Ljupco Pejov - Academia.edu (original) (raw)
Papers by Ljupco Pejov
Croatica Chemica Acta, 2000
A quantum theoretical basis for the experimentally observed vibrational Stark shifts of the sulfa... more A quantum theoretical basis for the experimentally observed vibrational Stark shifts of the sulfate internal modes in SO4 doped K2SeO4, Rb2SeO4 and Cs2SeO4 is presented. Analytical first order perturbation theoretical expressions are derived for the field-dependent wavenumbers of the 1 0 and 2 0 transitions, harmonic wavenumbers, as well as for the Stark tuning rate and the electrostatic field strength at the Cs sites of the host lattices. It is shown that the local field differences are the factor dominating over the differences in the anharmonicities of the guest anions in various host lattices, and are thus responsible for the experimentally observed trends. The proposed method allows calculation of the local crystalline field strength if the anharmonic potential energy parameters of the dopant anions are known. The calculated values for the studied series of matrices range from 229 to 259 V nm–1, which are approximately 3 times larger than those reported for water molecule sites...
Vibrational Spectroscopy, 2017
The work represents continuation of the vibrational spectra interpretation and spectra-structure ... more The work represents continuation of the vibrational spectra interpretation and spectra-structure correlation carried out on the minerals originating from Macedonia, herein, with concern on the assignment of bands in the vibrational spectra of the only and very rare Tl-sulfate representative from Allchar minedorallcharite, (Tl,K)Fe 3 (SO 4) 2 (OH) 6. The mineral occurs in very small (0.1 mm) yellow balls and is structurally classified in the jarosite-alunite family. The SEM-EDS analysis revealed the following chemical formula, (Tl 0.83 K 0.17)Fe 3 (SO 4) 2 (OH) 6 with the sample authenticity additionally confirmed by XRPD. The infrared spectrum shows great similarity with the previously interpreted jarosite IR spectrum. The spectral view in the region of the n 3 (SO 4), n 1 (SO 4) and n 4 (SO 4) modes makes it exceptionally difficult to discriminate between dorallcharite and jarosite. On the contrary, the bands arising from the Fe-O stretching modes around 505 and 468 cm À1 , which are red shifted for 7-9 cm À1 due to the longer Fe-O (av) distances in dorallcharite (2.028 Å) compared to shorter corresponding contacts in jarosite structure (2.012 Å), facilitate their differentiation. The Raman spectrum was also interpreted confirming pure mineral phase due to the possibility for microscopically point-and-shoot spectral collection. Additionally, to support the assignment of the experimental bands, IR spectra of both minerals were theoretically simulated using a 3D periodic density functional theory approach applying various combinations of exchange-correlation functionals.
Macedonian Pharmaceutical Bulletin
In the present scientific workflow, through the example of this simplest organic acid we’ll illus... more In the present scientific workflow, through the example of this simplest organic acid we’ll illustrate the approach to compute the anharmonic vibrational frequencies of characteristic X-H intramolecular chromophores which are treatable within 1D approximation (i.e. as one-dimensional anharmonic oscillators). The approach is straightforwardly extendable to an arbitrary X-Y oscillator.
![Research paper thumbnail of Computational studies of the C-13 and H-1 NMR isotropic chemical shifts using density functional optimized geometries. Adamantane and 2,4-methano-2,4-dehydroadamantane (a [3.1.1]propellane) as case studies](https://attachments.academia-assets.com/112013619/thumbnails/1.jpg)
](The C-13 and H-1 chemical shift values computed at HF, BLYP and B3LYP/6-311G(d,p) levels of theor... more The C-13 and H-1 chemical shift values computed at HF, BLYP and B3LYP/6-311G(d,p) levels of theory, for the BLYP/6-31G(d,p) optimized geometries of adamantane and 2,4-methano-2,4-dehydroadamantane, are reported and compared with the available experimental data. Except for the inverted carbon atoms, the HF values are superior to the DFT ones when the isotropic shifts with respect to TMS are in question. However, in case of the relative shifts computed with respect to the most deshielded center within the molecule, the DFT methods yield significantly better agreement with the experiment than the HF. The most probable reason for these findings may be the cancellation of errors arising from the inappropriate description of the paramagnetic contributions to the overall shielding tensor within the Kohn-Sham approach when an internal standard (within a molecule) is chosen, instead of an external one. The CSGT relative shift values correlate better with the experiment than the GIAO ones, th...
