The relationship of configuration to color in some complex compounds of transition elementsкод для вставкиСкачать
THE RELATIONSHIP OP CONFIGURATION TO COLOR IN SOME COMPLEX COMPOUNDS OF TRANSITION ELEMENTS A Dissertation Presented to the Faculty of the Graduate School The University of Southern California In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy by George N. Tyson, Jr. June, 1941 UMI Number: DP21729 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Publishing UMI DP21729 Published by ProQuest LLC, (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346 This dissertation, w ritten by .......... G E Q R & E ^ ......... under the guidance of h.X.8 F a c u lty Com m ittee on Studies, and app ro ved by a l l its members, has been presented to and accepted by the C o u n cil on G raduate Study and Research, in p a r t ia l f u l fillm e n t o f requirements f o r the degree o f D O C T O R O F P H IL O S O P H Y Dean Secretary D a t e ....lV m .,... 1941 Committee on Studies Chairman TABLE OF CONTENTS CHAPTER PAGE I. INTRODUCTION.................................. I II. THE NATURE OF THE P R O B L E M .................... 6 III. EXPERIMENTAL.................................. 11 Measurement of empty tube and tube filled with water to mark ............ Measurements on oobalt phthalocyanine • . • • Measurements on nickel phthalocyanine • • • • Measurements on copper phthalocyanine .... 15 16 17 Data collected from the hydrogenation of copper disalicylaldehyde ........................ S3 Results from magnetic measurements on solutions of copper disalicylaldehyde in pyridine, and on pyridine alone IV. ............. DISCUSSION OF THE RESULTSAND RELATED LITERATURE AS RELATED TO CONFIGURATIONS . . . . . . . . . V. 24 28 THE RELATIONSHIP OF COLORTO CONFIGURATION IN THE COMPOUNDS CONSIDERED, WITH A FURTHER DISCUSSION OF RELATED LITERATURE............ VI. SUMMARY AND C O N C L U S I O N S ..................... BIBLIOGRAPHY...................................... 35 41 44 LIST OF TABLES TABLE I. PAGE Colors of Coordinated Phthalocyanines of Group Ila M e t a l s ........................ II* Possible Electronic Configurations of Divalent Nickel in Complex Compounds III. 6 . . . . . . . . 9 Empirical Formulae and Analytical Results on Cobalt, Nickel, and Copper Phthalocyanine Compared with the Theoretical IV. 13 Diamagnetic Values of Atoms as Computed from Volume VI of the International Critical Tables, Page 365, for the Phthalocyanine Radical V. • • • • • • • ................. 21 Resume/ of Colors of Some Complexes of Cobalt, Nickel, and Copper . . . . . . VII. 20 Summary of Computations on Cobalt and Nickel Phthalocyanines VI. ................ • • ............ 27 Summary of Color to Configuration Relation in Divalent Nickel Complexes of Diamines as Found by Lifschitz and Co-Workers . . . . . 36 CHAPTER I INTRODUCTION It is apparent that any study of color must be severely restricted, and limited to but a small portion of the general subject, if one individual worker is to achieve any experi mental progress in a reasonable length of time. It is to be particularly noted that a complete study of color is an ex ceedingly wide field, and that experimentally it is impossible for one researcher to consider more than an aspect of the general phenomena because of the limitations of time. The title given to this experimental work is definitive of the material investigated in the laboratory and will be elaborated in the following pages. However, it is first con sidered necessary to discuss some other closely related as pects of the phenomena of color, in order to differentiate more clearly the scope of the material actually considered. The color of.dyes is an almost distinct field of investigation. In 1907, Baeyer^- suggested that the color of dyes was associated with the shift of an electron within a molecule, and the frequency of the shift was related to the color. Another notable paper2 continuing this thought 1 A. Baeyer, Ami. 354, 152 (1907). o E. Qi. Adams and L. Rosenstein. J. Am. Chem. Soo.. 36, 1472 (1914). ~ appeared a few years later, and more lately the concept of 3 4 5 resonance has been introduced. > » More recently, L. Pauling** has suggested that a quantitative calculation can be made roughly of the frequencies and intensities of the absorption bands of dyes. Thus, with such compounds as benzaurin, the resonance can be shown by the formulae: ==<_J>=o By means of wave mechanics Pauling has been able to apply to a limited number of the possible structures, equations which permit the prediction of the intensities of absorption bands The work to be described herein does not consider the color of organic dyes, but is intended rather to evaluate the contribution of the metallic portion of a metallicorganic complex to the color in certain transition complexes 3 C. R. Bury, J. Am. Chem. Soc,, 57, 2115 (1935). ^ L. Pauling, Organic Chemistry; H. Gilman, editor (New York: John Wiley and Sons, 1936), 1880-1890. (1935). 5 R. S. Mullikan. J. Chem. Phys.. 7. 121. 364. 570 “ ---~ 6 L. Pauling. Proc. Nat. Acad. Sci.. 25. No. 11, 577-582 (1939). 3 It should also be noted that the description of color is difficult, if done precisely. Thus eye fatigue, succes sive contrastings of different colors, etc., are psychological factors that have been described.7 * 8 However, in this work under consideration, these factors do not have to be consid ered, as but a small number of distinctively colored materials were investigated. The effect of particle size is also important as often the real color is masked by the degree of subdivision. Blue hydrated copper sulphate, for example, is white if the particle size is made sufficiently small. No such phenomenon is involved in the products prepared for this investigation, however, as the color remained relatively constant upon vigorous subdivision of the precipitated material by mortar and pestle. It is also well known that the color may vary with the source of illumination. The colors described in this research were viewed in bright daylight in all cases. Coloring due to the chemical composition of a material is caused by incident light striking the material. Of this light, generally part is reflected, part is absorbed, and 7 Helmholtz,s Treatise on Physiological Optics. Vol. II; J. P. C. Southall, editor TKew York: Optical Society of America, 1924). 