AFM, SPM
L. G. Fedenok
M.S. Shvartsberg fedenok@kinetics.nsc.ru
Oxidative dehydrodimerization (oxidative coupling) of terminal acetylenes is an important modern method for preparing highly unsaturated dimeric, polymeric, and macrocyclic structures.1
R R
(or Cu(I) + OCu(II) 2) R + Cu(I) + H+ (or H2O)
The detailed study of the oxidative coupling kinetics of a series of various acetylenes in a buffer solution (amine, НОАс in pyridine) shows the reaction to be second orders with respect to reagents, zero order with respect to Cu(I), and inverse second order with respect to acetic acid.2,3 It has been established that the reactivity of acetylenes increases with increasing their acidity. From the data obtained the reaction mechanism is proposed whose final stage involves synchronous oxidation of two acetylide anions with the simultaneous formation of the C-C bond. Propynol oxidation under the same conditions obeys quite different kinetic rules.4,5 Thus, e.g., for the [Сu(I)]/[Сu(II)] ≥ 5, the reaction has zero order with respect to Сu(II) and the first one respect with to Сu(I). In addition, we have revealed the surprising thing that the reaction rate increases with increasing [HOAc] at constant [OAc−].5 This fact served a basis for interpreting the ‘anomalous’ kinetics of the oxidative coupling of propynol. We assume that the presence of hydroxyl group in a molecule results in two consequences. On the one hand, the dissociation of its proton decreases the ethynyl hydrogen mobility, but the acid, present in solution, shifts dissociation equilibrium to the left. On the other hand, the sterically free hydroxyl group participates in the complexation with copper ions to facilitate the dimer complex formation on the final stage of the synchronous transfer of electrons. The scheme proposed is in fair agreement with experimental data.5
References:
[1] Siemsen, P.; Livingston, R.C.; Diederich, F. Angew. Chem. Int. Ed. 2000, 39, 2632-2657.
[2] Fedenok, L.G.; Berdnikov, V.M.; Shvartsberg, M.S. J. Org. Chem. USSR. 1973, 9, 1806-1809.
[3] Fedenok, L.G.; Berdnikov, V.M.; Shvartsberg, M.S. J. Org. Chem. USSR. 1974, 10, 934-936.
[4] Clifford, A.A.; Waters, W.A. J. Chem. Soc. 1963, 3056-3062.
[5] Fedenok, L.G.; Berdnikov, V.M.; Shvartsberg, M.S. J. Org. Chem. USSR. 1978, 14, 1334-1337.
[6] Fedenok, L.G.; Shvartsberg M.S. Tetrahedron Lett. 2003, doi: 52, 10.1016/j.tetlet.2011.05.065.
1. Theoretical Organic Chemistry: Poster presentation P-2 RAMAN SPECTROSCOPY OF PHOSPHORUS-
CONTAINING DENDRIMERS BUILT FROM THIOPHOSPHORYL CORE
1 - Kazan State Architect and Civil Engineering University, Kazan, Russia
2 - Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of RAS, Kazan, Russia
3 - Laboratoire de Chimie de Coordination, CNRS, France V.L. Furer1
A.E. Vandyukov2 J.-P. Majoral3 A.M. Caminade3
V.I. Kovalenko2 furer@ksaba.ru
Dendrimers are a new type of compounds and the perspective materials studied by supramolecular chemistry. Heteroatom-containing dendrimers, and particularly phosphorus- containing dendrimers, have their own specificity and properties.
In this work we show the value of FT Raman spectroscopy for characterization of dendrimers. Our aim was to study the connection between the peculiarities of the structure of these compounds and their vibrational spectra.
The Raman spectra of ten generations of phosphorus-containing dendrimers containing P=S and P=O bonds with terminal benzaldehyde and P−Cl groups have been recorded and analyzed. The Raman spectra of dendrimers are determined by the ratio Tn/Rn
(Tn – number of terminal groups, Rn – number of repeating units). This ratio trends to r – 1 (r – branching functionality of repeating unit), and becomes constant, when the generation number is higher than 3. The dependence of line full width at half height in Raman spectra on generation number is established.
