Fluorine substituent effect on the structure,electronic and spectra (vibrational,14 N NQR,UV) properties of carbo-borazine

Abstract

In this research, fluorine substituent influence on the electronic structure, ¹⁴NQR and electronic spectra of carbo-borazine molecule was explored at M062X/6-311G(d,p) level of theory. Energetic stability of possible isomers was examined. QTAIM results illustrated ring critical points (RCP) and the electrostatic potential of RCP reported. The curvature of electron density perpendicular to ring plane at RCP was considered to exploring of aromaticity of these molecules. The ELF map were used to description of chemical bonds (C-H, C-B, C-N, B-F, N-F and B-N) in the studied molecules. Natural transition orbital (NTO) analysis was employed to origin of corresponding transition of λ_max value. Fluorine substituent influence on the computed λ_max and ¹⁴N NQR parameters values was studied.

Keywords

carbo-borazine fluorine substituent QTAIM ELF

Introduction

Carbomers are extended molecules, which are attained by the insertion of -C≡C- unit in each bond of a molecule.^1–3 For instance, carbo-benzene (C₁₈H₆, D_6h) can be created with of six -C≡C- units in each bond of benzene. Preparation of this “bare” carbo-benzene has been unsuccessful. Computational studies have been illustrated electronic structure and properties of cabo-benzene.^4–9 But, synthesis of carbo-benzene derivatives has been reported.^10–12 Also, the inorganic analogues of carbo-benzene can be made. Carbo-borazine (B₃C₁₂N₃H₃, D_3h) is obtained from the inclusion of six -C≡C- units in each bond of borazine (B₃N₃H, D_3h). Preparation of this molecule was impossible, due to dimerization tendency of this molecule. The aromaticity of this molecule was examined, and it was illustrated that the electronegativity difference between B and N atoms disturbed the electronic delocalization. The computed induced magnetic field exhibited nonaromatic property in this molecule.¹³

In this research, we attracted to explore fluorine substituent influence on the structure, vibration and ¹⁴N NQR spectra and electronic properties of carbo-borazine at M062X/6-311G(d,p) level of theory. The curvature of electron density perpendicular to ring plane at RCP was considered to exploring of aromaticity of these molecules.

Computational methods

Optimizations of the considered molecules were done using the 6-311G(d,p) basis set^14–17 and hybrid functional of Truhlar and Zhao (M06-2X)¹⁸ by software package of Gaussian 09.¹⁹ Harmonic vibrational frequencies were verified that the optimized molecules have no imaginary frequency.

The Hirshfeld population analysis was made based on optimized molecules. This analysis is a very general atomic population way well-known on deformation density partition.²⁰

The computations of quantum theory of atoms in molecules analysis (QTAIM) and interacting quantum atoms (IQA) method^21–24 were calculated with the AIMAll software package.²⁵ The “Promega” basin integration method using fine interatomic surface mesh was applied.

Atomic dipole corrected Hirshfeld atomic charge (ADCH),²⁶ the electron localization function (ELF)²⁷ and curvature of electron density perpendicular to ring plane at RCP²⁸ were attained by Multiwfn 3.8 package.^29–31

Electronic transitions of the molecules were explored using TD-DFT³² at M062X/6-311G(d,p) level of theory. 30 lowest singlet excited states were evaluated.

Natural Transition Orbital (NTO) analysis³³ was accomplished with TD-DFT calculations on optimized molecules. The NTO distributions of the most intensity transition of molecules were provided using Chemissian version 4.2.3 software.³⁴

Results and discussion

Energetic aspects

Figure 1 presents the structures of carbo-borazine (CB) and fluorinated-carbo-borazine molecules. Energy and relative energy values of these molecules are summarized in Table 1. It can be observed B-fluorinated molecules are more stable than N-fluorinated molecules.

Figure 1.

The structures of carbo-borazine and fluorinated-carbo-borazine molecules.

Table 1.

