Dielectric-Optical Switches: Photoluminescent, EPR, and Magnetic Studies on Organic-Inorganic Hybrid (azetidinium)2MnBr4.

A new organic-inorganic hybrid, AZEMnBr, has been synthesized and characterized. The thermal differential scanning calorimetry, differential thermal analysis, and thermogravimetric analyses indicate one structural phase transition (PT) at 346 and 349 K, on cooling and heating, respectively. AZEMnBr crystallizes at 365 K in the orthorhombic, Pnma, structure, which transforms to monoclinic P21/n at 200 K. Due to the X-ray diffraction studies, the anionic MnBr42- moiety is discrete. The azetidinium cations show dynamical disorder in the high-temperature phase. In the proposed structural PT, the mechanism is classified as an order-disorder type. The structural changes affect the dielectric response. In this paper, the multiple switches between low- and high- dielectric states are presented. In addition, it was also observed that the crystal possesses a mutation of fluorescent properties between phase ON and OFF in the PT's point vicinity. We also demonstrate that EPR spectroscopy effectively detects PTs in structurally diverse Mn(II) complexes. AZEMnBr compounds show DC magnetic data consistent with the S = 5/2 spin system with small zero-field splitting, which was confirmed by EPR measurements and slow magnetic relaxation under the moderate DC magnetic field typical for a single-ion magnet behavior. Given the above, this organic-inorganic hybrid can be considered a rare example of multifunctional materials that exhibit dielectric, optical, and magnetic activity.

Unraveling the Ground State and Excited State Structures and Dynamics of Hydrated Ce3+ Ions by Experiment and Theory.

The 4f-5d transition of Ce3+ provides favorable optical spectroscopic properties such as high sensitivity and quantum yield, making it a most important dopant for lanthanide-activated phosphors. A key for the design of these materials with fine-tuned color emission is a fundamental understanding of the Ce3+ ground state and excited state structures and the dynamics of energy transfer. Such data is also crucial for deriving coordination chemistry information on Ce3+ ions in different chemical environments directly from their optical spectra. Here, by combining 4f-5d absorption and luminescence spectroscopy and highly accurate quantum chemical electronic structure calculations, we study the interplay between the local structure of Ce3+ in aqueous solutions and in crystalline hydrates, the strengths of Ce-O/Cl interactions with aqua and chloride ligands, and the resulting absorption and luminescence spectra. Experimental and theoretical absorption spectra of [Ce(H2O)9]3+ and [Ce(H2O)8]3+ with defined geometries provide a means for analyzing the equilibrium between these species in aqueous solution as a function of temperature ( K(298) = 0.20 ± 0.03), while analyses of spectra of different aqua-chloro complexes reveal that eight-coordinate aqua-chloro complexes are present in solution at high chloride concentration. An intriguing feature in these systems concerns the large observed Stokes shifts, 5500-10 100 cm-1. By exploring the excited state potential energy surfaces with relativistic multireference calculations, we show that these shifts result from significant geometrical relaxation processes in the lowest 5d1 excited state. For [*Ce(H2O)8]3+ the relaxation gives shorter Ce-O bonds and a Stokes shift of ∼5500 cm-1, while for [*Ce(H2O)9]3+ the lowest 5d1 state results in a spontaneous dissociation of a water molecule and a Stokes shift of ∼10 100 cm-1. These findings are important for the understanding and optimization of luminescence properties of cerium complexes.

The first example of ab initio calculations of f-f transitions for the case of [Eu(DOTP)]5- complex-experiment versus theory.

