Synthetic co-crystals of anhydrous guanine and process for preparing the same
This invention is directed to synthetic co-crystals of anhydrous guanine and at least one additional material, wherein the co-crystals have a high refraction index and therefore, provide products with pearlescence or whiteness with high coverage. The invention is further directed to a process for the preparation of anhydrous guanine and of the co crystals.
1. Synthetic co-crystals comprising anhydrous guanine and at least one additional material; wherein the at least one additional material is guanosine, and wherein the co-crystals have a plate morphology.
2. The synthetic co-crystals according to claim 1 , having a refractive index between 1.75-1.86.
3. Paints, coatings, printing inks, plastics, cosmetic formulations, food products, paper, agricultural products, and medicaments, comprising the synthetic co-crystal according to claim 1 .
4. Synthetic co-crystals consisting of anhydrous guanine and one additional material; wherein the one additional material is selected from the group consisting of hypoxanthine, xanthine and guanosine, wherein the co-crystals have a plate morphology.
5. The synthetic co-crystals according to claim 4 , wherein the one additional material is hypoxanthine or xanthine.
6. The synthetic co-crystals according to claim 4 , wherein the one additional material is guanosine.
7. The synthetic co-crystals according to claim 4 , having a refractive index between 1.75-1.86.
8. The synthetic co-crystals according to claim 4 , wherein said co-crystals are 5-250 μm long and/or 1-50 μm wide and/or 20-500 nm thick.
9. The synthetic co-crystals according to claim 4 , wherein said co-crystals have an average size of about 0.01-10 μm.
10. The synthetic co-crystals according to claim 4 , wherein said co-crystals have a smooth surface.
11. The synthetic co-crystals according to claim 5 , wherein the one additional material is hypoxanthine.
12. The synthetic co-crystals according to claim 11 , wherein the co-crystals are characterized by an X-ray powder diffraction having a noticeable shift from pure anhydrous guanine and higher ratio of the intensity of the (100) to the (012) diffraction peaks.
13. The synthetic co-crystals according to claim 11 , wherein the co-crystals have a rectangular shape.
14. The synthetic co-crystals according to claim 11 , wherein the co-crystals are free of impurities originating from crystals isolated from fish scales.
15. Paints, coatings, printing inks, plastics, cosmetic formulations, food products, paper, agricultural products, and medicaments, comprising the synthetic co-crystal according to claim 4 .
16. A pH controlled process for preparing the synthetic co-crystals according to claim 1 , wherein said process comprises the steps of:
preparing a basic or acidic aqueous solution of guanine and the at least one additional material;
maintaining the basic or acidic aqueous solution at a predetermined temperature range for a predetermined period of time;
filtering the basic or acidic aqueous solution to provide a filtrate;
adjusting the pH of the filtrate by adding a base or an acid to the filtrate over a predefined period of time until a predetermined pH value is obtained, thereby providing a synthetic co-crystal suspension comprising co-crystals;
allowing the synthetic co-crystal suspension to mature over a predetermined period of time; and
collecting the synthetic co-crystals from the crystal suspension.
17. The pH controlled process according to claim 16 , wherein the molar ratio between the at least one additional material and guanine is between 4:1-0.01:1.
18. The pH controlled process according to claim 17 , wherein the acid is selected from the group consisting of HCl, H 2 SO 4 , H 3 PO 4 , HNO 3 , C 6 H 8 O 7 , H 2 CO 3 , H 3 BO 3 , and any combination thereof and the pH of the acidic solution is between 0-3.
19. The pH controlled process according to claim 16 , wherein the base is selected from the group consisting of NaOH, NaHCO 3 , KOH, NH 4 OH, Ca(OH) 2 , and any combination thereof, and the pH of the basic solution is between 12-14.
20. The pH controlled process according to claim 16 , wherein the pH of the filtrate is adjusted by dropwise adding a base or an acid to the filtrate over a period of time of 1-20 minutes, wherein the predetermined pH value is between 10.5-11.5.
21. A temperature controlled process for preparing the synthetic co-crystals according to claim 1 , wherein said process comprises the steps of:
preparing a basic or acidic aqueous solution of guanine and the at least one additional material;
heating the basic or acidic aqueous solution to a predetermined temperature for the predetermined length of time;
inducing co-crystallization by cooling the basic or acidic aqueous solution at a predetermined rate until reaching a predetermined temperature thereby providing a synthetic co-crystal suspension comprising crystals;
allowing the synthetic co-crystal suspension to mature over a predetermined period of time; and
collecting the synthetic co-crystals from the crystal suspension.
22. A pH controlled process for preparing the synthetic co-crystals according to claim 4 , wherein said process comprises the steps of:
preparing a basic or acidic aqueous solution of guanine and the one additional material;
maintaining the basic or acidic aqueous solution at a predetermined temperature range for a predetermined period of time;
filtering the basic or acidic aqueous solution to provide a filtrate;
adjusting the pH of the filtrate by adding a base or an acid to the filtrate over a predefined period of time until a predetermined pH value is obtained, thereby providing a synthetic co-crystal suspension comprising co-crystals;
allowing the synthetic co-crystal suspension to mature over a predetermined period of time; and
collecting the synthetic co-crystals from the crystal suspension.
23. The pH controlled process according to claim 22 , wherein the molar ratio between the one additional material and guanine is between 4:1-0.01:1.
24. The pH controlled process according to claim 22 , wherein the basic or acidic aqueous solution comprises 0.003-0.2M of guanine.
25. The pH controlled process according to claim 22 , wherein the basic or acidic aqueous solution comprises 0.003-0.2M of the one additional material.
26. The pH controlled process according to claim 22 , wherein the acid is selected from the group consisting of HCl, H 2 SO 4 , H 3 PO 4 , HNO 3 , C 6 H 8 O 7 , H 2 CO 3 , H 3 BO 3 , and any combination thereof.
27. The pH controlled process according to claim 22 , wherein the pH of the acidic solution is between 0-3.
28. The pH controlled process according to claim 22 , wherein the base is selected from the group consisting of NaOH, NaHCO 3 , KOH, NH 4 OH, Ca(OH) 2 , and any combination thereof.
29. The pH controlled process according to claim 22 , wherein the pH of the basic solution is between 12-14.
30. The pH controlled process according to claim 22 , wherein the pH of the filtrate is adjusted by dropwise adding a base or an acid to the filtrate over a period of time of 1-20 minutes.
31. The pH controlled process according to claim 22 , wherein the predetermined pH value is between 10.5-11.5.
32. A temperature controlled process for preparing the synthetic co-crystals according to claim 4 , wherein said process comprises the steps of:
preparing a basic or acidic aqueous solution of guanine and the one additional material;
heating the basic or acidic aqueous solution to a predetermined temperature for the predetermined length of time;
inducing co-crystallization by cooling the basic or acidic aqueous solution at a predetermined rate until reaching a predetermined temperature thereby providing a synthetic co-crystal suspension comprising crystals;
allowing the synthetic co-crystal suspension to mature over a predetermined period of time; and
collecting the synthetic co-crystals from the crystal suspension.