. Further, ¹H measurements are reported for poly[d(A-T)] as a function of temperature in high CsCl concentrations. On going to high CsCl there are selective upfield shifts, with the most dramatic being observed for TH1′. At high temperature some of the protons undergo severe changes in linewidths. Those protons that undergo the largest upfield shifts also undergo the most dramatic changes in linewidths. In particular TH1′, TCH₃, AH1′, AH2, and TH6 all undergo large changes in linewidths, whereas AH8 and all the H-2′,2″ protons remain essentially constant. The maximum linewidth occurs at the same temperature for all protons (65°C). This transition does not occur for d(G-T)·d(C-A) at 65°C or at any other temperature studied. These changes are cooperative in nature and can be rationalized as a temperature-induced equilibrium between bound and unbound Cs⁺, with duplex and single-stranded DNA. NOE measurements for poly[d(A-T)] indicate that at high Cs⁺ the polymer is in a right-handed B-conformation. Assignments and NOE effects for the low-salt ¹H spectra of poly[d(A-T)] agree with those of Assa-Munt and Kearns [(1984) Biochemistry 23 , 791–796] and provide a basis for analysis of the high Cs⁺ spectra. These results indicate that both polymers adopt a B-type conformation in both low and high salt. However, a significant variation is the ability of the phosphate backbone to adopt a repeat dependent upon the base sequence. This feature is common to poly[d(G-T)]·[d(C-A)], poly[d(A-T)], and some other pyr–pur polymers [J. S. Cohen, J. B. Wouten & C. L Chatterjee (1981) Biochemistry 20 , 3049–3055] but not poly[d(G-C)].     

Copper(II) complexation by D-glucosamine. Spectroscopic and potentiometric studies

The Cu(II) complex formation equilibria of D- glucosamine were studied in aqueous solution by potentiometric and spectroscopic (ESR, CD, absorption spectra) techniques. All data agree that two major species are formed in the pH region 6–9 involving two D-glucosamine ligand molecules bound to the cupric ion via NH₂(CuL₂) or NH₂ and O^? (CuH_?2L₂). In the latter case deprotonated hydroxyls were found to be very effective coordination sites for Cu(II) giving rise to chelate complexes. On the contrary, no complex formation was observed for the Cu(II) N-acetyl-D-glucosamine system.     

Coordination properties of ethyl bis(pyridin-2-ylmethyl)phosphate ligand with copper and zinc chloride. X-ray crystal structure of Cu(II) complex

A new ethyl bis(pyridin-2-ylmethyl)phosphate (2-bis(pm)Ope) ligand has been synthesized and used for synthesis of copper(II) and zinc(II) complexes of the formula [MCl₂(2-bis(pm)Ope)] [M = Cu(II), Zn(II)]. Despite having the same general formula, Cu(II) and Zn(II) complexes are not isostructural. The Zn(II) complex is four coordinated (MCl₂N₂) forming probably tetrahedral structure whereas the Cu(II) complex of distorted square pyramidal geometry is five coordinated (MCl₂ON₂). The later compound not only coordinates by two nitrogen atoms of pyridine rings but also by the oxygen atom of pyridin-2-ylmethoxyl residue. The compound (2-bis(pm)Ope) has been obtained as the product of diethyl (pyridin-2-ylmethyl)phosphate’s (2-pmOpe) transestrification. The compounds have been identified and characterized by IR, far-IR, ¹H NMR, ³¹P NMR and elemental analyses. The crystal structure of copper(II) complex i.e. [CuCl₂(2-bis(pm)Ope)] has been determined by the X-ray diffraction method. The low temperature magnetic study reveals significant antiferromagnetic interaction between copper centers through the H-bond system.     

