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Multicobalt(II) two-dimensional layer coordination polymer {[Co(bitbu-OMe)2(NCS)2]·2MeOH}n (1) was synthesized using a bis-imidazole ligand having a steric hindrance, tert-butyl, and one methoxy group expressed by bitbu-OMe (bitbu-OMe = 1,1’-[(5-tert-butyl-2-methoxybenzene-1,3-diyl)dimethanediyl]bis(1H-imidazole). Since there are two methanol molecules trapped inside each void within 1, the investigation of small organic matters removal from organic wastewater was conducted in order to reveal its ability in the purification process. The research findings indicate that 1 has the ability to capture methanol, acetone, acetonitrile, and tetrahydrofuran in organic wastewater with removal ratios of 29.17%, 63.22%, 42.77%, and 21.24%, respectively.

Graphical abstract Hydroxychloroquine (HCQ) and favipiravir (FPV) are known to be effective antivirals, and there are reports about their use to fight the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) despite that these are not conclusive. The use of combined drugs is common in drug discovery, and thus, we investigated HCQ and FPV as a combined drug. The density functional theory method was used for the optimization of geometries, spectroscopic analysis and calculation of reactivity parameters. The quantum theory of atoms in molecules was applied to explain the nature of the hydrogen bonds and confirm the higher stability of the combined drug. We also evaluated the absorption, distribution, metabolism and excretion (ADME) parameters to assess their drug actions jointly using SwissADME. The preliminary findings of our theoretical study are promising for further investigations of more potent and selective antiviral drugs. Supplementary Information The online version contains supplementary material available at 10.1007/s11696-021-01946-8.

The coating industry is one of the most important consumers of water and chemicals and consequently is a major water polluter in Mauritius. The focus of this study was to characterise wastewater generated by a coating industry in Mauritius. The objectives were to develop a wastewater sampling strategy and to analyse the pollutant parameters as per Mauritian regulations. The wastewater samples were analysed for physicochemical properties and metal abundances over a period of 6 months. The physicochemical parameters analysed were pH, electrical conductivity (EC), true colour, total suspended solids (TSS), biological oxygen demand (BOD

The purpose of this study was to remove dyes from synthetic dyed wastewater using activated carbon derived from rice husk. The initial dye concentration was 45 mg/L. The batch adsorption worked best in an acidic medium of pH 2, adsorbent dosage of 13 g/L and agitation speed of 100 rpm with maximum dye removal of 80% after 10 min. The maximum adsorption capacity of the absorbent was found to be 2.0 mg/g with a final dye concentration of 10.8 mg/L. The adsorption was found to be a non-spontaneous, endothermic chemisorption process with less disorder which best fitted the Temkin model and followed pseudo-second order. For column adsorption, the highest qo corresponds to 12.8 mg/g and the maximum dye removal was above 99.5%. Some of the experimental deductions were confirmed by gas-phase computations [B3LYP/6-31G(d)].

The properties of the hydrogen-bonded complexes of chloroform and bromoform with ammonia, water, hydrogen fluoride, phosphine, hydrogen sulphide and hydrogen chloride were studied by means of ab initio calculations. The properties of interest were the molecular structures, the interaction energies, the vibrational spectra and the nature of the orbital interactions involved in the formation of the complexes. Of particular interest was the determination of whether the various interactions exhibited red-shifted or blue-shifted hydrogen bond behaviour. The complexes optimized in three distinct structural models, singly bonded, cyclic and cage. The interaction energies, in the main, varied systematically with changes of the haloform and of the partner molecules. Changes of the CH or YH (Y = N, O, F, P, S and Cl) bond lengths correlated in most cases with the interaction energies, subject to some inconsistencies, with opposite behaviour being shown by the two sets. Similarly, the CH and YH stretching wavenumber shifts also displayed a dependence on the interaction energies, tracking with the bond length changes. Based on the diagnostic utility of these structural and spectroscopic properties, the complexes were found to be almost exclusively red-shifted, for binding through both the CH and YH groups. The orbital interactions responsible for the stability of the complexes were determined to be donation from a Y atom lone pair orbital of the partner molecule to a CH σ antibonding orbital and from a X lone pair orbital (X = Cl and Br) of the haloform to a YH σ antibonding orbital.

