The dynamics of (57)Fe nuclei in Fe(III)-DNA condensates.

Abstract The dynamics of iron nuclei in the condensates obtained by interaction of Fe III with DNA, Fe III (DNA monomer) 2 , have been investigated by variable temperature 57 Fe Mossbauer spectroscopy. Studies were effected on gel and freeze-dried samples, obtaining nearly coincident values of the parameters isomer shift and nuclear quadrupole splitting in T ranges 20–260 K. Functions ln( A T / A 77.3 ) vs. T , here employed to investigate the dynamics of Fe nuclei, showed linear trends in the T ranges 20–150 and 150–260 K, respectively, the latter with larger slopes. Data coincided for gelled and freeze-dried specimens. No variation of δ or Δ E parameters occurred at the two T intervals, w…

Synthesis and structural characterisation of copper(I,II) complexes mimetic of "blue copper" proteins active site

The interaction of native calf thymus DNA with FeIII-dipyrido[3,2-a:2’,3’-c]phenazine

The mono and bis dipyrido[3,2-a:2',3'-c]phenazine (dppz) adducts of iron(III) chloride, i.e. [Fe(dppz)]Cl(3) and [Fe(dppz)(2)]Cl(3), have been synthesized and characterized. The interaction of the Fe(III)dppz hydrolyzed aquo complex with native calf thymus DNA has been monitored as a function of the metal complex-DNA molar ratio, by variable temperature UV absorption spectrophotometry, circular dichroism (CD) and fluorescence spectroscopy. The results obtained in solution at various ionic strength values give support for a tight intercalative binding of the Fe(III)dppz cation with DNA. In particular, the appearance of induced CD bands, caused by the addition of Fe(III)dppz, indicate the exi…

Confinement effects on the interactions of native DNA with Cu(II)-5-triethyl ammonium methyl salicylidene orto-phenylendiiminate in C12E4 liquid crystals

Confinement effects of native calf thymus DNA interacting with the complex Cu(ii)-5-(triethylammoniummethyl)salicylidene ortho-phenylendiiminate (CuL(2+)) perchlorate in tetraethylene glycol monododecyl ether (C(12)E(4)) liquid crystals have been investigated by UV absorption spectrophotometry, circular dichroism (CD) and small angle X-ray scattering (SAXS). The results indicate the occurrence of dramatic structural changes of both the DNA and the CuL(2+)-DNA system, when going from aqueous solution to C(12)E(4) liquid crystals, due to confinement constrains imposed by the closed structure of C(12)E(4) reverse micelles. Further marked departures from the behaviour observed in aqueous soluti…

Complexes of Tin(IV) with Tridentate Ligands M�SSBAUER, Infrared, and Solution Phase Studies

The configuration in the solid state and in solution phase of complexes of SuIV wit,li tridentate “planar” ligands, Sn(trid)2 and HNEt3Cl3 Sntrid, have been investigated by infrared and MOSSBAUER spectroscopy, as well as by osmometry, conductivity, and electronic and PMR spectroscopy. The presence of monomeric Sn(trid)2 and ionic [HNEt] [Cl3Sn trid−] species has been inferred. Octahedral type configurations are advanced for both classes of compounds. Komplexe des Zinn (IV) mit dreizahigen Liganden. Mossbauer- und IR-Spektren sowie Untersuchungen von Losungen Die Struktur von SnIV-Komplexen mit dreizahnigen “planaren” Liganden, Sn(trid)2 und HNEt3Cl2Sntrid, wurde in fester Phase und in Losun…

Infrared and M�SSBAUER spectroscopic studies on complexes of Hal2SnIV moieties with tridentate ligands

Novel complexes hal2Sntrid, where hal Cl, Br, and trid2− are dianions of „planar” tridentate ligands with ONO and SNO donor basic atoms, were synthesized and structurally investigated in the solid state mainly by far infrared and MOSSBAUER spectroscopy. Possible configurations were advanced and discussed, and it was concluded that the most probable is a monomeric trigonal bipyramidal structure for all compounds, although polymers, or dimers with O or Cl bridges, were not a priori excluded, in a special way for Br2Sntrid. Infrarot- und MOSSBAUER-spektroskopische Untersuchungen an Komplexen von Hal2SnIV mit dreizahnigen Liganden Neue Komplexverbindungen von Typ hal2Sntrid werden dargestellt (…

DFT computational study on Fe(III)-N,N′-ethylene-bis(salicylideneiminato) derivatives

DFT calculations, at unrestricted B3LYP level, have been performed on the structures of three iron(III) complexes, Fe(Salen)Cl, [Fe(Salen)]+ and [Fe(Salen)OH2]+, where Salen is the anion of Schiff base ligand N,N′-ethylene-bis (salicylideneimine), considering the spin multiplicity (S) values 2, 4 and 6. The results obtained have been compared with the available structural an magnetic experimental data, allowing us to conclude that a stable form of the FeIII(Salen) complex in aqueous solution should be characterized by an energy stabilization of the S=4 compared to the S=6 state.

The interaction of native DNA with iron(III)- N ,N'-ethylene-bis(salicylideneiminato)-chloride.

