Pigment Yellow G583-a misclassified pigment and its relationship with other acetoacetanilide azo pigments

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  • In the highly competitive tashion world the printer faces i i~reasing competition and to stay competitive must ,rlways react quickly and decisively to new trends Although the fashion requirement is recognised, there mrly n o t be a solution in the printer's arsenal and he must then rely on the dye maker to provide the answer Within the field of polyester/cellulose printing we feel there is both a fashion demand and d technical need The Procilcne N Liquid dyes could successfuly fulfil the need, cJnabling the printer to satisfy the highest fashion demands o n polyester/cellulose

    10 K k i t h , 1'wntex. 39 (1974) 4 4 5 11 B Glover. Rev Prog. Colordtion. 8 (1977) 36 12 E Fees. Melliand Textilher , 60 (1975) 595 1 3 . ,I H Provost and B M Shay. A A I C C Intern&on,il Coni (1'1x7) ( I n p r v s ) 1 4 AATCC National Conf (1974) 191 15 F Miksovsky, ,I S D C . 96 ( I 16 B (;lover and A Wyld. MI'< 17 3 Glover and J Marsden. Anirr Dyestiitl Heti , 65 (19761 4X 18 J R Provost and t I Rachmaiirr. 'l'extilveredluny, 15 (1'180) 319 19 ,I R Provost. Revista Quini Text , (March 19HO) 4 3 20 I. (;rah\ reported previously [ 11 Since then another example ti crystal structure of C I Pigment Yellow 6 (Figure 1 R-CI) in the form of Recolite Fast Yellow 3G (RCL) waib successfully determined [21 and proved to be the hytlr;l Lone tautomer In addition its X-ray powder pattern W~Y,

    442 JSDC Volume 103 December 1987

  • reported L31. During further investigation samples of Pigment Yellow G583 (HC) (also claimed to be C.I. Pigment Yellow 6) were examined. Two differences were evident immediately when compared with Recolite Fast Yellow %G. The colour was different and an examination of the X-ray powder patterns indicated that the crystal structures were different, giving rise to the speculation that commercially available C.I. Pigment Yellow 6 existed in two difftwnt polymorphs.

    However, the complete story was found to be more compliciltc!ti.

    Figure I C,, I Pigment Yellow 6 and related pigments (see text)


    Colour Comparing the colour by eye, in the bulk both were yellow, but Recolite Fast Yellow 3G had a slight but definite greenish tinge compared with Pigment Yellow G583 In the form of single crystals (much too large to be used as pigments) the difference in colour was more obvious Recolite Fast Yellow 3G was orange-yellow, while Pigment Yellow G583 is noticeably orange

    X-ray powder diffraction pattern The powder pattern of Recolite Fast Yellow 3G (as C.I. Pigment Yellow 6) has already been reportedi31. But a comparison of the photometer traces of the diffraction patterns (Figure 2) shows that that of Pigment Yellow G583 IS completely different to that of Recolite Fast Yellow ?A:;, and it was noticed that the former was much more similar to the trace for a-C.I. Pigment Yellow 5 [41 (Figure 1, R=H).

    Density of crystal It is normal during crystal structure determination to measure the density of crystal (DO) and compare it with that calculated from the X-ray data (Ox). The calculated density is obtained by dividing the weight of the unit cell contents by the unit cell volume. The agreement between these two values is a measure of the reliability of the X-ray work and is usiially fairly good.

    For Recolite Fast Yellow 3G [3] DO= 1.527?0.005 g/cm: and Ox= 1.527*0.001 g/cm3, while for Pig- ment Yellow G583 D0=1.447-C0.005 g/cm3 and Ox= 1.510-+ 0.001 g/cm3 [5]. The very poor agreement for the latter was attributed to its being a mixed crystal. On this assumption, the other component would most probably be a related pigment molecule of similar size and shape, either Ct. Pigment Yellow 1 (Figure 1, R=CH3) or C.I. Pigment Yellow 5 (Figure 1, R=H). On this assumption the observed density corresponds to a molecular propor- tion of 0.74*0.06 of C.I. Pigment Yellow 1 in C.I. Pigment Yellow 6, or 0.44?0.03 of C.I. Pigment Yellow 5 in C.I. Pigment Yellow 6.


    I x

    - ._ L =-

    - 0

    m C

    C Iu Y U

    . _

    - m

    , I I

    I I

    40 30 20 10 0

    Deflection of X-ray beam (20). degrees

    Figure 2 - Photometer traces from X-ray diffraction patterns o f (a) Recolite Fast Yellow 3G, (b) Pigment Yellow G583 and (c) tu-C.I. Pigment Yellow 5 (filtered cobalt radiation)

    Crystal structure determination The crystal structures of both Recolite Fast Yellow 3G [21 and Pigment Yellow G583 [5] have been determined. It is common, at the end of the determination, to plot the electron density of the molecule and this has been done for both of the pigments (Figures 3 and 4), projected down the a axis. The most noticeable point about these two electron density maps is that for Recolite Fast Yellow 3G the chlorine peak is much larger than any other, which

