ELECTRONIC SPECTROSCOPY IN CONDENSED MEDIA - LOWEST N-PI-STAR TRANSITION OF THE SOLVATED NITRITE ANION

A general formalism developed in earlier publications for treating the electronic spectra of solvated anions is found to successfully described the spectra of the nitrite anion in solvents of differing polarity (H2O, EtOH, CH3CN, DMF). The analysis presented supports the conclusions that the first excited state (1B1) of the solvated nitrite anion is a bound state. The entire width of the spectra can be accounted for via a Frank-Condon progression alone. The predicted vibrational frequencies of the participating bending mode in the aqueous solution are found to be 1074 and 827 cm-1 in the ground (X1A1) and the excited (1B1) states, respectively. These predicted frequencies have been further verified by ab initio calculations which simulate the gas-phase and solvated ion. The force constant for the ground state bending mode is found to be 9.8X10-11 dyne cm. in aqueous solution. The fitting procedure allows us to calculate an inhomogeneous broadening of 383 cm -1 for NO2- in water. These properties have been also calculated for the other solvents (EtOH, CH3CN, and DMF) and trends in the changes of these quantities have been established. © 1979 American Institute of Physics.