Electronic Absorption Studies Research Articles

DNA binding and nuclease activity of an oxovanadium valinato-Schiff base complex

A new oxovanadium complex [VO(sal-l-val)(phen)] (sal-l-val=Schiff base derived from salicylaldehyde and l-valine; phen=1,10-phenanthroline) has been designed and synthesized with the aim of developing potential DNA nuclease. The interaction of DNA with this structurally characterized oxovanadium complex has been studied by various physicochemical tools like UV–vis, fluorescence, viscosity and circular dichroism (CD). The intrinsic binding constant of the complex with DNA is determined by electronic absorption studies and calculated to be (4.74±0.02)×105M−1. The spectroscopic studies and the viscosity measurements indicate that the complex binds calf thymus DNA (CT-DNA) by intercalative mode. The ability of the complex to induce DNA cleavage was studied by gel electrophoresis techniques. The complex has been found to promote cleavage of pUC19 plasmid DNA from the super coiled (SC) form I to nicked coiled (NC) relaxed form II with good efficiency.

Swift photoswitching in a binuclear Zn(ii) metallacycle relative to a salen-type ligand

The synthesis, characterization and photoswitching behavior of a new salen type Schiff base N,N'-bis(2-hydroxy-5-phenylazobenzilidene)-2,4,6-trimethylbenzene-1,3-diamine (H₂L) and a binuclear zinc(ii) metallacycle [{Zn(L)}2·2H2O] (1) have been described. Both H₂L and 1 have been characterized by satisfactory elemental analyses, spectral (FT-IR, (1)H, (13)C NMR, ESI-MS, electronic absorption, emission) and electrochemical studies. Crystal structures of both H₂L and 1 have been authenticated by single crystal X-ray diffraction analyses. These exhibit trans-cis photoisomerization upon exposure to UV light (365 nm) and get back to a more stable trans-form after withdrawal of the light. Electronic absorption, emission, (1)H NMR and cyclic voltammetric studies revealed that trans-cis isomerization in metallacycle 1 is rather rapid (~5.0 s) relative to H₂L (~25 s) which has been supported by theoretical studies (DFT). Relatively fast photoisomerization in 1 compared to H₂L is facilitated by a small energy gap between HOMO levels of the trans- and cis-isomers. The percentage trans-cis conversion ratio for both H₂L and 1 has been evaluated (55-45, H₂L; 60-40%, 1) by (1)H NMR studies.

Transient electronic and vibrational absorption studies of the photo-Claisen and photo-Fries rearrangements

The liquid-phase photo-Claisen and photo-Fries rearrangement dynamics of allyl phenyl ether and phenyl acetate in cyclohexane solution have been interrogated via ultrafast transient absorption spectroscopy. Following excitation at 267 nm, the reaction progress is monitored on a picosecond time-scale by electronic and vibrational absorption spectra obtained from broadband UV/Visible and mid-infrared probe pulses. The evolution of the ground and excited electronic states of the parent molecule, the radicals produced by photo-induced homolytic bond fission, and intermediate cyclohexadienones formed via recombination of the produced radical pair are followed, providing new insight and detail on the reaction mechanisms. Subsequent kinetic analysis allows determination of rate coefficients as well as quantum yields for the processes involved. These examples serve to highlight the utility of employing broadband UV-Visible and infrared probe spectroscopies, in conjunction, to unravel the mechanisms of photochemical reactions in solution. The underlying photo-physics that initiates bond fission in this class of molecules is also addressed in the context of the role of dissociative (n/π)σ* excited states.

