Nov., 1946
MAGNETIC PROPERTIES [CONTRIBUTION OF THE
2267
OF OXYGEN-CARRYING S Y N T H E T I C C H E L A T E S
DEPARTMENT OF CHEMISTRY,
UNIVERSITY OF CALIFORNIA]
The Oxygen-carrying Synthetic Chelate Compounds. IV. Magnetic Properties' BY M. CALVIN AND C. H. BARKELEW'~ In connection with the investigation of the oxygen-carriers, we have studied the magnetic susceptibility of a number of transition group chelates. The measurements may be grouped into three classes, which will be discussed separately : A, susceptibilities at room temperature; B, temperature dependence; and C, susceptibility as a function of fraction oxygenation. The chelates fall into three general types
HC=N
I
H I1
be described at this point. Earlier workers3.'J have prepared and measured the susceptibilities of a few of these and similar compounds. Our results for the same compounds are in substantial agreement, with a single exception. The susceptibilities were measured using a Gouy balance. The samples were ground in an agate mortar and packed uniformly into a calibrated cylindrical glass tube. The force exerted by a magnetic field on the tube was found with a balance capable of weighing to 0.02 mg. The field was calibrated a t several current strengths with distilled water, and twice recrystallized copper sulfate pentahydrate. Fields of 5,000 to 12,000 gauss were used, and each sample was measured in a t least three field strengths, to detect and correct for any ferromagnetic impurities. In a number of cases, principally among the iron compounds, i t was necessary to fill the tubes in an inert atmosphere to prevent oxidation. The following tables, arranged by metal, give the susceptibilities measured in this laboratory. All values are molal susceptibility at 25", unless otherwise stated, and include Pascal's correction for the diamagnetism of the molecule. TABLE I
R
R
I11
Two cases were of especial interest, and will be referred to so frequently that abbreviations were adopted. Abbreviations
Case I Case I1
n =2
n =3
Sal-En Sal-prtr
Included also are derivatives of salicylaldehyde itself, crystalline solvates of a number of compounds represented by the above structures, plus a small number of compounds not included with above generalization. The compounds were synthesized by well-known techniques, described by Pfeifferlb; preparation of new compounds will be discussed in a paper soon to be published,2 and their preparations will not (1) The work herein reported was carried out in part under a Contract (OEMsr-279) between the National Defense Research Committee and the University of California. (la) Present address: Shell Development Co., San Francisco, Calif. ( l b ) P. Pfei5er and co-workers, Ann.. 603, 84 (1933); J firakl. Chcm.. 140, 29 (1934); 146, 243 (1936); 149, 217 (1937); 160, 261 (1938): 161, 145 (1939); 163, 265 (1939); 166, 77 (1940); Angcw. < h e m . , 63, 93 (1940). f 2 ) R . H.Bailes and M. Calvin.
COPPER-SALICYLALDEHYDE CHELATES, M = Cu Compound Formula Xm x 108 Copper salicylaldehyde 1440 Ethylenediimine 1,n = 2 1725 Pentarnethylene1,n = 5 diimine 1410 Hexarnethylene1,n = 6 diimine 1390 Heptamethylene1,n = diimine 1070 111, R Anil 1410
-0
4-NO2 Anil
111, R
--cZ)-NOz
Anil
111, R
-
4-CH1 Anil
111, R
-e2
4-COOH Anil
111, R
-c>-COOH
1310
4-XaSOs Ani1
111, R
--CI)--SOaNa
1670
4-Phenyl Anil
111, R
4-Methoxy Anil
111, R
4-OH
0
0
1770
.
950
1360
0-a
1350
--CI)-OCH*
1220
(3) Tyson and Adams, Tars JOURNAL. 64, 181 (1942). (4) Klemm and Raddatz, 2. anorg. Chcm., 460, 207 (1942). ( 5 ) D. P. Mellor and co-workers, J . Proc. Royal Soc. New Swfh Wafcs, 74, 129 (1940); 74,475 (1941); 71,27 (1941); Tars JOURNAL, 64, 181 (1942).
