the solubility of Yb(thd)3is much greater in chloroform than in carbon tetrachloride and in carbon tetrachloride than in n-hexane as expected. The P r ( f ~ d )complex ~ is systematically more aggregated This is in agreement with some than the E ~ ( f o d )complex. ~ related observations contained in a report by Sievers et a [ . (13) on the solvation behavior of 3-trifluoroacetyl-d-camphorate chelates. In chloroform, the La(II1) complex is much more aggregated than the Er(II1) complex. The decrease in aggregation with decreasing ionic radius may be interpreted through a lowering of the dipole moment as previously suggested for chromatographic data (14). Crystallographic data also show this influence of the ionic radius. Further, Yb(thd)3 is approximately ten times more soluble in chloroform than is Eu(thd), (15, 16), as can be expected from the smaller ionic radius of the Yb(II1) ion and, thus, from its smaller dipole moment and molecular association. On the basis of NMR spectra, Archer, Fell, and Jotham (17) recently reported the aggregation of the thd chelates. The relatively intense peak attributed by these authors to di(13) B. Feibush, M. F. Richardson, R. E. Sievers, and C. S . Springer, Jr., J. Amer. Chem. Soc., in press. (14) C. S . Springer, Jr., D. W. Meek, and R. E. Sievers, Znorg. Chem., 6 , 1105 (1967). (15) K. J. Eisentraut and R. E. Sievers, in “Inorganic Syntheses,” W. L. Jolly, Ed., Vol. XI, McGraw-Hill, New York, N.Y., 1968, p 94. (16) P. V. Demarco, T. K. Elzey, R. B. Lewis, and E. Wenkert, J. Amer. Chem. SOC.,92,5734(1970). (17) M. K. Archer, D. S. Fell, and R. W. Jotham, Znorg. Nucl. Chem. Lett., 7,1135 (1971).
Table I. Overall Aggregation Constants of the fod Chelates
Pn = [n-mer]/[monomerln Chloroform Carbon tetrachloride n-Hexane
EU(f0d)s log P 2 log Pa 0.2 ... 2.00 3.70
... 4.78
Pr(fod)s log 8 2 0.2
log P 3
2.53
... 6.06
3.71
...
mers in solution is believed to be due to impurities, for this peak does not appear for solutions of freshly purified compounds in purified solvents. The formation of Eu(fod), and P r ( f ~ d )aggregates ~ does not introduce additional peaks in the NMR spectra and the shift of the tert-butyl group peak is fairly constant in the concentration range investigated. This study was concerned only with aggregations in solutions of the free metal complexes. The extent of this phenomenon is very likely lowered upon the addition of an organic substrate which, in practice, is usually present in large excess. Under these conditions, the aggregation of the residual free fod chelate is low and is, thus, not necessarily reflected in the observed chemical shifts. RECEIVED for review April 3, 1972. Accepted July 19, 1972. Work supported in part by the National Science Foundation under Grant GP-30692X. Ofie of the authors (J.F.D.) also wishes to acknowledge financial support under fellowships from NATO and Patrimoine de 1’UniversitC de Likge (Belgium),
GINA-A Graphical Interactive Nuclear Magnetic Resonance Analysis Program Stephen R. Heller Heuristics Laboratory, Dicision of Computer Research and Technology, National institutes of Health, Bethesda, Md. 20014 Arthur E. Jacobson Laboratory of Chemistry, NIAMDD, National institutes o j Health, Rethesda, Md. 20014 THE AVAILABLE COMPUTER PROGRAMS (1-4) for calculating theoretical spectra are slow and cumbersome to use. Direct access to the WYLBUR text-editor system (5) on the DCRT/ Computer Center Branch IBM 360/370 batch programmed computer system at NIH enabled us to eliminate the error prone punched-card approach to the analysis program. However, in such systems the results from both the initial fit and iterative calculations are slow in forthcoming and the
Casetellano and A. A. Bothner-By, J. Chem. Phys., 41, 3863 (1964). (2) J. D’. Swalen and C. A. Reilly, ibid., 42,440 (1965). (3) R. K. Harris and C M Woodman, Mol. Phys., 10,437 (1966). (4) R. B. Johannesen, J. A. Ferretti, and R. K. Harris, J . Magn. Resonance, 3, 84 (1970). (5) S. J. Kaufmann, A. E. Jacobson, and W. F. Raub, J. Chem. Doc., 10,248 (1970); see references 2 and 3 therein.
