IR-active Bands Research Articles

Structural and spectroscopic properties, solvation effects, intermolecular interactions, and biological assays of a Mn(II)-complex with 1,10-phenanthroline and chloro ligands

The bis(chloro)-bis(1,10-phenanthroline)-manganese(II) crystalline complex, with the formula [Mn(phen)2Cl2], was synthesized by slow evaporation method. Structural, thermal, and vibrational properties of the crystal were obtained by X-ray powder diffraction (XRPD), thermal analysis, Raman, and Fourier-transform infrared (FT-IR) spectroscopy. XRPD results showed that the crystal belongs to a monoclinic system with P21/c (C2h5) space group. Thermal analyses revealed that the material presents good stability within 300–558 K temperature interval. In addition, Hirshfeld surface analysis revealed the sites involved in intermolecular interactions predominant in the crystal. Also, all Raman and IR-active bands were assigned from computational calculations based on density functional theory (DFT) to analyze intramolecular vibration modes. Additionally, the electronic and vibrational properties were investigated considering three different media (vacuum, methanol, and water) using the integral equations formalism of the polarizable continuum model (IEFPCM). Lastly, the bactericidal assays on Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 25922), Pseudomonas aeruginosa (ATCC 27853) e Enterococcus faecalis (ATCC 25923) were carried out to evaluate the antimicrobial activity of this complex.

FTIR and XRD Characterization of the Cements Available in Commercial Market of Nepal

In the engineering material characterizations and analytical domains where the specific physicochemical properties of the materials are probed through various sophisticated instrumental tools and techniques, the XRD and FTIR spectroscopy stand as the standalone applications as the former discloses the crystallographic structure, crystallite/grain sizes, and the chemical compositions of the specific materials nondestructively while the latter reveals details about the IR active vibrations modes of each covalent bond of their chemical constituents. In the present studies, we employ both of these techniques, and characterize the specifically selected variable manufactured ready-to-use dry OPC type cements available in the commercial markets of Nepal. The former technique derived the specific 2\(\theta\) value deterministic for identifying the closely packed interatomic layers with the significant levels of CaCO3, Ca(OH)2, and arsenic As5+ based AsO43- unit bearing crystalline phases in each samples. The calculated crystallite sizes of them are found as equal as that reported for the calcite based OPC cements, and are directly adopted to depict their utmost intermixing propensities with the carbon dust and hence, act as the most potential evidence of unlocking the possibility of inventing cement-carbon composites based supercapacitors and conductive devices, and of speculating their distinguishable hydration rates and setting times. And, the latter technique produced intense IR active bands in the designated wave number regions are used to confirm their silicate (SiO42-) tetrahedra, amorphous CaCO3 phases & the CO32-unit holding chemical constituents, 2CaO.SiO2 and 3CaO.SiO2 type chemical compounds explicitly. The presence of diffused type IR bands specific to the Al2O3 based chemical compounds signified that all of them contains significant levels of the alumina based hardening elements, but the complete absence of the peak typical to the Mg-O signified that none of them contains magnesia. The similar analyses of the IR bands further reveal that none of them possesses heavy and active type CaCO3, but have trace amounts of the AsO43- based chemical compounds as predicted by the XRD. The intensive peak area and the depth intensity studies of the designated IR bands speculate the dissimilar quantitative proportions and percentage compositions of these chemical constituents in them. The authors believe that the general results presented herewith illuminate the fundamental chemical constituents to be incorporated compulsorily into the OPC type cements so that they function normally and exhibit good cementitious abilities.