Synthesis, CMC Determination, Antimicrobial Activity and Nucleic Acid Binding of A Surfactant Copper(II) Complex Containing Phenanthroline and Alanine Schiff-Base

A new water-soluble surfactant copper(II) complex [Cu(sal-ala)(phen)(DA)] (sal-ala = salicylalanine, phen = 1,10-phenanthroline, DA = dodecylamine), has been synthesized and characterized by physico-chemical and spectroscopic methods. The critical micelle concentration (CMC) values of this surfactant-copper(II) complex in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308, 313. 318 and 323K) served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔG(0)m, ΔH(0)m and ΔS(0)m). The interaction of this complex with nucleic acids (DNA and RNA) has been explored by using electronic absorption spectral titration, competitive binding experiment, cyclic voltammetry, circular dichroism (CD) spectra, and viscosity measurements. Electronic absorption studies have revealed that the complex can bind to nucleic acids by the intercalative binding mode which has been verified by viscosity measurements. The DNA binding constants have also been calculated (Kb = 1.2 × 10(5)M(-1) for DNA and Kb = 1.6 × 10(5)M(-1) for RNA). Competitive binding study with ethidium bromide (EB) showed that the complex exhibits the ability to displace the DNA-bound-EB indicating that the complex binds to DNA in strong competition with EB for the intercalative binding site. The presence of hydrophobic ligands, alanine Schiff-base, phenanthroline and long aliphatic chain amine in the complex were responsible for this strong intercalative binding. The surfactant-copper (II) complex was screened for its antibacterial and antifungal activities against various microorganisms. The results were compared with the standard drugs, amikacin(antibacterial) and ketokonazole(antifungal).

Functionalized Bis-Cyclometalated Alkynylgold(III) Complexes: Synthesis, Characterization, Electrochemistry, Photophysics, Photochemistry, and Electroluminescence Studies

A series of luminescent alkynylgold(III) complexes containing various tridentate bis-cyclometalating ligands derived from 2,6-diphenylpyridine (R-C(^)N(^)C), [Au(R-C(^)N(^)C)(C≡C-C6H4-R')] has been successfully synthesized and characterized. Complexes 1 and 6 have been determined by X-ray crystallography. Electrochemical studies show a ligand-centered reduction that originated from the tridentate R-C(^)N(^)C pincer ligands and an alkynyl-centered oxidation. The photophysical properties of the complexes have been studied in detail by electronic absorption and emission studies. Tunable photoluminescence behaviors have been observed, with the emission maxima spanning through the visible region from 476 to 669 nm in dichloromethane at room temperature, and the complexes were also found to be emissive in various media at both room and low temperatures. Transient absorption studies have been conducted to investigate the excited state properties of the complexes. Furthermore, selected complexes have been incorporated into the emissive layer (EML) of organic light-emitting devices (OLEDs) and have demonstrated interesting electroluminescence.

Synthesis, Characterization, and Photophysical Studies of Some Novel Ruthenium(II) Polypyridine Complexes Derived from Benzothiazolyl hydrazones

A series of five benzothiazolylhydrazone ligands 3a–3e and their seven novel Ru(II) polypyridine complexes 4a–4d, 5a, 5d, 5e of the type [Ru(N–N)2(L)]Cl2, where (N–N)2 is 2,2′-bipyridine (bpy)2 or 1,10-phenanthroline (phen)2 and (L) is ligands 3a–3e, have been synthesized and characterized by elemental analysis, IR, 1H NMR, electronic absorption, and emission spectral studies. The interpretation of the analytical data revealed that the ligands coordinate with the metal ion in a bidentate fashion through azomethine nitrogen and phenolic oxygen to form complexes. These ligands and complexes also exhibit absorption and luminescence properties.

