Transitions Of Complexes Research Articles

Mesogenic Structures, Lyotropic and Thermotropic Phase Transitions in Demethyl-Ionene Alkyl Sulfonate Complexes.

Linear [B,10]-polyamines [(CH2)BN(CH3)(CH2)10N(CH3)] were prepared (B = 3 or 6). Protonated by stoichiometric amounts of n-alkylsulfonic acids, they form demethyl-ionene sulfonate complexes, which proved thermally stable up to 220 °C. Salt free complexes were investigated by polarized microscopy, thermogravimetry, and X-ray diffraction. Except the heptyl sulfonate, which crystallized, all complexes bearing longer alkyl chains formed mesogenic phases. Being isotropic in dry state, they became optically anisotropic when exposed to humidity due to a lyotropic transition (mediated by the gas phase) to a hexagonal phase, mostly. A cubic phase containing less water was also observed. Anisotropic complexes again were converted to an isotropic state upon heating under controlled humidity. The clearing temperatures distinctly depend on humidity and rise with increasing length of the alkyl sulfonate. This may allow the use of the complexes as humidity sensors. Oriented liquid crystalline samples are formed upon fast cooling in flat capillaries.

The lifetime of the actomyosin complex in vitro under load corresponding to stretch of contracting muscle.

During eccentric contraction, muscle is lengthening so that the actin-myosin cross-bridges bear a load that exceeds the force they generate during isometric contraction. Using the optical trap technique, we simulated eccentric contraction at the single molecule level and investigated the effect of load on the skeletal actomyosin lifetime at different ATP concentrations. The range of the loads was up to 17pN above the isometric level. We found that the frequency distribution of the lifetime of the actin-bound state of the myosin molecule was biphasic: it quickly rose and then decreased slowly. The rate of the slow phase of this distribution increased with both the load and the ATP concentration. The fast phase accelerated sharply with the load, but it was independent of ATP concentration. The presence of the fast phase demonstrates that some transition(s) in the actomyosin complex occur before the myosin head becomes able to bind ATP and detach from actin. Its high sensitivity to the load indicates that the transition is load-dependent.

Gadolinium ion pairs in Pb5Ge3O11: EPR investigation

It has been found that a symmetric group of weak satellites of the 1/2 ↔ −1/2 signal of the trigonal Gd3+ center in lead germanate observed in a wide temperature range is caused by transitions of paired complexes of gadolinium ions coupled by the magnetic dipole-dipole interaction.

Infrared study and phase transformation of the new lithium–diphenyl carbazide complex (LiDPC)

A complete IR investigation (400–4000cm−1) of orthorhombic, amorphous DPC and crystalline LiDPC (at room temperature and 80°C) is performed and new results are reported. Introducing lithium ions into diphenyl carbazide C13H14N4O forms a completely new complex associated with new properties. The IR spectroscopic analysis includes measurements and interpretation of the IR spectral band shape, intensities, and frequencies of the internal modes of vibrations.The principle modes of vibrations of amorphous DPC found to be 3445cm−1, 3292cm−1, 3052cm−1, 1670cm−1, 1602cm−1, 1495cm−1, 1305cm−1, 1254cm−1, 974cm−1, and 577cm−1 correspond to normal vibrations of NH, CH, NN, CO and monosubstituted benzene. A marked change could be recorded for these modes of vibrations in the presence of Li+ ions. The results strongly confirm the formation of a metal–organic complex. Anomalous spectroscopic changes could be recorded in LiDPC spectra. A proposed Li+ position in LiDPC complex is proposed. X-ray diffraction analysis is used to find out the crystal structure and parameters of LiDPC complex. The results obtained show triclinic crystal structure with a=5.6929Å, b=7.6378Å, c=17.8739Å, α=119.176°, β=63.322°, γ=85.378°. The results reveal the presence of an order–disorder phase transition in LiDPC complex at 60°C. The transformation process is monitored by clear variations in the spectral shape, band intensities and new eight different modes appeared in the high temperature disordered phase. An energy model is suggested for the interpretation of such phase transition process.