The lines assigned to the core, repeating units and terminal groups of dendrimers were defined by difference spectroscopy. The influence of the encirclement on the line frequencies and intensities was studied and due to the predictable, controlled and reproducible structure of dendrimers the information, usually inaccessible is obtained. Some lines in the Raman difference spectra have characteristic EPR-like form. The strong line at 1600 cm-1 show marked changes of intensity in dependence of aldehyde (−CH=O) or azomethyne (−CH=N) substituents in the aromatic ring. Raman spectroscopy provides unique detailed information concerning the structure of relevant materials, which could not be obtained with any other technique.
1. Theoretical Organic Chemistry: Poster presentation P-3 FTIR AND FT RAMAN SPECTROSCOPY OF PHOSPHORUS-CONTAINING FLUORESCENT
DENDRIMERS BUILT FROM CYCLOTRIPHOSPHAZENE CORE
1 - Kazan State Architecture and Civil Engineering University, Kazan, Russia
2 - CNRS, Laboratoire de Chimie de Coordination, CNRS, Toulouse, France
3 - Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center of RAS, Kazan, Russia
V.L. Furer1 S. Fuchs2 J.-P. Majoral2 A.-M. Caminade2 A.E. Vandyukov3
V.I. Kovalenko3 furer@ksaba.ru
Due to the numerous potential applications in the fields of catalysis, materials, biology and medicine, dendrimers constitute an important class of tree-like compounds. In this work FTIR and FT-Raman spectroscopy were used for characterization of the surface- block (called “Janus”) dendrimers that built from the hexafunctional cyclotriphosphazene core, obtained by the coupling of two dendrons, one having five dansyl functions and other with five carbamate ones, linked by amide or hydrazone bridge. Some model of dendrons, built from the cyclotriphosphazene core were also studied. We choose dansyl group as the fluorescent label for dendrimers. The presence of carbamate groups is important since they offer a wide range of possibilities to obtain hydrophilic functions onto the surface of dendrimers.
The characteristic feature of the IR and Raman spectra of the studied dendrimers and dendrons is their similarity to each other. The structural optimization and normal mode analysis were performed for dendrons on the basis of the density functional theory. The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that the dendron molecule has a concave lens structure with planar –O-C6H4-CH=O fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of dendron were interpreted by means of potential energy distribution. Relying on DFT calculations a complete vibrational assignment is proposed. The strong band 1597 cm-1 show marked changes of the optical density in dependence of substituents in the aromatic ring. The frequencies of ν(N-H) bands in the IR spectra reveal the presence of the different types of H-bonds in dendrimers. FTIR and FT-Raman spectroscopy provide unique detailed information concerning the structure of relevant materials, which could not be obtained with any other technique.
1. Theoretical Organic Chemistry: Poster presentation P-4 STRUCTURE OF OXIMES OF 1-METHYL-4- METHOXY-2-ETHANOYL- AND 1,4-DIMETHOXY- ETHANOYL- AND PROPANOYLBENZENE BY 1H AND 13C NMR SPECTRA AND X-RAY ANALYSIS 1 - Baku State University, Baku, Azerbaijan
2 - Moscow Chemical-Technology University, Moscow, Russia V.M. Ismaylov1
I.A. Mamedov1 S.S. Nasibov1 N.N. Yusubov1
V.V. Moskva2 niftali-yusubov@rambler.ru
The establishing of configuration of ketoximes is a difficult task. The most promising is the establishment of the configuration ketoximes and their derivatives by the 1H and 13C NMR spectra.
In order to reveal the universality of this method for decision of the structural features of ketoximes we synthesized oximes of 4-metoxy-2-etanoylphenol, 1,4-methoxy-2- ethanoylbenzene, 1,4-dimethoxy-2-propanoylbenzene and determined their configuration by using 13C NMR and X-ray analysis. It is important to note that the synthesis of these oximes by 1H, 13C NMR and X-ray analysis produced only one isomer.
From the literature data follows that in ketoximes signal of α-methyl group, which has syn-orientation to the OH group, always reveals itself in more strong field than the signal of CH3 group in anti-positions and is manifested in the 10-14 ppm, whereas in the spectra of Z-isomers of methylketoximes the signal of CH3 group is in the range of 15-21 ppm.
In the 13C NMR spectra of synthesized ketoximes the signal of the CH3 group is manifested in the 18-19 ppm.
According to literature data the indicated ketoximes should be attributed to the structure of Z-isomer. However, these X-ray analysis unambiguously give the structure of the E-isomer.
