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• Selective colorimetric recognition of cyanide ion in both solution and solid states. • Fast response to CN– (< 5 s). • Water percentage has a key role in the cyanide's recognition mechanism. • Recognition mechanism was investigated by IR soectroscopy. A novel chemosensor based on Nifuroxazide Cr(III) complex was developed for recognizing CN– over other tested anions e.g., F–, Cl–, Br–, I–, CH 3 COO–, NO 2 –, PO 4 3–, and SCN– in DMSO–H 2 O (9:1, v/v) and THF. Without any interference from the tested anions, UV–vis spectroscopy was used to investigate the recognition of CN–. The deprotonated species that resulted from the ionization of the phenolic group may be the cause of the color shift that occurred after adding CN– to the solution of the Cr(III) complex. The charge transfer interaction between the electron-donor unit and the electron-deficient nitro-furan moiety was improved as a result of the ionization of the phenolic group. The fact that the developed color vanishes in protic polar solvents e.g., H 2 O, CH 3 OH, and C 2 H 5 OH may lend credence to this assumption. The Lambert–Beer's law was obeyed in the concentration ranges of 3.4 × 10−3–3.4 × 10−5 M and 1.0 × 10−4–5.0 × 10−6 M in DMSO–H 2 O (9:1, v/v) and THF, respectively, reflecting the significant role of the solvent in controlling the sensitivity of the developed probe. The electronic transitions were investigated by executing time-dependent density functional theory calculations. [Display omitted] [ABSTRACT FROM AUTHOR]

• Square-pyramidal Zn(II) azide complexes. • Based on TDDFT calculations, the lowest E transition is assigned to LLCT (N 3 →Terpy). • NBO analysis supported charge transfer from coordination sites toward Zn(II). • MEP maps showed that azido ligands have roles in the cycloaddition reaction. Square-pyramidal Zn(II) azide complexes with the formula of [Zn n (N 3) 2n L] (n = 1; L = 4′-(2-pyridyl)-2,2′:6′,2′'-terpyridine (LPy), 4′-(4-phenylmorpholine)-2,2′:6′,2′'-terpyridine (LMorph), and n = 2; L = 1,4- bis (2,2′:6′,2′'-terpyridin-4′-yl)benzene (LBPY)) were synthesized, and structurally characterized using different spectroscopic and analytical tools. Ground-state geometry optimization and harmonic vibrational analysis were carried out at two different levels of theory (B3LYP/LANL2DZ and CAM-B3LYP/def2-SVP) to gather insights into the local minimum structures. Natural bond orbital (NBO) analyses revealed that the electronic population of the 3d orbitals of Zn(II) ion is corresponding to the oxidation state of Zn(I), not Zn(II), in agreement with the ligand to metal charge transfer. Molecular electrostatic potential energy maps showed that the azido ligand may act as a nucleophile in the cycloaddition coupling with electron poor dipolar molecules. The electronic structure and transitions were investigated by executing time dependent density functional theory (TDDFT) calculations. [Display omitted] [ABSTRACT FROM AUTHOR]