DFT calculation of molecular structure and vibrational spectra of the phosphorus-containing G1′ generation dendrimer with terminal aldehyde groups

Chemical Physics 326 (2006) 417–424 www.elsevier.com/locate/chemphys

DFT calculation of molecular structure and vibrational spectra of the phosphorus-containing G01 generation dendrimer with terminal aldehyde groups V.L. Furer b

a,*

, A.E. Vandyukov b, J.P. Majoral c, A.M. Caminade c, V.I. Kovalenko

b,1

a Kazan State Architect and Civil Engineering University, Zelenaya, 1, Kazan 420043, Tatarstan, Russia A.E. Arbuzov Institute of Organic and Physical Chemistry, Russian Academy of Science, Arbuzov Street, 8, 420088 Kazan, Russia c Laboratorie de Chimie de Coordination, CNRS, 205 route de Narbonne, 31077 Toulouse Cedex 4, France

Received 27 January 2006; accepted 2 March 2006 Available online 9 March 2006

Abstract The Raman and infrared spectra of the first generation of the phosphorus-containing dendrimer with terminal aldehyde groups have been recorded. The structural optimization and normal mode analysis are performed for phosphorus-containing dendrimer on the basis of the ab initio density functional theory. This calculations gave vibrational frequencies and infrared intensities for the t,g,g- and t,-g,gconformers of the terminal groups. The t,g,g-conformer is 0.34 kcal/mol less stable compared to t,-g,g-conformer. It is found that the repeated units of dendrimer exists in a single stable conformation with planar AOAC6H4ACH@NAN(CH3)AP fragments. 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 dendrimer. Our study reveals that in the G01 and G1 dendrimers the most reactive are the terminal groups. IR spectroscopy combined with ab initio DFT computation provides unique detailed information about the structure of the technologically relevant materials, which could not be obtained before with any other technique. Ó 2006 Elsevier B.V. All rights reserved. Keywords: Phosphorus-containing dendrimers; IR spectra; Normal vibrations; DFT

1. Introduction Dendrimers represent a unique class of molecules with a regular branched structure [1,2]. Molecules of dendrimers have mainly three-dimensional structure proceeded from one centre – the core with exponentially increasing number of repeated units and end groups [1,2]. Such compounds are perspective materials for the coordination chemistry, agrochemistry, catalyze, the storage and delivery of drugs [1,2]. Phosphorus-containing dendrimers benefit from the *

Corresponding author. Tel.: +7 843 2104737; fax: +7 843 2387972. E-mail addresses: [email protected] (V.L. Furer), [email protected] (V.I. Kovalenko). 1 Tel.: +7 843 2732283; fax: +7 843 2732253. 0301-0104/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.chemphys.2006.03.004

global interest in dendrimers, but they have also their own specificities and properties [3]. The highest generation obtained up to now in dendrimer chemistry, one of the most rapid methods of synthesis of dendrimers, and the most environment-friendly method, relate to phosphoruscontaining dendrimers [3]. Phosphorus-containing dendrimers share several properties with other types of dendrimers, for instance concerning catalysis, creation of new materials, modification of surfaces of materials, or transfection experiments [4–6]. However, they have also properties never reported up to now for other dendrimers, such as a high dipole moment value and the ability to form hydrogels even at low concentrations in water [7]. Such compounds having a hydrophobic interior and hydrophilic surface should have valuable properties [7].

