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Dr. Barbara M. Giuliano Dr. Laura B. Favero Dr. Assimo Maris Prof. Dr. Walther Caminati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(40):12759-12763
Two 1:1 adducts of ammonia with ethanol have been characterized by using pulsed‐jet FT microwave spectroscopy. They are formed with two different (trans and gauche), stable conformers of ethanol. Several internal‐dynamics effects are reflected in the features of the rotational spectra. The trans complex shows the tunneling effects owing to internal rotation of both ammonia and the methyl group. The rotational transitions of the gauche species exhibit a small splitting that is related to tunneling through the potential‐energy barrier between the two equivalent minima. 相似文献
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Frontiers in Rotational Spectroscopy: Shapes and Tunneling Dynamics of the Four Conformers of the Acrylic Acid—Difluoroacetic Acid Adduct 下载免费PDF全文
Dr. Gang Feng Qian Gou Dr. Luca Evangelisti Prof. Dr. Walther Caminati 《Angewandte Chemie (International ed. in English)》2014,53(2):530-534
The rotational spectra of four conformers of the acrylic acid—difluoroacetic acid adduct (CH2=CHCOOH–CHF2COOH, AA‐DFA) are reported and information on their internal dynamics is supplied. This represents an unprecedented result for the conformational analysis, with microwave spectroscopy, of such a heavy molecular adduct. 相似文献
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Conformational Equilibria and Large‐Amplitude Motions in Dimers of Carboxylic Acids: Rotational Spectrum of Acetic Acid–Difluoroacetic Acid 下载免费PDF全文
Qian Gou Dr. Gang Feng Dr. Luca Evangelisti Prof. Walther Caminati 《Chemphyschem》2014,15(14):2977-2984
We report the rotational spectra of two conformers of the acetic acid–difluoroacetic acid adduct (CH3COOH–CHF2COOH) and supply information on its internal dynamics. The two conformers differ from each other, depending on the trans or gauche orientation of the terminal ?CHF2 group. Both conformers display splittings of the rotational transitions, due to the internal rotation of the methyl group of acetic acid. The corresponding barriers are determined to be V3(trans)=99.8(3) and V3(gauche)=90.5(9) cm?1 (where V3 is the methyl rotation barrier height). The gauche form displays a further doubling of the rotational transitions, due to the tunneling motion of the ?CHF2 group between its two equivalent conformations. The corresponding B2 barrier is estimated to be 108(2) cm?1. The increase in the distance between the two monomers upon OH→OD deuteration (the Ubbelohde effect) is determined. 相似文献
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How Water Interacts with Halogenated Anesthetics: The Rotational Spectrum of Isoflurane–Water 下载免费PDF全文
Qian Gou Dr. Gang Feng Dr. Luca Evangelisti Montserrat Vallejo‐López Lorenzo Spada Prof. Dr. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Dr. Walther Caminati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(7):1980-1984
The rotational spectra of several isotopologues of the 1:1 complex between the inhaled anesthetic isoflurane and water have been recorded and analyzed by using Fourier transform microwave spectroscopy. The rotational spectrum showed a single rotamer, corresponding to the configuration in which the most stable conformer of isolated isoflurane is linked to the water molecule through an almost linear C?H???O weak hydrogen bond. All transitions display a hyperfine structure due to the 35Cl (or 37Cl) nuclear quadrupole effects. 相似文献
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Giovanna Salvitti Filippo Baroncelli Chiara Nicotri Luca Evangelisti Sonia Melandri Assimo Maris 《Molecules (Basel, Switzerland)》2022,27(23)
The rotational spectrum of the 1:1 N,N-diethylhydroxylamine-water complex has been investigated using pulsed jet Fourier transform microwave spectroscopy in the 6.5–18.5 GHz frequency region. The most stable conformer has been detected as well as the C monosubstituted isotopologues in natural abundance and the O enriched water species, allowing to determine the nitrogen nuclear quadrupole coupling constants and the molecular structure in the vibrational ground state. The molecule has a symmetry and the water lies in the symmetry plane forming two hydrogen bonds with the NOH frame with length: = 1.974 Å and = 2.096 Å. From symmetry-adapted perturbation theory calculations coupled to atoms in molecule approach, the corresponding interaction energy values are estimated to be 24 and 13 kJ·mol, respectively. The great strength of the intermolecular interaction involving the nitrogen atom is in agreement with the high reactivity of hydroxylamine compounds at the nitrogen site. 相似文献
