# THEORY OF VIBRATIONAL SPECTRA OF MOLECULAR COMPLEXES: SOME INDO CALCULATIONS

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 Title: THEORY OF VIBRATIONAL SPECTRA OF MOLECULAR COMPLEXES: SOME INDO CALCULATIONS Creators: Carreira, L. A.; Person, Willis B. Issue Date: 1970 Publisher: Ohio State University Abstract: Energies of interaction, vibrational frequency shifts, intermolecular vibration frequencies, and infrared intensity changes, all of them resulting from bringing two molecules together to form a one-to-one complex, have been calculated using the Pople-Beveridge-Dobosh INDO approximate quantum-mechanical $treatment,^{1}$ for a number of different complexes” in some different geometrical configurations. Calculations are restricted to the treatment of molecules composed of atoms from the first row of the periodic table, but the calculations for $H_{3}N-F_{2}$, for example, provide a good model for the interactions between amines and $I_{2}$. The extent of charge transfer from $NH_{3}$ to $F_{2}$, for example, has been calculated and the calculated charge distribution compared with that expected from simpler charge transfer theory and from experimental results in $I_{2}$ complexes. The relationship between the extent of charge transfer and the frequency shift of the halogen-halogen stretching vibration, suggested empirically by Friedrich and $Person,^{2}$ has been tested for these model systems. Calculations have been made for model systems including: $NH_{3}$ with $F_{2}$, $NH_{3}$ with $H_{2}$ (two different orientations), $NH_{3}$ with $N_{2}$ (two different orientations), and the water dimer. These results provide a rather complete theoretical model for understanding changes, both in frequency and in intensity, of vibrational spectra of molecules as they interact to form complexes. Description: This work was supported by the National Science Foundation, Research Grants No. GP-8111 and GP-17818. Additional support from the University of Florida Computer Center and the College of Liberal Arts and Sciences is gratefully acknowledged. $^{1}$J. A. Pople, D. I. Beveridge and P. A. Dobosh, J. Chem. Phys., 47, 2026 (1967): CNINDO: CNDO and INDO Molecular Orbital Program, by P. A. Dobosh, Quantum Chemistry Program Exchange, University of Indiana, No. 141. $^{2}$H. B. Friedrich and W. B. Person, J. Chem. Phys., 44, 2161 (1966)."" Author Institution: Department of Chemistry, University of Florida URI: http://hdl.handle.net/1811/8392 Other Identifiers: 1970-D-3