In this scientific workflow a method for efficient processing of the results from MD simulations ... more In this scientific workflow a method for efficient processing of the results from MD simulations is presented. In the particular case considered, the results from Born-Oppenheimer MD (BOMD) simulations, generated either with Gaussian09 or ORCA 4.0 series of codes will be used.
Journal of Molecular Liquids, 2002
ACS Omega, 2020
The synthesis of two polyhydroxylated pyrrolidines as 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) an... more The synthesis of two polyhydroxylated pyrrolidines as 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) analogues bearing a hydrazide moiety is described. The DAB analogues act as selective and potent inhibitors of α-mannosidase in the submicromolar concentration ranges (K i values ranging from 0.23 to 1.4 μM).
Journal of the American Chemical Society, May 21, 2020
Melting of any pure crystalline material at constant pressure is one of its most fundamental prop... more Melting of any pure crystalline material at constant pressure is one of its most fundamental properties, and it has been used to identify organic compounds or to verify their chemical or phase purity since the early times of chemistry. Here, we report that a mechanical deformation of plastic organic single crystals such as bending results in a small, yet significant decrease in their melting point of about 0.3─0.4 K. The bent section of the crystal was found to be mechanically softer relative to the straight one, and the softening temperature preceding the melting was also lower on the convex (outer) side of the bent crystal. Melting of the bent crystal starts at the kink and often appears as splitting of the respective endothermic peak in its thermal (DSC) fingerprint, while unilateral compression of the crystal results in multiple peaks. These thermomechanical effects become more pronounced with heavier mechanical damage due to increased concentration of defects and ultimately result in a large temperature spread of the associated phase change in addition to melting point depression in deformed or damaged crystals relative to their pristine counterparts. Within a broader context, the results show that mechanical treatment during sample preparation has a profound effect on the melting of a pure substance, and this could be critically important where the exact melting point is used as means for polymorph identification.
Makedonsko farmacevtski bilten, 2018
The purpose of this work was to formulate prolonged release matrix tablets with water soluble opi... more The purpose of this work was to formulate prolonged release matrix tablets with water soluble opioid drug (API) using different types of hydroxypropylmethyl cellulose (Methocel) as controlled release polymers. Methocel K100M was incorporated as intra-granular polymer (sample 1) along with Methocel K4M (sample 2) or Methocel K15M (sample 3) as extra-granular polymers. The final blends and tablets prepared by wet granulation process were fully characterized. Results showed that the polymer used extra-granularly significantly affects the tablet properties. By incorporation of Methocel extra granularly (samples 2 and 3), the hardness and tensile strength of the tablets increased and the total tablet porosity decreased. Sample 1, containing only Methocel K100M (intra granularly) has the lowest index of swelling and the fastest release of API probably due to the cross-linking of the polymer chains during the process of wet granulation. Also, the type of Methocel used extra-granularly (with different viscosity grade) was found to significantly affect the swelling ratio of the designed matrix systems and the drug release behavior. Sample 2 containing Methocel K4M extra-granularly has a lower index of swelling and faster release of API compared to sample 3. Considering the release mechanism, release data showed best fitting to the heuristic model proposed by Korsmeyer-Peppas. Two additional approaches were used for mathematical modeling of the release data in order to make them directly applicable for our experimental results.
