www.dergipark.gov.tr ISSN:2148-3736 El-Cezerî Fen ve Mühendislik Dergisi Cilt: 8, No: 1, 2021 (397-409) El-Cezerî Journal of Science and Engineering Vol: 8, No: 1, 2021 (397-409) DOI:10.31202/ecjse.825888 ECJSE How to cite this article Kunduracıoğlu, A., “2-Thienylboronic Acid: A DFT Study For The Spectral, Structural and Molecular Orbital Analysis” El-Cezerî Journal of Science and Engineering, 2021, 8(1); 397-409. Bu makaleye atıf yapmak için Kunduracıoğlu, A.,“2-Tienilboronik Asid: Spektroskopik, Yapısal ve Molekül Orbital Analizi Üzerine Bir DFT Çalışması” El-Cezerî Fen ve Mühendislik Dergisi 2021, 8(1); 397-409. ORCID ID:0000-0002-6421-9912 Makale / Research Paper 2-Thienylboronic Acid: A DFT Study For The Spectral, Structural and Molecular Orbital Analysis Ahmet KUNDURACIOĞLU Bursa Uludağ University, Mustafakemalpaşa Vocational College, Bursa, TURKEY akunduracioglu@uludag.edu.tr Received/Geliş: 14.11.2020 Accepted/Kabul: 17.12.2020 Abstract: In this study, due to the increasing importance of boronic acids, 2-Thhenylboronic acid and its isomers were examined in terms of structural properties and molecular orbitals. HOMO-LUMO boundary surfaces and FT-IR, FT-RAMAN analyzes were carried out with an integrated understanding. The molecule was investigated in terms of structural properties such as bond lengths, bond angles and buckling angles. Isomers of the molecule are considered separately from each other. In quantum chemical calculations, the DFT method was used at the B3LYP level and with the 6.31G * base set. These calculations were carried out using SPARTAN-14 computational chemistry package program. The results calculated for the bond lengths were found to be very close to the experimental values in the literature, with an error margin of usually between 0.45 and 1.6%. This error in bond angles occurred between 0.49% and 5.52%. Considering that the molecule has moving parts, it can be said that results are very close to experimental values. Keywords: Boronic acid derivatives, DFT, Spectral analysis, HOMO LUMO, Molecular structure 2-Tienilboronik Asid: Spektroskopik, Yapısal ve Molekül Orbital Analizi Üzerine Bir DFT Çalışması Öz: Boronik asitlerin artan önemi nedeniyle bu çalışmada, 2-Tienilboronik asid ve izomerleri, Yapısal özellikler ve molekül orbitaller bakımından incelenmiştir. HOMO-LUMO sınır yüzeyleri ve FT-IR, FT-RAMAN analizleri tümleşik bir anlayışla gerçekleştirilmiştir.Molekül, bağ uzunlukları, bağ açıları ve burkulma açıları gibi yapısal özellikleri yönüyle araştırılmıştır. Molekülün izomerleri birbirinden ayrı olarak ele alınmıştır. Kuantum kimyasal hesaplamalarda, DFT yöntemi, B3LYP düzeyinde ve 6.31G* temel seti ile kullanılmıştır. Bu hesaplamalar, SPARTAN-14 hesapsal kimya paket programı kullanılarak gerçekleştirilmiştir. Bağ uzunluklarıyla ilgili hesaplanan sonuçların, genellikler % 0.45 ile 1.6 arasında hata payıyla, literatürdeki deneysel değerlere çok yakın oldukları görülmüştür. Bağ açılarında bu hata % 0.49 ile 5.52 arasında gerçekleşmiştir. Molekülün hareketli kısımları olduğu dikkate alınırsa, deneysel değerlere son derece yakın sonuçlar alındığı söylenebilir. Anahtar Kelimeler: : Boronik asid türevleri, DFT, Spektroskopik analiz, HOMO LUMO, Molekül yapısı 