Abstract The interaction between native calf thymus deoxyribonucleic acid (DNA) and Fe III - N , N ′ -ethylene-bis (salicylideneiminato)-chloride, Fe(Salen)Cl, was investigated in aqueous solutions by UV–visible (UV–vis) absorption, circular dichroism (CD), thermal denaturation and viscosity measurements. The results obtained from CD, UV–vis and viscosity measurements exclude DNA intercalation and can be interpreted in terms of an electrostatic binding between the Fe(Salen) + cation and the phosphate groups of DNA. The trend of the UV–vis absorption band of the Fe(Salen)Cl complex at different ratios [DNA phosphate ]/[Fe(Salen)Cl] and the large increase of the melting temperature of DNA in …

Computational study of the interaction of proflavine with d(ATATATATAT)2 and d(GCGCGCGCGC)2

Abstract The interaction of proflavine (PR) with two B-DNA decamers of alternating AT and GC sequence, called [deca(dG-dC)]2 and [deca(dA-dT)]2, respectively, was computationally investigated by the ONIOM method, exploiting a three-layer QM/QM/MM hybrid approach. The highest level QM method was applied to the model system, which comprises the intercalation site (5th and 6th base pairs) and the inserted PR molecule. The connecting sugar phosphate backbone was added in the medium layer region. Both higher and medium level layers, differing in the size of the basis set used, were treated by the DFT MPWB1K functional. The full system in the lower layer was described by the empirical AMBER force…

Tin-DNA complexes investigated by nuclear inelastic scattering of synchrotron radiation

Nuclear inelastic scattering (NIS) of synchrotron radiation has been used to investigate the dynamics of tin ions chelated by DNA. Theoretical NIS spectra have been simulated with the help of density functional theory (DFT) calculations using 12 models for different binding sites of the tin ion in (CH3)Sn(DNAPhosphate)2. The simulated spectra are compared with the measured spectrum of the tin-DNA complex.

Studi spettroscopici su complessi indolotriazolopirimidina-DNA nativo.

Structure Validation of Natural Products by Quantum-Mechanical GIAO Calculations of 13C NMR Chemical Shifts GIAO=gauge including atomic orbitals.

Geometry optimization and GIAO (gauge including atomic orbitals) 1 3 C NMR chemical shift calculations at Hartree-Fock level, using the 6-31G(d) basis set, are proposed as a tool to be applied in the structural characterization of new organic compounds, thus providing useful support in the interpretation of experimental NMR data. Parameters related to linear correlation plots of computed versus experimental 1 3 C NMR chemical shifts for fourteen low-polar natural products, containing 10-20 carbon atoms, were employed to assess the reliability of the proposed structures. A comparison with the hybrid B3LYP method was carried out to evaluate electron correlation contributions to the calculatio…

Pirazolo[3,4-d][1,2,3]triazolo[1,5-a]pirimidina: accesso sintetico tramite cicloaddizioni 1,3-dipolari e riarrangiamento di Dimroth

THE INTERACTION OF NATIVE DNA WITH Ni(II), Cu(II) and Zn(II) COMPLEXES OF 5-TRIETHYL AMMONIUM METHYL SALICYLIDENE ORTHO-PHENYLENDIIMINE

Bis(triorganometal) and diorganometal 1,3-dithiolates (R3M)2(C6H3XS2) and R2M(C6H3XS2) (M = Sn, Pb; X= H, Cl)

Abstract Bis(triorganometal) and diorganometal 1,3-dithiolates (R3M)2(C6H3XS2) (C6H5XS2 1,3-dithiobenzene (for X = H) or 1,3-dithio-4-chlorobenzene (for X = Cl); M = Sn, X = Cl, R = CH3, C6H5; M = Pb, X = H, Cl, R = CH3, C2H5) and R2M(C6H3XS2) (R = CH3, C2H5, C6H5; M = Sn, X = Cl; M = Pb, X = H, Cl) have been prepared as the first organometal IVB derivatives of 1,3-dithiols, and investigated by vibrational, 1H NMR, and (in the case of organotin compounds) Mossbauer spectroscopy. The triorganometal derivatives are monomeric and the diorganometal derivatives dimeric in solution (37° C). For the latter a twelve-membered ring structure is proposed for both solution and the solid state.

Complexes of organometallic compounds. XLVI. Synthesis of adducts formed by organotin(IV) trichlorides with 1,2-bis(diphenylphosphino)ethane, and their characterization by mössbauer and infrared spectroscopy

Abstract Adducts between RSnCl 3 (R = Me, Bu n , Oct n , Ph) and 1,2-bisz(diphenylphosphino)ethane, DPE, have 1:1 composition. In Mossbauer spectroscopic experiences at variable absorber temperature the area under the resonant peaks, A, has been measured for RSnCl 3 ·DPE, R = Me, Ph; slopes plots of in A vs. T suggest strong coupling between Mossbauer atoms, which has been interpreted in terms of solid state polymeric structures, due to DPE acting as a bridging bis-monodentate ligand. Infrared data indicate the covalency of SnCl bonds. Three possible structural isomers of octahedral type are then proposed, one having trans -P 2 and two cis -P 2 atoms. A choice between these structures has …

Spectroscopic study of the interaction of Ni(II)-5-triethyl ammonium methyl salicylidene ortho-phenylendiiminate with native DNA.

