Adam Gorczyński

Electrochemical deposition of the new manganese(II) Schiff-base complex on a gold template and its application for dopamine sensing in the presence of interfering biogenic compounds.

Facile and efficient template synthesis of new manganese(II) complex [Mn2(H2L)2](ClO4)2 (1) and its crystal structure are reported. Self-assembly leads to the formation of dinuclear, phenoxo-bridged closed species via exploitation of both binding subunits of the in situ formed new Schiff-base ligand. Gold electrode modified with self-assembled monolayers (SAMs) composed of synthesized complex 1 was applied as a voltammetric sensor for quantitative determination of dopamine (DA) in the presence of ascorbic (AA) and uric acids (UA). The linear relationship between the current response of dopamine at the potential of peak maximum and the concentration was found over a wide analyte concentration range (R(2)≥0.993, 1×10(-10)-8.5×10(-4)M) with a very good sensitivity (4.11Acm(-2)M(-1) at dE/dt=0.1Vs(-1)), high detection limit (6.8×10(-9)M) and excellent reproducibility. It has been proven that current peaks of dopamine, ascorbic and uric acids were clearly separated from each other, thus enabling selective detection of these compounds coexisting in a mixture.

Fabrication of Nanostructured Palladium Within Tridentate Schiff-Base-Ligand Coordination Architecture: Enhancement of Electrocatalytic Activity Toward CO2 Electroreduction

There has been growing interest in the electrochemical reduction of carbon dioxide (CO2), a potent greenhouse gas and a contributor to global climate change, and its conversion into useful carbon-based fuels or chemicals [1–5]. Numerous homogeneous and heterogeneous catalytic systems have been proposed to induce the CO2 reduction and, depending on the reaction conditions (applied potential, choice of buffer, its strength and pH, local CO2 concentration, or the catalyst used) various products that include carbon monoxide, oxalate, formate, carboxylic acids, formaldehyde, acetone, or methanol, as well as such hydrocarbons as methane, ethane, and ethylene, are typically observed at different ratios. These reaction products are of potential importance to energy technology, food research, medical applications, and fabrication of plastic materials. Given the fact that the CO2 molecule is very stable, its electroreduction processes are characterized by large overpotentials, and they are not energy efficient. To produce highly efficient and selective electrocatalysts, the transitionmetal-based molecular materials are often considered [6–8]. The latter systems are capable of driving multi-electron transfers and, in principle, produce highly reduced species. In reality, such multi-electron charge transfer catalysts tend to effectively induce the two-electron reduction of CO2 to CO rather than yield highly reduced products in large amounts. Metallic copper electrodes are unique in this respect because they can drive multi-electron transfers. Mechanisms of the successful electrochemical reductions of CO2 to methane and ethylene can be interpreted in terms of complex processes occurring at copper electrodes [9, 10]. It is believed that, during electroreduction, the rate limiting step is the protonation of the adsorbed CO product to form the CHO adsorbate [11]. Significant decrease of the reaction overpotentials can be achieved with the use of the metal complex modified electrodes capable of both mediating electron transfers and stabilizing the reduced products [12]. Because reduction of CO2 can effectively occur by hydrogenation [13], in the present work, we concentrate on such a model catalytic system as nanostructured metallic palladium capable of absorbing reactive hydrogen in addition to the ability to adsorb monoatomic hydrogen at the interface [14–16]. Under such conditions, the two-electron reduction of CO2 typically to CO [12] is favored. When the reaction proceeds on palladium in aqueous KHCO3 solutions, carbon monoxide together with hydrogen and small amounts of formate are produced [17–19]. Further, it has been postulated that CO and COOH adsorbates are expected to be formed at the surfaces of Pd electrodes at −1.0 V (vs. Ag/AgCl) and, subsequently, desorbed at even more negative potentials [20]. To produce highly dispersed and stabilized palladium nanoparticles (as for Fig. 1a), we have generated them by electrodeposition (through consecutive potential cycling) from the thin film of N-coordination complex of palladium(II), [Pd(C14H12N2O3)Cl2]2 MeOH. The ligand and its palladium complex (their detailed crystallographic, IR, and NMR features will be a subject of our next publication) were synthesized via typical condensation reaction as published earlier [21, 22]. The resulting metallic Pd nanoparticles (diameters, 5–10 nm), rather than Pd cationic species, are stabilized and activated by nitrogen coordination centers from the macromolecular matrix. Supramolecular architectures of active and well-defined Schiff-base-ligands containing nitrogen donor atoms are of primary importance because A. Wadas : I. A. Rutkowska : P. J. Kulesza (*) Faculty of Chemistry, University of Warsaw, Pasteura 1, 02093 Warsaw, Poland e-mail: pkulesza@chem.uw.edu.pl

Association of a terpyridine ligand with lanthanide and copper(II) nitrates

Abstract Reactions between the 1,3-bis(6-methylpyridin-2-yl)pyridine ligand L, C17H15N3 and LnIII (1a, 1b, 1c, 1d) or a mixture of LnIII and CuII nitrates (2a, 2b, 2c, 2d) resulted in a series of respectively novel mono- and heterodinuclear complexes, where LnIII=Sm (a), Eu (b), Tb (c), Dy (d). The compounds were characterized by elemental analysis, ESI-MS and IR spectra, furthermore we obtained crystals of [H2L][Eu(NO3)5] (1b) and [CuL2][Eu(NO3)5] (2b) suitable for XRD characterization. In the crystal structures the Eu ions are 10-coordinated with quite a narrow range of Eu-O distances which are between 0.2436 and 0.2556 nm. In 1b the ligand molecule is protonated in both terminal rings, and the N-H groups are involved in the N-H···O hydrogen bonds with the same oxygen atom of one of the nitro groups. These hydrogen bonds connect the ions in 1b into the complex which is the principal building block of the structure. In 2b the [CuL2]2+ counterions are present; the Cu is octahedrally coordinated by all nitrogen iatoms of two L molecules which are therefore almost perpendicular to each other. The electrostatic interactions between the charged species are in both cases the main driving force of the crystal packing.

