Professor Lucjan Sobczyk
Magnetic Shielding Tensors of SP-Hybridized Carbon Nuclei
Contribution of Dipolar Species to the Formation of Local States for Charge Carriers in Molecular Materials
Sworakowski J. and Nespurek S.
Hydrogen-Bonded Chains with Large Proton Polarizability due to Collective Proton Motion - Pathways for Protons in Biological Membranes
Zundel G. and Brzezinski B.
Resonance Assisted Intramolecular Hydrogen Bond in Schiff Bases
Applications of Linear and Non-Linear Polarization to Conformational Equilibria Studies
Malecki J. and Nowak J.
Structure Isotope Effect in Hydrogen-Bonded Crystals - Similarity and Difference between Deuteration and Pressure Effect
Volumetric and Dielectric Studies on 4-n-Pentyl-4'-cyanobiphenyl (5CB) under High Pressure
Urban S., Wuerflinger A., Buesing D., Brueckert T., Sandmann M. and Gestblom B.
Fixation by H-bonding of Ligands in Polymer Coils
Huyskens P., Nelis K., Vael Ch.,
Verstraeten K. and Zeegers-Huyskens Th.
Decomposition of Mg(HSeO3)2.3H2O and Mg(HSeO3)2, IR Spectroscopic and Thermoanalytical Investigations
Engelen B., Mueller H. and Unterderweide K.
Isotope Effects on Chemical Shifts in Tautomeric Systems with Double Proton Transfer.|
Hansen P.E., Langgard M. and Bolvig S.
Aqueous Basicity and Proton Affinity of Flexible Carboxybetaines, N+(CH2)nCOO-
Barczynski P., Dega-Szafran Z. and Szafran M.
FT-IR and NMR Studies of the Proton Sponge Character of cis-1,2-Bis(diethylaminomethyl)cyclohexane
Brzezinski B., Grech E., Klimkiewicz J., Schroeder G., Stefaniak L. and Urjasz H.
Raman Spectroscopy of the Hydrogen Bond in the Associates H2O.HNO3 and (HNO3)2NO3-. Evans Windows
Potier A., Potier J., Herzog M.H. and Herzog J.F.
Thin Film Transmission Spectra and Vibrational Intensities of Liquid Pyridine
Wrzeszcz W., Czarnik-Matusewicz B. and Hawranek J.P.
Infrared Studies on the Structural Phase Transitions in (n-C3H7NH3)2SbBr5(n-C3H7NH3)3Sb2Cl9
Bator G., Jakubas R. and Majerz I.
Transformation of the 3-Oxoazabicyclo[2.2.2]octane Pentachlorophenol Complex into the|
Majerz I., Malarski Z. and Lis T.
Matrix Infrared Spectra of C6H6-HNO3 and C6H6-HONO Complexes in Solid Argon
Krajewska M. and Mielke Z.
X-ray, IR and 1H NMR Studies of 1:1 Adduct of 1,8-Bis(dimethylamino)naphthalene (DMAN) and 1,1-Cyclobutanedicarboxylic Acid (CBDC)
Bartoszak-Adamska E., Grech E. and Jaskolski M.
Vibrational and DSC Investigations of the (NH4)4H2(SeO43 Crystal
Baran J., Marchewka M.K., Drozd M. and Czapla Z.
An Ab InitioCalculation of the Vibrational Spectrum of Pyridine N-Oxide and Pyridine-d5 N-Oxide
Szafran M. and Koput J.
A Study of H-Bonded (HF)n Clusters within the Framework of the Electrostatic Model
Sokolov N.D. and Savel'ev V.A.
Application of the VSCF Theory to Coupled Vibrations in Hydrogen-Bonded Systems
Piskorz P.J. and Wojcik M.J.
An Application of Group Theory to the Solution of the Rate Equation
Kozlowski M. and Kolodziej H.A.
Matrix Isolation and DFT Quantum Mechanical Studies of Vibrational Spectra of Uracil and Its Methylated Derivatives
Szczepaniak K., Person W.B., Leszczynski J. and Kwiatkowski J.S.