Crystal structures and photophysical properties (IR and UV-vis-NIR) of two compounds, [C(NH2)3]5[Eu(DOTP)]·12.5H2O and K5[Eu(DOTP)]·11H2O (DOTP = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis (methylenephosphonic acid)), were determined. The DOTP ligand is bonded to Eu3+via four O and four N atoms, filling thus eight coordination sites of Eu3+. The experimental structures of two [K4Eu(DOTP)]- clusters were used as a starting point for theoretical ab initio calculations based on a multireference wavefunction approach. Positions of the energy levels of the 4f6 configuration of the Eu3+ ion have been calculated and compared with those derived from the experimental spectra. This enabled us to tentatively assign energy levels of the Eu3+ ion. The relationship between calculated energies of excited states and Eu-N and Eu-O bond lengths was discussed with respect to the nephelauxetic effect.

A new approach to determination of hydration equilibria constants for the case of [Er(EDTA)(H2O)(n)](-) complexes.

Two anionic complexes [Er(EDTA)(H2O)2](-) and [Er(EDTA)(H2O)3](-) were obtained in the form of the following compounds: [C(NH2)3]2[Er(EDTA)(H2O)2]ClO4·6H2O () and Na[Er(EDTA)(H2O)3]·5H2O (), respectively. The UV-vis-NIR absorption spectra of both monocrystals were measured at room temperature and at 4.2 K. The influence of the coordination number changes on intensities of the f-f transitions and the crystal field splitting of (2S+1)LJ multiplets are discussed. The weighted sum of molar absorption coefficients of f-f transitions in the spectra of and was used to reproduce the absorption bands of the Er(3+)-EDTA complex in aqueous solution. This approach allowed us to estimate that the complex in solution exists in 95% as the 8-coordinate [Er(EDTA)(H2O)2](-) species and in 5% as the 9-coordinate [Er(EDTA)(H2O)3](-) ones as well as to calculate the conditional hydration equilibrium constant (Kaqua) of the reaction: [Er(EDTA)(H2O)3](-) ↔ [Er(EDTA)(H2O)2](-) + H2O which is rather difficult to determine by using other methods. The Kaqua value was found to be 19 ± 1.

Progressive Structural Complexity in Ferroelectric 1,2,4-Triazolium Hexabromoantimonate(III): Interplay of "Order-Disorder" and "Displacive" Contributions to the Structural Phase Transitions.

Halobismuthates(III) and haloantimonates(III) with the R3MX6 chemical composition create a new and broadly unexplored class of ferroelectric compounds. In this paper, we report the haloantimonate(III) ferroelectric comprising an aromatic (1,2,4-triazolium) cation, i.e., (C2N3H4)3[SbBr6] (TBA). Temperature-resolved structural and spectroscopic studies indicate that TBA undergoes two solid-solid phase transitions between tetragonal [P42/m (I)] and monoclinic [P21/n (II) and P21 (III)] phases. TBA experiences a paraelectric-ferroelectric phase transition at 271/268 K (II-III) driven by "order-disorder" and "displacive" molecular mechanisms. The ferroelectric properties of phase III have been confirmed by hysteresis loop measurement, and additionally, the acentric order has been further supported by second-harmonic generation measurements. Insight into the molecular origins of the ferroelectric polarization was provided by periodic ab initio calculations using the Berry phase approach at the density functional theory (DFT-D3) method level employed for calculations of spontaneous polarization.

Charge density distribution in aminomethylphosphonic acid.

The experimental charge density distribution in aminomethylphosphonic acid has been determined from X-ray diffraction and its topological features have been analyzed. The results have shown that the P-O bonds are highly polarized, moreover the P-OH bond is weaker than the bonds to unprotonated O atoms. These facts have been confirmed by theoretical density functional theory (DFT) calculations, which have shown that the single, strongly polarized bonds within the phosphonate group are modified by hyperconjugation effects.

Analysis of charge density in nonaaquagadolinium(III) trifluoromethanesulfonate - insight into GdIII-OH2 bonding.

The experimental charge-density distribution in [Gd(H2O)9](CF3SO3)3 has been analysed and compared with the theoretical density functional theory calculations. Although the Gd-OH2 bonds are mainly ionic, a covalent contribution is detectable when inspecting both the topological parameters of these bonds and the natural bond orbital results. This contribution originates from small electron transfer from the lone pairs of oxygen atoms to empty 5d and 6s spin orbitals of Gd3+.

