COMBINED EXPERIMENTAL AND THEORETICAL STUDIES ON THE VIBRATIONAL, ELECTRONIC AND NMR SPECTRA OF 5-QC M KUMRU, M KOCADEMR, T BARDAKI Department of Physics, Faculty of Arts and Sciences, Fatih University, Bykekmece, Istanbul, Turkey 1 Outline Introduction Experimental Details Quantum Chemical Calculations Results Molecular Geometry Vibrational Analysis (IR aand Raman) Uv-Vis Spectrum Frontier molecular orbitals Molecular electrostatic potential map Charge Analysis NMR Spectra Conclusion Acknowledgements 2 (C 9 H 7 N) Quinoline is an aromatic nitrogen compound characterized by a solid-ring structure contains a benzene fused to pyridine at two adjacent carbon atoms. It can be obtained by the distillation of coal tar. Quinoline Introductio n 3 Quinoline 5-Quinolinecarboxaldehyde (C 10 H 7 NO) 4 Experimental Details The solid 5QC was purchased from Alfa Aesar Company (Karlsrule, Germany) at reagent grade (purity of %98) and used without any further purification. 5-Quinolinecarboxaldehyde 5 The mid region ( cm -1 ) room temperature FT-IR spectrum was recorded on Thermo Nicolet 6700 Series Spectrometer with attenuated total reflectance (ATR) technique. The far region FT-IR (FT-FIR) spectrum of 5QC ( cm -1 ) was recorded at the room temperature on Thermo Nicolet 6700 Spectrometer as polyethylene (PE) pellet. Experimental Details Infrared 6 Experimental Details Far-infrared The best quality for the FT-FIR spectra was obtained when the sample/PE ratio of the PE pellets is around 1/10. the sample and PE were mixed ground in a mortar. Then, a metallic anvil die was heated to nearly C on a heater. After the temperature of the die reaches to C, the metallic die that includes the mixture put under 5-tones pressure for 2 minutes. 7 The room temperature FT-Raman spectrum of 5QC ( cm -1 ) was recorded with the 1024 nm laser excitation line by using Thermo Nicolet Spectrometer 6700 used also in recording the FT- FIR spectrum. The room temperature UV-Vis absorption spectrum of 5QC dissolved in water was recorded in the range of nm with Xenon flash lamp on Thermo Scientific Evolution 300 Spectrometer. 8 Experimental Details Raman and Uv-Vis 9 1 H and 13 C NMR spectra were recorded on a Bruker Avance 400 Ultrashield Spectrometer equipped with a 5 mm SEI probe with Z-gradient coils, using a Bruker Automatic Sample Changer (B-ACS 60). 1 H NMR spectra were acquired at 300K with sample rotation. 16 scans and 2 prior dummy scans of 65 k points were acquired with a spectral width of ppm, a receiver gain of 144, and an acquisition time of s. 13 C NMR spectra were acquired using a Bruker zgpg30 pulse sequence with 128 scans and 0 prior dummy scans. Experimental Details Nmr Quantum Chemical Calculations 10 All quantum chemical calculations were performed by using Gaussian 03 (with Linda) program package on linux server cluster. The geometrical structures 5QC were optimized at the HF and B3LYP levels with the G** basis set. The optimized structures were then subjected to spectral calculations. The calculated normal modes of 5QC were assigned based on the atomic displacements visualized by using the GaussView program Quantum Chemical Calculations 11 UV-Vis absorption spectra have been calculated by using time-dependent (TD)-DFT method with B3LYP functional and G** basis set in both gas phase and in water but at gas-phase geometry. The UV-Vis spectra were simulated from the calculated forty TD-B3LYP lowest-lying vertical excitation energies and their associated oscillator strengths. Results Molecular Geometry Conformational analysis locates two stable conformers (Conf1 and Conf2) for 5QC due to the orientation of the carboxaldehyde moiety. 12 13 Results Molecular Geometry Bond Lengths 14 Results Molecular Geometry Bond Angles Results IR Spectra of 5QC 15 Results Raman Spectra of 5QC 16 Results Vibrational Analysis 17 5QC has N = 19 atoms and, thus 3N = 57 degrees of freedom. When the three translational (2A' + 1A'') and three rotational (1A' + 2A'') degrees are subtracted, the remaining 51 modes for the vibrational degrees of freedom transform under the C s symmetry as 35A' + 16A'' Results and Discussion Vi brational Analysis 18 Results and Discussion Vibrational Analysis 19 Continued. The ring C-H stretchings of 5QC are at 3100, 3097, and 3055 cm -1 in the IR spectrum, and at 3091 and 3060 cm -1 in the Raman spectrum. The C-H stretching of carboxaldehyde group of 5QC is at 2955 cm -1 (IR) and 2925 cm -1 (Raman). The C-H in-plane bendings of 5QC are at 1142, 1159, 1205, 1230, 1314, 1367, 1407, 1431, and 1497 cm -1 in the IR spectrum and 1043, 1159, 1205, 1230, 1317, 1367, 1405, 1432, and 1498 cm -1 in the Raman spectrum. The C-H out-of-plane bendings of 5QC are at 961, 983, and 1004 cm -1 in the IR spectrum and 962, 982, and 1004 cm -1 in the Raman spectrum. 