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The discovery and introduction of the switchSense technique in the chemical laboratory have drawn well-deserved interest owing to its wide range of applications. Namely, it can be used to determine the diameter of proteins, alterations in their tertiary structures (folding), and many other conformational changes that are important from a biological point of view. The essence of this technique is based on its ability to study of the interactions between an analyte and a ligand in real time (in a buffer flow). Its simplicity, on the other hand, is based on the use of a signaling system that provides information about the ongoing interactions based on the changes in the fluorescence intensity. This technique can be extremely advantageous in the study of new pharmaceuticals. The design of compounds with biological activity, as well as the determination of their molecular targets and modes of interactions, is crucial in the search for new drugs and the fight against drug resistance. This article presents another possible application of the switchSense technique for the study of the binding kinetics of small model molecules such as ethidium bromide (EB) and selected sulfonamide derivatives with DNA in the static and dynamic modes at three different temperatures (15, 25, and 37 °C) each. The experimental results remain in very good agreement with the molecular dynamics docking ones. These physicochemical insights and applications obtained from the switchSense technique allow for the design of an effective strategy for molecular interaction assessments of small but pharmaceutically important molecules with DNA.

Isothermal titration calorimetry, circular dichroism (CD) techniques, and

The dipole-bound anions of pyridine, pyridazine, and pyrimidine are characterized using equation of motion coupled cluster singles and doubles calculations. These calculations predict that the anions of pyridine, pyrimidine and pyridazine are bound in the Born-Oppenheimer approximation by 0.05, 0.8, and 19.0 meV, respectively. The binding energies of pyrimidine and pyridazine are large enough that the anions will remain bound even when allowing for corrections to the Born-Oppenheimer approximation, while that of pyridine is a borderline case. We were unable to find a stable non-valence correlation-bound anion for pyrazine, which has a zero dipole moment.

Carborane Bronsted superacids have proven to be useful reagents in a variety of organic and inorganic synthetic processes. In this work, analogs in which the icosahedral CB11 carborane core is replaced by a CAl11 core are studied using ab initio electronic structure tools. Each so-called caralumane Bronsted acid is formed by adding HF, HCl, or HH to a corresponding caralumane Lewis acid possessing a vacant Al-centered orbital that acts to accept an electron pair from the HF, HCl, or HH. The Lewis acid strengths of the species involved, as measured by their F- ion affinities, are all found to exceed the threshold for labeling them Lewis superacids. Also, the deprotonation Gibbs free energies of the Bronsted acids are found to be small enough for them to be Bronsted superacids. When HF or HCl is bound to a caralumane Lewis acid to form the Bronsted acid, the HF or HCl is bound datively to a single Al atom, and hydrogen bonds can be formed between this molecule's H atom and nearby F or Cl atoms attached to other Al atoms. In contrast, when HH is bound to the Lewis acid to form the Bronsted acid, two novel low-energy structures arise, both of which are Bronsted superacids. One has an essentially intact HH molecule attached to a single Al atom in a η2 fashion. In the other, the HH molecule is heterolytically cleaved to generate a hydride ion that attaches to a single Al atom and a proton that binds in a multicenter manner to other Al atoms. The structures and relative energies of a multitude of such caralumane Lewis and Bronsted superacids are provided and discussed.

The metal cations-polysaccharides complexes play crucial roles in the process of immune cell recognitions. Here, we create simpler biomimetic ligands, which emulate binding of carbohydrates in living organisms. We present a detailed study on the interactions of Cu2+, Ni2+ and VO2+ ions with t-butyl 3-azido- and 3-amino-2,3-dideoxy-α-d-arabino-hexopyranosides. NMR, IR and UV–Vis spectroscopies as well as single crystal X-ray diffraction were used for the ligand structure determinations and showed their binding affinity of ions selected. The formation of stable complexes of Cu(II), Ni(II), VO(IV) ions and saccharides with 1:1, 1:2 and 1:3 molar ratios was proved. The coordination sites proposed are N-donor (amino or azido groups), O-donor (hydroxyl group) and endo-oxygen atoms. Additionally, parameters like shape, charge density distribution, and sites of chemical reactivity of the sugars studied were obtained by mapping electron density isosurface with electrostatic potential (MESP).

