Abstract: In our previous work (see ECSOC-12, 2008) we found some interesting dependencies of ortho-protons chemical shift (δ_o^H) in monoalkylbenzenes NMR ¹H spectra upon the place and degree of branching of alkyl chain. If the branching takes place at the α-carbon atom, the downfield shift of basic spectral parameter - δ_o^H - (α-effect) is observed and entitled as "α-effect"; the branching at β-carbon atom leads to the shift toward upfield ("β-effect"). α-Effect has a positive value because δ_o^H value increases with the increase of amount of methyl groups in α-position, contrary, β-effect has a negative value. The natural question emerges: which other classes of aromatic compounds (in addition to monoalkylbenzenes) the founded regularities apply to? We obtain the answer while studying NMR ¹H spectra of 17 especially selected rows of monoalkylbenzenes with functional groups in alkyl substituent. Extended interpretation of the term "functional groups" allows to examine alkyl groups with multiple bonds C=C, CºC and C=O as a functionalized fragment. Depending upon the place of alkyl chain branching all compounds are divided into two types. In the compounds of A type the branching takes place at α-carbon atom and in the compounds of B type – at β-carbon atom. The variable fragments may be only hydrogen atom or methyl group. The use of differential spectral parameters (Δδ^Н_о) instead of basic ones (δ_о^Н) is more advisable because of the great scattering of δ_о^Н,N(n) values. The differential spectral parameter is a difference between the value of ortho-protons chemical shift δ_о^Н,N(n) of the investigated compound N_n and the same value δ_о^Н,N(0) of the standard compound, when all variable substituents R¹ = R² = R³ = Н. The δ^Н_о and Δδ^Н_о values of all A and B type compounds are demonstrated in 2 tables and 2 diagrams. The new regular "structure-property" dependencies which were determined for nonfunctionalized monoalkylbenzenes are observed for all values of basic spectral parameters δ₀^{H, N(n)} in the investigated rows of monoalkylbenzenes substituted by functional substituents in the side chain. α- and β-Effects (change of chemical shift of ortho-protons δ₀^H in NMR¹H spectra) are explained by changes of saturation of definite spatial areas near phenyl ring by methyl groups. It should be stressed that for the investigated compounds 1-17 there are no facts contradicting with the existing of "α-effect" at the branching of alkyl chain near α-carbon atom and "β-effect" observed at the branching near β-carbon atom. The similar regular "structure-property" dependencies are reported for monosubstituted para-alkylaromatic compounds in two our accompanied communications, which we also intend to sent to ECSOC-15.