Energy (E, a.u), relative energy (ΔE, kcal/mol), dipole moment (μ, Debye), Electronic spatial extent (ESE, a.u), electron density at RCP (ρ(3,+1), e.Å⁻³), curvature electron density (CED) at RCP and electrostatic potential at RCP in carbo-borazine and fluorinated carbo-borazine molecules at M062X/6-311G(d,p) level of theory.

Molecule	E	ΔE	μ	ESE	ρ(3,+1)	CED	ESP
CB	−699.2531	-	0.00	6167.67	3.00 × 10⁻⁶	−1.6 × 10⁻⁶	−3.27 × 10⁻²
BF	−798.5632	0.00	1.07	6986.19	2.98 × 10⁻⁶	−3.9 × 10⁻⁶	−2.89 × 10⁻²
BF2	−897.8732	0.00	1.07	6944.41	2.93 × 10⁻⁶	−3.9 × 10⁻⁶	−2.51 × 10⁻²
BF3	−997.1831	0.00	0.00	7861.28	2.89 × 10⁻⁶	−1.5 × 10⁻⁶	−2.13 × 10⁻²
NF	−798.4022	101.04	3.33	7784.50	2.81 × 10⁻⁶	−3.7 × 10⁻⁶	−2.22 × 10⁻²
NF2	−897.5505	202.47	3.30	8787.48	2.62 × 10⁻⁶	−2.9 × 10⁻⁶	−1.18 × 10⁻²
NF3	−996.6982	304.27	0.00	8675.27	2.44 × 10⁻⁶	−1.3 × 10⁻⁶	−1.69 × 10⁻³

Interacting Quantum Atoms (IQA) approach

The interacting quantum atoms (IQA) method is used to computation of the repulsion energy values of between of B and N nucleuses with F atom (V_nn(A,B)) in the fluorinated-carbo-borazine systems (Table 2). It can be detected greater V_nn(N,F) values in compared to V_nn(B,F) values. This consequence is well-matched with existence of LP/LP electron repulsion in the N-F bond. This impact is negligent in the B-F bond. Hence, the B-fluorinated molecules include greater energetic stability respect to N-fluorinated molecules.

Table 2.

Repulsion energy between nucleus of atom B and nucleus of atom F, also atom N and nucleus of atom F (V_nn(A,B), a.u), in fluorinated molecules at M062X/6-311G(d,p) level of theory.

Molecule	Bond	V_nn(A,B)
BF	B-F	17.87
BF2	B-F	17.87
BF3	B-F	17.88
NF	N-F	24.00
NF2	N-F	24.02
NF3	N-F	24.04

Polarity

Computed dipole moment values of the considered systems are given in Table 1. It can be deduced greater polarity in the N-fluorinated molecules than B-fluorinated molecules. This tendency is well-matched with larger polarity of N-F bond than B-F bond. Computed atomic dipole corrected Hirshfeld atomic charge (ADCH) of B and N atoms of the considered molecules are recorded in Table 3. It can be realized more positive ADCH values for N atoms of in the N-fluorinated molecules respect to B atoms in the B-fluorinated systems.

Table 3.

Computed atomic dipole corrected Hirshfeld atomic charge (ADCH) of B and N atoms in carbo-borazine and fluorinated carbo-borazine molecules at M062X/6-311G(d,p) level of theory.

Molecule	Q(B)		Q(N)
	B-H	B-F	N-H	N-F
CB	0.119	-	−0.006	-
BF	0.120	0.305	−0.006	-
BF2	0.120	0.305	−0.005	-
BF3	-	0.305	−0.005	-
NF	0.121	-	−0.004	0.230
NF2
NF3	0.124	-	−0.002	0.231

Electronic spatial extent (ESE)

ESE is estimated as the probability value of the electron density times the distance from the center of mass of a molecule. More it is features physical property of the electron density volume round the molecule. Greater defused electron cloud is provided with increasing of the range. Computed ESE values of the investigated systems are recorded in Table 1.