Quantum Chemical Studies of the Double Proton Transfer in Oxalic Acid Dimer
Phase Transformations in Locally Anharmonic Systems. Susceptibility Approach to|
Orientational Instabilities in Molecular Solids
Kuchta B. and Luty T.
CRYSTAL AND MOLECULAR STRUCTURES
The Structure of Narlumicine
Tykarska E., Chrzanowska M. and Kosturkiewicz Z.
The Crystal and Molecular Structure of Cyclic Thioamide ß-Diketone Derivatives.|
Intramolecular H-bonding and the Problem of Quasiaromaticity
Anulewicz R., Krygowski T.M. and Jagodzinski T.
Modelling Hydrogen-bonded Crystal Structures beyond Resolution of Diffraction Methods
Crystal and Molecular Structure of 2-(N,N-Diethylamino)-methyl-4-bromo-6-formylphenol
Wozniak K., Anulewicz R., Grech E. and Szady A.
Molecular Structure of Pyridine N-Oxide Complex with 2,6-Dichloro-4-nitrophenol
Tykarska E., Dega-Szafran Z., Grundwald-Wyspianska M. and Szafran M.
Spectroscopic Study of Inclusion Complexes of ß-Cyclodextrin with Sulfonamides
Szafran B. and Pawlaczyk J.
Magnetic Shielding Tensors of SP-Hybridized
by A. Gryff-Keller
(Received May 26th, 1997)
Experimental data concerning shielding tensors of the sp hybridized carbons including our own recent results have been reviewed. It appears, that the most general feature of shielding parameters for such carbons forms a linear relationship between the perpendicular chemical shift component and the isotropic chemical shift. Deviation from that interdependence informs about a distortion of the symmetry of the electron distribution around the given carbon and indirectly about various intra- or intermolecular interactions.
Contribution of Dipolar Species to the Formation of Local States for Charge Carriers in
by J. Sworakowski1 and S. Nespurek2
(Received May 28th, 1997)
Effect of polar impurities on transport of charge carriers in non-polar molecular materials is reviewed. The presence of such species gives rise to structural traps. Calculations of local values of the polarization energy in the vicinity of a dipolar defect show that traps as deep as several tenths of eV are created. If the polar impurity molecule can act as a trap itself, at high fields one may expect a dipole analogue of the Poole-Frenkel effect, the lowering of the trap depth following, however, a different dependence on the biasing electric field: EtF2/3. Moreover, the dipole-charge interactions contribute to the broadening of local transport states density in disordered materials.
Hydrogen-Bonded Chains with Large Proton
by G. Zundel1 and B. Brzezinski2
(Received April 15th, 1997; revised manuscript June 23rd, 1997)
Hydrogen-bonded chains may show very large proton polarizability due to collective proton motion if they are largely symmetrical. This result was first obtained with polylysine + dihydrogenphosphate and with polyglutamic acid + dihydrogenphosphate systems, respectively. These systems cause intense IR continua, demonstrating their large proton polarizability. This proton polarizability was studied in detail with intramolecular hydrogen-bonded systems and results of these studies are extensively discussed in this paper. Such hydrogen-bonded chains are very effective proton pathways in biology. They can easily be regulated by local electrical fields and by specific interactions. Two such pathways are discussed, the one in the L550 intermediate in the bacteriorhodopsin molecule and the pathway in the F0 subunit of the ATP synthase.
Resonance Assisted Intramolecular Hydrogen
by T. Dziembowska
(Received June 3rd, 1997; revised manuscript July 17th, 1997)
The intramolecular hydrogen bond, the proton transfer equilibrium and related properties of Schiff bases are discussed.
