Computational studies of metal carbonyl complexes of 3[4-ethyl(phenly)imino][indoline-2-one] and 3[4-butyl(phenly)imino][indoline-2-one]

Use and application of Schiff bases are extended to many different fields of technology. (ISE)M(CO)₅ complex [M?=?Cr (1), Mo (2), W (3), and where ISE is 3[4-ethyl(phenly)imino][indoline-2-one]; and (ISB)M(CO)₅ [M?=?Cr (4), Mo (5), W (6)], where ISB is 3[4-butly(phenly)imino][indoline-2-one] were investigated by computational methods. Computations were carried out using density functional theory (DFT) with B3LYP and CAM-B3LYP functionals, in conjunction with LanL2DZ basis set for metals and cc-PVTZ basis set for other atoms. Time-dependent density functional theory (TDDFT) was used at the same level to obtain the electronic transitions. Molecular orbital energies, UV-Vis spectra, and total electron densities of investigated molecules were shown in the gas phase and in THF. Metal complexes showed higher absorption coefficients compared to ISE and ISB in the visible region. Additionally, they displayed absorption peaks at longer wavelengths and full MLCT character in solution, and W complexes required less energy compared to the complexes of other investigated metal ions. Among the investigated systems, (ISE)W(CO)₅ and (ISB)W(CO)₅ complexes with lowest HOMO-LUMO gaps are found to be the best candidates for photosensitive material production.

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Graphical Abstract UV-Vis absorption spectra of ISE and (ISE)W(CO)₅

     

A B3LYP and MP2 theoretical investigation into host-guest interaction between calix[4]arene and Li+ or Na+

The DFT-B3LYP and MP2 methods with 6-311G** and 6-311++G** basis sets have been applied to study the complexation energies of the host-guest complexes between the cone calix[4]arene and Li⁺ or Na⁺ on the B3LYP optimized geometries. A comparison of the complexation energies obtained from the MP2(full) with those from MP2(fc) method is also carried out. The result shows that it is essential to introduce the diffuse basis set into the geometry optimizations and complexation energy calculations of the alkali-metal cation-π interaction complexes of calix[4]arene, and the D _e values show a maximum of 21.13 kJ mol⁻¹ (14.45% of relative error) between the MP2(full)/6-311++G** and MP2(fc)/6-311++G** method. For Li⁺ cation, the complexation is mainly energetically stabilized by the lower rim/cation (namely O–Li⁺) interaction. However, binding energies and NBO analyses confirm that Na⁺ cation prefers to enter the calix[4]arene cavity and the cation-π interaction is predominant, which contradicts the previous low-level theoretical studies. Furthermore, the complexation with Li⁺ is preferred over that with Na⁺ by at least 12.70 kJ mol⁻¹ at MP2(full)/6-311++G**//B3LYP/6-311++G** level.      

Density functional computations of enantioselective alkynylation of aldehyde catalyzed by chiral zinc(II)-complexes

The enantioselective alkynylation of aldehyde catalyzed by chiral zinc(II)-complexes was studied by means of the density functional theory (DFT). All the structures were optimized completely at the B3LYP/6-31G(d,p) level. To obtain more exact energies, single-point energy calculations at B3LYP/6-31+G(d,p) level were carried out on the B3LYP/6-31G(d,p) geometries. As shown, this enantioselective alkynylation was endothermic. The chirality-determining step for the alkynylation was the formation of the catalyst–ethanol complexes and the transition states for this step involved a six-membered ring. The dominant products predicted theoretically were of (R)-chirality, in good agreement with experiment.      

Alpha particle chemistry. On the formation of stable complexes between He2+ and other simple species: implications for atmospheric and interstellar chemistry

The possibility that stable complexes may be formed between alpha particles (He²⁺) and small molecules is investigated using QCISD quantum mechanical calculations. Implications for their presence in the terrestrial atmosphere and/or in interstellar space are discussed. Figure Optimized structure of a stable H₂OHe²⁺ complex     

ONIOM DFT/PM3 calculation on the interaction between STI-571 and abelson tyrosine kinase

The ONIOM2 (B3LYP/6–31G (d, p): PM3) and B3LYP/6–31G (d, p) methods were applied to investigate the interaction between STI-571 and abelson tyrosine kinase binding site. The complex of N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)- phenyl]-benzamide (part of STI-571) and related 16 amino acid residues were found at B3LYP/6–31G (d, p) level to have hydrogen bonds and π....π stacking interaction, their binding energy via HAF optimization was −20.4 kcal mol⁻¹. The results derived from this study agreed well with the reported observation. Figure Optimized structure of STI-571 and Thr315 in abelson tyrosine kinase based on ONIOM2 method     