Related Article: P.Naumov, N.Ishizawa, Jun Wang, L.Pejov, M.Pumera, Sang Cheol Lee|2011|J.Phys.Ch... more Related Article: P.Naumov, N.Ishizawa, Jun Wang, L.Pejov, M.Pumera, Sang Cheol Lee|2011|J.Phys.Chem.A|115|8563|doi:10.1021/jp2040339
Journal of The Serbian Chemical Society, 1998
Crystal Growth & Design, Mar 5, 2008
The crystal lattice of the isomorphous tetraaquabis(saccharinate)metal(II) dihydrates was employe... more The crystal lattice of the isomorphous tetraaquabis(saccharinate)metal(II) dihydrates was employed as a structurally flexible coordination framework capable of sustaining large internal distortions to study the competitive inclusion of Jahn-Teller (JT) distorted d 9 ions, [Cu(H 2 O) 4 (sac) 2 ] 2+ , and JT-inactive d 5 ions, [Mn(H 2 O) 4 (sac) 2 ] 2+ , in binary solid solutions under thermodynamically controlled conditions of statistical mixing (sac) saccharinate anion, C 7 H 4 NO 3 S-). Probing of the metal content of the solid phase showed a two-regime inclusion profile: increasing the ratio of the distorted cation relative to the undistorted one in the solution phase of up to about 35% results in linear dependence and preferred inclusion of the former with maximum concentration of 100% in the crystal and complete exclusion of the undistorted ion above that point. A mixed crystal with highest copper ratio of 63% was obtained from solution with 25% copper, which under the P2 1 /c crystal symmetry corresponds to sustainable integrity of the undistorted lattice by substitution of up to 2 / 3 of its sites. This stability limit shows that four out of the six sites around each [Mn(H 2 O) 4 (sac) 2 ] 2+ ion can be substituted by distorted [Cu(H 2 O) 4 (sac) 2 ] 2+ guests under conditions of thermodynamically controlled, statistically averaged exchange. The undistorted host is very tolerant toward inclusion of strongly distorted guests. When acting as host, the distorted ion is more discriminatory toward the undistorted guest. Along with the expectation from the JT theory, structural refinement of seven crystals, including a mixed crystal with composition of [Cu 0.126 Mn 0.874 (H 2 O) 4 (C 7 H 4 NO 3 S) 2 ](H 2 O) 2 , showed that metal-ligand distances are significantly affected by the metal substitution. Inclusion of the JT-active ion results in distortion of the coordination polyhedron by increasing the bond length difference between the two metal-O(water) bonds and also causes shortening of the M-N bond. Due to the rigidness caused by π-conjugation, the overall effect on the endocyclic geometry of the organic ligand is small. The anisotropic distortions around the metal ion are faithfully reflected in the stretching force constants of the coordinated water molecules and thus in the IR spectrum of the mixed crystals.
Journal of Raman Spectroscopy, Jan 18, 2018
This work represents the first complete experimental and theoretical study of the infrared (IR) s... more This work represents the first complete experimental and theoretical study of the infrared (IR) spectra of pharmacolite, Ca(AsO 3 OH)•2H 2 O; vladimirite, Ca 4 (AsO 3 OH)(AsO 4) 2 •4H 2 O; and picropharmacolite, Ca 4 Mg(AsO 3 OH) 2 (AsO 4) 2 •11H 2 O. IR spectra, collected at both room and liquid nitrogen temperature, have shown similar spectral view among minerals in the region of ν 1 to ν 4 modes, surprisingly not involving complexity in vladimirite and picropharmacolite spectral view due to the presence of both AsO 3 OH and AsO 4 units compared to pharmacolite where only AsO 3 OH units appear in the structure. On the other hand, vladimirite and picropharmacolite Raman spectra in the corresponding ν 1 to ν 4 region (955-350 cm −1) exhibit existence of 3 sets of 2 bands (6 in total) completely reflecting the existence of 3 symmetrically nonequivalent AsO 4 groups in the structures of vladimirite and picropharmacolite (of which one is protonated) and only one set of ν 1 to ν 4 bands from the structurally equivalent AsO 3 OH units in the pharmacolite structure. The liquid nitrogen temperature IR spectra enabled to infer important information regarding the OH vibrational bands related to the AsO 3 OH groups and to the water molecules. Essentially, all bands in the vibrational spectra were assigned and correlated with the findings for a plethora of structurally similar complex hydrogen arsenate minerals. To support the tentative assignment of bands in the vibrational spectra, quantum theoretical calculations were performed within the framework of density functional theory. On the basis of theoretical calculations, a few reassignments of bands appearing in the OH stretching region are proposed. X-ray powder diffraction was used to confirm authenticity of the title systems.
The ill. intensities of the bands due to OD stretching vibrations of lIDO molecules increase, as ... more The ill. intensities of the bands due to OD stretching vibrations of lIDO molecules increase, as a mle, with the increasing strength of the hydrogen bonds. One is apt to explain this behaviour in terms of non-statistical substitution of hydrogen with deuterium, the deuterium thus preferring the stronger bonds. It has been shown [I] that this notion fails to explain the intensity differences in the OH stretching region. hl the present paper an Einstein model of a crystal containing two types of hydrogen bond is considered, at a temperature low enough to prohibit creation/existence of phonons in the crystal. The most probable HID distribution is the one leading to minimisation of the Gibbs energy of the crystal. The results of the model show that deuterium atoms, as a mle, prefer weaker hydrogen bonds but in certain cases (two very strong bonds or one extremely weak hydrogen bond) might prefer stronger hydrogen bonds as well.
