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The anions of C60 fullerene have geometrically multiple distortions. These geometric changes of C60 were directly related to the orbital changes called structural distortion effects. In this study, neutral C60 fullerene and its −1 to −6 anions were optimized by using DFT method. The geometric changes and the electronic properties were also investigated. Unrestricted calculations were applied to investigate the energy gap changes and density of states (DOS) spectrums as well. The electron localization function (ELF) along with the natural bond orbital (NBO) calculations were presented the considerable images from the changes of electron properties of C60 fullerene. The results show that in −5 and −6 anions lost π bonds and also can see creation of non-bonding lone pair in −6 anion. The calculations on the vibrational levels, structural changes such as changes in diameters and dipole moments of C60n (n = 0 to −6) were investigated as well. The most stable spin forms of the optimized C60 structures were chosen to observe structural distortions by using the DFT computational method. For some of the anions the wide changes of forms, energies of the valance orbitals and the energy states were investigated for the low and high spins. Also, the spin channel phenomenon was studied by using the results of DFT-B3LYP/6-31G∗ calculations. The NBO analysis was performed due to its beneficial information in the changes of fullerene electronic system properties for all the anion states in the selected computational level method. The changes of the calculated IR spectra patterns have discussed due to the charge changes of C60n (n = 0 to −6) and on the basis of the structural distortions role (John-Teller effect). A linear equation was obtained by using graph theory (GT) between the energy of HOMO and/or LUMO orbitals and load amount of anions. The DOS spectrums and HOMO and LUMO orbitals in the different discussed spin states show that all fullerene anions have different spin behavior and magnetic specifications, in which anions −2 and −3 anions of C60 act as the spin channels.

The electronic and optical properties of N,N′-bis(salicylidene)-1,2-phenylenediamine (SPDA) ligand were studied as a chemical sensor of Mg2+ cation in two solvents (water and DMSO) using the ab initio theory through Density Functional Theory (DFT) and Time Dependent Density Functional theory (TDDFT) methods. The results show that the SPDA ligand has a high ability for chemical sensing of Mg2+. The results has also represented that HOMO-LUMO energy gap decreases 0.941 eV after the complex formation between SPDA and Mg2+. In addition, obvious changes are found in the UV–Vis absorption spectrum, optical analyses SPDA ligand and [SPDA.Mg]2+ complex, which it has the capability of detecting Mg2+ via the adsorptive UV–Vis and colorimetric methods. Emission spectrum calculations and photoinduced electron transfer (PET) process in water solution shows different wavelength emission spectrum in amount of 4.6 nm. An analysis of NBO (natural bond orbital) data indicates tangible changes in the electron transfers data from the electron pairs of ligand to the conjugated system, both prior and subsequent to Mg2+addition.

Today, due to convenience, rapid diagnosis and etc., chemosensors are widely used to detect metal ions. In the current research, through DFT and TD-DFT methods, 8-hydroxyquinoline-5-carbaldehyde-(benzotriazol-1′-acetyl) (QCH) ligand was used to identify Mg2+ cation and investigate its fluorescence emission spectrum mechanism. In order to investigate electronic properties, natural bond orbital (NBO) analysis, reduced density gradient (RDG) plots and electron localization function (ELF) as well as, changes in energy gap of HOMO and LUMO orbitals in the ground state, in water solution were used. Energy gap underwent change about ΔE = 0.17 eV in the presence of Mg2+ cation. Using TD-DFT calculations the optical absorption and emission of QCH ligand was investigated in the presence and absence of Mg2+cation. QCH ligand lacks emission spectrum but in the presence of Mg2+cation shows an emission spectrum in the wavelength of λEmi = 611 nm. Using electron-hole theory, photoinduced electron transfer (PET) process and fluorescence emission spectrum mechanism were investigated. Turning on emission spectrum in the presence of Mg2+ cation is due to stopping charge transfer from chelator to fluorophore.

Magnesium is one of the most common metal cations that contributes to the metabolism cycle of living beings as a biological ion so sensing magnesium ions is of great importance. As a catalyst, magnesium plays an essential part in a large number of cellular processes such as enzymatic biochemical reactions, and cell proliferation. Recently chemosensors are widely used in the detection of metal cations. In this study, the sensing ability of Isatin-3-(7′-Methoxychromone-3′-methylidene) (HL) ligands for the bivalent Mg +2 and Ca +2 cations was studied and compared using density function theory (DFT) method. The main inconvenient factor to detect magnesium is the Ca +2 cation. The calculations were performed using the CAM-B3LYP method on an aqueous environment. The analysis of optical data, including fluorescent and electronic absorption and emission indicates more sensitivity and selectivity for the detection of Mg +2 compared to Ca +2 in a way that energy gap changes of the [HL + Mg] and [HL + Ca] complexes are 0.155 eV and 0.054 eV respectively.