Quantum-chemical study of nitrosonium complexes of monocyclic aromatic compounds

Abstract

With the use of Hartree-Fock and DFT methods we demonstrated that for the benzene derivatives with the substituents Me, Et, Pr, i-Pr, t-Bu, CF 3 , F, and Cl π-complexes are more favorable by energy, whereas with the substituents CHO, MeCO, PhCO, CN, NO, and NO 2 n-complexes are more feasible. The affi nity of aromatic compounds to the nitrosonium-cation (A NO +) at the formation of the π-complexes grows with the growing donor character of the substituents in the ring and with their number. The best agreement between the calculated and experimental A NO + values for benzene was obtained with the use of RI-MP2/L1 method.Nitrosonium complexes of aromatic compounds are intensively investigated for many years [1][2][3][4][5][6][7][8][9][10][11]. The interest in these compounds originate from their participation as intermediates in a number of important organic reactions like diazotization, C-nitrosation, and nitration via the nitrosation of aromatic compounds [12,13]. It was established that the NO + cation catalyzed the bromination of aniline derivatives [14] and the proton exchange in N,N-dimethylanilinium-ion [15] ascribing these facts to the formation of the corresponding complexes arene-NO + . The interest to the studies of the nitrosonium complexes grew as the unique role of the NO molecule in the in vivo processes was discovered [1,16]. It is presumed that the nitrosonium-cation and some molecules being its sources take part in the processes of neurotoxic and neuroprotective actions of nitrogen oxide [17], and also are involved in the reactions resulting in DNA cross-linking [18]. Inasmuch as the experimental measurement of the aromatic compounds affi nity to the nitrosonium-cation (A NO +) is a complicated problem [1,19,20] it is interesting to apply the quantum-chemical methods to the calculation of A NO + values.The goal of this study is the theoretical investigation of the effect of structural factors on the complex formation of NO + cation with monocyclic aromatic compounds and establishing the features of the structure of the nitrosonium complexes.The following aromatic compounds we have chosen as the objects of the study: benzene (Ia) and its derivatives C 6 H 5 X Ib-Io, and also compounds II-VII. The choice of the objects of the study took into consideration the existence of the experimental data on the affi nity of the aromatic compounds to the NO + cation and the presence of spectral and XRD data supporting the formation of the nitrosonium complexes [1,[4][5][6].Quantum-chemical calculations were carried out by the methods DFT/PBE/3z [21] and RI-MP2/L1 [22] applying the program package PRIPODA [23], and also by Hartree-Fock (RHF) [24] and B3LYP [25] methods using GAMESS software [26]. The calculations were performed with the complete optimization of the geometry of all molecular structures corresponding to the stationary points, and the corrections for the zero vibration level to the total energy of the species also were taken into account. The electronic correlation was accounted for by the Møller-Pl...

Quantum chemical study of nitrosonium complexes of the 9-methyladenine-1-methylthymine complementary pair. Structure and dynamics

“…The calculations were performed by the RI-MP2/L1 method. As shown previously, this method provides a good agreement between the calculated geometric parameters of nitrosonium complexes derived from aromatic compounds, as well as their relative affinities for nitrosonium ion, and the experimental data [9,10]. The RI-MP2/L1 method was used to study nitrosonium complexes of uracil, thymine [11], adenine [12], cytosine [13], and the complementary pair 1-methylcytosine-9-methylguanine [14].…”

Quantum-chemical study on nitrosonium complexes of Bi- and polycyclic aromatic compounds

“…As we already noted, RI-MP2/L1 and DFT/PBE/3z calculations give similar relative affinity series of compounds X-XV for nitrosonium ion [39]. Joint processing of the affinities of compounds I-IX and X-XV [39] for nitrosonium ion, calculated by the two methods, gave a linear correlation shown in Fig.…”

“…It was found previously that the RI-MP2/L1 and DFT/PBE/3z quantum-chemical methods give similar geometric parameters of nitrosonium complexes derived from benzene and its derivatives, as well as similar relative affinity series of these compounds to nitrosonium ion [39]; therefore, we used the above methods in the present work. DFT/PBE/3z calculations of structures with large number of atoms take much shorter time (by several orders of magnitude) as compared to RI-MP2/L1.…”

“…Joint processing of the affinities of compounds I-IX and X-XV [39] for nitrosonium ion, calculated by the two methods, gave a linear correlation shown in Fig. 4.…”

“…1, Table 1) [1,[39][40][41][42][43][44][45]. All these complexes are characterized by angular arrangement of the NO group with respect to the benzene ring plane, sp 2 hybridization of carbon atoms in the aromatic ring, and long distances between the NO nitrogen atom and the nearest carbon atoms in the aromatic ring (2.3-2.4 Å).…”