1,3,3-Trimethylindolino-6'-nitrobenzopyrylospiran

NitroBIPS is used as a photochromic dye which can be incorporated in poly(vinylalcohol)(PVA) by electro-spinning to form PVA-spiropyran nanofibres. It has photo-responsive behaviour that may be useful in optical data storage applications. It can be used to dope liquid crystal to develop a coloured scattering device that is dual responsive and allows the initiation of electrohydrodynamic instabilities(EHDI). Addition of NitroBIPS can modify the transparency from 100% to 16%, providing a shielding effect which can be used for smart window applications. It may also be used to enhance the adhesion property of polystyrene(PS) on the glass substrate by improving the shear strength by a factor of 7.

1′,3′-Dihydro-1′,3′,3′-trimethyl-6-nitrospiro(2H-1-benzopyran-2,2′-(2H)-indole)(NitroBIPS) is a photochromic biocompatible spiropyran molecule that has six nitro groups positioned at the benzopyran section. It has a colourless leuco spiropyran form(SP) and coloured trans-merocyanine form(MC) that exhibits absorption peaks in the ultraviolet and visible regions respectively. NitroBIPS possesses a higher quantum yield in comparison to other spiropyran molecules and dissolves in a variety of solvents.

This photochromic dye crystallises from absolute EtOH [Hinnen et al. Bull Soc Chim Fr 2066 1968, Ramesh & Labes J Am Chem Soc 109 3228 1987, Berman et al. J Am Chem Soc 81 5607 1959]. [Beilstein 27 III/IV 1460.]