Density functional theory and time-dependent density functional theory computations were used to understand the electronic and photophysical parameters of NIR β-thiophene-fused BF2-azadipyrromethene dyes. The computed data are in good agreement with those obtained experimentally and they provide insights into the origin of red shifted optical spectra compared to the parent aza-BODIPY, low Stokes shift, non-linear optical responses and quantitative description of the singlet–triplet energy gap. The resultant decrease in the HOMO − LUMO energy gap is responsible for the red shift. The possible use as non-linear optical materials is supported by large enhancement in the non-linear optical properties. On the basis of vertical triplet energies, their possible potential therapeutic use as a photosensitizer in photodynamic therapy is proposed. The singlet–triplet energetic gaps suggest that the β-thiophene-fused BF2-azadipyrromethene dyes can act as a sensitizer to produce an efficient generation of singlet oxygen. Their optimal use as an efficient singlet fission materials has been proposed on the basis of excitation energies in the ground, lowest singlet and triplet excited states.

Density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations of two excited state intramolecular proton transfer (ESIPT) molecules [2,5-bis(2-benzothiazolyl)hydroquinone and 2,5-bis(benzo[d]thiazol-2-yl)-4-methoxyphenol] were performed to study their structural and photo-physical behavior upon excitation. The most stable structure was established by optimizing all possible rotamers. The vertical excitation and emission wavelengths obtained by using TD-DFT show very good correlation with the experimental values. A correlation has been established based on the absorption values to determine the contribution of stable rotamers.

This study was aimed at isolating hypaphorine from Erythrina mildbraedii Harms (Fabaceae) and Erythrina addisioniae Hutch. & Datziel (Fabaceae) in order to determine its structural and antibacterial effects. Density functional theory (DFT) calculations and X-ray crystallographic analysis of the isolated hypaphorine was determined. The antibacterial effects of hypaphorine against a number of Gram positive and Gram negative bacterial strains were investigated. The root mean square deviation between the experimental and calculated bond lengths and bond angles of hypaphorine were found to be 0.046 A and 1.5° respectively. The highest occupied molecular orbital (HOMO) of hypaphorine was delocalised on the indole moiety whereas the lowest occupied molecular orbital (LUMO) was delocalised on the –N(CH3)3 group and the HOMO–LUMO gap of hypaphorine was 4.65 eV. Hypaphorine inhibited the growth of the Gram-positive bacteria tested, namely Bacillus cereus, B. subtilis, Staphylococcus aureus and S. epidermidis. The lowest minimum inhibitory concentration (MIC) value of 2 mg/mL was exhibited against Mycobacterium smegmatis, Staphylococcus aureus and B. subtilis. The theoretical and experimental results from this study showed that hypaphorine is capable of forming quadrupole moments thus explaining its antibacterial effects on Gram positive bacteria.

The local and global reactivity descriptors of substituted dinitroaniline analogues were investigated using M06-2X/6-31 + G(d,p) method. It was observed that NH2 (m = 3.53 eV; p = 3.70 eV) substituent conveyed the highest nucleophilic character on the benzene ring system than the other groups under study. For the substrates 4-substituted-1-chloro-2,6-dinitrobenzenes, the condensed to atom electrophilicity ( $$ {\omega}_k^{+} $$) increases in the order COOCH3 > NO2 > F > SO3H > CN > Cl > Br. The para substituted groups with the halogens follow the order of increasing electronegativity, F > Cl > Br. However, the nucleophilicity of the halo substituents of the products increases in the order, F > Br > Cl. Molecular docking simulations using the homology model with the crystallographic structure of zinc-induced bovine tubulin heterodimer (1JFF) as one of the templates reveal that the interactions between the tubulins of Plasmodium falciparum and dinitroaniline analogues are due to H-bonding. In general, the binding interaction is with the following residues: Met137, ARG64, Lys60, Glu183, Val4, His28, Cys171, Tyr224, Asn206, 228, Ile235, and Leu238. The pKas of the residue decrease as the ring activating power of the substituents increases from strongly activating to weakly activating groups. There is no evidence of intra or intermolecular H-bonding between Arg64 and Cys171. Electronegativity (χ) gives a better generic description of the dinitroanilines than any other parameters considered. Short-range hydrophobic interaction contributes to reduced binding affinities of the ligands.