Polymorphism at hexadecanoic-acid crystals investigated through structural and vibrational studies

Hexadecanoic acid (HA) is a saturated fatty acid with wide industrial application due to its important chemical and physical properties. However, understanding of its polymorphic characteristics under a specific growth condition is still an open question. This paper shows HA crystals grown by the slow evaporation method with five different solvents. The polymorphism was evaluated by X-ray diffraction, Raman and Fourier-transform infrared (FT-IR) spectroscopy. Most of the crystals presented two main polymorphic phases, and the C polymorphic form common among samples appeared as a progressive increase with increasing solvent polarity. Nevertheless, solvents with slower evaporation allowed to obtain the Bm form as a minor phase. Furthermore, polar solvents with rapid evaporation allowed the growth of the Em form as a secondary phase. Vibrational analysis on the Raman- and IR-active bands indicated that almost all inter-molecular modes are more likely to gauche conformation than all-trans conformation. This behavior is due to changes in the hydrogen bonds (O−H.O) and, mainly, in the C-C bonds around the carboxylic group (COOH) that form the dimers between the pairs of molecules within the crystalline lattice.

A Multi-Attribute Decision-Making Model for the Selection of Polymer-Based Biomaterial for Orthopedic Industrial Applications.

The potential of quantifying the variations in IR active bands was explored while using the chemometric analysis of FTIR spectra for selecting orthopedic biomaterial of industrial scale i.e., ultra-high molecular weight PE (UHMWPE). The nano composites UHMWPE with multi-walled carbon nano-tubes (MWCNTs) and Mg-silicate were prepared and irradiated with 25 kGy and 50 kGy of gamma dose. Principal component analysis (PCA) revealed that first three principal components (PCs) are responsible for explaining the >99% of variance in FTIR data of UHMWPE on addition of fillers and/or irradiation. The factor loadings plots revealed that PC-1 was responsible for explaining the variance in polyethylene characteristics bands and the IR active region induced by fillers i.e., 440 cm−1, 456 cm−1, from 900–1200 cm−1, 1210 cm−1, 1596 cm−1, PC-2 was responsible for explaining the variance in spectra due to radiation-induced oxidation and cross linking, while the PC-3 is responsible for explaining the variance induced because of IR active bands of MWCNTs. Hierarchy cluster analysis (HCA) was employed to classify the samples into four clusters with respect to similarity in their IR active bands which is further confirmed by PCA. According to multi attribute analysis with PCA and HCA, 65 kGy irradiated sample is optimum choice from the existing alternatives in the group of irradiated pristine UHMWPE, UHMWPE/Mg-silicate irradiated with 25 kGy of gamma dose was the optimum choice for UHWMPE/Mg-silicate nano composites, and UHMWPE/γMWCNTs composites containing 1.0% dof γ MWCNTs for UHMWPE/MWCNTs nanocomposites, respectively. The results show the effectiveness of quantifying the variance for decision as far as optimization of biomaterials in orthopedic industrial applications is concerned.

Cryo spectroscopy of N2 on cationic iron clusters.

Infrared photodissociation (IR-PD) spectra of iron cluster dinitrogen adsorbate complexes [Fen(N2)m]+ for n = 8-20 reveal slightly redshifted IR active bands in the region of 2200-2340 cm-1. These bands mostly relate to stretching vibrations of end-on coordinated N2 chromophores, a μ1,end end-on binding motif. Density Functional Theory (DFT) modeling and detailed analysis of n = 13 complexes are consistent with an icosahedral Fe13 + core structure. The first adsorbate shell closure at (n,m) = (13,12)-as recognized by the accompanying paper on the kinetics of N2 uptake by cationic iron clusters-comes with extensive IR-PD band broadening resulting from enhanced couplings among adjacent N2 adsorbates. DFT modeling predicts spin quenching by N2 adsorption as evidenced by the shift of the computed spin minima among possible spin states (spin valleys). The IR-PD spectrum of (17,1) surprisingly reveals an absence of any structure but efficient non-resonant fragmentation, which might indicate some weakly bound (roaming) N2 adsorbate. The multiple and broad bands of (17,m) for all other cases than (17,1) and (17,7) indicate a high degree of variation in N2 binding motifs and couplings. In contrast, the (17,7) spectrum of six sharp bands suggests pairwise equivalent N2 adsorbates. The IR-PD spectra of (18,m) reveal additional features in the 2120-2200 cm-1 region, which we associate with a μ1,side side-on motif. Some additional features in the (18,m) spectra at high N2 loads indicate a μ1,tilt tilted end-on adsorption motif.

