Vibrational spectra and molecular structural investigation of quiniodochlor

Transcription

1 Indian Journal of Pure & Applied Physics Vol. 42, March 2004, pp Vibrational spectra and molecular structural investigation of quiniodochlor S Gunasekaran, U Ponnambalam *, S Muthu * & G Anand + PG & Research Department of Physics, Pachiyappa's College, Chennai * PG Department of Physics, Presidency College, Chennai Department of Physics, A M A College of Engineering, Vadamavandal Received 9 July 2003; revised 2 January 2004; accepted 28 January 2004 A normal coordinate analysis on quiniodochlor has been carried out with a systematic set of symmetry coordinates following Wilson's F-G Matrix method. The potential constants evaluated for the molecule are found to be in good agreement with literature values thereby confirming the vibrational assignments. To check whether the chosen set of vibrational frequencies contribute maximum to be potential energy associated with the normal coordinates of the molecule, the potential energy distribution has been evaluated. [Keywords: Normal coordinate analysis, vibrational spectra, quiniodochlor, F-G Matrix.] IPC Code: G 01J 3/44 1 Introduction Quiniodochlor is used as anti-bacterial and antifungal drug in the treatment of skin infections. An extensive work has been carried out on the title compound and its derivatives in recent years 1-5. The characteristic vibrational frequencies of this drug have been identified and assigned on the basis of their relative intensity, characteristic positions and correlation of vibrational bands of related compounds. Probable assignment has been made but no attempt has been made on normal coordinate analysis. Hence, in the present work, normal coordinate analysis has been carried out on the basis of C s symmetry. 2 Experimental Details The pure sample of quiniodochlor was obtained from Sigma Chemical Company, USA and used as such. The FTIR and FT-Raman spectra of the sample were recorded in the region cm -1 and cm -1 respectively using BRUCKER IFS 66V FTIR spectrometer at RSIC, Chennai, India. The FTIR and FT-Raman spectra are presented in Fig Normal Coordinate Analysis Quiniodochlor has 48 fundamental modes of vibration under C s symmetry point group which are distributed as Γ vib = 31 A + 16A", all the fundamentals are active both in the infrared and Raman. In the present work only 31 modes are considered. The structure, orientation of the principle axes and the nomenclature of the parameters of the quiniodochlor molecule are shown in Fig. 2. A set of symmetry coordinate has been arrived using the knowledge of projection operator and the character table pertaining to the C s point group symmetry. The symmetry coordinates thus obtained are as follows: A species S 1 = ΔD; S 2 = Δh; S 3 = 1/ 6 [Δa 1 + Δa 2 + Δa 3 + Δa 4 + Δa 5 + Δa 6 ] S 4 = 1/ 2 [Δd 1 +Δd 2 ]; S 6 =ΔT; S 7 =Δt; S 8 =Δr; S 9 =Δl S 10 = 1/ 3[ΔR 1 + ΔR 2 + ΔR 3 ]; S 11 = 1/ 6 [Δα 1 + Δα 2 + Δα 3 + Δα 4 + Δα 5 + Δα 6 ] S 12 = 1/ 2 [Δβ 1 + Δβ 2 ]; S 13 = Δγ ; S 14 = 1/ 3 [Δε 1 + Δε 2 + Δε 3 ]; S 15 = 1/ 2 [Δω 1 + Δω 2 ] S 16 =Δχ; S 17 =1/ 2[Δσ 1 + Δσ 2 ]; S 18 = 1/ 2 [Δθ 1 + Δθ 2 ]; S 19 = 1/ 2[Δφ 1 + Δφ 2 ] S 20 = Δτ

2 GUNASEKARAN et al.: VIBRATIONAL SPECTRA OF QUINIODOCHLOR 163 Fig. 1 Vibrational spectra of quiniodochlor (a) FT - Raman spectrum (b) FTIR spectrum A" Species S 21 = 1/ 2 [2Δa 1 - Δa 2 - Δa 3 + 2Δa 4 - Δa 5 - Δa 6 ]; S 22 = 1/ 2 [Δd 1 - Δd 2 ]; S 23 = 1/ 2 [Δb 1 - Δb 2 ]; S 24 = 1/ 6 [2ΔR 1 - ΔR 2 - ΔR 3 ] S 25 = 1/ 12[2Δα 1 - Δα 2 - Δα 3 + 2Δα 4 - Δα 5 - Δα 6 ]; S 26 = 1/ 2 [Δβ 1 - Δβ 2 ]; S 27 = 1/ 6 [2Δε 1 - Δε 2 - Δε 3 ]; S 28 = 1/ 2[Δω 1 - Δω 2 ]; S 29 = 1/ 2 [Δσ 1 - Δσ 2 ] S 30 = 1/ 2 [Δθ 1 - Δθ 2 ]; S 31 = 1/ 2 [Δφ 1 - Δφ 2 ]

