The optimal shape of 4H1NA with bond lengths and angles were derived and computed with the help of DFT theory and B3LYP functions 6-311 + + G (d, p). The structural and electrical properties change when an aromatic ring is being changed by the molecules with two unique functionalities. Table 1 contrasts the 4H1NA optimized molecule's bond lengths and angles with the CIF of an experimental crystal structure [14] and the molecule structure is shown in shown in Fig. 1. The bonds which exist between the carbon atoms as single and double bonds are easily recognizable with bond length values and are found to be with a value of about 1.40 (C3 – C5 = C4-C5 = C5-C9 = C7-C11 = C10-C16 = C15-C19 = C16-C17 = C10-C14)[24].
Optimized molecular geometry
Experimental and computed bond lengths for functional substituents like carbonyl (C7-O12 = 1.121; ex. 1.11), methylene (C7-H13 = 1.01; ex. 0.862), and hydroxy (O1-H3 = 0.987; ex. 1.03) are essentially same. End cyclic bond angles of C - C - C in the benzene ring are as follows: C4-C2-C5 = 119.56° (exp. 120.11°), C2-C4-C6 = 117.45° (exp. 118.17°), C2-C5-C8 = 118.18° (exp. 118.24°), C10-C6-C11 = 116.35° (exp. 114.13°). As the bond angle shows shortness with an increase in the size of the central atom, however bond angle shows inclement with an increase in the size of the ligand atom [25]. Lone pairs cause the bond angle to decrease, which increases the bond pairs' repulsion and causes them to draw nearer to one another. As shown the C = O site is with more electronegative effect than OH, so the bond angle C5-C9-O11 = 123.12° is slightly bigger than the O1-C2-C4 = 121.33° bond angle. For 4H1NA, the experimentally determined and computationally determined bond lengths had RMSD and R2 values of 0.963 and 0.921 respectively. The experimental and computed results were closely associated, as shown by the discussion above.
Table 1
The Geometrical Characters in terms of Bond Length (Å) and Bond Angle (º) for 4H1NA.
Bond length (Å) | Bond angle (º) |
Parameter | B3LYP/6-311 + + G ) | Experimental | Parameter | B3LYP/6-311 + + G | Experimental |
O1-C3 | 1.223 | 1.237 | C3-C4-H9 | 117.14 | 116.70 |
O1-H5 | 0.879 | 1.160 | C6-C7-H9 | 121.18 | 121.48 |
C3-C4 | 1.321 | 1.262 | C6-C8-O12 | 123.12 | 121.73 |
C5-H7 | 1.101 | 0.857 | O12-C8-H14 | 123.25 | 123.27 |
C5-C10 | 1.321 | 1.305 | C2-C5-C12 | 121.05 | 120.83 |
C6-O12 | 1.342 | 1.102 | C5-C8-H14 | 118.68 | 116.85 |
Bond angle (º) |
C2-O1-H3 | 101.12 | 101.31 | C6-C10-C15 | 120.23 | 120.81 |
O1-C2-C4 | 121.23 | 121.44 | C6-C10-H16 | 119.41 | 117.58 |
O1-C2-C5 | 115.71 | 115.11 | C15-C10-H16 | 117.31 | 118.24 |
C4-C2-C5 | 119.66 | 120.13 | C11-C17-H20 | 117.56 | 118.44 |
IR Analysis
The molecule, had 21 atoms and 57 modes (3n-6) of vibration, had its vibrational frequencies calculated using the B3LYP technique utilizing the basis set 6-311 + + G (d, p) (20 are stretching vibrations, 19 bending vibrations, 21 CH vibrations, 18 torsion stretching, and 3 out-of-plane stretching vibrations). Using 6-311 + + G (d, p) basis set, the wavenumbers in the IR region are determined [26]. They were then scaled by 0.961. The Gaussian 09 [18] and VEDA4.0 software’s [22] were used to examine all the analyzed vibrations of the molecule.
