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Updated: Jul 14, 2026

Magnetic Tweezers for the Measurement of Twist and Torque
Published on: May 19, 2014
Charge-transfer-induced twisting of the nitro group
Jahur A Mondal1, Moloy Sarkar, Anunay Samanta
1Radiation & Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
Abstract:
Excited-state relaxation dynamics of 2-amino-7-nitrofluorene (ANF) and 2-dimethylamino-7-nitrofluorene (DMANF) has been investigated in two aprotic solvents, namely acetonitrile and DMSO using femtosecond transient absorption spectroscopic technique. Following photoexcitation to the highly dipolar excited singlet (S1) state, ANF and DMANF undergo mainly two concomitant relaxation processes, namely dipolar solvation and conformational relaxation via twisting of the nitro group to an orthogonal configuration with respect to the aromatic plane. Viscosity dependence of the relaxation dynamics of the S1 states of both ANF and DMANF suggests no involvement of the twisting motion of the amino or dimethylamino group in the charge-transfer process. The twisting of the nitro group is found to be a friction affected diffusive motion, which does not associate with any further charge transfer. The results presented in this paper resolve experimentally the dynamics of the twisting motion of the nitro group for the first time.
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