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We report the observation and analysis of the rotational spectrum of a 1:1 cluster between 2-aminopyridine and water (AMW) carried out with supersonic expansion Fourier transform microwave spectroscopy at 4.7–16.5 GHz. Measurements of the 2-aminopyridine monomer (AMP) were also extended up to 333 GHz for the room-temperature rotational spectrum and to resolved hyperfine splitting resulting from the presence of two 14N quadrupolar nuclei. Supersonic expansion measurements for both AMP and AMW were also carried out for two synthesized isotopic species with single deuteration on the phenyl ring. Nuclear quadrupole hyperfine structure has also been resolved for AMW and the derived splitting constants were used as an aid in structural analysis. The structure of the AMW cluster was determined from the three sets of available rotational constants and the hydrogen bonding configuration is compared with those for clusters with water of similarly sized single-ring molecules. Experimental results aided by quantum chemistry computations allow the conclusion that the water molecule is unusually strongly bound by two hydrogen bonds, OH...N and O...HN, to the NCNH atomic chain of AMP with the potential to replace hydrogen bonds to the identical structural segment in cytosine and adenine in CT and AT nucleic acid base pairs. 相似文献
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Internal Dynamics in Halogen‐Bonded Adducts: A Rotational Study of Chlorotrifluoromethane–Formaldehyde 下载免费PDF全文
Dr. Qian Gou Dr. Gang Feng Dr. Luca Evangelisti Dr. Montserrat Vallejo‐López Lorenzo Spada Prof. Dr. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Dr. Walther Caminati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(10):4148-4152
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???O halogen bond (RCl???O=3.048 Å). The dimer displays two simultaneous large‐amplitude intramolecular motions. The internal rotation of formaldehyde around its symmetry axis (V2=28(5) cm?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≈2.5 cm?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 35Cl (or 37Cl) nucleus quadrupole effects. 相似文献
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Probing the CH⋅⋅⋅π Weak Hydrogen Bond in Anesthetic Binding: The Sevoflurane–Benzene Cluster 下载免费PDF全文
Nathan A. Seifert Dr. Daniel P. Zaleski Dr. Cristóbal Pérez Dr. Justin L. Neill Prof. Brooks H. Pate Montserrat Vallejo‐López Prof. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Fernando Castaño Prof. Isabelle Kleiner 《Angewandte Chemie (International ed. in English)》2014,53(12):3210-3213
Cooperativity between weak hydrogen bonds can be revealed in molecular clusters isolated in the gas phase. Here we examine the structure, internal dynamics, and origin of the weak intermolecular forces between sevoflurane and a benzene molecule, using multi‐isotopic broadband rotational spectra. This heterodimer is held together by a primary C? H???π hydrogen bond, assisted by multiple weak C? H???F interactions. The multiple nonbonding forces hinder the internal rotation of benzene around the isopropyl C? H bond in sevoflurane, producing detectable quantum tunneling effects in the rotational spectrum. 相似文献
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Atomistic molecular dynamics simulations were performed under ambient conditions to explore the conformational features and binding affinities of hexameric glycosaminoglycans (GAGs) with chemokine Interleukin8 (IL8) in an aqueous medium. We tried to understand the role of hydrogen bonds (HBs) involving conserved water in mediating the interactions. The Luzar-Chandler model was adopted to study the kinetics of HB breaking and formation concerning different water-mediated HBs. The conformational flexibilities of bound GAGs are due to the flexible glycosidic linkages than the occasional/rare ring pucker conformation. The free energy landscape constructed with ϕ, and ψ, depicted that different conformational minima associated with the glycosidic linkage flexibility of the GAGs in bound states are separated by energy barriers. The binding affinities of IL8 towards GAGs are favored through the electrostatic and non-polar solvation interactions. 4-different types of conserved water were explored in the solvent-mediated binding of GAGs with IL8. The average lifetime of the IL8-GAG direct HB pairs was ∼ten times less than the IL8-GAG-shared water HBs. This is due to the rapid establishment of HB breaking and reformation kinetics involving water of a shared layer. We find that despite the highly negatively charged surface of GAGs, the IL8 surface populated by non-cationic amino acids could serve as a promising binding site in addition to the cationic surface of the protein. 相似文献
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The Cage Structure of IndanCHF3 is Based on the Cooperative Effects of CH⋅⋅⋅π and CH⋅⋅⋅F Weak Hydrogen Bonds 下载免费PDF全文
Dr. Laura B. Favero Weixing Li Lorenzo Spada Dr. Luca Evangelisti Giorgio Visentin Prof. Dr. Walther Caminati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):15970-15973
The structural and energetic features of the C?H???π interaction and the internal dynamics of the CHF3 group change drastically in going from benzene?CHF3 to indan?CHF3, according to the analysis of the rotational spectrum of the latter complex generated in a supersonic expansion. 相似文献
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The title compound [Cd(Hq)2(Hdpa)2] (Hq = 8-hydroxyquinoline, H2dpa = diphenic acid) has been synthesized and characterized by single-crystal X-ray diffraction analysis. It crystallizes in monoclinic, space group C2/c with a = 20.6880(5), b = 14.2584(4), c = 13.4776(4) (A), β = 113.434(2)°, C46H28Cd1N2O10, Mr = 881.10, V = 3647.68(17) (A)3, Z = 4, Dc = 1.604 g/cm3, F(000) = 1784,μ = 0.668 mm-1, the final R = 0.0576 and wR = 0.1157 for 2631 observed reflections with I >2σ(Ⅰ). The centrosymmetric Cd(Ⅱ) ion is six-coordinated in a slightly distorted octahedral geometry.The intermolecular hydrogen bonds extend the mononuclear structure into a one-dimensional supramolecular framework. The fluorescence spectrum of the compound exhibits intense emission at 520 nm when excited at 330 nm in solid state at room temperature. 相似文献