Keys for the Existence of Stable Dimers of Bis-tetrathiafulvalene (bis-TTF)-Functionalized Molecular Clips Presenting [TTF]•+···[TTF]•+Long, Multicenter Bonds at Room Temperature

A systematic theoretical and computational investigation is performed to determine the keys governing the existence, in acetonitrile solutions, of dimers of bis-tetrathiafulvalene (bis-TTF)-functionalized diphenylglycoluril molecular clips (clip2(n+)) that are stable at room temperature for n ≤ 4. Although the experimental structure of these dimers in solution is unknown, electronic absorption studies suggest that they have [TTF](l+)···[TTF](m+) interactions that are preserved at room temperature (note that when l = m = 1 these interactions become long, multicenter bonds). In good agreement with the interpretation of the experimental spectroscopic data, all clip2(n+) dimers whose charge is ≤4 present an optimum geometry that, in all cases, has three short interfragment [TTF](l+)···[TTF](m+) interactions. The computed ΔG(298 K) for these optimum structures matches the available experimental data on the stability of these dimers. Such optimum geometry, combined with the zwitterionic character of the electron distribution in monomers and dimers (most of the net positive charge is equally distributed among the TTF groups, while a 1- au charge is located in the central fused five-membered rings) allows the formation of a maximum of two long, multicenter [TTF](•+)···[TTF](•+) bonds when all TTF groups host a 1+ au of charge, as in clip2(4+). However, these long, multicenter bonds alone do not account for the stability of clip2(n+) dimers at room temperature. Instead, the studies carried out here trace the origin of their stability to (1) the zwitterionic character of their charge distribution, (2) the proper geometrical shape of the interacting monomers, which allows the intercalation of their arms, thus making possible the simultaneous formation of two short contacts, both involving the positively charged TTF group of one monomer and the negatively charged central ring of the other, (3) the simultaneous presence of three short contacts among the TTF groups in the optimum geometry of the clip2(n+) dimers, which become two long, multicenter bonds and one van der Waals interaction when the four TTF groups host a 1+ charge, and (4) the net stabilizing effect of the solvent.

Ultrafast optical nonlinearity, electronic absorption, vibrational spectra and solvent effect studies of ninhydrin

FT-IR, FT-Raman and UV–Vis spectra of the nonlinear optical molecule ninhydrin have been recorded and analyzed. The equilibrium geometry, bonding features, and harmonic vibrational wavenumbers have been investigated with the help of B3LYP density functional theory method. A detailed interpretation of the vibrational spectra is carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Solvent effects have been calculated using time-dependent density functional theory in combination with the polarized continuum model. Natural bond orbital analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule. Employing the open-aperture z-scan technique, nonlinear optical absorption of the sample has been studied in the ultrafast and short-pulse excitation regimes, using 100fs and 5ns laser pulses respectively. It is found that ninhydrin exhibits optical limiting for both excitations, indicating potential photonic applications.

Correlation of photobleaching, oxidation and metal induced fluorescence quenching of DNA-templated silver nanoclusters

Few-atom noble metal nanoclusters have attracted a lot of interest due to their potential applications in biosensor development, imaging and catalysis. DNA-templated silver nanoclusters (AgNCs) are of particular interest as different emission colors can be obtained by changing the DNA sequence. A popular analytical application is fluorescence quenching by Hg(2+), where d(10)-d(10) metallophilic interaction has often been proposed for associating Hg(2+) with nanoclusters. However, it cannot explain the lack of response to other d(10) ions such as Zn(2+) and Cd(2+). In our effort to elucidate the quenching mechanism, we studied a total of eight AgNCs prepared by different hairpin DNA sequences; they showed different sensitivity to Hg(2+), and DNA with a larger cytosine loop size produced more sensitive AgNCs. In all the cases, samples strongly quenched by Hg(2+) were also more easily photobleached. Light of shorter wavelengths bleached AgNCs more potently, and photobleached samples can be recovered by NaBH4. Strong fluorescence quenching was also observed with high redox potential metal ions such as Ag(+), Au(3+), Cu(2+) and Hg(2+), but not with low redox potential ions. Such metal induced quenching cannot be recovered by NaBH4. Electronic absorption and mass spectrometry studies offered further insights into the oxidation reaction. Our results correlate many important experimental observations and will fuel the further growth of this field.

