Comparative DFT study of Raman spectra of phosphorus-containing dendrimers built from thiophosphoryl,cyclotriphosphazene and phthalocyanine cores

The FT Raman spectra of the zero and first generations of phosphorus-containing dendrimers built from thiophosphoryl, cyclotriphosphazene and phthalocyanine core with terminal oxybenzaldehyde groups have been recorded and analyzed. The structural optimization and normal mode analysis were performed for dendrimers on the basis of the density functional theory (DFT). The calculated geometrical parameters, harmonic vibrational frequencies and Raman scattering activities are predicted in a good agreement with the experimental data. The experimental Raman spectra of dendrimers were interpreted by means of potential energy distribution. Relying on DFT calculations the lines of the cores, repeating units and terminal groups of dendrimers were assigned.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. The strong line at 1600 cm⁻¹ show marked changes of intensity in dependence of aldehyde (CHO) or azomethyne (CHN) substituents in the aromatic ring. The polarizabilities and lipophilicity of dendrimers were estimated.     

Comparative IR spectroscopic study of phosphorus-containing dendrimers built of thiophosphoryl, cyclophosphazene and phthalocyanine cores

The FTIR spectra of four generations of phosphorus-containing dendrimers built of thiophosphoryl, cyclophosphazene and phthalocyanine cores with terminal benzaldehyde and P–Cl groups have been recorded and analyzed. FT-Raman spectra of four generations of phosphorus dendrimers built of cyclotriphosphazene core with terminal benzaldehyde groups have been detected. Their spectral pattern is determined by the ratio T_n/R_n (T_n—number of terminal groups, R_n—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. Experimental IR spectra of dendrimers built of thiophosphoryl, cyclophosphazene and phthalocyanine cores are very closely similar. The dependence of band full width at half height in IR spectra on the number of dendrons is established. The possibility appears to separate the bands assigned to the core, repeating units and terminal groups of dendrimers by difference spectroscopy method.     

DFT study of the IR and Raman spectra of a fluorescent dendron built from cyclotriphosphazene core

Combined experimental and theoretical studies on molecular structure of the zero generation dendron, built from the hexafunctional cyclotriphosphazene core, with five OC₆H₄(CH₂)₂NHSO₂C₁₀H₆N(CH₃)₂ terminal groups and one oxybenzaldehyde group G₀ are reported. The Fourier transform Raman and IR spectra of G₀ have been recorded. Conformations of low energy isomers of G₀ have been studied at quantum-chemical level. The optimized geometry has been calculated by density functional (DFT) method at the PBE/TZ2P level of theory. The theoretical geometrical parameters, harmonic vibrational frequencies, IR intensities and Raman scattering activities are predicted in a good agreement with the experimental data. It was found that dendron molecule G₀ has a concave lens structure with planar OC₆H₄CHO fragments and slightly non-planar cyclotriphosphazene core. Relying on DFT calculations the bands of the core and terminal groups were assigned. The frequencies of ν(NH) bands in the IR spectrum reveal the presence of the H-bonds in the dendron.     

DFT study and vibrational spectra of the phoshorus-containing G0 generation dendrimer

The Raman (10–3500 cm⁻¹) and infrared (150–3500 cm⁻¹) spectra have been recorded for tris(4-oxibenzaldehyde)thiophosphate. This compound includes structural parts of elementoorganic dendrimers: a core and terminal aldehyde groups. The structural optimization and normal mode analysis are performed for elementoorganic dendrimer on the basis of the ab initio density functional theory. It is found that the dendrimer exist in a single stable conformation with planar C₆H₄CHO fragments. Our calculations show that conformer with one trans and two gauche 4-oxibenzaldehyde groups is realized. All these observations suggest that steric congestion does not disturb the construction of dendrimers even for the highest generations, and that terminal groups are readily available for further reactions. Relying on DFT calculations a complete vibrational assignment is proposed for different parts of the studied dendrimers.     

DFT study and IR spectra of hexaphenoxycyclotriphosphazene generation phosphorus dendrimer

The infrared (150–3500 cm⁻¹) spectra have been recorded for hexaphenoxycyclotriphosphazene [NP(OPh)₂]₃ and all-D isotope specie. These compounds include a cyclotriphosphazene core and terminal phenoxy groups of elementoorganic dendrimers. The structural optimization and normal mode analysis are performed for elementoorganic dendrimer on the basis of the ab initio density functional theory. It is found that the dendrimer exists in a single stable conformation with slightly non-planar cyclotriphosphazene core. Relying on DFT calculations a complete vibrational assignment is proposed for different parts of the studied dendrimers. The softness of sulphur atom in the thiophosphoryl core to nucleophilic attack is higher than the softness of the atoms of the cyclotriphosphazene core. The reactivity of the core is less than that of terminal groups.     

