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Quantum chemical calculations at semiempirical (MNDO methods) and ab initio (6-31G and STO-3G basis ses) levels have been performed on boron(III) subphthalocyanines 1-10. Theoretical calculations predict a cone-shaped structure for these compounds independently of the kind of peripheral substitution and even of compositional changes in the central region of the macrocycle (for example, substitution of the boron atom by two hydrogens). The theoretical calculations are in excellent agreement with previous X-ray determinations.

Theoretical calculations were performed for studying the electronic molecular structure of axial subphthalocyanine (SubPc) derivatives. The intermolecular SubPc interactions were also investigated at theoretical level using adequate models. These models represent the interaction of one Cl(OR)-SubPc with the surrounding molecules through the Cl atom as well as the interaction of the Cl-SubPc with an incoming diiminoisoindole group in the first steps of the open ring reaction. The SubPc complexes with more electronegative atoms than Cl heteroatoms in apical positions are more pyramidal than Cl-SubPc. The B–X and B–Np are the most sensitive macrocycle positions with respect to the axial substitutions in SubPcs. The B–X bond has an elevated polarity and seems to correlate with the chemical reactivity of these compounds. The theoretical calculations of the near-frontier orbitals reveal an outstanding energetic and structural homogeneity along the studied series which is in correspondence with the fact that the axial ligand has only a small influence on the position of the maximum bands in UV-vis spectra as well as in the first half-wave potentials for oxidative processes. The study of the intermolecular interactions give information about their influence on the molecular structure of the axial complexes of the SubPcs. The characterization of the interaction of one Cl-SubPc with a pyrrol containing group may be useful in the understanding of the mechanism of the ring expansion reactions. In general, the present results indicate that the apical position may be a critical reactive center both for redox and axial substitution processes.

The micro-perforated panel structure has good sound absorption performance in medium and high frequencies, and the labyrinth metamaterial structure has good low-frequency sound absorption performance. Both the two structures are relatively simple, and can be obtained by simple processing with resin material, which is convenient for batch production. In order to enhance sound absorption ability for the sound absorption structure within low frequency, this research work has put forward one coupled structure via the micro-perforated panel and three second-order maze metamaterials structure, resulting in a coupled structure with a low-frequency sound absorption performance. Combination of equivalent circuit method calculates acoustic resistance and absorption coefficient for the sound absorption structure, and genetic algorithm has been employed to optimize the parameters of this sound absorption structure. Finally, the theoretical calculations analysis results have been verified by finite element simulation, which shows the trend of the curve of sound absorption coefficient of the two structures was basically consistent. And the sound absorption coefficient of the three peaks is all above 0.7, and the mean value of the sound absorption coefficient is above 0.6 at the acoustic frequency of 0–1500Hz, indicating that the coupled structure has a good performance of absorbing medium- and low-frequency sound waves.

¹⁵N and ¹³C NMR chemical shifts for four radiosensitizers have been calculated and compared with experimental data. The thermal and solvent effects on NMR spectra were simulated with the polarizable continuum model and an alternative molecular dynamics/quantum mechanics methodology. Magnetic shielding tensors were evaluated at the GIAO-B3LYP and GIAO-OPBE level using II' and 6-311+(2D,P) basis sets, showing that it is essential to incorporate the dynamics and solvent effects on NMR calculations in condensed phases.

The molecular structure and intra-molecular hydrogen bond energy of 20 conformers of 3-hydroxy-propenethial were investigated by using the MP2 and B3LYP levels of theory coupled to the 6-311++G** basis set. Also, computations for all the possible conformations of HPT in water and carbon tetrachloride solution were performed. The calculated geometrical parameters and conformational analyses in both gas phase and solution reveal that the closed ring hydrogen bonded structures are more stable than the remainder of the species. Hydrogen bond energies for various hydrogen-bonded conformers were obtained and investigated by means of the Bader theory of atoms in molecules (which is based on topological properties of the electron density).

The solvent effects on the keto-enol tautomeric equilibriums of ethyl acetoacetate (EAA) and tetronic acid (TA) are theoretically investigated. The present study shows that the most stable keto tautomer of EAA corresponds to the trans diketo, E, Z form; while the most stable enol tautomer corresponds to the structure in which the enolization takes place at the carbonyl group. Our calculations also put in evidence that the keto tautomer of TA prefers the trans diketo, E, E form, while the most stable enol tautomer corresponds to the structure in which the enolization takes place at the carbonyl group. The calculated free energies indicate that, in polar solvents, the keto-enol equilibrium of EAA is shifted towards the keto tautomer, whereas the keto-enol equilibrium of TA is shifted toward the enol tautomer. The trends of the change of equilibrium constants with respect to the change of solvent polarity are well reproduced by both B3LYP and MP2 calculations. The present study shows that the enthalpic term is predominant in the determination of the calculated equilibrium constants and the entropic effect on the calculated Gibbs free energies is found to be very small and has little influence on the studied keto-enol tautomeric equilibriums.

