Electronic structure and intramolecular interactions in three methoxyphenol isomers.

Electronic structures and intramolecular interactions of three methoxyphenol positional isomers and their rotamers have been studied using core X-ray photoelectron spectroscopy and quantum mechanical calculations. The structural calculations are benchmarked against published calculations of enthalpy of formation and rotational constants, and published experimental data. The good agreement obtained confirms the accuracy of the results. A single rotamer of each isomer was then selected and the C 1s photoelectron spectra calculated and compared with experiment. Good agreement is obtained, and the calculations were extended to investigate the effects of conformation. For 3-methoxyphenol, the difference in the C 1s binding energy of the conformers is small, <0.15 eV. For 2-methoxyphenol, whose ground state includes an OH⋯OCH3 hydrogen bond, the higher energy rotamers show the largest shifts for the methyl carbon atom, whereas the ring carbon bonded to OH hardly shifts The theoretical differences in core level energies of the two rotamers of 4-MP are still smaller, <0.05 eV. By comparing calculations neglecting or including final state relaxation upon ionization, the relaxation energy of the phenyl carbons in all isomers is found to be ∼0.5 eV, while that of the methyl groups is ∼1.3 eV.

Chloroform ingestion causing severe gastrointestinal injury, hepatotoxicity and dermatitis confirmed with plasma chloroform concentrations.

CONTEXT: Poisoning due to chloroform ingestion is rare. The classic features of acute chloroform toxicity include central nervous system (CNS) and respiratory depression, and delayed hepatotoxicity. CASE DETAILS: A 30-year-old female ingested 20-30 mL of 99% chloroform solution, which caused rapid loss of consciousness, transient hypotension and severe respiratory depression requiring endotracheal intubation and ventilation. She was alert by 12 h and extubated 16 h post-overdose. At 38-h post-ingestion, her liver function tests started to rise and she was commenced on intravenous acetylcysteine. Her alanine transaminase (1283 U/L), aspartate transaminase (734 U/L) and international normalized ratio (2.3) peaked 67- to 72-h post-ingestion. She also developed severe abdominal pain, vomiting and diarrhoea. An abdominal CT scan was consistent with severe enterocolitis, and an upper gastrointestinal endoscopy showed erosive oesophagitis, severe erosive gastritis and ulceration. She was treated with opioid analgesia, proton pump inhibitors, sucralfate and total parenteral nutrition. Secretions caused a contact dermatitis of her face and back. Nine days post-ingestion she was able to tolerate food. Her liver function tests normalized and the dermatitis resolved. Chloroform was measured using headspace gas chromatograph mass spectrometry, with a peak concentration of 2.00 µg/mL, 4 h 20 min post-ingestion. The concentration-time data fitted a 1-compartment model with elimination half-life 6.5 h. DISCUSSION: In addition to early CNS depression and delayed hepatotoxicity, we report severe gastrointestinal injury and dermatitis with chloroform ingestion. Recovery occurred with good supportive care, acetylcysteine and management of gastrointestinal complications.

Reinterpretation of Dynamic Vibrational Spectroscopy to Determine the Molecular Structure and Dynamics of Ferrocene.

Molecular distortion of dynamic molecules gives a clear signature in the vibrational spectra, which can be modeled to give estimates of the energy barrier and the sensitivity of the frequencies of the vibrational modes to the reaction coordinate. The reaction coordinate method (RCM) utilizes ab initio-calculated spectra of the molecule in its ground and transition states together with their relative energies to predict the temperature dependence of the vibrational spectra. DFT-calculated spectra of the eclipsed (D5h ) and staggered (D5d ) forms of ferrocene (Fc), and its deuterated analogue, within RCM explain the IR spectra of Fc in gas (350 K), solution (300 K), solid solution (7-300 K), and solid (7-300 K) states. In each case the D5h rotamer is lowest in energy but with the barrier to interconversion between rotamers higher for solution-phase samples (ca. 6 kJ mol-1 ) than for the gas-phase species (1-3 kJ mol-1 ). The generality of the approach is demonstrated with application to tricarbonyl(η4 -norbornadiene)iron(0), Fe(NBD)(CO)3 . The temperature-dependent coalescence of the ν(CO) bands of Fe(NBD)(CO)3 is well explained by the RCM without recourse to NMR-like rapid exchange. The RCM establishes a clear link between the calculated ground and transition states of dynamic molecules and the temperature-dependence of their vibrational spectra.

