The structure of phosphorus-containing dendrimers has been studied by IR spectroscopy and optical... more The structure of phosphorus-containing dendrimers has been studied by IR spectroscopy and optical polarization microscopy. The repeating units of dendrimer molecules are mesogens. This property arises from the conjugation of the aromatic ring and the hydrazone group. An analysis of the IR spectra showed that, with an increase in the generation number, the width of the stretching vibration bands ν(PN) and ν(PO) increases. Difficulties in packing molecules of higher generations cause conformational diversity. The shape of the dendrimer molecules was determined by analyzing the increments of dipole moments. Additionally, the modeling of the stacking of repeating links was performed. The spherical model of molecules does not satisfy the experimental dipole moments of the dendrimers. The flat disk model is more suitable for explaining step changes in dipole moments. The liquid-crystalline ordering of dendrimers under the action of applied pressure was found. With simultaneous heating and...
The IR spectra of p-(3-carboxy-1-adamantyl)thiacalix[4]arene (1) were studied. IR spectra of comp... more The IR spectra of p-(3-carboxy-1-adamantyl)thiacalix[4]arene (1) were studied. IR spectra of compound 1 do not contain bands of free hydroxyl groups. The νOH value at 3377 cm-1 signifies the formation of an intramolecular H-bond along the lower edge of compound 1. It was found that all the studied calixarene derivatives containing adamantylcarboxylic acid fragments on the upper edge form H-bonds between adjacent carboxyl groups. At the top edge of thiacalixarene, carboxyl groups form dimers or cyclic tetramers through intramolecular H-bonds. The conformation of the cone is preserved, but there is a mutual influence of Hbonds along the lower and upper edges of the thiacalixarene molecules. A structure with dimeric H-bonds between carboxyl groups is 1.5 kJ/mol less preferable than the conformation with tetrameric cyclic H-bonds of compound 1. Comparison of the νOH absorption frequency of alcohol hydroxyl groups in IR spectra of thiacalixarenes shows that the presence of the second H-b...
-I "ssumed to bc Gaussian and their half-widths were taken equal to 20 cm In the first s... more -I "ssumed to bc Gaussian and their half-widths were taken equal to 20 cm In the first stage, we carried out optimization of the geometry of the molecules in a system of dependent natural coordinates. According to data obtained by the method of molecular mechanics, the syn-conformation of the chloromelhvl fragment is more stable in I and III while the
The basic difficulty that arises in solving the problem of the frequencies of the vibrations of m... more The basic difficulty that arises in solving the problem of the frequencies of the vibrations of molecules is the selection of the force field. Since TiC-cross-linkin g has a cyclic structure, direct transfer of force constants from molecules of a related structure would be incorrect. At the first stage of the investigation the development of the force field for the frame of the ring was made with lhe help of a simple model of the TIC-ring, i.e., cvanuric acid {CA) IR = H). The geometric parameters of this molecule are known from data of x-ray analysis (4 1. The CA molecule belongs to the point group D3h and has the following types of vibrations: F,i b = 4.41 +3A~+7E'+3.1~'+3E' '. The E'- and A:~'-type vibrations are active in the 1R spectrum and those of types A I and E" in lhe Raman spectrum. To obtain a preliminary evaluation of the force constants of CA, we resorted to methods of quantum chemistry. Using the quantum-chemical method MINDO/3 15 I, we performed calculations of the equilibrium geometry of the molecule, the force constants, and the electrooptical parameters on an ES-1046 computer bv the programs of (6 1. The mean values of the optimized geometric parameters of the molecule did not differ by more than 2% from those obtained experimentally and were equal to: Rex = 0.1350 nm; RCo =0.1215 nm; RNtl = 0.1025 rim; a NCN = 115~ a CNC = 125~ a OCN = 122.5~ a CNH = 117.5 ~ . The calculated force constants were multiplied by the corresponding scaling factors suggested in )7 ) for esters, amides, and carbamates. However, their use for the molecule considered gives overstated values of the force constants of the C-N and C=O bonds, which seems to be
The FT-IR and FT–Raman measurements of 6 generations of phosphorus dendrimers G′ci built from cyc... more The FT-IR and FT–Raman measurements of 6 generations of phosphorus dendrimers G′ci built from cyclotriphosphazene core with phenoxy and deuterophenoxy terminal groups have been performed. Spectra of dendrimers depends on the ratio of end groups and repeated units. This ratio tends to be r – 1 (r – functionality of repeated unit), and becomes constant, when the generation number is above 3. Experimental Raman spectra of generations of dendrimers are very closely similar in accordance with the theory. Structural optimization and normal mode analysis were obtained for G′c1 by the density functional theory (DFT). Calculations have shown that each OC6H4CHNN(CH3) moiety is flat and six repeating units are located above and below the nearly flat cyclotriphosphazene ring. Optimized geometric bond length and angles obtained by DFT show good agreement with the experiment. The phenoxy terminal groups are characterized by the well-defined line at 1008 cm−1 in the experimental Raman spectrum of ...