Phase transition tuning by Fe(iii)/Co(iii) substitution in switchable cyano-bridged perovskites: (C3H5N2)2[KFexCo1-x(CN)6].

The single-crystals of mixed (C3H5N2)2[KFexCo1-x(CN)6] crystals, with different ratios of x = 0, 0.29, 0.42, 0.51, 0.63, 0.70, 0.85, 1, have been grown from aqueous solutions. The thermal stability of the crystals has been determined using both DTA and TGA analysis. DSC has revealed sequences of structural phase transitions (PTs). We have found four solid phases for the crystals with concentrations x < 0.6 and three phases above these concentrations. The Fe(iii) concentration has been estimated using the SEM technique. We have found the linear relationship of Tcversus the molar concentration of Fe(iii) for the IV → III PT. Based on the obtained results, a phase diagram has been constructed. The mechanism of the structural PTs has been discussed based on the results of dielectric relaxation, NIR, IR and Raman spectroscopyand X-ray measurements. Dielectric switching has been observed for all analysed mixed-crystals. All crystals exhibit ferroelastic properties.

Structural and thermodynamic aspects of hydration of Gd(iii) systems.

X-ray crystal structures of Gd(iii) and Lu(iii) aqua ions as well as their complexes with polyaminopolycarboxylates (EDTA, CDTA, EGTA, DTPA, DOTA) were determined: [Gd(H2O)9](CF3SO3)3, [Gd(H2O)8]Cl3·C10H20O5, [Lu(H2O)8]Cl3·C12H24O6·4H2O, [C(NH2)3][Gd(EDTA)(H2O)3], [C(NH2)3]2[Lu(EDTA)(H2O)2]ClO4·6H2O, [C(NH2)3][Lu(CDTA)(H2O)2]·6H2O, [C(NH2)3][Gd(EGTA)(H2O)]·2H2O, [C(NH2)2(N2H4)][Gd(HDTPA)(H2O)]·2H2O, Na[Gd(DOTA)(H2O)]·4H2O, and K2[Lu(DOTA)]Cl·4.6H2O. The weighted sums of UV absorption spectra of appropriate crystals were used to reproduce the spectra of the Gd(iii) aqueous solutions in the temperature range 276-363 K. It was shown that in aqueous solution the Gd(iii)-EGTA, Gd(iii)-DTPA and Gd(iii)-DOTA complexes exist as almost pure monohydrate [GdL(H2O)]n- species, while in the case of the Gd(iii) aqua ion, Gd(iii)-EDTA and Gd(iii)-CDTA systems the equilibria between variously hydrated species were found. The derived molar fractions of these species were used to determine the ΔG, ΔH and ΔS of hydration. It was shown that these thermodynamic functions may be derived not only from the spectra of the hypersensitive transitions, but from other f-f transitions as well. Next the ΔG, ΔH and ΔS values of hydration for the other Ln(iii)-EDTA systems (where Ln = Pr, Nd, Sm, Eu) were determined. It was found that the ΔG298 values of the dehydration reaction for Ln(iii)-EDTA complexes (where Ln = Pr, Nd, Sm, Eu, Gd, Ho, Er) were almost linearly dependent on the number of 4f electrons in the whole series of lanthanides. Moreover, it was shown that the point, where the ratio of [LnL(H2O)n] : [LnL(H2O)n-1] is equal to 1, shifts along the lanthanide series depending on the ligand denticity - the higher the ligand denticity, the farther the point of the equimolar ratio in the lanthanide series. The presented results are the first systematic experimental study on the thermodynamic description of the hydration equilibrium of Gd(iii) compounds.

[Tobacco smoking influence on the level of sex hormones--animal model]. / Wplyw dymu tytoniowego na poziom hormonów plciowych--model zwierzecy.