Ferrocene Orientation Determined Intramolecular Interactions Using Energy Decomposition Analysis.

Two very different quantum mechanically based energy decomposition analyses (EDA) schemes are employed to study the dominant energy differences between the eclipsed and staggered ferrocene conformers. One is the extended transition state (ETS) based on the Amsterdam Density Functional (ADF) package and the other is natural EDA (NEDA) based in the General Atomic and Molecular Electronic Structure System (GAMESS) package. It reveals that in addition to the model (theory and basis set), the fragmentation channels more significantly affect the interaction energy terms (ΔE) between the conformers. It is discovered that such an interaction energy can be absorbed into the pre-partitioned fragment channels so that to affect the interaction energies in a particular conformer of Fc. To avoid this, the present study employs a complete fragment channel-the fragments of ferrocene are individual neutral atoms. It therefore discovers that the major difference between the ferrocene conformers is due to the quantum mechanical Pauli repulsive energy and orbital attractive energy, leading to the eclipsed ferrocene the energy preferred structure. The NEDA scheme further indicates that the sum of attractive (negative) polarization (POL) and charge transfer (CL) energies prefers the eclipsed ferrocene. The repulsive (positive) deformation (DEF) energy, which is dominated by the cyclopentadienyle (Cp) rings, prefers the staggered ferrocene. Again, the cancellation results in a small energy residue in favour of the eclipsed ferrocene, in agreement with the ETS scheme. Further Natural Bond Orbital (NBO) analysis indicates that all NBO energies, total Lewis (no Fe) and lone pair (LP) deletion all prefer the eclipsed Fc conformer. The most significant energy preferring the eclipsed ferrocene without cancellation is the interactions between the donor lone pairs (LP) of the Fe atom and the acceptor antibond (BD*) NBOs of all C-C and C-H bonds in the ligand, LP(Fe)-BD*(C-C & C-H), which strongly stabilizes the eclipsed (D5h) conformation by -457.6 kcal·mol-1.

A comparative study of the antioxidant, antimicrobial, cytotoxic and thrombolytic potential of the fruits and leaves of Spondias dulcis.

OBJECTIVE: To investigate the antioxidant, antimicrobial, cytotoxic and thrombolytic property of the fruits and leaves of Spondias dulcis (S. dulcis). METHODS: Methanolic extracts of fruits and leaves of S. dulcis were partitioned with chloroform and dichloromethane. The antioxidant potential of the crude extract and partitioned fractions were evaluated in terms of total phenolic content, total flavonoid content, DPPH radical scavenging potential, reducing potential and total antioxidant capacity by specific standard procedures. The antimicrobial activity was evaluated using disc diffusion method. The cytotoxicity was evaluated by using brine shrimp lethality bioassay and compared with vincristine sulfate. The thrombolytic activity was compared with streptokinase. RESULTS: The methanolic fruit extract exhibited the highest phenolic content, flavonoid content and antioxidant capacity, among the other extracts, with the highest DPPH radical scavenging activity at a concentration of 10 µg/mL (IC50: 1.91 µg/mL) and maximum reducing power at a concentration of 100 µg/mL (EC50: 3.58 µg/mL). Though all extract showed moderate antimicrobial activity against the bacterial strains, weak or no activity against fungus. The range of LC50 value of all extracts was 1.335-14.057 µg/mL which was far lower than the cut off index for cytotoxicity. All extracts exhibited statistically significant (P<0.001) thrombolytic activity. CONCLUSIONS: Our study suggested that S. dulcis exhibits antimicrobial activities against a wide variety of strains while it possesses significant antioxidant, cytotoxic and thrombolytic activity.