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Efficient Synthesis, Spectroscopic and Quantum Chemical Study of 2,3-Dihydrobenzofuran Labelled Two Novel Arylidene Indanones: A Comparative Theoretical Exploration

Rahul Ashok Shinde1,2, Vishnu Ashok Adole2, Bapu Sonu Jagdale,1,2*, Thansing Bhavsing Pawar1, Bhatu Shivaji Desaleand Rohit Shankar Shinde2

1Department of Chemistry, Mahatma Gandhi Vidyamandir’s Loknete Vyankatrao Hiray Arts, Science and Commerce College Panchavati (Affiliated to SP Pune University, Pune), Nashik-422 003, India

2Department of Chemistry, Mahatma Gandhi Vidyamandir’s Arts, Science and Commerce College (Affiliated to Savitribai Phule Pune University, Pune), Manmad-423104

Corresponding Author Email: jagdalebs@gmail.com

DOI : http://dx.doi.org/10.13005/msri/170207

Article Publishing History
Article Received on : 4 Jun 2020
Article Accepted on : 21 Jul 2020
Article Published : 22 Jul 2020
Plagiarism Check: Yes
Reviewed by: Mr.Sandip S. Pathade
Second Review by: Ayyappan Elangovan
Final Approval by: Vijai Anand
Article Metrics
ABSTRACT:

Indanone and 2,3-dihydrobenzofuran scaffolds are considered as special structures in therapeutic science and explicitly associated with various biologically potent compounds. In the present disclosure, we report the synthesis of two new 2,3-dihydrobenzofuran tethered arylidene indanones via an environmentally adequate and viable protocol. The two compounds revealed in this have been characterized well by analytical methods; proton magnetic resonance (PMR), carbon magnetic resonance (CMR). The Density Functional Theory (DFT) study has been presented for the spectroscopic, structural and quantum correlation between  (E)-2-((2,3-dihydrobenzofuran-5-yl)methylene)-2,3-dihydro-1H-inden-1-one (DBDI) and (E)-7-((2,3-dihydrobenzofuran-5-yl)methylene)-1,2,6,7-tetrahydro-8H-indeno[5,4-b]furan-8-one (DBTI). Optimized geometry, frontier molecular orbital, global reactivity descriptors, and thermodynamic parameters have been computed for DBDI and DBTI. DFT/B3LYP method using basis set 6-311++G (d,p) has been employed for the computational study. Mulliken atomic charges are established by using 6-311G (d,p) basis set. Besides, molecular electrostatic potential for DBDI and DBTI is also explored to locate the electrophilic and nucleophilic centres.

KEYWORDS: DFT; HOMO-LUMO; Molecular Electrostatic Potential; 6-311++G(d,p); (E)-2-((2,3-dihydrobenzofuran-5-yl)methylene)-2,3-dihydro-1H-inden-1-one; (E)-7-((2,3-dihydrobenzofuran-5-yl)methylene)-1,2,6,7-tetrahydro-8H-indeno[5,4-b]furan-8-one

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Shinde R. A, Adole V. A, Jagdale B. S, Pawar T. B, Desale B. S, Shinde R. S. Efficient Synthesis, Spectroscopic and Quantum Chemical Study of 2,3-Dihydrobenzofuran Labelled Two Novel Arylidene Indanones: A Comparative Theoretical Exploration. Mat. Sci. Res. India; 17(2).


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Shinde R. A, Adole V. A, Jagdale B. S, Pawar T. B, Desale B. S, Shinde R. S. Efficient Synthesis, Spectroscopic and Quantum Chemical Study of 2,3-Dihydrobenzofuran Labelled Two Novel Arylidene Indanones: A Comparative Theoretical Exploration. Mat. Sci. Res. India; 17(2). Available from: https://bit.ly/3jt8huf