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However, there are still only few structural studies of dendrimers. The difficulties of applying the traditional arsenal of physical chemistry and structural methods for linear polymers are well known. Such a situation exists in the field of the vibrational spectroscopy of the dendrimers as well in spite of the obvious success of this method in the structural investigations of polymers. IR spectra of dendrimers up to now were used only for the analytical purposes. Only Raman spectra of the poly(amidoamine) dendrimers were published [8]. We recently reported the preparation and IR and Raman spectra of phosphorus-containing dendrimers built up to the 12th generation with terminal aldehyde and P–Cl groups [9–12]. The 12 generations of the one series were used to study the connection between the peculiarities of the structure of this type of compounds and its vibrational spectra. IR and Raman spectra of phosphorus-containing dendrimers were interpreted. In that preliminary study, the calculations were based on the semi empirical model of harmonic vibrations of molecular nuclei and on the valence-optical theory of IR spectra. Force constants and electro-optical parameters were transferred from the related compounds and were used for calculation of all generations. There are only a few density functional theory (DFT) studies of structure and spectra of low-generation dendrimers [13,14]. Analysis of IR spectra of dendrimers combined with DFT calculations is important for investigation of supramolecular properties of phosphorus-organic dendrimers as containers for different guest molecules. It enables to reveal the active sites of the dendrimer molecules for nucleophilic and electrophilic attack. The calculated electronic density spatial distribution reveals the existence of regions where appropriate environments would attract either an ion or a metal atom. The interpretation of IR spectra of non-crystalline dendrimers of higher generation is important for characterization their structure. The rather rigid repeating unit, having small conformational flexibility, defines the perfect microstructure of the studied elementoorganic dendrimers up to the 11th generation. The experimental bandwidths in the IR and Raman spectra will be applied to study conformational dynamics of the elementoorganic dendrimers. The dependence of band broadening in the vibrational spectra on the generation number is established. The analysis of spectra enables one to characteristic local flexibility of the repeating units and the terminal groups of the dendrimers. According to our study, the disc-like shape of molecules allows the uniform dendron arrangement, which has no appreciable spatial hindrances up to very high generations, 11th one e.g., and terminal groups of dendrimer molecules are available for further reactions. In this work our aim is to combine experimental results with ab initio quantum chemical calculations, to interpret IR and Raman spectra of the first generation of the phosphorus-containing dendrimer with terminal aldehyde groups (G01 ). During full optimization we were able to find

Me S P

CH

O

N

N

P

O

CHO

2

3

S

Fig. 1. The structure of dendrimer G01 .

local minimum conformers of the G01 molecule and its IR spectra using DFT techniques. The values of calculated geometric parameters were compared with precise molecular structure derived by the X-ray analysis [11]. Thus the main aim of this work was to obtain the characteristic spectral features of structural parts of dendrimer: a core, a repeated unit and terminal aldehyde groups based on ab initio quantum chemical analysis. The global and local reactivity descriptors have been used to characterize the reactivity pattern of the core, the repeated units and the terminal groups. The results that emerge from such an analysis contribute to understanding of the structure, dynamics and properties of dendrimers. 2. Experimental The synthesis and main characteristics of the studied phosphorus-containing dendrimer were described earlier [8–11]. The molecular structure of the dendrimer is the following: the trifunctional core S@PA(AOA)3, the bifunctional repeating unit AOAC6H4ACH@NAN(CH3) AP(S)— and the terminal groups are the 4-oxybenzaldehyde fragments –O–C6H4–CHO (Fig. 1). IR spectra in the region 3500–150 cm1 were recorded on an IFS-113v Bruker FTIR-spectrophotometer with a 4 cm1 resolution. The Raman spectra in the region 3500–10 cm1 were excited by Nd:YAG laser line 1064 nm with power at sample 300 mW and registered by an FRA 106/S Bruker FT-Raman spectrometer with a 4 cm1 resolution. 3. Computational method Calculations of IR and Raman spectra were carried out using the gradient-correlated density functional theory with Perdew–Burke–Ernzerhof exchange-correlation functional (DFT/PBE) [15]. This functional is very satisfactory from the theoretical point of view, because it verifies many of the exact conditions for the exchange-correlation hole and it does not contain any fitting parameters [16]. The calculated with PBE functional binding energies, geometries and dynamical properties of different molecules show the best agreement with experiment [17,18]. Calculations were performed using three exponential basis with two polarizing functions (TZ2P) [19]. This basis set was chosen in order to obtain the most advantageous relation of accuracy and computation time [19]. Its peculiarity is that the same set of exponents is used for all values of angle moment in atom [19]. The program PRIRODA was used to perform DFT calculations [19]. All stationary points were charac-