1. Introduction Like other boron compounds, boronic acid (BA) and its derivatives are gaining importance in today's innovative chemical studies. The importance of boron compounds especially “O” containing ones (Figure 1.) is on the rise due to oil shortage concerns in the future. Boron has a lack of e - in its valence shell which makes boron compounds Lewis acids. Thanks to this property boron compounds can coordinate to lewis bases. Most BA derivatives exist as white crystalline solids, which can be kept and processed in the open air without further circumspection. http://www.teknolojikarastirmalar./ http://www.google.com.tr/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=xz5s9XSyulZkLM&tbnid=oCAfilol35s7FM:&ved=0CAUQjRw&url=http%3A%2F%2Fahmetatangrafiktasarim.blogspot.com%2F2011%2F06%2Ftubiad-kuruldu.html&ei=23GwUZS3GoGbtAaknYHQAQ&bvm=bv.47534661,d.Yms&psig=AFQjCNE6WroNwBybnesv1SG0F_JPplJUQQ&ust=1370604374041622 mailto:akunduracioglu@uludag.edu.tr ECJSE 2021 (1) 397-409 2-Thienylboronic Acid: A DFT Study For The Spectral,… 398 BAs are chemically stable so that they have a shelf-life for long periods. However, derivatives with an alkyl substituted and some heteroaromatic ones have been shown to have limited stability under aerobic conditions. The reactivity and properties of BA derivatives depend upon the nature of their single variable substituent particularly the type of the –C‒(BOH)2 group which is directly bonded to boron atom. Some Oxygen-containing organoboron compounds have been depicted in Figure 1 [1- 5]. Boron compounds are well known for their catalytic activities in organic and synthetic chemistry [6-12]. Borane borinic acid boric acid boronic ester boroxine (Cyclic boronic anhydride)R,R',R"= alkyl or aryl for all boronic acid Figure 1. Oxygen-containing organoboron compounds Figure 2. Isomeric forms of compound TBA (energies in Hartree) 2-Thienylboronic acid (TBA) isomers have been handled for its structural and spectral properties in this study (Figure 2). TBA is a crystalline white solid with a melting point of 138-140°C [1,3,12]. Some researchers had already performed comprehensive studies on its structural and spectral properties [14-16]. But in their study, the molecule had been handled as is. The calculations in the following study have been performed considering the isomeric structure of TBA. 2. Materials and Methods 2.1. Computational Details For computational analysis of the compound TBA, 6-31G* basis set was used in the B3LYP level of DFT method [17-19] in the SPARTAN-14 quantum chemistry suite [20,21]. For calculations, TBA has four conformations; Cis-Cis, Cis-Trans, Trans-Cis and Trans-Trans (Figure 2). Kunduracıoğlu, A. ECJSE 2021 (1) 397-409 399 Consequently, all calculations for the compound has been repeated for each of these conformations separately. The obtained results have been tabulated and discussed under corresponding divisions. MO surfaces and spectral graphics are depicted in corresponding figures in the following parts of this manuscript. For vibrational analysis, the results which software produced were used after they were corrected with a scaling factor of 0.96. There is a huge archive of spectral data for the compound TBA which had been studied by several researchers so far. 399ort his reason, in this study, the existing experimental spectroscopic and structural data have been used. Some data obtained from calculations have not been mentioned here, were added as supporting information files. 