The electronic structures and spectroscopic properties of triphenylamine-based monostyryl and bis(styryl) dyes were studied using quantum chemical methods. The ground-state geometries of these dyes were optimized using the density functional theory (DFT) method. The lowest singlet excited state was optimized using time-dependent density functional theory (TD-DFT). The absorption was also calculated using the ground-state geometries. All the calculations were carried out in the gas phase and in solvent. The results indicate that the absorption maxima calculated using the TD-DFT are in good agreement with those obtained experimentally. These dyes possess a large second-order non-linear property and this is mainly due to the strong donor-π-acceptor conjugation which is attributed to the excited state intramolecular charge transfer (ICT). There is a relationship between the hardness and first hyperpolarizability and second hyperpolarizability of mono- and bis(styryl) dyes. The efficiency of the intersystem crossing process can be improved by reducing the energy gap between the singlet and triplet excited states.

The 2,2'-dinaphtholazobenzene molecular framework (P) was designed, synthesized and characterized. Its absorption and fluorescence properties revealed that P is a dual sensor for copper ions (Cu2+) and fluoride ions (F-) in DMSO. The colorimetric activities were clearly visible by naked eye upon the addition of the two ions. Fluorescence quenching and enhancement were observed when Cu2+ and F- ions were added respectively. Density Functional Theory (DFT) calculations were carried out to provide an insight into the interaction of guest ions (Cu2+ and F-) with P, and to explain how the molecular orbitals were affected. Graphical Abstract ᅟ.

The optimized molecular structures, vibrational wavenumbers and corresponding vibrational assignments of the syn and anti conformers of 2-, 3- and 4-pyridine carboxaldehydes and their sulfur and selenium analogues were calculated using the density functional theory method employing the B3LYP functional with the 6-311++G(d,p) basis set and second order Moller–Plesset Perturbation Theory (MP2) method with the cc-pVDZ basis set. The calculations were adapted to the C s symmetries of all ground state structures. The transition state arising from syn-anti isomerization was also modelled. All structures were fully optimized, and the geometries, rotational constants, dipole moments, charges, thermodynamic properties and energies are reported. Energies of the optimized structures were used to obtain the energy difference between the syn and anti conformers and the rotational barrier. The calculated vibrational wavenumbers were appropriately assigned to the various fundamental modes of vibrations. The Integral Equation Formalism Polarization Continuum Model was used to calculate the optimized geometry and the vibrational wavenumbers for all of the compounds in nine solvents: heptane, chloroform, tetrahydrofuran, dichloroethane, acetone, ethanol, methanol, dimethylsulfoxide and water. In addition, the LUMO, HOMO and energy band gap are also reported. The results indicate that the anti conformer is preferred with a rotational barrier of at least 19 kJ·mol−1.

The photo-physical behaviour of bis-2,5-(2-benzoxazolyl) hydroquinone and 2,5-bis (benzo[d]oxazol-2-yl)-4-methoxyphenol was studied using the Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT). All the possible rotamers were optimized to obtain global minimum optimized structure. The theoretical absorption and emission values of rotamers estimated by using TD-DFT [TD-B3LYP/6-31G(d)] are in good agreement with experimental absorption and emission wavelengths. Based on the absorption values, the contribution of respective rotamer is determined theoretically.

A number of properties of the homodimers of the three families of molecules MH3X, where M is Si, Ge, and Sn and X is F, Cl, Br, and I are computed. The results are compared with those of a similar study of the homodimers of the methyl halides containing the same four halogen atoms, and some notable differences are observed among related sets of monomer species. The interaction energies, the primary intermolecular geometrical parameters, the changes in the intramolecular bond lengths, and the vibrational data (wavenumber shifts and dimer/monomer infrared intensity ratios) of some of the modes most closely associated with the site of interaction show, for the most part, regular variations as the central atom and the halogen atom are systematically varied. The results are interpreted in terms of the changes in the bonding properties of the monomer molecules as they undergo dimerization.

