FORMATION OF CO-CRYSTAL AND CHARACTRIZATION OF ASPIRIN WITH CITRIC ACID AND PERCHLORIC ACID C.Muthuselvi.M.Sc.,M.Phil., Assistant Professor of Physics Devanga Arts College (Autonomous) Aruppukottai

Co-Crystals Co-Crystals are crystalline materials composed of two or more molecules held together within the same crystal lattice. Co-Crystals can be constructed through the several types of interaction, including hydrogen bonding and van der walls forces

Formation of Aspirin -Citric acid and Aspirin-Perchloric acid co-crystal Slow evaporation method Ethanol as a solvent Colorless crystals obtained The grown crystals are shown in figure

Characterization of Aspirin- Citric acid and Aspirin-Perchloric acid co-crystal Powder XRD FT-IR and Raman spectroscopy UV-Visible Spectroscopy

Powder XRD Crystalline quality of grown crystals were studied by powder diffraction analysis using a XPERT-PRO diffractometer with CuKα (1.540Å)in the 2Ɵ range . S.No 2Ɵ (degree) dspacing (Å) 1. 10.63 8.309 2. 16.93 5.232 3. 27.65 3.222 4. 33.01 2.711 S.No 2Ɵ (degree) d spacing (Å) 1. 5.42 16.295 2. 7.370 11.984 3. 10.573 8.360 4. 15.179 5.832

Powder XRD Pattern The X-ray powder diffraction analysis revealed the formation of Co-crystals of Aspirin with citric acid and Perchloric acid in the crystalline form

FT-IR and Raman spectroscopy The infrared and Raman spectroscopy studies are employed for the identification of the functional groups present in medically important drug namely Aspirin-citric acid and Aspirin-Perchloric acid co-crystal . The FT-IR spectrum of Aspirin-citric acid and Aspirin-Perchloric acid co-crystal was recorded using SHIMADZU FT-IR spectrometer in the range 4000-400 cm-1.

The Raman spectrum of Aspirin-citric acid and Aspirin-Perchloric acid co-crystal was recorded using Princeton Acton SP-2500 Raman spectrometer in the range 3500-500 cm-1. The observed Infrared and Raman spectra are illustrated in figure and the observed wave numbers of the various functional groups of title compound are tabulated.

FT-IR and Raman spectrum

Vibrational frequencies of Aspirin-citric acid Co-Crystal IR ν(cm-1) Raman ν(cm-1) Assignment - 3240(s) ν (OH) 3018(m) 3083(s) ν(CH) 2870(w) 2833(w) 2940(s) CH3.Str. 1755(s) 1689(br) 1605(s) 1604(s) C=O.Str 1575(m) 1523(w) C=C.Str. 1428(w) CH2Sci. 1274(w) C-OH.bending 665(s) 514(m) 424(m) 661(w) 428(m) COO.Bending

Vibrational frequencies of Aspirin-Perchloric acid Co-Crystal IR ν(cm-1) Raman ν(cm-1) Assignment 3236(s) 3231(w) ν(OH) - 3061(w) 3086(m) 3055(m) ν(CH) 3008(w) 2858(m) 1483(m) 1474(m) CH3 .Str. 1747(w) 1658(w) 1632(s) C=O.Str 1610(s) 1577(m) 1527(m) 1578(s) C=C Str. 696(s) 657(s) 530(s) 462(s) 675(w) 527(w) 452(s) ClO3 .Def. 567(s) 430(w) 569(s) ClO4

The frequency assignments have been made for various functional groups Due to the effect of hydrogen bonding the observed stretching modes and bending modes appear at slightly lower and higher wavenumbers respectively than those expected for free aspirin drug. This study confirms the presence of both molecules in the co-crystal form due to the hydrogen bonding between them.

UV-Visible Spectroscopy The optical transmittance and absorption spectrum of grown crystal has been recorded with SHIMADZU-UV 1601 double beam spectrometer in the range 200-1100 nm to find the suitability of crystal for optical applications. The optical transmittance and absorption spectrum of grown crystals are shown in graphs

The crystal shows a good transmittance in the visible region . From the absorption spectrum, there is no significant absorption in the entire range of visible light. A good optical transmittance from ultraviolet to Infrared region is very useful for optical applications .

Conclusion Co-crystallization technique was used to combine two drugs in a single solid phase and thus to achieve a newer approach for combination therapy. Using the newer approach, Co-crystals of Aspirin with Citric acid and Aspirin with Perchloric acid were prepared in this work.

Synthesis of Co-Crystals of Aspirin – Citric acid and Aspirin-Perchloric acid were successfully carried out by slow evaporation method. Ethanol is the best solvent for the formation of co-crystals. The X-ray powder diffraction analysis revealed the formation of Co-crystals of Aspirin with citric acid and Perchloric acid in the co-crystalline form.

The FT-IR and Raman spectra confirms the presence of both molecules and the frequency assignments of various functional groups explain the nature of hydrogen bonding between them. The optical transparency was found out for each crystal by recording the UV-Visible spectrum. They show that the co-crystals have the optical transparency above 90% .

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