3. Results and Discussion 3.1. Structure of the Compound As mentioned in the previous pages, the compound TBA has four geometrical isomers which will be called CC, CT, TC and TT (C for Cis- and T for Trans-) respectively in the following pages (Figure 2). As can be seen from Figure 2, the TC isomeric form which has ₋729.0228020 Hartree of energy was found as the least energetic form of the compound. In this study, the molecular structure of TBA and spectral data is going to be examined according to this fact [22]. 3.1.1 Molecular Structure Like any other compound, the molecular structure of TBA is determined by bond lengths, bond angles and dihedral (torsion) angles. In corresponding tables and figures, these properties have been depicted and argued comparatively. TBA wasn’t studied peculiarly for its molecular structure. But some very congener compounds were studied experimentally by Gosh et al. and Rettig et al. in their previous studies independently from each other [15,16]. In this study, the bond length and bond angles have been compared to the results of their studies (Figure 3. a, b). a) b) Figure 3. a) 2-(2'-thienyl)pyridine and b) phenylboronic acid Calculated and experimental bond lengths are tabulated in Table 1 comparatively. As seen in Table 1, among the calculated values, the ones for TC are generally the closest results to experimental values as expected. However, it can not be said that the other results are very far from experimental measurements. The overall average is very close to the experimental results with a very small deviation which is between 0.454% and 1.611%. But the most prominent and disappointing deviation between calculated values and experimental ones is about almost 29% which corresponds to HnOn bonds. It is not surprising that excessive mobility in these groups causes such a deviation. Computationally found and experimentally measured bond angles of the compound TBA were tabulated comparatively in Table 2. It can be said at first glance that the results are more compatible, although there are many missing data in the experimental column. The values in the ECJSE 2021 (1) 397-409 2-Thienylboronic Acid: A DFT Study For The Spectral,… 400 error% column lay between 0.195% and 5.5% which can be said to change within a reasonable range. Table 1. Calculated and experimental bond lengths(Ǻ) for the conformers of TBA Again isomer TC is noticed to show relatively most realistic values and error% would be smaller if only TC were noticed. Table 2. Calculated and experimental bond angles (°) for the conformers of TBA As a presupposition, any small compound with an aromatic ring can be expected to be perfectly planar. The compound TBA is not an exception. According to the calculated values, the dihedral angles of the compound are 180° and 0.00°. Unfortunately, there is not an experimental data-set to Bond CC CT TC TT Ave. Err.