Computed ESE values reveal larger ESE values in fluorinated systems than CB molecule. This increased ESE attributed to more electronegative and spatially extended fluorine atoms. On the other hand, B-F and N-F are more polar bonds than B-H and N-H bonds, respectively, and electron pull toward periphery. Also, F substituents include larger size and diffuseness than H atoms. These values expose replacing of hydrogens of carbo-borazine with fluorine substituents increase ESE of system.

It can be deduced larger ESE values in the B-fluorinated molecules than N-fluorinated molecules. In the N-fluorinated molecules, both N and F atoms are electron-withdrawing, pulling electron density inward toward the N–F bond. There is a more polarized B–F bond in the B-fluorinated molecules. Electron-deficient character of boron causes the electron density moves more noticeable, expanding the electron cloud.

QTAIM

Results of QTAIM computations displays bond critical points (BCP) between CC, CB, and CN units. It can be found the BCP is nearer to C in CN units, nearer to B in CB units, and nearer to B in BN units. The shift of BCP adopts the atomic radii pattern, BCP is place at middle in CC units.

On the other hand, QTAIM reveals the position of ring critical point (RCP) is changed. The CB, BF3 and NF3′s RCPs are located at (00,0), RCP of BF and NF are located at (0.00, 0.00, −0.67) and (0.23,-0.58, 0.00), respectively.

RCP of BF2 and NF2 are located at (0.00, 0.00, −0.63) and (0.00, 0.00, 0.58), respectively. It can be seen 1.21 Å displacement along z-axis. RCP of BF and NF are placed at (0.00, 0.00, −0.67) and (0.23, −0.58, 0.00), respectively.it can be found, −0.23, 0.58, and 0.67 Å displacement along x, y, and z-axes, respectively.

On the other hand, the RCP electrostatic potential of ring critical point (RCP) is altered (Table 1). It can be deducing more negative ESP values for B-fluorinated structures than N-fluorinated structures.

Aromaticity

Electron density at RCP is faithfully correlated to aromaticity of resultant ring.²⁸ Computed ρ(3,+1) values of the studied systems are given in Table 1. The larger the density, the stronger the aromaticity. As a result, B-fluorinated molecules have a stronger aromaticity than N-fluorinated molecules.

Now, we estimate the curvature of electron density perpendicular to ring plane at RCP. This parameter explores noteworthy relationship with the aromaticity of ring. More negative curvature suggests greater aromaticity. Comparison between the two curvatures again displays that B-fluorinated molecules have a stronger aromaticity than N-fluorinated molecules.

Two provided results are compatible with more stability energetically of B-fluorinated molecules respect to N-fluorinated molecules.

ELF

The ELF function explores the amount of electron delocalization in chemical systems, facilitating covalent bonding analysis by poor in electrons and red for rich-electron regions. ELF maps of carbo-borazine and fluorinated carbo-borazine molecules in the defined plane by three atoms are presented in Figure 2. Located hydrogen atoms in red areas, representative the electron deficiency distinctive of protons. But, B, C, and N atoms are surrounded by blue areas, suggesting the presence of electron density.

Figure 2.

ELF maps of carbo-borazine and fluorinated carbo-borazine molecules in the defined plane

The ELF map similarly describes chemical bonds (N-F, B-F, C-B, C-H, B-N, and C-N) colored between red and orange. Furthermore, the electron pairs round fluorine atoms seem as orange areas.

¹⁴NQR parameters

Electric field gradient tensor

Table 4 represents EFG tensors (q_zz, q_yy and q_xx) of ¹⁴N in studied molecules. Computed q_yy, q_xx values of N atoms of B-fluorinated molecules are smaller than CB molecule. But, computed q_zz values of N atoms of B-fluorinated molecules are larger than CB molecule.

Table 4.