8 D. B. Judd, J. Optical Soc. Am., 23, 359-374 (1933). 4 part is transmitted. The mechanism of the absorbed portion of the light is important, for it is this phenomenon which chiefly explains the coloring evidenced. The energy so absorbed is used in the excitation of electrons from one quantum state to a higher state. The energy regained in falling from the higher to the lower quantum state usually degenerates into heat* However, fluorescence and other light conserving effects are possible. In the experimental work performed, no fluorescence was noted. The excitation of electrons is accompanied by rela tively large energy changes, and corresponds to light in the visible and ultra violet range. However, change in the amplitude of the vibrations of nuclei, and change in the kinetic energy of rotation of molecules will give absorption that is shown only in the near infra-red, and the infra-red g portions of the spectra, respectively. No absorption spectra have been made of the materials prepared, and the visible color alone has been used for identification. Selective absorption will give rise to definite colors; if there is strong general absorption throughout the visible portions of the spectrum, the color appears 9 F. H. MacDougall, Physical Chemistry (New York: The Macmillan Company, 1936},203. 5 black. The selective absorption is sometimes known as body color. Mason^0 discusses the phenomenon of surface color, which is often observed in the case of materials which absorb light strongly. This phenomenon is caused by the same mechanism as the absorption, yet the hue of the re flected light does not have to be the same, nor the compli ment of the absorbed light. One of the materials prepared exhibits a marked surface color, and will be described in detail later. Thus, by noting the body color (and surface color also, if present) of particles that have been finely ground, a sufficiently accurate description of the compounds can be had for the purpose at hand, 10 C. W. Mason, J. Phys. Chem.. 27, 413 (1923). CHAPTER II THE NATURE OF THE PROBLEM It has been found that in a series of compounds such as the metallo-phthalocyanine complexes, the intensity of color decreases with increase in the atomic weight of the metals in a vertical group of the periodic table. Thus, in the series of phthalocyanine complexes coordinated with the elements of group Ila, the following chart illustrates the decrease in color of the compound, with increase in atomic weight of the metali TABLE I COLORS OF COORDINATED PHTHALOCYANINES OF GROUP Ila METALS Phthalocyanine Coordinated with: Colora Be +■+ dark green Mg+ + lighter green Ca+*f pale green Sr + + paler green Ba+ + faint green tinge, almost white a All of these compounds exhibit body color only. It is apparent from the chart that the metallic por tion of the complex has a modifying effect on the color. It 7 was therefore considered desirable to investigate this problem further in an attempt to determine whether the con figuration of the molecule in this series and another avail able complex compound exerted a marked effect upon the color of the compound, and the relative importance of the co ordinating group versus the configuration. Determination of the magnetic susceptibilities can be used for the establishing of the configuration of the mole cule in some cases. The magnetic criterion for bond type was first set forth by Pauling1*- in 1931 and has been much amplified and discussed by Huggins.1^ It should be remem bered, however, that this work is limited in its application and applies only to the elements and their ions through the first long transition series. For example, while the sus ceptibilities of compounds such as barium and strontium phthalocyanines can be determined, the existing theories do not allow the assigning of configurations to the molecules on this basis alone. However, in complexes containing ele ments of the first long transition series, and lower atomic numbers, the theory is well able in many cases to show the configuration of the molecule. Thus, in the experimental work considered later, divalent nickel phthalocyanine is one 11 L. Pauling, J. Am. Chem. Soc.. 53. 1391 (1931). 12 M. L. Huggins, J. Chem. Phys.. 5, 527 (1937). 8 of the compounds considered. The possible electronic arrange ments in the orbitals (with the 3d, 4s, and 4p orbitals shown in detail) and the corresponding configurations are given in Table II, page 9. It is immediately apparent that the magnetic suscepti bility is not definitively exclusive in this example. Thus, if the magnetic susceptibility of a coordinated divalent nickel ion indicates two unpaired electrons, the compound can be either planar or tetrahedral in configuration. This is due to the fact that because the planar structure is more stable than the tetrahedral in the transition metals, and because there is little difference in energy involved in the 3d and 4p orbitals, an electron from the 3d can be moved to the 4p o r b i t a l . H o w e v e r , if the magnetic susceptibility shows no unpaired electrons, the compound is planar without question. The results of X-ray diffraction work,T.whsn it is pos sible to find such work in the literature, coupled with the results of magnetic measurements, offer convincing proof of the structure of molecules. This technique will be employed in the examination of the experimental results obtained, and the influence of configuration on the color of molecules will be noted, as the main purpose of this research. 13 (1935). The E. G. Cox and K. C. Webster. J. Chem. Soc.. 731. TABLE II POSSIBLE ELECTRONIC CONFIGURATIONS OF DIVALENT NICKEL IN COMPLEX COMPOUNDS® Possible Electronic Arrangements of Ni in the Orbitals (1) Configuration Coordinating Bonds 1 2 3 3 4 4 s sp3 sp3 d d d d d s tetrahedral AGSTT 2 £ £ £ SAIL I ? 