Róbert Csonka

Isoindoline-derived ligands and applications

During the past decade isoindoline-based ligands became the subject of growing interest due to their modular set-up. In this review the structure and reactivity of these ligands and their transition metal complexes are covered. Beyond the discussion of the structural properties particular attention is paid to the expanding fields of applications of these compounds.

Formation, Characterization, and Reactivity of a Nonheme Oxoiron(IV) Complex Derived from the Chiral Pentadentate Ligand asN4Py

The chiral pentadentate low-spin (S = 1) oxoiron(IV) complex [FeIV(O)(asN4Py)]2+ (2) was synthesized and spectroscopically characterized. Its formation kinetics, reactivity, and (enantio)selectivity in an oxygen-atom-transfer reaction was investigated in detail and compared to a similar pentadentate ligand-containing system.

Biological and computational evaluation of resveratrol inhibitors against Alzheimer's disease.

Abstract It has been reported that beta amyloid induces production of radical oxygen species and oxidative stress in neuronal cells, which in turn upregulates β-secretase (BACE-1) expression and beta amyloid levels, thereby propagating oxidative stress and increasing neuronal injury. A series of resveratrol derivatives, known to be inhibitors of oxidative stress-induced neuronal cell death (oxytosis) were biologically evaluated against BACE-1 using homogeneous time-resolved fluorescence (TRF) assay. Correlation between oxytosis inhibitory and BACE-1 inhibitory activity of resveratrol derivatives was statistically significant, supporting the notion that BACE-1 may act as pivotal mediator of neuronal cell oxytosis. Four of the biologically evaluated resveratrol analogs demonstrated considerably higher activity than resveratrol in either assay. The discovery of some “hits” led us to initiate detailed docking studies associated with Molecular Dynamics in order to provide a plausible explanation for the experimental results and understand their molecular basis of action.

Solid-State NMR Study of Paramagnetic Bis(alaninato-κ2N,O)copper(II) and Bis(1-amino(cyclo)alkane-1-carboxylato-κ2N,O)copper(II) Complexes: Reflection of Stereoisomerism and Molecular Mobility in 13C and 2H Fast Magic Angle Spinning Spectra

Solid-state stereochemistry and mobility of paramagnetic copper(II) complexes formed by aliphatic amino acids (l-alanine, d,l-alanine, 1-amino-2-methyl-alanine) and 1-amino(cyclo)alkane-1-carboxylic acids (alkane = propane, butane, pentane, hexane) as bidentate ligands has been studied by (13)C and (2)H solid-state fast magic angle spinning (MAS) NMR spectroscopy. We examined the prospective method to characterize solid-state paramagnetic compounds in a routine way. Both (13)C and (2)H MAS spectra can distinguish d,l and l,l diastereomers of natural and polydeuterated bis([Dn]alaninato)copper(II) (n = 0, 2, 8) complexes with axial and/or equatorial methyl positions (conformations) primarily due to different Fermi-contact (FC) contributions. The three-bond hyperfine couplings clearly show Karplus-like dependence on the torsional angles which turned out to be a useful assignment aid. Density functional theory calculations of the FC term and crystal structures were also used to aid the final assignments. The correlations obtained for bis(alaninato-κ(2)N,O)copper(II) complexes were successfully used to characterize other complexes. The usefulness of the (2)H MAS spectra of the deuterated complexes was underlined. Even the spectra of the easily exchangeable amine protons contained essential stereochemical information. In the case of a dimer structure of bis(1-aminohexane-1-carboxylato-κ(2)N,O)copper(II) both the (13)C and (2)H resolutions were good enough to confirm the presence of the cis and trans forms in the asymmetric unit. With regard to the internal solid-state motions in the crystal lattice, the obtained quadrupolar tensor parameters were similar for the d,l- and l,l-alaninato isomers and also for the cis-trans forms suggesting similar crystal packing effects, static amine deuterons involved in hydrogen bonding, and fast rotating methyl groups.

Tempo-initiated oxidation of o-phenylenediamine to 2,3-diaminophenazine

The oxidation reaction of o-phenylenediamine (PDA) to 2,3-diaminophenazine (DAP) initiated by 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) has been investigated in methanol at ambient temperature. The oxidation of PDA was followed by electronic spectroscopy and the rate constants were determined according to the rate law -d[PDA]/dt = kobs[PDA][TEMPO]. The rate constant, activation enthalpy and entropy at 323 K are as follows: kobs (dm3 mol-1 s-1) = (3.60±0.13) × 10-6, Ea (kJ mol-1) = 76±11, DH‡ (kJ mol-1) = 74±10, DS‡ (J mol-1 K-1) = -122±31.

1,3-Bis(5′-methyl-4′-phenyl-2′-thiazolylimino)isoindoline

A new sterically hindered isoindoline-based 1,3-bis(5′-methyl-4′-phenyl-2′-thiazolylimino)isoindoline (1) was synthesized by fusion method with satisfyingly good yield. The structure of the newly synthesized compound was identified by FT-IR, UV-Vis, 1H-NMR, 13C-NMR and X-ray analysis.

CCDC 1516132: Experimental Crystal Structure Determination

Related Article: Robert Csonka, Dora Lakk-Bogath, Agnes Gomory, Laszlo Drahos, Michel Giorgi, Gabor Speier, Robert K. Szilagyi, Jozsef Kaizer|2017|Inorg.Chim.Acta|||doi:10.1016/j.ica.2017.07.065

Divastartalmú oxidoreduktázok szerkezeti és funkcionális modelljei

rendelkezik, stabilis és ezért szingulett-állapotú szerves szubsztrátumokkal szemben inert. A lényegesen nagyobb energiatartalmú, instabilabb szingulett-állapotú dioxigén reaktivitása nagyobb és redoxireakciókban, valamint elektrociklikus reakciókban (pl. olefinekkel, Diels-Aldertípusú reakciókban) jól reagál. A dioxigénnek a redoxireakciókban mutatott viszonylagos inertsége az elsõ elektron termodinamikailag kedvezõtlen felvételével is magyarázható (E0 = -0,32 V). A spin-tiltott folyamat tehát a dioxigén fotooxidációs, illetve átmenetifémekkel történõ oxidatív-addíciós reakciójával oldható fel.