Related Article: P.Naumov, N.Ishizawa, Jun Wang, L.Pejov, M.Pumera, Sang Cheol Lee|2011|J.Phys.Ch... more Related Article: P.Naumov, N.Ishizawa, Jun Wang, L.Pejov, M.Pumera, Sang Cheol Lee|2011|J.Phys.Chem.A|115|8563|doi:10.1021/jp2040339
Croatica Chemica Acta, 2000
A quantum theoretical basis for the experimentally observed vibrational Stark shifts of the sulfa... more A quantum theoretical basis for the experimentally observed vibrational Stark shifts of the sulfate internal modes in SO4 doped K2SeO4, Rb2SeO4 and Cs2SeO4 is presented. Analytical first order perturbation theoretical expressions are derived for the field-dependent wavenumbers of the 1 0 and 2 0 transitions, harmonic wavenumbers, as well as for the Stark tuning rate and the electrostatic field strength at the Cs sites of the host lattices. It is shown that the local field differences are the factor dominating over the differences in the anharmonicities of the guest anions in various host lattices, and are thus responsible for the experimentally observed trends. The proposed method allows calculation of the local crystalline field strength if the anharmonic potential energy parameters of the dopant anions are known. The calculated values for the studied series of matrices range from 229 to 259 V nm–1, which are approximately 3 times larger than those reported for water molecule sites...
Vibrational Spectroscopy, 2017
The work represents continuation of the vibrational spectra interpretation and spectra-structure ... more The work represents continuation of the vibrational spectra interpretation and spectra-structure correlation carried out on the minerals originating from Macedonia, herein, with concern on the assignment of bands in the vibrational spectra of the only and very rare Tl-sulfate representative from Allchar minedorallcharite, (Tl,K)Fe 3 (SO 4) 2 (OH) 6. The mineral occurs in very small (0.1 mm) yellow balls and is structurally classified in the jarosite-alunite family. The SEM-EDS analysis revealed the following chemical formula, (Tl 0.83 K 0.17)Fe 3 (SO 4) 2 (OH) 6 with the sample authenticity additionally confirmed by XRPD. The infrared spectrum shows great similarity with the previously interpreted jarosite IR spectrum. The spectral view in the region of the n 3 (SO 4), n 1 (SO 4) and n 4 (SO 4) modes makes it exceptionally difficult to discriminate between dorallcharite and jarosite. On the contrary, the bands arising from the Fe-O stretching modes around 505 and 468 cm À1 , which are red shifted for 7-9 cm À1 due to the longer Fe-O (av) distances in dorallcharite (2.028 Å) compared to shorter corresponding contacts in jarosite structure (2.012 Å), facilitate their differentiation. The Raman spectrum was also interpreted confirming pure mineral phase due to the possibility for microscopically point-and-shoot spectral collection. Additionally, to support the assignment of the experimental bands, IR spectra of both minerals were theoretically simulated using a 3D periodic density functional theory approach applying various combinations of exchange-correlation functionals.
Macedonian Pharmaceutical Bulletin
In the present scientific workflow, through the example of this simplest organic acid we’ll illus... more In the present scientific workflow, through the example of this simplest organic acid we’ll illustrate the approach to compute the anharmonic vibrational frequencies of characteristic X-H intramolecular chromophores which are treatable within 1D approximation (i.e. as one-dimensional anharmonic oscillators). The approach is straightforwardly extendable to an arbitrary X-Y oscillator.
The C-13 and H-1 chemical shift values computed at HF, BLYP and B3LYP/6-311G(d,p) levels of theor... more The C-13 and H-1 chemical shift values computed at HF, BLYP and B3LYP/6-311G(d,p) levels of theory, for the BLYP/6-31G(d,p) optimized geometries of adamantane and 2,4-methano-2,4-dehydroadamantane, are reported and compared with the available experimental data. Except for the inverted carbon atoms, the HF values are superior to the DFT ones when the isotropic shifts with respect to TMS are in question. However, in case of the relative shifts computed with respect to the most deshielded center within the molecule, the DFT methods yield significantly better agreement with the experiment than the HF. The most probable reason for these findings may be the cancellation of errors arising from the inappropriate description of the paramagnetic contributions to the overall shielding tensor within the Kohn-Sham approach when an internal standard (within a molecule) is chosen, instead of an external one. The CSGT relative shift values correlate better with the experiment than the GIAO ones, th...
In this scientific workflow a method for efficient processing of the results from MD simulations ... more In this scientific workflow a method for efficient processing of the results from MD simulations is presented. In the particular case considered, the results from Born-Oppenheimer MD (BOMD) simulations, generated either with Gaussian09 or ORCA 4.0 series of codes will be used.
