Molecular structure and vibrational spectra of quercetin and quercetin-5’-sulfonic acid

Accepted Manuscript Title: Molecular structure and vibrational spectra of quercetin and quercetin-5’-sulfonic acid Author: J. Hanuza P. Godlewska E. Kucharska M. Ptak M. Kopacz M. M˛aczka K. Hermanowicz L. Macalik PII: DOI: Reference:

S0924-2031(16)30332-0 http://dx.doi.org/doi:10.1016/j.vibspec.2016.11.007 VIBSPE 2658

To appear in:

VIBSPE

Received date: Revised date: Accepted date:

19-7-2016 18-11-2016 21-11-2016

Please cite this article as: J.Hanuza, P.Godlewska, E.Kucharska, M.Ptak, M.Kopacz, M.M˛aczka, K.Hermanowicz, L.Macalik, Molecular structure and vibrational spectra of quercetin and quercetin-5’-sulfonic acid, Vibrational Spectroscopy http://dx.doi.org/10.1016/j.vibspec.2016.11.007 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

1

Molecular

structure

and

vibrational

spectra

of

quercetin

and quercetin-5’-sulfonic acid J. Hanuzaa, P. Godlewskab,* , E. Kucharskab, M. Ptaka, M. Kopaczc, M. Mączkaa, K. Hermanowicza, L. Macalika a

Institute of Low Temperature and Structure Research, 2 Okólna str., 50-422 Wrocław,

Poland b

Department of Bioorganic Chemistry, Institute of Chemistry and Food Technology, Faculty

of Engineering and Economy, Wrocław University of Economics, Wrocław, Poland c

Department of Inorganic and Analytical Chemistry, Faculty of Chemistry, Rzeszów

University of Technology, Poland *

Corresponding author. Tel.: +48 71 3680299; fax: +48 71 3680292; E-mail address: [email protected] (P. Godlewska).

2 Highlights 

The IR and Raman spectra of studied compounds were recorded



The IR and Raman wavenumbers were calculated from the optimized geometry of molecule



IR, Raman and DFT methods confirm the existence of an intramolecular HBs



The vibrational characteristics of OH compounds were analyzed

Abstract Molecular structures of quercitin and quercitin sulfonic acid have been determined by DFT quantum chemical calculations. FT-IR and FT-Raman spectra have been measured in the solid state and discussed in terms of B3LYP/6-311G(2d,2p) approach. The role of the hydrogen bonds in stabilization of their structures has been analyzed. The IR spectra were measured in the temperature range 5 – 300 K and the observed effects were used in the discussion of the hydrogen bond behavior.

Keywords: Quercetin and quercetin-5’-sulfonic acid; FT-IR and FT-Raman studies; DFT calculations; Molecular structure; Hydrogen bonds

1. Introduction Quercetin is a member of a large family of polyphenolic compounds being a class of plant and fungus secondary metabolites. They are called flavonoids and they fulfil various functions in plants. They are the most important plant pigments for flower coloration giving yellow, red and blue pigmentation is attractive for pollinating animals. They are responsible for UV filtration in higher plants, symbiotic nitrogen fixation and floral pigmentation. They also play a role of chemical messengers, physiological regulators, and inhibitors. Quercetin compounds have been widely used in medicine, pharmacology and optics since the discovery of their antitumor properties and citotoxicity against cell cultures [1-4], the application in fluorimetric determination of nucleic acids [5] and an efficient contrast enhancer for magnetic resonance imaging [6]. Quercetin was used in these complexes as a ligand, because it and several other flavonoids exhibit biochemical and pharmaceutical

3 properties including anti-allergic, anti-viral, anti-bacterial, anti-mutagenic, anti-carcinogenic, anti-neoplastic, anti-thrombotic and anti-oxidant activities [7-14]. The crystal structure of quercetin dihydrate was reported by Rossi et al. [15] and Jin et al. [16]. It crystallizes in the space group P1 with two molecules in the unit cell. Having five hydroxyl and one carbonyl groups, quercetin participates in several intra- and inter-molecular hydrogen bonds (HB). Two crystalline water molecules participate in formation of hydrogen bond extended network of the crystal lattice. Two hydroxyl groups at C3 of the benzo-ring and at C5 of the pyrone ring are involved in the hydrogen bond with O4 oxygen atom of the carbonyl group at C4. This oxygen also participates in the intermolecular HB with the O5’H5’ group of a neighboring molecule forming the dimer Z=2 of the unit cell. IR and Raman studies were used for characterization of quercetin both in the solid state and in solutions. The earlier works were mainly focused on the hydroxyl and carbonyl group vibrations [17-27]. The semi-empirical calculations of the vibrational levels with the use of AM1 approach were performed for quercetin by Cornard et al. [28]. In this work the use of 0.85 scaling factor was needed to obtain fitting between the experimental Raman and theoretical wavenumbers. DFT quantum chemical calculations using the B3LYP functional and the 6-31+G* basis set were performed for flavone and its three hydroxy derivatives, including quercetin by Teslova et al. [29]. The calculated wavenumbers were compared to the experimental Raman spectra; 0.98 scaling factor was used to fit these values. Formation of inter- and intra-molecular HBs in these systems was not taken into account in these calculations. Quercetin-5’-sulphonic acid (QSA) was rarely used as an antioxidant, anticancer and metal ions complexing agent in relation to quercetin alone. It was proposed as a new reagent in spectrophotometric determination of lanthanides [30]. Some of its lanthanide complexes showed luminescence and were suggested as suitable in laser technology applications [31]. Due to its non-toxic properties and good solubility in water, this compound in the form of flavonoid-metal complexes was recognized as a prospective material for anticancer therapy [32]. Therefore, the knowledge of the vibrational levels of QSA and their relation to crystal and molecular structures is necessary to explain its spectroscopic properties. In the present work DFT quantum chemical calculations of QSA were performed and the obtained results were compared to those calculated for quercetin (Q) with the same basis set and functional. These results were used in discussion of the measured IR and Raman spectra of Q and QSA. The obtained here assignment of the vibrational bands have been used in discussion of the spectroscopic properties of QSA lanthanide complexes.

4

2. Experimental details Quercetin and quercetin-5’-sulfonic acid are commercially available. They were purchased from Sigma – Aldrich company.

2.1. Raman and IR measurements IR spectra in the 4000–30 cm-1 range were measured using a Nicolet iS50 FT-IR (Thermo Scientific) spectrometer equipped with an Automated Beamsplitter exchange system (iS50 ABX containing a DLaTGS KBr detector and a DLaTGS Solid Substrate detector for mid-IR and far-IR regions, respectively), a built-in all-reflective diamond ATR module (iS50 ATR), Thermo Scientific Polaris™ and a HeNe laser as the IR radiation source. The resolution was 2.0 cm-1. Raman spectra in the 4000–80 cm-1 range were measured in back scattering geometry with a FT Bruker 110/S spectrometer. The resolution was 2.0 cm-1. The YAG:Nd laser (excitation wavelength 1064 nm) was used as an excitation source. The spectra in aqueous and DMSO solutions were measured using a FT Bruker 110/S Raman spectrometer. Temperature dependence of FTIR spectra were also measured in the 4000–30 cm-1 range with the resolution of 2 cm-1 in the temperature range 4-298 K using a Janis ST100 Cryostat and BIORAD 575C spectrophotometer. The spectra were measured using pressed KBr pellet and Nujol mull techniques in the MIR region and Nujol suspension on the polyethylene plates in the FIR region.

2.2. Quantum chemical calculations Geometry optimization of the molecular structure of the studied compounds was performed for monomeric units with the use of the Gaussian 03 program package [33]. All calculations were performed using density functional three-parameters hybrid (B3LYP) methods [34-36] with the 6-311G(d,p) [37, 38] basis set starting from the X-ray geometry. The potential energy distribution (PED) of the normal modes among the respective internal coordinates was calculated for Q and QSA using the BALGA [39] program. The IR and Raman wavenumbers were calculated taking into account possible intramolecular hydrogen bonds formed in these molecules.