Comparative studies on copper(I) complexes: synthesis, X-ray crystallography and electrochemical properties of [Cu(dafone)nX] complexes (dafone=4,5-diaza-fluoren-9-one, X=Br, I, SCN)

The synthesis, X-ray structures and electrochemical properties of stable five-coordinate, trigonal-bipyramidal Cu^I complexes of dafone (4,5-diaza-fluoren-9-one) [Cu(dafone)₂X] with X=Br (1) or I (2) as ancillary ligands are discussed. The thiocyanate-bridged polymeric Cu^I complex of dafone, [Cu(dafone)(SCN)]_n (3), forms two-dimensional sheets in the crystal, held together by weak interactions involving the dafone ketone group, while the phenanthroline complex, [Cu(phen)(SCN)]_n (4), a zigzag arrangement of the phen ligands leads to interchain π-stacking within the lattice. The electrochemical studies reveal that dafone stabilizes the Cu^I oxidation state more efficiently than phen due to its better π-acceptor ability as indicated by more positive redox potentials for the Cu^I/Cu^II couple.     

New dinuclear copper(II) and zinc(II) complexes for the investigation of sugar–metal ion interactions

We have studied the binding interactions of biologically important carbohydrates (d-glucose, d-xylose and d-mannose) with the newly synthesized five-coordinate dinuclear copper(II) complex, [Cu₂(hpnbpda)(μ-OAc)] (1) and zinc(II) complex, [Zn₂(hpnbpda)(μ-OAc)] (2) [H₃hpnbpda = N,N′-bis(2-pyridylmethyl)-2-hydroxy-1,3-propanediamine-N,N′-diacetic acid] in aqueous alkaline solution. The complexes 1 and 2 are fully characterized both in solid and solution using different analytical techniques. A geometrical optimization was made of the ligand H₃hpnbpda and the complexes 1 and 2 by molecular mechanics (MM+) method in order to establish the stable conformations. All carbohydrates bind to the metal complexes in a 1:1 molar ratio. The binding events have been investigated by a combined approach of FTIR, UV–vis and ¹³C NMR spectroscopic techniques. UV–vis spectra indicate a significant blue shift of the absorption maximum of complex 1 during carbohydrate coordination highlighting the sugar binding ability of complex 1. The apparent binding constants of the substrate-bound copper(II) complexes have been determined from the UV–vis titration experiments. The binding ability and mode of binding of these sugar substrates with complex 2 are indicated by their characteristic coordination induced shift (CIS) values in ¹³C NMR spectra for carbon atoms C1, C2, and C3 of sugar substrates.     

Synthesis,structure and a fourier transform infrared study of Pt(II), Cu(II), and Mg(II) Complexes with xanthosine-5′-monophosphate

The reaction of xanthosine-5′'-monophosphate disodium salt (5′-XMPNa₂) with Pt(II), Cu(II) and Mg(II) ions produced compounds of the type cis- and trans-Pt(NH₃)₂(XMPNa₂)_nCl₂·xH₂O, where n = 1 or 2; Pt(XMPNa₂)_nCl₂·xH₂O, where n = 1-4, x = 1,4 & 6; Cu(XMP)·6H₂O and Mg(XMP)·xH₂O, where x = 9 or 4. In the complexes synthesized here at neutral pH values, the nucleotide binds through the N_7-atom of the purine ring system, whereas for Cu(II) and Mg(II) compounds obtained at pH = 4 a direct metal-phosphate interaction as well as N_τ bonding is proposed.     

13C Nuclear magnetic resonance study of salt induced conformational change of basic polypeptides: Poly (L-lysine), poly (L-arginine), and poly (L-ornithine)

