Theoretical Chemistry Accounts

, 131:1297

On the electronic structure of the diazomethane molecule

Regular Article

DOI: 10.1007/s00214-012-1297-5

Cite this article as:
Barbosa, A.G.H. & Monteiro, J.G.S. Theor Chem Acc (2012) 131: 1297. doi:10.1007/s00214-012-1297-5


The electronic structure and chemical bonding in the diazomethane molecule are investigated using full-valence generalized valence bond (GVB) methods. We point out that an ab initio-based bonding model must correspond directly to a wave function that yields at least qualitatively corrects values for the structural parameters of a molecule, that is, molecular geometry, vibrational frequencies, and dipole moment. However, in the case of diazomethane, when trying to emulate the bonding models proposed in the literature through full-valence GVB wave functions, we found out that all of them are directly associated with optimized molecular geometries that are saddle points in the molecular potential energy surface. This spurious behavior is corrected by a multiconfiguration–self-consistent field (MCSCF) wave function that incorporates an enlarged “pi-like” active space enabling a complete active space self-consistent field (CASSCF) block, with more active orbitals than electrons, together with a “sigma-like” generalized valence bond with restricted configuration interaction (GVB-RCI) block. With this wave function, we are able to generate the best calculated set of harmonic frequencies to date for the diazomethane molecule. The physical effects that are important for the correct description of its electronic and vibrational structure are then discussed using a series of MCSCF wave functions. This result leads to a decomposition of the electronic wave function into diabatic GVB-RCI chemical structures along the CH2 wagging mode illustrating the necessity to understand the chemical bonding in this molecule as a superposition of bonding patterns. Some structural properties of diazomethane and diazocompounds are then successfully analyzed using our model.


Diazomethane Chemical bonding Generalized valence bond Vibrational spectra 

Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • André G. H. Barbosa
    • 1
  • João G. S. Monteiro
    • 1
  1. 1.Instituto de QuímicaUniversidade Federal FluminenseNiteróiBrazil

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