5 The vector displacements of the atoms from their equilibrium positions during vibrations and the pictures of these displacements were prepared using the ANIMOL program that also visualizes particular modes in an animated way [40]. The calculated in DFT approach and experimental values were compared using scaling factors to correct the evaluated wavenumbers for vibrational anharmonicity and deficiencies inherent to the used computational level. 0.96 scaling factor was used for the range 3500– 2500 cm-1 and 0.98 for the range 2499–30 cm-1 of the spectra. The mean square deviation between the experimental and calculated unscaled wavenumbers for Q and (QSA) was 13.6 (8.4) for the IR and 3.0 (3.2) cm-1 for the Raman spectra. The scaling of the calculated wavenumbers improved this result to 8.3 (3.4) for the IR and 1.8 (1.6) cm-1 for the Raman spectra. No imaginary wavenumbers were obtained in the calculated spectra. The theoretical Raman intensities were calculated using the RAINT computer program [41, 42].

3. Results and discussion 3.1. Vibrations of the Q molecule Fig. 1 shows the atomic numbering of Q and QSA used in the DFT calculations. The structural parameters of Q reported in [24, 25] were used as the input data in these calculations. According to the nomenclature used in ref. [29] the benzene ring in the chromone system is designed as Ring A, the phenyl ring as Ring B and the pyrone ring as Ring C. Figs. 2 and 3 present the experimental and calculated IR and Raman spectra of Q and QSA. The respective wavenumbers are listed in Tables 1 and 2 together with the proposed assignment of the bands derived from the DFT calculations. The reliability of the structural model used in these calculations was confirmed by the comparison of the experimental and geometrical parameters presented in Table S1. Table S2 contains the atomic Cartesian coordinate of optimized Q and QSA molecules. In Table 3 geometrical parameters of hydrogen-bonds were collected. Figures 1-3 and Tables 1-3 The skeleton of the studied Q and QSA derivatives contains two separate units, a double ring chromone system and phenyl ring. The vibrations of these units form a specific spectral patterns in the IR and Raman spectra and first they should be isolated from the other normal modes of the studied compound. The vibrational characteristics of the Q molecule will be discussed in details because this system occurs in several flavonoids.

6 In the discussion of the obtained results it should be taken into account that the DFT calculations were performed for isolated molecules not confined in the crystal lattice. A, B and C rings of the phenolic system of the molecules appear in the solid state in the quasi planar conformation. This could not be true for water and other polar solvents where the intermolecular interactions may be as strong as intramolecular HB acting in these molecules. Therefore, the potential energy curves as a function of the torsion angles around the C2-C1’ bond of the Q and QSA molecules were determined. Fig. 4 shows these dependences for both studied compounds. The course of these relationships indicates that the most stable configurations of these molecules appear when the torsion angle is 0 0 and 1800, i.e. when three rings of the molecule lie in the same plane. The former case appears for these compounds in the solid state where short contacts C2’- HO1 and C6’-H-O(C3) appear. To explain how it is realized when the studied molecules are dissolved in polar media Raman spectra in a few solutions were measured (see Fig. 5). Figures 4 and 5

3.1.1. Vibrations of the chromone unit in the Q molecule The vibrations of the A and C rings in the chromone system are strongly coupled. They usually are simultaneously involved in the vibrations forming the common normal modes. Because 11 bonds form this system, eleven stretching normal modes should be active in the spectra. In fact, such a number of respective stretching vibrations were calculated in the range 1270 – 1660 cm-1. For the Q molecule the DFT calculation locates the respective bands at the following wavenumbers 11 = 1659, 12 = 1635, 14 = 1603, 16 = 1570, 18 = 1511, 19 = 1489, 21 = 1432, 22 = 1405, 23 = 1384, 26 = 1329 and 29 = 1279 cm-1. These vibrations involve the atoms of only one ring C (12) or A (18), but the others have a sum nature of the (A) + (C) type. Some of these normal modes contain a contribution of the vibrations corresponding to the OH groups at C3, C5 and C7 carbons and C=O group at C4 carbon atom. The same rules apply to the in-plane  and out-of-plane  bending vibrations of the chromone system. They were calculated in the ranges 1250-990 and 930-400 cm-1, respectively. The DFT calculations locate the bending (A) or/and (C) vibrations at the following wavenumbers: 31 = 1242, 32 = 1193, 37 = 1118, 39 = 1088, 40 = 1011 and 41 = 993 and those of the bending  vibrations at: 45 = 837, 47 = 816, 51 = 772, 53 = 708, 54 = 701, 55 = 680, 57 = 638, 58 = 634, 60 = 611, 62 = 580, 65 = 519, 67 = 453 and 70 = 397 cm-1.

7 The vibrations of the C-H bonds at C6 and C8 carbon atoms of the chromone system appear in the ranges characteristic for aromatic compounds. The DFT calculations locate the stretching (CH)A8 and (CH)A6 vibrations at 7 = 3096 and 9 = 3057 cm-1. The in-plane bending (CH)A6 and (CH)A8 vibrations of this group were predicted at 34 = 1180 and 36 = 1156 cm-1, respectively, but several other vibrations of the chromone skeleton exhibit small contribution of the C-H bond modes. Finally, the wavenumbers of the out-of-plane bending (CH)A6,8 and (CH)A8,6 vibrations were calculated at 47 = 816 and 49 = 802 cm-1. The calculated wavenumbers fit well to those observed in the IR and Raman spectra. Because some vibrations of the chromone skeleton fall into the region of the phenyl ring vibrations the observed bands are broadened and have a complex shape.

3.1.2. Phenyl ring vibrations The phenyl ring vibrations are very characteristic and they are usually observed at defined wavenumbers. Six stretching (B) modes were calculated at the following wavenumbers: 13 = 1615, 15 = 1601, 17 = 1534, 20 = 1448, 24 = 1357 and 27 = 1326 cm1

. The in-plane bending (B) vibrations were calculated at 33 = 1182, 35 = 1179, 37 = 1118

and 38 = 1108 cm-1. At last, the out-of-plane (B) vibrations have the greatest contribution to the phonons calculated at 42 = 938, 45 = 837, 52 = 715, 61 = 602, 63 = 567, 64 = 546, 66 = 481 and 68 = 452 cm-1. It should be noted that the breathing (B) vibrations of the phenyl ring in the studied quercetin is observed at 784 cm-1 in the IR spectrum and 790 cm-1 in the Raman one. These vibrations usually appear for benzene derivatives in the region 1000 – 800 cm-1 [43, 44]. The ring (CH)B5’, (CH)B2’ and (CH)B6’ vibrations were calculated at 3128, 3067 and 3032 cm-1 and they were observed in the range 3000–3090 cm-1. The other characteristic vibrations of the phenyl C-H bond contributes to the following normal modes: 

in-plane bending vibrations: (CH)B2’ contributes to 17 = 1534, 24 = 1357, 28 = 1296 cm-1 and (CH)B2’,5’,6’ contributes to 29 = 1279 and 35 = 1179 cm-1. These modes are observed at 1544-1550, 1362, 1295, 1287 and 1174 cm-1;



out-of-plane bending vibrations: (CH)B5’,6’ contributes to 43 = 927, 48, 49 = 802 cm-1 and (CH)B2’ contributes to 44 = 851 cm-1 mode. These bands are observed at 930, 883 and 805 cm-1.

These vibrations arise as strongly coupled the phenyl ring and CH modes. They are observed in ranges typical for these vibrations.

8 Very complex vibrations of the whole skeleton are observed in the range below 300 cm-1. They form concerted movements in which almost all fragments of the molecule take part together with the hydrogen bonds.