(1) S.
Calcomp plots of the results are even slower. While the computer run normally takes 1-2 hours, the overall elapsed time including the plots normally takes several days. The usual procedure for an initial fit calculation, with a number of first guesses, would take at least a week, or, on occasion, .weeks,before a reasonable first fit is made for the experimental :spectrum. In addition to the time factor, the cost of the numerous Calcomp plots and the calculations tend to make the analysis an expensive proposition. Thus we decided to rewrite the original UEAITR program (4) for the PDP-10, a time-sharing computer. The advantages of the time-sharing computer are numerous, with the main ones being the possibility of direct and immediate interaction and a graphic display of the resulting calculation. We denote the composite of the original program, now capable of display and plotting of the initial fit and iterative calculations, as GINA (Graphical Interactive NMR Analysis).
ANALYTICAL CHEMISTRY, VOL. 44, NO. 13, NOVEMBER 1972
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n,
Figure 1. Initial fit (zero iteration) of the data of Batterham, Bell, and Weiss at 250Hz sweep width
IS0
SO0
410
400
A I
I
~
I
I
"
I
I "
"
"
I
'
EXPERIMENTAL SPECTRUM SWEEP WIDTH .PSO HI
Figure 2. The 100-MHz experimental spectrum of the ring C protons of codeine at 250-Hz sweep width
n,
Figure 3. Initial fit (zero iteration) of the 100-MHz data at 100-Hz sweep width
The overall procedure [described in step-by-step fashion in an instruction manual (6)] for an analysis of an NMR spectral pattern is as follows:
I
1) Input trial parameters of chemical shifts and coupling constants using the PDP-10 text editor, SOS. 2 ) a) Run GINA for an initial fit. b) Display results graphically. c) Modify trial parameters, if necessary. d) Run GINA for a new initial fit. e) Etc. 3) Using the printed output of energy level labels and associated frequencies, text-edit the label and frequency disk file as needed, according to the frequencies noted in the
experimental NMR spectrum. The user's manual (6) shows examples of the output of the initial run and the modified (text-edited) input for the iterative run. In this particular case, there were 80 theoretical line frequencies, 76 of which were used in the iterative calculation. 4) a) Run GINA for iterative fit. b) Display results and, if satisfactory, plot the results of either the full spectrum, or portions of the spectrum as viewed on the display screen; the user changing the sweep offset and sweep width. The total elapsed time for the above procedure is 1-3 hours. An example of the analysis of an ABCDX five-spin system in codeine will be given as an example of how the program works.
( 6 ) S . R. Heller, "DCRTICIS, Gina-NMR Analysis Program User's Manual," Division of ComDuter Research and Technology, Bethesda, Md. 20014, May 1972.