The photophysical and electrochemical properties of eleven polycyclic benzimidazole fused organic pigments (four based on phthalic anhydride, four based on naphthalic anhydride and three based naphthalene tetra carboxylic acid dianhydride) were investigated using density functional theory and time dependent density functional theory methods (B3LYP/6-31G(d) and M06/6-31G(d)). The predicted geometries are comparable using both functionals. The electrochemical properties are in good agreement with the experimental results. However, the experimental absorption-emission properties are closer to the values computed using the M06/6-31G(d) method. Both the methods perform equally well in explaining the intramolecular charge transfer characteristics. This work can help to understand the modern age functional materials at molecular level and to design new molecules.

The characterization of the seleno-sulfide-bromo systems and the isomerization process on the [H, S, Se, Br] potential energy surface were investigated using state-of-the-art theoretical methods. The CCSD(T) and the MP2 levels of theory were employed along with the series of correlation consistent basis sets extrapolated to the complete basis set (CBS) limit in the optimization of the geometrical parameters and computation of electronic energies. The relative stability, in kcal mol−1, at the CCSD(T)/CBS follows the trend: HSSeBr (0) > HSeSBr (9.51) > SSeHBr (24.02) > SeSHBr (25.42). This order was observed in the previous study of the [H, S, Se, Cl] species. The structural parameters and vibrational frequencies of the [H, S, Se, Br] species are reported. This research work should be helpful to experimentalists in order to gain insights into these novel heteroatom molecules.

The structural and electronic properties of the neutral gallium sulfide (GaS2, Ga2S2, GaS4, and Ga2S4) clusters along with their anionic counterparts have been investigated systematically using the density functional theory, the second-order Moller–Plesset perturbation theory (MP2), and coupled cluster singles and doubles, including noniterative triples [CCSD(T)] with the 6-311+G(2df) basis set. At the CCSDT(T)//MP2 level, the lowest-energy configurations of the gallium sulfides prefer to be cyclic (GaS2), linear (GaS2 −), kite shape with a thiozonide unit (GaS4 and GaS4 −), rhombic (Ga2S2 and Ga2S2 −), and planar with two sulfur atoms in a terminal position (Ga2S4 and Ga2S4 −) geometries. In the gallium–sulfur binary clusters considered in this study, the neutral and anionic ground-state geometries prefer the planar structures with alternation of gallium and sulfur atoms. All the neutral clusters, with the exception of Ga2S2, possess high electron affinities, which range from 3.51 to 3.64 eV at the CCSDT(T)//MP2 level. A sequential addition of a sulfur atom to the Ga2S n (n = 1–3) system increases the charge transfer from gallium atoms to sulfur atoms, the adiabatic electron affinity, and the HOMO–LUMO gap. The sufficiently large HOMO–LUMO gaps ensure the stability of these gallium sulfide clusters. The Ga2S4 → Ga2S2 + S2 process is the most thermodynamically favored toward dissociation.

The equilibrium structures of Te(CN)2, Te(CN)(NC), and Te(NC)2 and three isomerization reactions: Te(CN)2 ⇌ Te(CN)(NC), Te(CN)(NC) ⇌ Te(NC)2, and Te(CN)2 ⇌ Te(NC)2 were studied in the gas-phase using density functional theory. Three functionals (B3LYP, BLYP, and BHLYP) were employed to characterize the low-lying electronic singlet and triplet TeC2N2 isomers. The basis sets for carbon and nitrogen used were of double-ζ plus polarization quality with additional s- and p-type diffuse functions, DZP++. For the tellurium atom, the LANL2DZ (ECP) basis set was used. The energetic ordering (kcal mol−1) (B3LYP) including zero-point vibrational energy corrections for the singlet ground state isomers follows: Te(CN)2 (0.0, global minimum)

Push-pull chromophores attached to carbazole based π-conjugating spacers bearing N-alkylamino donors, cyanovinyl and carbethoxy acceptors have been studied by the means of UV-Visible measurements. The intramolecular charge transfer (ICT) of these π-conjugated systems has also been tested by investigating the ability of the solute molecules to undergo shifts in their fluorescence emission maxima with increasing solvent polarity. Density Functional Theory [B3LYP/6-31G(d)] and Time Dependent Density Functional Theory [TD-B3LYP/6-31G(d)] computations have been used to have more understanding of the structural, molecular, electronic and photophysical parameters of push-pull dyes. The largest wavelength difference between the experimental and computed electronic absorption maxima was 45 nm. For emission, a largest difference of 61 nm was observed. The ground state and excited state dipole moments in different solvents were determined using experimental solvatochromic data and computed Onsager radii. The dipole moments of the molecules in the excited state were observed to be higher than in the ground state.

