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The synthesis of and spectroscopic data on subazaporphyrins, subphthalocyanines, subnaphthalocyanines and their related compounds reported to date are summarized, together with the results of molecular orbital (MO) calculations from our laboratory. Thus the problems and key points in the synthesis of these subazamacrocycles and their electronic absorption and magnetic circular dichroism (MCD) spectra are discussed, together with those of the monosubstituted-type low-symmetrical phthalocyanines obtained by their ring expansion reaction. The Q bands of these subazamacrocycles are orbitally doubly degenerate, and in the Soret band region, three transitions to the orbitally degenerate state are found. The MO calculations suggest that the HOMO levels destabilize considerably while the LUMO levels change slightly with increasing size of the π system. In addition, the electronic adsorption data are reproduced by the calculation only when the two pyrrole hydrogens in the monosubstituted-type phthalocyanines are assumed to be linked to the two pyrrole nitrogens along the short axis.

Molecular orbital (MO) calculations of more than 60 porphyrinic π conjugated structures have been performed within the framework of the Pariser–Parr–Pople approximation. The results of a series of compounds are introduced and summarized in order to show how they vary depending on the systematic change in molecular structure. These are shown schematically or itemized. Our results are compared with the spectra of the corresponding known compounds and with the MO results reported by previous workers, if available. In addition, the results have continually been compared, where possible, with those of tetraazaporphyrin or phthalocyanine systems. In naphthalene- or anthracene-fused compounds, these molecule-centered orbitals often appear, and these are indicated using either triangles or circles in figures if they appear between HOMO – 3 and LUMO + 3 orbitals.

In this work we employ an algebraic computational method to solve the integrals which arise in the study of diatomic molecules. Using the Slater-type orbitals (STO), we obtain analytical solutions for the one-center and two-center hybrid and Coulomb integrals. The exchange integrals are considered, as much as possible, in a similar manner. These results are used to calculate the electronic properties of the ground state of the LiH molecule, by means of a variational calculation using a basis of molecular orbitals. The behavior of the Slater exponents of the atomic orbitals are studied as functions of internuclear distance. We show that the STO undergo a lengthening of their shape when the nuclear separation increases.

Corresponding relation between the electron distributions and the harmonic minimum is established, by taking for example of the harmonic generation of the aligned CO₂ molecules in the highest-occupied-molecular-orbital (HOMO). We show that, as the polarization of the driving laser field rotates from parallel to perpendicular to the molecular axis, the harmonic yield first increases then decreases, and the location of the minimum in the harmonic spectrum moves to the higher energy region. These variations are connected with the electron distributions in the molecular orbital (MO) along the laser polarization of the driving laser field. Hence, by varying the laser polarization to scan, one can extract the overall electron distributions of the MOs from the generated harmonics.

The gas response of metal oxide-based sensors depends strongly on its adsorption properties. To explore the potential sensing capability of pristine and nitrogen modified TiO₂/graphene oxide (GO) heterostructures, the adsorption of NO₂ molecule on the N-doped nanocomposites was investigated using density functional theory (DFT) calculations. Six possible configurations were simulated based on the estimated adsorption energies. The binding sites were located over the oxygen, doped nitrogen and five-fold coordinated titanium atoms of TiO₂. The electronic properties including atomic Mulliken population, projected density of states and molecular orbitals were investigated in detail. The N–O bonds of the NO₂ molecule were significantly increased after the adsorption process. The adsorption of NO₂ molecule on the N-doped nanocomposite is more energetically favorable than the adsorption on the undoped one. The results suggest that NO₂ chemisorbs on the considered nanocomposites. Mulliken population analysis reveals a noticeable charge transfer from the nanocomposite to the molecule, which indicate that NO₂ acts as a charge acceptor. Molecular orbital calculations show that the highest occupied molecular orbitals (HOMOs) of the studied systems were mainly localized on the adsorbed NO₂ molecule. The significant overlaps in the projected density of states (PDOS) spectra of the interacting atoms confirm the formation of chemical bonds between them. There is a direct relationship between the results of charge transfer and sensing responses. N-doped nanocomposites have better sensing response than the undoped ones. The results highlight the possibility to develop innovative highly efficient NO₂ sensors based on novel TiO₂/GO nanocomposites.

The indium(III) complexes of (4-(tert-butyl)phenyl)-substituted tetraazaisobacteriochlorin (TAiBC) and tetraazachlorin (TAC) were synthesized by direct template condensation of bis(4-(tert-butyl)phenyl)fumaronitrile and tetramethylsuccinonitrile using indium(III) ion as a matrix. The corresponding metal-free tetraazaisobacteriochlorin and tetraazachlorin were obtained by demetallation of their indium(III) complexes. These metal-free complexes were characterized using elemental analysis, mass-spectrometry, ¹H and ${}^{13}$C{¹H}NMR spectroscopy, UV-vis and MCD spectroscopy as well as DFT and TD-DFT calculations. Due to the low symmetry of the molecules, the NMR data were complex, but could be assigned by collecting 1D- and 2D NMR data and comparing with the results of quantum chemical calculations. From the position of the pyrrole proton signal (6.78 ppm), it was found that the diatropic current of TAiBC is much weaker than that of TAC, and plausibly the weakest among porphyrinoids so far reported. Absorption and MCD spectra were reasonably interpreted using the calculated absorption spectra.