M. CALVINAND C. H. BARKELEW
2268
TABLE I (Concluded) Compound
Formula
xm
CT)
Benzylimine
111, R = -CH-
Imine Ethanolimine Heptylixihe Aldoxime Triamine
111, R = H 111, R = -CH2CH20H 111, R --(CH*)sCHz II1.R = -OH 11, n = 3
I, with discussion of color, water of solvation, and methods of preparation. Susceptibilities 1360 measured in connection with this work will not be presented here. 1500 For two unpaired spins, a value of xm = 3350 1280 X is expected.
x
10'
1390 1350 810
TABLE V COBALT SALICYLALDEHYDE COMPOUNDS'
TABLE I1 COPPER CHELArES NOT FALLING INTO THE ABOVE CLASSES Compound
Xrn
x
(a)
Sal En forms
Inactive Active Pyridinate Peroxide Pyridine-peroxide
10'
HC=N 1010
(b)
3 Fluoro Sal En forms
Inactive Brown hydrate Red hydrate Piperidinate H ydrate-peroxide Active
1040
(c)
1390 1750 1340
Trifluoroacetylacetone, two forms
(d)
TABLE I11 FERROUS SALICYLALDEHYDE CHELATES
+
Compound
Formula
I, n I, TZ 11, n 11; n 11, 11, n
= = = = = =
2 2, 3-OCHa 2 3 , 3-OCH3 3, 3-C1 3, 3-OC2Hs
Xm
x
lo-'
10,850 10,600 16,200 15,000 10,300 11,000
The value to be expected for four unpaired The values quoted are spins is 10,000 X subject to an uncertainty estimated to be * 1000, because of the extreme difficulty in preventing atmospheric oxidation. However, they unquestionably indicate four unpaired electrons for all compounds. TABLE IV
NICKEL SALICYLALDEHYDE COMPOUNDS Compound
Sal prtr 3-Methoxy Sal prtr Sal En
Formula
11, n = 3 11, n = 3, 3-0C2H5 I, n = 2
Xm
x
10'
4450 4260 0
.\ complqte discussion of nickel compounds is to appear soon. It will include three series of type
Other cobalt Sal En compounds
3-Methoxy hydrate 3-Methoxy 3-Allyl 3-Ethyl 6-Methoxy 3-Butoxy hydrate 5-Iiluoro 4-Methoxy hydrate 3-Chloro &Methyl hydrate 5-Methyl 3-Phenyl a-Chloro, 5-t-butyl
For a single unpaired spin, one expects a value of 1280 X 10-O. Higher values are caused by incomplete quenching of the orbital contribution to the magnetic moment. Lower values are attributed to impurities.
En En (solvation) 3-Methoxy Sal En Diethylene triamine 3-Methoxy Sal prtr. 3-Chloro Sal prfr. 3-Ethoxy Sal prtr.
3 Ethoxy Sal En
Pyridinate Red hydrate Yellow hydrate Active
1085 Acetoacetic ester
Vol. 68
(e)
Cobalt Sal prtr compounds
Co Sal prtr Co Sal. prtr hydrate Co Sal prtr peroxide 3-Kitro 3-Chloro 3 - h.1et hox y 3-Ethyl-4 tnethoxy 4-Nitro (j-Clhloro
3-Methyl 3-Methoxy hydrate 3-Phenyl 5-Methyl 5-Chloro 5-Hydroxy 4-Methoxy 3-Fluoro &Ethyl
TypeI; n = 2 Xm x 10'
2170 2650 1900 -200 50 Type 1, n = 2
3-F
2750 5170 1950 4360
0 2740
-
Type I ; n 3-OCyHs
4500 3460 8800 2680 x m X 106
8530 2500 1980 2500 2340 9700 1960 8850 3740 2740 3100 7890 3300 11, It
e
7700 7840 1200 6960 8000 8950 6500 8020 7780 8850 8060 8430 7070 7700 7880 8790 7420 8600
3
2
MAGNETIC PROPERTIES OF OXYGEN-CARRYING SYNTHETIC CHELATES
Nov., 1946
(Concluded)
TABLE V (f)
2269
Other cobalt salicylaldehyde chelates
Formula
Compound
cis-Cyclohexonediimineb trans-Cyclohexonediimineb
\
c-c /"
HzC
c-c
HC--CH I
10'
2405
\
N-Methyl prtrb Diethylene triamine
Xm
x
N=CH / H\
2390 --D
CH2
/
Hz Hz 11, n = 3, methyl on lower N
8750
11. n = 2
2030
I
3360
I HC---CHz I
I
2380
CHa A complete description of all forms of the oxygencarriers is to be found in another paper of this series, Calvin, Bailes and Wilmarth, THIS JOURNAL, 68, 2254 (1946); Bailes and Calvin, forthcoming. * The diamines in these compounds were prepared for us under the direction of Dr. T. A. Geissman at U. C. L. A. The values expected are: 1 unpaired spin, 1280; 3 unpaired spins, 6280.