2 ss r planar dsp2 HAAGS 2 22- planar dsp2 (2) s sp3 sp3 (3) s sp3 sp3 sp3 2 2 2 The nomenclature used seems to conform to standard usage. For example, see L. Pauling, Nature of the Chemical Bond (Ithaca, New York: Cornell University Press, 1939), 94. In the aEove table, t h e w2f* in each case represents a pair of electrons donated by the coordinating organic compound to the orbitals of the metallic ion, while the wl" in each case represents an electron in the designated orbital of the metal ion* The five 3d, 4s, and three 4p orbitals only are shown in detail. All other orbitals listed are assumed to contain two electrons. Thus, in the above, the Is, 2s, three 2p, 3s, and three 3p orbitals (which are shown as ls2sp33sp3) contain two electrons each, for a total of eighteen electrons. Likewise, in the coordinating bonds, the same con vention is used. For instance, sp3 bonds indicate one's, and three p orbitals used for bonding, and each of the four orbitals contain two electrons. 10 actual experimental work, and the calculations involved, are given in the following pages* CHAPTER III EXPERIMENTAL Metallo-phthalocyanines were synthesized by practi cally the same method as first given by Linstead and ooworkers.*4 The synthesis used is as follows: (The molecular ratios of J. T. Baker Co. C. P. metal chloride salts and boric acid, and Eastman C. P. phthallic anhydride and urea are given). One and thirty-four hundredths (1.34) moles of urea are placed in a 1500 ml Erlenmeyer flask in a sand bath together with .05 moles of boric acid for a catalyst. When the temperature of the melt reaches 150°C, .4 moles of phthallic anhydride which has been intimately mixed with .1 mole of the divalent metal chloride is added slowly with stirring. The temperature of the reactants is then raised to 200-220°C, and held at this temperature until the color of the melt remains constant for one half hour. The reactant mass is allowed to cool, and the crude pigment is then removed from the flask, and ground to a fine powder. The impurities are removed by warming the finely ground crude pigment first with five times its weight of normal sodium hydroxide, filtering; then warming the ^ Linstead and Co-Workers, £. Chem. Soc.. 1016 (1934). IE filtered pigment with five times its weight of normal hydro chloric acid, and filtering again. The precipitate is repeatedly washed with water, until the filtrate gives no test for chloride ion. The precipitate is then thoroughly dried in an oven at 105°C for several hours, and the pigment is then ground again with mortar and pestle, and the sodium hydroxide and hydrochloric acid treatment again repeated as above. In all, the whole purification was repeated three times. After the last drying, the finely ground powder is weighed and then dissolved in eight times its weight of concentrated sulphuric acid. After standing for forty-eight hours the concentrated sulphuric acid solution is poured into an amount of water such that the final volume yields a 5 per cent weight solution of sulphuric acid. The pigment is highly insoluble in the 5 per cent sulphuric acid solution, and the precipitate is filtered off and washed until free from sulphate ion. The finished pigment is then dried overnight in an oven at 105°C and the dried pigment is then thoroughly ground, in an attempt to get small parti cles of relatively uniform size. Copper, cobalt and nickel phthalocyanine were synthesized by this procedure; a yield of approximately 50 per cent was obtained of each. The formulae for these compounds has been rigorously established by Linstead and co-workers*^® as being the 15 Ibid*, 1016. 13 following, in which M++- represents the divalent metal: N rv .N — c A/ 1 c II c= N The empirical formulae and molecular weights, for the respective compound considered, together with the calculated and found percentages of the metal, are shown in the follow ing table: TABLE III EMPIRICAL FORMULAE AND ANALYTICAL RESULTS ON COBALT, NICKEL, AND COPPER PHTHALOCYANINE COMPARED WITH THE THEORETICAL $a MetalT Compound Molecular weight Calcu lated Found (by ash) Found by electrolytic deposition 571.07 10.30 9.80 9.92 G3 2 H l 6 % N i 570.82 10.25 7.74 7.82 G32H1 6 % Gu 575.70 11.04 G32^16N8Go 10.4 10.59 14 The percentages of metals shown in Table III were found both by ashing and by standard electrolytic deposition. The phthalic anhydride and urea were shed also, and the metal content was found to be negligible in each case (i.e., less than .03 per cent, which is approximately the experimental error involved in the ashing procedure). It should be noted that the calculated and experimentally found values are in fair agreement, except in the case of the nickel compound, and as the synthesis establishes the structure, the metal analyses are considered to validate the correctness of the synthesis. The ashing must be done by slow heating and careful watching to avoid volatilization. There is a tendency for fumes to appear from the crucible if the firing is done too rapidly. Check results can be obtained, however, by using an additional burner above the crucible and lid. The results are shown in the accompanying Table III. The method used for effecting a solution of the phthalocyanine samples for the electrolytic deposition was as follows: The sample was dissolved in concentrated sul phuric acid and heated to practical dryness. It was found, however, that this procedure had to be repeated several times before the destruction of the complex was completed. The results of the electrolytic determinations are compared with the results obtained from ashing in Table III. 15 As shown in the table, the value for the nickel in the experimental work is found to be low. However, as the complex was found to be diamagnetic (as discussed later) it was not necessary to purify the compound further, for this investigation. The construction and theory of the electromagnet used for the determination of the magnetic susceptibilities has been previously described in d e t a i l , T h e measurements were made using calibrated gold weights, which were stand ardized against a Bureau of Standards ten gram weight. Rest points were found for each weight, as was the sensitivity, enabling corrections to zero rest point to be made where necessary. obtained: Using this technique, the following data were (All weights are given in grams.) A. MEASUREMENT OF EMPTY TUBE AND TUBE FILLED WITH WATER TO MARK (1) Weight of glass tube used in the suscep tibility determinations. (The Gouy apparatus and tube has been fully de17 scribed and illustrated previously.) 