Figure 2 (A) Theoretically calculated FT-IR spectra (B) Experimental Infrared spectra of 4H1NA. (C)Theoretically calculated Raman spectra of 4H1NA.
While Fig. 2 (A, B) depicts theoretical Raman, Fig. 2 (C) depicts experimental and computed IR spectra. The theoretically determined intensity and the number of in-phase vibrational waves were compared. The IR values discovered agreed well with the data that had previously been published [8]. The RMSD and R2 values for the experimentally determined and theoretically analysed FT-IR were 1.01 and 0.899, respectively. It indicates the strong correlation between the theoretical and experimental analysis. Further down, we examine few of the significant vibrations and some of their features, like intensities.
C − H vibrations
In an aromatic structure, C-H vibrations of stretching are detected in 3101–3001 cm− 1, which is typical location for their rapid detection [27]. Gunase karan et al. [28] determined symmetric and asymmetric C-H stretching vibrations in the range 3101 − 3001 cm− 1 and 2990 − 2850 cm− 1 respectively. In molecule of reference, the FT-IR bands as determined computationally at 3076, 3073, 3062, 3047, 3042, 3038, and 2890 cm− 1 corresponds to C-H stretching vibrations as pure modes. The title chemical included six aromatic C-H bonds. Due to an increase in the intensity of the vibrations due intermolecular hydrogen bonding lowers the O-H stretching wavenumber units within the range 3510 − 3210 cm-1, however the free -OH group considerably absorbs in a range 3701 − 3583 cm− 1 [29]. The estimated wavenumber at 3116 cm− 1, when compared to the known values, shows positive reflection of over 97% PED, which is due to hydrogen bonding. Research backs up the behavior rhythm that is similar. The intramolecular Hydrogen-bonding between O-H...O makes aldehyde's C = O bond weak, causing carbonyl to appear at a lower wavenumber than anticipated, at 1614, 1336 cm− 1. O-H stretching occurs at the lower side, or 3116 cm-1, in a similar way [30].
C–C and C = O vibrations
The C–C stretching bands observed are found be at 1430–1650 cm− 1 [31]. In between also a strong doublet is found to get formed in a range 1622-1401cm− 1 which is found to due to conjugate substituent like C–C [31]. Six carbon atoms have been found to be observed in a range value of 1650 − 1410 cm− 1 [31], which are found to be linked to skeletal vibrations. The stretching vibrations observed for C–C as observed in the computed study are found to be observed at 1580, 1565, 1321, and 1015cm− 1, and the mixed modes of vibration occur at 1545, 1487, 1432, 1321, 1281, 1211, 1178, 1152, 1121, 1057, 941, 834, 744, 412cm− 1.
The harmonic frequencies as computed and the reference values are in good agreement. The C = O stretching vibrations are found to be in range of 1721 − 1621 cm− 1, and for this molecule the observed vibrations correspond to 1623cm− 1 corresponding to pure mode with a PED assignment of 55%. Additionally, the 1254 and 712 cm− 1 FT-IR bands showed mixed bands of vibration (C = O) corresponding to 16 and 12% PED value respectively.
Electron Localization Function (ELF) Diagram
Numerous techniques have been developed to reconcile chemically the molecule with quantum chemical postulates. One such technique is the Electron Localization Function by Becky and Edgecombe [32], makes a clear relationship between the chemical nature and the electron density localization. The function determines the spatial arrangement of localization factors connected to core, as bonding and nonbonding electron pairs.