3.1.3. Vibrations of the OH groups The existence of several types of intramolecular interactions in quercetin in the solid state was postulated [45-48]. Apart from the short contacts between C6’-H and oxygen of C3OH bond as well as C2’-H bond and O1 oxygen, intramolecular interactions in which hydroxyl groups at C3 and C5 and C4=O carbonyl group are involved were considered [45, 46]. Generally, the Q molecule contains five OH groups, two of them substitute the A ring, other two the B ring and one – the C ring. Their vibrations should differ because the hydroxyl groups at C5 position of the A ring and C3 position of the C ring participate in intra-molecular interactions with the C=O carbonyl group [45, 46]. Besides, the hydroxyl group at C7 position of the A ring and both hydroxyl groups of the B ring can form intermolecular HBs. A different nature of the hydroxyl groups is confirmed by the results of DFT calculations. It should be noted that a peculiar ability to chelate metal ions is exhibited mainly by the hydroxyl group at C3 and C4=O carbonyl group [49, 50]. It means that these HB-s can be replaced by stronger interactions in the solid state. The problem of intramolecular interactions in the QSA is discussed in part 3.2.5. The stretching vibrations of the OH groups at B3’, A7 and B4’ positions were located in the DFT calculations at 3681, 3676 and 3676 cm-1 but in the range 3700–3450 cm-1 of the IR and Raman spectra no band was observed. Instead, a broad IR contour corresponding to the HB interactions was observed in the range 3500–2000 cm-1. It means that these OH groups are engaged in the intermolecular hydrogen bonds with adjacent Q molecules or water molecules present in Q-dihydro compound. The theoretical calculations predict that the vibrations of OH groups in C3 and A5 positions should be located at 3444 and 3211 cm -1 which confirms that these groups interact with the C=O group and the latter HB is stronger than the former. This agrees with the conclusions reported in Refs. [45] and [46]. The bending vibrations of five hydroxyl groups of Q molecule contribute to several normal modes observed in the broad range 1520–1150 cm-1. These vibrations influence the following bands (the greatest contribution is bolded): 

(OH)A5: 11 (1659), 18 (1511), 19 (1489), 22 (1405);



(OH)C3: 12 (1635), 23 (1384), 25 (1341);

9 

(OH)A7: 30 (1249), 31 (1242), 36 (1156);



(OH)B3’: 20 (1448), 24 (1357), 33 (1182), 35 (1179);



(OH)B4’: 27 (1326), 33 (1182), 35 (1179).

Taking into account the greatest contributions of the OH internal coordinates to the normal modes, the following observed wavenumbers could be assigned to the respective bands: (OH)A5: 1514 – 1510 cm-1, (OH)C3: 1371 – 1345 cm-1, (OH)B3’: 1362 and 1185 cm-1, (OH)B4’: 1185 – 1174 cm-1 and (OH)A7: 1159 – 1157 cm-1. Such a contribution of the OH group vibrations to the normal modes and the sequence of the respective bands testify that the intra-molecular O-HA5O bond is stronger than that of the O-HC3O one. The other OH groups participate in weaker intermolecular bonds whose strength forms the sequence: O-HB3’O  O-HB4’O  O-HA7O, i.e. the latter is the weakest. A similar analysis could be performed for the out-of plane bending (OH) vibrations. They contribute to the following normal modes observed in the range 830–330 cm-1: 

(OH)A5: 46 (823), 59 (617), 60 (611);



(OH)C3: 56 (662), 59 (617), 60 (611), 64 (546), 69 (406);



(OH)A7: 53 (708), 71 (389);



(OH)B3’ and (OH)B4’: 68 (452), 73 (365), 74 (339).

All the above statements derived for the (OH) vibrations are true for the out-of-plane modes. The experimental wavenumbers of these vibrations correspond to the following bands: (OH)A5: 824 cm-1, (OH)C3: 599 and 405 – 404 cm-1 and finally (OH)B3’ and (OH)B4’: 341– 352 cm-1. The vibrational characteristics of the OH group modes should be completed by the vibrations in which C-O bond is stretched, i.e. (C-O) modes and in which the whole rigid CO-H unit rotates in the plane formed by these bonds, i.e. (COH) vibrations. The former vibrations are observed in the range 1550–780 cm-1. They usually partly contribute to the vibrations of the chromone and phenyl rings and are coupled with OH vibrations. Their participation does not exceed 20 % of the whole normal vibration. The latter vibrations, (COH), are observed in the ranges 707–705, 594–567 and 400–330 cm-1.

3.1.4. Vibrations involving C=O bond vibrations

10 Because the carbonyl group at C4 position of the C ring interacts simultaneously with OH groups at C3 and C5 positions of the chromone system, the bands corresponding to its vibrations should shift towards long wavelength region. The stretching (C=O) vibrations contribute to the 13, 14 and 16 modes calculated at 1615, 1603 and 1570 cm-1. The respective bands are observed at 1613, 1601 and 1586 cm-1. However, their contribution to the former two modes is very small and does not exceed 20 %. The greatest contribution of C=O bond internal coordinates appears for the 16 mode and therefore the band at 1586 cm-1 should be considered as (C=O) vibration. The bands corresponding to the in-plane (C=O) and out-of-plane (C=O) vibrations are observed in the ranges 931–372 cm-1 and 780–660 cm-1, respectively. The former contribute to the 42, 58 and 72 modes calculated at 938, 634 and 375 cm-1 and observed at 931, 635 and 372 (379) cm-1 The latter vibrations take part in the 51 (772), 54 (701) and 56 (662 cm-1) modes. Because the greatest contribution of 41 % order appears for the 51 mode, the band observed at 771 cm-1 should be assigned to the (C=O) vibration.

3.1.5. Vibration of the C-C bond between the B and C rings CB–CC bond between the chromone system and phenyl ring participates in three types of vibrations. It influences the stretching 25 mode calculated at 1341 and observed at 1345 cm-1. Bending (C-C) vibrations contribute to the 81, 82 and 87 modes calculated at 233, 225 and 85 cm-1 and observed in the range 231–217 and at 118 cm-1. At last, the out-of-plane (C-C) vibrations take part in the concerted motions observed in the range 104–99 cm-1.

3.2. Vibrations of the QSA derivative QSA like Q contains double chromone-phenyl system. It is expected that its vibrational characteristics should be quite similar. However, due to substitution of the SO 3H chromophore at C5’ carbon atom of the B ring, some changes in wavenumbers and PED contribution in the normal modes of this ring are observed. Table 2 lists the experimental IR and Raman wavenumbers, the theoretical values and PED data obtained from the DFT calculations. The differences between the Q and QSA vibrations is shortly discussed below.

3.2.1. Vibrations of the chromone system Comparing the vibrational data of the chromone system in Q and QSA molecules two effects can be seen. The wavenumbers of the respective bands show an insignificant shift

11 caused by a small change of the PED contributions to these normal modes. The changes in the wavenumbers do not exceed a few cm-1 which means that the change of substitution in ring B does not cause essential changes in the vibrations of the chromone system.

