Crystal structure characterization, Hirshfeld surface analysis, and DFT calculation studies of 1-(6-amino-5-nitronaphthalen-2-yl)ethanone

The title compound, C12H10N2O3, was obtained by the deacetylation reaction of 1-(6-amino-5-nitronaphthalen-2-yl)ethanone in a concentrated sulfuric acid methanol solution. The molecule comprises a naphthalene ring system bearing an acetyl, amino and nitro groups. In the crystal, the molecules are assembled into a two-dimensional network by N⋯H/H⋯N and O⋯H/H⋯O hydrogen-bonding interactions. n–π and π–π stacking interactions are the dominant interactions in the three-dimensional crystal packing.

The title compound, C 12 H 10 N 2 O 3 , was obtained by the deacetylation reaction of 1-(6-amino-5-nitronaphthalen-2-yl)ethanone in a concentrated sulfuric acid methanol solution.The molecule comprises a naphthalene ring system bearing an acetyl group (C-3), an amino group (C-7), and a nitro group (C-8).In the crystal, the molecules are assembled into a two-dimensional network by N� � �H/ H� � �N and O� � �H/H� � �O hydrogen-bonding interactions.n-� and �-� stacking interactions are the dominant interactions in the three-dimensional crystal packing.Hirshfeld surface analysis indicates that the most important contributions are from O� � �H/H� � �O (34.9%),H� � �H (33.7%), and C� � �H/H� � �C (11.0%) contacts.The energies of the frontier molecular orbitals were computed using density functional theory (DFT) calculations at the B3LYP-D3BJ/def2-TZVP level of theory and the LUMO-HOMO energy gap of the molecule is 3.765 eV.

Chemical context
2-Naphthylamine (also known as �-naphthylamine, CAS 91-59-8) occurs as pink crystals under the influence of light and has a weak, aromatic odor.In the past, It has been used for ligands or surfactants for the production of azo dyes, as an antioxidant in the rubber industry, as well as in the cable industry (Czubacka et al., 2020).It is also used for oxytocinase assays, water analysis, and sewage control, and as a model bladder carcinogen in laboratories (Freudenthal et al., 1999).It is not currently produced on an industrial scale and is not found in the natural state.
2-Naphthylamine derivatives find applications in organic synthesis and serve as building blocks in the synthesis of dyes (Czubacka et al., 2020), pharmaceuticals (Wu et al., 2024), and other organic compounds (Ding et al., 2005;Yao et al., 2013).The title 2-naphthylamine derivative, (I) was obtained by the deacetylation reaction of 2-acetyl-6-acetylamino-5-nitro-naphthalene in concentrated sulfuric acid methanol solution.Herein we report the crystal structure, Hirshfeld surface analysis, and density functional theory (DFT) calculations of the molecule.

Structural commentary
The title compound (Fig. 1) comprises a naphthalene core structure, where all carbon atoms within the naphthalene ring system (C1-C10) are ideally sp 2 -hybridized.The amino group and the nitro group are adjacent, located at positions C-7 and C-8, respectively, of the naphthalene ring system,while the acetyl group is located at the C-3 position.The angles between the two hydrogen atoms on the amino group and between the two oxygen atoms on the nitro group are 120 and 118.66 (17) � , respectively.The O2-N1-C8-C9 and O2-N1-C8-C7 torsion angles are 112.80(3) and À 165.8 (2) � , respectively.The acetyl group and naphthalene ring system are almost coplanar, the O1-C11-C3-C2 and C12-C11-C3-C4 torsion angles being 2.00 (3) and 2.80 (3) � , respectively.The intramolecular N2-H2A� � �O and C1-H1� � �O2 hydrogen bonds (Table 1) lead to the formation of two six-membered rings, stabilizing the molecular conformation (Fig. 1).The structure of I is further stabilized by atom-centroid and centroid-centroid (Cg-Cg) interactions, illustrated in Fig. 2.

Database survey
A survey of the Cambridge Structural Database (CSD version 2024.1.0;Groom et al., 2016) revealed a total of nine compounds with structural similarity greater than 70%, of which six have an acetyl or nitro substituent connected to the naphthalene ring core structure.However, there is only one compound with both acetyl and amino groups on the naphthalene ring system (refcode EBUXIL, CCDC 955350; Rejc et al., 2014).The title molecule atomic numbering scheme.Displacement ellipsoids are depicted at the 50% probability level The C1-H1� � �O2 and N2-H2A� � �O3 intramolecular hydrogen bonds are depicted by gray dashed lines.

Figure 2
The packing of the molecules showing the n-� and �-� stacking interactions (dashed lines) along the a-axis direction.

Figure 3
The packing of molecules showing the hydrogen-bonding interactions (gray dashed lines) along (a) the a-axis direction and (b) the b-axis direction.