Introduction

In the past few years, research on indanones and related compounds has been explored and they are found to exert an expansive range of biological properties.1-12 Importantly, they are the exceptionally valuable synthetic equivalents for the synthesis of wide variety of organic compounds having an excellent biologic profile.13-16 Many bioactive natural products are indanone based molecules. Some noticeable examples (Fig 1) 1-methoxy-6-methyl-3-oxo-2,3-dihydro-1H-indene-4-carbaldehyde (1), isopaucifloral F (2), 4-hydroxy-7-methyl-2,3-dihydro-1H-inden-1-one (3), Paucifloral F (4), Pterosin B  (5). These noteworthy naturally derived compounds are known as powerful medicinal agents.17-22 Donepezil (6) is one of the most important indanone structures which have been proficiently used for the treatment of Alzheimer’s disease due to its acetyl cholinesterase inhibitor activity. On the other hand, some eye catching examples of drugs containing dihydrobenzofuran are tasimelteon (9), 1-(2,3-dihydrobenzofuran-5-yl)propan-2-amine (10), 1-(2,3-dihydrobenzofuran-5-yl)-N-methylpropan-2-amine (11) and ((1R,2R)-2-(2,3-dihydrobenzofuran-4-yl)cyclopropyl) methanol (12). The 2-arylidene indanone compounds have been investigated as potent agents for treatment of Alzheimer’s disease, breast cancer and leukaemia, as tubulin depolymerizing agents and many other significant pharmacological applications. 1, 23 A medicinally important structure which is being used as sleep inducing agent is Ramelteon (7). Ramelteon binds with MT-1 and MT-2 receptor. It contains a tricyclic synthetic molecule: 1,2,6,7-tetrahydro-8H-indeno[5,4-b]furan-8-one (8). The 2,3-dihydrobenzofuran natural products have pulled in expanding consideration because of their unusual structural highlights and the wide scope of biological activities.[24] The benzofuran and 2,3-disubstituted benzofuran scaffolds are present in countless natural products that exhibit incredible profile of biological activities, such as antimicrobial, antiviral, anti-inflammatory antioxidant, and anticancer activities.25-29 In recent times, these compounds have been investigated to have various biological activities.30-37 Henceforth benzofuran containing compounds may be used to design and generate new capacity therapeutic candidates having exceptional importance in the subject of the new drug research.38-40 The use of green chemistry principles has been great advantage for the environment.41-54

Figure 1: Some noticeable examples of indanone and 2,3-dihydrobenzofuran containing biologically active compounds

Click on image to enlarge

Theoretical calculations based on DFT have been successfully explored largely in past few years to determine various structural aspects of synthetically and pharmacologically vital organic motifs.55-58 DFT/B3LYP method using various basis set has been found to be very crucial for investigating structural, chemical, and spectroscopic properties of the molecules.59-63 Considering all mentioned properties and future scope of these molecules, we have designed 2,3-dihydrobenzofuran tethered two important synthetic compounds (scheme 1) and have been explored for the investigation of their structural, chemical, electronic, thermodynamic and quantum chemical parameters. To the best of our insights, this is preliminary report on synthesis, characterization and DFT investigation of title molecules.

Scheme 1: Synthesis of 2,3-dihydrobenzofuran tethered 2-arylidene indanone derivatives

Click on image to enlarge

Methodology

Materials and Methods

The chemicals with high purity were purchased from local distributor. The chemicals were used as received without any further purification. Melting point was determined in open capillary and uncorrected. 1H NMR and 13C NMR spectra were recorded with a Bruker using CDCl3 as solvent, FT-IR spectra were obtained with potassium bromide pellets. Reaction was monitored by thin-layer chromatography using aluminium sheets with silica gel 60 F254 (Merck).

Experimental Procedure for the Synthesis of DBDI and DBTI

The synthesis of DBDI and DBTI is presented in Scheme 1. In a typical synthesis procedure, 2,3-dihydrobenzofuran-5-carbaldehyde (I, 10 mmol), 2,3-dihydro-1H-inden-1-one (II, 10 mmol) or 1,2,6,7-tetrahydro-8H-indeno[5,4-b]furan-8-one (III, 8 mmol) was added to a 25 mL flat bottom flask. To this 2 mL 40% NaOH and 5 mL ethanol were added. Then this alkaline mixture was stirred on magnetic stirrer until the formation of desired products (checked by TLC (7:3; hexane: ethyl acetate). Reaction mass was transferred to a beaker containing ice cold water, then filtered, dried and recrystallized to offer fine yellow crystals of IV or V.