Applications of Linear and Non-Linear Polarization
by J. Malecki and J. Nowak
(Received June 30th, 1997; revised manuscript July 28th, 1997)
Applications of linear and non-linear dielectric effects to studies of intramolecular equilibria in liquids are described. The physical principles of the two phenomena being responsible for the magnitude of the observed effect, i.e. the Langevin effect and the chemical effect, are outlined. The later effect consists in shifting the molecular equilibria under an influence of electric field to favour the more polar products of reaction. The experimental set-up and its limitations are shortly described. Applications of Non-linear Dielectric Effect (NDE) to determine the changes in free energy, enthalpy and entropy of fast intermolecular equilibria are described and illustrated by selected examples. The significance of the solvent polarity and its dependence on temperature in enthalpy and entropy is analyzed. Two opposite approaches to calculate these quantities are presented: directly from experimental data according to the usually applied procedure and under the assumption of a constant polarity. Presented experimental results illustrate the physical meaning of these quantities and the significance of the applied approach to the interpretation of experimental results.
Structure Isotope Effect in Hydrogen-Bonded
by M. Ichikawa
(Received June 11th, 1997; revised manuscript October 31st, 1997)
The deuteration effect on the crystal structure and phase transition is briefly reviewed. Some examples of phase diagrams between deuterium content and temperature are discussed in the context of the geometric isotope effect. Similarity and difference between the deuteration effect and the pressure effect are discussed. In the case of the strong H-bonds, like KH2PO4 and squaric acid (H2C4O4), deuteration corresponds to a negative pressure effect. However, there are some differences; H-bond is not necessarily the softest part of the crystal as usually assumed, and the pressure effect is responded by rotation of the PO4 or C4O4 group as well. On the other hand, in the case of (NH4)3H(SO4)2, deuteration corresponds to a positive pressure and a surprising similarity between deuteration and pressure effect exists in their phase diagrams.
Volumetric and Dielectric Studies on
by S. Urban1, A. Wuerflinger2, D. Buesing 2, T.
(Received May 28th, 1997)
The results of measurements of the specific volume Vm versus temperature T and pressure p are presented together with the new results of high pressure dielectric studies of 4-n-pentyl-4'-cyanobiphenyl (5CB) in the nematic and isotropic phase. The know-
Fixation by H-bonding of Ligands in Polymer Coils
by P. Huyskens, K. Nelis, Ch. Vael, K. Verstraeten and Th. Zeegers-Huyskens
(Received June 3rd, 1997)
The stability constants of H-bonds between phenols and the ester groups of polyethylmethacrylate (PEMA) in CCl4 determined by IR measurements, are of the same order of magnitude as those of the phenols with the low-molecular model substance ethylisobutyrate. In absence of additives, the cloud points at 25oC of PEMA (Mw = 258000) in CCl4-n-hexane mixtures are fairly well predicted by the equations of Huyskens et al. The presence of phenols displaces these cloud points towards higher values of the relative mole fraction of the cosolvent. This is also the case when acetone is used as additive. Beyond the cloud point, viscosity measurements show that practically no polymer coils remain in the supernatant liquid. However, after the phase separation, the additives behave in a completely different way. Dipolar measurements show indeed that the concentration of acetone in the supernatant liquid is of the same order as in the solution before the precipitation, whereas the phenol molecules are predominantly found in the precipitated flakes. This illustrates the fundamental difference between non-specific dipole-dipole interactions and specific intermolecular forces like H-bonds, whose characteristics were extensively studied during more than thirty years by Lucjan Sobczyk and his coworkers.
Decomposition of Mg(HSeO3)2.3H2O and Mg(HSeO3)2,
by B. Engelen, H. Mueller and K. Unterderweide
(Received June 10th, 1997)
By crystallization from aqueous Mg(HSeO3)2 solutions, single crystals of Mg(HSeO3)2.3H2O, Mg(HSeO3)2, and MgSe2O5 could be obtained. The compounds have been characterized by means of IR spectroscopy. The dehydration mechanisms of Mg(HSeO3)2.3H2O and Mg(HSeO3)2 have been studied using TG, DTA and high-temperature Raman techniques. DTA and TG measurements indicate that the thermal decomposition of Mg(HSeO3)2.3H2O results in the direct formation of the diselenite MgSe2O5. High-temperature Raman experiments under quasi static conditions (heating rate << 5 K/h, isothermal intervals of ~1h) show that Mg(HSeO3)2.3H2O decomposes in two steps under the intermediate formation of the anhydrous hydrogenselenite Mg(HSeO3)2.