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1 INTRODUCTION The rational design and synthesis of new metal- organic coordination polymers have generated con- siderable interest in supramolecular chemistry and material science owing to their intriguing structural diversities and potential applications as functional materials[1~3]. Molecular self-assembly has been pro- ved to be an efficient way to construct various inte- resting coordination polymers[4~6]. The coordina- tion covalent bond, hydrogen bond or other mole- cular interact… 相似文献
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Xunchen Liu Nicole Borho Dr. Yunjie Xu Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(1):270-277
Fluoroalcohols show competitive formation of intra‐ and intermolecular hydrogen bonds, a property that may be crucial for the protein‐altering process in a fluoroalcohol/water solution. In this study, we examine the intra‐ and intermolecular interactions of 2‐fluoroethanol (FE) in its dimeric conformers by using rotational spectroscopy and ab initio calculations. Three pairs of homo‐ and heterochiral dimeric FE conformers are predicted to be local minima at the MP2/6‐311++G(d,p) level of theory. They are solely made of the slightly distorted most stable G+g?/G?g+ FE monomer units. Jet‐cooled rotational spectra of four out of the six predicted dimeric conformers were observed and unambiguously assigned for the first time. All four observed dimeric conformers have compact geometries in which the fluoromethyl group of the acceptor tilts towards the donor and ensures a large contact area. Experimentally, the insertion of the O? H group of one FE subunit into the intramolecular O? H???F bond of the other was found to lead to a higher stabilisation than the pure association through an intermolecular O? H???O? H link. The hetero‐ and homochiral combinations were observed to be preferred in the inserted and the associated dimeric conformers, respectively. The experimental rotational constants and the stability ordering are compared with the ab initio calculations at the MP2 level with the 6‐311++G(d,p) and aug‐cc‐pVTZ basis sets. The effects of fluorination and the competing inter‐ and intramolecular hydrogen bonds on the stability of the dimeric FE conformers are discussed. 相似文献
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Dr. Amit Delori Dr. Peter T. A. Galek Dr. Elna Pidcock Prof. William Jones 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(22):6835-6846
An investigation into the predictability of molecular adduct formation is presented by using the approach of hydrogen bond propensity. Along with the predictions, crystallisation reactions ( 1a – 1j ) were carried out between the anti‐malarial drug pyrimethamine ( 1 ) and the acids oxalic ( a ), malonic ( b ), acetylenedicarboxylic ( c ), adipic ( d ), pimelic ( e ), suberic ( f ), azelaic acids ( g ), as well as hexachlorobenzene ( h ), 1,4‐diiodobenzene ( i ), and 1,4‐diiodotetrafluorobenzene ( j ); seven ( 1a to 1g ) of these successfully formed salts. Five of these seven salts were found to be either hydrated or solvated. Hydrogen bond propensity calculations predict that hydrogen bonds between 1 and acids a – g are more likely to form rather than the H bonds involved in self‐association, providing a rationale for the observation of the seven new salts. In contrast, propensity of hydrogen bonds between 1 and h – j is much smaller as compared to other bonds predicted for self‐association/solvate formation, in agreement with the observed unsuccessful reactions. 相似文献
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Analysis of Proton NMR in Hydrogen Bonds in Terms of Lone‐Pair and Bond Orbital Contributions 下载免费PDF全文
Dr. Kiplangat Sutter Prof. Gustavo A. Aucar Prof. Jochen Autschbach 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18138-18155
NMR spectroscopic parameters of the proton involved in hydrogen bonding are studied theoretically. The set of molecules includes systems with internal resonance‐assisted hydrogen bonds, internal hydrogen bonds but no resonance stabilization, the acetic acid dimer (AAD), a DNA base pair, and the hydrogen succinate anion (HSA). Ethanol and guanine represent reference molecules without hydrogen bonding. The calculations are based on zero‐point vibrationally averaged molecular structures in order to include anharmonicity effects in the NMR parameters. An analysis of the calculated NMR shielding and J‐coupling is performed in terms of “chemist’s orbitals”, that is, localized molecular orbitals (LMOs) representing lone‐pairs, atomic cores, and bonds. The LMO analysis associates some of the strong de‐shielding of the protons in resonance‐assisted hydrogen bonds with delocalization involving the π‐backbone. Resonance is also shown to be an important factor causing de‐shielding of the OH protons for AAD and HSA, but not for the DNA base pair. Nitromalonamide (NMA) and HSA have particularly strong hydrogen bonds exhibiting signs of covalency in the associated J‐couplings. The analysis results show how NMR spectroscopic parameters that are characteristic for hydrogen bonded protons are influenced by the geometry and degree of covalency of the hydrogen bond as well as intra‐ and intermolecular resonance. 相似文献