3.2.2. Phenyl ring vibrations Phenyl ring vibrations in Q molecule can be divided into two groups. In the first type the carbon atoms of the skeleton are engaged and therefore the bands corresponding to these modes do not change their wavenumber and PED contribution. Examples of such a behavior are the bands observed at 1612 cm-1 (Q  QSA 1615  1613), 1461 cm-1 (1448  1453), and 1118 cm-1 (1118  1108). The modes resulting from the coupling of the ring vibrations and its OH and SO3H substituents belong to the second type that exhibit a significant shift of their corresponding bands. A particularly expressive example of such a behavior is 7 mode calculated for QSA at 3132 and for Q at 3032 cm-1 which correspond to the (CH)B6’ vibration, i.e. to the stretching motion of the C-H bond adjacent to the sulfonic group. On the other hand, the (CH)B2’ vibration practically does not change its wavenumber (Q 3067  QSA 3071 cm-1). Similar effects are analyzed below where the vibrations of particular chromophores are discussed. The substitution of the sulfonic group influences the out-of-plane vibrations of the Q molecule which for QSA shift (CH)B2’ (47 851  869 cm-1) and (B) (54 715  731 cm-1) vibrations to the higher energy and those of (CH)B6’ to the lower energy (45 (927  902 cm-1). 3.2.3. Vibrations of the (OH)B3’ and (OH)B4’ hydroxyls: Q  QSA band shift Introduction of the sulfonic group in the 5’ position of the phenyl ring causes substantial changes in vibrational dynamics of the OH group at 4’ position (3676  3425 cm-1) but the wavenumber of the (OH)B3’ vibration is not changed. Inspection of the other data from Table 3 allows to draw the following conclusions: 

The contribution of the (OH)B4’ or (C-O)B4’ vibration in the normal mode in which the (B) vibration dominates causes a decrease of the respective wavenumber, i.e. 15 (1601  1592 cm-1), 18 (1534  1505 cm-1), 48 (837  830 cm-1);



The vibrations with the great contribution of the (B) coordinate with strong participation of other phenyl ring substituents and chromone vibrations increase their

12 wavenumber. This effect is seen for the 23 (1357  1400 cm-1), 33 (1182  1220 cm-1), 42 (1011  1030 cm-1), 64 (602  613 cm-1), 71 (481  509 cm-1); 

The theoretical wavenumber of the (OH)B4’ vibration significantly decreases to the 687 cm-1 (58 mode).



All the statements on the formation of the intermolecular HB-s in Q derivative are true for QSA.

3.2.4. C=O group vibrations in QSA The bands observed at 1612 (RS), 1597 (IR), 1599 (RS), 1558 (IR), and 1547 (RS) cm-1 correspond to the modes that exhibit some contribution of the (C=O) vibration. The greatest contribution is postulated for IR bands at 1597 (19%) and 1558 (22%) cm-1. This suggests that the (C=O) band observed for Q at 1586 cm-1 splits into a doublet at 1558 and 1597 cm-1 for QSA as a result of the sulfonic group substitution. The (C=O) vibration participates in the mode calculated for QSA at 949 and 376 cm-1 and observed at 935 (IR) and 938 (RS) cm-1 and 377 (IR) cm-1. The respective out-of-plane (C=O) vibration shows the greatest contribution to the mode calculated at 773 cm-1 and observed at 771 cm-1. It should be noted that this group is involved in the hydrogen bond with the (OH)A5 and (OH)C3. 3.2.5. CB – CC vibration in QSA We assigned the (C-C) vibration to the strong Raman band at 1314 cm-1 because it was predicted by DFT calculations as intense IR and Raman bands at 1342 cm-1. The occurrence of the bending (C-C) and (C-C) vibrations is predicted by the DFT calculations in the range 300 – 10 cm-1. They contribute to several normal modes from this range and on this basis we assigned these vibrations to the bands observed at 289 (IR), 291 (RS), 132 (IR), 130 (RS) as well as at 83 cm-1 (contribution of 81 %). The molecular structure of the studied compounds suggests a possibility of rotation around the C1’-C2 bond. To verify this hypothesis we dissolved the QSA in aqueous and DMSO solutions and measured their Raman spectra. Fig 5 compares these spectra with those recorded in the solid state. Strong differences between them proves that the conformation of QSA molecule is changed in the polar solutions where the intra-molecular interactions are replaced by the inter-molecular HB-s in which the solvent molecules are involved.

13 3.2.6. Vibrations of the sulfonic group Introduction of the sulfonic chromophore in the 5’ position of the phenyl ring of Q causes clear changes in the IR and Raman spectra of QSA. The vibrations of this group contributes to several normal modes with their different PED participation. DFT calculations performed for the isolated QSA molecule locate the (OH)SO3H vibration at 3634 cm-1 (3, Table 3). However, neither IR nor Raman spectra show bands in the range 3700–3450 cm-1. It means that the sulfonic group interacts with an adjacent molecule trough the O-HO hydrogen bond. This suggestion is confirmed by participation of the (OH)SO3H vibration in several other modes of this group. Contribution of c.a. 30–40 % is predicted by DFT calculations for the modes from the range 1350–1300 cm-1 (Table 2). However, the greatest participation of the 70–80 % order appears for the bands observed at 1127 and 1134 cm-1 and 1095 and 1093 cm-1 corresponding to the coupled (S=O) + (OH)SO3H vibrations. According to the DFT calculations the band observed at 884 cm-1 should be assigned to the (C-S) vibration and at about 780 cm-1 to the (S-OH) vibration. Smaller contributions of the S=O vibrations occur for the bands at 626, 543-550, 464, 446, 367, 348/347 as well as 324/335 and 305/306 cm-1. The out-of-plane ((OH)SO3H vibration should be assigned to the bands predicted in the range 120–20 cm-1.

4. Low-temperature IR spectra The effect of low temperature on the properties of QSA was studied in the temperature range 5–280 K. It is well known that decreasing temperature causes an increase of band wavenumbers and an increase in band intensity. These changes are particularly visible for the vibrations of OH groups participating in hydrogen bonds. Additionally, the contours of these bands become significantly narrower. Such effects are observed in the low-temperature spectra of QSA. They are shown in Fig. 6 A–E which present the IR spectra in the wavenumber ranges: 3650–2500 (A), 1750–1000 (B), 1000–500 (C), 450–280 (D), 280–180 (E), and 180–90 (F) cm-1. Figure 6 A–F The broad contour observed at room temperature in the range 3650–2500 cm-1 splits at 5 K into three components appearing at 3099, 3119, and 3197 cm-1, corresponding to the (CH) vibrations, six bands corresponding to the (OH) and (H2O) vibrations. The former bands show a distinct (280 K  5 K) shift and should be assigned to the following modes:

14 3575  3580 cm-1 (OH)B3’, 3515  3510 cm-1 (OH)A7, 3425  3455 cm-1 (OH)C3 + 3415 cm-1 (OH)B4’, 3250  3260 cm-1 (OH)A5, 2600  2605 cm-1 (OH)SO3H. The shifts of the bands in the range 1750-1000 cm-1 are insignificant and do not exceed a few cm-1. Comparing these data with the results of the DFT calculations, the respective bands could be assigned to the following vibrations: 1637 and 1384 cm-1 (OH)C3, 1597 and 1400 cm-1 (OH)B4’, 1480 and 1505 cm-1 (OH)A5, 1176 cm-1 (OH)A7 and 1137 cm-1 (OH)SO3H. Significant changes of the band contours observed in the 1000-500 cm-1 range appear at 664, 604, and 543 cm-1. These vibrations probably correspond to the (OH)C3. Other out-of-plane vibrations of the OH group are observed in the range 450–250 cm-1. The clear change of the spectral contour and shape is observed at low temperature for the bands at 404 cm-1 (OH)C3, 395 cm-1 (OH)A7, 377 cm-1 (OH)C3, 348 cm-1 (OH)B3’, 324 cm-1 (OH)A7 and 318 cm-1 (OH)B3’. The greatest changes of the IR spectra are observed for QSA in the 280-100 cm-1 range. The shift of some of these bands exceeds 10 cm-1. The following changes in band positions appear when the temperature is lowered to 5 K: 268273, 257261, 202215, 195205, 171175, 162168, 150157, 132137, 123 129 and 104117 cm-1. These bands are very weak or they are not observed at room temperature. All these bands should be assigned to the OHO vibrations, however, their assignment to the respective OH group is not possible without the knowledge of the structural parameters taken from the XRD studies. Generalizing the results of the low-temperature studies it should be noted that the most stable structural system appears for the groups (OH) A5C=O(OH)C3. All the statements presented above concerning the participation of other groups in the HB-s have been confirmed by the studies of IR spectra at low temperature. They also confirm the assignment of the bands proposed in Table 2 and based on the DFT calculations.