Numerous studies warn that women who smoke can suffer from weakened functioning of their ovaries and disturbed synthesis and metabolism of hormones. This may cause many pregnancy complications or premature menopause and osteoporosis. Moreover, smoking disturbs the menstrual cycle, decreases the effectiveness and increases the undesirable effects of the hormone replacement therapy. Tobacco smoke disturbs gametogenesis, ovulation, Fallopian tube transport, fertilization and the implantation of a fertilized cell, which results in the reduction of fertility. The goal of the present thesis was a toxicological assessment of the influence of tobacco smoke on the level of luteinizing hormone, follicle stimulating hormone, progesterone, and estradiol in blood serum of female rats, taking into consideration the phases of their sexual cycle. The experiment utilized a cytological method of determining the phases of the sexual cycle, which enabled the researcher to divide the rats into two groups (exposed to tobacco smoke and unexposed). Each of the groups was further divided into four subgroups with six animals for each phase of the sexual cycle (Proestrus, Estrus, Metestrus, Diestrus). The rats from the first group were exposed to tobacco smoke with the concentration of 1500 mg of Carbon Monoxide (CO) per cubic meter of ambient air (per content of Carbon Monoxide) for 5 days for 6 hours a day. Every day before the exposition at the same time the phases of the sexual cycle of female rats were checked in all of the subgroups. On the last 5th day of the experiment, after the exposition to the smoke, smear tests were conducted. The unexposed group was the control group. The evaluation of the exposition of the animals to tobacco smoke was based on the determination of the level of cotinine in blood serum by ELISA method. The measurement of the concentration of hormones was conducted by means of a jurisdiction method of electrochemiluminescence. In the experiment, a statistical difference was observed between the concentration of cotinine in the blood serum of the animals that were in the Proesrtus phase (86.8 ng/ ml), compared to the group in the Metestrus phase (351.0 ng/ml) and Diestrus phase (304.6 ng/ml). In the experiment a very high level of progesterone concentration was marked in the blood serum of the female rats that were exposed to tobacco smoke and that were in the Proestrus phase (195.1 ng/ml). The level of progesterone among the animals exposed to cigarette smoke was statistically higher compared to the control group (99.1 ng/ml). In all probability, this was caused by the slower metabolism of nicotine or faster biotransformation of cotinine. The experiment confirmed the negative influence of cigarette smoke on the course of the sexual cycle. The sexual cycle of the female rats exposed to tobacco smoke changed its rhythm and kept its proper course only in 29% of the examined animals.

Eu(iii) and Cm(iii) tetracarbonates - in the quest for the limiting species in solution.

The structural and spectroscopic properties of the compounds [C(NH2)3]5[Gd:M(CO3)4(H2O)]·0.75H2O (1) and [C(NH2)3]5[Y:M(CO3)4]·2H2O (2) (M = Eu, Cm) were determined. The crystals contain differently hydrated tetracarbonate complexes, [M(CO3)4(H2O)]5- and [M(CO3)4]5-, which were used as structural and spectroscopic models of Eu(iii) and Cm(iii) tetracarbonate species in aqueous solutions. The luminescence spectra of the crystals were used to establish the stoichiometry and stability of the limiting species of the aqueous Eu(iii) and Cm(iii) carbonate systems at different temperatures and in a broad range of ionic strengths. By implementing this method together with the Pitzer approach used for the description of highly concentrated systems, it was possible to determine the thermodynamic functions of the reaction [Eu(CO3)3]3- + CO32- ⇆ [Eu(CO3)4]5- under standard conditions for the first time (ΔH° = 31.4 ± 2 kJ mol-1 and ΔS° = 82 ± 10 J mol-1 K-1). The proposed model for Eu(iii) carbonates is consistent with the data recorded for the Cm(iii)-carbonate systems. The presented results are important not only from the point of view of environmental issues, but also for the coordination chemistry of f-elements in general.