Abstract: In our previous works (see ECSOC-15, 2008 and also 2 our accompanied communication) we found interesting dependencies of ortho- and meta-protons chemical shift (δ_o^H) in monoalkylbenzenes and disubstituted para-alkylaromatic compounds NMR ¹H spectra upon the place and degree of branching of alkyl chain. If this branching takes place at the α-carbon atom, the shift of basic spectral parameter – δ_i^H (δ_o^H or δ_m^H) - is observed and entitled as "α-effect"; the branching at β-carbon atom leads to another type shift ("β-effect"). The positive value of α- or β-effect means that δ_i^H value increases with the increasing of amount of methyl groups in α- or β-position; contrary, negative value of such effect mean decrease δ_i^H value. The natural question emerges: are α- and β-effects for phenyl ring carbon atoms existed too? We obtain the answer while studying NMR ¹H spectra of 26 especially selected rows of disubstituted para-alkylaromatic compounds N_n of the general formula p-Y-C₆H₄-(CH₂)_r-CR¹R²R³ (where r=0 or r=1). We examined as substituents "Y" 26 the most widespread groups from most electronegative (NO₂) to most electropositive (NMe₂). The variable fragments (R¹, R², R³) given in general formula are only hydrogen atom or methyl group. Depending upon the place of alkyl chain branching all compounds we divide into two types: the compounds of A type (r=0 in general formula), where the branching takes place at α-carbon atom and compounds of B type branched at β-carbon atom (r=1). The differential spectral parameters (Δδ_i^C) were used instead of basic ones (δ_i^C). The Δδ_i^C parameter means a difference between the value of studied carbon chemical shift δ_i^C,N(n) of the examined compound N_n and the same value δ_i^C,N(0) of the standard compound, where all variable substituents R¹ = R² = R³ = Н. The δ_i^C,N(0) and Δδ_i^C parameter values of all A and B type compounds are demonstrated in 5 tables. Averaged values of differential parameters were calculated, tabulated in additional 4 tables and pictured on 4 diagrams. In our communication we have a broad discussion of values and signs calculated for all types averaged differential parameters. The regular "structure-property" dependencies (α- and β-effects) which were founded only for δ₀^H,N(n) parameters, are also detected for 4 types of δ_i^C,N(n) parameters of studied disubstituted para-alkylaromatic compounds. Such α- and β-effects were observed for all examined differential spectral parameters Δδ_i^C,N(n) in all investigated rows of disubstituted para-alkylaromatic compounds. It should be stressed that for the investigated rows of compounds 1-26 there are no facts contradicting with the predicting values and signs of both α- and β-effects. The similar regular "structure-property" dependencies are also examined for ¹H NMR spectra parameters of other aromatic compounds in our accompanied communication, which we also want to sent now to ECSOC-15.

Abstract: In our previous works (see ECSOC-15, 2008; and also our accompanied communication №1) we found some interesting dependencies of ortho-protons chemical shift (δ_o^H) in monoalkylbenzenes NMR ¹H spectra upon the place and degree of branching of alkyl chain. If this branching takes place at the α-carbon atom, the shift of basic spectral parameter – δ_i^H (δ_o^H or δ_m^H) - is observed and entitled as "α-effect"; the branching at β-carbon atom leads to another type shift ("β-effect"). The positive value of α- or β-effect means that δ_i^H value increases with the increasing of amount of methyl groups in α- or β-position; contrary, negative value of such effect mean decrease δ_i^H value. The natural question emerges: which other classes of aromatic compounds (in addition to monoalkylbenzenes) the founded regularities apply to? Are α- and β-effects for meta-protons existed too? We obtain the answer while studying NMR ¹H spectra of 21 especially selected rows of disubstituted para-alkylaromatic compounds N_n of the general formula p-Y-C₆H₄-(CH₂)_r-CR¹R²R³ (where r=0 or r=1). We examined as substituents "Y" 21 the most widespread groups from most electronegative (NO₂) to most electropositive (NMe₂). The variable fragments (R¹, R², R³) given in general formula are only hydrogen atom or methyl group. Depending upon the place of alkyl chain branching all compounds we divide into two types: the compounds of A type (r=0 in general formula), where the branching takes place at α-carbon atom and compounds of B type branched at β-carbon atom (r=1). The differential spectral parameters (Δδ^Н_о) were used instead of basic ones (δ_о^Н). The Δδ^Н_о parameter means a difference between the value of studied proton chemical shift δ_i^Н,N(n) of the examined compound N_n and the same value δ_о^Н,N(0) of the standard compound, where all variable substituents R¹ = R² = R³ = Н. The δ_i^Н,N(0) and Δδ_i^Н parameter values of all A and B type compounds are demonstrated in 3 tables. Averaged values of differential parameters were calculated, tabulated in 2 tables and pictured on 2 diagrams. In our communication we have a broad discussion of values and signs calculated for all types averaged differential parameters. The regular "structure-property" dependencies (α- and β-effects) which earlier were founded only for monoalkylbenzenes δ₀^H,N(n) parameters, are also detected for δ₀^H,N(n) and δ_m^H,N(n) parameters of studied disubstituted para-alkylaromatic compounds. Such α- and β-effects were observed for all examined differential spectral parameters Δδ_i^H,N(n) in all investigated rows of disubstituted para-alkylaromatic compounds. It should be stressed that for the investigated rows of compounds 1-21 there are no facts contradicting with the predicting values and signs of both α- and β-effects. The similar regular "structure-property" dependencies are also examined for ¹³C NMR spectra parameters of the same disubstituted para-alkylaromatic compounds in our next communication №3, which we also want to sent now to ECSOC-15.