Dual-rhodamine urea derivative, a novel chemidosimeter for Hg(II) and its application in imaging Hg(II) in living cells

Abstract  The synthesis and spectral properties of a chemidosimeter 1,4-di[2-(6-ethylamino-3-ethylimino-2,7-dimethyl-3H-xanthen-9-yl) benzoic acid (aminomethyl)-3-phenylthiourea] benzene (1) for Hg(II) ions are reported, and it has been demonstrated that 1 can be used as a fluorescent probe for monitoring Hg(II) ions in living cells. Graphical abstract  A highly sensitive fluorescent probe (1) was developed as a fluorescent and colorimetric chemodosimeter in dimethyl sulfoxide/methanol solution with a broad pH range (pH 5–10) and high selectivity toward Hg²⁺ ions but no significant response toward other competitive cations. Furthermore, by means of confocal laser scanning microscopy experiments, it is demonstrated that 1 can be used as a fluorescent probe for monitoring Hg²⁺ in living cells. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

The platinum-olefin binding energy in series of (PH<Subscript>3</Subscript>)<Subscript>2</Subscript>Pt(olefin) complexes - a theoretical study

Theoretical investigation of Pt(0)-olefin organometallic complexes containing tertiary phosphine ligands was focused on the strength of platinum-olefin electronic interaction. DFT theoretical study of electronic effects in a substantial number of ethylene derivatives was evaluated in terms of the Pt-olefin binding energy using MP2 correlation theory. Organometallics bearing coordinated olefins with general formula (R¹R²C = CR³R⁴)Pt(PH₃)₂ [R = various substituents] had been selected, including olefins containing both electron-donor substituents as well as electron-withdrawing groups. The stability of the corresponding complexes increases with a strengthening electron-withdrawal ability of the olefin substituents. Figure Representation of (CH₂ = CHR)Pt(PPh₃)₂ and the stability chart     

Exploring the potential energy surface of novel [H,S, Se,Br] species: a high level first principle study

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.

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Graphical abstract Relative energy profile (in kcal mol^?1) using the CCSD(T)/CBS and MP2/CBS (in parentheses) method of the stationary states on the [H, S, Se, Br] PES.

     

Molecular model for host–guest interaction of tetraamino-<Emphasis Type="Italic">tert</Emphasis>-butylthiacalix[4]arene and tetraamino-<Emphasis Type="Italic">tert</Emphasis>-butylcalix[4]arene receptors with carboxylate and dicarboxylate guests: an ONIOM study

Geometry optimizations of tetraamino-tert-butylthiacalix[4]arene (tatbtc4a) and tetraamino-tert-butylcalix[4]arene (tatbc4a) complexes with acetate, oxalate, malonate, succinate, glutarate, adipate, and pimelate were carried out using the integrated MO:MO method. Thermodynamic quantities, preorganization energies and complexation energies of these complexes were obtained at the ONIOM(B3LYP/6-31G(d):AM1) level of theory. The relative stabilities of the tatbtc4a and tatbc4a complexes with carboxylate guests are reported. The complexes tatbtc4a/malonate and tatbc4a/oxalate were found to be the most stable species. The selectivity of the tatbtc4a receptor toward to malonate with respect to oxalate, in terms of selectivity coefficient, is 9.90×10². Figure Atom labeling of tatbtc4a/oxalate complex as a representative of host-guest system.     

Theoretical study on the ground state intramolecular proton transfer (IPT) and solvation effect in two Schiff bases formed by 2-aminopyridine with 2-hydroxy-1- naphthaldehyde and 2-hydroxy salicylaldehyde

The tautomerization mechanism the isolated and monohydrated forms of two Schiff bases 1 and 2, and the effect of solvation on the proton transfer from enol-imine form to the keto-enamine form have been investigated using the B3LYP hybrid density functional method at the 6-31G** basis set level. The barrier heights for H₂O-assisted reactions are significantly lower than that of unassisted tautomerization reaction in the gas phase. Nonspecific solvent effects have also been taken into account by using the continuum model (IPCM) of four different solvent. The tautomerization energies and the potential energy barriers are decreased by increasing solvent polarity. Figure The tautomerization mechanism the isolated and monohydrated forms of two Schiff bases 1 and 2, and the effect of solvation on the proton transfer from enol-imine form to the keto-enamine form have been investigated using the B3LYP hybrid density functional method at the 6-31G** basis set level     

Theoretical study on the thermal decomposition of model compounds for Poly (dialkyl fumarate)