Composite localized modes in discretized spin–orbit-coupled Bose–Einstein condensates

We introduce a discrete model for binary spin–orbit-coupled Bose–Einstein condensates trapped in a deep one-dimensional optical lattice. Two different types of the couplings are considered, with spatial derivatives acting inside each species, or between the species. The discrete system with inter-site couplings dominated by the spin–orbit coupling (SOC), while the usual hopping is negligible, emulates condensates composed of extremely heavy atoms, as well as those with opposite signs of the effective atomic masses in the two components. Stable localized composite states of miscible and immiscible types are constructed. The effect of the SOC on the immiscibility–miscibility transition in the localized complexes, which emulates the phase transition between insulating and conducting states in semiconductors, is studied.

Proton-Coupled Electron Transfer During the S-State Transitions of the Oxygen-Evolving Complex of Photosystem II.

The oxygen-evolving complex (OEC) of photosystem II (PSII) is a unique Mn4O5Ca cluster that catalyzes water oxidation via four photoactivated electron transfer steps. As the protein influence on the redox and protonation chemistry of the OEC remains an open question, we present a classical valence model of the OEC that allows the redox state of each Mn and the protonation state of bridging μ-oxos and terminal waters to remain in equilibrium with the PSII protein throughout the redox cycle. We find that the last bridging oxygen loses its proton during the transition from S0 to S1. Two possible S2 states are found depending on the OEC geometry: S2 has Mn4(IV) with a proton lost from a terminal water (W1) trapped by the nearby D1-D61 if O5 is closer to Mn4, or Mn1(IV), with partial deprotonation of D1-H337 and D1-E329 if O5 is closer to Mn1. In S3, the OEC is Mn4(IV) with W2 deprotonated. The estimated OEC Em's range from +0.7 to +1.3 V, enabling oxidation by P680(+), the primary electron donor in PSII. In chloride-depleted PSII, the proton release increases during the S1 to S2 transition, leaving the OEC unable to properly advance through the water-splitting cycle.

Re-evaluating the Cu K pre-edge XAS transition in complexes with covalent metal-ligand interactions.

Three [Me2NN]Cu(η2-L2) complexes (Me2NN = HC[C(Me)NAr]2; L2 = PhNO (2), (3), PhCH[double bond, length as m-dash]CH2 (4); Ar = 2,6-Me2-C6H3; ArF = 3,5-(CF3)2-C6H3) have been studied by Cu K-edge X-ray absorption spectroscopy, as well as single- and multi-reference computational methods (DFT, TD-DFT, CASSCF, MRCI, and OVB). The study was extended to a range of both known and theoretical compounds bearing 2p-element donors as a means of deriving a consistent view of how the pre-edge transition energy responds in systems with significant ground state covalency. The ground state electronic structures of many of the compounds under investigation were found to be strongly influenced by correlation effects, resulting in ground state descriptions with majority contributions from a configuration comprised of a Cu(ii) metal center anti-ferromagentically coupled to radical anion O2, PhNO, and ligands. In contrast, the styrene complex 4, which displays a Cu K pre-edge transition despite its formal d10 electron configuration, exhibits what can best be described as a Cu(i):(styrene)0 ground state with strong π-backbonding. The Cu K pre-edge features for these complexes increase in energy from 1 to 4, a trend that was tracked to the percent Cu(ii)-character in the ground state. The unexpected shift to higher pre-edge transition energies with decreasing charge on copper (Q Cu) contributed to an assignment of the pre-edge features for these species as arising from metal-to-ligand charge transfer instead of the traditional Cu1s → Cu3d designation.

Zwitterionic structures of selenocysteine-containing dipeptides and their interactions with Cu(II) ions

AbstractThe molecular structures of a series of selenocysteine-containing dipeptides in their zwitterionic forms were studied using the B3LYP/6-311++G(d,p) level in the aqueous phase. The B3LYP and BHandHLYP functionals in combination with 6-311++G(d,p) and LANL2DZ basis sets were used to investigate the effects of metal coordination on the structural and molecular properties of the dipeptides by complexing them with bivalent copper ions. The results from this DFT study provide valuable insights into the interaction enthalpies (metal ion-binding affinities) and free energies, the influence of the C-terminal moiety on the backbone structural features, the existence of various types of intramolecular H-bond interactions, harmonic vibrational frequencies, along with various other electronic properties pertaining to the zwitterions of the dipeptide molecules as well as their metallic complexes. Metal coordination via the carboxylate groups tends to enhance the planarity of the amide planes. The participations of the N- and C-terminal side-chain moieties in metal-binding markedly enhance the thermodynamic stability of the metalated dipeptides. The theoretical λmax values, calculated using the TD/DFT level for all the systems, well represent the occurrence of d-d transitions in the Cu-dipeptide complexes