Isotope Effects on Chemical Shifts in Tautomeric
by P.E. Hansen, M. Langgard and S. Bolvig
(Received June 25th, 1997)
Primary and secondary deuterium isotope effects on 1H and 13C chemical shifts are measured in citrinin, a tautomeric compound with an unusual doubly intramolecularly hydrogen bonded structure. The isotope effects are to a large extent dominated by equilibrium contributions and deuteration leads to more of the deuterated enol forms rather than the deuterated acid form. 1H, 13C and 17O nuclear shieldings are calculated using density functional ab initio methods. A very good correlation between calculated nuclear shieldings and experimental 1H and 13C chemical shifts is obtained. The tautomeric equilibrium can be analyzed based on the isotope effects on C-6 and C-8 carbons and shows an increase in the o-quinone form on lowering the temperature. Furthermore, upon deuteration the largest equilibrium shift is found for deuteration at OH-8 and the shift in the tautomeric equilibrium upon deuteration is increasing at lower temperature.
Aqueous Basicity and Proton Affinity of Flexible
by P. Barczynski, Z. Dega-Szafran and M. Szafran
(Received May 14th, 1997; revised manuscript July 7th, 1997)
pKa Values of 22 carboxybetaines in water were determined by potentiometric titration of their hydrohalides with KOH and their proton affinities (PA) in the gas phase were calculated using the AM1 method. The linear dependence of the pKa with 1/n implies that the distance between the two charged centers increases monotonically with the number of the methylene group (n). The calculated PA value for betaine is close to the experimental value. The acceptable results obtained for the correlation between pKa and PA, gives confidence to predict PA for the unknown betaines.
FT-IR and NMR Studies of the Proton Sponge Character of Cis-1,2-bis(diethylaminomethyl)cyclohexane
by B. Brzezinski1, E. Grech3, J. Klimkiewicz2, G. Schroeder1,
(Received April 15th, 1997: revised manuscript July 17th, 1997)
Cis-1,2-bis(diethylaminomethyl)cyclohexane (DEAMCH) was synthesised and its pKa values in acetonitrile were measured. Dual behaviour of DEAMCH was observed in the reaction with various acids: HClO4, 4-tert-butylphenol, 4-cyanophenol and pentachlorophenol (PCP) in acetonitrile and acetone-d6 solutions, respectively, when studied by FT-IR as well as 1H, 13C and 15N NMR spectroscopy. An intramolecular NHN+ hydrogen bond was found in 1:1 complex of DEAMCH with HClO4 in solution. This hydrogen bond was, however, weaker than those previously observed in other protonated proton sponges. In complexes of DEAMCH with 4-cyanophenol both NHN+ intramolecular hydrogen bond and structurally symmetrical intermolecular homoconjugated (OHO)- hydrogen bonds were formed. These properties of DEAMCH demonstrate its proton sponge like character. On the other hand, in complexes of DEAMCH with more acidic phenol such as PCP intermolecular hydrogen-bonded complexes are formed, in which the OH protons are localized at the amino groups. For these O-...HN+ hydrogen bonds a strongly asymmetrical double minimum proton potential with the well at the N atom is present, characteristic of complexes having no proton sponge like character.
Raman Spectroscopy of the Hydrogen Bond
by A. Potier, J. Potier, M.H. Herzog and J.F. Herzog
(Received May 28th, 1997; revised manuscript July 28th, 1997)
The discontinuous shifts of Raman lines with the concentration between 500 and 2600 cm-1 in solutions of HNO3-H2O and KNO3-HNO3 show the formation of the associates H2O.HNO3 and (HNO3)2.NO3-. The study of the 2000-3600 cm-1 range enhances the complexity of the OH' spectra with the occurrence of Evans windows, owing to the formation of hydrogen bonds in the two associates.
