New tetradentate phenolate O^N^N^S thiosemicarbazone (TSC) ligands and their Ni(II), Pd(II) and Pt(II) complexes were studied. The diamagnetic and square planar configured orange or red complexes show reversible reductive electrochemistry...

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH4)2[TcO(OTf)5]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO3(OTf)], and intermediate TcVI species. 99Tc nuclear magnetic resonance (NMR) has been used to study the TcVII compound and electron paramagnetic resonance (EPR), 99Tc NMR and X‐ray absorption near‐edge structure (XANES) experiments indicate the presence of the reduced technetium species. In moist air, (NH4)2[TcO(OTf)5] slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH4)4[{TcO(TcO4)4}4] ⋅10 H2O. Single‐crystal X‐ray crystallography was used to determine the solid‐state structures. Additionally, UV/Vis absorption and IR spectra as well as quantum chemical calculations confirm the identity of the species.

Mats of polyvinyl alcohol (PVA) core–shell nanofibers were produced using coaxial electrospinning in the presence of a thiosemicarbazone (TSC) N4-(S)-1-phenylethyl)-2-(pyridin-2-yl-ethylidene)hydrazine-1-carbothioamide (HapyTSCmB). Monolithic fibers with 0% or 5% TSC and core–shell fibers with 10% TSC in the spinning solution were studied to compare stability and release rates. SEM showed the formation of uniform, bead-free, cylindrical, and smooth fibers. NMR spectroscopy and thermal analysis (TG/DTA) gave proof for the chemical integrity of the TSC in the fiber mats after the electrospinning process. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy showed no TSC on the surface of the PVA/TSC-PVA fibers confirming the core–shell character. The TSC release profiles of the fibers as studied using UV-vis absorption spectroscopy showed a slower release from the PVA/TSC-PVA core–shell structure compared with the monolithic PVA/TSC fibers as well as lower cumulative release percentage (17%). Out of several release models, the Korsmeyer–Peppas model gave the best fit to the experimental data. The main release phase can be described with a Fick-type diffusion mechanism. Antibacterial properties were tested against the Gram-positive Staphylococcus aureus bacterium and gave a minimal inhibitory concentration of 12.5 μg/mL. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazoliumbromide (MTT)-based cytotoxicity experiments showed that the cell viability of fibroblast at different contents of TSC was slightly decreased from 1.5% up to 3.5% when compared to control cells.

Three chiral tridentate N^N^S coordinating pyridine‐carbaldehyde (S)‐N4‐(α‐methylbenzyl)thiosemicarbazones (HTSCmB) were synthesised along with lysine‐modified derivatives. One of them was selected and covalently conjugated to the cell‐penetrating peptide sC18 by solid‐phase peptide synthesis. The HTSCmB model ligands, the HTSCLp derivatives and the peptide conjugate rapidly and quantitatively form very stable PtII chlorido complexes [Pt(TSC)Cl] when treated with K2PtCl4 in solution. The Pt(CN) derivatives were obtained from one TSCmB model complex and the peptide conjugate complex through Cl−→CN− exchange. Ligands and complexes were characterised by NMR, IR spectroscopy, HR‐ESI‐MS and single‐crystal XRD. Intriguingly, no decrease in cell viability was observed when testing the biological activity of the lysine‐tagged HdpyTSCLp, its sC18 conjugate HdpyTSCL‐sC18 or the PtCl and Pt(CN) conjugate complexes in three different cell lines. Thus, given the facile and effective preparation of such Pt‐TSC‐peptide conjugates, these systems might pave the way for future use in late‐stage labelling with Pt radionuclides and application in nuclear medicine.

Cu‐mediated radiofluorination is a versatile tool for the preparation of 18F‐labeled (hetero)aromatics. In this work, we systematically evaluated a series of complexes and identified several generally applicable mediators for highly efficient radiofluorination of aryl boronic and stannyl substrates. Utilization of these mediators in nBuOH/DMI or DMI significantly improved 18F‐labeling yields despite use of lower precursor amounts. Impressively, application of 2.5 μmol aryl boronic acids was sufficient to achieve 18F‐labeling yields of up to 75 %. The practicality of the novel mediators was demonstrated by efficient production of five PET‐tracers and transfer of the method to an automated radiosynthesis module. In addition, (S)‐3‐[18F]FPhe and 6‐[18F]FDOPA were prepared in activity yields of 23±1 % and 30±3 % using only 2.5 μmol of the corresponding boronic acid or trimethylstannyl precursor.