V.L. Furer et al. / Chemical Physics 326 (2006) 417–424

terized as minima by analysis of Hessian matrices. The software package SHRINK [20] was used for transformation of quantum mechanical Cartesian force constants to the matrix in redundant internal coordinates and calculation of potential energy distribution. No scaling procedure of frequencies or force constant was applied. Recently we checked the selected functional and basis set by calculation of geometry and IR spectra of dendrimers [21,22]. The minima of the potential surface were found by relaxing the geometric parameters with standard optimization methods. IR spectra were generated from a list of frequencies and intensities using Gaussian band shape and half-width r of 10 cm1 for each of N vibration modes calculated. The intensity of each band is Ak in km/mol. ( ) 2 N X Ak ðm  m0 Þ pffiffiffiffiffiffi exp  IðmÞ ¼ 2r2 2pr k An assignment of bands was fulfilled on the basis of calculated potential energy distribution (PED). The electronic chemical potential, the chemical hardness and softness were obtained from the expressions l   (IP + EA)/2, g  (IP  EA) and S = 1/2g, in terms of the first vertical ionization energy IP and electron affinity EA, respectively [22]. The Fukui functions fkþ ðrÞ ¼ ½qk ðN þ 1Þ  qk ðN Þ for nucleophilic attack, and fk ðrÞ ¼ ½qk ðN Þ  qk ðN  1Þ for electrophilic attack, where qk is the electronic population of atom k in the molecule, N the number of electrons, were calculated. The local softness is obtained by projecting the global quantity onto any atomic centre k in the molecule by using the Fukui funcþ   tion: sþ k ¼ Sf k ; sk ¼ Sf k . The Fukui function and local softness for each reactive atom were calculated using Hirshfeld population analysis [23]. 4. Results and discussion The X-ray diffraction experimental data of G01 are absent. But we can use the geometric parameters of G00 dendrimer of the zero generation with terminal aldehyde groups and G1 dendrimer of the first generation with terminal PCl2 groups in crystalline state defined by the X-ray diffraction method [9]. The molecule G1 as a whole looks like a three blade propeller when examined in the direction of terminal P@S groups and each AOAC6H4ACH@NAN(CH3)AP arm is planar. In the molecule G00 the AOAC6H4ACH@O fragment is planar. Thus, the G01 molecular conformation is defined by the dihedral angles SPOC and POCC which determine the orientation of terminal groups. As it follows from the X-ray data the core dihedral angles SPOC of G00 are equal to 0.9°, 32.8° and 67.4°. The experimental dihedral angles POCC of terminal groups are equal to 85.4°, 68.5° and 102.9°. Full optimization yielded the t,g,g-conformer of terminal groups of the G01 with SPOC dihedral angles: 50.8°, 56.1°, and the dihedral angles POCC: 94.0°, 92.5°

419

(Fig. 2). Another energy minima was found for the t,g,-gconformer of G01 the with SPOC dihedral angles: 53.6°, 59.5°, and the dihedral angles POCC: 88.0°, 101.7° (Fig. 2). The t,g,g-conformer is 0.34 kcal/mol less stable compared to t,g,-g-conformer. The calculated bond dis˚ ) 1.926 (S@P(O3)), 1.641 (P–O), 1.398 (C–O), tances (A 1.936 (S@P(O2)), 1.707 (P–N), 1.368 (N–N), 1.462 (C–N), 1.295 (C@N), 1.221 (C@O) for the t,g,-g-conformer correspond well to the experimental values 1.877, 1.578, 1.404, 1.888, 1.624, 1.402, 1.438, 1.270, 1.204 (Table 1). The theoretical bond angles (°) 119.2 (SPO), 98.6 (OPO), 124.3 (POC), 119.7 (CNN), 114.3 (PNN), 125.0 (OCC), 114.9 (SPN), 122.6 (PNC) are also in close agreement with the experimental values 117.8, 100.0, 130.8, 119.2, 112.7, 123.4, 115.4, 125.6 (Table 1). Thus experimental and theoretical data 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. The concept of using dendrimers as new types of carries of active substances was propound until the very beginning of the research in the field of dendrimers chemistry [1–3]. In order to evaluate the interactions between dendrimers and various active substances such as drugs, pesticides, perfumes etc., we calculated electronic density spatial distribution for the core and terminal groups. From our calculations it follows that the studied phosphorus-containing dendrimers incorporate P@S polar bonds in the core and in the terminal groups with Hirshfeld atomic charges (in e) on atoms S (0.22) and P (0.43). The O(–C) and O(@C) atoms of the terminal group have charges 0.14 and 0.22, respectively. Other atoms of repeated unit and terminal groups have charges less than 0.1. Thus in the case of the phosphorus dendrimers we synthesize, macromolecules have a hydrophobic interior, surrounded by oxybenzaldehyde end groups, which are also hydrophobic. Such dendrimers are soluble in a variety of organic solvents, but not in water. Several ways to have water-soluble dendrimers by modifying their end groups were described [3]. The water solubility is obtained when substituents bearing charges, either positive or negative are located on the surface [7]. In contrast to most water-soluble dendrimers, which possess both hydrophilic interior and hydrophilic surface, these phosphorus-containing dendrimers have a hydrophobic interior [3]. One original property of studied dendrimers is their high dipole moment value, due to the presence of thiophosphoryl groups. An exponential increase is observed with increasing generations, up to 328 D for generation 11 [9]. This is the highest value reported up to now for a dendrimer, despite the enormous compensation of the elemental vectors constituting the global dipole moment due to the almost spherical structure of these compounds. The calculated in gas phase dipole moments 1.46 and 4.43 D for the t,g,g- and t,-g,g-conformers of the terminal groups for G01 are less than the experimental value of 8.27 D for dioxane solutions [9].