Thin Film Transmission Spectra and Vibrational
by W. Wrzeszcz, B. Czarnik-Matusewicz and J.P. Hawranek
(Received August 4th, 1997)
Thin film transmission spectra of liquid pyridine were measured in the 3300-500 cm-1 region, using cells of thicknesses ranging from 1.4 µm to 522 µm. The spectrum of the absorption index was determined from these data in the Mid-IR range. Vibrational intensities and other spectral parameters were calculated from the k() spectrum. The assignment of numerous bands was carried out. The data were compared with results of recent DFT calculations of the infrared spectrum of pyridine.
Infrared Studies on the Structural Phase Transitions
by G. Bator, R. Jakubas and I. Majerz
(Received May 26th, 1997; revised manuscript August 25th, 1997)
Internal vibration modes of (n-C3H7NH3)2SbBr5 and (n-C3H7NH3)3Sb2Cl9 were studied through their phase transitions using the infrared spectroscopy. The studies show that the vibrational states of the n-propylammonium cations change considerably during the phase transitions. The (CC), (CN) and s(NH) bands are very sensitive to the phase transition at 154 K in (n-C3H7NH3)2SbBr5, and at 232 K in (n-C3H7NH3)3Sb2Cl9. IR spectra point out the key role of the n-propylammonium cations in the phase transition mechanism of both crystals.
Transformation of the 3-Oxoazabicyclo[2.2.2]octane Pentachlorophenol Complex
by I. Majerz, Z. Malarski and T. Lis
(Received May 28th, 1997; revised manuscript August 27th, 1997)
The transformation of the 3-oxoazabicyclo[2.2.2]octane pentachlorophenol complex in methanol (and CH3OD) solution into the 3-hydroxy-3-methoxy-azabicyclo[2.2.2]octane pentachlorophenolate is described. The presence of the acidic phenol proton were sufficient to promote such a reaction. The crystal structures of the 3-hydroxy-3-met-hoxyazabicyclo[2.2.2]octane pentachlorophenolate and its deuterated analogue were determined by X-ray method. IR spectra indicate an ionic character of the complexes and a moderately strong N+-H...O- and N+-D...O- hydrogen bonds with the isotopic ratio (NH)/(ND) equal to 1.22. Weaker intermolecular O-H...O- and O-D...O- hydrogen bridges exhibit the isotopic ratio (OH)/(OD) 1.34.
Matrix Infrared Spectra of C6H6-HNO3
by M. Krajewska and Z. Mielke
(Received July 8th, 1997; revised manuscript September 15th, 1997)
Infrared spectra of the complexes between C6H6 and HNO3, trans-HONO and cis-HONO in solid argon are reported. Nitric acid and both isomers of nitrous acid form stable 1:1 hydrogen bonded complexes in which the OH group of an acid is interacting with the -electron system of benzene ring. In addition the nitric acid appears to form another 1:1 complex in which both OH and NO2 group interact directly with the benzene ring. In both benzene-nitric acid and benzene-nitrous acid systems the higher order aggregates (C6H6)nHNO3, (C6H6)nHONO n 2 are easily formed.
X-ray, IR and 1H NMR Studies of 1:1 Adduct
by E. Bartoszak-Adamska1, E. Grech2 and M. Jaskolski1
(Received September 22nd, 1997)
The crystal and molecular structure of the title compound has been determined by X-ray analysis. The compound crystallizes in the P21/c space group with cell parameters: a = 9.325(2) b = 15.158(3), c = 14.102(3) , ß = 106.40(3)o and with four C14H19N2+.C6H7O4- formula units in the unit cell. The structure contains DMANH+ cations with a short asymmetric intramolecular N-H...N hydrogen bond (N...N 2.595(2) ) and CBDC- monoanions with a short intramolecular O-H...O hydrogen bond (O...O 2.412(3) ). The ionic character of the very strong (NHN)+ and moderately strong (OHO)- hydrogen bonds has been derived from IR spectroscopy. The 1H NMR spectrum measured in acetonitrile solution is similar to that in the solid state.