Journal of Molecular Liquids, 2002
ACS Omega, 2020
The synthesis of two polyhydroxylated pyrrolidines as 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) an... more The synthesis of two polyhydroxylated pyrrolidines as 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) analogues bearing a hydrazide moiety is described. The DAB analogues act as selective and potent inhibitors of α-mannosidase in the submicromolar concentration ranges (K i values ranging from 0.23 to 1.4 μM).
Journal of the American Chemical Society, May 21, 2020
Melting of any pure crystalline material at constant pressure is one of its most fundamental prop... more Melting of any pure crystalline material at constant pressure is one of its most fundamental properties, and it has been used to identify organic compounds or to verify their chemical or phase purity since the early times of chemistry. Here, we report that a mechanical deformation of plastic organic single crystals such as bending results in a small, yet significant decrease in their melting point of about 0.3─0.4 K. The bent section of the crystal was found to be mechanically softer relative to the straight one, and the softening temperature preceding the melting was also lower on the convex (outer) side of the bent crystal. Melting of the bent crystal starts at the kink and often appears as splitting of the respective endothermic peak in its thermal (DSC) fingerprint, while unilateral compression of the crystal results in multiple peaks. These thermomechanical effects become more pronounced with heavier mechanical damage due to increased concentration of defects and ultimately result in a large temperature spread of the associated phase change in addition to melting point depression in deformed or damaged crystals relative to their pristine counterparts. Within a broader context, the results show that mechanical treatment during sample preparation has a profound effect on the melting of a pure substance, and this could be critically important where the exact melting point is used as means for polymorph identification.
Makedonsko farmacevtski bilten, 2018
The purpose of this work was to formulate prolonged release matrix tablets with water soluble opi... more The purpose of this work was to formulate prolonged release matrix tablets with water soluble opioid drug (API) using different types of hydroxypropylmethyl cellulose (Methocel) as controlled release polymers. Methocel K100M was incorporated as intra-granular polymer (sample 1) along with Methocel K4M (sample 2) or Methocel K15M (sample 3) as extra-granular polymers. The final blends and tablets prepared by wet granulation process were fully characterized. Results showed that the polymer used extra-granularly significantly affects the tablet properties. By incorporation of Methocel extra granularly (samples 2 and 3), the hardness and tensile strength of the tablets increased and the total tablet porosity decreased. Sample 1, containing only Methocel K100M (intra granularly) has the lowest index of swelling and the fastest release of API probably due to the cross-linking of the polymer chains during the process of wet granulation. Also, the type of Methocel used extra-granularly (with different viscosity grade) was found to significantly affect the swelling ratio of the designed matrix systems and the drug release behavior. Sample 2 containing Methocel K4M extra-granularly has a lower index of swelling and faster release of API compared to sample 3. Considering the release mechanism, release data showed best fitting to the heuristic model proposed by Korsmeyer-Peppas. Two additional approaches were used for mathematical modeling of the release data in order to make them directly applicable for our experimental results.
Related Article: P.Naumov, N.Ishizawa, Jun Wang, L.Pejov, M.Pumera, Sang Cheol Lee|2011|J.Phys.Ch... more Related Article: P.Naumov, N.Ishizawa, Jun Wang, L.Pejov, M.Pumera, Sang Cheol Lee|2011|J.Phys.Chem.A|115|8563|doi:10.1021/jp2040339
Journal of The Serbian Chemical Society, 1998
Crystal Growth & Design, Mar 5, 2008
The crystal lattice of the isomorphous tetraaquabis(saccharinate)metal(II) dihydrates was employe... more The crystal lattice of the isomorphous tetraaquabis(saccharinate)metal(II) dihydrates was employed as a structurally flexible coordination framework capable of sustaining large internal distortions to study the competitive inclusion of Jahn-Teller (JT) distorted d 9 ions, [Cu(H 2 O) 4 (sac) 2 ] 2+ , and JT-inactive d 5 ions, [Mn(H 2 O) 4 (sac) 2 ] 2+ , in binary solid solutions under thermodynamically controlled conditions of statistical mixing (sac) saccharinate anion, C 7 H 4 NO 3 S-). Probing of the metal content of the solid phase showed a two-regime inclusion profile: increasing the ratio of the distorted cation relative to the undistorted one in the solution phase of up to about 35% results in linear dependence and preferred inclusion of the former with maximum concentration of 100% in the crystal and complete exclusion of the undistorted ion above that point. A mixed crystal with highest copper ratio of 63% was obtained from solution with 25% copper, which under the P2 1 /c crystal symmetry corresponds to sustainable integrity of the undistorted lattice by substitution of up to 2 / 3 of its sites. This stability limit shows that four out of the six sites around each [Mn(H 2 O) 4 (sac) 2 ] 2+ ion can be substituted by distorted [Cu(H 2 O) 4 (sac) 2 ] 2+ guests under conditions of thermodynamically controlled, statistically averaged exchange. The undistorted host is very tolerant toward inclusion of strongly distorted guests. When acting as host, the distorted ion is more discriminatory toward the undistorted guest. Along with the expectation from the JT theory, structural refinement of seven crystals, including a mixed crystal with composition of [Cu 0.126 Mn 0.874 (H 2 O) 4 (C 7 H 4 NO 3 S) 2 ](H 2 O) 2 , showed that metal-ligand distances are significantly affected by the metal substitution. Inclusion of the JT-active ion results in distortion of the coordination polyhedron by increasing the bond length difference between the two metal-O(water) bonds and also causes shortening of the M-N bond. Due to the rigidness caused by π-conjugation, the overall effect on the endocyclic geometry of the organic ligand is small. The anisotropic distortions around the metal ion are faithfully reflected in the stretching force constants of the coordinated water molecules and thus in the IR spectrum of the mixed crystals.