% Exp* H2,O2 0.966 0.967 0.969 0.967 0.967 28.967 0.750 H1,O1 0.965 0.969 0.966 0.967 0.967 28.900 0.750 O2,B1 1.368 1.375 1.367 1.375 1.371 0.679 1.362 O1,B1 1.369 1.368 1.375 1.375 1.372 -0.454 1.378 B1,C1 1.568 1.556 1.555 1.548 1.557 -0.717 1.568 C1,S1 1.752 1.753 1.748 1.750 1.751 1.611 1.723 S1,C4 1.728 1.729 1.727 1.728 1.728 0.935 1.712 C4,H5 1.082 1.082 1.082 1.082 1.082 nc nd C4,C3 1.370 1.370 1.371 1.371 1.371 0.772 1.360 C3,H4 1.085 1.085 1.085 1.085 1.085 nc nd C3,C2 1.424 1.424 1.423 1.423 1.424 1.173 1.407 C2,H3 1.087 1.085 1.088 1.085 1.086 nc nd C2,C1 1.379 1.378 1.380 1.379 1.379 0.730 1.369 From ref: 14,15 and 16 nc= not calculated, nd: No data in lit. Angle CC CT TC TT Ave. Err.% Exp* H2,O2,B1 113.990 114.160 110.920 114.990 113.515 2.266 111.00 H1,O1,B1 112.970 110.480 113.210 114.540 112.800 1.622 111.00 O2,B1,O1 114.950 117.830 118.080 124.480 118.835 2.180 116.30 O1,B1,C1 121.790 117.650 123.360 117.480 120.070 -3.944 125.00 O2,B1,C1 123.270 124.520 118.550 118.040 121.095 1.846 118.90 B1,C1,S1 121.910 122.920 121.020 122.010 121.965 nc nd B1,C1,C2 129.260 127.770 129.600 128.320 128.738 5.523 122.00 C1,S1,C4 92.810 92.510 92.390 92.210 92.480 0.195 92.30 C2,C1,S1 108.840 109.320 109.380 109.670 109.303 -1.084 110.50 S1,C4,H5 120.390 120.300 120.420 120.360 120.368 nc nd S1,C4,C3 111.330 111.360 111.760 111.750 111.550 0.495 111.00 C4,C3,H4 123.500 123.310 123.740 123.570 123.530 nc nd C4,C3,C2 112.360 112.550 112.070 112.250 112.308 -0.876 113.30 C3,C2,H3 122.320 123.910 122.520 123.880 123.158 nc nd C3,C2,C1 114.670 114.270 114.400 114.120 114.365 1.298 112.90 H3,C2,C1 123.010 121.820 123.080 122.000 122.478 nc nd C2,C3,H4 124.140 124.140 124.190 124.180 124.163 nc nd C3,C4,H5 128.280 128.340 127.820 127.900 128.085 nc nd *= borrowed from ref (14,15 and 16, nc= not calculated, nd: No data in lit. Kunduracıoğlu, A. ECJSE 2021 (1) 397-409 401 compare those results for verifying. According to data in Table 3. TBA can be supposed to have a perfectly planar structure without bending. But it doesn’t mean the molecule is a rigid planar sheet, it bends, twists and wriggles in a limited space continually. Table 3. Calculated Dihedral angles (°) for the conformers of TBA Bond CC CT TC TT H2,O2,B1,O1 180.00 180.00 0.00 0.00 H1,O1,B1,O2 180.00 0.00 180.00 0.00 H2,O2,B1,C1 0.00 0.00 180.00 180.00 H1,O1,B1,C1 0.00 180.00 0.00 180.00 O2,B1,C1,S1 0.00 0.00 0.00 0.00 O1,B1,C1,C2 0.00 0.00 0.00 0.00 O2,B1,C1,C2 180.00 180.00 180.00 180.00 O1,B1,C1,S1 180.00 180.00 180.00 180.00 B1,C1,S1,C4 180.00 180.00 180.00 180.00 B1,C1,C2,C3 180.00 180.00 180.00 180.00 C1,C2,C3,C4 0.00 0.00 0.00 0.00 S1,C4,C3,C2 0.00 0.00 0.00 0.00 C1,S1,C4,C3 0.00 0.00 0.00 0.00 B1,C1,C2,H3 0.00 0.00 0.00 0.00 3.1.2. HOMO-LUMO Analysis and Electronic Transitions As the TC isomeric form has the minimum energy according to calculations, it has been accepted as the most stable form and other values have been compared according to this value. This conformer is 3.44, 0.09 and 2.60 kcalmol -1 more stable than CC, CT and TT isomeric forms respectively. In Table 5 calculated energies and energy differences have been presented comparatively. Figure 4. Electron transitions and energy differences between MO’s. HOMO E= -6.40 eV E= 1.1 eV E= -6.80 eV HOMO-1 LUMO+1 E= -0.80 eV ΔE2=5.6 eV ΔE1=6.0 eV ΔE3=7.5 eV ECJSE 2021 (1) 