Electric field gradient tensor (q_ii, a.u), Nuclear quadrupole coupling constant (χ_ii, MHz), asymmetry parameter (η) and nuclear quadrupole resonance frequencies (MHz) of, ¹⁴NQR spectra of carbo-borazine and fluorinated carbo-borazine molecules at M062X/6-311G(d,p) level of theory.

Molecule	Atom	Q_zz(a.u)	Q_yy(a.u)	Q_xx(a.u)	χ_zz	χ_yy	χ_xx	η	υ₊	υ₋	υ₀
CB	N	1.03188	−0.6331	−0.3988	4.956	3.041	1.915	0.227	3.998	3.436	0.563
BF	N1	1.05703	−0.6474	−0.4096	5.077	3.110	1.967	0.225	4.093	3.522	0.571
	N2	1.0321	−0.6325	−0.3996	4.957	3.038	1.919	0.226	3.998	3.438	0.560
BF2	N2	1.05703	−0.6474	−0.4096	5.077	3.110	1.967	0.225	4.093	3.522	0.571
	N1	1.0321	−0.6325	−0.3996	4.957	3.038	1.919	0.226	3.998	3.438	0.560
BF3	N	1.08245	−0.6621	−0.4204	5.199	3.180	2.019	0.223	4.189	3.609	0.580
NF	N(F)	1.58197	−1.3949	−0.187	7.598	6.700	0.898	0.764	7.149	4.248	2.901
	N(H)	1.02714	−0.6318	−0.3954	4.933	3.034	1.899	0.230	3.984	3.416	0.568
NF2	N(F)	1.57662	−1.3891	−0.1876	7.573	6.672	0.901	0.762	7.122	4.237	2.885
	N(H)	1.02266	−0.6313	−0.3914	4.912	3.032	1.880	0.235	3.972	3.396	0.576
NF3	N(F)	1.57158	−1.3833	−0.1883	7.548	6.644	0.904	0.760	7.096	4.226	2.870

Computed q_xx and q_zz values of N atoms bonded to F in N-fluorinated molecules are larger than CB molecule. But, computed q_yy values of N atoms of bonded to F in N-fluorinated molecules are smaller than CB molecule. Computed q_xx and q_yy values of N atoms bonded to H in N-fluorinated molecules are larger than CB molecule. But, computed q_zz values of N atoms of bonded to H in N-fluorinated molecules are smaller than CB molecule.

Nuclear quadrupole coupling constant

Nuclear quadrupole coupling constants (χ_ii) of ¹⁴N in considered molecules are collected in Table 4. χ_zz, χ_yy and χ_xx values of N atom of B-fluorinated molecules are larger than CB molecule.

Computed χ_zz and χ_yy values of N atoms bonded to F in N-fluorinated molecules are larger than CB molecule. This increased χ_zz and χ_yy values can be attributed to large electronegative of F atoms, which enhances electron asymmetry at N atom. This growing of electron asymmetry increases quadrupole interaction. But, computed χ_yy values of N atoms of bonded to F in N-fluorinated molecules are smaller than CB molecule. Computed χ_zz, χ_yy and χ_xx values of N atoms bonded to H in N-fluorinated molecules are smaller than CB molecule.

Asymmetry parameter

Computed asymmetry parameters (η) of ¹⁴N atom in considered molecules are collected in Table 4. These value demonstrate altered distribution of electric charge around the N nucleus respect to cylindrical symmetry in nitrogen molecules.

No significance changes are observed in the η values of N atoms of B-fluorinated molecules respect to CB molecule. Also, no dependency of the η values on the number of F atoms are found.

On the other hand, the computed η values of N atoms bonded to F are larger than N atoms bonded to H in N-fluorinated molecules. Also, these values are larger than the corresponding values in CB molecule. This increased η values can be attributed to electron withdrawing ability of F atoms, which enhances electron asymmetry at N atom.