Four sulfonamide derivatives with a methoxyphenyl moiety, namely N-{4-[(2-methoxyphenyl)sulfamoyl]phenyl}acetamide (1a), N-{4-[(3-methoxyphenyl)sulfamoyl]phenyl}acetamide (1b), 4-amino-N-(2-methoxyphenyl)benzenesulfonamide (2a) and 4-amino-N-(3-methoxyphenyl)benzenesulfonamide (2b), have been synthesized and characterized physiochemically by CHNS, MS, FT-IR, 1H NMR, 13C NMR, PXRD and TG methods. Crystal structures were determined by SC-XRD and their conformational and noncovalent interaction properties were examined by both experimental and theoretical (HS, MEPS, NBO, dimerization energy, QTAIM) methods. The conformational flexibility of the bridge connecting two phenyl rings was studied and minimum-energy conformations were theoretically found. The packing architecture and hydrogen bond networks were described by graph set notation. Hirshfeld surface analysis revealed regions of stronger contacts and allowed us to indicate the relative contributions of different noncovalent contacts in the crystal packing. MEPS calculations helped to distinguish the electron rich and electron poor regions and to find the best H-bond donors and acceptors. The use of the QTAIM method enabled us to explain the influence of functional groups and molecular arrangement on the strength of noncovalent interactions in the crystals and overall packing efficiency.

The acid strength of the datively bound HF → AlX3 complexes (X H, F, N3, CH3, CH CH2, C CH, C6H5, CN, CF3, OF, SH, SF, NCO, NCS, OCF3, and OSF5) is evaluated on the basis of theoretical calculations employing ab initio methods. It is demonstrated that the resulting acidity of HF → AlX3 depends strongly on the electron affinity of the X substituents as the effectiveness of the electron density withdrawal from the HF component towards the AlX3 component is related to the ability of the HF → AlX3 complex to donate a proton.

Grignard reagents are commonly used in organic synthesis, yet their ability to form stable anionic states has not been recognized thus far. In this work, representative examples of RMgF, RMgCl, and RMgBr molecules involving methyl, ethyl, and phenyl functional groups serving as R substituents are investigated regarding their equilibrium structures, adiabatic electron affinities, and vertical electron detachment energies of their daughter anions. The electronic stabilities determined for the negatively charged Grignard compounds are then compared to those predicted for their corresponding magnesium halides. The anions formed by RMgX (R = Me, Et, Ph; X = F, Cl, Br) molecules are found to be adiabatically electronically stable valence-bound systems characterized by relatively large vertical electron detachment energies spanning the 0.79-1.62 eV range. In addition, significant structural relaxation upon attachment of an excess electron is predicted for all Grignard compounds considered. Furthermore, the re-examination of the anions formed by magnesium halides resulted in recognizing them as valence-bound rather than dipole-bound anions, in contrast to the earlier interpretations.

The possible formation of the (AlF4(HF)n)− (n = 1–8 and 12), (AsF6(HF)n)−, and (SbF6(HF)n)− (n = 1–6 and 12) anionic clusters of a superhalogen nature is predicted in the solutions of binary HF/AlF3, HF/AsF5, and HF/SbF5 Lewis–Bronsted superacids on the basis of ab initio calculations. Our results show that all systems investigated represent extremely strongly bound anions characterized by vertical electron detachment energies (VDEs) that significantly exceed 10 eV. The VDE values estimated for the (AlF4(HF)12)−, (AsF6(HF)12)−, and (SbF6(HF)12)− systems are predicted to be 13.96, 14.03, and 14.03 eV, respectively, and are the largest vertical electron detachment energies reported in the literature thus far.

The acid strength of the datively bound X → AlF3 complexes (X = HF, HCl, H2S, AsH3, PH3, NF2H, NFH2, NH3, and H2O) is evaluated on the basis of theoretical calculations employing ab initio methods. Significant enhancement of the X acidity upon the formation of X/AlF3 compounds is predicted. It is demonstrated that even the non-acidic molecules X (e.g., H2O, NH3) combined with AlF3 are expected to form the X → AlF3 complexes characterized by the acid strength comparable or larger than that of H2SO4.

