Nitrile IR intensities characterize electric fields and hydrogen bonding in protic, aprotic, and protein environments

Nitriles are widely used as vibrational probes; however, the interpretation of their IR frequencies is complicated by hydrogen bonding (H-bonding) in protic environments. We report a new vibrational Stark effect (VSE) that correlates the electric field projected on the nitrile bond to the transition dipole moment and, by extension, the nitrile peak area or integrated intensity. This linear VSE applies to both H-bonding and non-H-bonding interactions. It can therefore be generally applied to determine electric fields in all environments. Additionally, it allows for semi-empirical extraction of the H-bonding contribution to the blueshift of the nitrile frequency. Nitriles were incorporated at H-bonding and non-H-bonding protein sites using amber suppression, and each nitrile variant was structurally characterized at high resolution. We exploited the combined information now available from variations in frequency and integrated intensity and demonstrate that nitriles are a generally useful probe for electric fields.

Computational studies on Emodin (C15H10O5) from Methanol extract of Pteridium acquilinum leaves

This research isolates, characterizes, and studies the computational and frequency calculations of emodin, extracted from the leaf extract of Pteridium acquilinum leaves using methanol. Vacuum liquid and tin layer Chromatography was used for the purification of the molecule. The (VLC purified), fraction was analyzed by Nuclear magnetic resonance (NMR) and the chemical structure of the compound isolated (anthraquinone), was confirmed by 1H & 13C-NMR analyses as emodin (C15H10O5). Computational and frequency studies have been done on the isolated molecule. Optimized geometry, IR frequencies, Bond distances (R) and angles (A), Dipole moments and other parameters have been computationally determined for the isolated molecule from quantum chemical calculations using the GAUSSIAN 09 retinue programs. Experimentally determined and computationally measured IR frequencies agree perfectly with each other. Computational studies can be used to predict unobserved chemical phenomena like design of new drugs and materials such as the positions of constituent atoms in relationship to their relative and absolute energies, electronic charge densities, dipoles, higher multiple moments, vibrational frequencies, relativity or other spectroscopic quantities and cross sections for collision with other molecules. This is the first time this anthraquinone, [emodin], with most of the parameters examined is reported from P. aquilinum.

Vibrational Study, Reinvestigation of the Crystal Structure of MgHPO4.3H2O and Calculated IR Frequencies for the PO43- by Isotopic Substitutions

The monohydrogenomonophosphatetrihydrate of magnesium MgHPO4.3H2O was reinvestigated by X-ray diffraction, vibrational spectroscopy, nuclear magnetic resonance and calculation of the IR frequencies by using isotopic substitutions. MgHPO4.3H2O is orthorhombic, space group Pbca with the following unit-cell parameters: a = 10.0133(2) Å, b= 10.2136(1) Å, c =10.6853(2) Å, Z = 8 and V = 1092.81(3) Å3. Raman and infrared spectra of MgHPO4.3H2O have been recorded and interpreted on the basis of factor group analysis. The occurrence of the four frequencies ν1, v2, v3, v4 in the vibrational spectra confirms the existence of the PO43− tetrahedron.

The Impact of Cation Distribution on The Structural and Magnetic Properties of Nonstoichiometric Co0.5Ni0.5+xFe2-xO4 Nanoferrites

In this work, the impact of nonstoichiometric substitution of Fe3+ cations by Ni2+ ones on the structural and magnetic properties of Co0.5Ni0.5+xFe2-xO4 (0.0 ≤ x ≤ 0.4) nanoferrites synthesized by citric autocombustion method. The cubic phase purity for sintered samples were verified by XRD patterns and FTIR spectra. The crystallite size and microstrain were deduced using Williamson-Hall method. The estimated crystallite size ranges from 55 to 89 nm in agreement with TEM microimages. Hysteresis loops traced using VSM prevailed a regular reduction of saturation magnetization with Ni substitution. Relied on the experimental data of XRD, FTIR, and VSM, cation distribution has been suggested, according to which the nonstoichiometric substitution was compensated by the appearance of higher valance states of Fe, Ni, and Co cations. The suggested cation distribution successfully explained the recorded data of lattice parameter, crystallite size, IR frequencies, magnetization and coercivity.

Modeling the Effect of Hydration on the Electronic and Vibrational Properties of AZT

The 3'-azido-3'-deoxythymidine, which is termed AZT, was introduced as anti-human immunodeficiency virus HIV. AZT is supposed to interact with water molecules forming two hydration shells. In the first shell, five water molecules were surrounding five active sites. Each water molecule then further interacted with two water molecules forming the second hydration shell. The computational note is dedicated on the basis of density functional theory (DFT). So that, DFT:B3LYP/6-31G(d,p) was used to follow up on the changes in AZT as a result of hydration. The DFT was used to calculate total dipole moment (TDM), HOMO/LUMO bandgap energies, molecular electrostatic potential (MESP), and IR frequencies.

Using fine-structured gratings to implement mid-infrared dual-band absorbers

A dual narrowband absorber operating at mid-infrared (mid-IR) frequencies was numerically investigated. The structure consists of a fine-structured silicon grating on a gold film. Each unit cell of the fine-structured silicon grating is composed of two different silicon bars. When illuminated by a transverse-magnetic (TM) polarized plane wave, the absorber will create two absorption bands. At normal incidence, the two absorption bands have respective peak wavelengths of ∼3.864 µm and ∼3.994 µm, and respective bandwidths of ∼28 nm and ∼36 nm. The level of absorption can be higher than 0.998. It is shown that the two absorption bands are related to different silicon bars in each unit cell. Moreover, the physical origin of the two absorption bands is attributed to the different surface-plasmon-polariton (SPP) modes excited in the absorber.