HIGHTEMPERATURE
C**UrnL
HCAT
EHL
Low TEMPERATURE 'wk Fig. 1.
a
iron with planar dsp2 hybridization would have two unpaired spins. The rather high orbital contribution in most cases shows little quenching effect. The two anomalously high values recorded in Table I11 might conceivably be due to the presence of some ferric iron although qualitative tests indicate its virtual absence. Ordinary ultimate Discussion of Results analysis would not indicate its presence. Copper Compounds.-We expect a single unNickel Compounds.-Nickel salicylaldehyde paired electron for copper compounds, irrespec- ethylenediimine is shown to be planar from its tive of the type of linkage or of the structure of diamagnetism, whereas the others are either ionic the molecule. Cupric ion, covalently bound cop- or tetrahedral. A more complete discussion of per with square dsp2 hybridization, or tetrahe- nickel compounds is t o follow in a later paper. Cobalt Compounds.-It has been hoped that dral sp3 hybridization, all have a single unpaired electron. The fact that the values are so close some magnetic criterion of oxygen-carrying to that predicted for spin only indicates that the activity would make itself apparent; however, the orbital contribution is almost completely quenched above results indicate that this is not the case, a t by the crystalline fields. As yet, no significant least for the compounds in the solid state. I t apconclusion concerning molecular structure can be pears, however, that a necessary though not sufficient condition is that the 2-1 compound$ have drawn from these data. Iron Compounds.-All ferrous compounds one unpaired electron, while the 1-1 compounds have four unpaired electrons, which indicates have three unpaired electrons. The ethylenediimine chelates are for the most strongly that iron is present in the ionic state, in view of the fact that similar cobalt and nickel part covalent square planar, with a single unpaired compounds will be shown to be planar. Covalent electron, the single exception being the 3-phenyl
hf. CALVINAND C. H. BARKELEW
2270
250 272 295
TABLE VI T,OK. CLASS WHICH
I:
x 10s COMPOUNDS Xlr,
OBEY THE CURIEWEISSLAW
Copper salicylaldehyde ethylenediimine (Fig. 2) 94 4870 162 3015 226 2170 250 1980 274 1820 294 1735 320 1380 345 1480 370 1380 Copper salicylaldehyde methylimine (Fig. 3) 96 3950 164 2540 250 1695 300 1432 320 13% 345 1260 370 1180 400 1090 Active cobalt salicylaldehyde ethylene diimine (Fig. -1) 100 6100 124 5450 160 4460 212 3600 240 3220 270 2860 296 2650 320 2560 345 2380 370 2240 400 2120
T ,O K . 250 270 296
Xm
x
108
2970 2720 2500
Cobalt salicylaldehyde “prtr” hydrate (Fig. 7) 96 120 140 166 157 208 22s 250 270 295
23,500 19,600 15,880 13,700 12,650 10,880 1c.100
9250 8.550 iK10
2360 2270 1900
188 216 228 248 268 282 290 320 345 370 400
Cobalt salicylaldehyde ethylenediimine, inactive isomer (Fig. 11) 102 113 126 137 151
4460 4030 3570 3330 3030
2670 2520 2500 2480 2390 2210 2170 2130 2130 2130 2130
in which steric effects.are acting to prevent a planar structure. A number of hydrates show 3 unpaired spins, probably indicating ionic cobalt, while a few show intermediate values. These latter will be discussed in the section on temperature dependence.