The pyrazine-2-thiocarboxamide (PTCA) as a pyrazine derivative with proven antifungal properties has for the first time been the subject of extensive research to evaluate its physicochemistry and ability to interact with biomolecules. The complete physicochemical and electrochemical profile of the studied compound together with its ionic species assignment were established as well as reported. The electrochemical characteristic of PTCA was examined in both: aqueous and aprotic solvent using the cyclic voltammetry technique. All the experimental results obtained were supported and compared with the DFT calculations. Furthermore, the pH effect on the redox processes and PTCA spectroscopic properties were also studied. The pKa values of the compound were determined using combined potentiometric and spectrophotometric/voltammetric (micro)titration methods. The detailed analyses of the PTCA's affinity to Calf thymus DNA and to Bovine Serum Albumin considered in scientific assay as potential cellular targets were the most important parts of the presented study. Indeed, a possible intercalation interaction mode was demonstrated for PTCA-DNA system studied by both spectrophotometric and electrochemical data which has never been reported before. Interestingly, values received by using the broad spectrum of techniques with different, individual measurable parameters have been showed a good agreement compared.

Ab initio methods with flexible orbital basis sets are used to examine the electron binding strengths of tri-fluorides, tri-chlorides, and tri-hydrides of B, Al, and Ga. The adiabatic electron affinities are found to increase with increasing atomic number of the central atom. For any given central atom M (M = B, Al, Ga), the adiabatic and vertical electronic stability for MCl3 is larger than that of the corresponding MF3. The tri-hydrides have quite different electron binding strengths than the corresponding tri-halides. BH3 has a very small EA (ca. 0.02 eV) and its anion is planar whereas the tri-halide anions and AlH3− and GaH3− are non-planar. AlH3 and GaH3 have considerably smaller EAs (ca. 0.3 eV) than the Al and Ga tri-halides (0.9–1.8 eV). In all, these anions provide species whose electron binding strengths span a considerable range (0.3–1.8 eV).

The mechanism of the (CH3)2CCH2+H2O→(CH3)3COH reaction catalyzed by two strong acids (H2SO4 and HSbF6) was investigated theoretically using the ab initio MP2 and CCSD(T) methods and the aug-cc-pVDZ/LANL2DZ and aug-cc-pVTZ/LANL2DZ basis sets. The effects of surrounding solvent molecules were approximated by employing the polarized continuum solvation model. The most important findings include the observation that both acids are capable of catalyzing isobutene hydration but the reaction is predicted to proceed faster when the HSbF6 superacid plays the catalyst role.

Theoretical investigation of the H(CHB11 X11 ) (X=H, F, Cl, CN), H(CHB11 Xn Y11-n ) (X,Y=F, Cl; n=1,5), and dimeric (H(CHB11 X11 ))2 (X=F, Cl) carborane superacids performed at the B3LYP/6-311++G(d,p) theory level revealed the similarity of their equilibrium structures and the possibility of nearly barrierless hydrogen atom migration among the substituents attached to one side of the icosahedral CB11 cage. The vertical electron detachment energies predicted at the OVGF/6-311++G(3df,2pd) theory level for the conjugate bases (CHB11 X11 )- were found to span the 5.82-9.00 ev range. The acid strengths (manifested by the Gibbs free deprotonation energies spanning the 213-266 kcal/mol range) predicted for the icosahedral H(CHB11 X11 ) carborane systems confirm their superacidic properties which might be increased even further by the attachment of the second carborane H(CHB11 X11 ) unit that leads to a dimeric structure mimicking a part of an experimentally observed H-bridged polymeric chain. The Gibbs free deprotonation energy of the dimeric (H(CHB11 Cl11 ))2 acid was predicted to be smaller by 17 kcal/mol than that of the corresponding monomeric H(CHB11 Cl11 ) acid.

The possibility of modifying (for computational purposes only) the IR νNH acidity scale based on the analysis of the ν(N–H) stretching vibration in the (C8H17)3N+H···A− salts (where A− stands for a deprotonated HA acid whose acidity is being investigated) is discussed. Simple alkyl groups (C3H7 and C4H9) are proposed to replace the relatively long and flexible octyl substituents in the R3N+H cations which the A− anions are combined with. The predictive ability of such modified IR νNH acidity scale and its usefulness for computational applications are verified for representative strong mineral acids (including superacids) and variously substituted carborane superacids.

