Substituent Effect on the Structure and Photophysical Properties of Phenylamino- and Pyridylamino-2,1,3-Benzothiadiazoles

4-Bromo-7-phenylamino-2,1,3-benzothiadiazole (1) and 4-bromo-7-(3-pyridylamino)-2,1,3-benzo thiadiazole (2) are synthesized. Their crystal structure and photophysical properties are studied in comparison with the known phenylamino- and pyridylamino-derivatives of 2,1,3-benzothiadiazole. It is found that the aryl substituent and noncovalent interactions affect the absorption band positions and emission in a solid and a solution. It is shown that under the mechanical action on polycrystalline samples of compounds 1 and 2 a hypsochromic shift of the emission band occurs, which indicates the weakening of noncovalent intermolecular interactions.