The thermal decomposition of model compounds for poly (dialkyl fumarate) was studied by using ab initio and density functional theory (DFT) calculations. To determine the most favorable reaction pathway of thermal decomposition, geometries, structures, and energies were evaluated for reactants, products, and transition states of the proposed pathways at the HF/6-31G(d) and B3LYP/6-31G(d) levels. Three possible paths (I, II and III) and subsequent reaction paths (IV and V) for the model compounds of poly (dialkyl fumarate) decomposition had been postulated. It has been found that the path (I) has the lowest activation energy 193.8 kJ mol⁻¹ at B3LYP/6-31G(d) level and the path (I) is considered as the main path for the thermal decomposition of model compounds for poly (dialkyl fumarate).      

Probing the coordination properties of glutathione with transition metal ions (Cr2+,Mn2+,Fe2+,Co2+, Ni2+,Cu2+,Zn2+,Cd2+,Hg2+) by density functional theory

Complexes formed by reduced glutathione (GSH) with metal cations (Cr²⁺, Mn²⁺,Fe²⁺,Co²⁺,Ni²⁺,Cu²⁺,Zn²⁺,Cd²⁺,Hg²⁺) were systematically investigated by the density functional theory (DFT). The results showed that the interactions of the metal cations with GSH resulted in nine different stable complexes and many factors had an effect on the binding energy. Generally, for the same period of metal ions, the binding energies ranked in the order of Cu²⁺>Ni²⁺>Co²⁺>Fe²⁺>Cr²⁺>Zn²⁺>Mn²⁺; and for the same group of metal ions, the general trend of binding energies was Zn²⁺>Hg²⁺>Cd²⁺. Moreover, the amounts of charge transferred from S or N to transition metal cations are greater than that of O atoms. For Fe²⁺,Co²⁺,Ni²⁺,Cu²⁺,Zn²⁺,Cd²⁺ and Hg²⁺ complexes, the values of the Wiberg bond indices (WBIs) of M-S (M denotes metal cations) were larger than that of M-N and M-O; for Cr²⁺ complexes, most of the WBIs of M-O in complexes were higher than that of M-S and M-N. Furthermore, the changes in the electron configuration of the metal cations before and after chelate reaction revealed that Cu²⁺, Ni²⁺,Co²⁺ and Hg²⁺ had obvious tendencies to be reduced to Cu⁺,Ni⁺,Co⁺ and Hg⁺ during the coordination process.     

Theoretical study on the series of [Au3Cl3M2] complexes, with M = Li, Na, K, Rb, Cs

The prediction of the series of complexes [Au₃Cl₃M₂] with M = Li, Na, K, Rb and Cs, has been achieved at the ab initio level of theory. All geometries were fully optimized at the MP2 level of theory; the central Au₃ cluster is capped by chlorine atoms and the alkaline metals lie above and below the plane of the central ring; aurophilic interactions were found on the metal cluster, and also a strong aromatic character coming from the delocalized d-electrons of the Au atoms according to nuclear independent chemical shift calculations. On the other hand, the chemical hardness parameter was used to test the stability of the series of complexes, and the Fukui indexes of electrophilic and nucleophilic attack were employed to explore possible sites where chemical reactivity may play a role. Figure Molecular representations of the series of complexes [Au₃Cl₃M₂] (M = Li, Na, K, Rb, Cs) and their corresponding chemical hardness     

Optical chemosensors for Cu(II) ion based on BODIPY derivatives: an experimental and theoretical study

Two BODIPY derivatives for Cu²⁺ ion chemosensors containing 4-[2-(diethylamino)-2-oxoethoxy]phenyl (BDP1) and 3,4-bis[2-(diethylamino)-2-oxoethoxy]phenyl (BDP2) were synthesized by coupling appropriate N,N-diethyl-2-(4-formylphenoxy)acetamide and 2,4-dimethylpyrrole moieties in the presence of trifluoroacetic acid and anhydrous dichloromethane at room temperature. The binding abilities between these chemosensors and 50 equivalents of Na⁺, K⁺, Ag⁺, Ca²⁺, Fe²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺ and Pb²⁺ ions were studied using UV-vis and fluorescence spectrophotometry. The results show that, compared to other ions, both the UV-vis absorption and fluorescence emission intensity of BDP2 decreased dramatically when Cu²⁺ ion was added. To explain this behavior, ab initio quantum chemical calculations were performed using correlated second-order Møller-Plesset perturbation theory (MP2/LanL2DZ). The calculated orbital energies indicated that the decrease in UV-vis absorption intensity and the quenching of fluorescene emission were due to the single-electron reduction of Cu²⁺ to Cu⁺ ion.