ABSTRACT Fourier transform IR spectra of the first generation dendrons built from thiophosphoryl ... more ABSTRACT Fourier transform IR spectra of the first generation dendrons built from thiophosphoryl core with terminal PCl groups, vinyl (G1) and azide (G2) functional group at the level of the core have been recorded. The optimized geometries of low energy isomers of G1 and G2 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of each structural part (core, branches, surface). It was found that the repeated branching units of G1 and G2 contain planar OC6H4CHNN(CH3)P fragments. DFT results for the structure of G1 and G2 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G1 and G2. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core functional and terminal groups. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals why azide group linked to phosphorus has a different reactivity when compared to organic azides.
ABSTRACT The Fourier transform IR and Raman spectra of the zero generation dendrimer G1 with two ... more ABSTRACT The Fourier transform IR and Raman spectra of the zero generation dendrimer G1 with two PNPS linkages and four terminal aldehyde groups have been recorded. The optimized geometry of low energy isomer of G1 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of PNPS linkages. DFT results for the structure of G1 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G1. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal group. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals that the softness and electrophilicity of sulfur atom in the core of the dendrimer G1 is higher than that of sulfur atoms and of the dendron G2. Thus PNPS linkage has a high electron density on sulfur which allows the regiospecific complexation of gold, whereas the other PS groups do not react this way. This explains why PN bond in PNPS linkage is much more stable than isolated PN bonds, which are easily hydrolyzed.
Currently used poiyviny[ iodide polarizers have rather inflexible spectral properties, which rest... more Currently used poiyviny[ iodide polarizers have rather inflexible spectral properties, which restricts their possible use in optical instruments. To eliminate this deficiency we have developed polymeric polarizers in which the dichroie substance is a mixture of dichroie dyes. Here we describe a method and present equations whereby the concentration of each component of the mixture of dyes introduced into the polymer film can be calculated, without simulating the system, to get specified transmittanees of the polarizers at the required wavelengths. We have made a polarizer from a mixture of two dyes with the following properties: transmittance T = 40%; at wavelengths Xi = 460, 560, 644 nm-not more than 1.5%. The polarizer is designed for photography of the earth's surface in polarized light.
With the change in the structure of the chains, the infrared spectrum of the polymer shows a decr... more With the change in the structure of the chains, the infrared spectrum of the polymer shows a decrease in the intensity of some of the bands and the appearance of new bands [3-6]. The polarization spectra of PAN fibers subjected to pyrolysis have been recorded, and the in-plane vibrations of structure II have been calculated [7]. Some of the bands in the infrared spectrum of PAN subjected to pyrolysis can be assigned to out-of-plane vibrations, however, and for the interpretation of the spectrum it is necessary to calculate the out-of-plane vibrations of structure II. The bond lengths and angles were taken as equal to those in the pyridine molecule [8]. The factor group of this infinite cyclic chain is isomorphous with the point group C2v. Group-theoretica l analysis shows that the infinite PAN chain has three out-of-plane vibrations of type B1, which are active in the infrared and Raman spectra and have ~r polarization. The frequencies of the vibrations of the infinite chain were calculated by the method described in [9]. The matrices of the kinematic coefficients and force constants were compiled in natural coordinates. Coordinates corresponding to movement of the bonds from the plane, and coordinates of the "butterfly flight" type, were used. These coordinates were proposed for benzene [10], and have been used in the calculation of the frequencies of naphthalene and anthracene [11, 12]. The valence-force field was taken from [12] without modification. This field was previously used successfully to calculate the out-of-plane vibrations of the phenazine molecule, which contains nitrogen atoms [13]. The solution of the secular equation was carried out by means of a computer. The values obtained for the frequencies of the vibrations are given in Table 1. The calculation of the forms of the vibrations shows that the band at 963 cm -I is due to the out-of-plane bending vibrations of the CH groups, the band at 833 cm -i is due to the twisting vibrations about the C - C bond, and to the out-.of-plane bending vibrations of the C - C bonds, andthe band at 449 em -1 is due to the out-of-plane bending vibrations of the C - C bond. Experimental data on the ultraviolet spectra of the products of the pyrolysis of PAN show that the length of the conjugated sections depends on the conditions of pyrolysis. It was therefore of interest to calculate the frequencies of the vibrations of finite chains. The calculation of the frequencies of the vibrations of finite chains was carried out by the method described in [14], in the zeroth approximation. The results of the calculation for N = 5, 10, and 100 (where N is the number of units in the sequence), together with the experimental data, are given in Table 1.
