Vibrational Spectroscopy 75 (2014) 1–10 Contents lists available at ScienceDirect Vibrational Spectroscopy jou r n al hom ep age: www.elsevier.com/locate/vibspec DFT study of structure, IR and Raman spectra of phosphorus-containing dendron with azide functional group V.L. Furer a,∗ , A.E. Vandyukov b , J.P. Majoral c , A.M. Caminade c , S. Gottis c , R. Laurent c , V.I. Kovalenko b,∗ a Kazan State Architect and Civil Engineering University, Zelenaya, 1, 420043 Kazan, Russia b Institute of Organic and Physical Chemistry, Russian Academy of Science, Arbuzov Str., 8, 420088 Kazan, Russia c Laboratorie de Chimie de Coordination, CNRS, 205 route de Narbonne, BP 44099, 31077 Toulouse Cedex 4, France a r t i c l e i n f o Article history: Received 22 June 2014 Received in revised form 23 July 2014 Accepted 20 August 2014 Available online 27 August 2014 Keywords: Phosphorus-containing dendron Azides IR spectra Raman spectra DFT a b s t r a c t The Fourier transform IR and Raman spectra of the first generation dendron G 1 built from thiophosphoryl core with terminal P Cl groups and azide functional group have been recorded. The optimized geometries of low energy isomers of G 1 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 G 1 contain planar O C 6 H 4 CH N N(CH 3 ) P< fragments. DFT results for the structure of G 1 are in good agreement with recent X-ray diffraction measurements. A complete vibrational assignment is proposed for different parts of G 1 . 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 why azide group linked to phosphorus has a different reactivity when compared to organic azides. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Dendritic-type architectures are frequently encountered in the biological world, such as the branches and roots of plants [1–3]. Dendrimers constitute a small-scale artificial model of these natu- ral dendritic architectures [4–6]. The three structural components of dendrimers, namely an interior core, repeated branching units radially attached to the core, and functional terminal groups attached to the outermost branching units, can be tuned at will [2]. A fine control of the overall size (the generation), shape, and properties of the dendrimer, creating special three-dimensional environments, can be achieved [2]. The dendrons possess one reac- tive functional group at the level of the core [3]. The grafting of dendrons on dendrimers allows to increase the number of end groups of the dendrimer in one step [3]. Organic azides are employed in chemistry, biology, medicine, and materials science [7]. Besides organic azides, in which the azide ∗ Corresponding authors at: Kazan State Archi & Civil Eng. University, Zelenaya 1, 420043 Kazan, Russian. Tel.: +7 8432 732283/+7 8432 1047 37; fax: +7 8432 732253/+7 8432 387972. E-mail addresses: furer@kgasu.ru, furer@mi.ru (V.L. Furer), koval@iopc.ru (V.I. Kovalenko). function is connected directly to carbon atom, hetero azides are of importance in organic synthesis [7]. An azide linked to a phospho- rus seems to have a different reactivity when compared to organic azides: we cannot perform Huisgens (click) reaction with alkynes [7]. However, we can perform Staudinger reactions with phos- phines [7]. Several phosphorus azides were used for the synthesis of various types of dendrimers, dendrons and hyperbranched poly- mers [3]. A Staudinger reaction between a phosphine and an azide linked to a P(S) group creates a phosphazene linkages substituted by a thiophosphoryl group (P N P S) [3]. This linkage is particu- larly interesting for further reactions at specific layers within the structure of a dendrimer [4]. To yield a better understanding of the properties imparted by each component to the whole structure and the influence of each part on the others, it is highly desirable to introduce the quantum-chemical density functional theory (DFT) studies of elec- tronic structure of low-generation dendrimers. The preparation and IR and Raman spectra of phosphorus dendrimers built up to 12th generation with terminal aldehyde and P Cl groups were reported [8–14]. Considering the size of dendrimer molecules the difficulty arises in spectral interpretation, and, therefore, DFT cal- culations would help facilitate spectral assignment. In this work our aim is to combine the experimental results with quantum-chemical DFT calculations to interpret IR and Raman http://dx.doi.org/10.1016/j.vibspec.2014.08.008 0924-2031/© 2014 Elsevier B.V. All rights reserved.