Computational Details

Density Functional Theory calculations were computed on an Intel (R) Core (TM) i5 computer using Gaussian-03 program package without any constraint on the geometry.64 The geometry of the title molecules was optimized by DFT/B3LYP method using 6-311++G (d,p) basis set. Optimized geometry was made using the Gauss View 4.1 molecular visualization program. To investigate the reactive sites of the title compound, the molecular electrostatic potential was computed using the same method. All the calculations were carried out for the optimized structure in the gas phase. Mulliken atomic charges were established by using 6-311G (d,p) basis set.

Results and Discussion

Spectral Analysis of DBDI and DBTI

The spectral images are given in Fig 2 (13 = 1H NMR spectrum of DBDI, 14 = 13C NMR spectrum of DBDI, 15 =1H NMR spectrum of DBTI, 16 =  13C NMR spectrum of DBTI).

a. (E)-2-((2,3-dihydrobenzofuran-5-yl)methylene)-2,3-dihydro-1H-inden-1-one (DBDI) : M.F. C18H14O2; Pale yellow crystals; M.P. 97 ºC; 1H NMR (500 MHz, Chloroform-d) δ – 7.90 (m, 1H), 7.64 (t, J = 2.1 Hz, 1H), 7.60 (td, J = 7.3, 1.2 Hz, 1H), 7.58 – 7.51 (m, 2H), 7.48 (dd, J = 8.3, 1.9 Hz, 1H), 7.47 – 7.38 (m, 1H), 6.86 (d, J = 8.3 Hz, 1H), 4.65 (t, J = 8.7 Hz, 2H), 3.99 (d, J = 2.1 Hz, 2H), 3.28 (t, J = 8.7 Hz, 2H); 13C NMR (126 MHz, Chloroform-d) δ – 194.45, 161.81, 149.48, 138.33, 134.39, 134.29, 132.25, 131.76, 128.28, 128.19, 127.58, 127.54, 126.09, 124.28, 109.97, 71.95, 32.63, 29.40

b. (E)-7-((2,3-dihydrobenzofuran-5-yl)methylene)-1,2,6,7-tetrahydro-8H-indeno[5,4-b]furan-8-one (DBTI) : M.F. C20H16O3; Yellow crystals; M.P. 147ºC;  IR (KBr, cm-1) – 2916.37, 1643.35, 1564.27, 1490.97, 1427.32, 1328.95, 1280.73; 1H NMR (500 MHz, Chloroform-d) δ 7.56 (d, J = 2.2 Hz, 1H), 7.52 (s, 1H), 7.47 (dd, J = 8.3, 1.9 Hz, 1H), 7.28 (s, 1H), 7.02 (d, J = 8.0 Hz, 1H), 6.86 (d, J = 8.3 Hz, 1H), 4.67 (dt, J = 14.6, 8.8 Hz, 4H), 3.93 (d, J = 2.0 Hz, 2H), 3.56 (t, J = 8.9 Hz, 2H), 3.28 (t, J = 8.7 Hz, 2H); 13C NMR (126 MHz, Chloroform-d) δ – 194.69, 161.73, 160.45, 141.39, 134.86, 133.83, 132.88, 132.20, 128.34, 128.13, 127.51, 125.03, 124.56, 115.13, 109.93, 72.44, 71.93, 32.23, 29.41, 28.54

Figure 2: Spectral images of the synthesized compounds (13 = 1H NMR  spectrum of DBDI, 14 = 13C NMR spectrum of DBDI, 15 = 1H NMR  spectrum of DBTI, and 16 = 13C NMR spectrum of DBTI)

Click on image to enlarge

 