NQR frequencies

Calculated NQR frequencies of ¹⁴N in considered molecules are given in Table 4. The N atoms of these molecules are located in the electric field of the other nuclei, hence, the symmetry of the EFG surrounding them alters. This alteration results in the splitting of the energy levels of ¹⁴N nuclei, accordingly, three NQR frequencies for ¹⁴N will be seen. The variances between the frequencies of nitrogen in these molecules can be associated to the direct participation of the electron pairs of N atom through chemical bond realization or diatropic current in the cycle.

No significance changes are observed in the υ₊, υ₋, and υ₀ values of N atoms of B-fluorinated molecules respect to CB molecule. Also, no dependency of the η values on the number of F atoms are found.

On the other hand, the υ₊, υ₋, and υ₀ values of N atoms bonded to F are larger than N atoms bonded to H in N-fluorinated molecules. These values are larger than CB molecule.

Electronic spectra

The carbo-borazine molecule fits to the D_3h point group. The strongest peak (f_max) is the S₀→S₂ transition. This transition appears at 270.20 nm (f = 0.8424). TD-DFT consequences expose no one transition evidently governs, and probing the appropriate canonical orbitals is not predominantly useful in this example:

HOMO-9 → LUMO

HOMO-2 → LUMO+1

HOMO-1 → LUMO+1

HOMO-1 → LUMO+2

HOMO → LUMO

Percentages of transitions contributions are 2.50%, 5.23%,41.35%, 3.39% and 41.45%, respectively.

Accordingly, we accomplished natural transition orbital (NTO) analysis on the most intense singlet-singlet transition for the carbo-borazine molecule. NTO analysis permits a direct clarification of electronic transitions in terms of a hole-particle representation. It can be inferred, this excitation implicates mostly the promotion of one π→π* electronic transition (Figure 3).

Figure 3.

The NTO distributions of the most intensity transition of carbo-borazine molecule.

Figure 4.

The HOMO and LUMO plots of carbo-borazine.

Calculated λ_max values in the fluorinated systems are listed in Table 5. Evaluation of fluorine substituent on the λ_max value exposes that red-shift in the N-fluorinated systems. It can be initiate red-shift in the λ_max values with increasing of fluorine atom numbers. Then, blue-shift is deduced in the B-fluorinated molecules. A blue-shift in the λ_max values with growing of fluorine atom numbers.

Table 5.

Computed λ_max, oscillator strength (f), frontier orbital energies (eV) and HOMO-LUMO gap (eV) values of carbo-borazine and fluorinated carbo-borazine molecules at M062X/6-311G(d,p) level of theory.

Molecule	λ_max	f	E(HOMO)	E(LUMO)	Gap
CB	270.19	0.8425	−7.70	−1.36	6.34
BF	266.40	0.8327	−7.73	−1.41	6.32
BF2	256.82	0.7573	−7.82	−1.34	6.47
BF3	250.06	0.7517	−7.97	−1.08	6.89
NF	272.23	0.8068	−7.90	−1.68	6.22
NF2	274.56	0.7665	−8.10	−1.92	6.18
NF3	279.29	0.6748	−8.30	−2.10	6.20

HOMO → LUMO transition has most involvement in S₀→S₂ transition. Figure 4 shows plots of HOMO and LUMO of carbo-borazine molecule. Molecular orbital analysis exposes that energy gap between two orbitals are increased with increasing of number of F atoms in the B-fluorinated systems. Contrary trend is detected the N-fluorinated systems (Table 5). Hence, λ_max values drop with growing of fluorine atom numbers in the B-fluorinated systems. However, higher λ_max values are realized with growing of fluorine atom numbers in the N-fluorinated systems.