Cooperativity in spin-crossover transition in metalorganic complexes: Interplay of magnetic and elastic interactions

It is of significant technological interest to have an understanding of cooperativity in spin-crossover phenomena observed in metalorganic polymeric complexes. Microscopic origin of this cooperativity has been discussed in literature primarily in terms of elastic interactions. Through Monte Carlo simulation of the model Hamiltonian we show that the superexchange interactions between localized magnetic moments at spin-crossover sites can play a crucial role in cooperativity, depending on the nature of the elastic interactions. While in the case of the effective elastic interaction of ferroelastic nature, inclusion of the above-mentioned exchange interaction produces quantitative changes in the hysteresis loop, for effective elastic interaction of antiferroelastic nature, the existence of hysteresis is found to be dictated entirely by the magnetic exchange interaction. Considering the example of a real material, namely Fe-triazole, employing the material-specific density functional theory calculation, we show the later scenario to be true for these systems. Our study should motivate further investigation on the role of magnetic exchanges in metalorganic polymers.

Linewidths and line shapes in the vicinity of graphene.

It is well known that graphene, by virtue of its pi-cloud delocalization, has a continuum of electronic energy states and thus behaves nearly like a metal. Instances involving quenching of electronic energy excitation in fluorophores placed in the proximity of graphene sheets are well documented. In this paper, we perform theoretical investigations on the broadening of vibrational and electronic transitions in the vicinity of graphene. We find that for CO vibrations in the vicinity of undoped graphene, the broadening at a distance of 5 Å is ∼0.008 cm(-1) (κ̃=2, κ̃ being the effective dielectric constant). In comparison, for electronic transitions, the linewidth is much larger, being of the order of several cm(-1). Also, if the transition dipole were parallel to the graphene sheet, the linewidth would be reduced to half the value for the case where it is perpendicular, an observation which should be easy to check experimentally for electronic transitions. This should be observable for the f - f transitions (which are rather narrow) of Lanthanide complexes placed within a distance of a few nanometers from a graphene sheet. Further the linewidth would have a (distance)(-4) dependence as one varies the distance from graphene.

Eukaryotic translation initiation factor eIF5 promotes the accuracy of start codon recognition by regulating Pi release and conformational transitions of the preinitiation complex.

eIF5 is the GTPase activating protein (GAP) for the eIF2·GTP·Met-tRNAiMet ternary complex with a critical role in initiation codon selection. Previous work suggested that the eIF5 mutation G31R/SUI5 elevates initiation at UUG codons by increasing GAP function. Subsequent work implicated eIF5 in rearrangement of the preinitiation complex (PIC) from an open, scanning conformation to a closed state at AUG codons, from which Pi is released from eIF2·GDP·Pi. To identify eIF5 functions crucial for accurate initiation, we investigated the consequences of G31R on GTP hydrolysis and Pi release, and the effects of intragenic G31R suppressors on these reactions, and on the partitioning of PICs between open and closed states. eIF5-G31R altered regulation of Pi release, accelerating it at UUG while decreasing it at AUG codons, consistent with its ability to stabilize the closed complex at UUG. Suppressor G62S mitigates both defects of G31R, accounting for its efficient suppression of UUG initiation in G31R,G62S cells; however suppressor M18V impairs GTP hydrolysis with little effect on PIC conformation. The strong defect in GTP hydrolysis conferred by M18V likely explains its broad suppression of Sui− mutations in numerous factors. We conclude that both of eIF5's functions, regulating Pi release and stabilizing the closed PIC conformation, contribute to stringent AUG selection in vivo.

