The infrared spectra of chelate compounds—II1

Talanta, 1963, Vol. 10, pp. 961 to 966. Pergamon Press Ltd. Printed in Northern Ireland

THE INFRARED

SPECTRA OF CHELATE COMPOUNDS-II*

A STUDY OF SOME BIVALENT METAL CHELATE COMPOUNDS OF 84lYDROXYQUINOLINE IN THE REGION 625 TO 250 cm-l R. J. Department

MAGEE?

and LOUISGORDON

of Chemistry, Case Institute of Technology Cleveland 6, Ohio, U.S.A.

(Received 11 November 1962. Accepted 18 March 1963) investigationof the infrared spectra in the region 625-250 cm-l of the complexes of copper, zinc, manganese, magnesium and

Summary-An

calcium with 8-hydroxyquinoline has been carried out. The spectra are simple, but, despite their simplicity, they differ from one another, both in the number of peaks and the relative positions of corresponding peaks. Possible analytical applications of the spectra in this region are discussed. infrared spectra in the region 5OOCk625 cm-l of some metal chelates of 8-hydroxyquinoline have already been rep0rted.l Investigations of metal chelates in the region 625-250 cm-l are few in number. Dismukes et aL2 have recorded the infrared spectra of some metal-acetylacetonate complexes between 700 and 350 cm-l, and Lane et aL3 have recently obtained the infrared spectra of 2-(2-pyridyl)-imidazoline, 2-(2-pyridyl)-benzimidazole, 2-(o-hydroxyphenyl)-imidazoline, 2-(o-hydroxyphenyl)-benzimidazole, and their metal chelates in Hbwever, no investigation of 8-hydroxythe region between 5000 and 300 cm-l. quinoline and its metal chelates in this low frequency range has been reported. THE

EXPERIMENTAL Materia Is The metal oxinates used in the investigation were prepared, as far as possible, by the method of precipitation from homogeneous solution;4*6 these were copper: zinc,’ manganese: magnesium6 and calcium.6 Potassium bromide discs were prepared using a Perkin Elmer die in conjunction with an “Elmes” hydraulic press capable of delivering 23,000 pounds total load on a ram 3 inches in diameter. Before use, the KBr, which was of spectroscopic grade, was dried at 150” for 24 hr, and was ground to pass 100 mesh. Measurement of the infrared spectra All spectra were recorded on a Perkin-Elmer, Model 21, Spectrophotometer with a CsBr prism; resolution was 1000, response 12, and speed 32. The spectra obtained for I-hydroxyquinoline and the five metal chelates are shown in Figs. l-6. RESULTS

AND

DISCUSSION

The principal absorption peaks observed in the spectra of 8-hydroxyquinoline and the metal oxinates (Figs. l-6), recorded in ,u except where stated, are given below: 8-Hydroxyquinoline 15.71, 174, Part I-see t Permanent Ireland. l

18.39, 2040, ref. 1. address:

21.3, 21.52, 23.62, 33.00.

Department

of Chemistry, 961

The Queen’s University,

Belfast, Northern

MAGEE

R. J.

962

0

I

15

17

19

I

21

I

,

^c3 25

and LOUIS GORDON

,

27

!

i9

31

1

33

Wovelenqth. FIG.

1.-The

,

35

,

37

,

39

p

infrared spectrum of copper oxinate in the region 1S-40 ,u. (2 mg of copper oxinate in 400 mg of KBr.)

100

i;; E

;

20 0.

I

I5

I

17

I

I9

I

21

I 23

11 25 27

11 29

31

Wavelength, FIG.

2.-The

,

0

I5

01

/ 15

I

I

I

I

I

I

I

I

I

19

21

23

25

27

29

31

33

4.-The

,

35

I

,

37

39

p

infrared spectrum of manganese oxinate in the region 15-40 ,u. (2 mg of manganese oxinate in 400 mg of KBr.)

1

17

I

19

I

21

I

23

I,

25

27

II,

29

Wovelength. FIG.

’ 39

p

17

J.--The

1 37

infrared spectrum of zinc oxinate in the region 15-40 p. (2 mg of zinc oxinate in 400 mg of KBr.)

Wovelength, FIG.

11 33 35

31

33

I

35

I,

37

39

p

infrared spectrum of magnesium oxinate in the region 15-40 p. (2 mg of magnesium oxinate in 400 mg of KBr.)

1

963

Infrared spectra of bivalent metal S-hydroxy-quinolates

I

0 ;..

I5

,,I,,,,,, 17

19

21

23

25

27

29

31

33

Wavelength,

FIG. 5.-The

I

I

37

39

I

p

infrared spectrum of calcium oxinate in the region 15-40 .LL (2 mg of calcium oxinate in 400 mg of KBr.)

Wavelength,

FIG. 6.-The

I 35

p

infrared spectrum of S-hydroxyquinoline in the region 1S-40 /L. (2 mg of Shydroxyquinoline in 400 mg of KBr.)

Copper oxina te 15.53, 15.82, 17.15, 19.15 (522.19 cmP1), 24.64 (405.84 cm-r), Zinc oxinate 15.41, 16.60, 17.68, 20.11 (497.26 cm-l), Manganese

24.70 (404.86 cm-l).

oxinate

15.49, 16.62, 17.10, 17.80, 20.05 (498.75 cm-‘), Magnesium

30.82.

26.86 (372.30 cm-l),

30.88.