The NMR spectrum of codeine (see Figure 2 for structure and numbering system) was desired in order to determine the
2220
EXAMPLE
ANALYTICAL CHEMISTRY, VOL. 44, NO. 13, NOVEMBER 1972
-~~ ~
~~
Table I. Chemical Shifts and Coupling Constants of the C Ring of Codeine J, Hz 8, PPm Proton No. Batterham, Bell, and Weiss data (9) Zero iteration data Final iterative data
5
6
7
8
14
5,6
57
6,7
6,s
6,14
7,s
7.14
8-
4.91 4.85 4.88
4.16 4.14 4.17
5.72 5.67 5.70
5.32 5.26 5.28
2.63 2.66 2.69
6.4 6.4 6.4
1.3 1.3 1.3
1.8 1.8 2.0
2.9 3.1 3.0
2.6 2.6 2.7
10.0 10.0 10.0
3.0 3.0 3.0
2.5 2.3 2.3
Figure 4. Final iterative fit of the 100MHz data at 250-Hz sweep width
550
am
450
400
Y
Figure 5. Final iterative fit of the 100MHz data at 100-Hz sweep width
configuration about C-6 of a newly synthesized 6-methylisocodeine and a spiro oxirane from codeinone (7),and for the calculation of the shielding caused by the bonds in the spiro oxirane molecule (8). Batterham, Bell, and Weiss have published an analysis of ring C of codeine using 60-MHz data (9). We used their values for the chemical shifts and coupling constants of the H5,He, H,, Hs, and H14protons, and obtained the zero iteration (initial) fit shown in Figure 1. These were observed at the graphics terminal and plotted at a sweep width of 250 Hz. Although this spectrum is not overly different from the experimentally obtained spectrum shown in Figure 2, we desired a more accurate fit. Thus, we obtained the NMR spectrum of codeine on a 100-MHz instrument. The initial fit to the chemical shifts and coupling constants obtained from this spectrum is shown in Figure 3. This appeared to be somewhat better than the Batterham, Bell, and Weiss fit, but was still not quite close enough to the Figure 2 spectrum. The printed output of frequencies obtained from this initial fit was modified to conform more precisely to the experimentally observed frequencies. After about three such trials, three iterations gave us our final result, now nicely matchedspectra as shown in Figures 4 and 5. The Batterham, (7) L. J. Sargent and A. E. Jacobson, J. Med. Chem., 15, 843 ( 1972). ('1 A' E' Jacobson, H. J. .' Yeh, and J * erg. Mak'n. Resonance, in press, 1972. (9) T. J. Batterham, K. H. Bell, and u. Weiss, Aust. J. Chem., 18, 1799 (1965).
Bell, and Weiss parameters, along with the initial and final parameters found here are shown in Table I. All five chemical shifts and all ten coupling constants were varied in the iterative calculation, which required three cycles and 23 sec of cpu time to converge. The probable errors in the final calculated values in Table I are *0.020 to *0.031 and the RMS error is 0.106. The validity of using a different is0 value for the HI4proton (indicating a very different chemical shift from the other protons) was confirmed by the fact that in treating all the protons as an ABCDE system, the results (i.e., the energies, frequencies, chemical shifts, and coupling constants) were found to be the same. It may be noted that HI4is not shown in the various figures, although its coupling constants and chemical shifts were used for the calculation. The codeine molecule, however, is rather complex; HL4is further coupled to Hs, and the latter is coupled to the spins of the Hlo protons. Thus, HI4 could not be obtained from these data, which were arbitrarily limited so as to achieve the restricted aims mentioned above. COMPUTER PROGRAM
GINA is a modified version of the original UEAITR program. The program makes use of magnetic equivalence factoring to reduce the size of some matrices and, hence, increases the speed of the program. Iteration is done on the line frequencies as is done in the LAOCN3 (1) Program, and the results can be output in a number of ways, including an
ANALYTICAL CHEMISTRY, VOL. 44, NO. 13, NOVEMBER 1972
2221
energy level diagram with lines assigned according to energy levels and/or connectivity. UEAITR contained only a stick plot option. GINA contains the usual Calcomp plot option of the full spectrum drawn on a sheet of paper the exact size (50 cm) of the normal NMR spectrum chart paper. In addition, a plot option has been added that allows the user to plot that portion of the spectrum that is on the display screen. This latter plot is 25.9 cm by 25.9 cm. To get a display plot which can be directly overlapped with an experimentally obtained spectrum (Varian NMR instrument), the factor 1.93 (50.0 cml25.88 cm) must be inserted for plotting purposes. The 100-Hz sweep width spectra reproduced in this paper were obtained via the graphic display plot, the 250-Hz sweep width spectral figures via Calcomp plots. While both contain identical information, and the latter are, perhaps, “prettier,” these Calcomp plots require recomputing all the points on the graph, whereas the
display plot uses the points already computed and displayed and is thus a faster plotting routine. The program, including the plotting, requires 48000 words of core to run. The display option, when used, requires 4000-8000 more words of core, depending on how much of the spectrum (how many points of the full curve) is being displayed on the screen. The entire program is written in FORTRAN IV and requests for further information should be addressed to S. R. H. ACKNOWLEDGMENT
We would like to thank H. J. C. Yeh for the 100-MHz spectrum of codeine and J. A. Ferretti and M. McNeel for valuable discussions about the computer program. RECEIVED for review May 2, 1972. Accepted July 31, 1972.