397-409 2-Thienylboronic Acid: A DFT Study For The Spectral,… 402 Energy differences were calculated according to Equation (1) below [23, 24]. ΔE= E(C 0 ) – E(TC) (1) Due to these differences between the calculated energies, TC conformer has been handled as a symbol for representing the electronic transitions and visualization of e - transfer between MO’s in Figure 4. The calculated UV-Vis spectra plots were depicted in Figure 5. Besides brief tables of transitions and HOMO LUMO surfaces for the compound have been added in the following lines. Table 4 summarizes the energy values for HOMO&LUMO boundary surfaces and in Table 5 the differences have been tabulated in different energy units. Table 4. Calculated Energies (eV) of the MO surfaces. Table 5. The energy equivalencies for the transitions between the conformers for the compound C o n fo r m e r s Energy (Hartree) Energy Differences Eq. Freq. (cm-1) Dip. Momnt (Debye) (Hartree) (kcalmol-1) (eV) CC -729.017314 0.0054880 3.443769392 0.149337261 1204.45136 2.85 CT -729.022648 0.0001540 0.096636386 0.004190586 33.79837999 4.60 TC -729.022802 0.0000000 0.0000 0.0000 0.0000 2.53 TT -729.018660 0.0041420 2.599142278 0.112710447 909.04474 5.39 Av. -729.020356 0.0024460 1.534887014 0.066559574 536.82362 3.84 3.1.3. Mulliken Charge Distribution Generally, the electronic distribution on a molecule is not homogenous because of the electronegativity differences between the atoms. This heterogeneity causes the localization of charges so that some parts of the molecule gains a negative or positive charge depending on the electronic density. The electron-rich parts of the molecule form a preferred site for electrophilic attacks and electronically poor sites are more suitable for nucleophilic attacks. M.O. CC CT TC TT Ave LUMO{+1} 0.40 0.50 1.10 1.00 0.750 LUMO -1.10 -0.90 -0.80 -0.60 -0.850 HOMO -6.70 -6.40 -6.40 -6.20 -6.425 HOMO{-1} -7.10 -6.90 -6.80 -6.50 -6.825 HOMO{-2} -8.50 -8.60 -8.60 -8.80 -8.625 HOMO{-3} -8.80 -9.10 -9.00 -8.90 -8.950 HOMO{-4} -9.60 -9.40 -9.40 -9.40 -9.450 HOMO{-5} -10.00 -9.90 -9.90 -9.60 -9.850 HOMO{-6} -10.00 -10.00 -10.00 -9.80 -9.950 HOMO{-7} -10.80 -10.40 -10.50 -10.20 -10.475 HOMO{-8} -10.90 -10.70 -10.70 -10.60 -10.725 HOMO{-9} -11.20 -10.90 -10.80 -10.70 -10.900 Kunduracıoğlu, A. ECJSE 2021 (1) 397-409 403 Mulliken charge distribution was calculated according to the DFT / B3LYP method and 6.31G* basis set. The calculated values were transferred into Graph 1 and depicted in figure 6. As can be seen in the graphic, all of the H atoms have a considerable positive charge but especially H1 and H2 which are next to O1 and O2 atoms have dramatically huge positive charges. C atoms have negative charges as expected due to S and B atoms which are not much electronegative. C2 and C3 have relatively smaller charges but C1 and C4 have obtrusive negative charges due to their neighbors. Even so, the most striking negative charges localized on the O1 and O2 atoms which are the most electronegative parts of the molecule. Table 6. Molecular orbital energies and differences forthe conformers of TBA (* From Ref. [14]) C o n fo rm er H O M O -1 H O M O L U M O L U M O + 1 ΔE (eV) λmax ΔE1 ΔE2 ΔE3 Calculated (Vac) Exp.