Computational Study

The optimized molecular structure of title molecules is depicted in Fig 3. Molecular structures 17 and 18 represent optimized geometrical structures for DBDI and DBTI respectively. The optimized molecular geometry provides good deal of information about the spatial orientation of various atoms in a molecule. From optimized molecular structures, it can be easily seen that both DBDI and DBTI possess C1 point group symmetry due to overall asymmetry of the molecules. Furthermore, it is evident that both the molecules contain non-planar dihydrofuran ring [Fig 3 (19 and 20)]. The non-planarity of dihydrofuran can be attributed to CH2 group (adjacent to oxygen atom) which is either above or below the plane. Due to this fact, both the molecules lack molecular plane (sh). It can also be seen that remaining skeleton of these molecules are in perfect planar position and therefore can have extended conjugation. This information is very much useful for the determination of various spectroscopic entities. The optimized geometrical parameters like bond lengths and bond angles of DBDI and DBTI are presented in Table 1A and 1B. The C9-O13 bond is 1.2195 Å in DBDI and C9- 1.2216 Å in DBTI. The olefinic C14-C15 bond is 1.3489 Å and 1.3491 Å in DBDI and DBTI molecules respectively. Other bond lengths are also in good agreement with the optimized structures. Bond angle data of both molecules are also in good agreement.

Figure 3: Optimized molecular structures of DBDI (17), DBTI (18), side view of DBDI (19), side view of DBTI (20)

Click on image to enlarge

 

Table 1A: Optimized geometrical parameters of DBDI by DFT/ B3LYP with 6-311++G(d,p) basis set

Bond lengths (Å)

C1-C2

1.3955

C9-C14

1.4968

C20-C24

1.39

C1-C6

1.4016

C10-H11

1.0966

C22-C25

1.0828

C1-H7

1.0846

C10-H12

1.0966

C22-C24

1.396

C2-C3

1.392

C10-H14

1.5142

C22-C28

1.5123

C2-H8

1.0852

C14-C15

1.3489

C24-O34

1.3588

C3-C4

1.3967

C15-H16

1.0892

C28-H29

1.0949

C3- C10

1.5162

C15-C17

1.4554

C28-C30

1.5454

C4-C5

1.3949

C17-C18

1.4111

C28-H33

1.0919

C4-C9

1.485

C17-C19

1.4153

C30-H31

1.089

C5- C6

1.3908

C18-C20

1.3917

C30-H32

1.0935

C5- H26

1.0841

C18-H21

1.0803

C30-O34

1.4575

C6- H27

1.0841

C19-C22

1.3806

C9-O13

1.2195

C19-H23

1.0852

Bond angles (°)

