Photoinduced bimolecular electron transfer from aromatic amines to pentafluorophenyl porphyrin combined with ultrafast charge recombination persistence with Marcus inverted region.

The dynamics of photoinduced bimolecular reductive electron transfer between meso-tetrakis(pentafluorophenyl)porphyrin (HFTPP), an acceptor (A), and five aromatic amines (donor (D)) with varying oxidation potentials (aniline (AN), N-methylaniline (MAN), N-ethylaniline (EAN), N,N-dimethylaniline (DMAN) and N,N-diethylaniline (DEAN)) in dichloromethane (DCM) as a solvent as well as in neat donor solvents were investigated by employing nanosecond to femtosecond time-resolved fluorescence spectroscopy and femtosecond time-resolved transient absorption spectroscopy upon S excitation of HFTPP. Systematic studies of time-resolved fluorescence quenching dependent on the donor concentration in the concentration range of 0.01-2 M and finally in neat donor solvents broadly enabled us to determine the electron transfer dynamics in three regimes of electron transfer: stationary or diffusion-controlled electron transfer, non-stationary electron transfer and intrinsic or ultrafast electron transfer.

Synthesis and Spectroscopic Investigation of Diketopyrrolopyrrole - Spiropyran Dyad for Fluorescent Switch Application.

We report the synthesis and characterization of a new fluorescent dyad SP-DPP-SP(9) via efficient palladium-catalyzed Sonogashira coupling of prop-2-yn-1-yl 3-(3',3'dimethyl-6-nitrospiro[chromene-2,2'-indolin]-1'-yl)propanoatespiropyran, SP(8), a well known photochromic accepter, with 3,6-bis(5-bromothiophen-2-yl)-2,5-bis((R)-2-ethylhexyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione, DPP(4), a highly fluorescent donor. Under visible light exposure the SP unit is in a closed hydrophobic form, whereas under UV irradiation it converts to a polar, hydrophilic open form named Merocyanine (MC), which is responsible for functioning of photo-switch application. The photochemistry pertaining to fluorescence switch, 'on/off' behaviour, of model dyad SP-DPP-SP(9) is experimentally analyzed in solution as well as in solid state in polymer matrices by photoluminescence(PL) and absorption spectroscopy.