Crystal structures and high-temperature and high-pressure vibrational spectra of synthetic fluorine-bearing brucites

Abstract Brucite [Mg(OH)2] has been extensively studied as a simple yet important analog for studying physical and chemical properties of hydrous minerals, and fluorine substitution (OH– = F–) is common in hydrous minerals since the radius of F– is similar to that of O2−. We synthesized two F-bearing brucite samples, Mg(OH)1.78F0.22 and Mg(OH)1.16F0.84, at 9.5 GPa and 1373 K. Single-crystal X-ray diffraction measurements indicate that both phases still crystallize in the space group of P3m1, and fluorine substitution significantly reduces the unit-cell volume, axial lengths, and averaged Mg-O(F) bond lengths. The averaged O···H distances get slightly shortened, and the H-O-H angles become smaller due to the fluorine effect. Additional IR-active OH-stretching bands are observed at 3660, 3644, and 3513 cm−1 for the F-bearing samples, besides the original one at 3695 cm−1. In situ high-temperature and high-pressure Raman and Fourier transform infrared (FTIR) spectra were collected on the F-bearing brucite samples, and comparisons were made with the natural one with 0.7 mol% F–. The temperature dependence [(∂vi/∂T)P] of the OH-stretching modes is inversely correlated to the vibrational frequencies from 3500 to 3700 cm−1, whereas (∂vi/∂P)T is in positive correlation with vi. In addition, the dehydration temperatures of the F-bearing brucites are 100–150 K higher than that for the F-free sample at ambient pressure. By creating new proton positions in lower energies, fluorine substitution stabilizes hydrous minerals (like brucite) to higher temperatures and significantly affects their thermodynamic properties, which has significant implications in mineral physical and geochemical studies.

Crystal chemistry and high-temperature vibrational spectra of humite and norbergite: Fluorine and titanium in humite-group minerals

AbstractThe humite-group minerals along the brucite-olivine join may be important dense hydrous magnesium silicate (DHMS) phases in the subducting slab. Fluorine and titanium can be incorporated into their structures through the substitutions (OH)– = F– and Mg2+ + 2(OH)– = Ti4+ + 2O2–. These substitutions have significant effects on the hydrogen bonding behavior in the structures. Structure refinements and in situ high-temperature Raman and Fourier transform infrared (FTIR) measurements were conducted on natural humite and norbergite crystals. Both minerals crystallize in space group Pbnm, and their isobaric Grüneisen parameters for the lattice and SiO4 internal vibrations are compared with those of chondrodite, clinohumite, brucite, and forsterite. For the humite-group minerals, the OH-stretching modes above 3450 cm–1 are affected by local H-H repulsion, whereas the behavior of those below 3450 cm–1 can be explained by F– and Ti4+ substitutions, either of which may relieve the H-H repulsion effect. The Raman-active OH bands below 3450 cm–1 are affected by Ti4+ substitution, while the IR-active bands can be affected by either F– or Ti4+ substitutions. Based on an analysis of the high-T Raman and FTIR spectra, the OH vibrations above and below 3450 cm–1 behave differently as a function of temperature, and similar behavior has also been observed for other dense hydrous silicate phases in the hydrous peridotite system. Hence, the lengths of the oxygen-oxygen edges in MgO6 octahedra where protonation can occur become similar to each other at elevated temperatures. This may provide an atomistic explanation for the electrical conductivity properties of DHMS phases at high temperatures.

Infrared Spectra of Alunite-Group Minerals Formed on Thermal Fields

IR spectra of alunite-group minerals formed on Pauzhetka–Kambalnyi–Koshelevskii (South Kamchatka) thermal fields were studied. Vibrational spectra were interpreted using correlation diagrams for the mineral structures. The IR-active ν3 bands shifted on going from [AlO6] to [FeO6] from 600, 630, and 670 cm–1 to 500, 530, and 630 cm–1; Raman-active ν1 bands, from 530 to 470 cm–1. Bands of [SO4] vibrations were active in both spectra and practically did not shift on going from MIAl3(SO4)2(OH)6 to MIFe3(SO4)2(OH)6.