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Fig. 2. The t,g,g- (a) and t,-g,g-conformers (b) of dendrimer G01 .

For large molecules, prediction of frequencies and intensities from quantum chemistry calculations in the region below 1700 cm1 is extremely important. The experimental and calculated IR and Raman spectra of G01 are represented at Figs. 3 and 4 and in Table 2. The strong band in the IR and Raman spectra at 1702 cm1 is obviously assigned to C@O stretching vibrations of the carbonyl group. The intense bands at 1598, 1502 cm1 in the IR spectra and the lines at 1601, 1504 cm1 of the Raman spectra refer to the CCar stretch and CCH bending vibrations of para-substituted aromatic ring. The band at 1576 cm1 with medium intensity in the Raman spectra and a weak shoulder at 1586 cm1in the IR spectra of the G01 may be assigned to

the m(C@N) vibrations of the hydrazone fragment ˜C@N– N— mixed with stretching vibrations of aromatic ring. The weak bands at 1444, 1468 cm1 in the IR and Raman spectra of the G01 refer to the symmetric deformation vibrations of the CH3 groups. The rather weak bands at 1420, 1407 cm1 and lines at 1419, 1408 cm1 in the Raman spectra correspond to CCar stretch and CCH bending vibrations of aromatic ring. The weak bands at 1302, 1294, 1287, 1248 cm1 and lines at 1303, 1294 cm1 in the Raman spectra are due to CCH bending vibrations of aromatic ring. The very strong band in the experimental IR spectra of G01 at 1207 cm1 is connected mainly with C–O stretch. The intense in the IR spectra band at 1189 cm1 is assigned to

V.L. Furer et al. / Chemical Physics 326 (2006) 417–424

The strong band at 966 cm1 in the IR spectra and the weak line at 962 cm1 in the Raman spectra may be assigned to CH out-of-plane bend. The intense in the IR spectra band at 936 cm1 is connected with the stretching of the P–O and C–O bonds. The very intense band in the IR spectra at 915 cm1 is due to P–N and N–N stretch. The medium-intensity double bands at 851, 835 cm1 in the IR spectra and lines at 851, 832 cm1 in the Raman spectra at 851 cm1 refer to the out-of-plane CH bending vibrations of aromatic ring. A weak band at 759 cm1 in the IR spectra and line at 766 cm1 in the Raman spectra include the stretching vibrations of C–O, P@S and P–O bonds. The bands in the region 100–500 cm1 are connected with bending vibrations of the molecule skeleton. The bands assigned to the core, repeated units and terminal groups of dendrimer may be separated by the DFT method. The core S@P–(O–)3, reveal itself by line at 657 cm1 of the P@S stretch. The repeated unit show line at 1576 cm1 assigned to m(C@N) vibrations of fragment ˜C@NAN—. The 4-oxibenzaldehyde terminal groups are characterized by the line at 1702 cm1 assigned to the C@O stretching vibrations. The intensity of the most prominent bands in the IR spectra of the G01 is reproduced by our calculations. The calculated absorption curve of the G01 as a hole corresponds to the experimental IR spectra in the wide frequency region