The low-lying candidates of hydrated divalent lead ion clusters [Pb(H₂O)_n]²⁺ with up to n = 17 have been extensively studied by using density functional theory (DFT) at B3LYP level. The optimized structures show that for n = 5–13 the lowest-energy structures prefer tetracoordinate with hemi-directed geometries, while the best candidates with n = 14–17 are hexacoordinate with holo-directed geometries, which is just consistent with the experimental observation. Furthermore, the origin of hemi-directed and holo-directed geometries has been revealed. It is found that in the hemi-directed geometries, the lone pair orbital has p character and fewer electrons are transferred from the water molecules to the Pb²⁺ ion. Contrarily, in the holo-directed geometries, the lone pair orbital has little or no p character and more electrons are transferred to the Pb²⁺ ion. On the other hand, the proton transfer reactions of the [Pb(H₂O)_n]²⁺(n = 2, 4, 8) complexes have been examined, from which the predicted products of these complexes are in good agreement with the experimental observation.

Theoretical calculations 6-311++G(d,p) have been performed in order to obtain binding energies and molecular properties of complexes involving nitrous oxide (N₂O) and two HX (X = F, Cl, Br and CN) molecules. Our calculations have revealed the existence of eleven stable structures. The vibrational changes which take place in the HX acid after complexation follow the usual behavior: the HX stretching frequency is shifted downward whereas its IR intensity is much enhanced. The new vibrational modes arising upon H-bond formation, were verified, especially, those associated with the out-of-plane and in-plane HX bending modes, which are pure rotations in the HX isolated molecule.

A theoretical analysis of the structure, aromaticity, magnetic properties and bonding in TBSPBOH and SPBOH complexes was performed. Geometry optimizations were carried out in the gas-phase at the B3LYP/6-31G(d) theory level. ¹H and ¹³C NMR spectra of these complexes were evaluated at the B3LYP/6-311+G(2d,p)-PCM theory level in CHCl₃ solution. The vector field induced by an external magnetic field was computed at the CHF/6-31G(d) theory level using the CTOCD-DZ formulation. In these cone-shaped molecules, the 14-π electron current induced in them by an external magnetic field does not follow a [14]-annulene path but the inner edge of the macrocycle. Therefore, the 14-π electron aromatic core corresponding to this induced current is constituted by the three mesoC atoms, the three N atoms, and the six C atoms directly bonded to them. The involvement of the N atoms in the 14-π aromatic core implies that one of the B-N bonds is a weaker B←N dative bond whose presence is reflected in the geometry of these complexes, which display larger average B-N bond lengths than in tripyrrolylborane. Thus, according to our analysis, structure, aromaticity and bonding in these systems are closely related. The anisotropic effect is somewhat larger in SPBOH than in TBSPBOH, and the larger curvature of the former makes larger relative shielding constants possible, not only for the hydroxyl proton but also for the outer atoms.

A hexapyrrane P6 with a terminal N-confused pyrrole was synthesized by acid-catalyzed [3+3] condensation followed by oxidation with DDQ, which did not afford the expected N-confused hexaphyrin. In stead, a rearranged product, i.e., $\alpha$-dipyrrin appended N-confused porphyrin 1 was obtained in a yield of 46%. Chelation of 1 with Pt(II) afforded the peripheral complex 1-Pt, which was further coordinated with Rh(I) in the cavity to afford the corresponding bimetallic complex 1-Pt-Rh. Both 1-Pt and 1-Pt-Rh exhibit split Soret-like bands and noticeable Q-like bands tailing to the NIR region up to ca. 1200 nm. Single crystal X-ray diffraction analyses of 1 and 1-Pt revealed that the peripheral coordination of Pt(II) slightly modifies the interplanar angle between the porphyrin macrocycle and the dipyrrin unit, which may modulate the absorption spectra. The results of this work compose an interesting example of synthesizing porphyrinoids appended with conjugated peripheral chains by the oxidative ring closure reaction of an oligopyrrane containing a terminal N-confused pyrrole, and such compounds may be used for both inner and peripheral coordination to afford complexes with tunable NIR absorption.