Assignment of Infrared-Active Combination Bands in the Vibrational Spectra of Protonated Molecular Clusters Using Driven Classical Trajectories: Application to N4H+ and N4D+

We investigate the utility of the driven molecular dynamics (DMD) approach to complex molecular vibrations by applying it to linear clusters with several degenerate vibrational modes and infrared (IR) intense combination bands. Here, the prominent features in N4H+ and N4D+ IR spectra, reported and described by others previously, have been characterized for the first time by DMD using recently published high-level potential and dipole moment surfaces. Namely, the calculations closely correlate the parallel proton stretch vibration in N4H+, at 750 cm-1, with the one observed experimentally at 743 cm-1. Second, the intense IR-active combination bands found in experimental spectra within 900-1100 cm-1 have been properly recovered by DMD at 950 cm-1 as strongly IR-active and confirmed as consisting of H+ asymmetric stretch and N2···N2 intermolecular symmetric stretch modes. Furthermore, we show that certain combination bands involving overtone transitions may be recovered by DMD using a hard-driving regime, such as the 1409 cm-1 band measured in N4H+, revealed by DMD at 1375 cm-1, and assigned to a progressive combination of the parallel H+ stretch and two quanta of N2···N2 stretch, in agreement with quantum mechanical studies reported previously by others.

Spectroscopic and conductometric behavior of boric acid in water and in an aprotic polar solvent

IR and Raman measurements were carried out for boric acid in water and DMSO. IR-active bands at 1410 and 1150 cm−1, which have been related to the E′ representation, were not observed in the Raman spectrum of the acid in water. At the same time, the 1060 cm−1 band, which should be Raman-active and has been associated to the A′ mode, possesses very low intensity and so is deemed a forbidden transition in the present study. Similar behavior was seen in DMSO, even though the 1150 cm−1 band is shifted to 1124 cm−1. These data allow us concluding that the C3h point group is not adequate for describing the H3BO3 structure, neither in water nor in DMSO. Furthermore, solute-solute interactions take place in water and give rise to [B2O(OH)4] and [B3O3(OH)4]− species, in which the former is experimentally observed for the first time at acidic pH. In DMSO both spectra suggest strong solute-solvent interactions and analyses at the νSO region show that the 1:1 H3BO3:DMSO adduct is the most abundant in the media. Conductivity measurements support the specific interactions in each system.

Cryo Kinetics and Spectroscopy of Cationic Nickel Clusters: Rough and Smooth Surfaces

The stepwise N2 adsorption on size selected Ni9+ and Ni13+ clusters at 26 K is studied in a hybrid tandem ion trap instrument. Adsorption kinetics of these clusters in conjunction with infrared photon dissociation (IR-PD) spectroscopy of their cluster adsorbate complexes allows for the elucidation of various N2 coverage and cluster size dependent effects, which are related to the rough Ni9+ and smooth Ni13+ cluster surface morphologies. Pseudo-first-order kinetic fits confirm consecutive adsorption steps by single exponential decays exclusively. The recorded IR-PD spectra of all observed cluster adsorbate complexes reveal IR active vibrational bands at frequencies of 2170–2260 cm–1, which coincides with the range of metal head-on coordinated N–N stretching modes. Density functional theory (DFT) calculations confirm the experiments and reinforce a possible isomerization with low N2 coverage in the case of Ni9+.

A New, Dispersion-Driven Intermolecular Arrangement for the Benzene-Water Octamer Complex: Isomers and Analysis of their Vibrational Spectra.