Abstract: At the XIV Conference ECSOC (2010), we made the first post, which opened a new section of our research - the study of influence on each other through the space of two molecule fragments, unconnected by chemical bonds, at the time of registration of NMR spectra. In this investigation it was found that the aryl ring has the greatest influence on the spectral parameters of the studied fragment of the molecule, which is separated from the aryl groups by one or more chemical bonds. In the present communication we conduct systematic investigation of the described phenomenon researching the methyl and ethyl esters of ω-aryl fatty acids by general formula: Ar-(CR¹R²)_m-X-(CR³R⁴)_n-COOAlk, where Alk = Me or Et, and X = N or O. We have studied such esters: i) of aromatic acids (m = n = 0, heteroatom X in them missing), i.e. unsubstituted and substituted benzoic (1), α-naphthoic (2); ii) of ω-arylcarbonic acid (m = 0, heteroatom X in them missing): arylacetic (3) (n = 1), β-arylpropionic (4) (n = 2) and γ-arylbutyric (5) (n = 3), as well as iii) acids, in which the alkyl moiety of the molecule acidic fragment contains heteroatom X (nitrogen or oxygen) (6). The presence or absence of the aryl fragment influence on the alkoxy group was judged on the value of the basic spectral parameters - the chemical shifts of methyl protons (δ_СН3^Н) as well as (δ_СН2^Н and δ_СН3^Н) in ethyl groups. There were developed and validated specific criteria for identifying such effect. One of them is based on the introduction of a new virtual parameter - the expected value of the chemical shift of alkoxy group protons. By the sum of the results, obtained using all the necessary criteria, we make judgments about the probability of the presence or absence of the studied effect. There were suggested the presence of studied effects in ethers 3-6, and its absence in the esters 1 and 2, with the exception of esters of substituted benzoic acids (1), in which the substituent in the ortho-position is aryl group. Based on the virtual differential ∆δ_СН2^Н and ∆δ_СН3^Н ​​ parameters values (which is equal to the difference between "experimentally obtained" and "expected" values ​​of the basic spectral parameters δ_СН2^Н or δ_СН2^Н), as well as other criteria, we make judgments about the magnitude of the studied effect in esters 3-6 as well as its dependence on the values ​​of m, n, and X. A comparison of aryl group "influence magnitude" aryl group on the protons of methyl and methylene fragments of ethoxyl group. We make the overall conclusion about high probability of the studied effect existence in esters 3-6 and, especially, in compounds 3 and 4.

Abstract: Our group has been involved in searching new synthetic routes to organostannanes by the S_RN1 mechanism.¹ Based on our experience we consider of interest to study the scope of S_RN1 in the polystannylation of an aromatic ring. Now we inform the experimental results obtained in the reaction of trimethylstannylsodium (1) with aryl phosphates supporting three nucleofugal groups, in liquid ammonia as solvent, and a DFT study which support the notable differences observed between isomeric substrates. In order to synthesize 1,2,4-tris(trimethylstannyl)benzene (2) we use as starting substrates 1,3-bis(diethoxyphosphoryloxy)-4-chlorobenzene (3) and 1,4-bis(diethoxyphosphoryloxy)-3-chlorobenzene (4). Under photostimulation 3 and 4 led to entirely different products distributions. Meanwhile 3 afforded 2 together with 1,3- and 1,4-bis(trimethylstannyl)benzene in a 63:23:10 ratio, 4 yielded a mixture of 2 and 1,4- bis(trimethylstannyl)benzene in a 32:68 ratio. Starting substrates were almost recovered in dark reactions supporting an S_RN1 mechanism. These results were unexpected since the substrates would have similar electron affinities. We have previously demonstrated that differences in spin density on radical anions affect products distributions,² so, we started a systematic theoretical study over 3 and 4 with the B3LYP functional, the LACVP pseudopotential (Sn) and the 6-31+G* (C, H, O, P) with GAUSSIAN03. We observed meaningful differences in SOMOs MO, spin density distribution and activation energies of the corresponding radical anions intermediate, which support the experimental outcome and allow us to interpret the distribution of stannylated end-products in terms of the structural features of the starting isomers. ¹ Silbestri, G. F.; Lo Fiego, M. J.; Lockhart, M. T.; Chopa, A. B. J. Organometal. Chem. 2010, 695, 2578-95 and references therein. ² Dorn, V. B.; Badajoz, M. A.; Lockhart, M. T.; Chopa, A. B.; Pierini, A. B. J. Organometal. Chem. 2008, 693, 2458-62.

