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By removing one carbon atom from [60]­Fullerene (C60), two different isomers (C59 [9-4] and C59 [8-5]) are generated for the C59 cluster. Inspired by their structural and electronic properties, we, theoretically, studied the static and frequency-dependent electronic (hyper)­polarizabilities of sp- and sp2-hybridized isomers in vacuum by TD-DFT calculations. The simulated absorption spectra showed that all absorption bands of C59 [9-4] and C59 [8-5] are attributed to π → π* and n → π* transitions. Regarding their nonlinear optical properties, it is found that the frequency-dependent polarizability anisotropy αanisotropy(λ = 1064.80 nm) of C59 [8-5] is 4 times larger than the static regime, revealing a notable polarization anisotropy, due to the delocalized π electrons around the vacancy defect. By decreasing the incident wavelengths from λ = 1908 nm to λ =589.08 nm, the dispersion of optical nonlinearity of C59 [8-5] has achieved the maximum at β xxx (λ = 1064.8 nm) = 38.150 au and (γ xxxx (λ = 589.08 nm) = −9.896 × 107 au), indicating that the resonance effect of the hyperpolarizability amplified with the decrease of incident wavelengths. Hyperpolarizability density analyses in X and Z directions displayed that the conspicuous negative ρ xxx (3)(r⃗) and −zρ zzz (3)(r⃗) are more expanded on the C59 [8-5] cage when the main contributions stem from the π electrons instead to the sp-hybridized carbon.

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Tryptophan methyl ester (Trp-ME) degrades with singlet oxygen and produce compounds which are photosensitizers and may react to form other derivatives such as N’-Formylkynurénine (NFK) and kynurenine, which are the final products of this oxidation. In order to study and optimize the molecular structure of NFK and determine its different thermodynamic properties, we performed a conformational analysis by DFT/B3LYP method with 3-21G basis set. Six most stable conformations were observed through the analysis of the potential energy surfaces, obtained by a relaxed scan of the dihedral angles. The most stable form of NFK has been registered for D[Formula: see text], D[Formula: see text], D[Formula: see text], D[Formula: see text], D[Formula: see text], and D[Formula: see text]. The study was conducted by HF and DFT/B3LYP with 6-31G(d,p), 6-3[Formula: see text](d,p) and 6-31[Formula: see text](d,p) basis sets, on the optimized geometry of the most stable conformation and its thermodynamic and orbital properties. Two absorption bands were recorded at [Formula: see text][Formula: see text]nm and at [Formula: see text][Formula: see text]nm and were also determined by TD-DFT method. They showed good agreement with the UV experimental spectrum which confirms that it is a powerful tool to determine the dynamic and static properties of molecules. The surface of the electrostatic potential (ESP) of the NFK was also analyzed.

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