5. Conclusion The vibrational characteristics of quercetin and quercetin 5’-sulfonic acid have been studied by means of FT IR and Raman spectra and DFT quantum chemical calculations. Their molecular structures have been compared and the influence of the sulfonic group substitution on the spectra and structure has been analyzed. The formation of the intramolecular hydrogen bonds between the C=O and OH groups at C3 and A5 carbon atoms of the chromone system has been confirmed. The consequences of the inter-molecular hydrogen bonds formation between the OH groups at A7, B3’ and SO3H groups have been considered. The obtained

15 results will be used in interpretation of the structure and spectroscopic properties of lanthanide complexes with QSA ligand.

Acknowledgement The present work was supported by Polish National Centre of Science under the grant No. 2014/15/B/ST5/04730.

References [1] H. Elo, Inorg. Chim. Acta 136 (1987) 149-153. [2] A.T. Beverly, T.A. Michael, W.R. Kristina, Cancer Res. 50 (1990) 6971-6975. [3] J. Zhou, L-f. Wang, J-y. Wang, N. Tang, J. Inorg. Biochem. 83 (2001) 41-48. [4] D. Malešev, V. Kuntić, J. Serb. Chem. Soc. 72 (2007) 921-939. [5] J. Zhou, G-Q Gong, Y-N Zhang, J-Q Qu, L-F Wang, J-W Xu, Anal. Chim. Acta 381 (1999) 17-22. [6] T. Muthurajan, P. Rammanohar, N.P. Rajendran, S. Sethuraman, U.M. Krishnan, Roy. Soc. Chem. Advances 5 (2015) 86967-86979. [7] P.C. Hollman, J.H. de Fries, S.D. van Leeuven, M.J. Mengelers, M.B. Katan, Am. J. Clin. Nutr. 62 (1995) 1276-1282. [8] P.C. Hollman, M.V.D. Gaag, M.J.B. Mengelers, J.M.P. van Trijp, J.H.M. de Fries, M.B. Katan, Free Radical Biol. Med. 21 (1996) 703-707. [9] D.R. Ferry, A. Smith, Y. Malkhandi, D.W. Fyle, P.G. de Takats, D. Anderson, J. Broker, D.J.Kon, Clin. Cancer Res. 2 (1996) 659-668. [10]

N. Kawada, S. Seki, M. Inoue, T. Kuroki, Hepatology 27 (1998) 1265-1274.

[11]

M. Yoshida, T. Sakai, N. Hosokawa, N. Marui, K. Matsumoto, A. Fujioka, H.

Nishino, A. Aoike, FEBS Lett. 260 (1990) 10-13. [12]

L. H. Long, M. V. Clement, B. Halliwel, Biochem. Biophys. Res. Commun. 273

(2000) 50-53. [13]

S. Birjees Bukhari, S. Memon, M. Mahroof Tair, M. I. Bhanger, J. Mol. Struct. 892

(2008) 39-46. [14]

W. Chen, S. Sun, W. Cao, Y. Liang, J. Song, J. Mol. Struct. 918 (2009) 194-197.

16 [15]

H.L. Hergert, E.F. Kurth, J. Am. Chem. Soc. 75 (1953) 1622-1625.

[16]

B.L. Shaw, T.H. Simpson, J. Chem. Soc. (1955) 655-658.

[17]

J.H. Looker, W.W. Hanneman, J. Org. Chem. 27 (1962) 381-389.

[18]

L. Briggs, L. Colebrook, Spectrochim. Acta 18 (1962) 939-957.

[19]

H.J. Looker, S.A. Kagal, J.I. Dappen, J.R. Edman, J. Hetero-Cycl. Chem. 3 (1966)

61-66. [20]

J.H. Looker, W.W. Hanneman, S.A. Kagal, J.I. Dappen, J.R. Edman, J. Hetero-Cycl.

Chem. 3 (1966) 55-60. [21]

C.I. Jose, P.S. Phadke, A.V. Raman Rao, Spectrochim. Acta A 30 (1974) 1199-1206.

[22]

Z. Dinya, J.B. Schag, A. Levai, Acta. Chim. Acad. Hung. 99 (1979) 453-459.

[23]

T.P. Dzugan, J. Schmidt, T J. Aartsma, Chem. Phys. Lett. 127 (1986) 336-342.

[24]

M. Rossi, L.F. Rickles, W.A. Halpin, Bioorg. Chem. 14 (1986) 55-69.

[25]

G.Z. Jin, Y. Yamagata, K.I. Tomita, Acta Cryst. C46 (1990) 310-313.

[26]

F. Martinez, T. Adzed, J. Iglesisas, Microchim. Acta 1 (1991) 105-114.

[27]

A. Torreggiani, A. Trinchero, M. Tamba, P. Taddei, J. Raman Spectrosc. 36 (2005)

380-388. [28]

J. P. Cornard, J. C. Merlin, A. C. Boudet, L. Vrielynck, Biospectroscopy 3 (1997)

183-193. [29]

T. Teslova, C. Corredor, R. Livingstone, T. Spataru, R.L. Birke, J.R. Lombardi, M.V.

Caňamares, M. Leona, J. Raman Spectrosc. 38 (2007) 802-818. [30]

M. Kopacz, B. Bujonek, D. Nowak, S. Kopacz, Chem. Anal (Warsaw) 46 (2001) 621-

631. [31]

M. Kopacz, A. Bartecki, Koord. Khim. 4 (1978) 1845; 5 (1979) 367.

[32]

M. Kopacz, D. Nowak, M.H. Umbreit, J. Kłos, Polish J. Chem. 77 (2003) 1787-1796.

[33]

M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,

J.A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P.

17 Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople, Gaussian 03, Revision A.1, Gaussian, Inc., Pittsburgh PA, 2003. [34]

D. Becke, J. Chem. Phys. 104 (1996) 1040-1046.

[35]

C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785-789.

[36]

R. G. Parr, W. Yang, Density-functional Theory of Atoms and Molecules, Oxford

University Press, New York, 1989. [37]

A.D. McLean, G.S. Chandler, J. Chem. Phys. 72 (1980) 5639-5648.

[38]

R. Krishnan, J.S. Binkley, R. Seeger, J.A. Pople, J. Chem. Phys. 72 (1980) 650-654.

[39]

M.J. Nowak, L. Lapinski, BALGA computer program for PED calculations (H.

Rostkowska, L. Lapinski, M. J. Nowak; Vib. Spectrosc. 49 (2009) 43-51. [40]

M.M. Szcześniak, D. Maślanka, AniMol - computer program, Infrared and Raman

Spectroscopy Teaching and Research Tool, Version 3.21 (1995–1997). [41]

D. Michalska, RAINT (Raman Intensities) - a computer program for calculation of

Raman intensities from the Gaussian outputs, Wrocław University of Technology, Wrocław, 2002. [42]

D. Michalska, R. Wysokiński, Chem. Phys. Lett. 403 (2005) 211-217.

[43]

G. Socrates, Infrared and Raman Characteristic Group Frequencies, 3rd ed., J. Wiley

and Sons. Ltd., 2001, and references therein. [44]

D. Lin-vien, N.B. Cothup, W.G. Fateley, J.G. Grasselli, The Handbook of Infrared and

Raman Characteristic Frequencies of Organic Molecules, Academic Press, Boston, 1991. [45]

L.H. Briggs, L.D. Colebrook, Spectrochim. Acta 18 (1962) 939-957.

