A combined spectroscopic and theoretical study of propofol center dot (h2o)(3)

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Molecular Hydration of Propofol Dimer in Supersonic Expansions: Formation of Active Centre-Like Structures

Spectroscopic studies of molecular aggregates are a powerful tool to understand the weak interactions between molecules. Here, Propofol2(H2O)6,7 clusters were formed in supersonic expansions and its electronic and infrared spectroscopy was explored using several mass-resolved laser-based spectroscopic techniques. Using REMPI, their S1<-- S0 electronic spectrum was obtained with vibrational resolution, while the UV/UV hole burning revealed the presence of a single isomer of propofol2(H2O)6 and of two isomers of propofol2(H2O)7. Employment of IR/UV double resonance yielded the IR spectrum in the OH stretch region. Comparison with the spectra predicted for the structures calculated at the M06-2X/6-31+G(d) level demonstrated that the two propofol molecules interact mainly through C-H contacts between the lipophilic sides of the molecules, while the hydroxyl moieties are in close contact, forming a kind of "active centre" with which the water molecules interact, forming polyhedral structure

Formation of water polyhedrons in propofol-water clusters

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O-Hdot operatordot operatordot operatorN and C-Hdot operatordot operatordot operatorO hydrogen bonds control hydration of pivotal tropane alkaloids: tropinonedot operatordot operatordot operatorH(2)O complex

The effect of monohydration in equatorial/axial isomerism of the common motif of tropane alkaloids is investigated in a supersonic expansion by using Fourier-transform microwave spectroscopy. The rotational spectrum reveals the equatorial isomer as the dominant species in the tropinone c5 c5 c5H2 O complex. The monohydrated complex is stabilized primarily by a moderate O\uf8ffH c5 c5 c5N hydrogen bond. In addition, two C\uf8ffH c5 c5 c5O weak hydrogen bonds also support this structure, blocking the water molecule and avoiding any molecular dynamics in the complex. The water molecule acts as proton donor and chooses the ternary amine group over the carbonyl group as a proton acceptor. The experimental work is supported by theoretical calculations; the accuracy of the B3LYP, M06-2X, and MP2 methods is also discussed

Competition between weak hydrogen bonds: C-H⋯Cl is preferred to C-H⋯F in CH2ClF-H2CO, as revealed by rotational spectroscopy

We recorded the pulsed jet Fourier transform microwave spectrum of the 1 : 1 adduct of CH2ClF with formaldehyde. Formaldehyde is linked to CH2ClF through a C-H···Cl bond rather than a weak C-H···F hydrogen bond, with a H···Cl "bond length" of 2.918 Å. Two additional equivalent C-H···O contacts, with a H···O distance of 2.821 Å, characterize the complex. Tunnelling splittings due to the internal rotation of the formaldehyde moiety have been observed, which allowed estimating the barrier to the internal rotation of formaldehyde to be 125(10) cm(-1). The (35)Cl quadrupole coupling constants have been determined to be χaa = 31.131(7) MHz and χbb-χcc = -105.82(1) MHz

Exploring microsolvation of the anesthetic propofol

Propofol (2,6-diisopropylphenol) is a broadly used general anesthetic. By combining spectroscopic techniques such as 1- and 2-color REMPI, UV/UV hole burning, infrared ion-dip spectroscopy (IRIDS) obtained under cooled and isolated conditions with high-level ab initio calculations, detailed information on the molecular structure of propofol and on its interactions with water can be obtained. Four isomers are found for the bare propofol, while only three are detected for the monohydrated species and two for propofol center dot(H2O)(2). The isopropyl groups do not completely block the OH solvation site, but reduce considerably the strength of the hydrogen bonds between propofol and water. Such results may explain the high mobility of propofol in the GABA(A) active site, where it cannot form a strong hydrogen bond with the tyrosine residue

Exploring microsolvation of the anesthetic propofol

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A combined spectroscopic and theoretical study of propofol center dot (H2O)(3)

Propofol (2,6-di-isopropylphenol) is probably the most widely used general anesthetic. Previous studies focused on its complexes containing 1 and 2 water molecules. In this work, propofol clusters containing three water molecules were formed using supersonic expansions and probed by means of a number of mass-resolved laser spectroscopic techniques. The 2-color REMPI spectrum of propofol center dot (H2O)(3) contains contributions from at least two conformational isomers, as demonstrated by UV/UV hole burning. Using the infrared IR/UV double resonance technique, the IR spectrum of each isomer was obtained both in ground and first excited electronic states and interpreted in the light of density functional theory (DFT) calculations at M06-2X/6-311++G(d,p) and B3LYP/6-311++G(d,p) levels. The spectral analysis reveals that in both isomers the water molecules are forming cyclic hydrogen bond networks around propofol&#039;s OH moiety. Furthermore, some evidences point to the existence of isomerization processes, due to a complicated conformational landscape and the existence of multiple paths with low energy barriers connecting the different conformers. Such processes are discussed with the aid of DFT calculations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4743960

Internal dynamics in halogen-bonded adducts: A rotational study of chlorotrifluoromethane-formaldehyde

The rotational spectra of two isotopologues of the 1:1 complex between chlorotrifluoromethane and formaldehyde have been recorded and analyzed by using Fourier-transform microwave spectroscopy. Only one rotamer was detected, with the two constituent molecules held together through a Cl c5 c5 c5O halogen bond (R(Cl c5 c5 c5O) = 3.048\u2005\uc5). The dimer displays two simultaneous large-amplitude intramolecular motions. The internal rotation of formaldehyde around its symmetry axis (V2 = 28(5)\u2005cm(-1)) splits all the rotational transitions into two component lines with a relative intensity ratio of 1:3. On the other hand, the almost free internal rotation (V3 48 2.5\u2005cm(-1)) of the CF3 symmetric top increases the "rigid" value of the rotational constant A by almost one order of magnitude. In addition, all the transitions display a hyperfine structure due to the (35)Cl (or (37)Cl) nucleus quadrupole effects