From structural properties of the EuIII complex with ethylenediaminetetra(methylenephosphonic acid) (H8EDTMP) towards biomedical applications.

Crystals of Eu(III) with ethylenediaminetetra(methylenephosphonic acid) (H(8)EDTMP) and with ethylenediaminetetraacetic acid (H(4)EDTA) have been synthesized in the same experimental conditions and their X-ray analyses have been performed. The EDTMP ligand wraps the Eu(III) ion in a fashion similar to its carboxylic analogue, EDTA, i.e. coordinating through two nitrogen atoms and four oxygen atoms in such a way that only one oxygen atom from each phosphonate group is bonded to the central ion. The coordination sphere is completed by two oxygen atoms of the bidentate carbonate anion in the case of the Eu(III)-EDTMP complex, whereas the inner sphere of the Eu(III)-EDTA crystal is completed by three water molecules. Spectroscopic studies (UV-Vis and (31)P NMR spectra) of Eu(III)-EDTMP solutions at controlled pH showed that the replacement of inner sphere water molecules and/or OH hydroxy groups by a carbonate anion in the Eu(III)-EDTMP complex at physiological pH results in the formation of [Eu(EDTMP)(CO(3))](7-) species which is thermodynamically stable and kinetically inert. The affinity of the carbonate anion towards the Eu(III)-EDTMP species was studied by analysis of f-f intensities and luminescence decay rates. The dissociation constant of the Eu(III)-EDTMP-carbonate complex was found to be approximately 43 mM. The presented results may be helpful in understanding the role played by the (153)Sm(III)-EDTMP complex known as Quadramet in the seeking of metastatic tissue in bones as well as possibly giving some premises for future ligand design of these types of complexes with lanthanide radionuclides.

Coordination ability of trans-cyclohexane-1,2-diamine-N,N,N',N'-tetrakis(methylenephosphonic acid) towards lanthanide(III) ions.

The proton and metal complex equilibria of trans-cyclohexane-1,2-diamine-N,N,N',N'-tetrakis(methylenephosphonic acid) (CDTP) with lanthanide(iii) ions, where Ln(III) = La(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Ho(III) and Lu(III) were studied. The stoichiometry, protonation and complex formation constants were determined by potentiometric titration at 25.0 degrees C and ionic strength of 0.1 mol dm(-3) (KCl). All metal ions form several species: [LnH4L]-, [LnH3L](2-), [LnH2L](3-), [LnHL](4-), [LnL](5-), [LnH(-1)L](6-) and [LnH(-2)L](7-) in the pH range between 2 and 11. The stability constants log beta(LnL) were found to be between 14.7 and 16.7. The studied complexes were also characterized by spectroscopic methods (31P NMR, UV-Vis absorption and emission spectroscopy). These studies allowed to reveal a distinct structural change of the Ln(III)-CDTP complex which occurs between protonated and hydroxy species in solutions at pH around 7.5. The major change is caused by the involvement of both nitrogen donors in the metal ion coordination occurring in ML species. The data obtained from UV-Vis spectroscopy allowed to draw conclusions about complex symmetry and to estimate a number of coordinated water molecules. The hydration number or more precisely the number of two OH oscillators was found to be approximately one in all species formed over the pH range between 5 and 10. The structure of the major hydroxy complex was supported by X-ray crystallographic data. The crystal structures of the Eu(III) and Tb(III) complexes clearly show that the CDTP ligand is coordinated to the Ln(III) ion by two nitrogen and four oxygen atoms in such a way that only one oxygen atom from each phosphonic group is placed in the lanthanide inner sphere. The monomeric complex anion is connected to a symmetry related ion through short hydrogen bonds formed by two hydroxy ions and one water molecule. In this way the two neighbouring anions form a quasi-dimer in which one of the Ln(III) ion is seven-coordinate (two N atoms, four O atoms and one hydroxy ion) and the other is eight-coordinate (two N atoms, four O atoms, one hydroxy ion and one water molecule).