Aromaticity and Chemical Bonding of Chalcogen-Bonded Capsules Featuring Enhanced Magnetic Anisotropy

We present a theoretical study of chalcogen bonded container capsules ( A_X+A_X ) where X=O, S, Se, and Te, and their encapsulation complexes with n-C₉H₂₀ (n-C₉H₂₀@ A_X+A_X ). Both Se and Te encapsulation complexes have significant experimental and computed binding energies, analogous to the hydrogen bonded counterparts, while the S and O capsules and their encapsulation complexes show only weak binding energies, which are attributed to different types of bonding: chalcogen S⋅⋅⋅N bonds for S-capsules and π–π stacking and weak hydrogen bonds for the O case. All A_X+A_X and C₉H₂₀@ A_X+A_X present unusually high magnetic anisotropies in their interiors. The ¹H NMR spectra of the encapsulation complexes display the proton signals of the encapsulated n-nonane highly upfield shifted, in agreement with the available experimental data for the Se capsule. We found that different factors contribute to the observed magnetic anisotropy of the capsule's interior: for the Te capsule the most important factor is Te's large polarizability; for the O analogue the inductive effects produced by the electronegative nature of the O and N heteroatoms; and for the S and Se capsules, the polarizability of the heteroatoms combines with electric field effects.     

The Development of Highly Sensitive and Selective Immunosensor Based on Antibody Immobilized ZnO Nanorods for the Detection of D‐Dimer

ZnO nanorods were grown on gold coated glass substrate by low temperature aqueous chemical growth method. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques were used for the characterization of ZnO nanorods. ZnO nanorods are highly dense, uniform, well aligned and perpendicular‐oriented to the substrate. ZnO nanorods exhibited good crystal quality. The well aligned ZnO nanorods were potentially used for the development of selective and sensitive immunosensor for the detection of D‐dimer by immobilizing antibody on stabilized lipid films. The ZnO nanorods based immunosensor responded to a wide range of D‐dimer concentrations with fast response time of ca. 20 s.     

Theoretical study of highly excited Σ and Π states of NaLi and experimental observation of the interacting 5Σ and 6Σ states

Theoretical multireference configuration interaction (MRDCI) calculations on the excited ¹Σ⁺ and ¹Π states of NaLi are presented. They improve the results of a previous study by two of the present authors, resolve some differences with other theoretical results and lead to overall good agreement with experimental observations. To extend the experimental data base of electronic states in NaLi, a previously unknown ¹Σ⁺ state is investigated by polarisation labelling spectroscopy. Comparison with accompanying and previous theoretical calculations leads to a conclusion that the observed system consists of two band systems switching smoothly from one adiabatic state to the other and allows assignment of the bands as 5¹Σ⁺ ← X¹Σ⁺ in the lower energy part and to 6¹Σ⁺ ← X¹Σ⁺ for higher energies.     

An ab initio potential energy surface and spectroscopic constants for the XΣg state of NO2

A three-dimensional potential energy function has been calculated for the X¹Σ⁺_g state of NO⁺₂ from ab initio MRD-CI data. With this PE function, converged vibrational calculations have also been performed for ten vibrational states, with the aid of a computer program developed in the present work for this purpose. The calculated harmonic frequencies, vibrational term values and rotational constants are in good agreement with experimental data.     

Calculation of sulphur L(S2p)-MM Auger energies of H2S

The Auger energies of the L(S2p)-MM transitions of H₂S have been computed using MC SCF methods. The results are sufficiently accurate to assign the experimental spectrum and indicate large relaxation as well as large single-triplet splitting for low energy transitions.     

Conformations of the thiathiophthenes and related molecules

A conformational ab initio MO study has been carried out for the thiathiophthene molecule (TTP) and two related model compounds, thiomalonaldehyde (TMA) and its conjugate base (TMA(-)). The conformational energy surfaces for TMA, TMA(-) and TTP were generated using a least squares fit to the calculated data and plotted on a CALCOMP plotter. The results of the calculations showed that the cis-cis planar conformation of TTP is the most stable in agreement with experimental findings. For TMA and TMA(-) the cis-cis planar conformation is not the most stable. Contour plots of the five occupied -MO's of TTP show great similarity to those of naphthalene.Less detailed calculations were carried out for 3-hydroxy-prop-2-en-1-thione (HPT) and 3-mercapto-prop-2-en-1-thione (MPT). HPT was shown to be most stable in the cis planar hydrogen bonded conformation in agreement with the experimentally obtained results. For MPT the non-hydrogen bonded planar structure was found to be the most stable.     