The anharmonic spectra of the gas phase cubic water octamer (W8, D2d and S4 isomers) have been theoretically calculated at the second order Møller-Plesset perturbation (MP2) and the coupled cluster with single, double and a perturbative estimate of triple replacements [CCSD(T)] theories. The CCSD(T) harmonic frequencies are the first ones reported for this cluster. An additional band at ∼3500 cm(-1) is reported, in a spectral area that was not previously accessible experimentally due to technical reasons. The IR spectra of the S4 isomer have a larger number of fundamental bands than the spectra of the D2d isomer, in accordance with the presence of lower symmetry in the former compared to the latter. When W8 interacts with benzene (BZ), the dispersion interaction plays a major role in determining the resulting intermolecular arrangement. Calculations at the MP2, DFT (with the ωB97XD functional which includes dispersion corrections) and CCSD(T) levels of theory suggest an optimal arrangement in which BZ is almost parallel to one of the faces of the W8 cube. This structure differs from the previously reported one in which one of the "free" OH bonds of the W8 cube pointed toward the center of BZ (Science 276, 1678 (1997)) that was determined at the DFT level with the dispersionless B3LYP functional and was used to assign the experimentally measured IR spectra. Five low-lying isomers, three of the S4-like and two of the D2d-like type, were determined, and their spectra were assigned. The perturbation of BZ to the W8 vibrational bands amounts to (i) the localization of the normal modes of W8 thus resulting in more IR active bands and (ii) the lowering of the overall symmetry of the complex that results in the splitting of the doubly degenerate bands of the bare W8. Our results further suggest that a future recording of the IR spectra in the HOH bending region can definitively aid in the assignment of the various isomers of both the BZ and the BZ-W8 complexes.

High-Resolution Infrared and Raman Spectra of the Polycrystalline Sinomenine Hydrochloride

High-resolution infrared and Raman spectra of the polycrystalline sinomenine (SM) hydrochloride have been measured to work out its whole really existing vibrational spectral bands. Except for the hydroxyl stretching modes and IR active bands less than 400 cm −1 , most normal modes (about 34) are both IR and Raman active. In addition, 8 Raman bands less than 400 cm −1 are tentatively assigned, for the first time to our knowledge, to stretching/bending modes of the aromatic-ring−methoxyls and (SMH) + –Cl − ions, respectively.

Relationship between the structural characteristics and photoluminescent properties of LnEuTi2O7 (Ln=Gd and Y) pyrochlores

Mixed pyrochlore oxides LnEuTi2O7 (Ln=Gd and Y) were prepared by solid-state reaction and their structures have been confirmed and characterized using X-ray powder diffraction (XRD), Raman, FT-IR and photoluminescence (PL) techniques. Raman spectra and X-ray diffraction patterns revealed the formation of pure oxides after sintering at 1200°C. These compounds were crystallized in a pyrochlore structure A2B2O7 in a cubic lattice with an Fd3m space group and their refined lattice parameters were in the range of 10.197(6)–10.157(4)Å for GdEuTi2O7 and YEuTi2O7, respectively. The X-ray Rietveld analysis indicated that Eu3+ ions were located in the A3+ site with inversion symmetry. The IR active bands, characteristic of the A and B sites of a pyrochlore compound, were detected by infrared spectroscopy due to their metal–oxygen bonds. The samples luminescence properties were analyzed by measuring the excitation and emission spectra. Results indicated that the as-prepared samples showed a strong emission of Eu3+ under their radiation of 325nm. For LnEuTi2O7 oxides, the orange emission at 589nm was the strongest, which corresponded to the magnetic dipole transition 5D0–7F1 due to an energy transfer from hosts. However, the red emissions 5D0–7F2 were very weak because electronic dipole transitions are parity forbidden. This fact also confirmed that the Eu3+ ions were located in the sites with the inversion center.