The quantitative study on aromaticity of the molecule, like, the chemical structure, chemical reactivity, molecular bonding, can be learned from electron localization function measurement [33]. Figure 3 displays 3-dimensional representations of ELF values (using a color scale resembling a map's hues and as shaded contour) (A). Red is used to indicate high ELF levels (between 1.3 and 1.1), yellow to green with moderate ELF (between 0.6 and 1.2), and blue for low ELF levels. The regions with strong Pauli repulsion surrounds the H- atom with single electron highlighted in red. The region which surrounds the carbon have similar spin electrons and are close enough as shown by blue area. The surface in a shaded map showing the projections in 4H1NA are shown in Fig. 3(B) as per the electron localization function. The ELF values for C-C and C-H covalent bond positions are high, confirming the electron localization in those regions. The small electron localization zones in between the inner shell and valence shells corresponding to heavy atoms as like oxygen are illustrated by green and blue rings as like the regions which surround the nuclei of both oxygen atoms.
Mulliken atomic charge
The Calculation of Mulliken atomic charge shows a crucial role in quantum chemical calculations and systems molecular calculations due to atomic charge influence on polarity, acidity-basicity behavior, polarizability, electron position and a variety of other characteristics related to molecule [34]. The distribution of charge on atoms imply the emergence of donor/acceptor relationship involved in charge transfer spectra of the molecule. Figure 4 displays the polarity distribution of reference molecule that was calculated using the Mulliken method, the computational methods. It also gives important details on the NMR chemical shifts in addition to the aforementioned. Three charge components were used to estimate charges in the Mulliken population study: No charge = 0, multiplicity = singlet (N), Negative charge = -1 (N + 1), multiplicity = doublet, and Positive charge = + 1 (N-1), multiplicity = doublet. According to the data, it is clear that the 4H1NA C4 atom that is connected to the (C = O) functional group with large positive atmosphere. This is because of the more electronegativity of an atom present which attracted ring's C atoms electrons.
Thermodynamical properties
Enthalpy, specific heat, and other thermodynamic properties were calculated using ORCA software using same basis set over 100 to 500 K temperature range. The findings are shown in Table 2. Entropy (So), specific heat capacity (Cp), and enthalpy (En) are growing thermodynamic functions because of the increase in molecular oscillation frequency with temperature rises (Ho) Uniform distribution was used to explain this connection between thermodynamic constants and temperature increase [65] [35]. The values of specific heat and enthalpy at 100 K entropy were discovered to be 66.87, 13.54, and 100.91, respectively. When the temperature is increased to 510 K, the values of (So), (Cp), and (Ho) increase to 122.11, 62.187, and 117.397, respectively. Temperature has a positive effect on thermodynamical parameters, as shown in Fig. 5. The results above show that 4H1NA has the good stability in respect to thermochemistry. The linear and quadratic formulas as used for the observation of R2 factor for thermodynamical characteristics: 1.000 for (So), 0.987 for (Cp), and 0.954 for (Ho). The graphs for the fitting equations below
S = 0.15T + 53.2226…………………….……. (7)
Cp = 0.142T – 0.5611…………………………. (8)
H = 0.0001T2 + 0.0009T + 102.0014 ……….. (9)
The 2nd law of thermodynamics [35] enables us to compute additional thermodynamically associated energy and the direction of chemical reactions using thermodynamic data.
Table 2
Effect of Temperature of thermodynamics of 4H1NAat B3LYP/6–311 + + G (d, p).
Temperature (K) | Entropy Cal/Mol-Kelvin | Specific heat Cal/Mol-Kelvin | Enthalpy kcal/mol |
100 | 66.873 | 12.542 | 100.761 |
200 | 81.383 | 24.872 | 102.725 |
298.15 | 95.094 | 38.009 | 106.017 |
400 | 109.11 | 50.821 | 110.541 |
500 | 121.17 | 61.383 | 116.281 |
UV-Vis and electronic properties
The combination of the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) referred to as a "FMO," and it is crucial for understanding the chemical, optical, Ultraviolet and visible spectrum, and electrical properties of molecules [36]. The Ultraviolet and Visible spectra of 4H1NA making use of MeOH was captured on a spectrometer. The theoretical calculation of the UV-vis spectrum of 4H1NA using Methanol as the solvent phase is presented in Fig. 6. (A, B). the Frontier Molecular Analysis with the help of computational methods the electronic properties of molecules 4H1NA were investigated (d, p).