Table 1 ˚ ) and bond angles (°) of G0 Experimental and calculated bond distances (A 1 Exp. [9]

Calculation t,g,g-conformation

Bond distances S@P(O3) PAO CAO S@P(O2) PAN CAN CAN C@N C@O Angles SPO OPO POC CNN PNN OCC SPN PNC

1.877 1.578 1.404 1.888 1.624 1.402 1.438 1.270 1.204 117.8 100.0 130.8 119.2 112.7 123.4 115.4 125.6

1.926 1.641 1.398 1.936 1.707 1.368 1.462 1.295 1.221

t,g-g-conformation 1.929 1.639 1.406 1.935 1.709 1.366 1.462 1.295 1.221

119.3 98.6 124.3 119.7 114.3 125.0 114.9 122.6

421

118.5 99.2 120.7 119.9 114.5 125.0 114.9 122.4

C–C stretch. The bands at 1155, 1099, 1014 cm1 in the experimental IR spectra and the lines at 1163, 1101, 1014 cm1 in the Raman spectra were assigned to CCH bend and CCar stretch.

ν (P -O ) ν (P -N )

ν (C -O )

δ (CC H )

ν (C C ) ar

ν (C C ) ar

ν (C =0)

ρ (CH )

c

Extinction

ν (P =S )

b

a

400

600

800

1000

1200

1400

1600

1800

-1

Wavenumber / cm

Fig. 3. Theoretical spectra of t,-g,g-conformer (a), t,g,g-conformer (b), and experimental IR spectra of dendrimer G01 (c).

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ν (C C )

Raman Intensity / arb. units

ar

ν (C =N )

δ (CC H )

ν (C -O ) ν (C =0)

ν (P =S )

0

200

400

600

800

1000

1200

1400

1600

1800

Wavenumber / cm-1 Fig. 4. Experimental Raman spectra of dendrimer G01 .

(Fig. 3). Thus DFT method may be used for interpretation of dendrimer spectra. The functional groups define the chemical properties of dendrimers. That is why it was interesting to clear up the changes in the IR spectra for the t,g,g- and t,-g,g-conformers as compared with experimental spectra of G01 (Fig. 3). The bands characteristic for each conformation are defined and assigned. The calculated band positions of the t,g,gand t,-g,g-conformers are very close to each other and may reveal itself as conformational splitting in the experimental IR spectra. The intensity of the band at 1203 cm1 due to t,-g,g-conformer increases relative to that of t,g,g-conformer. The behaviour in the PO stretching regions at 899 and 869 cm1 also shows the change in the intensity of bands due the rotational isomerism. The absorption curve of t,g,g-conformer better reproduce the experimental spectra in this region (Fig. 3). The most widely studied property of phosphoruscontaining dendrimers is catalysis. The presence of tricoordinated phosphorus atoms, generally on the surface, allows the complexation of various organometallic derivatives having catalytic properties [3]. Dendritic catalysts are believed to combine the advantages of homogeneous catalysts, since they are soluble, and the advantages of heterogeneous catalysts since they should be easily recovered and reused, thank to their large size [3]. Many experiments have

been conducted, with various types of dendrimers having phosphorus either at the branching points and the surface, or only on the surface, or at the core [3]. In some cases, the catalytic properties were increased, in other cases decreased, compared to monomeric complexes possessing an analogous structure [3]. The reactivity of the end groups of these dendrimers is amongst the most versatile and the most widely studied [3]. A huge number of reactions on the P(S)Cl2 and aldehyde end groups of the studied dendrimes have been carried out [3]. For instance, dendrimers having three or even four different types of end groups simultaneously have been described, for the first time [3]. This very special and so far unique type of functionalization was called ‘‘multiplurifunctionalization’’ [3]. In this work we try to characterize the reactivity of dendrimers G1 and G01 with the P(S)Cl2 and aldehyde end groups by means of global and local reactivity descriptors (Table 3). The ionization energy IE and electron affinity EA, the global softness and reactivity of dendrimers G01 and G1 are very similar. The local softness of the G1 and G01 are quite different. The softness of sulphur atom in the core to nucleophilic attack ðs k Þ increases in G1 as compared with G01 . We found that the softness values of sulphur atom of the terminal S@PCl2 group in the G1 is higher, than softness of carbonyl oxygen of aldehyde end group in the G01 . The most reactive place is

V.L. Furer et al. / Chemical Physics 326 (2006) 417–424

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Table 2 Experimental and corresponded calculated frequencies m (cm1) and intensity I (km/mol) of bands in the IR spectra of G01 in the region 200–1800 cm1 Exp.