New field-induced single ion magnets based on prolate Er(III) and Yb(III) ions: tuning the energy barrier Ueff by the choice of counterions within an N3-tridentate Schiff-base scaffold

Lanthanides have relatively recently been recognized as ideal candidates for the construction of advanced magnetic materials that would allow for their future applications in spintronics and high-density data storage. Despite enormous progress that deals with the control of magnetic anisotropy and slow relaxation of magnetization in Single Molecule Magnets (SMMs), further improvements are still indispensable to go beyond the ultra-low temperature regime. We have thus prepared four lanthanide complexes ([ErL2(OTf)(MeOH)2](OTf)2 (1), [YbL2(OTf)2](OTf) (2), [ErL(NO3)3(H2O)](3) and [YbL(NO3)3(MeOH)]·MeCN (4)) with a tridentate Schiff-base ligand L, to unravel magneto-structural correlations in this new family of field-induced Single Ion Magnets (SIMs). Interestingly, as revealed by the single crystal X-ray diffraction, their structures are synthetically tuned by the choice of the applied counterion. The static and dynamic magnetic properties of 1–4 were investigated revealing that all compounds behave as field-induced Single Ion Magnets (SIMs). Their energy barriers Ueff decrease in the sequence: 4, 2, 3, 1, with an order of magnitude difference between the highest and the lowest value. To correlate the observed magnetic properties with spectroscopic data, low-temperature absorption spectroscopy was performed. This has allowed the determination of the energy levels of the Ln(III) ions and the exact composition of the state vectors for the Ln(III) ground multiplets via crystal-field analysis (CFA) and semiempirical superposition model (SPM) approach. Theoretical and magneto-structural correlation studies indicate that one can modulate the heterotopic coordination spheres around the prolate Er(III) and Yb(III) solely with the counterions. This leads to rarely observed high-coordinate SIM species with the LnNxOy first coordination sphere (where Ln – Er or Yb, x = 3 or 6, y = 2, 3 or 6). Their performance can be related to the intricate interactions between the electron density on the Ln ion and the crystal field created by the surroundings.

Generation of Low-Dimensional Architectures through the Self-Assembly of Pyromellitic Diimide Derivatives

Small π-conjugated molecules can be designed and synthesized to undergo controlled self-assembly forming low-dimensional architectures, with programmed order at the supramolecular level. Such order is of paramount importance because it defines the property of the obtained material. Here, we have focused our attention to four pyromellitic diimide derivatives exposing different types of side chains. The joint effect of different noncovalent interactions including π–π stacking, H-bonding, and van der Waals forces on the four derivatives yielded different self-assembled architectures. Atomic force microscopy studies, corroborated with infrared and nuclear magnetic resonance spectroscopic measurements, provided complementary multiscale insight into these assemblies.

Utilization of a new gold/Schiff-base iron(III) complex composite as a highly sensitive voltammetric sensor for determination of epinephrine in the presence of ascorbic acid

The preparation of new materials that can act as systems capable of sensing biologically relevant molecules constitutes a significant modern challenge as well as a necessity oriented towards disease prevention. Subcomponent self-assembly of 2-(methylhydrazino)benzimidazole, 4-tert-butyl-2,6-diformylphenol and Fe(ClO4)2(H2O)6 leads to a new, bimetallic iron(III) complex of the following formula: [Fe2(H3L)2(MeOH)2(μ-OMe)2](ClO4)4 (1), as established by ESI-MS, FTIR and single crystal X-ray analysis. It is important to note that ligand H3L was also successfully synthesized and characterized for the first time. Compound 1 was successfully deposited on a gold electrode and applied as a voltammetric sensor with respect to epinephrine (EP). Cyclic voltammograms (CVs) proved the catalytic activity of the new, electrochemically prepared composite Au/1 for the oxidation of EP in the presence of ascorbic acid (AA). The respective current peaks were clearly separated from each other, thus enabling selective detection of these compounds coexisting in a mixture. For the prepared sensor a linear relationship between the current response of EP electrooxidation at the potential of peak maximum (ip) and the concentration of EP in solution (cEP) in the presence of constant AA concentration was found in the broad range of cEP (R2 ≥ 0.9997, 1.0 × 10−8 M to 9.0 × 10−4 M) with a high detection limit (7.4 × 10−9 M), excellent reproducibility as well as high stability.

Supramolecular complexes of cobalt(II), manganese(II) and cadmium(II) with bis(terpyridine) ligand as novel luminescent materials

Abstract Self-assembly of N6-donor bis(terpyridine) ligand L with transition metal ions: Co(II), Mn(II) and Cd(II) leads to a formation of three kinds of supramolecular complexes. In the electronic absorption and emission spectra of supramolecular complexes additional bands were observed what was ascribed to the coordination of ligand molecules to metal ions. Luminescence properties of these complexes strongly depend on the kind of metal ions and counter ions. The effective blue luminescence was observed in the case of Mn(II) and Cd(II) complexes in which all N-donor atoms of ligand molecules coordinate with the metal center