CHARGE DENSITY ANALYSIS ON MODIFIED COUMARINS: SECOND HARMONIC GENERATION

P. Munshi and T. N. Guru Row

Indian Institute of Science, Solid State and Structural Chemistry Unit, C. V. Raman Avenue, BANGALORE, 560012 India (munshi@sscu.iisc.ernet.in).

Coumarins have been used in several areas of synthetic, medicinal and photochemistry. The several substituted coumarin derivatives are used in the dye industry. Thio-substituted coumarins depict state dependent variation in static dipole moment and crystallize in noncentrosymmetric space groups, a characteristic requirement for second harmonic generation (SHG). Crystal and molecular structure of (I) 2H-chromene-2-thione[1] and (II) 2H-thiochromene-2-one[2] have been determined to belong to the space group P2(1)2(1)2(1) and Pc respectively and the preliminary SHG measurements from powder samples using Perry’s method depict high activity as a NLO material. High resolution X-ray diffraction data has been collected at 90K on a Bruker AXS SMART APEX system, in order to analyze the presence of sulfur in place of oxygen (the case of coumarin) and the consequent electron density distributions have been analyzed using space partitioning based on the topology of the total electron density. The results from experimental charge density analysis of I [3, 4] and II have been compared with the theoretical calculation performed at different level using GAUSSIAN98. The subsequent calculations of one-electron properties have been performed using both XD and MOLLY packages.

I II

References

1 Munshi, P. and Guru Row, T. N. (2001) Acta Cryst. E57, o1175-o1176.

2 Munshi, P. and Guru Row, T. N. (2002) Acta Cryst. E58, o353-o354.

3 Munshi, P. and Guru Row, T. N. (2002) Acta Cryst. B58, 1011-1017.

4 Munshi, P. and Guru Row, T. N. (2003) Acta Cryst. B59, 159.