Calculation

IR

Raman

t,g,g-conformation

m

m

m

I

m

I

1702

1702 1601

1701 1602 1595 1585 1583 1490 1463 1442 1412 1411 1387 1376 1293 1292 1291 1230 1227 1205 1189 1156 1141 1100 1014 1014 988 950 944 910 890 886 840 836 791 769 763 731 720 712 702 645 640 621 600 579 570 554 544 513 494 486 458 455 416 400 332 324 305 285 265 244 226 211

358.3 126.7 112.5 1.2 8.3 206.2 44.5 6.9 15.0 15.3 14.5 4.5 13.2 11.7 10.8 9.3 121.9 90.8 80.7 18.8 179.7 20.5 4.9 3.1 2.4 6.8 434.2 93.2 634.6 198.8 62.9 103.6 3.0 446.6 40.2 29.0 157.6 7.5 64.7 47.4 0.0 59.8 16.7 15.4 22.4 26.1 5.1 18.6 26.8 0.6 155.9 9.4 0.0 0.4 2.4 3.0 0.4 11.7 10.6 0.9 5.2 9.7

1702 1601 1595 1585 1582 1488 1462 1434 1412 1410 1387 1376 1287 1286 1284 1228 1224 1203 1192 1150 1140 1097 1015 1014 989 948 946 901 899 882 843 833 795 768 764 730 721 712 701 645 636 623 599 580 571 558 552 509 484 479 457 450 418 401 343 340 310 288 263 233 224 216

405.1 83.3 135.5 2.5 1.8 156.6 67.6 6.2 15.3 1.7 16.8 3.4 6.4 11.6 12.3 57.5 122.5 124.1 30.4 14.7 195.9 2.9 4.4 7.4 2.8 5.9 159.0 70.2 147.6 244.7 92.9 8.4 4.7 345.1 71.3 11.1 54.6 9.9 83.6 31.4 1.6 15.2 31.5 16.7 1.4 49.4 3.4 48.9 56.2 6.1 24.6 30.7 1.9 12.7 9.5 5.0 2.2 15.6 0.6 7.5 1.9 9.5

1598 1586 1502 1468 1444 1420 1407 1389 1368 1302 1294 1287 1248 1225 1207 1189 1155 1138 1099 1014 966 953 915 936 885 851 835 785 759 730 710 672 658 624 605 588 571 562 533 513 492 470 464

1576 1504 1468 1446 1419 1408 1370 1303 1294

1225

1163 1142 1101 1014 1005 962 950 915 885 851 832 795 766 733 718 672 657 639 618 605

535 494

448 417 400 336 324 303 283 262 247 225 213

t,g-g-conformation

Assignment

84 50 62 36 36 47 68 88 45 45 57 57 80 80 80 26 26 45 40 69 59 51 38 38 79 19 34 27 48 66 71 71 87 20 20 38 38 32 36 15 58 60 24 18 18 21 21 25 85 65 39 39 31 23 21 21 24 19 16 44 44 36