Mixed (phthalocyanine)(Schiff-base) terbium(iii)–alkali metal(i)/zinc(ii) complexes: synthesis, structures, and spectroscopic properties

A series of five mixed (phthalocyanine)(Schiff-base) terbium(III)–alkali metal(I) complexes, Li(Pc)Tb(L)(CH3OH)2·(THF) (1) and M(Pc)Tb(L)(CH3OH) (M = Na, K, Rb, Cs) (2–5), have been synthesized and isolated from the reaction between a metal free Schiff-base ligand of N,N′-bis(3-methyloxysalicylidene)benzene-1,2-diamine (H2L) and a half-sandwich phthalocyaninato terbium compound M(Pc)(acac) (H2Pc = metal free phthalocyanine, Hacac = acetylacetone) with the help of a corresponding alkali ion. The sandwich nature, with a mixed phthalocyanine and Schiff-base ligand, of the whole series of five compounds has been unambiguously revealed on the basis of single crystal X-ray diffraction analysis. Electronic absorption and luminescence spectroscopic studies, in particular the titration of 1–5 in mixed methanol/tetrahydrofuran with an equivalent amount of Zn(II) ions, leads to almost the same electronic absorption and luminescence spectra, suggesting the replacement of the alkali metal(I) ion locating at the O4 cavity of the Schiff-base ligand by a Zn(II) ion. This is confirmed by the X-ray diffraction analysis result for single crystals of the novel mixed (phthalocyanine)(Schiff-base) terbium(III)–zinc(II) complex Zn(Pc)Tb(L)(Py)2(NO3)·(CH3OH)2·(THF) (6) obtained from the reaction of K(Pc)Tb(L)(CH3OH) (3) with an excess amount of zinc nitrate in the presence of pyridine (Py). The present results will certainly attract interest for the design, synthesis, and further functional exploration of novel sandwich-type rare earth complexes involving tetrapyrrole and other macrocyclic ligands.

Electronic absorption study on hydration, solvation behavior for some keto and thioketo pyrimidine derivatives

In this study, the hydration and solvation properties of recently synthesized 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-one, (I) and 5-benzoyl-1-(methylphenylmethyleneamino)-4-phenyl-1H-pyrimidine-2-thione, (II), were studied with respect to pH and time by using UV–vis spectroscopy method in aqueous (95.0% v/v water) and methanol (95.0% v/v methanol) media. The roles of the keto oxygen of I and the thioketo sulfur of II on the hydration and solvation behavior were discussed. The experiments were performed at 25°C and at pH values between 1.0 and 13.0.Compound I was found to undergo hydration best in strongly acidic solutions. However, compound II was found to undergo solvation best in basic solutions. The preferred hydration and solvation mechanisms were discussed based on UV–vis data and the related mechanisms undergoing in strongly acidic and basic regions were proposed for the each compound.

Vanadocene de Novo: Spectroscopic and Computational Analysis of Bis(η5-cyclopentadienyl)vanadium(II)

The magnetic and electronic properties of the long-known organometallic complex vanadocene (VCp2), which has an S = 3/2 ground state, were investigated using conventional (X-band) electron paramagnetic resonance (EPR) and high-frequency and -field EPR (HFEPR), electronic absorption, and variable-temperature magnetic circular dichroism (VT-MCD) spectroscopies. Frozen toluene solution X-band EPR spectra were well resolved, yielding the 51V hyperfine coupling constants, while HFEPR were also of outstanding quality and allowed ready determination of the rigorously axial zero-field splitting of the spin quartet ground state of VCp2: D = +2.836(2) cm–1, g⊥ = 1.991(2), g∥ = 2.001(2). Electronic absorption and VT-MCD studies on VCp2 support earlier assignments that the absorption signals at 17 000, 19 860, and 24 580 cm–1 are due to ligand-field transitions from the 4A2g ground state to the 4E1g, 4E2g, and 4E1g excited states, using symmetry labels from the D5d point group (i.e., staggered VCp2). Contributions to...

