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The Electronic Structures of 4‐Substituted 3,5‐Dihydro‐4 H ‐pyrazoles and 5‐Substituted 1,4‐Dihydro‐5 H ‐tetrazoles
Author(s) -
Gleiter Rolf,
Veszprémi Tamás,
Quast Helmut
Publication year - 1989
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19891220530
Subject(s) - chemistry , mndo , cndo/2 , ionization energy , ab initio , spectral line , crystallography , ionization , computational chemistry , molecule , organic chemistry , physics , ion , astronomy
The He( I ) photoelectron spectra of 4‐oxo‐ ( 1 ), 4‐methylimino‐ ( 2 ), 4‐thioxo‐ ( 3 ), and 4‐hydrazono‐3,3,5,5‐tetramethyl‐3,5‐dihydro‐4 H ‐pyrazole ( 4 ) as well as 5‐oxo‐ ( 7 ), 5‐imino‐ ( 8 ), and 5‐thioxo‐1,4‐dimethyl‐1,4‐dihydro‐5 H ‐tetrazole ( 9 ) have been recorded. The assignment of the first PE bands is based on the comparison with the PE spectra of compounds of similar structures and the results of MO calculations (Hartree Fock ab initio method, MNDO and HAM/3). The investigations reveal for 1 – 4 that the first PE band is due to the ionization from the n_ orbital localized at the azo group. For 7 – 9 , the first band is due to ionization from a π MO of b 1 symmetry. While the energy of the first PE band of 1 – 4 varies only sligthly, that of 7 – 9 changes strongly. The UV/VIS spectra of 1 – 4 and 7 – 9 are interpreted on the basis of CNDO/S‐CI calculations. The first band in the UV/VIS spectrum of 1 , 2 , and 4 is assigned to a π*←n_ transition of the azo group; for 3 , the first band is due to a π*← s transition localized at the CS group. The comparison between experiment and calculation suggests to assign the first UV band of 7 – 9 to a π*←π transition.