A study of the Ga2Te3 and Ga3Te2 clusters is presented using three different levels of theory, namely; DFT, MP2 and CCSD(T). We used the 6-311G(d) basis set for gallium atom and the LANL2DZdp ECP basis set for tellurium atom. The results include geometrical parameters, vibrational frequencies and energies of the low-lying structures. We report the vertical electron detachment energy (VEDE) and adiabatic electron detachment energy (AEDE) for the anionic species. The neutral Ga2Te3 cluster adopts a V-shape configuration with 1A1 ground state whilst its anion is kite shaped with 2A1 ground state. On the other hand, the Ga3Te2 and Ga3Te2 ¯ species prefer a three dimensional 6-D3h geometry with 2A2″ and 1A1′ electronic states, respectively. The adiabatic electron affinity (AEA) for Ga2Te3 is 2.78 eV and that of Ga3Te2 is 2.86 eV at the CCSD(T)//B3LYP level. We analyse, discuss and compare the findings of our research with the analogous gallium chalcogenides.

We hereby report a theoretical study on the equilibrium geometries, electronic structures and harmonic vibrational frequencies of Ga2Se3, Ga3Se2 and their anions. The ground and low-lying excited states of Ga2Se 3 − , Ga2Se3, Ga3Se 2 − and Ga3Se2 are studied at the B3LYP and/or MP2 and CCSD(T) levels in conjunction with 6-311+G(d) and 6-311+G(2df) one particle basis sets. Ga2Se 2 − adopts the C2v kite geometry while Ga2Se3 has a ‘V’ geometry. Ga3Se 2 − has a three-dimensional ‘D3h ’ geometry and Ga3Se2 prefers the three-dimensional ‘C2v ’ structure. Electron detachment energies from the ground electronic states of the anions to several neutral states are reported and discussed. At CCSD(T)//MP2 level, the adiabatic electron affinity (AEA) of Ga2Se3 is calculated to be 3.23 eV when using the 6-311+G(2df) basis set and that of Ga3Se2 is 2.77 eV with the 6-311+G(d) basis set. The findings of this research are analyzed and compared with gallium oxide and sulfide analogues.

The gauche and trans rotamers of halogeno(halogenomethyl)silane (XSiH2CH2X; X = F, Cl, Br, I), fluoro(halogenomethyl)silane and halogeno(fluoromethyl)silane (SiH2F–CH2Y and SiH2Y–CH2F; Y = Cl, Br, I) have been studied in the gas phase using theoretical methods. The transition state arising from gauche-trans isomerization has also been modeled. The methods used are density functional theory (DFT) and second-order Moller–Plesset theory (MP2). B3LYP is the functional used for the DFT method. The basis set used is 6-311++G(d,p) for all atoms except that 6-311G(d,p) is used for the iodine atom only. The results indicate that the trans conformers are preferred in the gas phase and both energy difference and rotational barrier height increase as the size of the halogen increases. This study has been extended to include the solvent effect with the dielectric constant of the solvents varying from 2 to 80. The solvent effect was explored using Self-Consistent Reaction Field and the conformers have been fully optimized at the DFT/B3LYP level of theory. The net effect of a solvent is that energy difference decreases but the rotational barrier is not much affected. The findings from this work are explained in terms of different interactions and these are supported by a Natural Bond Orbital analysis.

