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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 6 (1996), S. 307-311 
    ISSN: 1057-9257
    Keywords: quantum chemical semiempirical calculations ; m-nitrophenol ; polymorphic forms ; hyperpolarisabilities ; electron affinities ; electronic transitions ; spin densities ; hydrogen bonding ; proton transfer ; paramagnetic species ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Energy differences between m-nitrophenol (mNP) molecules in the gas phase and in two crystalline polymorphic forms - the optically non-linear orthorhombic and the centro-symmetric monoclinic form - have been found by the semiempirical all-valence modified INDO method. The calculations were performed for neutral molecules and for possible ions as well as for deprotonated molecules in the three phases. The values obtained for electron affinities, hyperpolarisabilities, electronic transition energies and spin desities on atoms in open-shell structures indicate that paramagnetic species are most favoured in the orthorhombic polymorph. This tendency corroborates our ESR results on the generation of unpaired spins by near-infrared excitation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 375-381 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polarized IR spectra in the 20-400 cm-1 region and Raman spectra in the 0-200 cm-1 region were measured at room and liquid nitrogen temperature for crystals of two phases of m-nitrophenol (mNPh). The Raman spectra of the orthorhombic mNPh crystal were measured as a function of temperature from room temperature up to 360 K for spectroscopic evidence of a phase transition. The symmetries of lattice and low-frequency internal vibrations are discussed. The influence of decreasing temperature on the bands produced by the hydrogen bridge vibration is presented. The role of the hydrogen bond in the mechanism of the phase transition and the metastability of the monoclinic phase is discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polarized Raman and IR spectra of m-nitrophenol (mNPh) crystals in two modifications and of mNPh and its deuterated analogue powders in a KBr pellet, nujol mull and CCl4 solution have been measured in the region 200-4000 cm-1. The results are discussed and compared with earlier published data for α-resorcinol, m-nitroaniline and m-aminophenol (mAPh). For the last compound new results, i.e. the IR spectra of the deuterated analogue, are presented, and reinterpretation of some previous assignments is proposed. The assignments of the bands in the mNPh spectra and the re-examination of the mAPh spectra were facilitated by ordering the spectra of the four compounds into two classes exhibiting common features.It has been found that the differences between the spectra of two phases of the mNPh crystal are small and reflect the differences in interactions between the chains of molecules linked by hydrogen bonds. These interactions perturb particularly the NO2 group vibrations which cannot be treated using the oriented gas model. On the basis of INDO/CI calculations of electronic absorption spectra vibronic couplings in the IR and Raman spectra of the mNPh crystals have been proposed to account for many intensity enhancements.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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