Versatile Reactivity of MnII Complexes in Reactions with N-Donor Heterocycles: Metamorphosis of Labile Homometallic Pivalates vs. Assembling of Endurable Heterometallic Acetates.

Reaction of 2,2'-bipyridine (2,2'-bipy) or 1,10-phenantroline (phen) with [Mn(Piv)2(EtOH)]n led to the formation of binuclear complexes [Mn2(Piv)4L2] (L = 2,2'-bipy (1), phen (2); Piv- is the anion of pivalic acid). Oxidation of 1 or 2 by air oxygen resulted in the formation of tetranuclear MnII/III complexes [Mn4O2(Piv)6L2] (L = 2,2'-bipy (3), phen (4)). The hexanuclear complex [Mn6(OH)2(Piv)10(pym)4] (5) was formed in the reaction of [Mn(Piv)2(EtOH)]n with pyrimidine (pym), while oxidation of 5 produced the coordination polymer [Mn6O2(Piv)10(pym)2]n (6). Use of pyrazine (pz) instead of pyrimidine led to the 2D-coordination polymer [Mn4(OH)(Piv)7(µ2-pz)2]n (7). Interaction of [Mn(Piv)2(EtOH)]n with FeCl3 resulted in the formation of the hexanuclear complex [MnII4FeIII2O2(Piv)10(MeCN)2(HPiv)2] (8). The reactions of [MnFe2O(OAc)6(H2O)3] with 4,4'-bipyridine (4,4'-bipy) or trans-1,2-(4-pyridyl)ethylene (bpe) led to the formation of 1D-polymers [MnFe2O(OAc)6L2]n·2nDMF, where L = 4,4'-bipy (9·2DMF), bpe (10·2DMF) and [MnFe2O(OAc)6(bpe)(DMF)]n·3.5nDMF (11·3.5DMF). All complexes were characterized by single-crystal X-ray diffraction. Desolvation of 11·3.5DMF led to a collapse of the porous crystal lattice that was confirmed by PXRD and N2 sorption measurements, while alcohol adsorption led to porous structure restoration. Weak antiferromagnetic exchange was found in the case of binuclear MnII complexes (JMn-Mn = -1.03 cm-1 for 1 and 2). According to magnetic data analysis (JMn-Mn = -(2.69 ÷ 0.42) cm-1) and DFT calculations (JMn-Mn = -(6.9 ÷ 0.9) cm-1) weak antiferromagnetic coupling between MnII ions also occurred in the tetranuclear {Mn4(OH)(Piv)7} unit of the 2D polymer 7. In contrast, strong antiferromagnetic coupling was found in oxo-bridged trinuclear fragment {MnFe2O(OAc)6} in 11·3.5DMF (JFe-Fe = -57.8 cm-1, JFe-Mn = -20.12 cm-1).

CoII Complexes with a Tripyridine Ligand, Containing a 2,6-Di-tert-butylphenolic Fragment: Synthesis, Structure, and Formation of Stable Radicals.

Interaction of a tripyridine ligand bearing a 2,6-di-tert-butylphenolic fragment (L, 2,6-di-tert-butyl-4-(3,5-bis(4-pyridyl)pyridyl)phenol) with CoII pivalate or chloride led to the formation of one-dimensional coordination polymers [Co(L)Cl2] n ·nEtOH (1) and [Co3(L)2(OH)(Piv)5] n (2) or a trinuclear complex Co3(H2O)4(L)2Cl6 (3) (Piv- = pivalate). Chemical oxidation of L and 1-3 by PbO2 or K3[Fe(CN)6], as well as exposure of L (in solution or solid state) and 2 (in solid state) to UV irradiation, led to the formation of free radicals with g = 2.0024, which probably originated because of oxidation of 2,6-di-tert-butylphenolic groups. These radicals were stable for several days in solutions and more than 1 month in solid samples. Irradiation and oxidation of the solid samples probably caused formation of the phenoxyl radical only on their surface. It was shown by density functional theory calculations that exchange coupling between the unpaired electron of the phenoxyl radical and CoII ions was negligibly weak and could not affect the electron paramagnetic resonance signal of the radical, as well as exchange coupling of CoII ions could not be transmitted by L. The latter conclusion was confirmed by the analysis of magnetic properties of 1: temperature dependency of magnetic susceptibility (χM) of 1 could be simulated by a simple model for isolated CoII ions.

Radical indicator reaction for determination of 1,1-dimethylhydrazine.

2,3,5-Triphenyl-2H-tetrazolium chloride (TPT) has been proposed as a redox indicator for determination of 1,1-dimethylhydrazine (DMH) which is used as a rocket propellant. It has been found that TPT is a sensitive chromogenic reagent due to its potentiometric and spectral characteristics. Products of the reaction between DMH and TPT have been characterized by mass spectrometry and EPR spectroscopy. In the EPR studies, C,N-diphenylnitrone (DPN) has been used as the radical trap and the obtained data indicate the radical nature of the reaction. The EPR spectrum of a mixture containing DPN and DMH has been recorded and calculated, whereas the spectrum of a three-component mixture containing DPN, TPT, and DMH is measured but it is complex for interpretation. A passive chemical dosimeter as a paper indicator strip with a polymer substrate impregnated with TPT has been manufactured and tested for continuous monitoring and determination of DMH in air in out-of-laboratory conditions at a concentration as low as 0.006 mg/m3 (warehouse operation area) and 0.5 mg/m3 (a warehouse box).