* (Methanol) CC -7.1 -6.7 -1.1 0.4 6 5.6 7.1 206.64 221.4 174.62 236.5 CT -6.9 -6.4 -0.9 0.5 6 5.5 6.9 206.64 225.42 179.68 TC -6.8 -6.4 -0.8 1.1 6 5.6 7.5 206.64 221.4 165.31 TT -6.5 -6.2 -0.6 1 5.9 5.6 7.2 210.14 221.4 172.2 *Borrowed from Ref. (14) Figure 5. Calculated UV-Vis spectra for the isomers of TBA CC CT TC TT ECJSE 2021 (1) 397-409 2-Thienylboronic Acid: A DFT Study For The Spectral,… 404 These details can also be tracked from the models' ESP Maps depicted in Figure 6 according to color. Also, all charge values including natural and electrostatic charges can be found in the supplementary material. Figure 6. Electrostatic potential map (ESP Map) for the isomers of TBA Figure 8. Calculated Mulliken charge distribution of the isomers of TBA 3.1.4. Vibrational Spectroscopy (FT-IR and FT-RAMAN) The molecule has 13 atoms and that means 33 vibrational modes in two main parts. –B(OH)2 and ring groups. The most mechanically active part of the molecule is the –B(OH)2 group which gives motion to the molecule. It exhibits swinging, rocking and every kind of mechanical motions which adds isomeric transformations to the molecule. As a brief analysis, the frequencies and their corresponding bonds have been tabulated in Table 7 and Figure 7. In the table, the isomers of the molecule were involved comparatively. These results also can be found in supplementary material as well. Most experimental values are in an agreement with the results taken for methyl and phenylboronic acids [23,24]. Even so, some dramatic points should be underlined [17]. 1. From a rapid view, it can be said the differences between the experimental and calculated values are dramatically rising after the 3000s. 2. In the experimental spectrum, the broad peak in 3219cm -1 refers to –C(BOH)2 group which is generally seen in the 3300-3200cm -1 band due to its bonded –O-H stretch [9]. Kunduracıoğlu, A. ECJSE 2021 (1) 397-409 405 T a b le 7 . C o m p ar is o n o f th eo re ti ca l an d e x p er im en ta l F T -I R a n d F T -R A M A N s p ec tr a fo r th e co n fo rm er s o f T B A T o ta l en er g y D is tr ib u ti o n 2 ,1 τ( C -B ) (6 4 ), τ (B -O ) (2 4 ) β (C -B ) (6 4 ), β (C B O ) (3 3 ) γ( B C C τ) ( 7 6 ), γ (C B O O ) (1 2 ) β (C B O ) (4 5 ), ʋ (C -B ) (1 9 ), ʋ (C -τ ) (1 1 ), Δ 1 (R ) (1 0 ) β (C B O ) (4 8 ), β (C -B ) (1 6 ), ʋ (C -τ ) (1 5 ) τ2 R ( 7 0 ), τ (B -O ) (1 0 ), γ (B -C ) (1 0 ) τ( B -O ) (8 0 ) τ( B -O ) (3 9 ), τ 1 R ( 3 4 ), τ 2 R ( 1 4 ) β (O B O ) (4 1 ), Δ 1 (R ) (2 6 ), ʋ (C -B ) (1 3 ) τ1 R (6 7 ), τ (B 9 -O 1 0 ) (1 5 ) ʋ (C -τ ) (4 8 ), Δ 1 (R ) (2 3 ) γ( C B O O )( 6 8 ), γ (B C C τ) ( 1 6 ) γ( C -H ) (9 9 ) Δ 2 (R ) ( 6 6 ), ʋ (C -τ ) (3 2 ) γ( C -H ) (8 8 ) E x p er im en ta l1 R a m a n 3 9 3 s 4 9 8 v s 5 3 6 s 6 6 7 s F T -I R 4 5 7 w 5 4 7 m 6 4 7 s 7 1 3 s 7 9 9 s D F T / B 3 L Y P 6 .3 1 G i T T 0 .1 3 4 .2 1 1 0 .6 5 6 .4 6 0 .3 7 2 .4 2 6 4 .2 1 4 1 .3 4 3 .0 5 2 5 .6 7 4 0 .7 8 6 .0 2 6 3 .3 4 1 .7 8 3 .9 1 T T 5 9 1 3 6 1 4 9 3 2 8 3 5 6 3 9 5 4 3 9 5 1 8 5 6 3 5 8 4 6 5 8 6 6 1 7 3 1 7 5 2 8 6 3 i T C 2 .6 5 2 .0 1 1 .9 1 9 .5 4 3 .6 6 1 7 .5 1 1 5 8 .4 3 2 .4 2 1 4 .8 5 9 .5 8 1 .2 5 9 .6 1 7 5 .6 7 2 .5 6 2 .9 5 T C 4 2 1 4 1 1 4 9 3 2 5 3 9 2 4 4 6 4 7 1 5 4 7 5 5 3 5 9 2 6 6 2 6 6 3 7 3 2 7 5 2 8 4 7 