[46]

M. Heneczkowski, M. Kopacz, D. Nowak, A. Kuźniar, Acta Poloniae Pharmaeutica

58 (2001) 415-420. [47]

I. Wawer, A. Zielińska, Solid State Nucl. Magn. Resonance 10 (1997) 33-38.

[48]

P. Trouillas, P. Marsal, D. Siri, R. Lazzaroni, J-L. Duroux, Food. Chem. 97 (2006)

679-688. [49]

G-R. Xu, M. Y. In, Y. Yuan, J-J. Lee, S. Kim, Bull. Korean Chem. Soc. 28 (2007)

889-892. [50]

M. Symonowicz, M. Kolanek, Biotechnol. Food Sci. 76 (2012) 35-41.

18 Figure captions

Fig. 1. The atomic numbering of Q (A) and QSA (B).

19 Fig. 2. The IR (A) and Raman (B) spectra of Q in the range 3700–80 cm-1.

20 Fig. 3. The IR (A) and Raman (B) spectra of QSA in the range 3700–80 cm-1.

21 Fig. 4. The potential energy curve of Q (A) and QSA (B) as a function of the torsion angle defined around C2-C1’ bond.

22 Fig. 5. Comparison of the Raman spectra measured for the QSA in the solid state and dissolved in aqueous and DMSO solutions.

23 Fig. 6. Temperature dependence of the IR spectra of QSA in the ranges: 3650–2500 (A), 1750–1000 (B), 1000–500 (C), 450–280 (D), 280–180 (E), and 180–90 (F) cm-1.

24 Table 1. Experimental and calculated wavenumbers (cm-1) with PEDs and assignments of quercetin. No Calc. 1 2 3 4 5 6 7 8 9 10 11

3681 3676 3676 3444 3211 3128 3096 3067 3057 3032 1659

Int [%] IR RS 10 1 3 2 45 1 30 1 74 1 1 0 0 1 2 0 1 2 5 2 83 17

Exp.

12

1635

14

13

1615

18 100 1618 sh

14

1603

69

9

1601 s

38 A) + 14 C) + 16 C=O)

15

1601

43

1

1590 sh

56 B) + 9 (OH)B4’

16

1570

33

36

IR 3443 sh 3412 sh 3359 sh 3283 sh 3223 m

PED RS

3236 w

3095 sh 3090 w 3079 sh 3064 vw

1664 m

1655 m

99 OH)B3’ 79 OH)A7 + 21 OH)B4’ 78 OH)B4’ + 21 OH)A5 99 OH)C3 99 OH)A5 99 CH)B5’ 100 CH)A8 100 CH)2’ 100 CH)A6 99 CH)B6’ 50 A) + 17 C) + 23 (OH)A5 37 C) + 19 B) + 16 (OH)C3

19

1613 vs 56 B) + 10 (CH)B5’ + 7 C=O)

1586 s

38 A) + 17 C) + 31 C=O)

1578 sh 17

1534

21

7

1550 w

1544 s

41 (CH)B2’ + 37 B) + 11 C-O)B4’

1527 sh 18

1511

72

8

1518 sh

1514 m 25 A) + 24 (OH)A5 + 19 (CH)A8 + 11 C-O)A7

1510 s 1468 m 34 C) + 19 A) + 21 (OH)A5

19

1489

44

6

20

1448

0

6

1456 m

1458 m 32 B) + 20 (OH)B3’ + 10 (CH)B2’

21

1432

19

18

1428 m

1433 s

15 A) + 15 C) + 16 B) + 19 C-O)A5

22

1405

37

18

1400 s

26 A) + 23 C) + 17 (OH)A5 + 12 C-O)C3

23

1384

32

1

1371 sh 23 (OH)C3 + 20 C) + 18 A) + 12 C-O)A5 + 11 C-O)A7

24

1357

12

6

1362 s

25

1341 100 71

26

1329

15

9

27

1326

9

6

1309 s

32 B) + 23 (OH)B4’

28

1296

14

2

1295 s

35 C-O)B3’ + 23 B) + 20 (CH)B2’

29

1279

67

0

1345 s

39 (OH)B3’ + 29 B) + 28 (CH)B2’ 23 (OH)C3 + 21 B-C) + 11 C-O)B3’ + 9 (B) + 8 (C)

1328 vs 43 A) + 11 C) + 11 (CH)A6 + 10 C-O)A5

1287 m 20 C-O)B3’,4’ + 20 (CH)B2’,5’,6’ + 13 A) + 10 C) + 8 (OH)A7 + 7 (OH)C3 + 7 (OH)A5

25 30

1249

7

1243 w 17 (CH)A6,8 + 15 (OH)A7 + 15 C-O)B3’,4’ + 12 A) + 11 C-

1 1238 m

O)C3 1215 w 26 C) + 12 A) + 21 (OH)A7 + 12 (CH)A6,8 + 11 C-O)A5

31

1242

13

1

1207 vs

32

1193

43

5

1198 s

33

1182

67

6

34

1180

21

7

35

1179

40

2

36

1156

80

2

1159 vs

1157 m 32 (CH)A8 + 30 (OH)A7 + 17 A)

37

1118

20

0

1139 vs

1136 w 29 C) + 27 B) + 17 (CH)A8 + 8 C-O)A5

38

1108

4

4

1103 sh

1105 m 33 (B) + 17 C-O)B3’,4’ + 14 (CH)B6’,2’,5’ + 13 C)

39

1088

6

2

1092 vs

40 C) + 15 C-O)C3 + 15 (CH)A6,8 1185 sh 41 (OH)B3’,4’ + 21 B) + 17 (CH)B2’,5’,6’ + 17 (CH)A6 44 (CH)A6 + 18 C-O)A7 + 8 (OH)B3’ 1174 sh 34 (OH)B4’,3’ + 32 (CH)B2’,5’,6’ + 27 B)

49 C) + 25 A)

1046 sh 1000 m 39 A) + 16 C) + 13 B) + 11 (CH)A6,8

40

1011

10

1

1010 m

41

993

1

1

998 s

51 A) + 15 B) + 8 (CH)A6,8

42

938

2

3

931 s

25 (B) + 20 (A) + 17 C-O)C3 + 11 (C=O) + 7 C-O)B3’

43

927

0

0

44

851

5

0

884 m

930 m

100 (CH)B5’,6’

883 w

98 (CH)B2’

845 m

34 (B) + 27 (C) + 7  (A) + 12 C-O)B3’,4’ + 7 (C=O)

878 m 45

837

6

4

847 w

46

823

11

0

47

816

14

0

48

802

2

0

49

802

4

0

805 s

50

780

3

8

784 s

51

772

1

0

771 sh

52

715

0

0

716 w

724 w

90 (B)

53

708

1

0

705 m

707 w

39 (C) + 16 (COH)C3 + 13 (COH)A5 + 9 (COH)A7

54

701

2

0

690 m

692 w

46 (A) + 11 (C) + 8 (B) + 22 (C=O)

55

680

0

2

56

662

0

1

57

638

1

0

58

634

3

4

824 vw 100 (OH)A5 818 s

816 vw 70 (CH)A6,8 + 30 (A) 56 (CH)B5’,6’ + 36 (CH)A8,6 55 (CH)A8,6 + 35 (CH)B6’,5’ 790 m

62 S(B) + 26 C-O)B3’,4’ 41 (C=O) + 27 (C) + 18 (A) + 11 (CH)A6

32 (A) + 18 (C) + 31 (B) 662 vw

635 m

662 w

34 (C=O) + 24 (B) + 18 (CH)B6’,5’ + 12 (OH)C3 + 9 (A)

641 m

67 (A) + 20 (CH)A8,6 37 (C) + 30 (A) + 13 (C=O)

26 59

617

8

0

60

611

10

0

61

602

5

8

62

580

2

1

48 (OH)C3 + 19 (C) + 12 (A) + 12 (B) + 11 (OH)A5 599 s

31 (OH)C3 + 30 (A) + 25 (C) + 16 (OH)A5 49 (B) + 12 (A) + 12 (C)