C2-C1-C6

121.0843

C3-C10-H12

111.0202

C24-C20-H25

120.7525

C2-C1-H7

119.5183

C3-C10-C14

103.716

C19-C22-C24

119.7843

C6-C1-H7

119.3974

H11-C10-H12

106.8518

C29-C22-C28

132.2832

C1-C2-C3

118.7113

C11-C10-C14

112.1608

C24-C22-C28

107.8768

C1-C2-H8

120.2384

H12-C10-C14

112.1657

C20-C24-C22

121.8831

C3-C2-H8

121.0502

C9-C14-C10

108.9035

C20-C24-O34

124.6712

C2-C3-C4

119.9694

C9-C14-C15

119.6675

C22-C24-O34

113.443

C2-C3-C10

128.8339

C10-C14-C15

131.4291

C22-C28-H29

110.9107

C4-C3-C10

111.1967

C14-C15-H16

113.501

C22-C28-C30

101.3765

C3-C4-C5

121.5946

C14-C15-C17

131.9157

C22-C28-C33

113.4248

C3-C4-C9

109.8763

H16-C15-C17

114.5833

H29-C28-C30

111.6154

C5-C4-C9

128.529

C15-C17-C18

124.5419

H29-C28-H33

107.733

C4-C5-26

118.3789

C15-C17-C19

117.4689

C30-C28-H33

111.7831

C4-C5-C26

119.9287

C18-C17-C19

117.9891

C28-C30-C31

114.1679

C6-C5-C26

121.6924

C17-C18-C20

122.1142

C28-C30-H32

111.7492

C1-C6-C5

120.2615

C17-C18-H21

119.8067

C28-C30-O34

106.6458

C1-C6-C27

119.5862

C20-C18-H21

118.0781

H31-C30-H32

109.2705

C5-C6-C27

120.1523

C17-C19-C22

120.4148

H31-C30-O34

107.3237

C4-C9-O13

126.7014

C17-C19-H23

119.0694

H32-C30-O34

107.3357

C4-C9-H14

106.3076

C22-C19-H23

120.5157

C24-O34-C30

107.5144

O13-C9-H14

126.991

C18-C20-C24

117.8125

C3-C10-H11

111.0122

C18-C20-H25

121.4346

 

Table 1B: Optimized geometrical parameters of DBTI by DFT/ B3LYP with 6-311++G(d,p) basis set

Bond lengths (Å)

C1-C2

1.3997

C10-H12

1.0967

C24-H32

1.359

C1-C6

1.3939

C10-C14

1.5147

C26-H27

1.095

C1-H7

1.0832

C14-C15

1.3491

C26-C28

1.5455

C2-C3

1.3921

C15-H16

1.0893

C26-H31

1.0919

C2-H8

1.0851

C15-C17

1.4554

C28-H29

1.089

C3-C4

1.4029

C17-C18

1.4112

C28-H30

1.0936

C3-C10

1.5171

C17-C19

1.4152

C28-H32

1.4572

C4-C5

1.3896

C18-C20

1.3917

C33-H34

1.0948

C4-C9

1.4812

C18-H21

1.0803

C33-H35

1.0907

C5-C6

1.3917

C19-C22

1.3806

C33-C36

1.546

C5-C33

1.5076

C19-H23

1.0852

C36-H37

1.094

C6-O39

1.3649

C20-C24

1.39

C36-H38

1.0892

C9-O13

1.2216

C20-H25

1.0828

C36-O39

1.4579

C9-C14

1.4959

C22-C24

1.396

C10-H11

1.0969

C22-C26

1.5123

Bond angles (°)