Annealed SnO2 thin films: Structural, electrical and their magnetic properties

SnO2 thin films of ~150nm thicknesses were deposited on quartz substrate by pulse laser deposition technique and annealed at 600–900°C for 1h with a variation of 100°C per sample. The X-ray diffraction patterns show that as deposited SnO2 thin film was completely amorphous while annealed SnO2 thin films were randomly oriented, polycrystalline in nature and correspond to the rutile phase. The average crystallite size estimated using Scherrer and Williamson–Hall equations was found to increase with annealing temperature. In addition to the three fundamental Raman peaks at 473cm−1, 627cm−1 and 766cm−1 corresponding to the tetragonal rutile phase of SnO2, two IR active Raman bands and one Raman forbidden mode were also observed at 500cm−1, 690cm−1 and 544cm−1 respectively. The dc resistivity measurements in the temperature range of 297–400K show semiconducting behavior of all the annealed thin films. Room temperature dielectric properties of all the samples show dispersion which is explained in the light of Koop's theory based on Maxwell–Wagner two layer models. The dielectric parameters: real part of dielectric constant, dielectric loss and ac conductivity show their maximum value for SnO2 film sample annealed at 600°C. The dielectric loss shows anomalous behavior and exhibits relaxation peaks (Debye peaks) at lower and middle frequencies. Complex impedance plots (Nyquist plots) for annealed SnO2 thin films show two well-resolved semicircles corresponding to two different electrical transport mechanisms which stand for grain and grain boundary. It is observed that the contribution of grains in the conduction process starts dominating over the grain boundary with the increase in annealing temperature. From a magnetic hysteresis loop, it is clear that all the single phase SnO2 thin films annealed at different temperatures are ferromagnetic at room temperature and the value of saturation magnetization shows its maximum for the film annealed at 600°C.

Infrared photodissociation spectroscopy of oxygen-rich Fe(O2)n(+) (n = 3-5) cation complexes.

Infrared spectra of mass-selected oxygen-rich iron dioxygen complexes Fe(O2)n(+) with n = 3-5 are measured via infrared photodissociation spectroscopy in the gas phase. These cation complexes are produced via a laser vaporization supersonic ion source. The structures are established by comparison of the experimental spectra with the simulated spectra derived from density functional calculations. All of the Fe(O2)n(+) complexes studied have a single IR-active band in the 1050-1100 cm(-1) region, arising from the O-O stretching vibration of the superoxo ligand(s). These complexes are determined to have structures with a chemically bound Fe(O2)2(+) core ion that is weakly coordinated by neutral O2 molecules. The Fe(O2)2(+) core ion has a planar D2h symmetry with two equivalent side-on superoxo ligands bound to an Fe(3+) cation center.

Synthesis of Cu<sub>2</sub>O Nanospheres and Cubes: Their Structural, Optical and Magnetic Properties

In this work, synthesis strategy of Cu2O nanosphere and cube was elucidated and the structural, optical and magnetic properties were studied. Cu2O nanospheres and cubes were synthesized by wet chemical method through selecting the appropriate amount of isopropyl alcohol (IPA) with distilled water as solvent. 5% of IPA yielded cubic shape Cu2O and 30% of IPA yielded spherical Cu2O. The phase purity was confirmed with powder XRD. The FTIR result exhibit Cu (I)-O vibrational band around 628 cm-1 supports the XRD results. In Raman spectra weak band at 508 cm-1 corresponds to Raman allowed mode. The IR active bands at 110 and 150 cm-1 are observed because of the violation of selection rules which demonstrates the defects present in synthesized Cu2O. Raman peaks at 218 and 415 cm-1 are assigned to multiphonon Raman scattering. The UV-Vis diffuse reflectance spectrum was recorded to calculate the band gap value. The band gap value calculated using Kubelka-Munk equation was 2.015 eV and 2.025 eV, respectively, for Cu2O cube and nanosphere.

