EFFECT OF CRYSTALLIZATION WATER
1443
placed in a quartz ampoule with a magnetic stirrer, toluene
3
+
was added, and the Eu PL intensity was measured in
the solid phase at 612 nm (20°C). Then agitation was
switched on and R Al was introduced using a syringe,
3
with Al/Eu ratios of 12, 20, 30, 40. The total volume of
the reaction solution was 10 ml. At certain intervals of
time, the PL from the solid phase was recorded (with the
3
+
stirrer switched off) at 612 nm for Eu and 485 nm for
2+
Eu . PLspectra were measured with a spectrofluorimeter
based on an MDR-23 monochromator and a FEU-39
photomultiplier as a photodetector.
i
On addition of a Bu Al solution to a suspension of the
3
3+
CH in toluene, the red Eu PLdisappears (λ = 612nm)
max
2
+
and there appears a blue Eu PL (λ = 485nm), with
max
its brightness gradually reaching the maximum value
(
2
by approximately 80th minute) (Fig. 1, curves 1 and
3
+
). By this instant of time, the whole amount of Eu is
2+
reduced to Eu . During and after the interaction of the
CH with R Al, the whole amount of europium remains
3
in the solid phase.
i
The reaction of the CH with Bu Al is also accompanied
τ, min
3
i
by vigorous evolution of gaseous Bu H, which points to
3+
Fig. 1. Kinetics of variation of the PL intensity from (1) Eu
dehydration of the europium ion (Fig. 1, curve 3). By the
and (2) Eu2+ and for evolution of (3) BuiH and (4) EtH in the
3
+
i
instant of disappearance of the Eu PL, about 33% Bu H
is released, which corresponds, in terms of crystallization
reaction of EuCl3 ⋅ 6H2O (0.54 mmol) in toluene with (1–3)
i
Bu Al and (4) Et Al. R Al/EuCl ⋅ 6H O = 30, 20°C, λ
=
3
3
3
3
2+
2
ex
+
3
65 nm for Eu3 and 280 nm for Eu . (I) PL intensity, [V(RH)]
i
water that has entered into the reaction with Bu Al [in
accordance with the stoichiometry of reaction (1)], to
removal of two water molecules
3
alkane volume, and (τ) time.
The rate of Eu3+ reduction, estimated by the time in
which the maximum PL intensity is reached, increases
i
i
i
H O + 2 Bu Al → (Bu Al) O + 2Bu H.
(1)
2
3
2
2
i
with the ratio between the starting reagents (Bu Al/
3
EuCl ⋅ 6H O): 80 min (20), 65 min (30), 30 min (40).
3
2
It can be assumed that the observed decrease in the
i
2+
At Bu Al/EuCl ⋅ 6H O ≤ 12, no Eu PL is observed
3
+
3
3
2
intensity of the Eu PL is due to partial dehydration of
(
monitoring time 1 h), because the whole amount of
3+
the Eu ion, which yields compounds characterized by
i
Bu Al is expended under these conditions in the reaction
3+
3
a lower quantum efficiency of the Eu PL because of the
with water and europium is not reduced.
smaller number of water molecules coordinated with this
3
+
It was found that the nature of an aluminum alkyl
strongly affects the time in which the blue Eu2+ PL
appears. For example, in the interaction of the CH with
Et3Al, the PL is recorded much later (in 2 h), compared
ion, compared with the Eu ion contained in the CH.
A similar decrease in the PL intensity has been observed
previously in the interaction of TbCl ⋅ 6H O with R Al
3
2
3
[
2]. In addition, our measurements demonstrated that
i
the PL intensity of anhydrous EuCl (synthesized by the
with the case of Bu Al (in 1.5–2 min). It was found that
3
3
this effect is not due to different reactivities of Eu3
toward aluminum alkyls of varied nature. This conclusion
follows from an analysis of the results of the following
experiments. Into a reactor containing a suspension
of CH (0.54 mmol) in toluene, we introduced Bu Al
(Al : Eu = 12) in order to dehydrate the CH. After the
+
method described in [7]) is an order of magnitude lower
than that for the CH. After 10−12 min of interaction
i
i
between the CH and Bu Al, vigorous evolution of Bu H
3
3
+
almost ceases (Fig. 1, curve 3) and a steep rise in the Eu
i
PL intensity is observed (Fig. 1, curve 2). By this time,
3
3
+
the Eu/H O ratio is less than unity [found by calculating
2
i
i
the amount of water reacted with Bu Al, using the kinetic
evolution of the main amount of Bu H ceased (in ~10min),
3
curve of isobutane evolution (Fig. 1, curve 3)].
the solution was decanted and the remaining solid product
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 82 No. 8 2009