Controlling the Chiral Inversion Reaction of the Metallopeptide Ni-Asparagine-Cysteine-Cysteine with Dioxygen

Synthetically generated metallopeptides have the potential to serve a variety of roles in biotechnology applications, but the use of such systems is often hampered by the inability to control secondary reactions. We have previously reported that the Ni(II) complex of the tripeptide LLL-asparagine-cysteine-cysteine, LLL-Ni(II)-NCC, undergoes metal-facilitated chiral inversion to dld-Ni(II)-NCC, which increases the observed superoxide scavenging activity. However, the mechanism for this process remained unexplored. Electronic absorption and circular dichroism studies of the chiral inversion reaction of Ni(II)-NCC reveal a unique dependence on dioxygen. Specifically, in the absence of dioxygen, the chiral inversion is not observed, even at elevated pH, whereas the addition of O(2) initiates this reactivity and concomitantly generates superoxide. Scavenging experiments using acetaldehyde are indicative of the formation of carbanion intermediates, demonstrating that inversion takes place by deprotonation of the alpha carbons of Asn1 and Cys3. Together, these data are consistent with the chiral inversion being dependent on the formation of a Ni(III)-NCC intermediate from Ni(II)-NCC and O(2). The data further suggest that the anionic thiolate and amide ligands in Ni(II)-NCC inhibit Cα-H deprotonation for the Ni(II) oxidation state, leading to a stable complex in the absence of O(2). Together, these results offer insights into the factors controlling reactivity in synthetic metallopeptides.

Heteroleptic Dipyrrinato Complexes Containing 5-Ferrocenyldipyrromethene and Dithiocarbamates as Coligands: Selective Chromogenic and Redox Probes

Six heteroleptic dipyrrinato complexes [Ni(fcdpm)(dedtc)] (1), [Ni(fcdpm)(dipdtc)] (2), [Ni(fcdpm)(dbdtc)] (3), [Pd(fcdpm)(dedtc)] (4), [Pd(fcdpm)(dipdtc)] (5), and [Pd(fcdpm)(dbdtc)] (6) (fcdpm = 5-ferrocenyldipyrromethene; dedtc = diethyldithiocarbamate; dipdtc = diisopropyldithiocarbamate; dbdtc = dibutyldithiocarbamate) have been synthesized and characterized by elemental analyses and spectral (ESI-MS, IR, (1)H, (13)C NMR, UV-vis) and electrochemical studies. Crystal structures of 1, 2, 4, and 5 have been authenticated by X-ray single-crystal analyses. Nickel-based complexes 1-3 display selective chromogenic and redox sensing for Hg(2+) and Pb(2+) ions, while palladium complexes 4-6 display selective chromogenic and redox sensing only for Hg(2+). Electronic absorption, ESI-MS, and electrochemical studies indicated that sensing arises from interaction between 1-3 and Hg(2+)/Pb(2+) through sulfur of the coordinated dithiocarbamates, while it arises from the pyrrolic nitrogen of fcdpm and dithiocarbamate sulfur from 4-6 and Hg(2+). Different modes of binding between Ni and Pd complexes have further been supported by theoretical studies. The receptor-cation binding constants (K(a)) and stoichiometry between probes and Hg(2+)/Pb(2+) have been estimated by the Benesi-Hildebrand method and Job's plot analysis. Detection limits for 1-3 toward Hg(2+)/Pb(2+) and 4-6 for Hg(2+) have been found to be reasonably high.

Hybrid density functional study on SrTiO3 for visible light photocatalysis

Hybrid Density Functional calculations have been performed on the electronic structure of anionic mono- (S, N, P, and C) and co-doped (N–N, N–P, N–S, P–P) SrTiO3 to improve their visible light photocatalytic activity. The electronic band position of doped system has been aligned with respect to the water oxidation/reduction potential. The electronic band position and optical absorption study shows that the mono- (S) and co-doped (N–N, N–P and P–P) SrTiO3 systems are promising materials for the visible-light photocatalysis. The calculated binding energies show that the co-doped systems are more stable than their respective mono-doped systems.