Infrared Photodissociation Spectroscopy of Iron Nitrosyl Cation Complexes: Fe(NO)n+ (n = 1–5)

Infrared spectra of mass-selected mononuclear iron nitrosyl cations Fe(NO)n(+) with n = 1-5 and their argon tagged complexes are measured via infrared photodissociation spectroscopy in the nitrosyl stretching frequency region in the gas phase. The structures are established by comparison of the experimental spectra with the simulated spectra derived from density functional calculations. Two IR active bands were observed for the argon-tagged Fe(NO)2(+) and Fe(NO)3(+) complexes, consistent with theoretical predictions that these complexes have bent C(2v) and nonplanar C(3v) symmetry, respectively. The Fe(NO)4(+) complex was characterized to have a completed coordination sphere with 17 electrons containing a bent one-electron NO ligand and three three-electron NO ligands. The Fe(NO)5(+) complex was determined to involve a Fe(NO)4(+) core ion that is solvated by an external NO molecule.

Preparation of a series of NiL(η2-C60) complexes (L = 1,2-bis(diphenylphosphino)ethane, and 1,1′-bis(diphenylphosphino)ferrocene) by zinc dust reduction

A simple method for preparation of nickel-fullerene coordination complexes has been developed. NiLCl2(Br2) and C60 mixtures are reduced by zinc dust upon heating in o-dichlorobenzene. Diffusion of hexane into the reaction mixture results in formation of crystals of NiL(η2-C60)⋅solvent (L = 1,2-bis(diphenylphosphino)ethane (dppe, 1), 1,3-bis(diphenylphosphino)propane (dppp, 2) and 1,1′-bis(diphenylphosphino)ferrocene (dppf, 3)). Nickel coordinates to the 6–6 bonds of C60 by η2- type and has distorted square-planar geometry. The average Ni–C(C60) bond lengths are 1.936(6)–1.977(3) Å. We found that increase in the P(L)–Ni–P(L) angle and the dihedral angle between the PNiP and CNiC planes results in elongation of the Ni–C(C60) and Ni–P(L) bonds by 0.04–0.06 Å. Complexes 1–3 contain zero-valent nickel since fullerenes are neutral according to the IR- and visible-NIR spectra. Some of the IR-active bands of C60 are split into three bands in spectra of 1–3 due to C60 symmetry lowering, and the F1u(4) C60 mode is shifted to lower wave numbers due to the π-back donation. The formation of 1–3 is accompanied by appearance of new bands in the visible range at 435–447 and 661–680 nm.

Characterization of Dopant Diffusion within Semiconducting Polymer and Small-Molecule Films Using Infrared-Active Vibrational Modes and Attenuated Total Reflectance Infrared Spectroscopy

Understanding dopant diffusion within organic and polymeric semiconductors is of great importance toward the development of organic photovoltaic and electronic devices, many of which require layered structures with controlled doping profiles (e.g., p-n and p-i-n structures). The current paper demonstrates a new method to determine the diffusion and permeability coefficients for dopant diffusion within polymeric and small-molecule organic semiconductors using attenuated total reflectance infrared (ATR-IR) spectroscopy and taking advantage of the intense IR-active vibrational bands created when dopants such as iodine accept charge from a semiconducting polymer to generate polaronic species. The diffusion and permeability coefficients for iodine within poly(3-hexylthiophene) (P3HT) are determined to be 2.5×10(-11)±1.2×10(-11) cm2/s and 2.4×10(-8)±1.2×10(-8) cm2/s·atm, respectively. The approach is applied to P3HT/PCBM (1:1 mass ratio) films, and the diffusion and permeability coefficients through these composite films are determined to be 7.8×10(-11)±2.8×10(-11) cm2/s and 4.8×10(-8)±1.3×10(-8) cm2/s·atm, respectively. Finally, the approach is extended to determining iodine diffusion within the polycrystalline semiconductor tetraphenylporphyrin (TPP) in a bilayer film with P3HT, and the diffusion coefficient of iodine through TPP is determined to be 7.1×10(-14)±1.1×10(-14) cm2/s. Although the current paper determines diffusion and permeability for the dopant iodine, this approach should be applicable to a wide array of dopants and polymeric and small-molecule semiconductors of interest in photovoltaic and electronic applications.