JP3059247B2 - Sterically hindered 1,3-diphenyl-2-pyrazoline derivatives, process for their preparation and scintillators comprising them - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the formula:

[0002]

Embedded image

Sterically hindered 1,3-diphenyl-2-pyrazolines of the formula wherein R ₁ represents an electron donor substituent and R ₂ represents a CH ₃ or OCH ₃ — group or an H atom. -For derivatives. The invention further relates to this derivative and to a scintillator comprising it.

[0004]

2. Description of the Related Art 1,3-Diphenyl-2-pyrazoline-
Derivatives and optical brighteners and their use as scintillators are known from DE-A 25 31 495. In particular from this document, derivatives are known which have a mesityl group at the 3-position of the pyrazoline ring and a phenyl group substituted at the 1-position of the pyrazoline ring. A steric hindrance is formed in the molecule by the mesityl group.

A phenyl group is present at both ortho positions (2 ',
6 ') is unsubstituted or contains a methyl- or methoxy substituent. Further, a phenyl group is defined to contain an electron acceptor substituent at the p-position (4 ').
A further definition includes methyl or methoxy substituents in the ortho position (2 ', 6') and additionally phenyl groups having substituents in the 4'- and 5'-positions having electron acceptor activity.

[0006] In addition to the above-mentioned literature, a production method in which equivalents of phenylvinylketone and phenylhydrazine are reacted is known.

[0007] Such 1,3-diphenylpyrazoline derivatives exhibit relatively high Stokes transitions in the range up to 130 nm. The Stokes transition Δλ _includes the difference between the fluorescence-maximum value λ _E.max and the absorption-minimum value λ _A.max .

This derivative is used as a scintillator substance in solutions and solid polymers, and because it emits fluorescent light which is distinctly different from light having a wavelength which is itself absorbed from the substance. It is also suitable for use in detecting ionized light.

[0009] Increasing the concentration of scintillating substance in the solution extends the wavelength range on the one hand that emits fluorescent light and on the other hand reabsorbs light, where both ranges begin to overlap. This reduces the intensity of the fluorescent light.

For sensitive measurements of elementary particles or ionizing radiation, relatively high concentrations of scintillator substances (> 10 ⁻² M) are often required, from which the described disadvantages arise.

If, despite the high concentration of scintillator material required, the Stokes transition of the scintillator becomes larger, the transmission in the overlapping region of the absorption and fluorescence spectra increases.

[0012]

The object of the present invention is therefore to provide 1,3-diphenyl-2-pyrazolin-derivatives which exhibit a still higher Stokes transition compared to known derivatives.

[0013]

The derivatives defined at the outset have now been found.

Surprisingly, the 1,3-diphenyl-pyrazoline derivative is at the 4'-position and the phenyl group at the 1-position does not have a substituent having an electron acceptor function, but has a function as an electron donor. It has been shown that a particularly high Stokes transition is achieved when the substituent is contained.

The substituent having an electron donor action is, in particular, a group
_{N (CH 3) 2, -NH} 2, -OH, -OCH 3, -CH 3
And -C (CH _{3) 3.}

The highest value of the Stokes transition is obtained when the phenyl group in the 1-position additionally has a methyl- or methoxy substituent in its ortho position. This pyrazoline compound is particularly strongly sterically hindered.

This value of the Stokes transition is further enhanced by the introduction of an electron donor at the 4'-position.

With the 1,3-diphenylpyrazoline derivatives according to the invention, the wavelength ranges of the fluorescence emission and absorption are even further separated from one another, so that the overlap only occurs at high concentrations of the scintillator substance in the solution. The fluorescence-quantum yield and the fluorescence decay time remain the advantageous ranges of the known derivatives. The derivatives according to the invention are therefore particularly suitable as scintillators, for example in large-volume chambers with aromatic solvents or with polymeric scintillator fibers.