3 164 INDIAN J PURE & APPL PHYS, VOL 42, MARCH 2004 Fig. 2 Structure, nomenclature of parameters and the orientation of the principle axes of quniniodochlor where Δ s represent changes in the corresponding bond distances and bond angles. The required structural data were taken from literature 5. 4 Results and Discussion A normal coordinate analysis for quiniodochlor has been carried out using the observed wave numbers from FTIR and FT-Raman spectra. The evaluation of force constants is made on the basis of general valence force field by applying Wilson's F-G matrix method. The initial set of force constants for the quiniodochlor have been taken from related molecules. This set of force constants was subsequently refined by keeping a few interaction constants fixed throughout the refinement process. (i) C-H vibrations The C-H stretching vibrations of a heterocyclic aromatic compound fall in the region cm -1. In this region the bands are not much affected by the nature and position of the substituents 6. In the present work band observed at 3028 cm -1 (υ 10 ) in FTIR and 3025 cm -1 in FT Raman is assigned to C-H symmetric stretching. The bands observed at 3100 cm -1 (υ 24 ) in FTIR and 3105 cm -1 in FT-Raman are assigned to C-H asymmetric stretching. (ii) C-O stretching The band due to the C-O stretching vibrations of lactones occurs in the region cm -1. In the present work, the bands observed at 1270 cm -1 (υ 8 ) in IR and 1275 cm -1 in Raman are assigned to C - O stretching vibration.

4 GUNASEKARAN et al.: VIBRATIONAL SPECTRA OF QUINIODOCHLOR 165 Table 1 Vibrational assignment, force constants and PED values of quiniodochlor Symmetry coordinate Frequency (cm -1 ) Assignment Force const 10 2 N/m PED % FTIR FTRaman A Species S (w) 1500(s) C - C stretching S 2 563(s) 566(w) C - I stretching S (m) 1463(w) ring C C symmetric stretching S (s) ring C N symmetric stretching S (s) 1580(w) ring C C symmetric stretching S 6 649(vs) C - Cl stretching S (w) 3125(m) C - H stretching S (s) 1275(w) C - O stretching S (m) O - H stretching S (w) 3205(m) C - H symmetric stretching S (w) 475(m) C - C - C symmetric bending S (w) 445(m) C - C - N symmetric bending S (w) 415(m) C - N - C symmetric bending S (w) 550(m) C - C - C symmetric bending S (w) 595(m) C - C - O symmetric bending S (w) 440(m) C - O - H bending S (w) 410(m) C - C - I symmetric bending S (w) 1090(m) C - C - H symmetric bending S (w) 460(m) C - C - Cl symmetric bending S (vs) 950(w) C - C - H bending A" Species S (m) 1640(w) ring C C asym stretching S (w) 1545(s) ring C N asym stretching S (m) 1610(w) ring C C asym stretching S (m) C - H asym stretching S (w) 505(m) C - C - C asym bending S (w) 535(m) C - C - N asym bending S (w) 575(m) C - C - C asym bending S (w) 615(m) C - C - O asym bending S (w) 425(m) C - C - I asym bending S (m) 1205(w) C - C - H asym bending S (m) 490(w) C - C - Cl asym bending (iii) C-Cl vibration The C-Cl stretching vibrations 8 give generally strong bands in the region cm -1. In the present work, the bands observed at 649 cm -1 (υ 6 ) in IR and 650 cm -1 in Raman are assigned to C - Cl stretching vibration. The remainder of the observed frequencies and their corresponding assignments are presented in Table 1.

5 166 INDIAN J PURE & APPL PHYS, VOL 42, MARCH Potential Energy Distribution To check whether the chosen set of vibrational frequencies contribute the maximum to the potential energy associated with the normal coordinates of the molecule, the potential energy distribution has been calculated using the relation PED = F ii L 2 ik / λ k. PED is the contribution of the i th symmetry coordinate to the potential energy of vibration whose frequency is υ, F ii is the force potential constant, L ik is the L matrix element and λ k = 4π 2 C 2 υ 2. The calculated force constants and the potential energy distribution are presented in Table 1. References 1 Acheson R M, An introduction to chemistry of hetero cyclic compounds. Third Edition (John Wiley, New York), Tripathi K D, Medical Pharmacology, 3E (Jaypee Medical Publishers, New York) Indian Pharmacopeia, Vol. 1 & 2 (Controller of Publications Civil Lines, New Delhi) Gunasekaran S, Ponnambalam U, Muthu S & Anand G, Proceedings of the national symposium on atomic molecular structure, interactions and laser spectroscopy, Varanasi (2002). 5 Sutton L E, The interatomic bond distances and bond angles in molecules and ions, (Chemical Society, London), Asish Sharma & Sharma S D, Acta Ciencia Indica, Vol. XXVII P, No.2 (2001) Silverstein R M, Clayton Basslor & Morril T C, Spectroscopic identification of organic compounds, 5E (John Wiley, New York) Shreemathi S, Ph.D. thesis, University of Madras, India, 2001.