The interaction of native calf thymus DNA with the cationic Ni(II) complex of 5-triethyl ammonium methyl salicylidene ortho-phenylendiimine (NiL(2+)), in 1mM Tris-HCl aqueous solutions at neutral pH, has been monitored as a function of the metal complex-DNA molar ratio by UV absorption spectrophotometry, circular dichroism (CD) and fluorescence spectroscopy. The dramatic modification of the DNA CD spectrum, the appearance of a broad induced CD band in the range 350-400nm, the strong increase of the DNA melting temperature (T(m)) and the fluorescence quenching of ethidium bromide-DNA solutions, in the presence of increasing amounts of the NiL(2+) metal complex, support the existence of a tig…

Complexes of organometallic compounds. LI. The correlation between 119Sn Mössbauer isomer shifts and partial atomic charges on tin in R3SnL compounds

Abstract The 119Sn Mossbauer isomer shift parameters, δ, of compounds R3SnL (R = AlK, Ph; L = F, Cl, OH, OR′, CN, NCS, NCO, N3) have been correlated to partial atomic charges on tin QSn, calculated according to a valence state electronegativity equalization procedure carried out by the CHELEQ program. A unique δ/QSn correlation has been obtained for all the five-coordinated R3SnL species by using average δ parameters for the AlK3IV derivatives.

The structure and dynamics of Cl-substituted tetraphenyl- and tetrabenzyl-tin(IV)

Abstract The crystal and molecular structure of (o-ClC6H4CH2)4Sn has been determined by X-ray crystallography. Tin is in a slightly distorted environment. The molecular dynamics of (p-ClC6H4)4Sn, (o-ClC6H4)4Sn and (o-ClC6H4CH2)4Sn have been investigated by variable temperature 119Sn Mossbauer spectroscopy (VTMS). A Debye-solid behaviour has been detected for (p-ClC6H4)4Sn, where, on the other hand, no influence by hydrogen–chlorine interaction on the magnitude of the dynamics data and functions seems to occur. For the o-Cl-substituted derivatives, a non-Debye-solid character could be advanced.

Dynamics of Metal Centers Monitored by Nuclear Inelastic Scattering

Nuclear inelastic scattering of synchrotron radiation has been used now since 10 years as a tool for vibrational spectroscopy. This method has turned out especially useful in case of large molecules that contain a M\"ossbauer active metal center. Recent applications to iron-sulfur proteins, to iron(II) spin crossover complexes and to tin-DNA complexes are discussed. Special emphasis is given to the combination of nuclear inelastic scattering and density functional calculations.

Tin(IV), Monomethyltin(IV), and Dimethyltin(IV) Complexes with thiol sulfur and heterocyclic nitrogen donors: Molecular dynamics and structure by119Sn m�ssbauer spectroscopy

The molecular dynamics of the complexes Sn(SPyN)4 (1), SnCl2(SPyN)2 (2), MeSn(SPy)3 (3), MeSnCl(SPyN)2 (4), Me2Sn(TCy)2 (5), Me2SnCl(TOx) (6), and Me2Sn(TUr) (7) [HSPy = 2-mercaptopyridine; HSPyN = 2-mercaptopyrimidine; HTCy = 2-thiocytosine; HTOx = 8-thioquinoline; H2TUr = 2-thiouracil] has been investigated by variable temperature 119Sn Mossbauer spectroscopy. The area under the resonant peaks has been determined as function of temperature, from which Debye temperatures and cut-off frequencies, as well as recoil-free fractions (Lamb Mossbauer factor) and mean square displacements of 119Sn, have been calculated. By fingerprint procedures on the basis of literature data, monomeric structure…

DFT calculations of the electric field gradient of tin compounds: a structure elucidation tool by 119Sn Mossbauer spectroscopy.

Determination of the Relative Stereochemistry of Flexible Organic Compounds by Ab Initio Methods: Conformational Analysis and Boltzmann-Averaged GIAO 13C NMR Chemical Shifts GIAO=gauge including atomic orbitals.

Ab initio calculations at the Hartree-Fock level with full-geometry optimization using the 6-31G(d) basis set, and GIAO (gauge including atomic orbitals) 1 3 C NMR chemical shifts, are presented here as a support in the study of the stereochemistry of low-polar organic compounds having an openchain structure. Four linear stereoisomers, fragments of a natural product previously characterized by experimental 1 3 C NMR spectra, which possesses three stereogenic centers, 11 carbon atoms, and 38 atoms in total, were considered. Conformational searches, by empirical force-field molecular dynamics, pointed out the existence of 8-13 relevant conformers per stereoisomer. Thermochemical calculations …

The interaction of organotins with native DNA

The compounds R2SnCl2 and R3SnCl (RMe, Et, nBu, nOct, Ph, in ethanol solution) as well as the aqueous species [Me2Sn(OH2)n]2+ and [Me3Sn(OH2)2]+, react with aqueous native DNA, yielding solid phases. According to the pointcharge model treatment of the 119Sn Mossbauer parameter nuclear quadrupole splitting, trans-octahedral R2Sn(O2PXY)2, and trigonalbipyramidal R3Sn(O2PXY), (RMe, Et, nBu), would occur in the pellets, the tin atoms being coordinated by phosphodiester groups of the nucleic acid. The precipitates from Ph2SnIV would consist of the DNA complex as well as of the Ph2SnIV distannoxane obtained by hydrolysis of the reactant, whilst nOct2SnCl2, nOct3SnCl and Ph3SnCl would mainly yield…

The interaction of native calf thymus DNA with Fe(III)- dipyrido[3,2-a:2’,3’-c]phenazine chloride

Synthesis of copper(II) complexes of new carbon-scorpionate ligands

A set of new “carbon-based” scorpionate ligands based on S- and N-containing heterocyclic moieties have been synthesized. They offer the advantage of a higher stability with respect to the “classical” boron-based scorpionate ligands and also a certain degree of hydrophilicity. The synthesis of these ligands was accomplished by the coupling reaction of the N-methylimidazolyllithium with a suitable electrophilic partner. The reaction yield ranges from 40% to 65%. Preliminary results on the synthesis and characterization of the related copper(II) complex are also presented.