Anodic Voltammetry of Some Aromatic Amines in Chloroform Absorpti,on Spectra and Association Phenomena of the Corresponding Cation Radicals Georges Cauquis and Denis Serve Laboratoire d‘Electrochimie Organique et Analytique du Centre &Etudes Nucliaires de Grenoble, €3. P. 85, 38041 Grenoble-Cedex, France
Two RECENT PAPERS describe the formation of aromatic amine cation radicals in chloroform, the process used being either amine oxidation ( I ) through bromine coulometrically generated in situ from the bromide ions of the electrolyte 0.1M Et4NBr or photooxidation at room temperature (2). The study is devoted to N,N‘-diphenyl p-phenylenediamine (DPPD), N,N’-dimethyl N,N’-diphenyl-p-phenylenediamine (DMDPPD), N,N,N’,N’-tetraphenyl-p-phenylenediamine (TPPD), N,N,N’,N’-tetramethyl-p-phenylenediamine (TMPD) and 4-hydroxydiphenylamine (HDPA). Cation radicals are characterized only through the position of the higher wave length absorption band. After an independent study of the oxidation of some N phenyl-p-phenylenediamines(3) and diphenylamines (4-6) in acetonitrile 0.1M Et4NC104,we noticed that in the case of DMDPPD . +, TPPD +,and HDPA. + cation radicals, there exists important disagreements between reported maxima of absorption ( I ) and those we observe in solutions resulting from the controlled potential oxidation of these amines in acetonitrile at the level of the first wave of their voltammetric curve (Table I). These discrepancies cannot be explained by either change of the solvent from acetonitrile to chloroform 9
(1) P. Wuelfing, E. A. Fitzgerald, and H. H. Richtol, ANAL. CHEM.,42,299 (1970). ( 2 ) E. A. Fitzgerald, P. Wuelfing, and H. H. Richtol, J . Phys. Cliem.. 75, 2737 (1971). (3) G. Cauquis, H. Delhomme, and D. Serve, Tetrahedron Letf., 1972, 1965. (4) Zbid.,1971, 4113. ( 5 ) G. Cauquis, J. Cognard, and D. Serve, ibid., p 4645. (6) G. Cauquis, H. Delhornme, and D. Serve, BUN.SOC.Chim. Fr.,
in press. 2222
or the intervention of the anion probably associated to the cation radical. It thus seemed interesting to complete our study by a survey of the electrochemical oxidation of the above mentionned amines in chloroform 0.25M n-Bu4NC104. We also consider the case of N-(p-methoxypheny1)-p-phenylenediamine (MPPD) which was not studied in papers ( I , 2) but which enables us to observe a striking radical association phenomenon. EXPERIMENTAL
Prolabo RP chloroform is made free from ethanol by washing with water and subsequent drying on calcium chloride, then on sodium carbonate. After distillation from sodium carboGate, the solvent is collected on molecular sieves Linde 4 A, kept in the dark, and used within three days. Tetrabutylammonium perchlorate, polarographic grade (Southwestern Analytical Chemicals) was dried under vacuum. DPPD and TPPD are Eastman Kodak products recrystallized from benzene. DMDPPD has been prepared in the same way as indicated by the authors in ( 2 ) . TMPD and MPPD are precipitated from the acidic aqueous solution of their respective chlorhydrate (Fluka puriss and Merck for analysis) by adding sodium hydroxide, the last precipitating fraction only being re-collected. Schuchardt HDPA is purified by successive precipitation from a benzene solution by addition of hexane. All products are dried under vacuum. Voltammetric curves are obtained with a Tacussel potentiostat (Model PRT 500). The reference electrode, Agl10-M Ag+ in 0.25M n-BuaNC104,is made by anodic dissolution of a siIver wire and proves to be reproducible in many experiments. The half-wave potential of ferrocene is -0.35 V us. this electrode.
ANALYTICAL CHEMISTRY, VOL. 44, NO. 13, NOVEMBER 1972