Journal of Raman Spectroscopy, Jan 18, 2018
This work represents the first complete experimental and theoretical study of the infrared (IR) s... more This work represents the first complete experimental and theoretical study of the infrared (IR) spectra of pharmacolite, Ca(AsO 3 OH)•2H 2 O; vladimirite, Ca 4 (AsO 3 OH)(AsO 4) 2 •4H 2 O; and picropharmacolite, Ca 4 Mg(AsO 3 OH) 2 (AsO 4) 2 •11H 2 O. IR spectra, collected at both room and liquid nitrogen temperature, have shown similar spectral view among minerals in the region of ν 1 to ν 4 modes, surprisingly not involving complexity in vladimirite and picropharmacolite spectral view due to the presence of both AsO 3 OH and AsO 4 units compared to pharmacolite where only AsO 3 OH units appear in the structure. On the other hand, vladimirite and picropharmacolite Raman spectra in the corresponding ν 1 to ν 4 region (955-350 cm −1) exhibit existence of 3 sets of 2 bands (6 in total) completely reflecting the existence of 3 symmetrically nonequivalent AsO 4 groups in the structures of vladimirite and picropharmacolite (of which one is protonated) and only one set of ν 1 to ν 4 bands from the structurally equivalent AsO 3 OH units in the pharmacolite structure. The liquid nitrogen temperature IR spectra enabled to infer important information regarding the OH vibrational bands related to the AsO 3 OH groups and to the water molecules. Essentially, all bands in the vibrational spectra were assigned and correlated with the findings for a plethora of structurally similar complex hydrogen arsenate minerals. To support the tentative assignment of bands in the vibrational spectra, quantum theoretical calculations were performed within the framework of density functional theory. On the basis of theoretical calculations, a few reassignments of bands appearing in the OH stretching region are proposed. X-ray powder diffraction was used to confirm authenticity of the title systems.
The ill. intensities of the bands due to OD stretching vibrations of lIDO molecules increase, as ... more The ill. intensities of the bands due to OD stretching vibrations of lIDO molecules increase, as a mle, with the increasing strength of the hydrogen bonds. One is apt to explain this behaviour in terms of non-statistical substitution of hydrogen with deuterium, the deuterium thus preferring the stronger bonds. It has been shown [I] that this notion fails to explain the intensity differences in the OH stretching region. hl the present paper an Einstein model of a crystal containing two types of hydrogen bond is considered, at a temperature low enough to prohibit creation/existence of phonons in the crystal. The most probable HID distribution is the one leading to minimisation of the Gibbs energy of the crystal. The results of the model show that deuterium atoms, as a mle, prefer weaker hydrogen bonds but in certain cases (two very strong bonds or one extremely weak hydrogen bond) might prefer stronger hydrogen bonds as well.
Related Article: P.Naumov, N.Ishizawa, Jun Wang, L.Pejov, M.Pumera, Sang Cheol Lee|2011|J.Phys.Ch... more Related Article: P.Naumov, N.Ishizawa, Jun Wang, L.Pejov, M.Pumera, Sang Cheol Lee|2011|J.Phys.Chem.A|115|8563|doi:10.1021/jp2040339