Cobalt salicylaldehytle “prtr” active (Fig. 8 ) 96 120 140 166 188 208 228 250 270 293 320 345 370 490
23,200 18,350 61,100 13,700 12,080 10,870 9950 9000 8400
7670 7060 6640
/ 0
I
100
T,
6170 5720
Fig. 2.-Copper
dehyde ethylenediimine hydrate (Fig. 5) 100 21,300 164 13,900 200 11,830 220 11,010 252 9800 296 8530
CLASS 11: COMPOUNDS WHICHDo Nor OBEYTHE CURIE-WEIS LAW Cobalt 3 ethoxy salicylaldehyde ethylenediimine red hydrate (Fig. 9) 96 5100 120 4560 140 4200 168 3840 187 3500 208 3460 227 3470 250 3450 270 3460 293 3460
Cobalt 3-methoxy salicylaldehyde ethy1eni:diimine active (Fig. 6) 96 7560 120 6020 53m 140 164 4580 188 4130 208 3600 228 3220
Cobalt salicylaldehyde ethylenediirnine pyridinate (Fig. 10) 98 5180 128 3360 150 2910 170 2580 180 2470 196 2370 2370 220
Cobalt 3-methoxysalicylal-
Vol. 68
300
200
400
OK.
salicylalethylenediiminc.
,/
0
100
200
300
400
T,“E;. Fig. 3.--Copper
salicylalmethyliniine.
The value of three unpaired spins for the prtr compounds is evidence that this cobalt is ionic, since chemical evidence shows the cobalt to be 5coordinated, in a tetragonal pyramidal configuration. The ease of crystal formation, something which is not found in compounds in which the nitrogen is replaced by carbon, indicates a compact and rigid molecular structure, while the oxygen-carrying capacity indicates an open sector in
MAGNETIC PROPERTIES OP OXYGEN-CARRYING SYNTHETIC CHELATES
Nov., 1946
0
200
100
2271
300
T,OK. Fig. 7.-coSal
0
100
Fig. 4.-Cobalt
200
300
Prtr hydrate.
400
T,OK. salicylalethylenediimine active.
100
0
200
300
400
T,OK. 0
100
200
300
Fig. S.-CoSal
Prtr active.
T, O K . Fig. 5.-C!o3MeOSalEn
hydrate.
4
3 N.
I
s X 2 E X
..
0
3
100
200
300
T,OK. Fig. 9.-Co3EtOSalEn
1
I
0
100.
I
2
200
300
T , OK.
red hydrate.
by hfellor.6 It is the measurement of CoSal En which differs from that of hlellor. He apparently had peroxide formation, probably being unaware of the compound's oxygen activity.
Temperature Variation of Susceptibility The apparatus for temperature control is shown the coordination sphere. The covalent hybridiza- in Fig. 1. The sample was duspended inside the tions leading to a tetragonal pyramid are d2sp2, central vessel, past which a stream of constant d4s, d2p3, d4p, all of which would have one un- temperature air was rapidly blown. The stream paired electron. of air was produced by boiling liquid air; its I t was found, without exception. that all red temperature was controlled to *0.5' by its rate or brown compounds are planar, and all yellow, of boiling and the liquid level in the boiler. The yellow green, or orange compounds are tetrahedral latter was held constant by intermittent addition or ionic. This generalization was first po$ted out of liquid air: the current throurrh the heater was contiolled with a rheostat. TYhe operation was (6) Kimball. J . Chrm. Phys., 8 , 128 (19401 Fig. 6.-C!o3MeOSalEn
active.
M. CALVINAND C. H. BARKELEW
2272
Vol. 68
d
a3
1
I
100 200 300 T,OK. Fig. 10.-Cobalt salicylalethylenediimine pyrldinate. 0
I '
1.75I
I
100
I
I
200
300
I
I
400
500
T,OK. Fig. 12.--Cobalt salicylalethylenediimine inactive.
"[I
d
4""
B ,
indicating that the moment is decreasing. For convenience, we have plotted AS. .= 2.83 K T against T in Fig. 12. No crystal transitions have been observed for these compounds at these temperatures, so the conclusion drawn is that the behavior is due to a loss in magnetic entropy of the cobalt atom. This implies splitting of the degenerate orbital levels by the crystalline field in such a manner as to give rise to the phenomenon. Bethe' has shown that crystalline fields split the levels as diagrammed in Fig. 13, and it has further
0
100 200 300 400 T , OK. Fig. 11.-Cobalt salicylalethylenediimine inactive.
completely automatic; the thermocouple controlled a system of magnetic valves which operated the liquid air stream. Each sample was allowed one hour to reach temperature equilibrium before measurement. Temperatures above 25' were. attained with a simple non-inductive furnace. The current through the heater was controlled by a thermocouple. The comoounds measured fell into two general classes, according to whether or not they obeyed the Curie-Weiss law x,,,
- 8)
B2pa/3k(T
This predicts that the reciprocal molal paramagnetic susceptibility will be linear with temperature, with slope inversely proportional to the square of the magnetic moment. In the above formula, /3 and k are universal constants, p is the moment, and 6 is a characteristic constant.