An Ab InitioCalculation of the Vibrational Spectrum
by M. Szafran and J. Koput
(Received March 17th, 1997)
Density functional theory (using Becke's exchange and Lee-Young-Parr's correlation functionals (BLYP)) and ab initio second-order Moller-Plesset (MP2) calculations were carried out in order to investigate the molecular structure and vibrational spectra of pyridine N-oxide and its perdeuterated analog. The calculated structural and spectral features are in good agreement with the available experimental results. Most of the BLYP/6-31G(d,p) and MP2/6-31G(d,p) non-CH stretching frequencies are slightly lower than the reliable experimental assignments; the mean deviations are 23 and 21 cm-1, respectively. On the basis of agreement between calculated and experimental results, assignments of the fundamental vibrational modes were examined and some reassignments were proposed.
A Study of H-Bonded (HF)n Clusters within the
by N.D. Sokolov1 and V.A. Savel'ev2
(Received June 26th, 1997)
Properties of H-bonded linear (HF)n clusters are considered in terms of the electrostatic model. The expression for the potential energy of such clusters includes Coulomb interaction of effective (residual) atomic charges, the polarizing action of these charges on neighboring molecules, and the exchange repulsion between nearest neighbors. This model was used to calculate the energy of the formation of the dimer (HF)2 and the trimer (HF)3, s(HF) frequency shifts accompanying the formation of these clusters, and the dependence of the dipole moment and the intensity of the s(HF) vibration on the number of molecules in the (HF)n cluster. The results are in satisfactory agreement with the experiment and with ab initio calculation data. The contributions of cooperative (trimolecular) interaction to the energy of the trimer (~ 8%) and the frequency shift and the intensity of the s(HF) mode (1-2%) were determined. In the weak-field approximation, the dipole moment does not include cooperative effects.
Application of the VSCF Theory to Coupled
by P.J. Piskorz and M.J. Wojcik
(Received May 9th, 1997; revised manuscript June 30th, 1997)
The Vibrational Self-Consistent Field (VSCF) method is used to solve the problem of vibrational couplings in hydrogen-bonded systems. This method leads to a system of coupled equations which can be solved and allow to calculate infrared vibrational X-H and X-D bands. The VSCF method is used to calculate spectra of hydrogen-bonded uracil and 1-methyluracil crystals and is compared with previously used overlap integral method in the adiabatic approximation. The advantages of the new method are discussed.
An Application of Group Theory
by M. Kozlowski and H.A. Kolodziej
(Received June 16th, 1997; revised manuscript August 18th, 1997)
The dielectric relaxation of some three site models systems is evaluated using group theory to solve the basic rate equations to predict the relaxation in some simple cases.
Matrix Isolation and Dft Quantum Mechanical
by K. Szczepaniak1, W.B. Person1, J. Leszczynski2 and J.S. Kwiatkowski3
(Received August 20th, 1997)
The infrared spectra of uracil and its derivatives in the carbonyl region are strikingly complex, and extremely sensitive to substitution, particularly at ring nitrogens. In this work the infrared spectra of uracil, 1,3-di-deuterouracil, 1-methyluracil, 3-methyluracil and 1,3-dimethyluracil are studied experimentally by low temperature (12 K) matrix isolation infrared spectroscopic techniques, and theoretically by DFT/B3LYP/6-31G(d,p) quantum mechanical methods. Particular attention is focused on the carbonyl region and on the mechanical coupling of the C2=O and C4=O stretching vibrations with each other, with the N1H and N3H bending motions, and with other motions. It is shown that this coupling plays a crucial role in determining the frequencies and intensities of the normal modes that determine the spectral patterns in the infrared spectrum in the carbonyl region. The extreme sensitivity of the frequencies, intensities and spectral pattern in the carbonyl region to isotopic substitution and methylation (and to the intermolecular interactions, particularly hydrogen bonding) is attributed, to a large extent, to changes in this coupling. The DFT calculations appear to give quite accurate values for the force constants and allow separation of simple mass effects and chemical substituent effects on the coupling. Fermi resonance in the carbonyl region is an important factor contributing to the observed complexity of this spectral region. Examination of this effect making use of the visualization of normal modes of vibration provides rules for when it may be expected to be important.