The vibrational spectra of the elementoorganic starburst dendrimers

The main features of vibrational spectra of starburst dendrimers have been analyzed for the first time. Their spectral pattern, in general, is determined by the ratio of a number of terminal groups to a number of repeating units. This ratio tends to m_r−1 (m_r — branching functionality of repeating unit), and becomes constant, when the generation number of the starburst dendrimer increases higher than 3-5. IR and Raman spectra of twelve generations of the phosphorus-containing dendrimers are represented and interpreted on the basis of the calculation of frequencies of the normal vibrations and band intensities in the IR spectra of ‘molecules’ terminated by dangling methyl groups, which are the fragments of the dendrimer molecule. Tailored spectra of these fragments are then compared with experimental spectra and satisfactory similarity has been obtained. Experimental spectra of generations higher than 4 are very similar, according to the theoretical approach. The results can be used for the analysis of the chemical and physical transformations in starburst dendrimers.     

Synthesis of phosphorus-containing polyoxamacrocycles with one to two reactive thiophosphoryl chloride groups

Novel phosphorus-containing polyoxamacrocycles with one to two reactive thiophosphoryl chloride groups 5, 6, 7, 8 were synthesized from bishydroxyl compounds 1, 2, 3, 4 and thiophosphoryl chloride respectively. Their structures were confirmed by ^ 1H NMR, ^13C NMR, ^31p NMR and elemental analysis.     

Synthesis of phosphorus-containing polyoxamacrocycles with one to two reactive thiophosphoryl chloride groups

Novel phosphorus-containing polyoxamacrocycles with one to two reactive thiophosphoryl chloride groups 5,6,7,8 were synthesized from bishydroxyl compounds 1,2,3,4 and thiophosphoryl chloride respectively.Their structures were confirmed by ~1H NMR,~(13)C NMR,~(31)p NMR and elemental analysis.     

Surface, core, and structure modifications of phosphorus-containing dendrimers. Influence on the thermal stability

Three new series of phosphorus-containing dendrimers are described. Their solubility depends on the type of end groups they bear. Perfluoroalkyl chains give dendrimers soluble in chlorofluorocarbons, whereas guanidinium and pyridinium derivatives give water-soluble compounds. The thermal stability of these compounds, as well as of 19 other dendrimers of various generations, having various cores, or various end groups, or branching points is studied. The main feature of this study is that the internal structure of these dendrimers is thermally stable at least up to 376°C. The number of the generation has practically no influence, whereas the principal criterion influencing the thermal stability is the type of end groups. The water-soluble cationic dendrimers are the least stable, but even those are stable up to 225°C. For most of these dendrimers, an important percentage of mass (around 50%) is retained even at a temperature as high as 1000°C. In the best case, up to 70% of the initial mass is retained at 1000°C.     

Vibrational spectra study of fluorescent dendrimers built from the cyclotriphosphazene core with terminal dansyl and carbamate groups

The FTIR and FT Raman spectra of the "Janus"-type dendrimers, possessing five carbamate groups on one side and five fluorescent dansyl derivatives on the other side, with amide G(1) and hydrazone G(2) central linkages were studied. These surface-block dendrimers are obtained by the coupling of two different dendrons. The FTIR and FT-Raman spectra of the zero generation dendrons, built from the hexafunctional cyclotriphosphazene core, with five dansyl terminal groups and one carbamate G(0v) and one oxybenzaldehyde function G(0v)' have been recorded. The structural optimization and normal mode analysis were performed for dendron G(0v)' on the basis of the density functional theory (DFT). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that dendron molecule G(0v)' has a concave lens structure with planar -O-C(6)H(4)-CHO fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of dendron G(0v)' were interpreted by means of potential energy distributions. 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 the dendrimers.     

羧基为核收敛的多醚树枝状大分子的红外与拉曼光谱分析

根据文献合成了第一、第二和第三代羧基为核收敛的多醚树枝状大分子(缩写为G1、G2和G3)。利用振动光谱数据,结合X-衍射结构分析,从G1的结构推想出G2和G3的可能结构。以2,5二甲基苯基醚作为模型分子,把复杂分子拆成组成结构进行光谱分析,从而对产物G1、G2和G3的谱带作了初步归属。     

Dendrimers with a cyclam core. Absorption spectra, multiple luminescence, and effect of protonation

We have synthesized two dendrimers (4 and 5) consisting of a 1,4,8,11-tetraazacyclotetradecane (cyclam) core appended with four dimethoxybenzene and eight naphthyl units (4) and 12 dimethoxybenzene and 16 naphthyl units (5). The absorption and luminescence spectra of these compounds and the changes taking place upon protonation of their cyclam core have been investigated. In acetonitrile-dichloromethane 1:1 v/v solution they exhibit three types of emission bands, assigned to naphthyl localized excited states (λ_max=337 nm), naphthyl excimers (λ_max ca 390 nm), and naphthyl-amine exciplexes (λ_max=480 nm). The tetraamine cyclam core undergoes only two protonation reactions, whose constants have been obtained by fitting the spectral changes. Protonation not only prevents exciplex formation for electronic reasons, but also causes strong nuclear rearrangements in the cyclam structure which affect excimer formation between the peripheral naphthyl units of the dendrimers.     

