On the ground and excited state dipole moments of planar vs. twisted nitroaniline analogues

1991 ◽  
Vol 69 (3) ◽  
pp. 550-557 ◽  
Author(s):  
Hemant K. Sinha ◽  
Keith Yates
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Charge Distribution ◽  
Excited States ◽  
Reasonable Agreement ◽  
Dipole Moments ◽  
Molecular Orbital Calculations ◽  
Adequate Explanation ◽  
Excited State Dipole Moments ◽  
State Charge

Planar and conformationally twisted p-nitroaniline (PNA) and N,N-dimethyl-p-nitroaniline (DMPNA) systems have been subjected to electric field study (electrochromism) to understand their charge transfer characteristics in the ground and excited states. The observed values of ground and excited state dipole moments suggest that twisting of either the donor (D) with respect to the acceptor (A) or vice versa can have a large impact on the resultant charge distribution, particularly on the excited state charge distribution. These observations remarkably support the TICT hypothesis and minimum overlap rule, as proposed by Grabowski et al. Simple molecular orbital calculations provide adequate explanation for the observed changes in the dipole moment and reasonable agreement has been found in each case studied. Key words: electrochromism, dipole moments, charge transfer.

Excited state dipole moments and polarizabilities of some aromatic alkenes and alkynes

1990 ◽  
Vol 68 (9) ◽  
pp. 1507-1513 ◽  
Author(s):  
Hemant K. Sinha ◽  
Paul C. P. Thomson ◽  
Keith Yates
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Excited States ◽  
Experimental Error ◽  
Acid Catalysis ◽  
Dipole Moments ◽  
Excited State Dipole Moments ◽  
Induced Changes ◽  
Excited State Dipole Moment ◽  
Shed Light

Electric field induced changes in the optical absorption spectra (electrochromism) have been used to obtain the excited state dipole moments and polarizabilities of styrene, 2-vinylnaphthalene, 2-naphthylacetylene, and 9-vinylanthracene. Excited state dipole moments of the order of 4–6 debye have been obtained for all these molecules except for 9-vinylanthracene, for which the excited state dipole moment is zero within experimental error. These results support earlier proposals of the involvement of charge transfer excited states in the fast and efficient acid-catalysed photohydration reactions of this type of substrate. 9-Vinylanthracene, on the other hand, under similar conditions reacts differently to give a dimer as the major photoproduct, and its reaction is not subject to acid catalysis. These results shed light on the importance of charge transfer excited states on the efficiency of photohydration reactions. Keywords: electrochromism, excited state, dipole moments, polarizabilities.

Ground and excited state dipole moments of planar vs. twisted p-N,N-(dimethylamino)benzonitrile systems: maximum charge transfer for minimum overlap

1992 ◽  
Vol 70 (7) ◽  
pp. 1932-1938 ◽  
Author(s):  
Hemant K. Sinha ◽  
S. Muralidharan ◽  
Keith Yates
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Degrees Of Freedom ◽  
Theoretical Calculations ◽  
Dipole Moments ◽  
Torsional Angle ◽  
Dimethylamino Group ◽  
Maximum Charge ◽  
Donor Acceptor ◽  
Excited State Dipole Moments

Electric field induced change in the absorption spectrum (electrochromism) has been employed to obtain the ground and excited state dipole moments of planar and sterically hindered (twisted) p-N,N-(dimethylamino)benzonitriles in dioxane solution. These studies support the twisted intramolecular charge transfer (TICT) hypothesis and provide additional insight to the TICT concept. The charge transfer nature of the excited state has been found to directly depend on the torsional angle of the N,N-dimethylamino group with respect to the benzonitrile moiety. It is suggested that solvent coupling is essential to initiate twisting by affecting the intramolecular degrees of freedom and the existence of the highly dipolar excited state is a result of such twisting of the donor–acceptor bond. Theoretical calculations have been performed to explain the observed changes in dipole moment values.

Ground and Excited State Dipole Moments of BADAN and ACRYLODAN Determined from Solvatochromic Shifts of Absorption and Fluorescence Spectra

2001 ◽  
Vol 56 (5) ◽  
pp. 407-411 ◽  
Author(s):  
A. Kawski ◽  
B. Kukliriski ◽  
P. Bojarski
Keyword(s):  
Excited State ◽  
Excited States ◽  
Fluorescent Probes ◽  
Electric Dipole ◽  
Fluorescence Spectra ◽  
Dipole Moments ◽  
Absorption And Fluorescence Spectra ◽  
Electric Dipole Moments ◽  
Solvatochromic Shifts ◽  
Excited State Dipole Moments

Abstract The electric dipole moments in the ground μg, and excited states μe of the fluorescent probes BADAN (6-bromoacetyl-2-dimethylamino-naphthalene) and ACRYLODAN (6-acrylolyl-2-dimethylamino-naphthalene) are determined from the solvatochromic shifts of their absorption and fluorescence spec­tra for two Onsager interaction radii (a = 4.2 and 4.6 Å). The obtained values of μg and μe for BADAN are comparable to those of PRODAN, while for ACRYLODAN they are distinctly greater.

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