Quantum Chemical Studies of the Double Proton Transfer in Oxalic Acid Dimer
by H. Chojnacki
(Received August 4th, 1997; revised manuscript September 11th, 1997)
The double proton transfer process has been studied for the oxalic acid dimer in the gaseous state and for crystalline form at the non-empirical level. The correlation energy corrections have been taken into account at the MP2 level as well as crystal field effects were considered. The results of our calculations enable a reasonable interpretation of low potential barriers, observed in NMR experimental studies of some molecular crystals involving carboxylic dimers. The possible mechanisms of the double proton transfer are considered.
Phase Transformations in Locally Anharmonic Systems. Susceptibility Approach to Orientational
by B. Kuchta and T. Luty
(Received October 6th, 1997)
A model of the structural transformation has been discussed, where the local potential is anharmonic but single-welled. Such potential represents a Hamiltonian to model the structural phase transition in charge-transfer molecular crystals A-TCNB (anthracene-tetracyanobenzene). The conditions for the instability and transformation have been found, using the static susceptibility approach, and compared with the variational approximation. The latter method gives a six times lower transition temperature. The fluctuations and entropy are pointed out as the cause of this difference. The exact transition temperature has been calculated by simple Monte Carlo simulations. A comparison with a double-welled case, which models the structural transition in N-TCNB molecular crystal (naphthalene-tetracyanobenzene), has been presented.
The Structure of Narlumicine
by E. Tykarska, M. Chrzanowska and Z. Kosturkiewicz
(Received February 12th, 1997)
The crystals of racemic narlumicine, C21H21NO7, 6-[[6-[2-(dimethylamino) ethyl]-1,3benzodioxol-5-yl]hydroxymethyl]furo[3,4-e]-1,3-benzodioxol-8(6H)-one, have been investigated by X-ray diffraction methods. The crystals are monoclinic, space group P21/c, a = 10.792(2), b = 18.064(4), c = 10.053(3) , ß = 104.77(3)o, Z = 4. The structure was solved by direct methods and refined to R = 0.036 for 2149 observed reflections. The three-cycle and two-cycle moieties are nearly planar and the dihedral angle between them is 63.5o. The sum of bond angles around the nitrogen atom is 330.2o. The fourth apex of the pyramid is occupated by the O-H...N hydrogen bond. The intermolecular hydrogen bond O-H...N (2.716(5) ) links the molecules into chains parallel to the y axis.
The Crystal and Molecular Structure of Cyclic Thioamide ß-Diketone Derivatives. Intramolecular
by R. Anulewicz1, T.M. Krygowski1 and T. Jagodzinski2
(Received May 6th, 1997; revised manuscript June 12th, 1997)
Crystal and molecular structures of the 2,6-dioxocyclohexanethiocarboxanilide (I), 4,4-dimethyl-2,6-dioxocyclohexanethiocarboxanilide (II) and 1,3-indandione-2-thiocarboxanilide (III) have been determined by use of X-ray diffraction technique on a Kuma-diffractometer. Crystal data for compound (I): C13H13N1O2S1, Mr = 247.32, monoclinic, C2/c, a = 22.704(5) , b = 7.312(1) , c = 17.192(3) , ß = 123.07(3), Z = 8, R = 0.0597 for 2181 reflections. Compound (II): C15H17N1O2S1, Mr = 275.36, triclinic, P-1, a = 10.748(1) , b = 9.223(2) , c = 7.346(2) , = 91.21(3), ß = 100.36(3), = 76.01(3), Z = 2, R = 0.0733 for 2485 reflections. Compound (III): C16H11N1O2S1, Mr = 281.12, triclinic, P-1, a = 6.945(3) , b = 8.786(1) , c = 12.435(3) , = 86.97(3), ß = 73.78(3), = 66.74(3), Z = 2, R = 0.0696 for 2361 reflections. Of the two potentially H-bonding systems of each of the title compounds one that with OH...S, is stronger and this results in a stronger -electron delocalization. This is quantitatively measured by HOMA index, which is by ca. 0.3 units larger than for the other H-bonding system, the one with the NH...O bridge.