Combined analysis of chemical bonding in a Cu(II) dimer using QTAIM, Voronoi tessellation and Hirshfeld surface approaches.

Interaction of 1-(1H-pyrazol-5-yl)ethanone oxime (H2PzOx) with copper(II) chloride in the presence of pyridine afforded a binuclear discrete [Cu2(HPzOx)2Cl2py2] complex, which was characterized by Fourier transform-IR and electron paramagnetic resonance (EPR) spectra, magnetochemistry and high-resolution X-ray diffraction experiments. Multipole refinement of X-ray diffraction data and density-functional theory (DFT) calculations of an isolated molecule allowed charge and spin distributions to be obtained for this compound. Magnetochemistry data, EPR spectra and DFT calculations of an isolated molecule show antiferromagnetic coupling between copper(II) ions. The spin distribution suggests an exchange pathway via the bridging pyrazole ring in the equatorial plane of the CuN4Cl coordination polyhedron, thus providing support for the classical superexchange mechanism; the calculated value of the magnetic coupling constant -2J is equal to 220 cm(-1), which compares well with the experimental value of 203 ±â€…2 cm(-1). Chemical connectivity was derived by Bader's 'quantum theory of atoms in molecules' and compared with Voronoi tessellation and Hirshfeld surface representations of crystal space. All methodologies gave a similar qualitative and semi-quantitative description of intra- and intermolecular connectivity.

Effects of solvation on the spin state of iron(III) in 2,8,12,18-tetrabutyl-3,7,13,17-tetramethyl-5,10-diazaporphyrinatoiron(III) chloride.

The chloroiron(III) complex of 2,8,12,18-tetrabutyl-3,7,13,17-tetramethyl-5,10-diazaporphyrin, [(Cl)FeMBDAP], was prepared and studied by X-ray crystallography and by solution (1)H NMR and UV-vis measurements. In the crystal structure of hemisolvate [(Cl)FeMBDAP] x 0.5CHCl(3), two nonequivalent [(Cl)FeMBDAP] units containing Fe1 and Fe2 are arranged in pi-dimers with considerable overlap on their concave sides. Axial chloride bonded to Fe2 is solvated by hydrogen bonding with CHCl(3). Parameters of the coordination pyramid have typical values for the spin-mixed (S = 3/2 / 5/2) Fe(III) complexes in the case of Fe1 and are characteristic for the pure intermediate-spin state for Fe2 (displacement from the (N(Pyr))(4) planes - 0.385 and 0.290 A and the average N(Pyr)-Fe bond lengths -1.992 and 1.954 A for Fe1 and Fe2, respectively). Effective magnetic moments in CHCl(3) and CH(2)Cl(2) capable of specific solvation of chloride by hydrogen bonding (4.5-4.6 micro(B) at 298 K) are indicative about mixed intermediate/high-spin state S = 3/2 / 5/2, with the S = 3/2 contribution increasing upon lowering of the temperature (4.02 micro(B) in CD(2)Cl(2) at 193 K). In nonsolvating CCl(4), C(6)D(6), and THF-d(8), the mu(eff) values are consistent with the predominantly high-spin state at ambient temperature (5.5-5.75 micro(B) at 298 K) and almost pure S = 5/2 state at low temperature (ca. 5.9 micro(B) in THF-d(8) below 270 K). Downfield isotropic shifts from 35 to 50 ppm are observed for alpha-alkyl protons and upfield shifts from -5 to -15 ppm for meso-CH protons, which is characteristic for the presence of the intermediate-spin state. The splitting of signals of the diastereotopic alpha-CH(2) protons is increased with growth of the S = 3/2 state contribution from 1.5 to 4 ppm in nonsolvating to 11 ppm in specifically solvating solvents at 298 K and further to 31 ppm at 193 K (in CD(2)Cl(2)). In the presence of DMSO addition and in methanol solution, the single CH(2) signal is observed at 25-28 ppm, and the meso-CH resonance is also shifted downfield to ca. 30 ppm, indicating the formation of six-coordinated complexes [(DMSO)(2)FeMBDAP](+) and [(MeOH)(2)FeMBDAP](+), the latter having the mu(eff) value of 4.92 micro(B) at 291 K is a spin-mixed species. The electron spin resonance spectra recorded at 77 K indicates that in frozen glasses in CD(2)Cl(2) and THF molecules in the high-spin state (g( perpendicular) approximately 6) and the predominantly intermediate-spin state (g( perpendicular) approximately 4.2-4.3) coexist together.