Quantum-Chemical Modeling of Nickel Interaction with Acrylic Acid

Quantum-chemical modeling of system Niz+ – H2O – HAk (z=+2, +1, 0) using DFT-methods allowed to prove the mechanism of the processes of Ni2+-ions electroreduction in the presence of acrylic acid (HAk). It has been shown that the initial structure is an octahedral complex [Ni2+(H2O)5Ak-], the intermediate is the complex [Ni+(H2O)2Ak-] and the final product exists in three forms: [Ni0(H2O)2Ak], [Ni0(H2O)2(σ-HАk)], [Ni0(H2O)2(π-HАk)].Due to this, the result of еn– type unsaturated organic compounds effect on nickel electrocrystallization process is not simple and depends on the nature and intensity of the effect of external factors.Nickel electrodeposition is a widespread process in electroplating industry due to a number of important properties of this metal. Electrolytes for nickel electrodeposition are used with various organic additives depending on the intended use of the coating [1]. The substances which contain a double -С=С-bond in their structure are often used as additives in the nickel-plating solutions. Molecules of such organic compounds involve centers with surplus electron density. Due to the fact that the electronic structure of nickel contains a vacant d-orbital, organic molecules tend to form a rather strong π-bond with metal ions and even with atoms [2]. As a result of this interaction the above-mentioned type of organic compounds influences effectively on the metal electrocrystallization process. Acrylic acid (HAk) was chosen as an object of reserch.Quantum-chemical modeling was carried out in WinGAMESS program using nonemperical methods. Cluster systems were calculated using B3LYP DFT method. We used 6-31G** basis set for metal atoms and 6-311G basis set for the atoms of ligands. In the article [3] it was shown that this calculation methodology provides high adequacy of the chousen model to the real processes involving 3d metals.Parameters of the optimized structures are listed in the table I and II. TABLE I. Interatomic distances (Å) between nickel and oxygen atoms in the cluster [Niz +(H2O)5Ak-] Atom number Ligand z = +2 z = +1 z = 0 O1Н2О2.0463.7473.339O2Н2О2.0433.6463.302O3Н2О2.0793.6473.557O4Н2О2.0582.0272.063O5Н2О2.0431.9782.071O6СH2=CH-COO- 2.0321.8862.103O7СH2=CH-COO- 3.3433.4652.112 TABLE II. Interatomic distance (Å) between nickel atom and some atoms of ligands in the cluster [Ni0(H2O)5HAk] (distances of more than 4 Å are not given) Atom number Ligand σ-complex π-complex O1Н2О3.341–O2Н2О3.446–O3Н2О3.611–O4Н2О2.0012.009O5Н2О2.0491.984O6СH2=CH-COOН2.0642.030O7СH2=CH-COOН2.228–С3СH2=CH-COOH–2.020 For Ni2+ ions the optimized structure is an octahedral complex with almost equivalent Ni–O bonds (Table I). Transition to Ni+ ions is accompanied by significant reorganization of inner coordination sphere of the complex (Table I). The central atom directly bonds only with two from five water molecules. The newly-formed structure [Ni+(H2O)2Аk-] is characterized by irregular allocation of electron density. Bond distance between nickel atom and oxygen atom of carboxyl group decreases from 2.032 Å to 1.886 Å, which indicates that the bond becomes significantly stronger.As a result of complete reduction of nickel ions the central atom in the complex [Ni0(H2O)2Аk-] increases the coordination number from 3 to 4 (Table I). The second oxygen atom of the carboxyl group (O7) is attracted by nickel atom forming a strong bond which is approximately the same as Ni–O6 bond.At the same time, for Ni0complexes the structures with molecular form of HAk are also identified as stable. In these complexes there occurs σ- and π-coordination of HAk with nickel atom (Table II).Based on the analysis of energies of all listed structures we have proposed the most tipical reaction route of the process of Ni2+ions electroreduction in the presence of acrylic acid: +ē +ē[Ni2+(H2O)5Аk-] → [Ni1+(H2O)2Аk-] → [Ni0(H2O)2Аk-] [1] -3H2O +H3O+ [Ni0(H2O)2Аk-] → [Ni0(H2O)2(σ-HАk)] → [Ni0(H2O)2(π-HАk)] [2]It is obvious that external influences, which are realized during nickel electrodeposition, will change the balance of the above-mentioned forms. As a result they will have an effect on the properties of the metal phase which is formed in the presence of е n– type unsaturated organic substances.References G.A. Di Bari Nickel plating // Metal Finishing, p. 209 – 225, Vol. 103, № 6. (2005)E. Fisher. G. Werner. Metal π-Complexes. – p. 264, Elsevier publishing, New York (1968)V.A Seredyuk. and V.F Vargalyuk. Estimation of Reviability of Quantum-Chemical Calculations of Electronic Transitions in Aqua Complexes of Transition Metals // Russian Journal of Electrochemistry. Vol.44, № 10, p. 20 – 27. (2008)

Profiles of (υ′;υ″ = 0) bands recorded in excitation spectra using b30+u ← X10g+ transitions in Cd2 and B31 ← X10+ transitions in CdAr