8.9114 George N. Tyson, Jr., "The Construction and Use of a Strong Electromagnet in Certain Chemical Studies" (unpub lished Master*s thesis, University of Southern California, Los Angeles, July, 1939). ^ Loc. cit. 16 (2) Weight of glass tube when subjected to influence of magnetic field used* (4*1 Anrp.)* 8 9114 (3) Weight of tube filled to lack with 15 9279 distilled water (4) Weight ofwater (3-1) at 22°G. (5) Volume of tube (taking density of HgO at (6) Weight 22°C as .99777) 7 0165 7 032 ml of tube plus water when sub jected to field of 4.1 Amps.* 15 8989 (7) Apparent loss in weight of the 0290 water (3-6) B. MEASUREMENTS ON COBALT PHTHALOCYANINE (0) Weight of tube plus cobalt phthalocyanine to mark (i.e., former level of water) (9) Weight of cobalt phthalocyanine (8-lj 11 1840 2 2726 (10) Weight of tubeplus cobalt phthalocyanine when subjected to field of 4.1 Amps.* 11 2108 (11) Apparent increase in weight of the cobalt phthaloc yanine 0268 (12) Density of the cobalt phthalocyanine as packed in the tube, 2.2726/7.032 C. 323 MEASUREMENTS ON NICKEL PHTHALOCYANINE (13) Weight of tube plus nickel phthalocyanine to mark (i.e., former level of water) 11.7908 17 (14) Weight of nickel phthalocyanine (14)-(1) 2.8794 (15) Weight of tube plus nickel phthalocyanine when subjected to field of 4*1 Amps.* 11.7836 (16) Apparent loss in weight of nickel phthalocyanine D. .0072 MEASUREMENTS ON COPPER PHTHALOCYANINE (17) Weight of tube plus copper phthalocyanine to mark (i.e., former level of water) (18) Weight of eopper phthalocyanine (18-1) 11.9633 3.0519 (19) Weight of tube plus copper phthalocyanine when subjected to a field of 4.1 Amps.* 11.9948 (20) Apparent increase in weight of the copper phthalocyanine .0315 (21) Density of the copper phthalocyanine as packed in the tube, 3.0519/7.032 .434 * 4.1 Amperes were used consistently throughout the magnetic measurements. The field developed with the distance between pole pieces used throughout was approximately 15,000 oersteds. From the foregoing data, together with the volume susceptibility of water as given in the International Critical Tables, Volume VI, page 340, which has the value of K s -.720 x 10"6 e.g.s. units, the magnetic moments of the copper and cobalt phthalocyanines can be calculated. 18 The computations for the cobalt phthalocyanine are as follows: It is seen from the data that equal volumes of cobalt phthalocyanine and water were used in the determination of the apparent changes in weight of the respective materials in the magnetic fields. That isf 7.032 mis of cobalt phthalo cyanine apparently increased in weight .0268 grams (see item B—11) while an equal volume of water lost .0290 grams (see item A-7). The magnetic field exerted no measureable influ ence on the empty glass tube (see items A)• Knowing the volume susceptibility of water (K - -.720 x 10"^), the volume susceptibility of the cobalt phthalocyanine can be simply computed: -0.0290 B 0.0268 -0.720 x 10-6 g K « 0.664 X 10“° c.g.s. The volume susceptibility can be readily converted to the unit weight basis or specific susceptibility, X s , by dividing by the "density," (which will depend on the relative degree of tightness of the packing)• Thus X 8 s | a 0.66.4_ x 10~6. „ 2.055 x 10=6 d 0.323 The specific susceptibility is converted to the molecular susceptibility (Xm ) merely by multiplying by the molecular weight. Thus X 3 x M : 2.055 x 10“6 x 571.03 « 1150. x 10“6 The molal magnetic susceptibility, containing dipoles 19 “IQ of one kind only has been equated by Langevin, ° in which the effect of both the diamagnetic organic portion and the para magnetic metallic portions of the molecule are considered. It has already been seen that the diamagnetic is opposite to the paramagnetic effect, and so the equation must take into account this factor. The equation is: Xm = Na f Nu2/ 3kT where, a - the diamagnetic molecular susceptibility N = 6.06 x 1023 k s Boltzmann* s constant T a Absolute temperature u * permanent magnetic dipole moment (magnetic moment) The diamagnetic effect is present, because the action of a magnetic field causes a negative polarization (known as the Larmor Precession) in all substances. It can be sufficiently precisely computed from tables, by merely add ing the diamagnetic values for the atoms present. Thus Na has been computed from the values in Volume VI of the International Critical Tables, page 36, as follows: The empirical formula of the phthalocyanine radical as given by 18 Bulletin of the National Research Council, Theories of Magnetism. 55. 19 E. C. Stoner, Magnetism and Matter (London: Meth and Company, 1934), 110. The whole subject of magnetic sus ceptibilities is discussed in this work, and in particular also, J. H. VanVleck, The Theory of Electric and Magnetic Suscepti bilities (London: Oxford University Press, 1932). 20 Linstead20 is 0 3 2 ^ 1 6 ^8 * structural formula of the com pound has been shown previously on page 13. In this formula it can he seen that, per molecule, there are twenty-four carbon atoms in the benzene rings, and eight carbon atoms with ethylenic linkages. The diamagnetic effect of an ethylenio and benzene carbon vary, and this has been accounted for in the following table. TABLE IV DIAMAGNETIC VALUES OF ATOMS AS COMPUTED FROM VOLUME VI OF THE INTERNATIONAL CRITICAL TABLES, PAGE 365, FOR THE PHTHALOCYANINE RADICAL Number of atoms Value per atomic wt. (cgs units x 10+6) Value per molecule (cgs units x 10+6) 24 benzene carbons - 7.75 - 176.0 16 hydrogens - 3.05 — 48.8 8 Ethylenic carbons -11.95 - 95.6 8 Nitrogens - 5.8 - 46.4 Thus, the total diamagnetic effect of the organic portion of the phthalocyanine compound is the sum of the in dividual atoms, which is obtained by adding the last column, or -376.8 x 10"° e.g.s. units, which is the value of Na. 20 Linstead and Co-Workers, J. Chem. Soc.. 1016 (1934). El Boltzmann’s constant has a value of 1.572 x 10“6 . N ergs/degree, and thus when T *> 295, the value of -gj-fj? has a value of 4.97 x 10~36. Thus, with