A nitrosyl iron complex with 3.4-dichlorothiophenolyl ligands: synthesis, structures and its reactions with targets - carriers of nitrogen oxide (NO) in vivo.

In this work, a new binuclear nitrosyl complex with 3.4-dichlorothiophenolyl ligands [Fe2(SC6H3Cl2)2(NO)4] has been synthesized. Nitrosyl iron complexes (NICs) are systems for the storage and delivery of NO in the body. There is a dynamic equilibrium between dinitrosyl iron units bound to low molecular weight ligands and high molecular weight (protein) ligands in vivo. From this point of view, the transformation of the studied complex in DMSO and buffer, as well as in biological systems, has been analyzed. In DMSO, it decomposes into mononuclear NICs, which quickly decay in buffer solutions with NO release. The high molecular weight product is formed as a result of the binding of the complex to bovine serum albumin (the Stern-Volmer constant is 2.1 × 105 M-1). In this case, the complex becomes a prolonged NO-donor. Such a long-term effect has been observed for the first time. Similarly, in a system with oxyhemoglobin, NO generation is slower; the UV-vis spectra show a gradual formation of methemoglobin. On the other hand, reduced glutathione has little effect on the NO-donor properties of the complex despite the fact that ligand substitution is observed in the system and a binuclear product is formed. Mucin binds the complex, and the decomposition mechanism is different from that for buffer solutions. Thus, these proteins and glutathione are able to participate in the transformation of the complex and modulate its properties as a potential drug.

First crystal structure of an Fe(III) anionic complex based on a pyruvic acid thiosemicarbazone ligand with Li+: synthesis, features of magnetic behavior and theoretical analysis.

The iron(III) anionic complex based on a pyruvic acid thiosemicarbazone ligand with the lithium cation Li[FeIII(thpy)2]·3H2O (1) has been synthesized and characterized by FTIR spectroscopy, powder and single crystal X-ray diffraction, direct current magnetic susceptibility measurements, and 57Fe Mössbauer spectroscopy. Moreover, the molecular structure of the [Fe(thpy)2]- anion has been determined for the first time. The [Fe(thpy)2]- units in the triclinic P1̄ lattice of 1 are assembled into layers parallel to the bc plane. The Li+ cations and water molecules are located between the layers and the structure is stabilized by hydrogen bonding. The [Fe(thpy)2]- anions form interconnected dimer pairs through hydrogen bonds and short contacts with Fe⋯Fe separation of 6.7861(4) Å. According to dc magnetic measurements, compound 1 demonstrates an incipient spin-crossover transition from the LS (S = 1/2) to the HS (S = 5/2) state above 250 K. The Bleaney-Bowers equation for a model of an isolated LS dimer with a mean-field correction was applied to fit the experimental data of magnetic susceptibility dependence on temperature in the temperature range of 2-250 K. The intra-dimer J1 = -1.79(1) K and inter-dimer J2 = -0.24(3) K antiferromagnetic coupling constants were defined. The analysis of the 57Fe Mössbauer spectra at 80 K and 296 K confirms the presence of the shortened distances between the iron nuclei. Moreover, the influence of the lithium cation on the stabilization of the LS state was shown for the [Fe(thpy)2]- anion. BS-DFT calculations for the optimized structure of two isolated [Fe(thpy)2]- anions also correctly predict a weak exchange J1(calc) = -0.92 K. DFT calculations revealed the OPBE (GGA-type) functional that correctly predicts the spin-crossover transition for the iron(III) thpy compounds. Besides, the effect of the N2O4, N2S2O2, and N2Se2O2 coordination environments on the energy stabilization of the LS state of iron(III) anionic thpy complexes was noted as well.

Strong magneto-chiral dichroism in enantiopure chiral ferromagnets.