Synthesis, characterization and catechol oxidase biomimetic catalytic activity of cobalt(II) and copper(II) complexes containing N2O2 donor sets of imine ligands

New tetradentate imine ligands are derived from Schiff base condensation in a 1:2 molar ratio of the 1,2,4,5-tetra-amino benzene with 2-hydroxy benzaldehyde, (L1), 2,4-dihydroxy benzaldehyde (L2) and 2-hydroxy naphthaldehyde (L3). These ligands react with CoCl2 and CuCl2 in refluxing ethanol to yield a series of cobalt(II) and copper(II) complexes of the type [M2IILn] nH2O. The structure of the obtained ligands and their metal(II) complexes were characterized by various physicochemical techniques, viz. elemental analysis, molar conductance, magnetic susceptibility measurements, thermal analysis (TGA & DTG), IR, electronic absorption and ESR spectral studies. Four-coordinate tetrahedral and square–planar structures were proposed for cobalt(II) and copper(II) complex species respectively. The ability of the synthesized complexes to catalyze the aerobic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to the light absorbing 3,5-di-tert-butylquinone (3,5-DTBQ) has been investigated. The results obtained show that all complexes catalyze this oxidation reaction and slight variations in the rate were observed. The probable mechanistic implications of the catalytic oxidation reactions are discussed.

Syntheses, X-ray Crystal Structures, and Optical, Fluorescence, and Nonlinear Optical Characterizations of Diphenylphosphino-Substituted Bithiophenes

A series of bithiophene derivatives that are either symmetrically disubstituted with two Ph(2)(X)P groups (X = O, S, Se) or monosubstituted with one Ph(2)(X)P group (X = O, S, Se) and an organic functional group (H, CHO, CH(2)OH, CO(2)Me) have been synthesized. The X-ray crystal structures of Ph(2)(Se)P(C(4)H(2)S)(2)P(Se)Ph(2), Ph(2)(O)P(C(4)H(2)S)(2)H, Ph(2)(S)P(C(4)H(2)S)(2)H, and Ph(2)(O)P(C(4)H(2)S)(2)CH(2)OH exhibit very different solid-state structures depending on the type of intermolecular π-π interactions that occur. The compounds have been characterized by electronic absorption and fluorescence studies. Of particular interest is that the quantum yields of Ph(2)(O)P(C(4)H(2)S)(2)H, Ph(2)(O)P(C(4)H(2)S)(2)P(O)Ph(2), Ph(2)(O)P(C(4)H(2)S)(2)CO(2)Me, and Ph(2)(O)P(C(4)H(2)S)(2)CH(2)OH are significantly larger than that of bithiophene (factors of 13, 14, 14, and 22, respectively). This behavior is quite different from that of analogously substituted terthiophenes in which substitution results in only modest increases in the quantum yields over that of terthiophene (factors of 0.94, 2.7, 1.3, and 1.5, respectively). DFT studies of the emission process suggest that modifying the Ph(2)(X)P group affects both the fluorescence and nonradiative rate constants while modifications of the organic substituents primarily affect the nonradiative rate constants. The higher quantum yields of the substituted bithiophenes make them promising for application in organic light-emitting devices (OLED). The optical power limiting (OPL) performances of these Ph(2)(X)P-substituted bithiophenes were evaluated by nonlinear transmission measurements in the violet-blue spectral region (430-480 nm) with picosecond laser pulses. The OPL performances are enhanced by heavier X groups and when by higher solubilities. Saturated chloroform solutions of Ph(2)(O)P(C(4)H(2)S)(2)H and Ph(2)(S)P(C(4)H(2)S)(2)H exhibit significantly stronger nonlinear absorption than any previously reported compounds and are promising candidates for use in broadband optical power limiters.