the previously found values of Xm and Na, the value of the magnetic moment u, can easily be found. It is most convenient to convert this value into Bohr magnetons, by dividing by the Bohr conversion unit, which is taken as .9174 x 1020. The theoretical spin dipole moment, in Bohr magnetons, is given by the equation: u s V n(n S) where n is the number of unpaired eleotrons. PI Thus it can be easily computed that the values of 1, E, and 3 unpaired electrons are 1.73, 2.83, and 3.88 Bohr magnetons, respectively. The observed moments are usually somewhat higher.22 The following table summarizes the results of the computations on the cobalt and copper phthalocyanines. TABLE V SUMMARY OF COMPUTATIONS ON COBALT AND NICKEL PHTHALOCYANINES Compound X s x 106 Xm x 106 Bohr magnetons Exptl. Calcd. Unpaired electrons present Cobalt phthalo cyanine 2.06 1155 1.8 1.73 1 Copper phthalocyanine 1.80 1038 1.8 1.73 1 0 0 0 Nickel phthalocyanine — — L. Pauling, Nature of the Chemical Bond (Ithaca, New York: Cornell University tress, 1939), 106^ 22 Ibid.. 107. 22 The nickel phthalocyanine was diamagnetic, and ac cordingly has no unpaired electrons. The phthalocyanines of Be+*+, Mg+-<-, Ca++, Sr-*-+, and Ba++ were synthesized using the same procedure as effected the synthesis of cohalt, nickel, and copper phthalocyanine, except that it was not found possible to purify them by the acid and base washing. In order to avoid the decomposition of these phthalocyanines, purification was effected by re peated washings with 96 per cent ethyl alcohol. The yields obtained were approximately 30 per cent in all cases. The phthalocyanines prepared in this manner, again supporting the work of Linstead, were all found to be diamagnetic. Another phase of the experimental work consisted in the reduction of copper disalicylaldehyde. This compound, along with cobalt and nickel disalicylaldehyde, has been Oft thoroughly described previously in the literature. ° In this work, the copper disalicylaldehyde was dissolved in pyridine, and the magnetic moment measured. The solution was then put into a Pyrex flask and evacuated by a vacuum pump to 15 mm of Hg pressure. By means of a two-way stop cock, hydrogen from a cylinder was introduced, in great excess of the theoretical amount required to reduce the cupric to cuprous ion. The flask was then heated to approximately 98°C prc G. N. Tyson, Jr., and S. C. Adams, J. Am. Chem. Soo.. 62, 1228 (1940). for several hours, and the originally green pyridine solution of eupric disalicylaldehyde changed to a deep ruby red color, provided the original material was allowed to stand for some time before the hydrogenation was attempted. The data for this work follow: DATA COLLECTED FROM THE HYDROGENATION OF COPPER DISALICYLALDEHYDE 1. 2.4016 grams of copper disalicylaldehyde diluted to 100 ml with pyridine. 2. (.0079 moles of compound.) 50 mis of the above solution. (0040 moles of Cu disalicylaldehyde) used in hydro genation set-up. 3. System evacuated to 15 mm Hg pressure. The pump was kept in operation for ten minutes, and as the vapor pressure of pyridine is appreciable at this temperature, it is assumed that most of the air was swept out during the evacuation. 4. Approximately .008 moles of hydrogen is allowed to enter the evacuated flask. 5. Solution heated to 98°C for two hours and no change of color was noted. The material was allowed to stand un disturbed for six days. 6 . After standing for six days, the solution had developed a brown cast, as had the remainder of the solution which 24 had not been put into the hydrogenation set-up. The 50 ml of solution in the flask was again treated as previously, that is, evacuation)- to 15 mm of Hg pres sure, then the introduction of approximately .008 moles of hydrogen. On heating at 98°C for thirty minutes, a ruby red solution developed. RESULTS FROM MAGNETIC MEASUREMENTS ON SOLUTIONS OF COPPER DISALICYLALDEHYDE IN PYRIDINE, AND ON PYRIDINE ALONE The pyridine used was J. T. Baker and Company C. P. grade. The calibrated weights previously mentioned were used, and the weighing technique was the same. That is, actual rest-points were determined in all cases, as were the sensitivities, and the appropriate correction to a zero rest-point was made for the weighings. The same tube was used in the magnetic field as was used for the previous measurements, and the tube each time was filled with the solution to an etched mark which was found in the phthalo cyanine measurements to be 7.032 mis. are as follows: The results obtained (All temperatures are at 23°C.) 7. Apparent loss in weight of 7.032 mis of pyridine 3. Apparent loss in weight of solution of 7.032 ml of solution made by diluting .0241 gr. 25 2.4016 gr. of Cu disalicylaldehyde with 98.2 gr. of pyridine. (Measurement made within five minutes of the mixing of the complex in the pyridine ,0202 gr, 9# Apparent loss in weight of 7.032 mis of the above solution of copper disalicy laldehyde after standing six days. (Brownish tint.) .0202 gr, 10. Apparent loss in weight of 7.032 mis of the original solution that had been "hydrogenated" with change in color after standing six days. (Color is ruby red.) .0206 ^r; The computations with the above values are as follows: Items (7)-(8 ) - .0241 - .0202 - .0039 gr. This is a paramagnetic value and actually represents an apparent increase in the weight due to the presence of the copper disalicylaldehyde. The value is identical for the solution that had stood for six days. It is found in Volume VI, page 364 of the International Critical Tables that the volume susceptibility of pyridine is -.611 x 10“6. Thus, using this relationship to find the volume susceptibility of the copper disalicylaldyhyde, the following relationship is valid: - 0.0241 -.611 x 10"6 " .0039 K K - .103 x 10“ 6 26 The "density” of copper disalicylaldehyde in the sample isj 2*4016 98.2 4 2,4016' — ni>A "" So, the specific susceptibility is Xs - 0-103 x IQ - 6 „ 4.29 x 10“® .024 When by converting this value and the value of Xs obtained by computing the apparent change of weight in the hydrogenated material, it is found that approximately 1.9 Bohr magnetons are exhibited in all three cases. Thus it is seen that one unpaired electron is found in all cases, and it is to be particularly emphasized that the complex, whether it colors the pyridine solution green or ruby red, still exhibits one unpaired electron. In the table following, page 27, the colors of the compounds to be discussed later are listed as a resumed The results of the magnetic measurements on the com pounds described and the relationship to color, will be dis cussed fully in the following pages. 