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Charge-transfer complexes of heterocyclics of biological interest—II. Aminopyrazoles
~~~m,&mica Acta. Vol. 47A, No. 11, pp. 1635-KS,1991 F’rintedin Great Britain
0584-a539/91s3.00+0.00 @1991pe@UWtlPtWpk
SHORT NOTE
Charge-transfer complexes of heterocyclics of biological interest-II. Aminopyrazoles (Received 4 January 1991; in final form 18 March 1991; accepted 20 March 1991)
The 1:l CT complexes of the aminopyraxoles l-5 with the acceptors TCNE, DTP and CHL con&m that the aryl-NH group plays an important role in determining the basicity of the aminopjlazoles towards the acceptors. The basic strength of the donors studied decreases as follows: aryl-NH>morpholeno (3)> S-CH, (5). Substitution of the hydrogen atom of the NH group of the heterocyclic ring by a methyl group in 1 and 3a inhibits the electron releasing character of these donors. The results indicated that the aryl-NH as well as the NH of the heterocyclic ring is the most probable donating centre and the interaction in the CT complexes is accordingly a mixture of n--Jc* and z-JC*. A decrease in the electron density on the donor and an increase on the acceptor are visible in the light of the IR spectra of crystalline DTP complexes. The thermodynamic properties of complexes reveal that the CT complexation of the donors with DTP is more exothermic than with TCNE or CHL. The full paper has been deposited with the British Library at Boston Spa, Wethbery, West Yorks, U.K. as Supplementary Publication No. SUP 13033 (15 pages).
Ar-N
AI-N
H
w
H
CN
1 a
Ar -
CsHS
b
Ar=
CsH4-m--CH,
c
Ar = C6H4-p-CH,
d
h
e
AI =
CIH4-p--Cl
f
Ar t
CeHS--CH2
=
2
GH4-p-OCHs
3n R = H 3b R = CHs
TCNE (VItAI 47:11-J
DTF 1635
C?IL
SHORTNATE
1636
Acknowledgements-The authors are deeply indebted to the Alexander von Humbldt Foundation for donation of a Perkin-Elmer Lambda 2 UvlVIS spectrophotometer, and to Professor D. D8pp, Duisburg University (Germany) for measuring the ‘H NMR spectra. Chemistry Departments, Faculty of Science and Faculty of Agriculture, El-Minia University, El-Minia, A. R. Egypt
* Author to whom correspondence
should be addressed.
ALAA A. HASSAN NA~RK. MOHAMED k-USRIAR.kAHIhl ABOUL-FETCIUH E. MOURAD’ SALEHABOUL-FETOUH
0584-a539/91s3.00+0.00 @1991pe@UWtlPtWpk
SHORT NOTE
Charge-transfer complexes of heterocyclics of biological interest-II. Aminopyrazoles (Received 4 January 1991; in final form 18 March 1991; accepted 20 March 1991)
The 1:l CT complexes of the aminopyraxoles l-5 with the acceptors TCNE, DTP and CHL con&m that the aryl-NH group plays an important role in determining the basicity of the aminopjlazoles towards the acceptors. The basic strength of the donors studied decreases as follows: aryl-NH>morpholeno (3)> S-CH, (5). Substitution of the hydrogen atom of the NH group of the heterocyclic ring by a methyl group in 1 and 3a inhibits the electron releasing character of these donors. The results indicated that the aryl-NH as well as the NH of the heterocyclic ring is the most probable donating centre and the interaction in the CT complexes is accordingly a mixture of n--Jc* and z-JC*. A decrease in the electron density on the donor and an increase on the acceptor are visible in the light of the IR spectra of crystalline DTP complexes. The thermodynamic properties of complexes reveal that the CT complexation of the donors with DTP is more exothermic than with TCNE or CHL. The full paper has been deposited with the British Library at Boston Spa, Wethbery, West Yorks, U.K. as Supplementary Publication No. SUP 13033 (15 pages).
Ar-N
AI-N
H
w
H
CN
1 a
Ar -
CsHS
b
Ar=
CsH4-m--CH,
c
Ar = C6H4-p-CH,
d
h
e
AI =
CIH4-p--Cl
f
Ar t
CeHS--CH2
=
2
GH4-p-OCHs
3n R = H 3b R = CHs
TCNE (VItAI 47:11-J
DTF 1635
C?IL
SHORTNATE
1636
Acknowledgements-The authors are deeply indebted to the Alexander von Humbldt Foundation for donation of a Perkin-Elmer Lambda 2 UvlVIS spectrophotometer, and to Professor D. D8pp, Duisburg University (Germany) for measuring the ‘H NMR spectra. Chemistry Departments, Faculty of Science and Faculty of Agriculture, El-Minia University, El-Minia, A. R. Egypt
* Author to whom correspondence
should be addressed.
ALAA A. HASSAN NA~RK. MOHAMED k-USRIAR.kAHIhl ABOUL-FETCIUH E. MOURAD’ SALEHABOUL-FETOUH