Modelling Hydrogen-bonded Crystal Structures
by A. Katrusiak
(Received June 30th, 1997; revised manuscript July 29th, 1997)
Knowledge of molecular geometry, combined with the predictions of preferred molecular orientation, can yield details of disordered crystal structures difficult to investigate by diffraction methods. The R-OH- -O'-R' hydrogen bond dimensions O-H, H- -O, R-O-H, and H- -O'-R' chiefly depend on the electronic structure of the proton-donor and acceptor groups. Thus, when hydrogen-bonded aggregates undergo transformations, such as hydrogen-bonds breaking, concerted H-transfers or H-disordering, the molecular rearrangements are coupled with the H-sites. This interdependence is exemplified by a one-dimensional model of a hydrogen-bonded aggregate, and the real structures and thermodynamic properties of H2O ice and H3BO3 orthoboric acid.
Crystal and Molecular Structure of
by K. Wozniak1, R. Anulewicz1, E. Grech2 and A. Szady2
(Received June 12th, 1997; revised manuscript August 5th, 1997)
Structural and spectroscopic properties of solid 2-(N,N-diethylamino)-methyl-4-bromo-6-formylphenol have been investigated. There are two molecules of the title compound in the independent part of the unit cell with only minor structural differences. This is an example of a Mannich base containing a neutral [O-H...N] intramolecular hydrogen bonding. Single crystal X-ray diffraction shows that the title molecule is dominated by neutral Kekule structures. Being involved in a strong intramolecular [O-H...N] hydrogen bonding, 2-(N,N-diethylamino)-methyl-4-bromo-6-formylphenol forms its crystal lattice by means of different types of weak intermolecular [C-H...O], and C-H...Br hydrogen bonds.
Molecular Structure of Pyridine N-Oxide Complex
by E. Tykarska, Z. Dega-Szafran, M. Grundwald-Wyspianska and M. Szafran
(Received May 14th, 1997; revised manuscript October 6th, 1997)
A complex of pyridine N-oxide (PyO) with 2,6-dichloro-4-nitrophenol (DCNP) was studied by X-ray diffraction, FT-IR spectroscopy and quantum-mechanical calculations with the DFT and semiempirical methods. The crystals of the PyO.DCNP are triclinic, space group P1-, a = 6.833(1) , b = 8.717(2) , c = 11.482(2) , = 98.93(2)o, ß = 93.63 (1)o, = 109.12(2)o, V = 633.6(3) 3, Z = 2. The molecules of the complex are joined by the N-O...H-O hydrogen bond with the O...O distance of 2.476(2) and the O(4)...H(1)-O(1) angle of 165.1o. The dihedral angle between the planes of the bridged pyridine and phenyl rings is 71.8o. The weak C-H...O, C-H...Cl interactions and stacking forces stabilize three dimensional packing pattern. The SAM1 and DFT methods predict one minimum for B...H-A form, while the PM3 method predicts two minima, the deeper one for B...H-A complex and the shallower one for B+-H...A- form. For the most stable complexes the predicted O...O distances are longer than the experimental value by 0.141, 0.067 and 0.231 , respectively for the DFT, SAM1 and PM3 methods. The calculated bond lengths, except N(1)-O(4), are longer than those from the X-ray as results of intermolecular interactions in the crystal. The SAM1 geometry of PyO.DCNP is slightly better than this obtained by the PM3 method and it is recommended as input in ab initio calculations. The protonic broad absorption in the 1500-250 cm-1 region is typical for such a short hydrogen bond and the proton motion may be described by a potential curve with an asymmetric double minimum. Proton motion in the bridge is faster than the time range of IR spectroscopy.
Spectroscopic Study of Inclusion Complexes
by B. Szafran and J. Pawlaczyk
(Received May 26th, 1997; revised manuscript June 25th, 1997)
Return to main page.
© 1998 Polish Journal of Chemistry
prepared by (aws)