According to the present invention, mesityl vinyl ketone is
The derivatives defined at the outset are prepared by reacting with a hydrazine derivative containing the desired 1-position phenyl group as a substituent. The five rings of the pyrazoline are composed of vinylketone- and hydrazine-groups.

The synthesis of the diphenylpyrazoline derivative according to the invention is carried out as follows.

Mesityl vinyl ketone (J. Amer. C)
hem. Soc. 62, 2088-91 (1940)
0.3 mol and 0.35 mol of the corresponding hydrazine-hydrochloride in 500 ml of ethanol and 10 ml of water.
Add an equivalent amount of NaOH in 0 ml of the mixture and boil under reflux for 4-6 hours. The reaction is controlled by thin layer chromatography. During the formation of the batch, the reaction products usually crystallize out and are separated off by filtration. Further reaction products are obtained from the mother liquor by evaporation. The product is washed with water to remove NaCl and then simultaneously with the use of activated carbon,
Purify by two recrystallizations from ethanol. The product crystals are pure white or colorless. Yield 50-60%
It is.

The photophysical data of the novel and two 1-phenyl-3-methyl-2-pyrazolin compounds according to the invention, known in the table, are contrasted with one another.

The dye was either dissolved in toluene (T) or bound in polystyrene (PS).

The compounds I in the table are described in the publications mentioned at the outset. Compound II is 4 'with compound I
-Position electron acceptor is different. Compounds III and IV are occupied by the electron donor according to the invention in the 4'-position.

The quantum yield then relates to the oxygen-containing toluene solution. The quantum yields described in the publications mentioned at the outset relate to oxygen-free solutions.

Compound I is the same as I, except that CH _{3-at the} 4'-position is
Depends on the group. The CH ₃ -group represents only a weak electron donor. Still, the Stokes transition value is 130nm
To 139 nm (solvent toluene).

Compound IV is the same as I, except that OCH _3-
Depends on the group.

The OCH ₃ -group is a stronger electron donor than the CH ₃ -group. With the OCH ₃ -group the Stokes transition is even more strongly enhanced to a value of 152 nm (solvent toluene).

In compound II, starting from compound I,
An electron acceptor is introduced at the 4'-position. The electron acceptor is described in the German Offenlegungsschrift No. 2531495 mentioned at the outset.
It has been proposed in advance by the specification.

[0030]

As is evident from a comparison of both listed compounds, the electron acceptor causes a clear decrease in the Stokes transition at this position.

The model calculations show that starting from a pyrazoline compound in which the phenyl group at the 1-position in the ortho-position contains a methyl or methoxy substituent, an electron donor is introduced in the same way at the 4'-position. This indicates that the Stokes transition increases as well.

The pyrazoline compounds in which the highest value of the Stokes transition is selected, therefore the electron donor in which the substituent R ₂ represents a methyl or methoxy group and which has as high an electron donor action as the substituent R ₁ Expected to.

[0033]

[Table 1]

The symbols in the table represent the following: Smp. : Maximum melting point (° C) λ _A.max : Maximum absorbance (nm) λ _E.max : Maximum fluorescence (nm) Δλ: Stokes transition (nm) Q _F : Quantum yield for oxygen-containing solution (dimensionless) τ : Fluorescence decay time (ns) T: Toluol PS: Polystyrene

Continuation of front page (56) References JP-A-52-10272 (JP, A) CERN [Rep. ] CERN 90-10, Proc. -Large Hadron on Collider Workshop, Vol. 3, p. 255-260 (1990) (58) Field surveyed (Int. Cl. ⁷ , DB name) C07D 231/06 C09K 11/06 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. The formula: embedded image Wherein the substituent R ₁ is an electron donor substituent and R ₂ is CH ₃
Or an OCH ₃ -group or an H-atom]], sterically hindered 1,3-diphenyl-2-pyrazoline derivatives. 2. A mesityl vinyl ketone having the formula: The method for producing a derivative according to claim 1, wherein the derivative is reacted with a hydrazine derivative. 3. A scintillator having the composition according to claim 1.