The three complexes [Fe(opo)3], [Cu(opo)2], and [Zn(opo)2] containing the non-innocent anionic ligand opo− (opo− = 9-oxido-phenalenone, Hopo = 9-hydroxyphenalonone) were synthesised from the corresponding acetylacetonates. [Zn(opo)2] was characterised using 1H nuclear magnetic resonance (NMR) spectroscopy, the paramagnetic [Fe(opo)3] and [Cu(opo)2] by electron paramagnetic resonance (EPR) spectroscopy. While the EPR spectra of [Cu(opo)2] and [Cu(acac)2] in dimethylformamide (DMF) solution are very similar, a rather narrow spectrum was observed for [Fe(opo)3] in tetrahydrofuran (THF) solution in contrast to the very broad spectrum of [Fe(acac)3] in THF (Hacac = acetylacetone, 2,4-pentanedione; acac− = acetylacetonate). The narrow, completely isotropic signal of [Fe(opo)3] disagrees with a metal-centred S = 5/2 spin system that is observed in the solid state. We assume spin-delocalisation to the opo ligand in the sense of an opo− to FeIII electron transfer. All compounds show several electrochemical opo-centred reduction waves in the range of −1 to −3 V vs. the ferrocene/ferrocenium couple. However, for CuII and FeIII the very first one-electron reductions are metal-centred. Electronic absorption in the UV to vis range are due to π–π* transitions in the opo core, giving Hopo and [Zn(opo)2] a yellow to orange colour. The structured bands ranging from 400 to 500 for all compounds are assigned to the lowest energy π−π* transitions. They show markedly higher intensities and slight shifts for the CuII (brown) and FeIII (red) complexes and we assume admixing metal contributions (MLCT for CuII, LMCT for FeIII). For both complexes long-wavelength absorptions assignable to d–d transitions were detected. Detailed spectroelectrochemical experiments confirm both the electrochemical and the optical assignments. Hopo and the complexes [Cu(opo)2], [Zn(opo)2], and [Fe(opo)3] show antiproliferative activities against HT-29 (colon cancer) and MCF-7 (breast cancer) cell lines in the range of a few µM, comparable to cisplatin under the same conditions.

Antibacterial fiber mats of poly(lactic-co-glycolic acid) (PLGA) were produced in the presence of different amounts of the thiosemicarbazone (TSC) N4-(S)-(1-phenylethyl)-2-(pyridin-2-ylmethylene)hydrazine-1-carbothioamide (HfpyTSCmB) through electrospinning. Increasing amounts (0, 2.5, 5, and 10 wt%) of TSC in the PLGA spinning solution in 2,2,2-trifluoroethanol (TFE) caused an increase up to 230% in conductivity and up to 27% in viscosity. The morphology of the electrospun fibers was studied using scanning electron microscope (SEM) and showed the formation of uniform, bead free, cylindrical, and smooth fiber mats. Increasing amounts of HfpyTSCmB in the polymer solution resulted also in significant shrinking of the diameter and narrowing of the size distribution of the fibers in line with the increased conductivity of the spinning solutions. Nuclear magnetic resonance (NMR) spectroscopy and thermal methods (DSC and TG/DTA) gave proof for the chemical integrity of HfpyTSCmB in the fiber mats after the electrospinning process. The release profile of HfpyTSCmB from the fibers was examined using UV-vis absorption spectroscopy. The observed release data during 21 days was fitted to different mathematical models with the best results obtained from the Higuchi release model. The fiber mat samples showed effective antibacterial properties with inhibition zones of 0.5 to 1.5 mm against the Gram-positive Staphylococcus aureus and the Gram-negative Escherichia coli. K E Y W O R D S bacteriostatic properties, controlled drug release, nano fiber mats, PLGA, thiosemicarbazone 1 | INTRODUCTION There is an increasing demand for novel antimicrobial materials in many application areas, due to threatening human health with the growth of drug-resistant pathogens due to the biological and morphological modifications. This has led the high demand for novel drugs with enhanced, targeted activity. Thiosemicarbazones (TSC) are very promising molecules having interesting pharmacological properties with remarkable antioxidant, antiviral, antibacterial, anticancer, antitumor, antimalarial, ribonucleotide reductase enzyme inhibition, and antifungal activities when coordinated to metals but also in their absence. 1-7 TSC are synthesized through condensation of thiosemicarbazides with aldehydes or ketones. 1-3 The source thiosemicarbazides are synthesized either from secondary amines in a substitution reaction with methyl hydrazinecarbodithioate or from the addition of hydrazine to isothiocyanates. 6-13 TSC can act as ligands coordinating metal ions through their azomethine nitrogen and thiocarbonyl sulfur atoms (Scheme 1). The title TSC N4-(S)-(1-phenylethyl)-2-(pyridin-2-ylmethylene)hydrazine-1-carbothioamide (HfpyTSCmB) potentially coordinates metals through three (NNS)

Ammonium pertechnetate reacts in mixtures of trifluoromethanesulfonic anhydride and trifluoromethanesulfonic acid under final formation of ammonium pentakis(trifluoromethanesulfonato)oxidotechnetate(V), (NH4)2[TcO(OTf)5]. The reaction proceeds only at exact concentrations and under the exclusion of air and moisture via pertechnetyl trifluoromethanesulfonate, [TcO3(OTf)], and intermediate TcVI species. 99Tc nuclear magnetic resonance (NMR) has been used to study the TcVII compound and electron paramagnetic resonance (EPR), 99Tc NMR and X‐ray absorption near‐edge structure (XANES) experiments indicate the presence of the reduced technetium species. In moist air, (NH4)2[TcO(OTf)5] slowly hydrolyses under formation of the tetrameric oxidotechnetate(V) (NH4)4[{TcO(TcO4)4}4] ⋅10 H2O. Single‐crystal X‐ray crystallography was used to determine the solid‐state structures. Additionally, UV/Vis absorption and IR spectra as well as quantum chemical calculations confirm the identity of the species.