Green and sustainable chemistry approaches necessitate an ongoing investigation towards new, environmentally benign and selective catalysts. We have thus prepared a new benzothiazole-scaffolded hydrazone Schiff base ligand L and coordinated it with copper(II) ions leading to five different complexes, the form of which in the solid state is counterion-dependent. Nitrate, chloride and triflate anions lead to monometallic species, whereas utilization of sulfates and tetrafluoroborates is responsible for the formation of bimetallic assemblies. The catalytic efficiency of synthesized compounds was shown in Cu-TEMPO (2,2,6,6-tetramethyl-l-piperidinoxyl) aerobic oxidation of activated alcohols resulting in good to excellent conversions and 100% selectivity to form the corresponding aldehydes. Considering the experimental results and Density Functional Theory calculations we propose two most plausible reaction mechanisms that further corroborate the enhanced activity of bimetallic species. It appears that the tridentate character of the ligand sacrifices some of the overall catalytic efficiency for the selectivity of the process. Aqueous reaction medium, low catalyst loading, air as oxidant and exclusive oxidative selectivity render these CuII complexes promising candidates for further improvement.

Complexes of antibiotics with metal ions draw attention of scientists looking for new drugs as well as those endeavoring to increase the activity of antibiotics that are currently in use. The bioactivity of antibiotics can be increased by coordination of metal ion. Moreover, such complexes allow for reduction of drug’s dose introduced into the body and improve their bioavailability. In order to study the antimicrobial effect of antibiotics-metal complexes, it is necessary to properly determine their structure and physicochemical properties. Therefore, the selection of appropriate research methods plays a crucial role in a comprehensive understanding and prediction of metallopharmaceuticals’ activity. The electronic structure and spatial structure of antibiotic-metal complexes, their stability, ligands’ donor atoms, acid-base properties, lipophilicity and most preferable binding sites to the biomolecules are essential features of this type of compounds. This review delineates the collection of available tools and methods necessary for an exhaustive analysis of metallopharmaceuticals.

The acidity of Lewis-Bronsted superacids can be derived from the theoretical calculations as the Gibbs free energy of the deprotonation reaction (ΔGacid ), which describes the tendency of a studied compound to donate a proton. This paper presents the first Quantitative Structure - Property Relationship (QSPR) model that correlates the ΔGacid of superacid (HF/MeX3 formula (X=F, Cl, Br)) with their structure. Developed model is well fitted, roubustness, has good predictive abilities, fulfills all OECD recommendation for good model. Obtained results provide the insight into the relation of structural features of superacids, which are responsible for their acid strength - the structures characterized by strong F-Me dative bond (with relatively large vibrational frequency), small positive partial atomic charge on Me central atom, possibly large polarity exhibit large acid strength. Such assumption can be used in the future as valuable information in the process of the designing new, stronger, more effective superacids.

The acidic strength of selected Lewis–Bronsted superacids consisting of HClO4 Bronsted acid and containing the excess of either AlF3 or SbF5 Lewis acid component is evaluated on the basis of theoretical calculations employing ab initio methods. The Gibbs free energies of deprotonation processes for HClO4/n(AlF3) and HClO4/n(SbF5) (n = 1–3) are found to depend on the number (n) of AlF3 or SbF5 molecules (playing Lewis acid role) surrounding the HClO4 system. The successive attachment of either AlF3 or SbF5 molecules to HClO4 gradually increases the acidity strength of the resulting superacid which leads to the saturation achieved for 2–3 AlF3 molecules interacting with Bronsted acid. The preference of formation of the Lewis acid aggregates is observed during the analysis of the most stable HClO4/n(AlF3) and HClO4/n(SbF5) isomeric structures. The mixing ratios of HClO4 and either AlF3 or SbF5 compounds that should likely maximize their resulting acid strength are proposed and discussed.

The mechanism of the (CH3)2CCH2 + H2S → (CH3)3CSH reaction catalyzed by various superacids (HBF4, HAsF6, and HSbF6) was investigated theoretically using the ab initio CCSD(T) and MP2 methods and the aug-cc-pVDZ/LANL2DZ basis sets. The effects of surrounding solvent molecules were approximated by employing the PCM solvation model. The most important findings include the observation that each superacid considered is capable of effectively catalyzing isobutene hydrosulfurization as it reduces the activation barrier by ca. 95% in comparison to the uncatalyzed process.