Thus, on the basis of chemical shift of the carbon atom of the methyl group not always can be uniquely define the configuration of ketoximes because on the value of this chemical shift significantly affected the neighboring atoms or groups, in particular the methyl group in ortho-position of aromatic nucleus.
1. Theoretical Organic Chemistry: Poster presentation P-5 N,N-ANNULATED DIAZAPHOSPHOLE: NEW
AROMATIC SYSTEM. STRUCTURE AND REACTIVITY
G.A. Razuvaev Institute of Organometallic Chemistry RAS, Nizhny Novgorod, Russia
O.V. Lukoyanova O.Ya. Gorak Yu.S. Panova
V.V. Sushev A.N. Kornev
G.A. Abakumov olga.novikova@iomc.ras.ru
Heterophospholes are five-membered 6e aromatic systems having a two-coordinate, tervalent (σ2, λ3) phosphorus which contributes one electron to the aromatic sextet.
Unique tetracyclic bis-diazaphosphole have been obtained by the reduction of the corresponding dichloroderivation.
The heterocyclic system, containing annulated five-membered rings, is entirely planar. Such arrangement enhances the effective overlap of the molecular orbitals along the fragments P-C-C-N to form a conjugated 10e-system of an essentially new type. These facts let us discuss aromaticity of the molecule. The Nuclear Independent Chemical Shift (NICS) values computed at and above the five-membered ring centers are negative.
The P-N bond lengths (1.733 Å) are in the range typical for the phosphazanes; while the N-N distance of 1.368 Å is rather shorter than that usually known for hydrazines.
Geometry of the molecule was optimized at the B3LYP/6-31G(d) level. The three highest occupied orbitals are mainly localized on the annulated heterocycles.
NBO analysis of optimized structure shows significant charge separation in the five- membered cycles: the N atoms bear partially negative charges (-0.394) while the P atoms are positively charged (+0.592); the carbon atoms, bonded to nitrogen and phosphorus, have partial charges of +0.141 and +0.422, respectively.
This work was supported by The Russian President’s program “Leading Scientific Schools”
(No. 7065.2010.3) and RFBR regional grant No 11-03-97029.
1. Theoretical Organic Chemistry: Poster presentation P-6 QM/MM MODELING OF THE G117H
BUTYRYLCHOLINESTERASE CATALYZED ECHOTHIOPHATE HYDROLYSIS REACTION
MECHANISM
1 - N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia
2 - Institut de Recherche Biomedicale des Armees–CRSSA, La Tronche, France
3 - M.V. Lomonosov Moscow State University, Department of Chemistry, Moscow, Russia
S.V. Lushchekina1 P. Masson2 F. Nachon2 A.V. Nemukhin3
S.D. Varfolomeev1 sofya.lushchekina@gmail.com
Butyrylcholinesterase (BuChE) serves as a stoichiometric bioscavenger of organophosphorus (OP) compounds, forming a covalent bond with them. Creation of BuChE mutants capable of catalyzing the hydrolysis of OP compounds will convert the enzyme into effective catalytic bioscavenger. The G117H mutant of BuChE hydrolyzes OP compounds at slow rates. Understanding of the hydrolytic mechanism should help to improve the OPase activity of ChE-based catalytic bioscavengers. The crystallographic structure of the G117H mutant of BuChE conjugated to echotiophate was published recently [1].
We performed molecular dynamics and QM/MM studies of the G117H BuChE mutant conjugated to echotiophate in order to consider different hydrolysis mechanisms.
The possible changes in His117 orientation depending on protonation state and it influence on average enzyme dynamics were considered. The hydrolysis reaction energy profiles for different possible hydrolysis mechanisms were obtained and compared with the respective profiles for aging process. The His117 protonation lowers reaction energy barriers and stabilizes reaction products both for the hydrolysis and aging processes comparing to the wilde-type BuChE.
References:
[1] 1. Nachon, F. et al., X-ray crystallographic snapshots of reaction intermediates in the G117H mutant of human butyrylcholinesterase, a nerve agent target engineered into a catalytic bioscavenger. Biochemical Journal, 2011, *434*(1): p. 73-82.
1. Theoretical Organic Chemistry: Poster presentation P-7 EFFICIENT METHOD OF THE SYNTHESIS OF
N-SUBSTITUTED TETRAHYDROINDOLE