Profiles of the (υ′;υ″ = 0) vibrational bands recorded using the b30+u ← X10g+ and B31 ← X10+ transitions in Cd2 and CdAr complexes, respectively, are presented and analysed. Specifically, CdAr and Cd2 complexes are simultaneously propagating in a supersonic beam. Transitions in these complexes can be used to provide the conditions for selective detection of one of the complexes in the expansion. Extended analysis of the B31- and b30+u -state vibrational progressions provided improved values for ω′ex′e and ω′e vibrational characteristics, as well as D′e well depths and Re′ bond lengths of the B31- and b30+u-state potentials. Several of the CdAr bands were recorded with partly resolved rotational structure. The new characterisation of the B31 state, along with results of the rotational and isotopic analyses of the band profiles, agrees with the most recent results of ab initio calculations, while results obtained for the b30+u state call for improvement in the ab initio calculations for Cd2.

Optical transitions in the light-harvesting complexes of bacterial photosynthetic centers

The geometric parameters of the model structure of the bacterial photosynthetic center, which consists of a light-harvesting antenna complex, a reaction center, lipid layers, and the solvation shells of water molecules, were optimized using quantum mechanics-molecular mechanics (QM/MM). The optical absorption spectra of the bacteriochlorophyll were evaluated in the quantum subsystem. It was shown that the shift of the absorption bands towards longer wavelengths as compared to the spectrum of the individual bacteriochlorophyll molecules is characteristic of the cluster of pigment molecules that are found in the antennas.

Evolution of ferroelectricity in tetrathiafulvalene-p-chloranil as a function of pressure and temperature.

The neutral-to-ionic phase transition in the mixed-stack charge-transfer complex tetrathiafulvalene-p-chloranil (TTF-CA) has been studied by pressure-dependent infrared spectroscopy up to p = 11kbar and down to low temperatures, T = 10K. By tracking the C=O antisymmetric stretching mode of CA molecules, we accurately determine the ionicity of TTF-CA in the pressure-temperature phase diagram. At any point, the TTF-CA crystal bears only a single ionicity; there is no coexistence region or an exotic high-pressure phase. Our findings shed new light on the role of electron-phonon interaction in the neutral-ionic transition.

Ruthenium complexes of hexakis(cyanophenyl)[3]radialenes and their di(cyanophenyl)methane precursors: synthesis, photophysical, and electrochemical properties

The coordination chemistry of cross-conjugated ligands and the effect of cross-conjugation on the nature of metal–metal and metal–ligand interactions have received limited attention. To explore the effects of cross-conjugation eight ruthenium complexes were synthesized, mononuclear complexes of two isomeric cross-conjugated [3]radialenes [RuCp(PPh3)2(L)]PF6 and [{RuCp*(dppe)}(L)]PF6 (L = hexakis(4-cyanophenyl)[3]radialene, 2; hexakis(3-cyanophenyl)[3]radialene, 3), and dinuclear complexes [{RuCp(PPh3)2}2(L)](PF6)2 and [{RuCp*(dppe)}2(L)](PF6)2 of the diarylmethane precursors (L = 4,4′-dicyanodiphenylmethane, 4; 3,3′-dicyanodiphenylmethane, 5) to the [3]radialenes. Considerable synthetic challenges allowed only clean isolation of mononuclear complexes of the multidentate radialenes 2 and 3. As expected, coordinating a positively charged metal induces a red shift for the π–π* transition in complexes of ligand 2, but unexpectedly a blue shift for the same transition in complexes of 3 was observed. This points to conformational differences for the [3]radialene in the ruthenium complexes of the para- (2) versus meta- (3) substituted hexaaryl[3]radialenes. Cyclic voltammetry indicates that the methylene spacer in 4 and 5 does not enable any interaction between metal centers and the absorption behavior is essentially as observed for [Ru(NCPh)(PPh3)2Cp]PF6 and [Ru(NCPh)(dppe)Cp*]PF6 but generally with a slight red shift in absorbance maxima.