m(C@O) m(CCar), 18 d(CCH) m(CCar), 17 d(CCH) m(C@N), 36 m(CCar), 7 d(CCH) m(C@N), 36 m(CCar), 7 d(CCH) d(CCH), 31 m(CCar) d(HCH), 16 d(NCH) d(HCH) m(CCar), 41 d(CCH) m(CCar), 41 d(CCH) d(NCH), 39 d(HCH) d(NCH), 39 d(HCH) d(CCH) d(CCH) d(CCH) m(CC), 16 d(CCH), 17 d(NCH) m(CC), 16 d(CCH), 17 d(NCH) m(CO), 15 d(CCH), 12 m(CCar) m(CO), 21 d(CCH), 13 m(CCar) d(CCH), 15 m(CCar) d(CCH), 20 m(CO), 16 m(CCar) d(CCH), 21 m(CCar) d(CCC), 35 m(CCar), 22 d(CCH) d(CCC), 35 m(CCar), 22 d(CCH) q(CH) m(PN), 18 d(CNH), 15 m(CN) m(NN), 19 d(CNH), 19 m(PN) m(PN), 21 m(NN), 21 d(NCH) m(PO), 23 m(CO), 18 m(CCar) q(CH) q(CH) q(CH) q(CH) m(P 0 @S), 16 m(PN), 14 m(PO) m(P 0 @S), 16 m(PN), 14 m(PO) m(P 0 @S), 17 m(PO) m(P 0 @S), 17 m(PO) v(CC), 30 q(CH) v(CC), 31 q(CH) m(P@S), 11 d(CCC) d(CCC), 12 d(CCH) d(CCC), 18 d(CCH) d(CCC), 22 m(P@S), 12 m(PN) d(CCC), 17 d(POC) d(CCC), 17 d(POC) d(POC), 18 m(P@S), 12 q(CH) d(POC), 18 m(P@S), 12 q(CH) q(CH), 16 v(CC) v(PC) v(PC), 15 d(SPO), 7 v(CC) v(PC), 20 d(SPO) v(PC), 20 d(SPO) v(PO), 30 d(OCC) v(CC), 15 q(CH), 14 d(OCC) v(PN), 16 v(CN), 15 q(CH) v(PN), 16 v(CN), 15 q(CH) v(NN), 20 v(PN), 20 v(CC) v(PN), 19 v(NN), 16 q(CH) d(CNN), 22 d(SPO), 8 v(CC) q(CH), 22 d(SPO), 8 v(CC) q(CH), 21 d(SPO), 17 v(CC) d(SPN), 21 d(SPO), 17 v(CC)

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Table 3 Global and local reactivity descriptors of dendrimers G1 and G01 System

Atom

Group

Ionization energy (eV)

Electron affinity (eV)

Global softness (au)

Local softness (au) s k

G1

5.777 P S O N S P N Cl Cl

S@PO3 S@PO3 S@PO3 C@N S@PCl2 S@PCl2 N@PCl2 S@PCl2 S@PCl2

P S O N S P N O O

S@PO3 S@PO3 S@PO3 C@N S@PO2 S@PO2 N@PO2 N@PO2 C@O

G01

5.878

located in the terminal groups in dendrimers G1 and G01 , the core P@S bond is less active. The reactivity of the repeated units is also less than that of terminal groups. In summary the investigation of FT-IR and FT-Raman spectra of the first generation of phosphorus-containing dendrimer with aldehyde terminal groups was carried out. The DFT study provides a proof of the actual structure of the phosphorus-containing dendrimer. Full optimization yielded the t,g,g-conformer of terminal groups of the G01 with SPOC dihedral angles: 50.8°, 56.1°, and the dihedral angles POCC: 94.0°, 92.5°. Another energy minima was found for the t,g,-g-conformer of G01 the with SPOC dihedral angles: 53.6°, 59.5°, and the dihedral angles POCC: 88.0°, 101.7°. The t,g,g-conformer is 0.34 kcal/ mol less stable compared to t,g,-g-conformer. A complete spectral interpretation was proposed on the basis of experimental information and quantum chemical DFT calculations. The calculated spectra reproduce the main features of experimental spectra of the G01 . Our study reveals that in the G01 and G1 the most reactive are the terminal groups. References [1] G.R. Newkome, C.N. Moorefield, F. Vogtle, Dendrimers and Dendrons: Concepts, Syntheses, Applications, VCH, Weinheim, 2001. [2] D.N. Reinhoudt, J.F. Stoddart, R. Ungaro, Chem. Eur. J. 4 (1998) 1349.

2.821

2.801

sþ k

4.603 0.028 0.221 0.029 0.156 0.552 0.074 0.221 0.202 0.184

0.018 0.156 0.016 0.129 0.570 0.230 0.055 0.386 0.524

0.009 0.087 0.029 0.051 0.164 0.020 0.073 0.021 0.111

0.002 0.009 0.005 0.007 0.070 0.004 0.000 0.005 0.126

4.584

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