A ¹³C-nmr study of the salt-induced helix–coil transition of the basic polypeptides poly(L -lysine) [(Lys)_n], poly(L -arginine) [(Arg)_n], and poly (L -ornithine) [(Orn)_n] was performed to serve as a reference of the helical portion of histones and other proteins. As is the case with pH-induced helix–coil transition, the downfield displacement of the C^α and carbonyl carbon signals are observed in the helical state. The upfield shift of the C^β signals, on the other hand, is noted in the salt-induced transition. Regardless of the differences in the side chains and also the salts used, very similar helix-induced chemical shifts are obtained for (Lys)_n and (Arg)_n. However, the displacement of the C^α, C^β, and carbonyl carbons of (Orn)n in the presence of 4M NaClO₄ is found to be almost 50% of that of (Lys)_n and (Arg)_n. This is explained by the fact that the maximum helical content is about 50%, consistent with the ORD result. Further, the motion of the backbone and side chains of the helical from was estimated by measuring the spin-lattice relaxation time (T₁), nuclear Overhauser enhancement (NOE), and line width. In the case of (Lys)_n, the motion of the side chains is charged very little in comparison with that of the random coil. Indicating that the aggregation of the salt-induced helix is small in contrast to that of the pH-induced helix. For (Arg)_n, however, the precipitate of the helical polymers is mainly due to aggregation.     

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes with an open-chain pentadentate nitrogen ligand

The open-chain, potentially, pentadentate, ligan 1,11-bis(dimethylamino)-3,6,9-trimethyl-3,6,9,-triazaundecane (Me₇tetren) forms a series of metal complexes having the general formula [M(Me₇tetren)]Y₂ (Y = 1, M = Co, Ni; Y = ClO₄, M = Co, Ni, Cu, Zn). On the basis of their physical properties, it is suggested that all these compounds contains isostructural five-coordinate [M(Me₇tetren)]²⁺ cations, the ligand acting as pentadentate. These complexes react in solution with thiocyanate ion to give mono- and, with exception of copper(II), di-thiocyanato five- and six-co-ordinate derivatives. Mono-thiocyanato derivatives of cobalt(II), nickel(II) and zinc(II) have been isolated as tetraphenylborate salts. Cobalt(II) and nickel (II) di-thiocyanato derivatives have been also isolated. Results are discussed in terms of the steric requirements of the ligand and electronic properties of the metal ions.     

Synthesis, crystal structure and spectroscopic behaviors of Co(II) and Cu(II) complexes with Salen-type bisoxime ligands

Two Salen-type ligands (H₂L¹, 4,4′-dichloro-2,2′-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol and H₂L², 4,4′-dinitro-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) and their corresponding complexes ({[CoL¹(MeOH)]₂(OAc)₂Co} · 2MeOH and [CuL²]₂) have been synthesized and characterized by element analyses, ¹H NMR, FT-IR and UV-Vis spectra, TG-DTA and single crystal X-ray crystallography. Crystallographic data suggests the octahedral geometry for Co(II) complex and square-pyramidal geometry for Cu(II) complex. Furthermore, the fluorescence behavior of Cu(II) complex in DMSO is discussed.     

Magnetic, spectroscopic, structural and biological properties of mixed-ligand complexes of copper(II) with N,N,N,N″,N″-pentamethyldiethylenetriamine and polypyridine ligands

Two new mixed ligand complexes of copper(II) with N,N,N^′,N″,N″-pentamethyldiethylenetriamine and polypyridine ligands have been prepared and characterized by means of spectroscopic, magnetic and single-crystal X-ray diffraction methods. These two complexes are isomorph and isostructure in which the coordination polyhedron about the copper(II) ion is distorted square pyramidal. [Cu(PMDT)(bipy)]²⁺ and [Cu(PMDT)(phen)]²⁺ show an absorption wavelength maximum at 625 and 678 nm, respectively, assigned to the d-d transition. Antibacterial, antifungal and superoxide dismutase activities of these complexes have also been measured. It was observed that [Cu(PMDT)(bipy)](ClO₄)₂ was more effective against P. Pyocyanea and Klebsiella sp. than S. aureus. Similarly, Fusarium sp. was highly susceptible against [Cu(PMDT)(bipy)](ClO₄)₂ but less susceptible against [Cu(PMDT)(phen)](ClO₄)₂.