Conclusion

Computational investigation of fluorine substituent influence on the electronic structure, spectroscopic properties of carbo-borazine molecule at M062X/6-311G(d,p) level of theory indicated B-fluorinated systemswere more stable than N-fluorinated systems, energetically. Larger polarity was established in the N-fluorinated molecules are more stable than B-fluorinated systems. Computed ESE data exposed larger ESE values in fluorinated systems than CB molecule. More negative ESP values were provided for B-fluorinated systems than N-fluorinated systems. The curvature of electron density perpendicular to the ring plane at the RCP explored noteworthy relationship with the aromaticity of cycle. More negative curvature denoted stronger aromaticity. Tis parameter revealed stronger aromaticity in B-fluorinated molecules than N-fluorinated molecules. The υ₊, υ₋, and υ₀ values of ¹⁴N NQR spectra for N atoms bonded to F were larger than N atoms bonded to H in N-fluorinated molecules. These values were larger than CB molecule. The λ_max values of electronic spectra decreased with growing of fluorine atom numbers in the B-fluorinated systems. But, higher λ_max values were found with growing of fluorine atom numbers in the N-fluorinated systems.

Footnotes

ORCID iD

Reza Ghiasi

Consent to participate

All the co-authors consent to participate.

Consent to publish

All the co-authors consent to publish.

Author's contribution

Reza Ghiasi: Conceptualization, Data curation, investigation, Formal analysis, writing, review and editing.

Nahid Shajari: methodology, Data curation, writing, review and editing.

Funding

No funds or grants were received.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data availability

All data generated or analyzed during this study are included in this published article.

Clinical trial number

Not applicable

References

Chauvin

Carbomers

. “Carbomers”. I. A general concept of expanded molecules. Tetrahedron Lett 1995; 36: 397–400.

Chauvin

. “Carbomers”. II. En route to [C,C]6carbo-benzene. Tetrahedron Lett 1995; 36: 401–404.

Maraval

Chauvin

. From macrocyclic oligo-acetylenes to aromatic RingCarbo-Mers. Chem Rev 2006; 106: 5317–5343.

Godard

Lepetit

Chauvin

. DFT Exploration of structural and magnetic properties of [n]Annulene ring Carbomers. Chem Commun 2000: 1833–1834. doi:10.1039/b005961g.

Lepetit

Godard

Chauvin

. Aromaticity and Homoaromaticity of Annulene ring Carbomers. New J Chem 2001; 25: 572–580.

Lepetit

Silvi

Chauvin

. ELF Analysis of out-of-plane aromaticity and in-plane Homoaromaticity in carbo Annulenes and Pericyclynes. J Phys Chem A 2003; 107: 464–473.

Zou

Lepetit

Coppel

, et al. Ring carbo-Mers: From questionable Homoaromaticity to bench aromaticity. Pure Appl Chem 2006; 78: 791–811.

Soncini

Fowler

Lepetit

, et al. Aromaticity of ring carbo-Mers of [N]Annulenes and [N]cycloalkanes. Phys Chem Chem Phys 2008; 10: 957–964.

Chauvin

Lepetit

Maraval

, et al. Variation of aromaticity by twisting or expanding the ring content. Pure Appl Chem 2010; 82: 769–800.

10.

Kuwatani

Watanabe

Ueda

. Synthesis of the first 3,6,9,15,18,18-hexa-substituted-1,2,4,5,7,8,10,11,13,14,16,17-dodecadehydro[18]annulenes with D6h-symmetry. Tetrahedron Lett 1995; 36: 119–122.

11.

Suzuki

Tsukude

Watanabe

, et al. Synthesis, structure and properties of 3,9,15-tri- and 3,6,9,12,15,18-hexasubstituted dodecadehydro[18]annulenes (C18H3R3 and C18R6) with D6h-symmetry. Tetrahedron 1998; 54: 2477–2496.

12.

Zhu

Duhayon

Romero-Borja

, et al. Hexaaryl-carbo-benzenes revisited: A novel synthetic route, crystallographic data, and prospects of electrochemical behavior. New J Chem 2017; 41: 3908–3914.

13.

Jalife

Audiffred

Islas

, et al. The inorganic analogues of carbo-benzene. Chem Phys Lett 2014; 610–611: 209–212.

14.