Configuration interaction study of the oscillator strenghts for the A1--- A1 and A1--- A1 transitions of the water molecule

Oscillator strengths for transitions between the ¹A₁ ground state of water and its ¹A₁ and ¹A₁ excited states are computed employing two different theoretical approaches. In one series of calculations a common orthonormal one-electron basis is employed for all of the above states, while in the other type of treatment two different, mutually non-orthogonal, sets are used; the multireference single- and double-excitation (MRD CI) method is employed in each case, with configuration selection, to generate the various electronic wavefunctions. It is found that the use of ground-state SCF MOs leads to poor convergence in the wavefunctions of the (Rydberg-type) ¹A₁ and ¹A₁ excited states and consequently also for the corresponding --- and --- f-values; this behavior is seen to be closely related to the near degeneracy of the two excited states, each of which is a mixture of the 3a₁ → 3sa₁ and 1b₁ → 3pb₁ configurations. Analogous computations with the ¹B₁¹b₁ → 3sa₁ MOs show much better convergence properties, and the resulting f-values compare well with what is obtained when state-specific orbital sets are employed separately for ground and excited states and non-orthonormal techniques are applied to compute the desired transition moments. These results tend to confirm previous findings which indicate conceptual and computational advantages for the calculation of excited-state wavefunctions and properties within the context of a state-specific theory. They also show that although the goal of eliminating the dependence of MRD CI calculations on the choice of MO basis is very nearly approached for energy quantities, it is less satisfactorily achieved for other properties, especially when the existence of nearly degenerate electronic states is a critical factor.     

A Calcium Solid State Ion Selective Minisensor Based on Lipid Films on ZnO Nanorods

This article describes the development of a calcium solid minisensor based on lipid films on ZnO nanorods. The lipid film was composed from dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylcic acid (DPPA). The calibration graph was logarithmically related to the concentration of calcium ions in the range from 10^?6 to 10^?3 M. The response times of the electrode were less than 5 s. No memory effects were observed for this electrode. The reproducibility of the electrode was less than 5 %. The electrode has shown good stability for a period of 1 month. The influence of a wide range of metals and anions as potential interferences was checked. The method was applied to the rapid detection of calcium ions in mineral waters.     

Theoretical study of hydrogen bonding in homodimers and heterodimers of amide, boronic acid, and carboxylic acid, free and in encapsulation complexes

The homodimers and the heterodimers of two amides, two boronic acids, and two carboxylic acids have been calculated in the gas phase and in N,N-dimethylformamide (DMF) and CCl(4) solvents using the DFT (M06-2X and M06-L) and the MP2 methods in conjunction with the 6-31G(d,p) and 6-311+G(d,p) basis sets. Furthermore, their pairwise coencapsulation was studied to examine its effect on the calculated properties of the hydrogen bonds at the ONIOM[M06-2X/6-31G(d,p);PM6], ONIOM[MP2/6-31G(d,p); PM6], and M06-2X/6-31G(d,p) levels of theory. The present work is directed toward the theoretical rationalization and interpretation of recent experimental results on hydrogen bonding in encaptulation complexes [D. Ajami et al. J. Am. Chem. Soc. 2011, 133, 9689-9691]. The calculated dimerization energy (ΔE) values range from 0.74 to 0.35 eV for the different dimers in the gas phase, with the ordering carboxylic homodimers > amide-carboxylic dimers > amide homodimers > boronic-carboxylic dimers > amide-boronic dimers > boronic homodimers. In solvents, generally smaller ΔE values are calculated with only small variations in the ordering. In the capsule, the ΔE values range between 0.67 and 0.33 eV with practically the same ordering as in the gas phase. The calculated % distributions of the encapsulated dimers, taking into account statistical factors, are in agreement with the experimental distribution, where the occurrence of boronic homodimer dominates, even though it is calculated to have the smallest ΔE.     

Conformations and fluorescence of encapsulated stilbene

Absorption and emission spectra of free and encapsulated stilbene in two different capsules were calculated using the DFT and the TDDFT methodology at the B3LYP, CAM-B3LYP, M06-2X, PBE0, and ωB97X-D/6-31G(d,p) levels of theory. The present work is directed toward the theoretical interpretation of recent experimental results on control of stilbene conformation and fluorescence in capsules [Ams, M. R.; et al. Beilstein J. Org. Chem. 2009, 5, 79]. The results of the calculations are in agreement with experiment and show that fluorescence of trans-stilbene persists in the large cage while it is quenched in the small one. It is found that the geometry of trans-stilbene in the ground as well as in the first excited singlet state is unaffected by encapsulation in the large cage, and consequently the absorption and emission spectra are similarly unaffected. In the small cage, the ground state of encapsulated trans-stilbene is distorted, with the two phenyl groups twisted, while the geometry of the excited state, after relaxation, lies at the conical intersection with the ground state. Consequently, there is no emission similar to that of free trans-stilbene, and the state decays nonradiatively to the ground state.