Abstract: The object of the present study is the isodesmic reaction of cellobiose (the repeating unit in cellulose) with different kinds of silanes, R-SiH₃, to form silylated cellobiose (Cello-SiH₃) and the corresponding alcohols (R-OH). The size and the chemical reactivity of the substituent R is varied as well as the position where O-silylation at the cellobiose takes place. In contrast to experimental observations where the O6 position is favored for silylation, for the computed reactions, energy differences are smaller than 3 kcal/mol for the different positions at the B3LYP/6-311G* as well as at the B3LYP/6-311+G* level of theory. Depending on the silane, reaction energies in a range from -17 kcal/mol (R=NHSiH₃) and +18 kcal/mol (R=F) have been calculated. In addition, semi-empirical calculations on the PM3 level of theory have been performed. These results are set into contrast with the results derived from DFT calculations to assess whether semi-empirical methods may be useful for the description of larger systems containing silylated cellobiose units. Acknowledgements: The research leading to these results has received funding from the European Community's Seventh Framework Programme [FP7/2007–2013] under grant agreement no. 214015 (S.S. and H.M.A.E.) and no. 214653.

Abstract: Fluorescent probes are widely used in membrane biophysical studies to investigate the properties of the molecular environment of cell membrane and biochemical processes related to it. These probes provide information of the molecular environment trough changes of their photophysical properties. While these probes can provide valuable information of the membrane molecular properties, a clear structural description, at the molecular scale, of the membrane properties surrounding the fluorescent molecular probe, is essential for the interpretation of the experimental fluorescent signal. In this work, we studied the membrane permeation properties of four benzo[a]phenoxazinium fluorescent probes with different alkyl chains in the tetracyclic ring in DPPC membranes using molecular modelling techniques . We describe the molecular mechanism of interaction between the molecular probes and the DPPC lipids. We show that probes can be preferentially located at the membrane water interface interaction with the lipid polar groups, while others can be cross the membrane in a passive way. This processes is dependent on the tetracyclic substitutions and alkyl chain present in the fluorescent probe. These findings can provide a detailed rational of the structural properties surrounding the molecular probes that could be correlated with the experimentally measured fluorescence.

Abstract: Ab-initio levels of theory using 6-31+G(d,p) basis set have been carried out to investigate the Isomeric structures, energies and properties of mononsilacyclopropylidenoids, C₂H₄SiMX (where M= Na or Li, and X= F, Cl or Br). The theoretical calculations depict that each of them has three stationary structures: silacyclopropylidenoid (S), tetrahedral (T), and inverted (I). All of the silacyclopropylidenoid (S) forms are energetically more stable than others except for S-LiF, whereas all of the tetrahedral (T) forms are the most unstable ones except for T-NaF. Energy differences between S, T, and I forms range from 0.60 to 8.70 kcal/mol. Moreover, natural bond orbitals (NBO), and frontier molecular orbitals (FMO) were achieved in this computational study.