i C T 5 .8 2 1 .8 4 0 .5 8 5 .7 4 7 .2 2 2 7 .0 5 1 5 3 4 .3 4 1 .8 4 2 1 .5 4 1 0 .4 1 5 8 .3 8 6 6 .0 7 1 .9 2 1 5 .0 7 C T 2 2 1 3 9 1 4 5 3 2 4 3 9 3 4 3 4 4 6 0 5 4 7 5 4 7 5 9 1 6 5 2 6 5 9 7 2 7 7 5 1 8 6 2 i C C 0 .1 4 1 .0 2 3 2 .9 5 1 2 .7 9 3 .9 1 2 2 .1 6 1 6 1 .5 0 .3 1 0 .8 5 4 0 .8 4 0 .4 3 8 0 .8 4 1 .7 5 4 C C 5 3 1 4 8 1 5 4 3 3 2 3 9 3 4 0 6 4 4 7 5 2 4 5 6 4 5 7 5 6 5 1 6 5 8 7 2 7 7 5 0 8 4 8 A A "i A " A ' A ' A ' A " A " A " A ' A " A " A ' A " A ' A " N o 1 * 2 * 3 * 4 * 5 * 6 * 7 * 8 * 9 * 1 0 * 1 1 1 2 1 3 1 4 1 5 ECJSE 2021 (1) 397-409 2-Thienylboronic Acid: A DFT Study For The Spectral,… 406 T a b le 7 . C o m p ar is o n o f th eo re ti ca l an d e x p er im en ta l F T -I R a n d F T -R A M A N s p ec tr a fo r th e co n fo rm er s o f T B A ( C o n t. ) T o ta l en er g y D is tr ib u ti o n 2 ,1 ʋ (C -τ ) (6 7 ), Δ 1 (R ) (1 9 ) γ( C -H ) (8 5 ), τ 1 R ( 1 4 ) ʋ (B -O ) (3 9 ), β (O -H ) (3 5 ), ʋ (C -τ ) (1 3 ) β (O -H ) (7 8 ), ʋ (B -O ) (1 9 ) β (O -H ) (3 4 ), ʋ (C -τ ) (2 1 ), ʋ (C -B ) (1 2 ) ʋ (C -C ) (5 6 ), β (C -H ) (2 9 ) β (C -H ) (6 6 ), ʋ (C -C ) (2 3 ) β (C -H ) (5 1 ), ʋ (C -C ) (2 9 ) ʋ (C -C ) (3 4 ), ʋ (B -O ) (1 4 ), β (C -H ) (2 1 ) ʋ (B -O ) (5 1 ), ʋ (C -C ) (1 1 ) ʋ (B -O ) (4 5 ), ʋ (C -C ) (1 6 ), β (C -H ) (1 3 ) ʋ (C -C ) (6 9 ), β (C -H ) (1 0 ) ʋ (C -C ) (4 8 ), Δ (R ) (3 4 ) ʋ (C -H ) (9 8 ) ʋ (C -H ) (9 9 ) ʋ (C -H ) (9 8 ) ʋ (O -H ) (1 0 0 ) ʋ (O -H ) (1 0 0 ) 1 R ec ei v ed f ro m R ef . 1 4 , 2 3 , 2 4 2 v al u es l es s th en 1 0 % o m it te d . 3 ʋ = s tr et ch in g ; δ = i n p la n e b en d in g ; γ = o u t o f p la n e b en d in g ; ρ = s ci ss o ri n g ; ω = w ag g in g ; τ= t o rs io n ; t , t w is ti n g ; r , r o ck in g . [ F re q u en cy (c m − 1 ), a= in s o li d p h as e b = a s d is so lv ed i n 1 ,4 -d io x an e E x p er im en ta l1 R a m a n 8 8 0 v s 9 5 6 m 1 0 7 6 m 1 1 6 1 m 1 3 2 7 m 1 4 2 3 m 3 0 0 8 w 3 0 8 6 m 3 1 6 3 m F T -I R 8 5 7 m 8 8 4 m 9 4 4 w 1 0 5 4 m 1 0 8 7 m 1 1 9 6 s 1 3 6 5 v s 1 4 2 5 v s 1 5 1 8 v s 3 2 1 9 v s D F T / B 3 L Y P 6 .3 1 G i T T 2 1 .5 1 1 .1 1 1 9 3 .5 7 8 .1 4 1 0 1 .8 7 .1 7 9 .4 9 8 .7 4 1 0 9 .2 1 6 7 .2 2 6 5 .6 1 1 4 .5 6 8 .0 5 5 .3 4 8 .3 1 2 .1 5 8 .7 7 5 0 .8 7 T T 8 6 5 9 2 9 9 4 9 9 8 3 1 0 5 2 1 0 9 4 1 1 2 3 1 2 4 9 1 3 5 9 1 4 0 5 1 4 2 0 1 4 8 6 1 5 8 8 3 2 1 9 3 2 3 3 3 2 6 5 3 7 8 7 3 7 9 2 i T C 1 4 .1 3 0 .5 2 2 .3 8 1 5 7 .7 1 6 5 .2 3 .7 7 2 1 .4 6 0 .3 2 1 7 2 .3 2 2 0 .8 2 3 7 .3 1 3 4 7 0 .6 9 1 9 .2 5 9 .0 2 1 .7 1 6 1 .6 8 2 8 .0 8 T C 8 6 6 9 1 7 9 7 9 1 0 3 4 1 0 5 4 1 0 9 3 1 1 2 1 1 2 5 9 1 3 6 1 1 4 0 0 1 4 4 3 1 4 8 4 1 5 8 9 3 1 9 1 3 2 2 9 3 2 6 6 3 7 7 3 3 8 0 9 i C T 4 .2 9 0 .7 6 6 9 .0 3 1 2 2 .9 9 7 .3 9 2 7 .4 1 .1 7 2 0 .0 9 2 1 5 .2 2 2 2 .8 2 4 9 .4 1 1 3 .7 5 7 .6 6 4 .7 3 4 .8 6 1 .1 3 5 9 .5 8 3 0 .5 5 C T 8 6 5 9 3 2 9 8 2 1 0 3 0 1 0 4 7 1 0 8 9 1 1 2 2 1 2 4 6 1 3 5 4 1 4 0 2 1 4 3 8 1 4 8 5 1 5 8 6 3 2 2 2 3 2 3 7 3 2 7 1 3 7 7 1 3 8 0 2 i C C 1 2 .4 8 0 .3 1 3 .1 7 2 4 9 .5 1 0 1 2 7 .9 3 9 .8 3 4 .4 2 4 2 0 .3 1 7 6 .6 1 8 4 .3 7 6 .9 4 4 1 .4 5 1 6 .1 5 6 .9 6 0 .9 8 3 6 .7 8 2 5 .4 4 C C 8 6 3 9 2 0 9 7 8 1 0 1 7 1 0 5 7 1 0 9 2 1 1 2 1 1 2 5 8 1 3 4 5 1 3 8 9 1 4 5 6 1 4 8 2 1 5 8 6 3 1 9 8 3 2 3 1 3 2 7 2 3 8 1 8 3 8 2 4 A A ’ A ” A ' A ' A ' A ' A ' A ' A ' A ' A ' A ' A ' A ' A ' A ' A ' A ' N o 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1 3 2 3 3 Kunduracıoğlu, A. ECJSE 2021 (1) 397-409 407 1. 