Discussion The .first eight compounds described, those in class I, appear to obey the CurieWeiss law closely, and, for this reason, they merit little comment. The compounds in class 11, three cobalt chelates, show an unusual and quite characteristic deviation. The susceptibility shows a plateau in the intermediate temperature region,
Cubic
unperturbed
Rho m6 i c
/ sf
/ \
b
s
Fig. 13.-co++.
beerl demonstrated by Van Vleck,* that the high anisotropy of most cobalt compounds is a corollary of the same effect. It is clear that such a splitting, assuming the crystalline symmetry to be rhombic or of a lower order, can account for the behavior observed, if the plateau in the moment occurs between the levels marked d and e . For compounds in which the splitting is not so wide, those in case I, or compounds which do not split with an almost degeneratel lower level, such as copper compounds, the effect is not observed.
The Change in Magnetism on Oxygenation Two samples, one of cobalt salicylaldehyde ethylenediimine, and one of cobalt salicylaldehyde (7)Bethe, Ann, Phrs., 8 , 133 (1929). (8) Vpn VI&, PhpS. Rw.,41, 908 (1832).
OXYGENEQUILIBRIUM WITH SOLIDCHELATE CONPOUNDS
Nov., 1916
"prtr," were oxygenated in stages and the magnetic susceptibility at each stage measured. The oxygenations were carried out by suspending the weighed, -filled tubes in a bomb and exposing to oxygen for various intervals of time. The extent of oxygenation was determined by weight. The sample of the parent diamine showed the following hrhavior when exposed to 1 atmosphere of oxygen.
2273
6000
TABLEVI1 5%
Time, min.
0 2 3 15 20 30 50
Xm
0 1
x
106
2490 2440 2290 1862 1550 990 4iti 160
0.0 0.21 0.62 1.44 1.85 3.11 4.34 4 . 9 0 (complete)
2
4 02,
The data are plotted in Fig. 14. 'The line is straight, showing simple additivity of susceptibilities, as would be expected for a two-phase solid system.
g 2000 r(
6
1000
2 3 4 absorbed, yo. Fig. 14.-CoSalEn.
8
Fig. 15.-CoSal
Prtr.
A similar plot of the parent triamine is shown in Fig. 15. The curvature of the line may be due to non-additivity of the components. It is also consistent with the possibility that irreversible oxidation is taking place as saturation is approached. Cobaltic compounds would be expected to have 2 or 4 unpaired spins, in any case more than the one for the peroxide.
Summary Room tenipexature susceptibilities of a number of transition element chelates have been measured. The variation of susceptibility with temperature has been studied, and characteristic anomalies discussed with respect to crystal symmetry. Susceptibility as a function of oxygenation has been studied for two oxygen carriers.
X
1
6
%.
5
0 2
RECEIVED APRIL8, 1946
[CONTRIBUTION OF THE DEPARTMENT OF CHEMISTRY, UNIVERSITY OF CALIFORNIA, BERKELEY, CALIFORNIA, AND GATESAND CRELLIN LABORATORIES OF CHEMISTRY, CALIFORNIA INSTITUTE OF TECHNOLOGY '1
The Oxygen-carrying Synthetic Chelate Compounds. V. Solid Compounds la
w.
B Y E. w. HUGHES,~ K.
wILMARTH3 AND
THE
Equilibrium with the
M. CALVIN
The present work is concerned with the measurement of the equilibrium represented by the general reaction 2 chelate (s)
+
0 2
(g)
+(chelate)2Ot (s)
where the chelates are of type I* and bearing (1) No. 10G5. (la) The work herein reported was done under
Contract (OEMsr-279) between the National Defense Research Committee and the University of California. (2) Present address: California Institute of l'echnology. Pasadena. (3) Present address: University of Southern California, Los Angeles. (4) Calvin, Bailes and Wilmarth, THIS JOURNAL, 68, 2254 (1946). R
various substituents in the benzene ring.5 Both the oxygen equilibrium pressure and the X-ray powder diagrams of the solid phase were taken as a function of the oxygen content of the solid phase. (5) We will use the abbreviation CoSaEn for this type, inserting the substituents as required.