Organic light‐emitting materials based on iridium(III) complexes bearing phenanthroimidazole ligands

We present the elegant synthesis and the photophysical and electroluminescent properties of a series of cyclometalated iridium(III) complexes [Ir(PPI)2(pic), PPI: 1,2‐diphenyl‐1H‐phenanthro[9,10‐d]imidazole; pic: picolinic acid]. The Ir(PPI)2(pic) complexes showed characteristic phosphorescence with an emission range of 556–579 nm and a high quantum efficiency with microsecond lifetimes. The strongly allowed phosphorescence in these complexes is the result of significant spin–orbit coupling of the Ir center. All bis(PPI) derivatives exhibit intense triplet metal‐to‐ligand charge transfer (MLCT) photoluminescence in the fluid solutions at room temperature. The impact of different solvents, substituents on the phenanthroimidazole ligands and complex concentrations upon their emissive behavior have been examined and demonstrate that their emission energies can be systematically modified. Weak bands located at longer wavelength have been assigned to the 1MLCT ← S0 and 3MLCT ← S0 transitions of iridium complexes. Application of the 3MLCT excited state of the [Ir(PPI)2(pic)] materials in organic light‐emitting devices are described. Copyright © 2014 John Wiley & Sons, Ltd.

A composition-dependent “re-entrant” crystallographic phase transition in the substitutional metal acetylacetonate complex (Cr1−xGax)(acac)3

The formation of a complete solid solution between acetylacetonate (acac) complexes of chromium and gallium, (Cr1−xGax)(acac)3 for 0.1<x<0.9, has been investigated through the co-synthesis method. Well-crystallised, subliming solids are found to form for each nominal value of x, with thermal analysis confirming each composition to have a congruent melting point, making it a substitutional complex. Whereas the pure complexes (i.e. the end members of the solid solution, x=0 and x=1) are both centrosymmetric, a composition-dependent crystallographic phase transition to a non-centrosymmetric structure is found to occur for compositions with 0.4<x<0.9. Such a “re-entrant” crystallographic transition is interpreted to be due to the drive to overcome the disorder present in certain centrosymmetric chromium-rich compositions, by going over to a non-centrosymmetric structure with a doubling of the unit cell. The substitutional complex is shown to lead to a substitutional oxide with the β-gallate structure.

Intermolecular interactions and charge transfer transitions in aromatic hydrocarbon-tetracyanoethylene complexes.

A comprehensive theoretical study of the electronically excited states in complexes between tetracyanoethylene (TCNE) and three aromatic electron donors, benzene, naphthalene and anthracene, was performed with a focus on charge transfer (CT) transitions. The results show that the algebraic diagrammatic construction method to second order (ADC(2)) provides excellent possibilities for reliable calculations of CT states. Significant improvements in the accuracy of the computed transition energies are obtained by using the scaled opposite-spin (SOS) variant of ADC(2). Solvent effects were examined on the basis of the conductor-like screening model (COSMO) which has been implemented recently in the ADC(2) method. The dielectric constant and the refractive index of dichloromethane have been chosen in the COSMO calculations to compare with experimental solvatochromic effects. The computation of optimized ground state geometries and enthalpies of formation has been performed at the second-order Møller-Plesset perturbation theory (MP2) level. By comparison with experimental data and with high-level coupled-cluster methods including explicitly correlated (F12) wave functions, the importance of the SOS approach is demonstrated for the ground state as well. In the benzene-TCNE complex, the two lowest electronic excitations are of CT character whereas in the naphthalene and anthracene TCNE complexes three low-lying CT states are observed. As expected, they are strongly stabilized by the solvent. Geometry optimization in the lowest excited state allowed the calculation of fluorescence transitions. Solvent effects lead to a zero gap between S1 and S0 for the anthracene-TCNE complex. Therefore, in the series of benzene-TCNE to anthracene a change from a radiative to a nonradiative decay mechanism to the ground state is to be expected.

Correlation of resistance switching behaviors with dielectric functions of manganite films: A study by spectroscopic ellipsometry

ABSTRACTPr0.5Ca0.5MnO3(PCMO) films were deposited on LaAlO3(100) substrates under pressure from 1.33 to 5.33 Pa by RF magnetron sputtering. Resistance switching and dielectric functions of PCMO films were studied by DC current-voltage characteristic measurements and spectroscopic ellipsometry (SE) measurements. Resistance switching was observed in the devices composed of PCMO films deposited under low pressures of 1.33 and 2.67 Pa. SE measurements revealed that dielectric functions also depended on deposition pressure. PCMO films deposited under lower pressure had larger high-frequency dielectric constant, larger oscillator strength of the electric dipole charge transitions in MnO6octahedral complexes, and lower oscillator strength ofd-dtransitions in Mn3+and Mn4+ions. SE measurements suggested that oxygen vacancies and MnO6octahedral complexes play an important role in resistance switching in PCMO films.