Relationship between XPS core binding energies and atomic charge in adducts of SnIV derivatives with pyrazine, and comparison with mössbauer isomer shift data

Abstract Adducts Snhal·pyz (hal = Cl, Br, I; pyz = pyrazine), RnSnCl 4−n ·pyz (n = 1, R = Me, Bu n , Oct n , Ph; n = 2, R = Ph) and SnCl 4 ·(pyz) 2 have been investigated by X-ray photoelectron spectroscopy. Binding energy (b.e.) values are discussed in the light of structural characteristics of the adducts as well as of valence state electronegativities of atoms and groups bound to tin. Sn 3d 5 2 b.e.s, corrected for the Madelung potential at the metal atom, linearly correlate with both partial atomic charges on tin, accounting for relaxation upon ionization, and 119 Sn Mossbauer isomer shifts. The results are interpreted in terms of six-coordinated, octahedral type, configurations of the …

Synthesis and structural characterization of new Bis(pyrazolyl)thioimidazolyl)borate ligands [NNS] donor and their relate complexes

Interactions of organotins with biological systems

The bonding and structure in the environments of tin atoms in organotin-biological molecules has been investigated by 119Sn Mossbauer spectroscopy, mainly through the rationalization of the nuclear quadrupole splitting parameter by pointcharge model approaches. Organotin moieties R2SnIV and R3SnIV (R = Me, nBu, Ph) generally assume trigonal-bipyramidal type configurations in membranes of human erythrocytes, when incubated with whole erythrocytes and erythrocyte ghosts at the level of micromolar (μmol dm−3) organotin per mg of membrane protein. Corresponding structures are assumed by Me2SnIV and Me3SnIV in the cytoplasm. Ethanolic Me2SnCl2 yielded distorted trans-octahedral species when reac…

Fluorescence emission and enhanced photochemical stability of Zn(II)-5-triethyl ammonium methyl salicylidene ortho-phenylendiiminate interacting with native DNA.

Abstract The photophysical and photochemical properties of the cationic Zn II complex of 5-triethyl ammonium methyl salicylidene ortho-phenylendiimine (ZnL 2+ ) interacting with native DNA were investigated by steady state and time-resolved fluorescence spectroscopies. Experimental results indicate that, in the presence of DNA, ZnL 2+ is efficiently protected from a photochemical process, which occurs when it is in the free state dispersed in aqueous solution. The analysis of the absorption and emission spectra of ZnL 2+ , both stored in the dark and after exposure to tungsten lamp light for 24 h, corroborated by quantum chemical calculations, allowed us to point out that ZnL 2+ undergoes a…

The interaction of native DNA with Zn(II) and Cu(II) complexes of 5-triethyl ammonium methyl salicylidene orto-phenylendiimine

The interaction of native calf thymus DNA with the Zn(II) and Cu(II) complexes of 5-triethyl ammonium methyl salicylidene orto-phenylendiimine (ZnL(2+) and CuL(2+)), in 1 mM Tris-HCl aqueous solutions at neutral pH, has been monitored as a function of the metal complex-DNA molar ratio by UV absorption spectrophotometry, circular dichroism (CD) and fluorescence spectroscopy. The results support for an intercalative interaction of both ZnL(2+) and CuL(2+) with DNA, showing CuL(2+) an affinity of approximately 10 times higher than ZnL(2+). In particular, the values of the binding constant, determined by UV spectrophotometric titration, equal to 7.3x10(4) and 1.3x10(6)M(-1), for ZnL(2+) and CuL…

DFT Calculations of the Electric Field Gradient at the Tin Nucleus as a Support of Structural Interpretation by119Sn Mössbauer Spectroscopy

DFT calculations, using an all-electron basis set and with full geometry optimization, were performed on 34 Sn(II) and Sn(IV) compounds of known structure and (119)Sn Mössbauer parameters, to obtain the theoretical values of the electric field gradient components, V(xx), V(yy), and V(zz), at the tin nucleus. These were used to determine the quantity V = V(zz)[1+ 1/3((V(xx) - V(yy))/((V(zz))(2)](1/2), for each investigated compound, which is related to the quadrupole splitting (DeltaE) parameter according to DeltaE = 1/2eQV, where e is the electronic charge and Q is the quadrupole moment of the tin nucleus. The linear fitting of the correlation plot of the experimental DeltaE, versus the cor…

Synthesis, characterization, and in vitro antimicrobial activity of organotin(IV) complexes with triazolo-pyrimidine ligands containing exocyclic oxygen atoms

Abstract Tri-organotin(IV) complexes of the triazolo-pyrimidine derivatives 4,5-dihydro-5-oxo-[1,2,4]triazolo-[1,5 a ]pyrimidine (5HtpO), 4,7-dihydro-5-methyl-7-oxo-[1,2,4]triazolo-[1,5 a ]pyrimidine (HmtpO), and 4,5,6,7-tetrahydro-5,7-dioxo-[1,2,4]triazolo-[1,5 a ]pyrimidine (H 2 tpO 2 ), and the diorganotin derivative n -Bu 2 Sn(tpO 2 ), were synthesized and characterized by means of infrared and 119 Sn Mossbauer spectroscopy. In all the complexes obtained the triazolopyrimidines act as multidentate ligands producing polymeric structures. A trigonal bipyramidal arrangement of the ligands around the tin atom is proposed for triorganotin(IV) derivatives, with organic groups on the equatoria…

XPS structural data and correlation with Mossbauer spectra for Tin-organic compounds: adducts of RnSnCl4-n with 1,2-bis(diphenylphosphino)ethane

Abstract Core level X-ray photoelectron spectra of 1:1 adducts of SnCl4 and RSnCl3 with DPE {[RnSnCl4−n} · DPE (n = 1, R = Me, Bun, Octn, Phn; n = 2, R = Ph; DPE = 1,2-bis(diphenylphosphino)ethane], have been measured in solid phase. The Sn3d 5 2 binding energies, corrected for the Madelung potential at the metal atom, are well correlated with both partial atomic charge on tin, accounting for relaxation upon ionization, and 119Sn Mossbauer isomer shifts. The results are discussed in terms of these molecular parameters.