The structure of phosphorus-containing dendrimers has been studied by IR spectroscopy and optical... more The structure of phosphorus-containing dendrimers has been studied by IR spectroscopy and optical polarization microscopy. The repeating units of dendrimer molecules are mesogens. This property arises from the conjugation of the aromatic ring and the hydrazone group. An analysis of the IR spectra showed that, with an increase in the generation number, the width of the stretching vibration bands ν(PN) and ν(PO) increases. Difficulties in packing molecules of higher generations cause conformational diversity. The shape of the dendrimer molecules was determined by analyzing the increments of dipole moments. Additionally, the modeling of the stacking of repeating links was performed. The spherical model of molecules does not satisfy the experimental dipole moments of the dendrimers. The flat disk model is more suitable for explaining step changes in dipole moments. The liquid-crystalline ordering of dendrimers under the action of applied pressure was found. With simultaneous heating and...
The IR spectra of p-(3-carboxy-1-adamantyl)thiacalix[4]arene (1) were studied. IR spectra of comp... more The IR spectra of p-(3-carboxy-1-adamantyl)thiacalix[4]arene (1) were studied. IR spectra of compound 1 do not contain bands of free hydroxyl groups. The νOH value at 3377 cm-1 signifies the formation of an intramolecular H-bond along the lower edge of compound 1. It was found that all the studied calixarene derivatives containing adamantylcarboxylic acid fragments on the upper edge form H-bonds between adjacent carboxyl groups. At the top edge of thiacalixarene, carboxyl groups form dimers or cyclic tetramers through intramolecular H-bonds. The conformation of the cone is preserved, but there is a mutual influence of Hbonds along the lower and upper edges of the thiacalixarene molecules. A structure with dimeric H-bonds between carboxyl groups is 1.5 kJ/mol less preferable than the conformation with tetrameric cyclic H-bonds of compound 1. Comparison of the νOH absorption frequency of alcohol hydroxyl groups in IR spectra of thiacalixarenes shows that the presence of the second H-b...
-I "ssumed to bc Gaussian and their half-widths were taken equal to 20 cm In the first s... more -I "ssumed to bc Gaussian and their half-widths were taken equal to 20 cm In the first stage, we carried out optimization of the geometry of the molecules in a system of dependent natural coordinates. According to data obtained by the method of molecular mechanics, the syn-conformation of the chloromelhvl fragment is more stable in I and III while the
The basic difficulty that arises in solving the problem of the frequencies of the vibrations of m... more The basic difficulty that arises in solving the problem of the frequencies of the vibrations of molecules is the selection of the force field. Since TiC-cross-linkin g has a cyclic structure, direct transfer of force constants from molecules of a related structure would be incorrect. At the first stage of the investigation the development of the force field for the frame of the ring was made with lhe help of a simple model of the TIC-ring, i.e., cvanuric acid {CA) IR = H). The geometric parameters of this molecule are known from data of x-ray analysis (4 1. The CA molecule belongs to the point group D3h and has the following types of vibrations: F,i b = 4.41 +3A~+7E'+3.1~'+3E' '. The E'- and A:~'-type vibrations are active in the 1R spectrum and those of types A I and E" in lhe Raman spectrum. To obtain a preliminary evaluation of the force constants of CA, we resorted to methods of quantum chemistry. Using the quantum-chemical method MINDO/3 15 I, we performed calculations of the equilibrium geometry of the molecule, the force constants, and the electrooptical parameters on an ES-1046 computer bv the programs of (6 1. The mean values of the optimized geometric parameters of the molecule did not differ by more than 2% from those obtained experimentally and were equal to: Rex = 0.1350 nm; RCo =0.1215 nm; RNtl = 0.1025 rim; a NCN = 115~ a CNC = 125~ a OCN = 122.5~ a CNH = 117.5 ~ . The calculated force constants were multiplied by the corresponding scaling factors suggested in )7 ) for esters, amides, and carbamates. However, their use for the molecule considered gives overstated values of the force constants of the C-N and C=O bonds, which seems to be
The FT-IR and FT–Raman measurements of 6 generations of phosphorus dendrimers G′ci built from cyc... more The FT-IR and FT–Raman measurements of 6 generations of phosphorus dendrimers G′ci built from cyclotriphosphazene core with phenoxy and deuterophenoxy terminal groups have been performed. Spectra of dendrimers depends on the ratio of end groups and repeated units. This ratio tends to be r – 1 (r – functionality of repeated unit), and becomes constant, when the generation number is above 3. Experimental Raman spectra of generations of dendrimers are very closely similar in accordance with the theory. Structural optimization and normal mode analysis were obtained for G′c1 by the density functional theory (DFT). Calculations have shown that each OC6H4CHNN(CH3) moiety is flat and six repeating units are located above and below the nearly flat cyclotriphosphazene ring. Optimized geometric bond length and angles obtained by DFT show good agreement with the experiment. The phenoxy terminal groups are characterized by the well-defined line at 1008 cm−1 in the experimental Raman spectrum of ...