This also makes predictions for several conjugated-system reactions as well as the most unstable region in an electron sphere [37]. Significant donor orbitals are shown in the HOMO, whereas conspicuous acceptor orbitals are seen in the LUMO. The HOMO, HOMO-2, and HOMO-1 LUMO orbitals underwent the requisite electronic transfer, as shown by the FMO energy stages of the reference molecule, as mentioned in Table 3. The color red shows positive phase, while the color green shows negative phase. The energy difference between the HOMO and LUMO is 3.999 eV, HOMO-1 and LUMO+ 1 are 5.668 eV, and HOMO-2 and LUMO+ 2 are 5.999eV, as depicted in Fig. 7. As seen in Fig. 7, the highest occupied molecular orbital of the compound 4H1NA is mostly focused throughout the entire molecule, with the exception of the H atoms. The lowest unoccupied molecular orbital is similarly pointed on the ring, and the oxygen atoms of the C = O and OH groups. The max values and vibrational strengths of the 4H1NA molecule have been determined using (TD-DFT), known as time-dependent density functional theory, in which the polarizable continuum model (PCM) was used to take solvent effects into consideration. Table 4 lists the vibrational strengths in a gas phase and Methanol solvent along with an experimental and estimated max values. With MeOH as the solvent, the experimental max were discovered at 315 nm and 359 nm, respectively. Three transitions in the Ultra-Violet Visible region are predicted by the TD-DFT determination. By utilizing B3LYP, the intense electronic excitation at 331.49 nm (3.7496 eV) with a vibrational strength f = 0.1805 in the Gas phase, and 333.25 nm (3.6089 eV) with vibrational strength f = 0.189 in Methanol for 4H1NA as indicated in Table 3 were both detected. The powerful electronic transitions at 290.31 nm in gas phase and 286.50 nm in MeOH, as determined by CAM-B3LYP, are listed in Table 3. Ionization potential, electronegativity, electron affinity, chemical hardness, chemical softness, chemical potential, and electrophilicity index are a few more relevant variables that were derived utilizing HOMO-LUMO energy phase.
According to Table 4, the chemical hardness of 4H1NA was 2.1157; a more chemical hardness value denotes a material's chemical stability. Similar to this, the electronegativity potential, which determines the electron attraction in a covalent bond was determined as the flow of electrons between Highest occupied and lowest unoccupied molecular orbitals, results in a strong electrophilicity index of 4.8721 (4H1NA). Conceptual Density Functional Theory (CDFT), was applied to examine biochemical properties and find active spots, using a number of points including electrophilicity, chemical hardness, and chemical potential. An important CDFT-based indicator was used to evaluate bioactivity is an electrophilicity index [38], chemical softness value of 0.48822, the title compound was deemed to be harmless.
Because of the positive overlap of population, a positive value implies a high bonding cooperation, a negative value suggests a strong anti-bonding contribution, and zero value shows no bonding participation. The anti-bonding, bonding, and non-bonding states of ligands are identified using the OPDOS diagrams that contrast their donor-acceptor properties. The PDOS represented the arrangement of fragment orbitals assisting the molecular orbital.
