Raman study on para nitroaniline single crystal I: Lattice vibrations

Abstract

Low frequency polarized spectra were investigated from 300 to 30K; but, as accidental depolarization arises at low temperature, study was chiefly made at 300K. External vibrations have been assigned using group theory and the influence of hydrogen bonds on the motions of the molecular layers : &-Bq librations at 41.6-64.8, 83.542.4 and 130 cm-', translations in-plane at 79 and 94, out-of-plane at 144 cm-1, owing to layers. Some infrared bands have been observed and assigned.

Raman study on p‐nitroaniline in channels of the molecular sieve AlPO4–5

“…+ 1 pPQn + * * * n Introducing Eqn (3) into Eqn (2) and keeping in mind that the constant term Pj*O consists of the 2'-component only (the PNA length axis is the 2'-axis), one finds that only those components of the scattering tensor can differ from zero for which at least one coordinate index equals 2'. Because of the CZn symmetry of the individual molecules the totally symmetric vibrations A, will involve the component a,.,, of the scattering tensor only, whereas the B vibrations involve a,.,,.…”

Raman study on para nitroaniline single crystal. II: Internal Vibrations

“…We previously [2] placed the zN0, twisting vibration among the low frequencies, at 53 cm-', t o follow Trueblood et aZ. 's expectations [7].…”

“…We have studied the Raman spectrum of the pNA crystal as a function of temperature from 300 to 30K and in spite of the accidental depolarization appearing at low temperature [2], we used mainly the spectra obtained at 30K since, the lines being sharper, the resolution of the bands is better; as the resolution was not always sufficient, we have taken one spectrum at 5 K but only with polycrystalline pNA.…”

“…In [l] and[2] there was an error in the transcription of two moments of inertia of the pNA. The text should read:Iu = 209 x g cm2, IV = 1035 x g cm2,…”

Espectroscopia vibracional, Raman ressonante e eletrônica de nitroderivados em sistemas conjugados

“…Ao longo da última década houve um grande interesse na síntese de sistemas moleculares push-pull visando atingir valores cada vez mais elevados de β e γ. Dentre esses sistemas destacam-se diversas moléculas insaturadas contendo grupos nitro e uma grande variedade de grupos elétron doadores. A de nitroaromáticos e seus derivados, principalmente da pNA[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] , seja bastante extensa, nota-se a escassez de estudos sistemáticos envolvendo diferentes grupos (D-A) no anel aromático em diferentes posições relativas; e/ou envolvendo a formação de espécies aniônicas derivadas daremoção de próton do grupo elétron doador. Esta escassez de estudos sistemáticos, experimentais e teóricos, diz respeito tanto à espectroscopia eletrônica como vibracional, Raman e infravermelho, e ainda mais criticamente com relação à espectroscopia Raman ressonante.…”