ABSTRACT Fourier transform IR spectra of the first generation dendrons built from thiophosphoryl ... more ABSTRACT Fourier transform IR spectra of the first generation dendrons built from thiophosphoryl core with terminal PCl groups, vinyl (G1) and azide (G2) functional group at the level of the core have been recorded. The optimized geometries of low energy isomers of G1 and G2 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of each structural part (core, branches, surface). It was found that the repeated branching units of G1 and G2 contain planar OC6H4CHNN(CH3)P fragments. DFT results for the structure of G1 and G2 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G1 and G2. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core functional and terminal groups. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals why azide group linked to phosphorus has a different reactivity when compared to organic azides.
ABSTRACT The Fourier transform IR and Raman spectra of the zero generation dendrimer G1 with two ... more ABSTRACT The Fourier transform IR and Raman spectra of the zero generation dendrimer G1 with two PNPS linkages and four terminal aldehyde groups have been recorded. The optimized geometry of low energy isomer of G1 have been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. DFT is used for analyzing the properties of PNPS linkages. DFT results for the structure of G1 are in good agreement with X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G1. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core function and terminal group. Natural bond orbital (NBO) analysis has been applied to comparative study of charge delocalization. Our study reveals that the softness and electrophilicity of sulfur atom in the core of the dendrimer G1 is higher than that of sulfur atoms and of the dendron G2. Thus PNPS linkage has a high electron density on sulfur which allows the regiospecific complexation of gold, whereas the other PS groups do not react this way. This explains why PN bond in PNPS linkage is much more stable than isolated PN bonds, which are easily hydrolyzed.
Currently used poiyviny[ iodide polarizers have rather inflexible spectral properties, which rest... more Currently used poiyviny[ iodide polarizers have rather inflexible spectral properties, which restricts their possible use in optical instruments. To eliminate this deficiency we have developed polymeric polarizers in which the dichroie substance is a mixture of dichroie dyes. Here we describe a method and present equations whereby the concentration of each component of the mixture of dyes introduced into the polymer film can be calculated, without simulating the system, to get specified transmittanees of the polarizers at the required wavelengths. We have made a polarizer from a mixture of two dyes with the following properties: transmittance T = 40%; at wavelengths Xi = 460, 560, 644 nm-not more than 1.5%. The polarizer is designed for photography of the earth's surface in polarized light.
With the change in the structure of the chains, the infrared spectrum of the polymer shows a decr... more With the change in the structure of the chains, the infrared spectrum of the polymer shows a decrease in the intensity of some of the bands and the appearance of new bands [3-6]. The polarization spectra of PAN fibers subjected to pyrolysis have been recorded, and the in-plane vibrations of structure II have been calculated [7]. Some of the bands in the infrared spectrum of PAN subjected to pyrolysis can be assigned to out-of-plane vibrations, however, and for the interpretation of the spectrum it is necessary to calculate the out-of-plane vibrations of structure II. The bond lengths and angles were taken as equal to those in the pyridine molecule [8]. The factor group of this infinite cyclic chain is isomorphous with the point group C2v. Group-theoretica l analysis shows that the infinite PAN chain has three out-of-plane vibrations of type B1, which are active in the infrared and Raman spectra and have ~r polarization. The frequencies of the vibrations of the infinite chain were calculated by the method described in [9]. The matrices of the kinematic coefficients and force constants were compiled in natural coordinates. Coordinates corresponding to movement of the bonds from the plane, and coordinates of the "butterfly flight" type, were used. These coordinates were proposed for benzene [10], and have been used in the calculation of the frequencies of naphthalene and anthracene [11, 12]. The valence-force field was taken from [12] without modification. This field was previously used successfully to calculate the out-of-plane vibrations of the phenazine molecule, which contains nitrogen atoms [13]. The solution of the secular equation was carried out by means of a computer. The values obtained for the frequencies of the vibrations are given in Table 1. The calculation of the forms of the vibrations shows that the band at 963 cm -I is due to the out-of-plane bending vibrations of the CH groups, the band at 833 cm -i is due to the twisting vibrations about the C - C bond, and to the out-.of-plane bending vibrations of the C - C bonds, andthe band at 449 em -1 is due to the out-of-plane bending vibrations of the C - C bond. Experimental data on the ultraviolet spectra of the products of the pyrolysis of PAN show that the length of the conjugated sections depends on the conditions of pyrolysis. It was therefore of interest to calculate the frequencies of the vibrations of finite chains. The calculation of the frequencies of the vibrations of finite chains was carried out by the method described in [14], in the zeroth approximation. The results of the calculation for N = 5, 10, and 100 (where N is the number of units in the sequence), together with the experimental data, are given in Table 1.
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