27 TABLE VI RESUME OF COLORS OF SOME COMPLEXES OF COBALT, NICKEL, AND COPPER Compound Body color Surface color Cobalt phthalocyanine Extremely deep Blue with purple Black cast Metallic copper Lustre Nickel phthalocyanine Rich deep blue None Copper phthalocyanine Deep purple Metallic copper Lustre Freshly prepared copper disalicylaldehyde solution Green None Copper disalicylaldehyde solution stored six days Green with a brownish tint None Copper disalicylaldehyde solution stored for six days, and hydrogenated Ruby red None CHAPTER IV DISCUSSION OF THE RESULTS AND RELATED LITERATURE AS RELATED TO CONFIGURATIONS It was found as listed in the experimental section that cohalt phthalocyanine exhibits a magnetic moment cor responding to one unpaired electron. The twenty-five electrons of divalent cobalt ion are arranged in the orbit als as follows: 3 Is 2sp3 3sp3 4 d d d d d nsmi s P P P 2 ft* This arrangement accounts for the experimentally ob served magnetic moment of one unpaired electron, and as the bonding (shown by the "2 s") occurs as dsp2 , the resulting compound is coplanar. The convention used in the nomencla ture of the orbitals above was shown on page 9 in detail* The w2sw refer to electron pairs donated to the metallic ion by the coordinating group, etc. This nomenclature is adhered to strictly in the following pages* In the case of the copper, it was seen that one un paired electron was present in this compound also. value could be interpreted in one of two ways. This The cupric ion has twenty-seven electrons which must be accounted for, and the possible arrangements are as follows: First, a tetrahedral structure would exhibit one un paired electron: 29 3 Is 2 sp3 3sp3 d d d d d 111111 1 11 4 j3 E E E 2 2 2 2 Or, secondly, as previously noted, the planar con figuration which has been found to be more stable than the tetrahedral could be formed by the shifting of the unpaired 3d electron to a 4p orbital, with the bonding then occurring in the 3d orbital which is now available for this purpose, together with bonds in the 4s and two 4p orbitals. Thus the configuration of planar copper phthalocyanine would have an electronic configuration of the cupric ion as follows: 3 4 Is 2sp3 3sp3 d d d d d nanus s PPP s fff This structure, it should be repeated, is in accord with the results of other investigations. Cox and Webster, in studying quadricovalent complexes of cupric ion by means of X-ray analysis, found planar configurations. 2 4 The theoretically greater strength of the planar molecule has been discussed by Pauling. 2 5 In an X-ray study of phthalo cyanines, it was established that the structure of the molecules was planar. 2 5 24 Thus it is successfully established Cox and Webster, J. Chem. Soc.. 731 (1935). 2 5 Pauling, The Nature of the Chemical Bond (Ithaca, New York: Cornell University Press, 1939), 10O. Robertson, £. Chem. Soc.. 1195 (1935). 30 that the cupric compound must he considered as planar in structure. The divalent nickel complex was found to be diamagnetic, i.e., no unpaired electron was present. This indicates with out doubt that the only feasible arrangement is as follows for the twenty-six electrons of divalent nickel: 3 4 Is 2sp3 3sp3 d d d d d 1111 n i l 2 _s £ £ £ 2 2 2 The planar configuration of the nickel compound had been previously noted. 2 7 Thus it has been established that the phthalocyanine complexes with the divalent ions of cobalt, nickel, and copper are all coplanar. It has been established previously that the copper disalicylaldehyde is planar also. 2*8 this compound is green. It was also noted that The color of the compound does not change when put into solution in pyridine. The structure suggested for this compound is as follows:2 9 27 L. Kleram and W. Klemm, J. Prakt. Chem.. 143. 182 “ 28 Tyson and Adams, £. Am. Chem. Soc., 62. 1228 (1940). (1935). Loc. cit. 31 It has heen shown in the experimental section that this compound in solution exhibits a magnetic moment cor responding to one unpaired electron. As the compound is planar in the solid state, it is assumed that the compound in solution has the same structure. Thus, the electronic configuration of the cupric ion would be: 3 Is 2sp3 3sp3 d d d d d nHllH 2 and this structure is planar. s 2 4 PPP 2 2 1 It was noted in the experi mental section that this compound was changed from green to ruby red in solution, when a solution of the green material which had stood for six days at room temperature was hydrogenated with an excess of hydrogen. It was noted that by means of magnetic susceptibility measurements the ruby red solution showed that one impaired electron was still present. If a reduction of the cupric ion had occurred, and cuprous ion was formed, the compound should have become dia magnetic, because the cuprous ion does not have an unpaired electron. Thus, the electronic configuration of the twenty- eight electrons of cuprous ion are arranged as: 3 4 Is 2sp3 3sp3 d d d d d s PPP 1111313111 2 2 2 2 Thus, cuprous ion is diamagnetic, and has a tetra hedral structure. However, the experimental section shows that the red compound exhibits one unpaired electron. This 32 is in direct contradiction to the assumption made by Calvin, 3 0 that the change in color is ascribed as being due to the reduction of the cupric ion* In this work, the uptake of hydrogen was measured and rates of reaction considered. Calvin did not measure the solutions, in which quinoline was used as the solvent, by means of the susceptibilities exhibited. The experimental values in this work have been consistently checked and definitely refute the assumption made by Calvin. A reasonable explanation can be given for the experimental results observed, however. It can be reasonably postulated