Temperature study of Raman, FT-IR and photoluminescence spectra of ZnPc thin layers on Si substrate

The temperature study of zinc phthalocyanine (ZnPc) thin layers deposited on (0 0 1) Si substrate using Raman, FT-IR absorption and photoluminescence (PL) methods are reported. The Raman scattering spectra of ZnPc layers were investigated in the spectral range 1250–1650 cm⁻¹ and in the temperature range 100–500 K. The changes of spectral parameters such as the band position, integrated intensity and full width at half maximum (FWHM) of selected Raman modes while heating and cooling processes have been determined. The fast decrease of the frequency and the intensity of these modes observed with the increase of the temperature above 420 K, can be probably caused by the change of crystalline form of ZnPc thin layer. The FT-IR measurements have been performed in the temperature range 98–523 K. Our study allowed us to estimate the orientation of the molecular plane similar to these of CuPc thin films deposited on Si substrate. The Raman spectra have been compared with FT-IR spectra of ZnPc molecules in KBr pellets and thin layers of ZnPc on (0 0 1) Si substrate. The PL spectra of ZnPc layers were measured in the spectral range 350–1200 nm and in the temperature range 13–320 K. With increasing temperature from 13 to 175 K we observed the increase of PL bands at 1.76 and 1.85 eV which disappear reaching temperature above 200 K.     

Long-wave Raman spectra of some normal alcohols

Long-wave Raman spectra of some normal alcohols (from n-pentanol to n-decanol) in the liquid phase were registered. The regularities in the dependencies of Raman bands frequencies on the number of carbon atoms in the hydrocarbon chain were deduced. The calculations of Raman spectra of the studied molecules, their equilibrium structures and possible conformers were carried out in the approximation B3LYP/cc-pVDZ. These results in combination with the analysis of literature data allowed to explain the observed regularities in Raman band positions in the spectral range of 200–600 сm⁻¹ and their shifts upon increasing length of the chains. It was found that the plane configurations dominate in the liquid phase for molecules with short- and moderate-chain lengths. The elongation of the chain leads to the decrease of the fraction of plane conformers and in n-decanol the plane structure is completely absent.     

Simulation of the Raman spectra of zwitterionic glycine + nH2O (n = 1, 2, …, 5) by means of DFT calculations and comparison to the experimentally observed Raman spectra of glycine in aqueous medium

Raman spectra of an aqueous solution of glycine (Gly) have been recorded in the range of 400-2000 cm⁻¹. In aqueous solution, glycine molecules exist in their zwitterionic form, having two opposite charged poles, COO⁻ and NH₃⁺. The zwitterionic structure of glycine (ZGly) is stabilized by the hydrogen bond interaction of water (W) molecules. In the present report, we have optimized the ground state geometries of different hydrogen bonded complexes of [ZGly + (W)_n=1-5] in aqueous medium using DFT calculations at the B3LYP/6-311++G(d) level of theory. A comparative discussion on the structural details and binding energies (BEs) of each conformer has been also done. The theoretical Raman spectra were calculated corresponding to the most stable [ZGly + (W)_n=1-5] conformers. The theoretically simulated Raman spectra of each stable conformer were compared with experimentally observed Raman spectra to explore the number of water molecules needed for stabilizing the structure of ZGly. The theoretically simulated Raman spectra corresponding to the most stable conformer of [ZGly + (W)₅] having a BE of −22.8 kcal/mol, are matching nicely with the experimentally observed Raman spectra. Thus, on the basis of the above observations, we conclude that the conformer, [ZGly + (W)₅] is the most probable conformer in the aqueous medium. We also believe that in the conformer, [ZGly + (W)₅] the five water molecules are arranged around the ZGly in such a way that the effect of steric hindrance is less compared to the other conformers. The dipole-dipole interaction potential (DDP) is also calculated corresponding to the strongest hydrogen bond for each [ZGly + (W)_n=1-5] conformer.     