Table 3
Comparative Electronic Characteristics of 4H1NA obtained experimentally and computationally
λmax (nm) | Band gap (eV) | Oscillatory Strength | Assignments |
EXPERIMENTAL | | | |
MeOH | | | |
316 | 3.89 | - | - |
B3LYP |
Obtained | | | |
Gas State | | | |
329.45 | 2.9981 | 0.0899 | H→L (97%) |
324.14 | 2.9113 | 0.0002 | H-2→L (95%) |
311.72 | 2.9418 | 0.0697 | H-1→L (92%) |
MeOH | | | |
322.25 | 2.9078 | 0.1278 | H→L (98%) |
318.30 | 2.7586 | 0.1201 | H-1→L (93%) |
315.24 | 2.7826 | 0.0098 | H-2→L (95%) |
CAM-B3LYP |
GAS State | | | |
290.31 | 3.1432 | 0.1245 | H→L (96%) |
268.23 | 3.5164 | 0.0003 | H-2→L (82%) |
277.15 | 3.3448 | 0.2136 | H-1→L (83%) |
MeOH | | | |
289.50 | 3.0712 | 0.2117 | H→L (97%) |
284.06 | 3.2127 | 0.0003 | H-2→L (86%) |
279.61 | 3.2605 | 0.1646 | H-1→L (865%) |
Table 4
Energy values calculated by B3LYP/6-311 + + G (d, p) method
Parameter | Values |
EHomo(eV) | -5.35235 |
ELumo(eV) | -3.34704 |
Ionization potential | 7.35235 |
Electron affinity | 3.34704 |
Energy gap(eV) | 5.01421 |
Electronegativity | 5.39170 |
Chemical potential | -5.39780 |
Chemical hardness | 3.01545 |
Chemical softness | 0.38993 |
Electrophilicity index | 5.87650 |
Intermolecular Interactions
Crystal Explorer 17.5 [40] was used to conduct a Hirshfeld surface (HS) investigation [39] to characterize the molecular interactions within the title chemical's crystal. The Hirshfeld surfaces of 4H1NA are shown in Fig. 8, together with the shape index, curvedness, de and di, and fragment patches. Shape index, curvedness, and fragment patch values range from − 0.8789 to 0.9349, -4.4780 to 0.1329, and 0.0001 to 12.011, respectively, whereas di and de values range from 2.0002 to 3.5134 and 2.0049 to 3.3587 Table 5 shows the lowest, highest, and mean values for each 3D surface. Figure 8 displays the title compound's standard resolution molecular Hirshfeld surface (dnorm) (A).
The surface could use in identification of molecular interactions that often occur. The dnorm value with negative sign in which the molecular interactions are larger than Vander Waals radii. Hirshfeld surface is colored red, white, or blue to represent the dnorm value. Longer interactions with a positive dnorm value are depicted in blue, whereas closer encounters with a negative dnorm value are displayed in red. The vander Waals separation is equal to the contacts in the white patches, which have a dnorm value of 0. The title compound's di and de are depicted in Fig. 8 (B and C).
Two distances are determined for each location on the iso-surface: de (the separation in between the point and the closest nucleus out of the surface) and di (distance in between point and the nucleus close to surface). Using de and di, the normalized contact distance (dnorm) is calculated. The shape index, identifies the complementarity between the molecules in the crystal packing [41], is one of the fundamental components of the Hirshfeld analysis. Intermolecular complementarity zones are represented by points on the surface shape index that have a variety of colors, as seen in Fig. 8 (D). The red dots represent the concave regions of atoms in molecules that are stacked on top of one another.
Table 5
Hirshfeld Surface Property for 4H1NA.
Mode | Minimum Interaction | Mean Interaction | Maximum Interaction |
dnorm | -0.0398 | 0.3823 | 0.9575 |
di | 2.0002 | 2.6576 | 3.5134 |
de | 2.0049 | 2.6652 | 3.3587 |
Shape Index | -0.8789 | 0.2767 | 0.9349 |
curvedness | -4.4780 | -0.9729 | 0.1329 |
Fragment patches | 0.0000 | 5.6144 | 12.011 |
The crystal surface's convex portion is shown by blue dots, which denote the molecule's ring structure. A molecular form's surface area can be calculated from its curvature [33]. The curvedness of compound 4H1NA is represented Fig. 8 (E); it ranges from − 4.4780 to 0.1329; low curvedness values correspond to flat shaped areas on the surface, while high curvedness values correspond to sharp edged like curvature and tend to the surface in spots, showing the interaction in between neighboring molecules. The blue border between flat parts mentions the stacking interactions between flat areas.