Theoretical study of the hydrogen-bonded complexes serotonin–water/hydrogen peroxide

Eight H-bonded complexes between serotonin (5-hydroxy-tryptamine) and water/hydrogen peroxide were studied at the B3LYP and HF levels of theory, using the 6-31+G(d) basis set. A thermodynamic analysis was performed in order to find the most stable complex. The calculated bonding parameters showed that the most stable H-bonded complex is formed between serotonin and hydrogen peroxide by means of the intermolecular H-bond –H₂N...H–OOH. Fig. a Theoretical study of the hydrogen-bonded supersystems serotonin-water/hydrogen peroxide     

Formation and isomerization of dicyclopenta[de,mn]anthracene. Electronic Structure Study

The formation of dicyclopenta[de,mn]anthracene (P1) and its isomerization into dicyclopenta[jk,mn]phenanthrene (P3) was investigated using density functional theory. It was shown that P1 is formed from 1,4-diethynilanthracene, but due to its instability, it undergoes further transformation. This transformation involves rearrangements of some hydrogen atoms and ring contraction/ring expansion process, yielding as a final product the isomer P3. The energies of activation for the P1→P3 intraconversion show that this reaction is competitive to the other, previously investigated isomerization of P1 into dicyclopenta[de,kl]anthracene (P2). In addition, our investigation shows that the formation of P3 from P1 is energetically more favorable than the formation of P3 from P2. Thus, the presence of the isomer P3 in the reaction mixtures could also be caused by the isomerization of the very unstable isomer P1. Figure Isomerization of 1,4-diethynilanthracene to dicyclopenta[jk,mn]phenanthrene via dicyclopenta[de,mn]anthracene Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Aromaticity and electronic properties of Heterosuperbenzene (Heterohexabenzocoronene)

A global electrophilicity parameter and the aromaticity of some heterocyclic polyaromatic hydrocarbons were evaluated on the basis of DFT calculations. The substitution of carbon atoms by nitrogen atoms dramatically changes the global electrophilicity of the molecules, with the fully substituted molecule being the most electrophilic with a reactivity very close to that of fullerene. Figure Fully substituted heterohexabenzocoronene Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

An experimental and theoretical study of the enantioselective deprotonation of cyclohexene oxide with isopinocampheyl-based chiral lithium amides

The mechanism of the enantioselective deprotonation of cyclohexene oxide with isopinocampheyl-based chiral lithium amide was studied by quantum chemical calculations. The transition states of eight molecules were fully optimized at the ab initio HF/3-21G and density functional B3LYP/3-21G levels with Gaussian 98. The activation energies were calculated at the B3LYP/6-31+G(3df,2p)//B3LYP/3-21G level. We found the theoretical evaluation to be consistent with the experimental data. At the best case, an enantiomeric excess of up to 95% for (R)-2-scyclohexen-1-ol was achieved with (−)-N, N-diisopinocampheyl lithium amide. Enantioselective deprotonation of cyclohexene oxide Electronic Supplementary Material Supplementary material is available for this article at Dedicated to Professor Dr. Paul von Ragué Schleyer on the occasion of his 75th birthday.     

The zinc complex catalyzed hydration of alkyl isothiocyanates

Based upon our preceding studies of the hydration of CO₂, COS and CS₂, accelerated by the carbonic anhydrase (CA) using simplified [ZnL₃OH]⁺ complexes as model catalysts, we calculated the hydration mechanisms of both the uncatalyzed and the [ZnL₃OH]⁺-catalyzed reactions (L = NH₃) of isothiocyanates RNCS on the B3LYP/6-311+G(d,p) level of theory. Interestingly, the transition state for the favored metal mediated reaction with the lowest Gibbs free energy is only slightly higher than in the case of CO₂ (depending on the attacking atom (N or S). Calculations under inclusion of solvent corrections show a reduction of the selectivity and a slight decrease of the Gibbs free energy in the rate-determining steps. The most plausible pathway prefers the mechanism via a Lindskog proton-shift transition state leading to the thermodynamically most stable product, the carbamatic-S-acid. Furthermore, powerful electron withdrawing substituents R of the cumulenic substrates influence the selectivity of the reaction to a significant extent. Especially the CF₃-group in trifluoromethylisothiocyanate reverses the selectivity. This investigation demonstrates that reaction principles developed by nature can be translated to develop efficient catalytic methods, in this case presumably for the transformation of a wide variety of heterocumulenes aside from CO₂, COS and CS₂. Figure Competing transition structures for the [ZnL₃OH]⁺-mediated activation of isothiocyanates Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.