C2-C1-C6

118.5211

H12-C10-C14

111.9372

C22-C26-C28

101.3739

C2-C1-H7

121.2674

C9-C14-C10

108.9942

C22-C26-H31

113.4203

C6-C1-H7

120.2114

C9-C14-C15

119.5279

H27-C26-C28

111.6235

C1-C2-C3

119.9287

C10-C14-C15

131.4776

H27-C26-H31

107.7282

C1-C2-H8

119.3749

C14-C15-H16

113.5279

C28-C26-H31

111.775

C3-C2-H8

120.6958

C14-C15-C17

131.868

C26-C28-H29

114.1682

C2-C3-C4

120.3155

H16-C15-C17

114.604

C26-C28-H30

111.7328

C2-C3-C10

128.7497

C15-C17-C18

124.5193

C26-C28-O32

106.6493

C4-C3-C10

110.9348

C15-C17-C19

117.4754

H29-C28-H30

109.266

C3-C4-C5

120.4952

C18-C17-C19

118.0053

H29-C28-O32

107.3348

C3-C4-C9

109.9704

C17-C18-C20

122.0958

H30-C28-O32

107.3437

C5-C4-C9

129.5343

C17-C18-H21

119.7491

C24-O32-C28

107.5129

C4-C5-C6

118.2297

C20-C18-H21

118.1546

C5-C33-H34

110.6631

C4-C5-C33

133.2551

C17-C19-C22

120.4133

C5-C33-H35

113.1536

C6-C5-C33

108.4696

C17-C19-H23

119.0843

C5-C33-C36

101.1394

C1-C6-C5

122.5085

C22-C19-H23

120.5024

H34-C33-H35

107.1137

C1-C6-O39

124.3126

C18-C20-C24

117.8164

H34-C33-C36

112.2093

C5-C6-O39

113.175

C18-C20-H25

121.4388

H35-C33-C36

112.6213

C4-C9-O13

126.6343

C24-C20-H25

120.7445

C33-C36-H37

111.603

C4-C9-C14

106.3681

C19-C22-C24

119.7754

C33-C36-H38

114.1268

O13-C9-C14

126.9976

C19-C22-C26

132.2866

C33-C36-O39

106.8638

C3-C10-H11

111.2344

C24-C22-C26

107.8829

H37-C36-H38

109.2168

C3-C10-H12

111.3211

C20-C24-C22

121.8918

H37-C36-O39

107.3892

C3-C10-C14

103.7313

C20-C24-O32

124.6749

H38-C36-O39

107.3122

H11-C10-H12

106.8163

C22-C24-O32

113.4303

C6-O39-C36

107.235

H11-C10-C14

111.8977

C22-C26-H27

110.9233

From the frontier molecular orbital (FMO) analysis the information about charge transfer within the molecule can be anticipated. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is very crucial parameters for the investigation of quantum chemical parameters. Fig 4 (21) demonstrates HOMO-LUMO picture of DBDI and Fig 4 (22) is for DBTI. The charge transfer phenomenon supports the bioactive property of the molecule. The FMO study gives an understanding of the reactivity of the molecule and the active site can be established by the distribution of frontier orbital. The HOMO-LUMO study is also used for predicting the most reactive position in -electron systems and additionally explains several types of reactions in the conjugated frameworks. The less HOMO-LUMO energy gap suggests the molecule is softer and a large gap suggests a molecule is harder. The HOMO-LUMO gap in DBDI is 3.7018 eV and in DBTI is 3.6898 eV. Due to the low energy gap in the molecule DBDI, this molecule will have more ease in the charge transfer within the molecule than the molecule DBTI. This also suggests higher chemical reactivity. In the present study quantum chemical parameters have been established which provide good deal of comparison between these two molecules. Electronic parameters are tabulated in Table 2 and reactivity descriptors in Table 3. The ionization potential (I) provides information about ionization capability of the molecule whereas electron affinity (A) provides information regarding electron attraction capability. Our study reveals that ionization in DBTI is easier than DBDI; as former has less value of ionization potential. On the contradictory DBDI has more electron affinity than DBTI.  The absolute hardness (η) and global softness (σ) corresponds to the HOMO-LUMO energy gap. The chemical potential (Pi) can be explored to determine the ionization capability of an electron. The global electrophilicity index (ω) provides idea about electrophilic character of the molecule. The electronic charge transfer is predicted by ΔNmax. The global reactivity descriptors’ study indicates both the molecules are strong electrophiles and therefor can undergo nucleophilic attack easily. The molecule DBDI involves more electron transfer than DBTI as predicted by ΔNmax; however it requires little bit more energy than DBTI.

Figure 4: FMO picture; 21 for DBDI and 22 for DBTI

Click on image to enlarge

Table 2: Electronic parameters

Entry

ETotal (a.u.)

EHOMO

(eV)

ELUMO

(eV)

ΔE

(eV)

I

(eV)

A

(eV)

DBDI

-845.0077

-5.9698

-2.2680

3.7018

5.9698

2.2680

DBTI

-997.6827

-5.9434

-2.2536

3.6898

5.9434

2.2536

 Note: I = −EHOMO & A= −ELUMO

Table 3: Quantum chemical parameters

Entry

χ

(eV)

ɳ

(eV)

σ

(eV-1)

ω

(eV)

Pi

(eV)

ΔNmax

(eV)

Dipole moment (Debye)