Synthesis, characterization, magnetic, thermal and electrochemical studies of oxidovanadium (IV) picolyl hydrazones as functional catechol oxidase models

Abstract The picolyl hydrazone ligands derived from picolonic acid hydrazide and α-pyridyle ketone (L 1 , L 2 and L 3 ), α-acetyl thiophene (L 4 ), α-formyl or α-acetyl phenol (L 5 and L 6 respectively) and 2-hydroxy-1-naphthaldehyde (L 7 ) react with equimolecular amount of vanadyl sulfate in refluxing methanol to yield oxidovanadium (IV) complexes. The structure of the obtained ligands and their oxidovanadium (IV) complexes were characterized by various physicochemical techniques, viz. elemental analysis, molar conductance, magnetic susceptibility measurements, thermal analysis (TGA & DTG), IR, electronic absorption and ESR spectral studies. Cyclic voltammeteric behavior of the complexes has also been discussed. Five-coordinate square-pyramidal structure was proposed for all complexes. A monomeric nature was reported for complexes (2) , (3) , (6) , and (7) , while dimeric structures were suggested for complexes (1) , (4) and (5) . The ability of the complexes to catalyze the aerobic oxidation of catechol to the light absorbing o -quinone has been investigated. The results obtained show that all complexes catalyze this oxidation reaction and large variations in the rate were observed. Electrochemical data for most complexes show that there is a linear relationship between their ability to oxidize catechole and their E 1/2 potentials. The most effective catalysts were those complexes which exhibited E 1/2 values approached to the E° value of the natural tyrosinase enzyme isolated from mushroom, while those that largely deviated from that potential exhibited lower oxidase catalytic activity. The probable mechanistic implications of the catalytic oxidation reactions are discussed.

Synthesis, spectroscopic, powder X-ray diffraction and DNA binding studies on copper(II) complexes of 4,4′-diaminodiphenyl sulfone

Four new Cu(II) complexes of 4,4′-diaminodiphenyl sulfone (DDS) with different anions (chloride, sulfate, nitrate or acetate) were synthesized and characterized by elemental analysis, electronic absorption, IR, magnetic moment, thermal analysis and powder X-ray diffraction studies. It was found that the pure DDS and complex [Cu2(DDS)2(NO3)2].(NO3)2 (3) crystallize in orthorhombic system while the complexes [Cu2(DDS)2].Cl4 (1), [Cu2(DDS)2].(SO4)2 (2), and [Cu2(DDS)2].(CH3COO)4 (4) crystallize in monoclinic system. The crystallite sizes of complexes have smaller values as compared to pure DDS. Infrared studies suggest that the coordination of NH2 of DDS with Cu(II) ion. The binding of the complexes with calf thymus (CT) DNA was investigated by electronic absorption titration, fluorescence measurements and DNA thermal denaturation. The spectroscopic studies together with the DNA melting studies indicated that the complexes may bind to CT-DNA in a non-intercalative mode.

Studies on nickel (II) and palladium (II) complexes with some tetraazamacrocycles containing tellurium

The synthesis of 10-membered and 12-membered tellurium containing tetraazamacrocyclic complexes of divalent nickel and palladium by template condensation of diaryltellurium dichlorides, (aryl = p-hydroxyphenyl, 3-methyl-4-hydroxyphenyl, p-methoxyphenyl) with 1,2-diaminoethane and 1,3-diaminopropane in the presence of metal dichloride is reported. The resulting complexes have been subjected to elemental analyses, magnetic measurements, electronic absorption, infra-red, and proton magnetic resonance spectral studies. The formation of proposed macrocyclic skeletons and their donor sites have been identified on the basis of spectral studies. Distorted octahedral structure for the nickel complexes in the solid state and squareplanar structure for the palladium complexes have been suggested.