In:
The Journal of Chemical Physics, AIP Publishing, Vol. 45, No. 11 ( 1966-12-01), p. 4181-4189
Abstract:
The electron spin resonance spectra of vanadyl acetylacetonate (VOacac2) and a number of its adducts have been examined in benzene solution at ambient temperatures. It is found that the magnitude of the vanadium nuclear hyperfine splitting constant decreases from 108.19 to 105.3 G as amine adducts are formed, while the g value increases from 1.9695 to 1.9699. The anisotropies of the axially symmetric g and hyperfine tensors, Δg and b, and the rotational correlation time τR have been calculated from the linewidths of VOacac2, VOacac2·pyridine, and VOacac2·piperidine in benzene solution. The correlation time increases from 2.4×10−11 to 3.0×10−11 sec, |b| increases from 2.1×109 to 2.3×109 rad/sec, and |Δg| decreases from 0.034 to 0.029 on coordination of pyridine. Although the g values calculated from the electronic spectra using the theories of Ballhausen and Gray or Kivelson and Lee decrease slightly on adduct formation rather than increase as observed experimentally, the calculated anisotropies Δg follow the experimental trend. Analysis of the line broadening observed for mixtures of VOacac2 and an adduct allows the estimation of the rate of exchange of amine between the adduct and bulk solvent. Line shapes for the −72 line have been calculated for the intermediate exchange-rate region and compared with experimental spectra. For the reaction VOacac2+pyridine⇌ lim krkfVOacac2·pyridine,kr=1.3×107 sec−1, kf=1.0×109M−1·sec−1. For the similar reaction with piperdine, kr≤2×106 sec−1, kf≤2.8×109M−1·sec−1; and for 2-picoline, kr=7×107 sec−1, kf=5×107M−1 sec−1.
Type of Medium:
Online Resource
ISSN:
0021-9606
,
1089-7690
Language:
English
Publisher:
AIP Publishing
Publication Date:
1966
detail.hit.zdb_id:
3113-6
detail.hit.zdb_id:
1473050-9
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