Infrared, Mössbauer and lattice dynamics studies of (3-mercaptopropionato)bis(trimethyltin(IV))

Investigations on organotin, organolead, lead(IV), and lead(II) dithiolates

Abstract Bis(triorganometal) 1,2-dithiolates (R3M)2S2R′ [(HS)2R′ = C7H8S2 for toluene-dithiol-3,4 (H2TDT); M = Sn, Pb; R = Ph; or (HS)2R′ = C10H14S2 for 1,2-dimethyl-4,5-bis(mercaptomethyl)benzene (H2DBB); M = Sn, R = CH3, C6H5; M = Pb, R = C6H5], diorganometal 1,2-dithiolates R2MS2R′ [(HS)2R′ = C6H6S2 for 1,2-dimercaptobenzene (H2DMB); M = Pb, R = CH3, C2H5, C6H5; or (HS)2R′ = H2TDT; M = Sn, R = CH3, C6H5; M = Pb, R = C6H5; or (HS)2R′ = H2DBB; M = Sn, R = CH3, C6H5; M = Pb, R = CH3, C2H2, C6H5; or (HS)2R′ = C8H6N2S2 for 2,3-dimercaptoquinoxaline (H2QDT); M = Pb, R = C6H5] and some lead(IV) and lead(II) dithiolates Pb(S2R′)n [(HS)2R′ = H2DMB, n = 2; (HS)2R′ = H2TDT, n = 2; (HS)2R′ = H2DBB, …

Mono-aryltin(IV) and mono-benzyltin(IV) complexes with pyridine-2-carboxylic acid and 8-hydroxyquinoline. X-ray structure of p-chloro-phenyl-tris(8-quinolinato)tin(IV)·2CHCl3

Abstract Complexes RSn(O2CPy)3·2H2O and RSn(Ox)3, (PyCOOH=pyridine-2-carboxylic acid, HOx=8-hydroxyquinoline, R=o- and p-Tolyl, o- and p-ClC6H4=o- and p-ClPh, o-ClC6H4CH2=o-ClBenzyl; besides, R=Ph in RSn(Ox)3) have been synthesized and characterized by elemental analysis and determination of molecular weights in CHCl3 solutions. The structure of p-ClPhSn(Ox)3·2CHCl3 has been determined by X-ray diffractometry. The 7-coordinated tin atom of the monomeric compound is in the center of a pentagonal bipyramid formed by (p-ClPh)C and O and N atoms of the chelating Ox− ligands. The latter type of structure would hold for all complexes according to 119Sn Mossbauer (including the determination of th…

Ground state and electronic spectrum of Cu(ii) and Cu(iii) complexes of N,N′-1,2-phenylenebis-2-mercaptoacetamide

The electronic structure and the UV-vis spectrum of reduced and oxidized model systems of the N,N'-1,2-phenylenebis(2-mercapto-2-methylpropionamide) copper complex have been studied using a multiconfigurational quantum chemical method (CASSCF/CASPT2). The bonds between Cu and the two sulfur ligand atoms have a large covalent character in the oxidized Cu(III) form. As a result of the increased covalency, the effective charge on the Cu atom is actually smaller in the oxidized form. The electronic spectrum for both oxidation states of the complex is in agreement with the experiment for excitation energies and intensities showing that the theoretical description of the electronic structure is e…

A study of dimethyltin(IV)-L-cysteinate in aqueous solution

The in vivo activity of some R2Sn-L-cysteinate complexes (R = Me, Et, n-Bu) against murine P-388 leukaemia has been tested. Only the Et2Sn(IV) complex showed a marginal positive effect. Trigonal bipyramidal tin environments with two carbon (R) atoms and the sulfur atom in the equatorial plane and oxygen (carboxylate) and nitrogen (NH2) in apical positions have been proposed for the solid compexes (R = Me, Et, n-Bu, Ph) on the basis of experimental Mossbauer parameters and infrared (IR) data. Aqueous solutions of the Me2SnL-cysteinate have been studied by IR, 1H NMR and 119Sn Mossbauer spectroscopy (in frozen solution) at different pH values to identify the Me2Sn(IV) species present. At pH >…

Studio computazionale della interazione tra proflavina e i polinucleotidi poly(dA-dT).poly(dA-dT) e poly(dG-dC).poly(dG-dC).