594 s

567 w

23 (C) + 15 (A) + 16 (COH)A5 + 14 (COH)B3’,4’ + 11 (COH)A7 + 8 (B)

63

567

4

4

573 s

557 sh

35 (COH)B3’,4’ + 34 (B) + 15 (A)

64

546

0

0

544 s

542 sh

43 (B) + 38 (OH)C3 + 10 (OH)B3’,4’

65

519

2

3

515 s

523 m

50 (A) + 21 (C) + 15 (COH)A5

66

481

1

4

489 s

490 m

41 (B) + 23 (COH)B3’,4’ + 20 (C)

67

453

0

1

459 m

458 w

34 (C) + 23 (A) + 16 (B) + 11 (COH)A5

68

452

0

0

442 s

442 w

78 (B) + 22 (OH)B3’,4’

69

406

2

0

404 s

405 m

61 (OH)C3 + 22 (C) + 12 (OH)B3’,4’

70

397

1

3

33 (A) + 23 (C) + 19 (COH) A5 + 9 (COH)A7

71

389

21

1

100 (OH)A7

72

375

8

1

372 m

379 w

36 (C=O) + 36 (COH)C3 + 12 (C)

73

365

25

1

352 s

352 w

80 (OH)B4’,3’ + 17 (B)

74

339

0

1

341 s

345 w

89 (OH)B3’,4’

75

335

2

1

76

321

13

0

77

309

3

0

310 w

301 vw 76 (COH)B4’,3’ + 14 (B)

78

285

3

1

302 m

291 vw 36 (C) + 11 (A) + 24 (COH)C + 15 (COH)B3’

79

284

0

0

266 m

270 w

30 (C-A) + 22 (A) + 20 (OH)A7 + 17 (C)

80

246

1

1

245 w

254 w

56 (A) + 25 (C) + 18 (OH)B3’

81

233

0

2

230 w

231 m

40 (B-C) + 23 (C) + 31 (A)

82

225

1

2

217 w

223 m

39 (C) + 24 (B) + 18 B-C)

83

222

0

1

165 m

84

198

0

1

154 m

165 m

52 (OH)B3’ + 19 (CH)B2’,5’,6’ + 16 (B) + 10 (C) + 9 (OH)A7

85

139

0

1

138 m

144 m

56 (C) + 18 (A) + 21 (B)

86

107

0

2

130 m

87

85

0

6

88

78

0

0

89

39

0

2

37 (COH)A7 + 19 (A) + 13 (C) + 15 (COH)A5 316 m

67 (OH)B3’,4’ + 17 (B) + 12 (C)

51 (OH)A5 + 25 (OH)A7 + 18 (A)

39 (C) + 22 (CH)B6’ + 15 (OH)B4’ + 12 (A) + 11 (B) 118 m

48 (A-C) + 33 (B-C)

111 m

106 m

46 (C) + 22 (A) + 21 (C-A) + 10 (OH)C3

104 m

99 sh

45 (C) + 32 (OH)C3 + 28 (B-C)

27 90

15

0

21

95 (B-C)

* scaling factor = 0.96 (3500 – 2500 cm-1) and 0.98 (2499 – 0 cm-1), in-plane vibrations:  – stretching;  – bending; out-ofplane vibrations:  – torsional;  – wagging vibrations; A – phenyl ring in chromone, B – phenyl ring, C - pyrone ring

28 Table 2. Experimental and calculated wavenumbers (cm-1) with PEDs and assignments of quercetin-5’sulfonic aid. No Calc. Int [% ] IR RS

Exp. IR

RS

PED

Calc. Q

1

3680 13

1

3575 w



100 OH)B3’ + H2O)

3681

2

3674 24

2

3515 m



100 OH)A7 + H2O)

3676

3

3634 29

1

2699m,



100 OH)SO3H

vb 4

3453 31

2

3459 w



99 OH)C3

3444

5

3425 100

2

3425 w



100 OH)B4’

3676

6

3228 69

2

3250 w



99 OH)A5

3211

7

3132

3

0

3185 w



100 CH)B6’

3032

8

3097

0

1

3101 w



100 CH)A8

3096

9

3071

1

1



100 CH)B2’

3067

10 3058

1

3

3059 w



100 CH)A6

3057

11 1659 84

35

1650 w

50 A) + 18 C) + 21 (OH)A5

1659

12 1639 17

63

1637 m

1641 vs

47 C) + 18 (OH)C3 + 12 B)

1635

1612 vs

61 B) + 10 (CH)B6’,2’ + 9 C=O)

1615

1599 sh

50 A) + 16 C) + 19 C=O)

1603

66 B) + 17 (OH)B4’ + 11 (CH)B2’

1601

45 A) + 17 C) + 22 C=O)

1570

13 1613 10 100 14 1603 92

38

15 1592 15

3

16 1574 22

46

1558 m

1547 vs

17 1510 36

12

1510 w

1514 vw 34 A) + 9 C) + 18 (CH)A6 + 16 (OH)A5

18 1505 56

2

1505 w

1499 w

19 1487 56

7

1480 w

20 1453

9

2

1597 m

1461 m

1511

46 B) + 22 (CH)B6’,2’ + 12 C-O)B4’

1534

43 C) + 21 A) + 20 (OH)A5

1489

33 B) + 15 (OH)B4’ + 10 (OH)B4’,3’ + 7

1448

(CH)B6 21 1432 13

25

1429 m

1435 m

26 C) + 16 A) + 14 C-OH)A5 + 9 (OH)A 1432 + 7 (CH)A8

22 1406

3

3

1408 w

20 (OH)B4’ + 19 C) + 15 A) + 13 B) +

1405

12 (OH)A5 23 1400 70

52

1400 s

28 B) + 20 (OH)B4’ + 14 A) + 10 (CH)B6’+ 9 C)

1357

29 24 1381 41

2

1384 m

1387 w

30 (OH)C3 + 21 C) + 17 A) + 11 C-

1384

OH)A5 5

1

1361 m

32 B) + 30 S=O) + 7 (OH)B3’

26 1342 49

68

1314 s

24 (OH)C3 + 24 B-C) + 22 (B) + 11 C-

25 1346

1341

O)B3’ 27 1334 17

45 S=O) + 18 B) + 17 (CH)B6’,2’ + 12

32

C-O)B4’ 28 1329 17

6

51 A) + 16 C) + 13 C-OH)A5 + 8

1306 s

1329

(CH)A8,6 29 1282 42

2

1287 w

23 A) + 14 C) + 18 C-O)B3’ + 15

1279

(OH)C3 + 11 B) + 11 (CH)B2’ 30 1267 37

4

31 1250

1

5

38 B) + 25 C-O)B4’ + 16 (CH)B6’,2’

1266 w

26 A) + 12 C) + 20 (CH)B2’,6’ + 13 C-

1242

O)B3’ + 12 C-O)C3 32 1242 14

2

1242 w

27 (OH)A7 + 27 C) + 22 A) + 10

1249

(CH)A8,6 33 1220 93

3

1220 m

1224 vw 34 B) + 19 (OH)B4’ + 16 (OH)B3’ + 10

1182

(CH)B6’ 34 1192 19

10

1190 s

29 C) + 14 (CH)A6 + 18 (OH)B3’ + 9 C-

1193

O)C3 35 1180 19

6

36 1159 98

4

37 1149 20

1

38 1136 21

3

39 (CH)A6 + 19 C-O)A3

1176 m 1169 sh

1180

27 (OH)A7 + 23 (CH)A8 + 13 C) + 11 A) 1156 55 (OH)SO3H + 18 S=O)

