Ekkehard Sinn

Single- and Multiphoton Turn-On Fluorescent Fe3+ Sensors Based on Bis(rhodamine)

Selective and sensitive turn-on fluorescent Fe(3+) sensors based on novel bis(rhodamine) dye molecules are reported. The compounds are synthesized with very high yields and characterized with NMR, ESI mass spectrometry, and elemental analysis. Single- and two-photon fluorescence enhancement is observed for both molecules in the presence of Fe(3+). High selectivity and sensitivity is observed over other metal ions and is shown to be due mainly to the spirolactam ring-opening power of Fe(3+). All measurements are made in buffer environments simulating biological conditions to facilitate single- and multiphoton fluorescence imaging of Fe(3+) in vivo and in vitro. Larger enhancement of fluorescence for both one- and two-photon excitation makes them suitable candidates for fluorescent labeling of biological systems. Two photon cross-section and time-resolved fluorescence measurements are utilized to understand the selectivity of the present sensors for Fe(3+)-sensing.

Magnetic study of M‐type doped barium ferrite nanocrystalline powders

We have studied the static magnetic properties of three different M‐type doped barium ferrite compounds prepared by the glass crystallization method. The zero‐field‐cooled (ZFC) and field‐cooled (FC) processes have been recorded at low field and they all show the typical features of a small particle system. The ZFC curves display a broad peak at a temperature TM, which depends on the distribution of particle volumes in the sample. Isothermal magnetization curves M(H) at several temperatures and saturation magnetization Ms as a function of temperature have been measured for the Co‐Ti sample (BaFe10.4Co0.8Ti0.8O19). The dependence on temperature of the macroscopic magnetic parameters has been analyzed. The distribution of blocking temperatures is studied from the derivative of the remanent‐to‐saturation magnetization ratio with respect to temperature and it is fitted to a lognormal distribution, leading to a mean blocking temperature 〈TB〉=(81±40) K. The distribution of volumes of the magnetic unit is also o...

Pentacoordinate copper complexes of nitrogen-sulfur donors: structural chemistry of two complexes of bis(2-(2-benzimidazolyl)ethyl) sulfide with the sulfur alternatively in equatorial and axial coordination modes

Resolution structurale des deux complexes [Cu(BBES) (MeOH) (OH 2 )] (ClO 4 ) 2 et [Cu(BBES) (acoc)] PF 6 •H 2 O•EtOH, BBES=bis-(N-methylbenzimidazolyl-2)-1,5 oxo-3 pentane. Spectres RPE montrant que les complexes gardent leurs structures deformees en solution

Properties of barium hexaferrite powders for magnetic recording

Abstract Substituted barium hexaferrite powders prepared by the glass crystallization method are investigated geometrically and magnetically. Evaluating a special kind of remanence curves allows the anisotropy field distribution of the powders to be determined. In order to obtain the intrinsic anisotropy field distribution the influence of thermal fluctuations must be separated from the data. The magnetic properties of powders of different composition are discussed.

Structural and magnetic properties of BaFe/sub 12-2x/Co/sub x/Ti/sub x/O/sub 19/ powders prepared by the glass crystallization method

The glass crystallization method is shown to be suitable for preparing BaFe/sub 12-2x/Co/sub x/Ti/sub x/O/sub 19/ powders with a nearly perfect crystallographic structure and a narrow particle size distribution. The dependences of the specific magnetization, the coercivity, and the particle size distribution on both the annealing temperature and the Co-Ti content correlate in a characteristic way. Furthermore, the lattice parameters, the specific surfaces and the thickness of the effective nonmagnetic surface layer were determined. The coercivity of the hexaferrite magnetic tapes is more than 8*10/sup 3/ A/m higher than for the corresponding powders. >

Tuning Up Superoxide Dismutase Activity of Copper Complex of Salicylaldehyde Semicarbazone by Heterocyclic Bases Pyridine and N-methyl Imidazole

Abstract The copper(II) complexes of the Schiff base salicylaldehyde semicarbazone (SALSC) have been prepared and structurally characterized. The compound possesses a distorted square planar geometry where the metal atom lies slightly below the ligand donor atom plane and exhibits a longer Cu–Cl bond distance (2.226 A). The superoxide dismutase activity of the compound can be synergistically enhanced by the addition of heterocyclic bases.

Low temperature magnetic properties and antiferromagnetic interactions of the magnetic susceptibility calibrant HgCo(NCS)4

Abstract High sensitivity magnetic susceptibility determinations in the range 1.3-100K, on HgCo(NCS) 4 , a common susceptibility calibrant, are reported. Earlier literature data reported for calibration purposes are shown to be inaccurate. Previously undetected anti- ferromagnetic interactions are shown to exist in HgCo(NCS) 4 , causing deviation from Curie-Weiss behavior at low temperatures.