Spectroscopic Study of the Interaction of NiII-5-triethyl Ammonium Methyl Salicylidene orto-phenylendiiminato with Native DNA

Complexes of organometallic compounds

Abstract The configurations of (CH 3 ) 3 PbNCS, (C 6 H 5 ) 3 PbNCS, (C 6 H 5 ) 2 Pb(NCS) 2 , (C 6 H 5 ) 3 Pb(NCS) 2 − and (C 6 H 5 ) 2 Pb(NCS) 4 2− have been investigated in the solid and (except for the insoluble diphenyl derivative) in solution. From infrared spectroscopy it is deduced that the compounds are isothiocyanates in both states, and there is evidence for a polymeric nature of the solid neutral species involving bridging through NCS. PMR and osmometric investigations show that five-coordinate species (CH 3 ) 3 Pb(NCS)·(CH 3 ) 2 CO are present in acetone solution. Possible configurations are discussed.

Mossbauer spectroscopic studies on the molecular dynamics of organotin(IV) polymers

Abstract Linear organotin(IV) polymers with tin appended to the polymer chain or inserted into the polymer backbone have been characterized by Mossbauer spectroscopy. The lattice dynamics of three representative examples of these classes, as well as of a cross-linked organotin(IV) polymer, have been investigated by temperature-dependent Mossbauer spectroscopy. It has been shown that parameters associated with polymers having low interchain interactions practically correspond to those of molecular, non-coupled, solids.

ChemInform Abstract: Pyrazolo[3,4-d][1,2,3]triazolo[1,5-a]pyrimidine: A New Ring System Through Dimroth Rearrangement.

Abstract Derivatives of the new ring system pyrazolo[3,4- d ][1,2,3]triazolo[1,5- a ]pyrimidine were synthesized from the corresponding angular isomers, through a Dimroth rearrangement, in quantitative yields. Preliminary computational studies demonstrated that this class of compounds could be a good candidate as DNA intercalating agents.

Sintesi di Nuovi Derivati del Sistema Triciclico Pirazolo[3,4-d][1,2,3]triazolo[1,5-a]pirimidinico DNA interattivi

A119Sn Mössbauer spectroscopic study on complexes of di-and tri-organotin(IV) moieties with 2-mercaptoethanesulfonates, in the solid state and in aqueous solution

The configuration of the bonding environment of tin in the complexes [R2Sn(SCH2CH2SO3)2]2− (R = Me, Ph) and [Me3Sn(SCH2CH2SO3)]− has been determined to be tetrahedral both in the solid state and in aqueous solution (for the methyl derivatives). The coordination number of tin increases to five in aqueous solutions for the Me2Sn(IV) complexes in Hepes buffer (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid; at least in fivefold excess, at pH 7.4) due to coordination by the tertiary amino nitrogen atom. No effect is detected due to the surfactant 2-hydroxypropylcellulose concerning both coordination to tin and influence on the Mossbauer parameters. The stoichiometry of mixed complex format…

The interaction of S,N-coordinated dimethyltin(IV) derivatives with deoxyribonucleic acid: structure and dynamics by119Sn Mössbauer spectroscopy

Complexes Me2SnCl(SPy) and Me2SnCl(SPym) (HSPy = 2-mercaptopyridine; HSPym = 2-mercaptopyrimidine), from ethanol solutions, interact with aqueous calf-thymus DNA yielding condensed phases with probable Me2Sn(SPy,SPym) (DNA monomer) stoichiometries of 1:1; the condensation of DNA is inferred originated from electrostatic bonding between complex cations Me2Sn(SPy,SPym)+ and the phosphate oxygen of the phosphodiester groups. Octahedral-or trigonal-bipyramidal tin environments are inferred from the point-charge model treatment of the 119Sn Mossbauer parameter nuclear quadrupole splitting, considering the bonding by S and N, or only S donor atoms from the ligand, as well as possible coordination…

The interaction of native calf thymus DNA with Zn(II)-N,N'-bis(5,5'-triethylammoniomethyl-salicylidene)phenylendiimine

The interaction between native calf thymus deoxyribonucleic acid (DNA) and Fe-III-N,N'-ethylene-bis (salicylideneiminato)chloride, Fe(Salen)Cl, was investigated in aqueous solutions by UV-visible (UV-vis) absorption, circular clichroisin (CD), thermal denaturation and viscosity measurements. The results obtained from CD, UV-vis and viscosity measurements exclude DNA intercalation and can be interpreted in terms of an electrostatic binding between the Fe(Salen)(+) cation and the phosphate groups of DNA. The trend of the UV-vis absorption band of the Fe(Salen)Cl complex at different ratios [DNA(phosphate)]/[Fe(Salen)Cl] and the large increase of the melting temperature of DNA in the presence …

Complexes of organometallic compounds. L. The correlation between 119Sn mössbauer isomer shifts and calculated partial charges on tin in adducts of tin(IV) and organotin(IV) halides with phosphorus and oxygen donors

Abstract The relationship between Mossbauer isomer shifts, δ, and atomic charges on tin, QSn has been studied for homologous series RnSnhal4−n· L2 [ n = 0−3; L2 = donor atoms of 1, 2-bis(dipheylphosphino)ethane, N, N′-ethylenebes(salicylideneimine) and N, N′-ethylenbes(acetylacetoneimine)] and Snhal4· 2PR3. Semiempirical values of QSn have been calculated by two methods based on the concept of orbital electronegativity equalization upon bond formation. Linear correlations δ/QSn are obtained, which can be function of the coordination number of the metal atom, for terms of the series characterized by different orbital electronegativities of atoms directly bound to tin. Deviations occur for ad…

Studies on the antitumor activity of complexes of R2Sn(IV) with penicillamine enantiomers and with 3-thio-propanoic acid, and correlation with structural aspects