Abstract: The lower molecular weight hydrocarbons that can be mapped on the buckminsterfullerene (C₆₀) structure are commonly known as "buckybowls" or "geodesic polyarenes" and have the distinctive characteristics of preserving the curvature and aromaticity of fullerene. These bowl-shaped structures are expected to be quite rigid. Nevertheless, the smaller members of the family, in spite of its substantial curvature are surprisingly flexible undergoing rapid bowl-to-bowl inversion in solution as evidenced by the dynamic NMR behavior of C₂₀H₁₀ (corannulene) and several of its derivatives. With the aim of gaining understanding in the bowl-to-bowl inversion, the present theoretical study has explored the effect that substitution of some of the hydrogen atoms of corannulene has on this process. The model systems studied have the formula C₂₀H_10-nR_n with R = -Cl, -Br, -C≡CH, -CH₃ and n = 0, 2, 4, 5, 6, 8, and 10. It is observed that the bowl depth is reduced only by high substitution levels or by a substitution pattern that conduces to important peri interactions. Full substitution with bulky groups causes a pronounced repulsion and the deformation of the transition structure for bowl inversion that otherwise is planar. The activation barrier for the inversion – bowl depth data fit an empirical quartic/quadratic function used previously in similar systems but the coefficients of the fitting don't follow the predicted substituent independency.

Abstract: Photochemical oxidations of propylene by means of nitromethane and nitroethane were studied by UB3Lyp/6-31g in both the triplet and singlet states. It was studied the reaction paths giving propylene oxide. Gaussian03 was used to perform the calculations of the transition states of the reactions using QST2 and QST3 methods. Activation energies were calculated for every stage of the reactions. It was shown that the reaction proceeds mainly on the triplet potential surface energy.

Abstract: The genome DNA is constantly exposed to endogenous and exogenous oxidative stresses. Damaged DNA can cause mutations, which may increase the risk of developing cancer, aging, and other diseases. Various oxidative stresses lead to G:C–T:A and G:C–C:G transversions, because guanine is highly susceptible to oxidative stress in the DNA, owing to the lowest oxidation potential among four nucleobases. One typical lesion product of guanine is 8-oxo-7,8-dihydroguanine (8oxoG), and DNA polymerases incorporate adenine but not guanine opposite 8oxoG lesions. More specifically, 8oxoG:A base pairs cause G:C–T:A transversions, and then the other oxidative guanine damages seem to cause G:C–C:G transversions. 2,5-diamino-4H-imidazol-4-one (Iz) and 2,2,4-triamino-5(2H)-oxazolone (Oz) are the oxidative guanine damages, which can pair with guanine, and several DNA polymerases incorporate guanine opposite these lesions in vitro. We previously reported that the calculated stabilization energy of Iz:G base pair is similar to that of C:G base pair and that of Oz:G base pair is planar and has two hydrogen bonds. Guanidinohydantoin (Gh) and spiroiminodihydantoin (Sp) are the oxidative products of 8oxoG. It was shown that Klenow fragment incorporated adenine and guanine opposite these lesions. Our previous study proposed Gh:G and Sp:G base pairs, however, the stabilization energy of these base pairs have not been calculated. Therefore, We estimated the stabilization energy of these base pairs by ab initio molecular orbital calculations.