Hirshfeld Surface analysis
In order to visualize the intermolecular interactions, a Hirshfeld surface analysis (Hirshfeld, 1977) was carried out using Crystal Explorer 21.5 (Spackman et al., 2021).The threedimensional d norm surface of the title compound, plotted with a standardized resolution and color scale ranging from À 0.4536 (red) to 1.4893 (blue) a.u. is shown in Fig. 4. It reveals the primary interactions to be internal and external hydrogen bonds, n-� and �-� interactions.The intense red spots symbolize short contacts and negative d norm values on the surface are related to the presence of the N2-H2A� � �O3 hydrogen bonds in the crystal structure.Weak C1-H1� � �O2 and C6-H6� � �O1 contacts are showed by dim red spots (Fig. 5).The 2D fingerprint plots quantitatively visualize the H� � �O/O� � �H, H� � �H, H� � �C/C� � �H, and H� � �N/N� � �H interactions (Fig. 6).The n-� and �-� stacking interactions, located in the middle region of the fingerprint plot, play an integral role in the overall crystal packing, contributing 16.6% (Fig. 6a).The most significant contacts are H� � �O/O� � �H and H� � �H, contributing 34.9% and 33.7%, respectively, while the H� � �C/C� � �H contacts contribute 11.0%, and the H� � �N/ N� � �H contacts contribute 3.8% to the Hirshfeld surface (Fig. 6b-6e).The Hirshfeld surfaces mapped over shape-index, curvedness, electrostatic potential, and fragment patches are shown in Fig. 7.The pattern of orange and blue triangles on the shape-index surface (Fig. 7a) shows the characteristic feature of �-� interactions.Since curvedness plot (Fig. 7b) shows flat regions, it is evident that the title molecules are arranged in planar stacking (Spackman et al., 2009).

DFT calculations
The molecular structure of the title compound in the gas phase was optimized using density functional theory (DFT) (Neese et al., 2009) with the standard B3LYP-D3BJ method with the basis set def2-TZVP (Hanwell et al., 2012), default SCF and geometrical convergence criteria as implemented in the Orca 5.0.4 package (Neese, 2018(Neese, , 2022)).The input files were prepared from the CIF file using Avogadro 1.98.1 software (Hanwell et al., 2012).The calculated bond lengths and bond angles for the title compound are presented in Table 2 along with the corresponding crystallographic data (from the CIF file) for comparison•The computed results agree well with the experimental crystallographic data.Electron distribution in the frontier molecular orbital (FMOs), i.e. the highest occupied MO (HOMO; À 6.357 eV) and the lowest unoccupied MO (LUMO; À 2.592 eV) with a LUMO-HOMO gap of 3.765 eV, are illustrated in Fig. 8.The HOMO is less distributed on the naphthyl acetyl group while LUMO is more distributed.When the energy gap is small, the molecule exhibits high polarizability and enhances its chemical reactivity.The calculated energies and related parameters are presented in Table 3.The hardness and softness values are important parameters in understanding the chemical reactivity of a compound and stability index of a ligand.Compounds formed with a ligand exhibiting higher dipole moment values are generally more stable (Zhan et al., 2003).
The energy band gap is shown.

Molecular electrostatic potential (MEP)
The molecular electrostatic potential (MEP) map, generated using !B97M-V/def2-TZVP (Mardirossian & Head-Gordon, 2016) basis sets with the Orca 5.0.4 software package (Neese, 2022), was used to broadly predict reactive sites for electrophilic and nucleophilic attack in the title compound.The map, drawn using VMD 1.9.4 (Humphrey & Schulten, 1996) and Multiwfn 3.8 (Lu & Chen, 2012;Zhang & Lu, 2021), is shown in Fig. 9.In the crystal, the molecular charge distribution is governed by the MEP.The electrostatic potential in the MEP map varies increasingly according to a red < white < blue color scheme [ranging from À 35.80 kcal mol À 1 (extreme red) to 51.87 kcal mol À 1 (extreme blue)].

Synthesis and crystallization
0.5 g of 2-acetyl-6-acetamido-5-nitronaphthalene were dissolved in 30 mL of MeOH, 3 mL of concentrated H 2 SO 4 was, and the reaction was refluxed at 353 K for 6 h.After the reaction was complete, it was quenched with 10 mL of ice water, precipitating yellow solids, and filtered to obtain the target product.The MeOH was dissolved and red transparent block-shaped crystals were cultured at 277 K in the refrigerator (Xu et al., 2017).

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.

Figure 4
Figure 4View of the three-dimensional Hirshfeld surface mapped over d norm .

Figure 6
Figure 6 The two-dimensional fingerprint plots showing (a) all interactions, and delineated into (b) O� � �H/H� � �O, (c) H� � �H, (d) C� � �H/H� � �C, and (f) N� � �H/H� � �N interactions [the d e and d i values represent the distances (in A ˚) from a point on the Hirshfeld surface to the nearest atoms inside and outside the surface, respectively].

Table 3
Calculated energies for the title compound.

Table 2
Comparison of selected (X-ray and DFT) geometric data (A ˚, � ).

Table 4
Experimental details.