Abstract The activity of diorganotin(IV) derivatives, with SnS bonds, against murine leukemia P-388, has been investigated. The water-soluble penicillamine (PenH2) complexes, Me2Sn(D-Pen), Me2Sn(L-Pen), Me2Sn(D-PenH)2 and Me2Sn(L-PenH)2, are essentially inactive, and do not show any dependence of the antitumor activity from the configuration about the chiral centre. The complexes with 3-thiopropanoic acid (H2Tpr), R2Sn(Tpr), are active for REt and Ph, in line with the general behaviour of R2Sn(IV) derivatives. The nature of the organotins in the vehicle of administration is investigated by 119Sn Mossbauer spectroscopy. The structures of solid state polymers, occurring in suspensions, are …

The hydrolysis of Me2SnIV and Me3SnIV moieties monitored through 119Sn Mössbauer spectroscopy

Abstract The 119 Sn Mossbauer parameters δ, isomer shift, and Δ E , nuclear quadrupole splitting, have been determined in frozen aqueous solutions of Me 2 Sn IV and Me 3 Sn IV moieties at varying pH. The resulting functions n versus pH (where n is the average number of protons released per mole of the organotin aquocation) agree satisfactorily with functions from potentiometry. The structures of the aquocations, as well as of the hydroxides, and of the mono-hydroxo complex [Me 2 Sn(OH)(OH 2 ) n ] + , are correlated to the Δ E exp data by point-charge model calculations.

Complexes of organometallic compounds

Abstract Novel complexes RClSntrid, where R is Me, Ph, n-Oct, and trid 2− are dianions of tridentate “planar” ligands with ONO and SNO donor atoms, were synthesized and investigated in the solid state by infrared and Mossbauer spectroscopy. Possible configurations are discussed; polymeric trigonal bipyramidal structures seem to occur, although five-coordinated monomers as well as octahedral dimers (via oxygen or sulfur bridges) are not excluded.

Complexes of organometallic compounds. LII. 119Sn Mössbauer isomer shifts, partial atomic charges on tin, and structure, in triorganotin(IV) halides

Pyrazolo[3,4-d][1,2,3]triazolo[1,5-a]pyrimidine: a new ring system through Dimroth rearrangement

Abstract Derivatives of the new ring system pyrazolo[3,4- d ][1,2,3]triazolo[1,5- a ]pyrimidine were synthesized from the corresponding angular isomers, through a Dimroth rearrangement, in quantitative yields. Preliminary computational studies demonstrated that this class of compounds could be a good candidate as DNA intercalating agents.

Synthesis and structural characterisation of copper complexes mimetic of “blue copper” proteins active site

Intercalation of daunomycin into stacked DNA base pairs. DFT study of an anticancer drug

We have computationally studied the intercalation of the antitumor drug daunomycin into six stacks of Watson-Crick DNA base pairs i.e., AT-AT, AT-TA, GC-AT, CG-TA, GC-GC, GC-CG) using density functional theory (DFT). The proton affinity of the DNA intercalater daunomycin in water was computed to be 159.2 kcal/mol at BP86/TZ2P, which is in line with the experimental observation that daunomycin is protonated under physiological conditions. The intercalation interaction of protonated daunomycin with two stacked DNA base pairs was studied through a hybrid approach in which intercalation is treated at LDA/TZP while the molecular structure of daunomycin and hydrogen-bonded Watson-Crick pairs is c…

Tin-DNA complexes investigated by nuclear inelastic scattering and synchrotron radiation

Synthesis, spectroscopic characterization and in vitro antimicrobial activity of diorganotin(IV) dichloride adducts with [1,2,4]triazolo-[1,5-a]pyrimidine and 5,7-dimethyl-[1,2,4]triazolo-[1,5-a]pyrimidine

Abstract The heterocyclic ligands [1,2,4]triazolo-[1,5-a]pyrimidine (tp) and 5,7-dimethyl-[1,2,4]triazolo-[1,5-a]pyrimidine (dmtp), react with diorganotin dichlorides giving the addition compounds Me2SnCl2(tp)2, Et2SnCl2(tp)2, Me2SnCl2(dmtp)2, Et2SnCl2(dmtp)2, Bu2SnCl2(dmtp), Ph2SnCl2(dmtp). The organotin:ligand stoichiometry goes from 1:2 to 1:1 by increasing the steric hindrance of the organic groups bound to tin. The compounds have been characterized by means of infrared, 119Sn Mossbauer and 1H AND 13C NMR spectroscopy. The ligands presumably coordinate to tin classically through the nitrogen atom at the position 3. The 1:1 complexes adopt trigonal bipyramidal structures, with the organi…

Mono-organotin(IV) and tin(IV) derivatives of 2-mercaptopyridine and 2-mercaptopyrimidine: X-ray structures of methyl-tris(2-pyridinethiolato)tin(IV) and phenyl-tris(2-pyridinethiolato)tin(IV)�1.5CHCl3

Mono-organotin(IV) and tin(IV) derivatives of 2-mercaptopyridine (HSPy) and 2-mercaptopyrimidine (HSPym), RSnL 3 (R=Me, n-Bu, Ph; L=SPy, SPym; R=Bz=benzyl, o-CIBz, oClC 6 H 4 , p-ClC 6 H 4 , o-tolyl, p-tolyl; L=SPy), RSnCIL 2 (R=Me, n-Bu, Ph; L=SPy, SPym), RSnCI 2 L (R=Me, n-Bu; L=SPy, SPym) and SnCI 4-n L n (L=SPy, SPym; n=2,4) were obtained from RSnCI 3 or SnCI 4 and NaL or by neutralization (R=Ph,p-tolyl; L=SPy, SPym). RSnCIL 2 and RSnCI 2 L were better prepared by comproportionation of RSnCI 3 and RSnL 3 . MeSn(Spy) 3 and PhSn(SPy) 3 .1.5CHCI 3 crystals, as determined by single-crystal X-ray diffraction, are monoclinic. In the discrete monomeric RSn(SPy) 3 units, three bidentate SPy lig…

