MODIFIED ISOLONCHOCARPIN AS A PRECURSOR OF AROMATIC O- HETEROCYCLE-BASED PHOTOSENSITIZER

• Main Author: Dwiputra, Bayu
• Format: Final Project
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/72972
• Institution: Institut Teknologi Bandung

Secondary photochemical reaction such as energy transfer from photosensitizers (PS) to other molecules has been utilized by both biological systems and synthetic ones in order to access metastable states that are kinetically unfavoured. The application of PSs in health and energy sector encourages scientists to conduct numerous research on PSs through synthesis, semisynthesis, or isolation of natural products. Synthetic PSs are usually through many reaction purification steps and utilizes transition metals efficient to obtain the required properties. Hence, new methods to obtain PSs are needed that are more efficient and environmentally friendly. One alternative to shorten the synthetic route is to use building blocks that are available in nature such as (-)-isolonchocarpin (1) which can be isolated from Tephrosia vogelii. McMurry reaction towards (-)-isolonchocarpin resulted in overcrowded alkene 2. Modification in the form of bromination of C3 was done towards 2 to produce 3 that spontaneously aromatizes to 4. Photoisomerization of 4 followed by its photocyclication is expected to produce 5 that can potentially be applied as a PS or its precursor. Compound 2 and 4 was obtained with 25,15% and 12,01% yield respectfully. UV- Vis absorption spectrum of 4 have shown two sets of isosbestic points under irradiation with 254 nm UV light, while only one set was observed if 365 nm light was used. It is assumed that the first set of isosbestic points refer to isomerization of 4 from trans to cis, while the second set refers to the photocyclization of cis-4 to 5. Trans-4 was used as a model compound to test computional method using DFT and TD-DFT-TDA with COSMO solvation model. It is found that the transition lines from the calculation overlapped with three peaks that was observed in the experimental spectrum. Based on these results, this method of modification can potentially be used as a more efficient method in order to obtain aromatic O-heterocyclic-based PSs.