DBDI

4.1189

1.8509

0.5403

4.5830

-4.1189

2.2553

3.5520

DBTI

4.0985

1.8449

0.5420

4.5525

-4.0985

2.2215

3.0116

Note: χ = (I + A)/2; ɳ = (I − A)/2; σ = 1/ɳ; ω = Pi2/2ɳ; Pi = −χ; ΔNmax = −Pi/ɳ

The MEP plots are displayed in Fig 5. The properties like dipole moment, electronegativity, partial charges and chemical reactivity of any molecule can be correlated with the aid of molecular electrostatic potential. The molecular electrostatic potential is a total charge distribution of a molecule space. The regions of positive, negative and neutral potentials are indicated by different colours. Red suggests a zone of negative electrostatic potential and the white zone of positive electrostatic potential. In the present case, it can be observed than negative electrostatic potential lies over oxygen atom in both DBDI and DBTI. On the other hand, the positive electrostatic potential is situated over hydrogen atoms of two aromatic rings. The blue part indicates zero electrostatic potential and it is mainly located over hydrogen atoms of dihydrofuran ring in both DBDI and DBTI. The molecule DBTI has less positive electrostatic potential than DBDI. This is due to the presence of extra dihydrofuran ring in DBTI. These zones of various electrostatic potential can give valuable data in regards to various sorts of intermolecular interactions and hence one can foresee the chemical behaviour of the molecule.

Figure 5: Molecular electrostatic potentials; 23 for DBDI and 24 for DBTI

Click on image to enlarge 

 

The different thermodynamic properties were computed from the theoretical vibrational frequencies and are presented in Table 6. The thermodynamic data disclosed in this could provide valuable insights to the other thermodynamic parameters.  In present investigation, the theoretical thermodynamic calculations based on vibrational data provided valuable insights on thermodynamic stability of the title molecules. Our study reveals that the molecule DBTI is thermodynamically more stable than DBDI. Moreover DBTI possesses more degree of translational, rotational and vibrational freedom as compared to DBDI. Also, it has higher value of heat capacity. Mulliken atomic charges of DBDI and DBTI are presented in Table 4 and Fig 6. Mulliken atomic charges give important information regarding electropositive and electronegative nature of atoms. All hydrogen atoms are electropositive as they are attached to atoms having more electronegativity than hydrogen. Out of two oxygen atoms in DBDI molecule, 34O is more negative with Mulliken atomic charge value of -0.346342. On the other hand, 39O is the most negative with Mulliken atomic charge value of -0.357181.

