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A novel pyrene‐sulfathiazole‐based potential drug candidate 3 was designed, successfully synthesized by a condensation reaction of pyrenecarboxaldehyde (1) with sulfathiazole (2) in good yield, and fully characterized by NMR, IR, UV‐Vis, and HRMS spectroscopic techniques. The TD‐DFT/B3LYP calculations displayed that the recorded peaks at 396, 377, 280, and 236 nm were due to the mainly n‐π* and partially π‐π* transitions that occurred on pyrene, azomethine, and sulfathiazole moieties. The NBO results disclosed that the electron delocalizations happened onto sulfathiazole, aromatic rings (pyrene and Ph‐), and azomethine groups had the main responsibility of the lowering stabilization energy of compound 3. The NMR shifts were calculated by using the GIAO approaches in the DMSO phase and compared with the relevant data recorded. The thermodynamic and quantum chemical quantities were used for elucidating the physicochemical properties and reactivity behavior, in THF, DMSO, and water simulation environments. Accordingly, the calculated DM (D) and α (au) order of compound 3 were calculated in the order of vacuum

In this study, (E)-N-phenyl-1(pyren-1yl)methanimine (3) and a isomeric mixture of 5ZZ and 5EE (1,4-phenylenebis(1-(pyren-1-yl)methanimine) were synthesized by condensation of pyrene-1-carbaldehyde (1) with aniline (2) or benzene-1,4-diamine (4) The synthesized compounds were characterized using NMR, UV–vis, IR and HRMS spectroscopic techniques. Utilizing the density functional theory (DFT) and a basis set of B3LYP/6-311G(2d,2p), theoretical computations were done. The computed values were applied to simulated spectra of compounds 3 and the isomeric mixtures 5EE , and 5ZZ demonstrating good agreement with observed spectra. In various solvents, the UV–vis spectra of compounds 3 , 5EE , and 5ZZ were recorded in areas 200–500 nm, and function density theory (DFT) and time-dependent density functional theory (TD-DFT) algorithms were used to determine if they can serve as metal-free organic dyes in the use of dye-sensitized solar cells (DSSCs). The charge separation distance (Δr) between an electron and the hole it corresponds to was investigated in addition to the degree of electron-hole overlap (Λ) because transition density matrices (TDM) give information about how each electron departs from its corresponding hole during excitations, resulting in charge transfer (CT). To obtain more insight into the characteristics of complexes, the Mulliken population approach, density of states (TDOS), natural population analysis (NPA), molecular electrostatic potential (MEP), condensed Fukui function, and relative nucleophilicity indices derived from orbital charge calculation results (NPA) were used. In addition, the photovoltaic properties of these compounds were studied comparatively. DFT band gap for 3 was 2.493, 5EE was 2.050, and 5ZZ was 2.071 eV. Furthermore, the power conversion efficiency (PCE) values for compound 3 and the isomeric mixture of compound 5 are calculated as 2.31%, and 2.82%, respectively. The results obtained can provide a useful reference for the development of organic compounds containing pyrene units in more efficient organic-based compounds for photovoltaic applications. This study serves as a valuable guide to studying synthesized compounds studied as a metal-free organic dye in dye-sensitized solar cells, from which the actual efficiencies can be obtained when analyzing the DSSC properties by performing experimental and TD-DFT calculations. [Display omitted] • Pyrene-imine-based organic materials 3 , and 5 (isomeric mixtures, 5 EE and 5ZZ) derived from the pyrenecarbaldehyde (1) with aniline (2) and benzene-1,4-diamine (4) and have been designed, synthesized, and characterized. • The compound 3 was designed to incorporate D-A-D ′ structural motif while the isomeric mixtures 5 EE and 5ZZ were designed to incorporating D-A-π-A-D structural motifs. • The organic materials was synthesized in excellent yield using a one pot/one step condensation reaction, and characterized by various spectroscopic techniques. • The photovoltaic properties of all the materials were investigated and, DFT calculations have supported the obtained experimental results. • The results here reported that pyrene-imine-based hybrid skeletons, especially 5 EE and 5ZZ , show great promise as photosensitive organic materials for DSSCs. [ABSTRACT FROM AUTHOR]

• Three organic materials 2, 4a-b incorporating branched tetraethoxymethyl, diphenyl, and dipyrenyl units, respectively linked to benzidine core through two imine π-bridge were designed. • The organic materials have been synthesized and characterized by spectroscopic techniques. • The molecular geometry, vibrational frequencies, and 1H/13C NMR chemical shift values of the organic materials are investigated utilizing B3LYP/6–311G(2d,2p). • Among these materials, the novel compound 4b with the d -A-π-A-D architecture is a potential candidate as useful electron transport materials for DSSCs. Herein, tetraethoxymethyl, diphenyl, and dipyrenyl units have been fused with biphenyl group, via diimine bond, resulting in 3 (2 novel) benzidine derivatives 2, 4a-b. The derivatives were successfully synthesized by condensation of three different aldehydes (formaldehyde, benzaldehyde 3a, and pyrenecarboxaldehyde 3b) with benzidine in high yields. Structural identifications of the newly obtained compounds are determined by NMR, IR, UV–Vis, and HRMS spectroscopic techniques. Then, the photovoltaic properties of the organic compounds were investigated. To obtain insight into the geometric, electronic, and spectroscopic features of compounds 2, 4a-b , theoretical calculations were performed utilizing the B3LYP/6–311G(2d,2p) basis set. Theoretical 1H and 13C NMR resonance signals of compounds 2, 4a-b were estimated in the gas phase and the IEFPCM model in solvent field calculations utilizing the GIAO method at the B3LYP/6–311G(2d,2p) level and showed excellent correlation with the experimental results. A comparison of computed and experimental vibrational frequencies was performed, and significant bands were allocated. The results showed that experimental and theoretical IR frequencies had a good correlation (R2=0.9997 (2), 0.9996 (4a), and 0.9940 (4b)). To explain the relationship between the molecular structure of the compounds and photovoltaic properties, density functional theory (DFT) and its time-dependent form (TD-DFT) were utilized. The HOMO-LUMO energies and energy gap (Eg) helped understand optimal energy levels for electron absorption and transfer. The calculated band-gap of compounds 2, 4a-b were 4.705, 3.679, and 3.006 eV, respectively. The power conversion efficiency (PCE) values for the compounds 2, 4a-b were also calculated as 2.25, 2.70, and 2.80%, respectively. Compared to compounds 2 and 4a , dipyrenyl-bearing benzidine derivative 4b showed a larger redshift in the absorption wavelength with a remarkable high PCE value along with a low Eg value, which can be attributed to the greater stability of 4b due to the extended π-conjugation. Therefore, compound 4b with the d -A-π-A-D architecture is a potential candidate as useful electron transport material for DSSCs. [Display omitted] [ABSTRACT FROM AUTHOR]