As materials science is moving towards the synthesis, the study and the processing of new materials exhibiting well-defined and complex functions, the synthesis of new multifunctional materials is one of the important challenges. One of these complex physical properties is magneto-chiral dichroism which arises, at second order, from the coexistence of spatial asymmetry and magnetization in a material. Herein we report the first measurement of strong magneto-chiral dichroism in an enantiopure chiral ferromagnet. The ab initio synthesis of the enantiopure chiral ferromagnet is based on an enantioselective self-assembly, where a resolved chiral quaternary ammonium cation imposes the absolute configurations of the metal centres within chromium-manganese two-dimensional oxalate layers. The ferromagnetic interaction between Cr(III) and Mn(II) ions leads to a Curie temperature of 7 K. The magneto-chiral dichroic effect is enhanced by a factor of 17 when entering into the ferromagnetic phase.

Enantiomerically pure quaternary ammonium salts with a chiral alkyl chain N(CH3)(n-C3H7)2(sec-C4H9)I: synthesis and physical studies.

A pair of enantiomerically pure quaternary ammonium salts with a chiral side chain, methyl-(R)-(1-methylpropyl)di(n-propyl)ammonium iodide 1 and methyl-(S)-(1-methylpropyl)di(n-propyl)ammonium iodide 2, and the related racemate, methyl-(rac)-(1-methylpropyl)di(n-propyl)ammonium iodide 3, were synthesized through a reductive alkylation procedure, starting from enantiomerically pure and, also, racemic forms of (rac)-(1-methylpropyl)amine. A spectroscopic chiroptical signature in solution was provided by the Raman optical activity spectra of compounds 1 and 2. The crystallographic structures of 1, 2, and 3 were examined by single crystal X-ray diffraction. 1 crystallizes in the tetragonal space group P4(3)2(1)2 (no. 96), a = b = 12.826 (2) A, c = 17.730 (2) A, V = 2916.9 (5) A(3), Z = 8, Flack coefficient 0.04 (2). 2 crystallizes in the tetragonal space group P4(1)2(1)2 (no. 92), a = b = 12.842 (1) A, c = 17.749 (2) A, V = 2927.0 (5) A(3), Z = 8, Flack coefficient 0.05 (2). The crystal structures and space groups for 1 and 2 are enantiomorphs and the crystallographic investigation confirmed the absolute configuration of the stereocenter in both compounds. 3 crystallizes in the monoclinic space group P2(1)/n(no. 14), a = 8.178 (1) A, b = 14.309 (2) A, c = 12.328 (2) A, beta = 96.811 (6) degrees, V = 1432.4 (2) A(3), Z = 4.

Structure, magnetism and optical properties of achiral and chiral two-dimensional oxalate-bridged anionic networks with symmetric and asymmetric ammonium cations.

A series of two-dimensional (2D) oxalate-based compounds, namely [N(n-C4H9)4][M(II)Cr(III)(ox)3] (M(II) = Mn, Fe; ox = C2O4(2-)) and [N(C2H5)(n-C3H7)(n-C4H9)(n-C5H11)][M(II)M(III)(ox)(3)] ((M(II), M(III)) =(Mn, Cr), (Fe, Cr), (Mn, Fe)) were synthesised starting from racemic tris(oxalato)metalate: rac-[M(III)(ox)3]3- (M(III) = Cr, Fe). For Cr(III), the synthesis has been undertaken starting from resolved (Delta)- or (Lambda)-[Cr(III)(ox)3]3-. The natural circular dichroism measurements assess the enantioselectivity of the synthesis. X-Ray powder diffraction analysis has revealed that, when racemic reagents are used to synthesise Mn(II) containing compounds, a R3c achiral space group is found. In contrast a P6(3) chiral space group is found when starting from (Delta)- or (Lambda)-[Cr(III)(ox)3]3-. Surprisingly, whatever the optical purity of the starting building block, all Fe(II) containing compounds crystallise in the P6(3) chiral space group. The magnetic properties of the synthesised compounds confirm that these compounds are ferromagnets for M(III)= Cr. For M(II)= Mn, Theta ranges between 9 and 11 K and T(c) equals 6 K. For M(II)= Fe, Theta ranges between 14 and 16 K and Tc between 11 and 12 K. [N(C2H5)(n-C3H7)(n-C4H9)(n-C5H11)][Mn(II)Fe(III)(ox)3] is an antiferromagnet with Theta = - 107 K and T(N) = 29 K.