Synthesis and structural studies by infrared and Mössbauer spectroscopy of adducts of tin(IV) and organotin(IV) derivatives with 2,2′-azopyridine

Abstract A number of complexes have been prepared by the reaction between 2,2′-azopyridine(AZP) and tin(IV) halides and organotin(IV) halides, and characterized by elemental analysis and infrared and variable temperature 119Sn Mossbauer spectroscopies. All of the new compounds have 1:1 stoichiometry, with the AZP ligand occupying two coordination sites by bonding through one of the ring and one of the azo group nitrogen atoms, to give rise to distorted octahedral structures. In the diorganotin complexes the two organic groups occupy trans positions. The infrared and Mossbauer spectroscopic data suggest that these compounds are monomeric in the solid state.

An infrared study of organothallium thiocyanates

Abstract Some structural aspects of the organothallium(III) thiocyanates R 2 TlCNS (R = Me, Ph).[Ph 4 As][Me 2 Tl(CNS) 2 ] and Phtl(CNS) 2 have been studied by IR spectroscopy. From the frequencies of the NCS group vibrations in the solids, and the integrated intensity of the C≡N stretching absorption in solution, it was ascertained that the diorganothallium derivatives are isothiocyanates with a certain amount of ionic character in the TlNCS bonds, whereas PhTl(CNS), is essentially a TlSCN bonded compound. Apparently both solid Me 2 TlCNS and [Ph 4 As][Me 2 Tl(CNS) 2 ] do not show IR active ν s (TlC 2 )bands. The compound Me 2 TlCNS displays a double ν as (TlC 2 band, from which the pres…

119Sn M�ssbauer studies of bis[cysteinato(1?)-S]- and bis[penicillaminato(1?)-S]-diorganotin(IV) species in the crystalline state and in frozen aqueous solution

The bonding and the configuration of the tin environment in the title compounds {R2Sn[SCH2CH(NH3+)COO−]2 and R2Sn[SC(CH3)2CH(NH3+)COO−]2, indicated in the following as R2Sn(cysH)2 and R2Sn(penH)2 respectively} has been investigated through the determination of the Mossbauer-Zeeman spectra of Ph2Sn(cysH)2 and Ph2Sn(penH)2 in the solid state, and through conventional Mossbauer spectroscopy of Me2Sn(penH)2 in the solid state as well as of Me2Sn(cysH)2 and Me2Sn(penH)2 in aqueous solution (frozen). The treatment of the data by the pointcharge model approach suggested the general occurrence of a tetrahedral C2SnS2 core. In aqueous Hepes buffer, a tertiary amino nitrogen atom has been observed to…

The dynamics of 57Fe nuclei in Fe(II)-DNA and [Fe(II)(1-methyl-2-mercaptoimidazole)2]-DNA condensates.

Abstract Alcoholic solutions of FeCl 2 and Fe II (Hmmi) 2 Cl 2 (Hmmi=1-methyl-2-mercaptoimidazole) induce calf thymus DNA condensation from aqueous solutions buffered at pH 7.4. A 1:1 Fe II –(DNA monomer) stoichiometry is assumed. The 57 Fe Mossbauer hyperfine parameters suggest an octahedral coordination environment, severely distorted, in both Fe II –(DNA monomer) and [Fe II (Hmmi) 2 ]–(DNA monomer) condensates. The dynamic properties of iron nuclei in freeze-dried samples were investigated by means of variable temperature 57 Fe Mossbauer spectroscopy. Mean square displacements, 〈 x 2 〉( T ), were calculated, such as the effective vibrating mass and the Mossbauer lattice temperature of th…

Diorganotin(IV)-2-mercaptopyrimidine complexes

The complexes formed between the diorganotin(IV) moieties, R 2 Sn(IV), and the ligand 2-mercaptopyrimidine, (H)SPym, were investigated. Complexes R 2 SnHal(SPym) and R 2 Sn(SPym) 2 [R = Me, i Pr, n Bu, i Bu, t Bu, cyclohexyl(Cy), Ph] were synthesized, and characterized by elemental analysis. In the solid state, chelation of SPym through S and N donors was established by IR spectroscopy, and the nature of the environment of tin centers was investigated by 119 Sn Mossbauer spectroscopy. From the dynamics of 119 Sn nuclei determined by variable-temperature measurements on representative compounds [Me 2 SnCl(SPym) and Cy 2- SnBr(SPym)], as well as by point-charge model treatment of nuclear quad…

Synthesis and mössbauer studies of some aquo complexes of tin(IV) with crown ethers

Abstract The preparation, characterization, and 119Sn Mossbauer spectra of a number of tin(IV) complexes with cyclic polyethers are presented. With tin(IV) chloride and methyltin(IV) trichloride, 1:1 and 2:1 metal-to-crown-ether complexes are formed, while dimethyltin(IV) dichloride forms only 2:1 complexes; in every case, two water molecules are present in the solid state structure. An octahedral coordination geometry around the tin(IV) center is proposed on the basis of Mossbauer and IR spectra.