Hay

. Gaussian Basis sets for molecular calculations. The representation of orbitals in transition-metal atoms. J Chem Phys 1977; 66: 4377–4384.

15.

Krishnan

Binkley

Seeger

, et al. Self-consistent molecular orbital methods. XX. A basis set for correlated wave functions. J Chem Phys 1980; 72: 650–654.

16.

McLean

Chandler

. Contracted Gaussian basis sets for molecular calculations. I. Second row atoms. J Chem Phys 1980; 72: 5639–5648.

17.

Wachters

AJH

. Gaussian Basis set for molecular Wavefunctions containing third-row atoms. J Chem Phys 1970; 52: 1033–1036.

18.

Zhao

Truhla

. Comparative DFT study of van der Waals complexes: rare-gas dimers, alkaline-earth dimers, zinc dimer, and zinc-rare-gas dimers. J Phys Chem 2006; 110: 5121–5129.

19.

Frisch

Trucks

Schlegel

, et al. 2013, Gaussian, Inc., Wallingford CT.

20.

Hirshfeld

. Theor. Bonded-atom fragments for describing molecular charge densities. Chim. Acta 1977; 44: 129–138.

21.

Blanco

Pandás

Mckee

. Bay-type H···H “bonding” in cis-2-butene and related species: QTAIM versus NBO description. J Comput Chem 2014; 35: 1499–1508.

22.

Pendas

Blanco

Francisco

. Chemical fragments in real space: Definitions, properties, and energetic decompositions. J Comput Chem 2007; 28: 161–184.

23.

Blanco

Pendas

Francisco

. Interacting quantum atoms: A correlated energy decomposition scheme based on the quantum theory of atoms in molecules. J Chem Theory Comput 2005; 1: 1096–1109.

24.

Francisco

Pendas

Blanco

MAA

, et al. Theory. Comput. 2006; 2: 90–102.

25.

Keith

. AIMAll, Version 19.10.12. Overland Park, KS: TK Gristmill Software, 2019.

26.

Chen

. Atomic dipole moment corrected Hirshfeld population method. . J Theor Comput Chem 2012; 11: 63.

27.

Chen

. Meaning and functional form of the electron localization function. Acta Phys -Chim Sin 2011; 27: 2786–2792.

28.

Howard

Krygowski

. Benzenoid hydrocarbon aromaticity in terms of charge density descriptors. Can J Chem 1997; 75: 1174–1181.

29.

Chen

. Quantitative analysis of molecular surface based on improved marching Tetrahedra algorithm. J Mol Graph Model 2012; 38: 314–323.

30.

Chen

. Multiwfn: A multifunctional Wavefunction analyzer. J Comp Chem. 2012; 33: 580–592.

31.

. A comprehensive electron Wavefunction analysis toolbox for chemists, Multiwfn. J Chem Phys 2024; 161: 082503.

32.

Runge

Gross

EKU

. Density-Functional theory for time-dependent systems. Phys Rev Lett 1984; 52: 997–1000.

33.

Martin

. Natural transition orbitals. J Chem Phys 2003; 118: 4775–4777.

34.

Skripnikov LV. Chemissian, Version 4.2.3, Visualization Computer Program, 2014.

Fluorine substituent effect on the structure,electronic and spectra (vibrational,14 N NQR,UV) properties of carbo-borazine

Abstract

Keywords

Introduction

Computational methods

Results and discussion

Energetic aspects

Interacting Quantum Atoms (IQA) approach

Polarity

Electronic spatial extent (ESE)

QTAIM

Aromaticity

ELF

14NQR parameters

Electric field gradient tensor

Nuclear quadrupole coupling constant

Asymmetry parameter

NQR frequencies

Electronic spectra

Conclusion

Footnotes

ORCID iD

Consent to participate

Consent to publish

Author's contribution

Funding

Declaration of conflicting interests

Data availability

Clinical trial number

References

¹⁴NQR parameters