that the planar structure is converted to a tetrahedral structure by the hydrogenation, and the electronic structure of the cupric ion is as follows: 3 4 Is Ssp3 3sp3 d d d d d nnain i s z PPP 222 From this arrangement it is seen that the unstable tetrahedral arrangement is attained. This is in good agree ment with the chemical behavior observed by Calvin^ in which the red form is unstable, and cannot be recovered in the crystalline form, as the red compound changes to the green on exposure to air. On the basis of experimental work of susceptibilities 30 •stn M. Calvin, Trans. Farad. Soc., 34, 1181 (1938). Loc. cit. 33 measured in this research, the hydrogenation of cupric dis alicylaldehyde is explained by the following equations: This mechanism would account for the uptake of hydro gen, and the ready conversion of the reduced compound to the original form in the presence of oxygen# One further experimental fact must still be explained, however# In the previously eited work of Calvin, as well as in this experimental study, it was noted that the green cupric compound became brown on standing. It was found, as previously noted, that the brown solution still exhibited one unpaired electron. This is taken as indicating the breakdown of the complex structure, at least partially, with a resulting formation of cupric oxide. No marked change in magnetic moment would be expected, however, as cupric ion has the following electronic arrangement in cupric oxide: 3 Is 2sp3 3sp3 d d d d d n n n m 34 It is evident, however, that this postulated meehanism of the so-called reduction of copper disalicylaldehyde is catalyzed by an agent not shown. This factor has been dis cussed at some length in the work as reported by Calvin. A summary of the work related to configuration is: Cobalt, nickel, and copper phthalocyanine as well as green copper disalicylaldehyde are all planar, while red cupric disalicylaldehyde is tetrahedral. The relationship of the configuration to color, and the pertinent literature will be discussed in the following pages. CHAPTER V THE RELATIONSHIP OF COLOR TO CONFIGURATION IN THE COMPOUNDS CONSIDERED, WITH A FURTHER DISCUSSION OF RELATED LITERATURE Recently Lifschitz and his collaborators®** have pre pared, and measured magnetically, many complexes of nickel. This work appears to indicate that the color of the com pound is closely related to its bond and coordination type. The compounds prepared were the nickel complexes of stilbenediamine (1 , 2 diphenylethylenediamine, which is desig nated as "stien" in Table VII to follow) and monophenylethylenediamine (which is designated as "phenen" in Table VII), In these complexes, two molecules of the diamine are coordinated with divalent nickel. These workers have found that all of the diamagnetic complexes are yellow, and all of the paramagnetic complexes are blue. Their results are summarized in Table VII. It is readily seen that this work lends striking credence to the theory that the color is dependent on the configuration. From Table VII it is noted that compounds of identical composition, such as Ni phenen2 (NOgIg, Ni stieng(ClgCCOO)g, Ni phenengtClO^Jg, can be either blue or yellow, depending only on the magnetic susceptibility. In the remaining compounds, the differences other than the 3 2 Lifschitz, Bos and Dijkema, Z. Anorg. Alle.1. Chem. 242, 97 (1939). ~ 36 TABLE VII SUMMARY OF COLOR TO CONFIGURATION RELATION IN DIVALENT NICKEL COMPLEXES OF DIAMINES AS FOUND BY LIFSCHITZ AND CO-WORKERS* Diamagnetic complexes (yellow) Paramagnetic complexes (hlue) Ni stien2S04 'H£0 Ni st ien2 S04 *2H20 Ni stien2(Cl3CC00)2 Ni stien2(Cl3CC00)2 Ni stien2(HCOO)2 *4H20 Ni stien2(HC00)2 Ni phenen£(0 1 0 4 ) 2 Ni phenen (0 1 0 4 ) 2 Ni phenen2(N03)2 Ni phenen2(N03)2 Ni stien2Cl2*2H20 Ni phenen2(N03 )2 «2H20 Ni stien2Cl2 Ni stien2(0 ^ Ni stien2(N03)2 Ni stien2(CH3C00)2 Ni stien2(0 1 0 4 ) 2 Ni phenen2Cl2#2H20 5000)2 Ni stien2 (C^q H-^g04BrS)2^ a Lifschitz, Bos and Di.ikema. Z. Anorg. Alle.i. Chem., 242, 97 (1939). ~ * ---13 d-a-Bromocamphor-S- Sulfonate 37 susceptibility is not great. Thus, the yellow Ni stiengSO^HgO which is diamagnetic contains only one less molecule of water than the blue paramagnetic Ni stiengSO^'EHgO. Inspection of the remainder of Table VII indicates that the differences between the diamagnetic and paramagnetic complexes are not striking except for the magnetic effect of the unpaired elec trons. The differences in color (and corresponding differ ence in susceptibilities) of the blue and yellow compounds were obtained by slightly changing the conditions of the syntheses. Thus, such differences as rate of cooling, the solvent used for precipitation, etc., would determine whether a diamagnetic or paramagnetic compound would result. Lifschitz and his co-workers3 3 have conclusively assigned the planar structure to the yellow diamagnetic com pounds on the basis of other experimental work. compounds are assumed to be tetrahedral. The blue The generalization is then made that all diamagnetic nickel complexes of this type are yellow, and the paramagnetic complexes are blue. In a discussion of this problem, Pauling3 4 also notes that the color is determined by the nature of the attached atons as well as the type of coordination. 33 34 Thus, the Lifschitz, Bos and Dijkema, op. cit., 843. 97 (1939). Pauling, Nature of the Chemical Bond, 123. 38 diamagnetic divalent nickel disalicylaldimine complex is orange, and the paramagnetic disalicylaldehyde is green.35 Other divalent compounds of nickel which show the influence of the attached groups are the diamagnetic compounds Ni(P(C3 H 5 )3 )gX2 (with X = Cl, Br, or CIO4 ); these are red, and are to be contrasted with the paramagnetic nitrate, colored a deep red.36 Thus it can be seen that the evidence tends to support the fact that a change in color is marked when a configuration is changed, but that the colors are affected also by the nature of the atoms in the coordinating group. For purposes of comparison, the preferred formula of a yellow diamagnetic compound as given by Lifschitz and collaborators® 7 is contrasted with the formula previously given for the diamagnetic planar compound of divalent nickel phthalocyanine. 