20 Results and Discussion Vibrational Analysis The ring C-C stretchings appears at 1367, 1614, and 1626 cm -1 in the IR spectrum, and at 1367, 1614, and 1625 cm -1 in the Raman spectrum. The stretching frequency of the C-C bond between the ring and carboxaldehyde moiety of 5QC (1230 cm -1 both in IR and Raman) is in the expected region of this vibration ( cm -1. The frequency of the ring C=N ring stretching of 5QC that appears at 1314 cm -1 (IR), 1317 cm -1 is also consistent with literature values. The C=O stretching frequency of the carboxaldehyde moiety of 5QC {1684 cm -1 (IR), 1687 cm -1 (Raman)} lies within the literature range of 172565 cm Results and Discussion Vibrational Analysis Results Uv-Vis Spectrum of 5QC 22 Results Characteristics of experimental and calculated electronic absorption spectra 23 UV-Vis spectra based on the TD-B3LYP/ G** vertical excitation wavelengths (nm) and oscillator strengths f that relate to absorbance in the experimental spectra are reasonably close to each other Results Frontier molecular orbitals 24 The energies (eV) of frontier molecular orbitals and the involving physicochemical global molecular characteristics of 5QC Results Molecular electrostatic potential map 25 Molecular electrostatic potential (MESP) is defined as ; Where, Z A is the charge on nucleus A located at R A and p(r) is the electronic density. It can be calculated in terms of theoretical methods. Results Charge Analysis 26 Charge distribution analyses were performed with B3LYP method using both 6-31G* and G** basis sets and applying Mulliken, electrostatic potential (ESP), and the most sophisticated natural bond analysis (NBO). 27 Proton NMR spectrum of 5QC shows seven signals arising from the seven hydrogen atoms present in the structure. Six of these spin-spin coupled hydrogen atoms are on the benzene (H2, H3, and H4) and pyridine (H7, H8, and H9) moieties while one proton is on the carboxaldehyde group (H10). Results 1 H NMR spectrum Results 13 C NMR Spectrum 28 Several molecular characteristics of 5-quinolinecarboxaldehyde (5QC) have been studied. It has been shown to have two stable conformers due to the orientation of carboxaldehyde moiety. These two conformers lie energetically very close to each other with a small transition barrier. Therefore, they are expected to coexist at the room temperature. The comparison of the calculated geometry parameters of 5QC with the previously available X-ray data of analogous compounds reveal that the position of the carboxaldehyde moiety does not alter much the geometry parameters of the quinoline moiety. The normal modes in the presently recorded IR and Raman spectra of 5QC have been assigned based on the present quantum chemical calculations. When the calculated vibrational frequencies are scaled, the calculated vibrational spectra with HF and B3LYP methods are very similar to each other, validating the use of both methods in the vibrational studies of analogous compounds. 29 Conclusion 30 We have proven B3LYP method to be quite successful in UV-Vis spectral calculations on 5QC. Therefore, the bands in the experimental UV-Vis spectra have been assigned based on frontier molecular orbitals. Frontier molecular orbitals have been also used in estimating some physicochemical parameters of 5QC. Molecular electrostatic potential plots show the most reactive atoms in terms of nucleophilic attack are the nitrogen and oxygen atoms. The calculations of atomic charges have been shown to be challenging and the quality of several charge analysis schemes has been discussed. Finally, the presently recorded 1 H and 13 C NMR spectra have been analyzed. Our Some Related Articles : [1] V. Kk, A. Altun, M. Kumru, Spectrochim. Acta Part A, 85(2012)9298 [2] M. Kumru, V. Kk, T. Bardak, Spectrochim. Acta Part A, 90(2012)2834 [3] M. Kumru, V. Kk, M. Kocademir, Spectrochim. Acta Part A, 96 (2012) 242251 [4] M. Kumru, V. Kk, P. Akyrek, Spectrochim. Acta Part A, 113(2013) 7279 [5] M. Kumru, V. Kk, M. Kocademir, H.M. Alfanda, A. Altun, L. Sar, Spectrochim. Acta Part A, 134 (2015) 8189 [6] M. Kumru, A. Altun, M. Kocademir, V. Kucuk, T. Bardak, . amaz, Combained experimental and quantum chemical studies on structural and spectroscopic (FT-IR, FT-Raman, UV-Vis, and NMR) characteristics of 5-quinolinecarboxaldehyde (in preperation) 31 Acknowledgements We thanks Scientific Research Fund of Fatih University under the project number P _G (1457) The Turkish Scientific and Technical Research Council (TBTAK) for their financial support through National Postdoctoral Research Scholarship Programme 32 THANK YOU 33