Boson peak in the low-frequency Raman spectra of an ordinary liquid

Polarised and depolarised low-frequency Raman spectra of liquid formamide have been analysed. The employed fitting procedure shows convincingly that the Boson peak contribution to the overall low-frequency Raman pattern is present even in this ordinary, low-viscous liquid.     

Infrared and Raman spectra of 2,4-dimethylaniline

The infrared spectra of 2,4 dimethylaniline have been recorded in the region 3600-100 cm⁻¹. The Raman spectra with polarization measurements have been recorded and investigated for the first time in the region 3500-100 cm⁻¹. New frequency assignments have been proposed assuming the molecule to possess an approximateC ₂ symmetry. Fifty normal modes of the molecule, out of a possible fifty four modes, have actually been observed and assigned including twenty seven hitherto unreported frequencies. The observed spectral changes give evidence of the presence of an intermolecular hydrogen bonding of an N−H...N type, and suggest a solid-solid phase transition between 223 and 123 K in the molecule.     

Fourier-transform infrared and Raman difference spectroscopy studies of the phosphorus-containing dendrimers

FT IR and Raman spectra of 12 generations of the phosphorus-containing starburst dendrimers containing P=S and P=O bonds with terminal aldehyde and P-Cl groups were compared. The influence of the encirclement on the band frequencies and intensity is studied and due to the predictable, controlled and reproducible structure of the dendrimers the information usually inaccessible is obtained. Bands in the IR difference (G2'(P=O)-G2'(P=S)) spectra have characteristic EPR-like form. The strong band at 1600 cm(-1) show marked changes of the optical density in dependence of the aldehyde (-CH=O) or azomethyne (-CH=N-) substituents in the aromatic ring. The analysis of difference spectra enables one to assign the characteristic bands nu(P=S) and nu(P=O) for the bonds in the core, in the repeating unit and in the terminal groups of the dendrimers. This assignment is supported by the calculation of the absorption curves of the different fragments of dendrimer with the force constants and electro-optical parameters. The IR and Raman spectra of dendrimers are depended on the ratio of number terminal groups to a number of repeating units, which in its turn is strictly determined by the generation number. Thus, the marked differences in the vibrational spectra of the first successive generations aspire to zero for the higher ones. The rather rigid repeated units with little conformational flexibility define the perfect microstructure of the studied phosphorus-containing dendrimers up to the eleventh generation.     

Raman spectra of Sr3(PO4)2 and Ba3(PO4)2 orthophosphates at various temperatures

The Raman spectra for Sr₃(PO₄)₂ and Ba₃(PO₄)₂ were investigated in the temperature range from 80 to 1623 K at atmospheric pressure. An unexpected melting of each sample was observed around 1573–1583 K in this study. In the temperature range from 80 to 1323 K, the Raman wavenumbers of all observed bands for Sr₃(PO₄)₂ and Ba₃(PO₄)₂ continuously decrease with increasing temperature. A quantitative analysis on the wavenumbers of Raman bands for both samples reveals that the ν₃ antisymmetric stretching vibrations show the strongest temperature dependence and the ν₂ symmetric bending vibration displays the weakest temperature dependence. The effects of cations on Raman bands are discussed. The reason for the unexpected melting of both samples is mainly attributed to the significant contribution from excess surface energy and the grain-boundary energy that has apparently lowered the melting points of the small samples, i.e., Gibbs–Thomson effect.     

Raman scattering spectra and molecular conformations of bis(quaternaryammonium bromide)-water systems

The dimeric bis(quaternaryammonium bromide) surfactants, [Br⁻(CH₃)₂N⁺(C _m H_{2 m +1})—(CH₂) _s —(C _m H_{2 m +1})N⁺(CH₃)₂Br⁻, s = 2, 3 and m = 4, 6, 10 and 12, s = 6 and m = 8, 10, 12], have been synthesized and the phase maps of the sm6-8-water, sm6-10-water and sm6-12-water binary systems have been determined (sm6-8 implies s = 6, m = 8). In order to examine the molecular structures of these solid samples and of their dimeric surfactant-water binary systems, Raman spectra of the simple dimeric surfactants, sm2-4 and sm3-4, in which crystal structures of the trans- and cis-type conformations have been determined by single-crystal X-ray diffraction analysis, have been investigated, and Raman bands characteristic of these skeletal structures were found in the skeletal deformation region. On the basis of these characteristic Raman bands for the two conformations, it has been concluded that the dimeric surfactants, sm6-8, sm6-10 and sm6-12 also take up a cis-type conformation in the crystalline state. Furthermore, it has been found that the Raman bands in the C—H stretching, skeletal stretching and CH₂ scissoring regions are sensitive to phase structure. Received: 21 July 1998 Accepted in revised form: 9 November 1998