1134 vs

1127 m

22 (OH)SO3H + 22 B) + 14 (OH)B3’ + 12

1118

C) + 8 (CH)A8 39 1118

1

8

21 B) + 20 C) + 14 (CH)B6’,2’ + 13

1118 vs

1108

(CH)A8 + 7 (OH)B3’ 40 1097 19

2

1093 s

1095 w

68 S=O) + 12 (OH)SO3H

41 1088 12

4

1030 m

1031 m

45 C) + 16 A) + 9 S=O)

1088

42 1030 16

3

1018 vs

1024 m

48 B) + 15 C) + 11 A)

1011

43 1000

1

1001 s

1002 w

54 A) + 16 (CH)A + 9 C-O)A

1011

1

30 44

949

1

4

935 m

938 vw

28 (A) + 16 C-O)C3 + 14 (B) + 10 (C=O)

938

+ 10 C-O)B3’ 888 w

100 (CH)B6’

45

902

1

0

46

878

8

1

884 m

33 B) + 22 CS) + 8 C-O)B3’ + 8 (C)

47

869

4

0

863 w

97 (CH)B2’

851

48

830

7

14

842 m

55 (B) + 14 C-O)B4’ + 9 (C)

837

49

821

5

0

833 w

80 (OH)A5 + 20 (CH)A6

823

50

817

20

0

826 w

50 (CH)A6,8 + 30 (OH)A5 + 20 (A)

816

51

804

0

0

90 (CH)A8,6 + 10 (A)

802

52

775

58

3

791 vw

81 S-OH)

53

773

1

0

771 w

41 (C=O) + 28 (C) + 17 (A) + 11 (CH)A6

772

54

731

1

0

743 w

745 w

96 (B)

715

55

725

4

10

715 w

725 w

29 (B) + 15 (A) + 11 (C) + 17 S-OH)

56

715

0

0

834 m

43 (C) + 16 C-O)C3 + 10 (COH)A5 + 10

927

708

(A) 57

704

1

0

700 vw

58

687

11

1

690 w

59

664

0

1

664 w

704 vw

52 (A) + 28 (C) + 13 (C=O)

701

97 (OH)B4’ 663 w

34 (COH)C3 + 24 (B) + 14 (C=O) + 13

662

(CH)B2’,6’ + 10 (A) 60

639

1

0

61

638

3

2

62

630

2

1

641 m 637 m 626 m

68 (A) + 20 (OH)A7

638

42 (C) + 33 (A) + 9 (COH)B 3’

634

20 (A) + 19 (C) + 13 (COH)B + 11 CS) + 10 (S=O)

63

616

3

33 (A) + 16 (C) + 27 (OH)C3 + 12 (OH)A5

1

617

+ 10 (B) 64

613

0

12

65

609

14

1

604 s

66

576

39

1

584 s

67

574

4

6

68

566

1

0

543 m

28 (B) + 16 (COH)B4’ + 16 (C)

602

606 m

54 (OH)C3 + 21 (A) + 10 (C) + 9 (OH)A5

611

589 m

48 (S=O) + 16 (B)

573 m

36 (A) + 25 (C) + 16 (COH)A5

550 w

38 (B) + 22 (CS) + 20 (S=O) + 16 (OH)C3

580

+ 11 (S-OH) + 10 (OH)B3’ 69

528

0

0

37 (B) + 26 (OH)C3+ 23 (S=O) + 7 (OH)B4’ 546

31 70

522

2

1

71

509

1

7

72

465

1

1

73

455

0

2

74

439

5

1

446 m

75

408

1

0

411 m

497 m

522 m

34 (A) + 20 (C) + 16 (COH)A5 + 9 (B)

519

499 w

41 (B) + 18 (A) + 16 (C) + 8 C-O)B3’

481

464 w

77 (S=O) + 15 (B) + 8 (OH)B4’ 46 (C) + 16 (A) + 12 (COH)A5 8 (COH)A7 453 64 (S-OH) + 20 (S=O) + 12 (B)

417 w

55 (OH)C3 + 15 (C) + 10 (OH)B4’ + 8

406

(CH)B2’,6’ 76

397

1

4

404 w

77

386

19

2

395 m

78

376

7

0

377 m

79

372

2

0

392 w

41 (A) + 23 (C) + 18 (COH)A5

397

100 (OH)A7

389

32 (C=O) + 24 (COH)C3 + 14 (C)

375

28 (OH)B3’ + 24 (OH)B4’ + 20 (OH)C3 + 14

365

(S-OH) + 9 (CH)B2’ 80

360

2

1

367 m

24 (COH)B4’ + 16 (S=O) + 13 (B) + 13 (COH)B3’ + 10 (COH)C3 + 8 (COH)A7

81

344

4

0

348 m

347 vw

25 (COH)B3’ + 48 (S=O) + 18 (B) + 9 (COH)B4’

82

330

4

2

324 vw

335 w

28 (COH)A7 + 13 (COH)A5 + 13 (A) + 8

321

(C) + 21 (S=O) 83

328

15

1

318 vw

328 w

85 (OH)B3’

84

312

1

4

305 vw

306 w

27 (B) + 24 (S=O) + 19 CS) + 11

285

(COH)C3 85

286

0

0

289 w

291 w

30 (C-A) + 23 (C) + 15 (OH)A7 + 12 (A) + 284 11 (OH)A5

86

277

1

0

268 w

275 vw

37 (B) + 25 (S-OH) + 13 (C)

87

262

0

1

257 w

261 w

20 (S-OH) + 19 (C) + 16 (A) + 14 (B) + 9 (COH)C3

88

245

0

1

89

240

0

1

90

222

0

2

91

221

1

3

92

194

0

2

40 (A) + 21 (B) + 20 (C) 36 (CS) + 18 (B) + 16 (COH)B3’

233 m 226 w

176 w

246

189 w

51 (OH)A5 + 25 (OH)A7 + 19 (A)

225

33 (C) + 33 (B) + 23 B-C)

222

24 (OH)B3’ + 22 (C) + 15 (CH)B2’ + 15 (S- 198 OH) + 12 (OH)A7 + 11 (OH)B4’

32 93

170

16

5

168 vw

94

139

0

5

139 s

95

138

0

7

132 s

96

108

0

2

124 s

97

95

0

6

115 s

79 (OH)SO3H + 18 (S=O) 41 (C) + 27 (CS)

130 w

113 w

37 (C) + 7 (A) + 25 (CS) + (B-C)

139

42 (C) + 7 (A) + 9 (B) + 35 (B-C)

107

52 (CS) + 26 (B) + 22 (OH)B3’ + 8 (OH)B4’ + 7 (S-OH)

98

80

0

1

101 vw

46 (C) + 15 (A) + 20 (C-A) + 10 (OH)C3 + 85 8 (OH)A7

99

66

0

2

100

39

0

4

83 vw

90 (B-C) 39 (C) + 31 (COH)C3 + 21 (CH)B3’ + 10 (S- 39 OH) = (B-C)

101

23

0

6

37 (S-OH) + 45 (S=O) + 8 (B)

102

11

0

17

88 (B-C)

15

* scaling factor = 0.96 (3500 – 2500 cm-1) and 0.98 (2499 – 0 cm-1), in-plane vibrations:  – stretching;  – bending; out-ofplane vibrations:  – torsional; A – phenyl ring in chromone, B – phenyl ring, C - pyrone ring

33 Table 3. Hydrogen bond geometry (Å, °) and wavenumbers (cm-1) for Q and QSA. D-H...A

D-H HA Exp. Calc. Exp. Calc.

DA Exp. Calc.

D-HA Exp. Calc.

Q O-HA5O

0.982

0.987 1.678 1.748

2.576

2.641

149.9

O-HC3O

1.001

0.976 2.280 1.984

2.708

2.614

104.4

-

2.640 2.619 2.673

-



148.8

3223 (3236) 120.1 3283

QSA O-HA5O O-HC3O S-OH

-

0.986 0.976 0.975

-

1.756 2.001 1.786

148.4 119.2 149.6

3250 3459 2699