3008, 3086 and 3163 cm -1 peaks assign the C-H stretching motions which belong to the thienyl ring part. 2. There are two kinds of CC bonds in the ring; -C-C- and –C=C- of which stretchings are seen as 1518 and 1423cm -1 peaks. 3. As a resulting word, the calculations and experiments can be supposed to be an agreement in 500 to 1600 cm -1 but the deviations between results rise in peaks of 3000+ cm -1 . Figure 7. Calculated and experimental* FT-IR spectra of the compound TBA (*=from ref. 12) 4. Conclusions The molecular structure and HOMO-LUMO analysis have been carried out by using the SPARTAN-14 suite via DFT theory in the B3LYP level and 6.31 G* basis set. Also, FT-IR and FT- RAMAN spectra were calculated and compared to experimental results as well. ECJSE 2021 (1) 397-409 2-Thienylboronic Acid: A DFT Study For The Spectral,… 408 The compound had been studied by different research groups from different aspects but in this study, the calculations were handled from a new point of view, isomeric transformations were examined for the first time as well. The experimental values taken from the literature were compared to calculated ones and found to be very close with small deviations. It was seen that the calculations related to vibrational analysis moved away from the experimental results after 3000 cm -1 , but the values were very close in the range of 500-1600 cm -1 . Due to the lack of experimental crystallographic data in the literature, the calculated geometric values were compared with 2 different molecules structurally similar to TBA. As a result of all studies, the calculated and experimental values were found to be very close and in agreement. Acknowledgment The software SPARTAN-14 used in this study was bought with the financial support of Pamukkale University Scientific Research Support Unit (Project no: HZL-2014/5). Besides, the experimental FT-IR spectrum of the compound TBA was received from the Sigma Aldrich product page and was used with gratitude for their kindness. The supplementary data file contains some additional data such as NMR spectra FT-RAMAN spectra and some extra tables about the title molecule TBA. Available from the authors upon reasonable request, References [1]. Hall, D.G., Boronic acids: preparation and applications in organic synthesis and medicine, DOI:10.1002/3527606548, Wiley‐VCH Verlag GmbH & Co. KGaA, 2006. [2]. Kar, A., Pharmacognosy and Pharmacobiotechnology 2nd Ed., New Age International (P) Ltd. Publishers, New Delhi, 2007. [3]. 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Acta, Part A, 2012, 97, 892-908. https://www.sigmaaldrich.com/catalog/product/aldrich/436836?lang=en®ion=TR https://www.amazon.com/Robert-M.-Silverstein/e/B001H9Q3TA/ref=dp_byline_cont_book_1 https://www.amazon.com/s/ref=dp_byline_sr_book_2?ie=UTF8&text=Francis+X.+Webster&search-alias=books&field-author=Francis+X.+Webster&sort=relevancerank https://www.amazon.com/s/ref=dp_byline_sr_book_3?ie=UTF8&text=David+J.+Kiemle&search-alias=books&field-author=David+J.+Kiemle&sort=relevancerank