A theoretical study of CnX, CnX+ and CnX- (X = O and Se; n = 1-10) clusters is carried out employing the density functional theory and the B3LYP functional. All species are fully optimized using the basis set 6-31G(d) for all atoms and further, single-point computations are done using the B3LYP/aug-cc-pVTZ level. Molecular properties such as equilibrium parameters, dipole moment, infrared vibrational frequencies, Raman activities and rotational constant are predicted. The computations indicate that the equilibrium structures are either linear or quasi-linear. We report the different forms of electron affinities, ionization energy, atomization energy and binding energy of the CnO and CnSe chains. The results indicate parity effect is very apparent for electron affinity, ionization energy, and binding energy but the effect is less pronounced for atomization energy. The n-even linear chains have larger ionization energy and atomization energy than the n-odd ones but this effect is reversed for electron affinity. The findings from this work are critically discussed and they are very similar to those obtained previously for the hetero-atom doped carbon chains. This research indicates that n-odd carbon chains are more stable than n-even and this is the trend for the chalcogens carbon chains.

This is a gas-phase study of the gauche and trans conformers of 1-bromo-2-iodoethane. The methods used are the second-order Moller-Plesset theory (MP2) and density functional theory (DFT). The functional used for the DFT method is B3LYP and the basis sets used are 6-311++G(d,p) for all atoms except that different basis sets, namely 3-21G, LANECP, CRENBL ECP, Stuttgart RLC ECP and 6-311G(d,p), have been explored for the iodine atom. The results indicate that the trans conformer is preferred. The energy difference between the gauche and trans conformers (ΔE g−t) and related thermodynamic parameters are reported. The ΔE g−t values are 12.50 kJ⋅mol−1 (B3LYP) and 10.00 kJ⋅mol−1 (MP2) with the basis sets being 6-311++G(d,p)[C,H,Br]/6-311G(d,p)[I]. The conformers of 1-bromo-2-iodoethane have also been subjected to vibrational analysis. The results from the two theoretical levels are in good agreement but they are not much affected by the basis set of the iodine atom. The study has been extended to explore solvent effects using Self-Consistent Reaction Field methods. The structural parameters of the conformers are little affected by the polarity of the solvent but ΔE g−t decreases and the solvation Gibbs energy increases with increasing polarity of the solvent.

This work compares the performance of theoretical methods and basis sets on the molecular structure, atomisation and ionisation energies, electron affinity, and vibrational spectrum of silylene. Silylene, its cation and anion have been studied in 1 A 1, 2 A 1 and 2 B 1 states, respectively, in the gas phase and C2v symmetry. The methods considered are second-order Moller-Plesset perturbation theory (MP2), the density functional theory (DFT), Gaussian-2 (G2) and complete basis set methods (CBS-4M and CBS-Q). The basis sets used are 6-31G(d,p), 6-311G(d,p), 6-31++G(d,p) and 6-311++G(d,p). The functional used for the DFT method is B3LYP. Silylene and its cation and anion have been optimised using the MP2 and DFT methods and the named basis sets. Single-point energy calculations (G2, CBS-4M and CBS-Q) were performed using MP2/6-311++G(d,p) structures and these energies have been used to calculate atomisation energy, ionisation energy and adiabatic electron affinity. Frequency calculations were also done and the raw vibrational frequencies were assigned. It is interesting to note the close similarity between the predicted parameters and some of the available literature values. The results obtained are consistent and converge with different basis sets with improved size and quality. However, the parameters obtained are very much method dependent.

It is not difficult to balance chemical equations and thus it is hardly given more thoughts. However, there is a mathematical principle for the balancing of chemical equations and this principle may be used for automation. The balancing of chemical equation is carried out, by formulating a reaction matrix and the latter is used in a matrix equation. The matrix equation is then solved to obtain the balancing coefficients. The conventional matrix inverse method cannot always be used and hence the solution is obtained by row reduced operations. These operations and any matrix manipulation are carried out with Matlab. Further this novel method can be used to classify chemical equations as nonfeasible, unique and nonunique.