Crystal structures of cis-dibromodioxobis(triphenylphosphine oxide)molybdenum(VI), cis-dichlorodioxobis(triphenylphosphine oxide)molybdenum(VI), and cis-bis(butane-2,3-diolato)dioxomolybdenum(VI)–butane-2,3-diol (1/2): a comparison of co-ordination spheres and the general stereochemistry of molybdenum(VI) oxo-complexes

The crystal and molecular structures of the title complexes cis-[MoO2Br2(PPh3O)2](1), cis-[MoO2Cl2(PPh3O)2](2), and the i.r. spectra of these complexes and of a third complex, cis-[MoO2F2(PPh3O)2](3), have been determined. Crystal data: (1), space group P21/c, Z= 4, a= 19.081(1), b= 9.964(1), c= 19.202(1)A, β= 111.52(2)°, R= 0.068 for 5 023 reflections; (2), space group P21/c, Z= 4, a= 18.95(3), b= 10.003(1), c= 19.278(2)A, β= 112.06(4)°, R 0.052 for 6 520 reflections. Complexes (1) and (2) have distorted octahedral symmetry with cis PPh3O ligands. Apart from those bonds involving halogens, there are no significant differences in bond lengths in the two complexes. Assignments of the i.r. spectra of (1)–(3) have been correlated with their structural features. General aspects of the stereochemistry of molybdenum(VI) complexes are highlighted, and it is shown how these can be successfully applied to predict the gross stereochemistry of a molybdenum(VI) complex with butane-2,3-diol (HL), cis-[MoO2L2]·2HL, whose structure was previously unknown. Crystal data for (4): space group C2/c, Z= 4, a= 16.269(5), b= 9.848(5), c= 14.313(5)A, β= 91.31(5)°, R 0.076 for 1 368 reflections. The crystal contains isolated MoO2L2 molecules connected by hydrogen bonds to two HL molecules. The complex also has distorted octahedral symmetry with two short, two medium, and two long Mo–O bonds. A general principle is established that in mixed-ligand complexes the weaker π-bonding donors are found to be trans to the terminal oxygen where they are not directly competing for the available empty metal 4d orbitals.

Hormone anchored metal complexes. 1. Synthesis, structure, spectroscopy and in vitro antitumor activity of testosterone acetate thiosemicarbazone and its metal complexes.

Testosterone acetate thiosemicarbazone (TATSC, 17-β-hydroxyandrost-4-one acetate thiosemicarbazone) was synthesized and characterized by single crystal X-ray structure determination. The copper and platinum complexes of this steroid derivative were synthesized and characterized by spectroscopy and electrochemiatry. The in vitro activity of these compounds against human breast cancer cell line MCF-7 was tested. The highest activity was found for the [Pt(TATSC)Cl1] followed by [Cu(TATSC)Cl2] and the ligand in compariosn with cisplatin.

Peroxo malato vanadates(V): syntheses, spectra and structure of the (NH4)2[VO(O2)(C4H4O5)]22H2O dimer with a rhomboidal V2O2(hydroxyl) bridging core

Crystalline peroxo malato vanadates(V) of the formula M[VO(O2)(C4H4O5)]H2O, where M = Na, K, NH4, Cs, obtained from aqueous solutions and characterized by IR and UV spectroscopy are described. X-ray structure analysis of (NH4)2[VO(O2)(C4H4O5)]22H2O shows that the complex crystallizes in the triclinic space group, P1, with a = 9.157(4), b = 9.662(5), c = 14.203(5) A, ga = 104.58(3), β = 90.52(3), γ = 115.50(2)°, V=1088 A3, Z=2. The structure contains a dimer with a novel tridentate coordination of the malato ion. Two bridging hydroxyl oxygens enclose a symmetrical rhomboidal V2O2 plane, binding two distorted pentagonal bipyramidal vanadium polyhedra. The peroxo groups, with OO bond lengths of 1.442(2) A, are located in the equatorial plane across from the bridging hydroxyl oxygens, and the fifth side of the pentagonal plane is occupied by the oxygen of the vicinal carboxylic group. The second carboxylic group is coordinated at the apical position, trans to the oxo group. In the UV spectra all the compounds show the typical broad [monoperoxo → vanadium] charge transfer band at a λmax=425 nm. Characteristic very strong IR bands were assigned by comparison with the spectra of malic acid and numerous other heteroligand peroxo vanadates(V). The v(OO) stretch appears in the vicinity of 922 cm−1, and the v(V = O) band near 977 cm−1. The stereochemistry and the relationship of these compounds to the biochemistry of vanadium are discussed.