Abstract: The extraordinary structures and properties of fullerenes have had an important impact on nanotechnology as these compounds exhibit outstanding mechanical and electronic properties. 1,3-Dipolar cycloadditions (1,3-DCs) have proved to be a powerful way to functionalize these conjugated ? systems and have offered wide opportunities for the creation of new nanocarbon structures with potential application in biological, biotechnology, material science and medicinal chemistry. The 1,3-DCs of fullerene (C60) with nitrile oxides, RCNO, have been studied in the gas phase using density functional theory (DFT) at the B3LYP/6-31G(d) level. Energetic and kinetic parameters have been determined at room temperature so as to investigate the effect of electron-withdrawing (R = F, Cl, Br, NC, CN and NO2) and electron-releasing (R = Me and Et) substituents attached to the nitrile oxides on the 1,3-DCs. These parameters have been interpreted in terms of group electronegativity and DFT reactivity indices. An unexpected behaviour was observed for the 1,3-DC involving FCNO as these reactions have some pseudodiradical character. Inspired by the results of the 1,3-DCs of nitrile oxides to C60, we have extended this theoretical gas phase research to the addition of a second HCNO to the cycloadduct of the addition of HCNO on C60. The various possibilities for the second addition are being explored with the aim of determining the thermodynamic and kinetic products. The findings of our research should be helpful to experimentalists in their quests for functionalized fullerenes.

Abstract: Corannulene is an unsaturated hydrocarbon composed of fused rings, one central five-membered ring and five peripheral six-membered rings. Its structure can be considered as a portion of C₆₀. Corannulene is a curved pi surface, but unlike C₆₀, it has two completely different faces: one concave (inside) and one convex (outside). In this work, computational modeling of the binding between alkali metals cations and corannulene has been performed at the DFT and MP2 levels. Different isomers of the corannulene/M⁺ binding have been studied and the transition states interconnecting local minima were located. The alkali cations can be bound to five or six membered ring in both faces. In DFT calculations, the binding to the convex face (outside) is favored relative to the concave face for the three alkali cations as it already has been published [R.C. Dunbar, J. Phys. Chem. A 2002, 106, 9809]. For Li⁺ and Na⁺, MP2 calculations are very similar and show the same trend, but for K⁺ the calculations are quite different and the trend is reversed. According to our results, migration of cations can take place over the convex or the concave pi-face. There are two ways to transform a concave complex in a convex complex: migration across the edge of corannulene and bowl-to-bowl inversion.

Abstract: One of the most important transformations of glycidic esters is their decarboxylation to give rise to aldehydes and ketones. A proposed mechanism for the decomposition of the ethyl 3-phenyl glycidate indicates that the ethyl side of the ester is eliminated as ethylene through a concerted six-membered cyclic transition state, and the unstable intermediate glycidic acid rapidly decarboxylates to give the corresponding aldehyde. Two possible pathways for the glycidic acid decarboxylation were proposed, one of them via a five-membered cyclic transition state and the other one via a four-membered cyclic transition state(Chuchani, G.; Tosta, M.; Rotinov, A.; Herize, A. J. Phys. Org. Chem. 2004, 17, 694). An accurate experimental description of the glycidic acid decarboxylation is a challenging task, since the glycidic acids decompose even at room temperature. Therefore, the goal of this work is investigated the path more favored by decarboxylation. Theoretical calculations were carried out in order to probe this proposed mechanism. Geometries of the different reactants, products and intermediates were optimized at different levels of calculation. The vibrational frequencies were calculated at the same level. The results were compared with those from experiments. Theoretical calculations indicate that the glycidic acid decarboxylation occurs via a five-membered cyclic transition state.

Abstract: Despite being intense in the gas phase, the strength of the interaction between a cation and an aromatic cloud decreases significantly when solvated. This effect has an important impact on a variety of systems where the cation•••pi interaction is known to play a key role. In the case of cation•••pi contacts involving aromatic amino acid residues, the degree of exposure to the solvent can be widely variable, so the interaction can be modulated by the environment in an almost continuous way. Most theoretical studies regarding cation•••amino acid interactions have been performed by considering simple alkaline cations in the gas phase. However, interactions can also be established with more complex cations from other amino acids, such as it is the case with arginine cationic side chain and the aromatic units in phenylalanine, tyrosine and tryptophan. In the present work ab initio and DFT methods were employed to study complexes formed by phenylalanine and a guanidinium cation representing the cationic chain of arginine. The results help understanding the impact of the interaction on the structure of phenylalanine, and constitute a first step towards the study of the effects caused by water molecules in the characteristics of these systems.