Cycloaddition reactions represent one of the most powerful processes in organic chemistry. The most common types of cycloaddition reactions are the Diels-Alder (DA) and the 1,3-dipolar cycloaddition reactions (1,3-DCs) which lead to five and six membered rings, respectively. In our ongoing efforts to contribute to the understanding of DA and 1,3-DCs; we studied the following using the B3LYP/6-31G(d) level of theory: 1. The 1,3-DCs of the pyridinium-3-olates and pyrazinium-3-olates with methyl acrylate and methyl methacrylate [1,2]. 2. The competitive hetero-DA and 1,3-DCs of methyl glyoxylate oxime and its tautomeric nitrone with cyclopentadiene in the absence and in the presence of BF3 as a Lewis acid catalyst [3]. 3. A systematic study on the 1,3-DCs of C60 with substituted nitrile oxides (RCNO; R = F, Cl, Br, NC, CN and NO2) [4]. Among the outcomes of our investigations is the successful use of theoretical methods to understand the regio- and stereoselectivity of the reactions considered. It is expected that experimentalists find the results useful for synthesis involving these moieties and cycloaddition reactions. This presentation will overview our ongoing research program to have more understanding of these cycloaddition reactions.

Theoretical methods (DFT/B3LYP and MP2) have been used to optimize the geometries of the Al x Sb y (x + y = 3, 5) clusters and their anions. Single point energy computations at CCSD(T) level have also been performed using the optimized B3LYP and MP2 structures. The basis sets used for Al and Sb atoms are 6-311+G(2d) and LANL2DZdp ECP, respectively. Harmonic vibrational frequency computations were carried out to confirm the nature of the stationary points. We report the structural and spectroscopic parameters of the named clusters. We also report the relative energy of the clusters, the vertical electron detachment energy, the adiabatic electron detachment energy and the adiabatic electron affinity. The most stable structures at the CCSD(T)//MP2 level are, the D ∞h linear structure (AlSb2) and the C 2v V-bent structure (AlSb 2 − ), the C 2v V-bent structure (Al2Sb and its anion), the C 2v edge-capped tetrahedron (Al2Sb3 and its anion), the C 2v trigonal bipyramidal structure (Al3Sb2 and its anion), the C 4v square pyramidal (AlSb4) and a C 2v ground structure for its anion, the C 2v planar trapezoidal structure (Al4Sb) and the C 2v edge-capped tetrahedron (Al4Sb−). The adiabatic electron affinities calculated at the CCSD(T)//MP2 level are 2.17 eV (AlSb2), 2.17 eV (Al2Sb), 2.38 eV (Al2Sb3), 2.76 eV (Al3Sb2), 2.21 eV (AlSb4) and 2.03 eV (Al4Sb). The findings of this research are analysed, discussed and compared with the analogous picnogenides clusters.

A systematic investigation of the X2CTe and XYCTe (X,Y = H, F, Cl, Br, I and CN) species is carried out using the second-order Moller–Plesset perturbation theory and density functional theory. The basis sets used for all atoms (except iodine and tellurium) in this work are of double-ζ plus polarization quality with additional s- and p-type diffuse functions and denoted DZP++. The LANL2DZdp ECP and 6-311G(d,p) basis sets are used for tellurium and iodine. Vibrational frequency analyses are performed to evaluate zero-point energy corrections and to determine the nature of the stationary points located. The ionization potentials (IPad and IPad(ZPVE)), the four different forms of neutral–anion separations (EAad, EAad(ZPVE), VEA and VDE), the singlet–triplet splittings as well as the HOMO–LUMO gaps are predicted. The electronegativity (χ) reactivity descriptor for the halogens (F, Cl, Br and I) and the calculated Mulliken’s electronegativity are used as tools to assess the interrelated properties of these telluroformaldehyde derivatives. The predicted IPad(ZPVE) values with the B3LYP functional range from 7.89 [I2CTe] to 9.16 eV [F(NC)CTe], the EAad(ZPVE) ranges from 1.29 [I2CTe] to 3.34 eV [(NC)2CTe], the singlet–triplet splitting ranges from 0.64 [H(NC)CTe)] to 1.85 eV [F2CTe], and the HOMO–LUMO gap ranges from 2.21 [H(NC)CTe] to 3.42 eV [F2CTe]. The HOMO–LUMO gap is found to be proportional to the singlet–triplet splitting. The results obtained are critically analyzed and discussed. This research is also compared with analogous studies of formaldehyde, thioformaldehyde and selenoformadehyde.