342
Y. Kumar et a!. / Luminescence properties of pesticides, II
NMR (CDCI3) 7.77 (s, 6H, tolyl metlsyls), 7.13 (d, 3H, 5Hz. N—CH3), 2.80—3.22
(multiplet, 3H, aromatic protons), UV (ethanol) Xmax 268 nm (a
274 mu (a 534.0 ~/mol cm).
Azak was also prepared by the technique described in ref. [2]
=
561.4 ~/niol cm),
In this case the
=
.
2.6-di-t-butyl-4-methyl phenol was condensed with methyl isocyanate. Crude yield
of the reaction was 90%. Its spectral properties are as follows: m.p. 200— 20l°C~
m.s.. M+ 277; NMR (CDCI3) r8.64 (s, l8H, 2x0-t-butyls), 7.69 (s, 3H, p—Me), 7.12
(d, 3H, 5Hz, NHMe), 2.87 (s. 3H, aromatic), i.e. (CHCI3) ~max 3460 c m ’ (N —H),
1740 c m ~ (C
=
0); UV (ethanol) Xmax 276 nm (a
=
263 ~/mol cm), 268 nm (a
=
300 Q/mol cm).
Dazak was prepared from 2,6-di-t-butylphenol and methyl isocyanate. The crude
yield of the reaction was 100%. The spectral properties of dazak are as follows:
m.p. 199°C;m.s., M3 263, NMR (CDC13) 7-8.61 (s, 18H, 2x0-t-butyls), 7.08 (d, 3H,
5Hz, N-HMe), 2.5—2.8 (niultiplet, 3H, aromatic protons); IR (CHC13)iJmax 3460
c m t (N—H), 1730 c m ’ (C
=
0); UV (ethanol) Amax 261 nm (a
=
188 Q/mol cm).
EPA used in phosphorescence studies was obtained from American Instrument
Co., Silverspring, Maryland. 3-Methyl pentane was obtained from Matheson, Cole-
man & Bell Co., Baton Rouge, Louisiana. tsopropyl alcohol was obtained from J.T.
Baker Chemical Co., Philipsburg, New Jersey and was GC-spectrophotometric quali-
ty. It was used without further purification.
2.2. Apparatus
All emission and excitation measurements were carried out on a fully compensat-
ed Aminco—Bowman Spectrophotometer. The block diagram for this apparatus is
given in the preceding paper as is the block diagram for the apparatus used to obtain
decay curves.
3. Results and discussion
3.1. Excitation and emission spectra
Typical phosphorescence excitation and emission spectra are shown in fig. I. All
spectra were recorded at 77 K with and without the use of a rotating shutter (phos-
phoroscope). The use of the phosphoroscope resulted in a decrease in first and sec-
ond order scattered light; no other difference was observed. This is to be expected
since fluorescence emission was not observed for any of the compounds examined in
this study, and the phosphoroscope serves only to differentiate between emissions
of long and of short duration.
The phosphorescence spectrum consisted in each case of a broad, structureless
band with a maximum centered betw een 420 and 450 nm. Details of the phospho-
rescence emission and excitation in the three solvents examined are given in table 1.