Figure 6: Mulliken atomic charges; 25 for DBDI and 26 for DBTI

Click on image to enlarge

Table 4: Mulliken atomic charges

DBDI

DBTI

Atom

Charge

Atom

Charge

1  C

-0.077564

1  C

-0.066467

2  C

-0.073918

2  C

-0.071827

3  C

-0.124734

3  C

-0.136440

4  C

-0.045291

4  C

-0.028203

5  C

-0.027585

5  C

-0.151259

6  C

-0.091625

6  C

0.237673

7  H

0.098412

7  H

0.103104

8  H

0.083048

8  H

0.081455

9  C

0.229546

9  C

0.228244

10  C

-0.099451

10  C

-0.097862

11  H

0.144775

11  H

0.141638

12  H

0.144745

12  H

0.141771

13  O

-0.317630

13  O

-0.330787

14  C

-0.235269

14  C

-0.230793

15  C

0.027322

15  C

0.025347

16  H

0.098993

16  H

0.097262

17  C

-0.093882

17  C

-0.092018

18  C

-0.050912

18  C

-0.050598

19  C

-0.034868

19  C

-0.035806

20  C

-0.081547

20  C

-0.081903

21  H

0.101597

21  H

0.102766

22  C

-0.171504

22  C

-0.171159

23  H

0.089924

23  H

0.089055

24  C

0.233928

24  C

0.233868

25  H

0.101132

25  H

0.101140

26  H

0.099328

26  C

-0.193460

27  H

0.098860

27  H

0.140271

28  C

-0.193507

28  C

-0.012403

29  H

0.140606

29  H

0.125239

30  C

-0.012580

30  H

0.125046

31  H

0.125473

31  H

0.134920

32  H

0.125273

32  O

-0.346495

33  H

0.135247

33  C

-0.165668

34  O

-0.346342

34  H

0.139763

35  H

0.143083

36  C

-0.012170

37  H

0.120278

38  H

0.120579

39  O

-0.357181

The theoretical IR spectrum of DBTI is computed at DFT/B3LYP method using 6-311++G (d,p) basis set. The theoretical and experimental IR spectra are Figure 7A and Figure 7B respectively. There are total 111 fundamental modes of vibrations as per 3N-6 formula. The important experimental IR vibrations are 2916.37, 1643.35, 1564.27, 1490.97, and 1427.32 cm-1. The 2916.37 cm-1 is due to the asymmetric C-H vibrations. The similar vibration is at 2917.36 cm-1 in the theoretical spectrum. The C=O frequency is appeared at 1643.35 cm-1. The carbonyl stretching is located at 1679.68 cm-1 in the simulated IR spectrum. The C=C vibrations are 1564.27, 1490.97, and 1427.32 cm-1. There is good agreement between the theoretical and experimental IR spectra.

Figure 7: A. Theoretical IR B. Experimental IR

Click on image to enlarge

 

Table 5: Thermodynamic properties

Parameter

DBDI

DBTI

E total (kcal mol-1)

Translational

Rotational

Vibrational

179.528

0.889

0.889

177.751

205.961

0.889

0.889

204.183

Heat Capacity at constant volume, Cv (cal mol-1K-1)

Translational

Rotational

Vibrational

61.812

2.981

2.981

55.850

71.567

2.981

2.981

65.605

Total entropy S (cal mol-1K-1)

Translational

Rotational

Vibrational

128.401

42.590

34.076

51.735

140.894

43.033

34.964

62.897

Zero point Vibrational Energy Ev0 (kcal mol-1)

169.82521

194.65241

Rotational constants (GHZ):

1.2333834   0.1314400   0.1190901

1.0102184      0.0921864     0.0847426

E (RB3LYP) (a.u.)

-845.0077

-997.6827

 

Conclusions

In the present research work, DFT/B3LYP method at 6-311++G (d,p) basis set has been used for the exploration of various important structural, electronic and quantum chemical parameters of title molecules. An elaborative correlation among DBDI and DBTI has been presented. The properties like the HOMO-LUMO energy gap, charge transfer phenomenon, molecular electrostatic potential, and global reactivity descriptors have been explored using the same level of method. Additionally, important thermodynamic statistics have been computed and these two molecules have been compared based on this data to elucidate their thermodynamic behaviour. The theoretical analysis of the two title compounds furnished the following results. Both DBDI and DBTI possess C1 point group symmetry due to the overall asymmetry of the molecules. The molecule DBDI possesses a higher dipole moment than the molecule DBTI. The HOMO-LUMO gap in DBDI is 3.7018 eV and in DBTI is 3.6898 eV.  The MEP analysis suggests that the molecule DBTI has less positive electrostatic potential than DBDI. Thermochemical data reveals that the molecule DBTI is thermodynamically more stable than DBDI. Moreover, DBTI possesses more degree of translational, rotational, and vibrational freedom as compared to DBDI. The 39O is the most negative with Mulliken atomic charge value of -0.35718 in the DBTI molecule whereas 34O is more negative with Mulliken atomic charge value of -0.346342 in DBDI.

Acknowledgments

Authors acknowledge Central instrumentation facility, Savitribai Phule Pune University, Pune for NMR and Mass spectral analysis. Authors also would like to thank Lokenete Vyankatrao Hiray Arts, Science and Commerce College Panchavati, Nashik and Arts, Science and Commerce College, Manmad for permission and providing necessary research facilities. Authors would like to express their sincere and humble gratitude to Prof. Arun B. Sawant for Gaussian study. Dr. Aapoorva Hiray, Coordinator, MG Vidyamandir institute, is gratefully acknowledged for Gaussian package.

Funding

We have not received any kind of fund for the research work.

Conflict of Interest

Authors declared that he do not have any conflict of interest regarding this research article.

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