5 8 35 Tyson and Adams, J. Am Chem. Soc., 62, 1228, (1940). 36 K. A. Jenson, Z. Anorg. Allg. Chem.. 229, 265, (1936). 37 Lifschitz, Bos and Dijkema, Z. Anorg. Allej. Chem.. 242. 97 (1939). 33 (1934). Linstead and Co-Workers, J. Chem. Soc.. 1016 39 H — — H C ~ N X H I 1 c — H H N H H H N -c - c6 Hr H ^ - C - C £Hr H /J/e- An inspection of the above formulae show that in both complexes the divalent nickel is bonded to four nitrogens atoms. Although both complexes are diamagnetic, and possess planar structures, the Ni stien2 X 2 is yellow and the nickel phthalocyanine is an intense blue. The differences in the 40 coordinating groups are seen to exert a dominating influence on the color, and slight differences may cause a marked change. It should also be stressed that when the configura tion of the divalent metal is changed in the molecule, the color will also undergo a marked change. Thus, it seems reasonable on this basis, when coupled with the previous discussion of the stability of planar and tetrahedral con figurations, to assume that the planar green copper disali cylaldehyde changes to the red tetrahedral configuration when the hydrogen is taken up. An inspection of the experimental data shows that cobalt, nickel, and copper phthalocyanines are of varying shades of blue. This data indicates that there are but slight gradations in color, when the same coordinating group is used, with the change in increasing weight of the central metal ion. This appears to indicate definitely that the co ordinating portion of the complex molecule, at least in the phthalocyanines investigated, has the dominant influence on the color, and the choice of the metallic ion merely modifies the color slightly. Certainly it is evident that the difference of diamagnetism and paramagnetism does not radically alter the color in the cases of the paramagnetic cobalt and copper phthalocyanines and the diamagnetic nickel phthalocyanine. However, the nature of the coordinating group precludes the formation of bonds other than the planar type, and it is to be stressed that no radical change in color occurs. CHAPTER VI SUMMARY AND CONCLUSIONS In experimental work with the compounds formed by co ordinating divalent ions with phthalocyanine, and the analysis and determination of the magnetic susceptibility of some of the compounds, it has been found possible to verify and deduce some limited conclusions concerning the color of co ordinated compounds. It has been found that in the series of complex sub stances formed with phthalocyanine and the ions of the elements of Group Ila of the periodic table, beryllium phthalocyanine is deep green, and the color becomes progres sively lighter with increase in atomic number, until In the case of barium phthalocyanine, the compound has but a faint tinge of green. Because of the nature of the coordinating group, as found in the literature, it is known that all of the compounds are planar in configuration. In a more extensive investigation of the compounds cobalt, nickel, and copper phthalocyanine, it has been found that cobalt and copper phthalocyanine are paramagnetic, and exhibit one unpaired electron, while nickel phthalocyanine is diamagnetic. All of the compounds are planar in con figuration as found from their measured susceptibilities, and that these compounds show varying shades of blue. Thus 42 it is indicated that the configuration functions as an im portant factor in the determination of color, and the metal ion modifies the color. It has also been noted that the color of planar nickel compounds varies with the atoms in the coordinating group, as seen by a comparison of probably planar nickel disali cylaldehyde, which has been previously described. compound is green. This The effect of the coordinating group can be more fully illustrated by a further search of the literature. Thus, the planar complex of divalent nickel diphenylethylenediamine is yellow. Both this compound and blue nickel phthalocyanine are coordinated to four nitrogen atoms, thus lending further support to the statement that the color of the complex, of the configuration under consid eration, is strongly affected by the nature of the coordin ating groups. The marked change in color with change in configura tion has been shown by the change of color of copper disali cylaldehyde in pyridine solution, upon hydrogenation. This compound, which had been previously shown to be green when occurring as a planar structure, was found to change to a red color on assuming the tetrahedral structure after hydrogenation. The magnetic measurements on these solutions conclusively showed that there was no change in the elec tronic configuration of the divalent copper after the 43 hydrogenation. Substantiation of the hypothesis concerning the change of color involved when complexes undergo change in their configuration was found in the literature in the case of the nickel diamines. It was noted in this case that the planar compounds were yellow, while the tetrahedral compounds were blue. A reasonable reaction to explain the change in color in copper disalicylaldehyde in pyridine solution when treated with hydrogen has been given. The reaction is: <0 Cx) In this reaction, the compound (1) is green, with a planar configuration, and on hydrogenation of the aldehyde group the compound is changed to a tetrahedral structure (2 ). The measurements of the magnetic susceptibilities are in conformity with this hypothesis. BIBLIOGRAPHY BIBLIOGRAPHY A. BOOKS Clark, C. H. D., Electronic Structure and Properties of Matter. London: Chapman and Hall, Ltd“ 1934. Gilbert, N. E., Electricity and Magnetism. The Macmillan Company, 1932. Hirst, A. W., Electricity and Magnetism. Hall, Inc., 1937. New York: New York: Prentice- Knowlton, A. A., Physics for College Students. McGraw-Hill Book Company, 1928. MacDougall, F. H., Physical Chemistry. Macmillan Company, 1936. Mellor, J. W., Higher Mathematics. and Company, 1931. New York: New York: The New York: Longmans, Green Page, L., Introduction to Theoretical Physics. Van Nostrand Company, 1929. New York: Pauling, L., The Nature of the Chemical Bond. 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