20.65 (484.26 cm-l),

26.12 (382.85

oxinate

15.47, 16.40, 17.05, 17.76, 19.55 (511.51 cm-r), cm-l), 31.68, 32.99, 34.50. Calcium oxinate

15.30, 16.74, 17.75, 19.95 (501.25 cm-l), 20.47 (488.52 cm-l), 23.25, 26.78 (373.41 cm-‘). The spectra (of 8-hydroxyquinoline and the metal chelates) in the region examined are quite simple, in contrast to those taken at higher frequency.l In the caesium bromide region, i.e., the region of the investigation, absorption may be caused by internal vibrations, torsional oscillations8 of water in the sample, or lattice vibrations, although these last are not likely above 300 cm-‘. Miller et aZ.8 point out that where water of crystallisation exists in a sample, rotations become hindered and are better described as torsional oscillations. These oscillations produce

R. J. MAGEE and LOUIS GORDON

964

absorption in the caesium bromide region. Water can, however, cause difficulty in this region and often produces peaks which are broad. The spectra of the metal chelates, despite their simplicity, differ markedly from one another, both in the number of peaks and the relative positions of corresponding peaks. They also differ from 8-hydroxyquinoline itself. Perhaps the most interesting peak is that which occurs in the region around 19-20 ,u, or more specifically, copper

I 0

I

0.5

I

Weight

FIG. 7.-Optical

I

I.0

I.5 of

I

2.0

oxlnate.

I

I

2.5

3.0

z

mg

densities plotted against weight of copper oxinate.

(19.15 ,LJU;522.19 cm-r); zinc (20.11 ,u; 497.26 cm-r);5 manganese (20.05 ,u; 498.75 cm-r); magnesium (19.55 ,LLU;511.51 cm-l), and calcium (19.95 ,u; 501.25 cm-l or 20.47 ,LL; 488.52 cm-l). The peak in this region occurs in all of the metal chelates but not in the spectrum of 8-hydroxyquinoline. The peaks for calcium at 26.78 ,u (373.41 cm-l), for magnesium at 26.12 ,U (382.85 cm-l) and for manganese at 26.86 ,u (372.30 cm-‘) are broad. They do not occur in the spectra of copper and zinc. These peaks possibly represent water of crystallisation.

Analytical applications The infrared spectra in the region under investigation are much simpler than those obtained in the region 5000-625 cm- l.l Despite their simplicity, however, considerable differences occur between the spectra of the individual metal oxinates (Fig. l-6). These differences are such that qualitative analysis for the metals may be carried out using the spectra as a basis. To investigate the quantitative significance of the technique the peak at 19.15 ,u or 522.19 cm-l in the copper oxinate spectrum was examined. Potassium bromide discs were prepared by the procedure outlined elsewhere,l and the optical densities for different amounts of copper oxinates were determined. In Fig. 7 the optical densities obtained are plotted against the weights of oxinate taken. It can be seen that the points lie on a straight line. The actual peaks for three different amounts, 0.5, 1.0 and 2.0 mg of copper oxinate are shown in Fig. 8.

Infrared spectra of bivalent metal 8-hydroxy-quinolates .\”

965

100 80-

8 6 F E : 0 +

6040-

_ (0)

ZO-

60 -

Wovelength FIG.

8.--The

p

peaks for three different amounts of copper oxinate, in 400 mg of KBr: (a) 0.5 mg; (b) l.Omg; (c) 2.0 mg.

It is clear that the infrared technique in the range 625-250 cm-l for the quantitative determination of elements by means of their work detailed analytical investigations were not carried out, but a lytical study is considered to be worthwhile. It is proposed to carry and the results will be reported later.

has potentialities oxinates. In this quantitative anaout such a study

Acknawled’emen~s-The authors acknowledge the partial assistance of the United States Atomic Energy Commission in supporting the investigation described herein under Contract AT(l l-1)-582. Thanks are also due to the Research Department for use of the Model 21 spectrophotometer.

of the Union Carbide Co., Parma, Ohio, U.S.A.,

Zusammenfassung-Eine Untersuchung der Oxinate von Cu, Zn, Mn, Mg und Ca im IR-Bereich (6255250 cm-r) wurde durchgefiihrt. Die Spektren sind einfach, unterscheiden sich aber trotzdem voneinander. Sowohl die Anzahl als such die Lage der Spitzen ist verschieden. Die Moglichkeiten einer analytischen Anwendung der Methode wurden diskutiert. Resume-Une recherche sur les spectres infra-rouges des chelates de l’hydroxy-8-quinoltine et des metaux suivants (cuivre, zinc, manganese, magnesium, calcium) a tte effect&e dans les regions 250-625 cm-‘. Les spectres obtenus sont simples, mais malgre leur simplicite, ils different sensiblement a la fois par le nombre des pits et la position relative de ces pits. On presente une discussion des possibilites d’application de ces spectres a l’analyse.

966

R. J. MAGEE and LOUIS GORDON REFERENCES

1 R. J. Magee and L. Gordon, T&n@ 1963, 10,851. 2 J. P. Dismukes, L. H. Jones and J. C. Bailar, Jr., J. P&v. Chem., 1961, 65, 792. 3 T. J. Lane, I. Nakagawa, J. L. Walter and A. J. Kandathal, Znorg. Chem., 1962, 1,267. 4 L. Gordon, M. L. Salutsky, and H. H. Willard, Precipitation from Homogeneous Solution. J. Wiley and Sons, Inc., New York, 1959. 5 R. G. W. Hollingshead, Oxine and Its Derivatives. Butterworths, London, 1954, Vols. I and II. 6 E. D. Salesin and L. Gordon, Talunta, 1960, 4, 75. 7 J. P. Jones, 0. E. Hileman, and L. Gordon, Talunta, 1963, 10,111. * F. A. Miller, G. L. Carlson, F. F. Bentley and W. H. Jones, Spectrochim. Acta, 1960, 16, 135.