Abstract: Interactions between cations and aromatic molecules can be often find on a large number of biomolecular systems, such as proteins and receptor-ligand complexes. In addition, its important role in biological processes such as molecular recognition, drug action, and protein folding has been revealed by extensive experimental and theoretical investigations. Most previous theoretical investigations of cation···p interactions, have been focused on their characteristics in the gas phase, with less attention to their behavior in aqueous environment. In this latter case, most of the work has been focused on the whole effect of water solution as a medium on the cation···p interactions. Hence, it is important studying the influence of individual water molecules on the interaction as the cation···p complex is sequentially hydrated. The ammonium···phenol and methylammonium···phenol cation···p complex was selected as a model system to explore how water molecules affect the cation···p interaction. To mimic the process of water molecules binding to a cation···p complex, water molecules were introduced into the complex one by one. The purpose of this study is studying the geometrical characteristic of cation···p complexes with different numbers of water molecules and to investigate how the binding of water molecules to an existing cation···p complex affects the cation···p interaction.

Abstract: Among the different forces observed in biological complexes, the cation···p interaction is a strong, non-covalent binding force which participates in a wide variety of processes such as molecular recognition in biological receptors, enzymatic catalysis, etc. The nature and characteristics of this kind of interaction has been mainly theoretically studied in the gas phase, despite being known that the presence of water molecules modulates the strength of the interaction between metal ions and aromatic species. Besides, most studies have employed benzene as a prototype of aromatic unit. On the other hand, an also simple aromatic system as phenol presents two coordination sites for cations: the aromatic ring and the hydroxyl oxygen, thus allowing a greater variety of structures to be formed than in benzene. The hydroxyl group can also be hydrated and participate in the formation of the hydrogen bond network. In the present work, a study of the interaction between cations and phenol has been carried out to shed light on the effect of successive hydration on the interaction. So, ab initio and DFT methods were employed for studying the stepwise microhydration of phenol···cation complexes, locating the most stable structures and obtaining the corresponding complexation energies. The results suggest that the participation of the hydroxyl group is already relevant in clusters containing a small number of water molecules.

Abstract: Di-substituted silanetellurones, X₂Si=Te (X=H, F, Cl, Br, I and CN) are the target of this research. They are organometallic analogues, also known as heavy ketones, and they have recently been of great interest to researchers. Knowledge of the properties of such heavy ketones is important for a better understanding of both the chalcogen and substituent effects. The chemistry of multi-bonded compounds between group 14 and heavier chalcogen atoms has attracted chemists in various fields, as these molecules have proven to be convenient models for studying fundamental chemical problems and valuable intermediate products in synthesis. However, the literature of the mentioned species is limited and this research work endeavors a systematic investigation of these silanetellurones, using theoretical methods. We report the structural and spectroscopic parameters as well as the ionization potentials (IP_ad and IP_ad(ZPVE)), the neutral–anion separations (EA_ad and EA_ad(ZPVE)), the singlet–triplet splittings, the Kohn-Sham HOMO–LUMO gaps besides the nucleophilicity (N) and global electrophilicity (ω) indices. Since experimental data are still lacking for silanetellurones, the findings of this work would add to the literature, assist experimentalists to generate and further explore these novel species as well as rationalize some reactions pertaining to silanetellurones.

Abstract: The nature of selenium-sulfur non-bonding interactions in a series of substituted benzeneselenenyl derivatives has been investigated by means of computational techniques. The results of these calculations, together with experimental measurements (X-rays crystallography and NMR), suggest that the strength of this interaction increases with the increase of electronegativity of the substituent on selenium. Natural bond orbital (NBO) analysis suggests that this interaction has a mainly covalent character, rather than electrostatic, and originates from an interaction between a lone pair of sulfur and an antibonding orbital on selenium. Atom in molecules (AIM) analysis further supports this finding.