    JSDC Volume 103 December 1987 443

  • would be expected. In Pigment Yellow G583 the chlorine peak is comparable in height to those for the oxygen atoms. As a result the computer calculations were changed to allow the proportion of chlorine present to be one of the variable parameters, and these calculations gave a final value of 0.605*0.003 as the proportion of a chlorine atom present in each molecule of Pigment Yellow G583. In addition the calculations indicated that the second molecule in the mixed crystal could not be C.I. Pigment Yellow 1 but presumably C.I. Pigment Yellow 5. On this assumption, the value of 0.605-t_0.003 compares very well with the value of 0.56k0.03 obtained from the density measurements. The calculated value can also be used to give an alternative density (D,) of 1.453+0.001 g/cm:{, in far better agreement with the observed density.


    figuir J A composite electron density map of Recolite Fast Ycllow JG calculated on sections through atomic peaks. the molpcule IS projected down the a axis, with contouring at intervals of 2% per tf 3, the outermost contour being at the first intend


    FiyLire 4 G58.7 (for key see Figure 3)

    A composite electron density map of Pigment Yellow

    Chemical analysis for chlorine Unfortuately there were insufficient single crystals of Pigment Yellow G583 remaining to allow for a chemical analysis for chlorine and so this was carried out on the commercial pigment. The value obtained was 4.1 -1 0.3 wt% chlorine, equivalent to a proportion of 0.42 +- 0.03 of C.I. Pigment Yellow 6. This confirms that Pigment Yellow G583 is a mixed crystal, but the value is lower than the other two previously mentioned; this may be due t o the purifying effect of recrystallisation. Hence it appears that Pigment Yellow G583 is a mixed crystal of approxi- mately 60mol% C.I. Pigment Yellow 6 and 40 mol'% C.1. Pigment Yellow 5.

    A chemical analysis for chlorine in commercial Recolitv Fast Yellow 3G powder (performed by the same laboratories) gave a value of 9.120.3 wt% chlorine, equivalent to a molecular proportion of 0.93i0.03 of C.I. Pigment Yellow 6. This suggests that this specimen was substantially pure.

    Comparison with some other acetoacetanilide azo pigments The crystal structures of several acetoacetanilide a m pigments are similar and have been commented upon previously. Mez [6] stated that C.I. Pigment Yellow 1 and C.I. Pigment Yellow 6 are isomorphous. Some evidence has been found to support this view, but other findings contradict it, so it was concluded that the two structures are not, strictly speaking, isomorphous [7]. On the other hand Paulus [8] agreed with Mez [6]. Subsequently it was claimed [91 that Hansa Yellow 5G (a mixed crystal of 47mol% C.I. Pigment Yellow 5 and 53mol% C.I. Pigment Yellow 1) is isomorphous with C.I. Pigment Yellow I , and still later [lo] that a-C.I. Pigment Yellow 5 is isomorphous with C.I. Pigment Yellow 1. Now there is Pigment Yellow G583, a mixed cystal of 60mol'X, C.I. Pigment Yellow 6 and 40 mol% C.I. Pigment Yellow 5, t o consider. In view of the fact that, indirectly, it has been concluded that the crystal structures of C.I. Pigment Yellow 6 and a-C.I. Pigment Yellow 5 are not iso- morphous, the question is whether Pigment Yellow G5X3 is isomorphous with either of these or whether, because of its intermediate composition, its cystal structure is intermediate. This gives rise to the possibility of a solid solution existing throughout the composition range.

    When the most accurate cell dimensions and axial ratios of these pigments are considered (Table 1) differences can be seen between these compounds. The most noticeable is that C.I. Pigment Yellow 6 stands apart from the others; the values of a and 6 are smaller than even those f o r a-(2.1. Pigment Yellow 5, a smaller molecule: the values of c and ,!3 are significantly larger and the axial ratios i l r e somewhat different, particularly 6:c.

    Again it is noticeable when inspecting the X-ray powder patterns that four are fairly similar but the one from C.I. Pigment Yellow 6 is obviously different to the others (Table 1). (In addition to the patterns from (2.1. Pigment Yellow 6131 and a-C.I. Pigment Yellow 5[41, that from C.I. Pigment Yellow 1 [ll] has also been reported.)

    Thus both these criteria of the X-ray diffraction from the series of pigments suggest that C.I. Pigment Yellow 6 is not isomorphous with the other four. This is supported by an inspection of the unit cell volumes of the two series (Table 1). In one series a hydrogen atom (a-C.I. Pigment

    444 JSDC Volume 103 December 1987

  • TABLE 1

    Cell dimensions and axial ratios of some related acetoacetanilide azo pigments

    Pigment'"' a b C B V a:b:c Ref.

    C.I. Pigment Yellow 6 7.462 19.568 11.175 105.96 1569.0 0.38134:1:0.57109 [21 Pigment Yellow G583 7.572 20.366 10.413 98.89 1586.5 0.37234:1:0.51205 [51 C I . Pigment Yellow 5 7.593 20.029 10.217 101.87 1520.6 0.37910:1:0.51011 [lo] Hansa Yellow 5G 7.567 20.420 10.345 99.29 1577.5 0.37057:1:0.50661 [91 C 1. Pigment Yellow 1 7.598 20.375 10.440 98.18 1599.8 0.37291:l:O 51239 171

    (a) The unit cell in all cases IS P21/n

    Yellow 5) is replaced by a methyl group (C.I. Pigment Yellow 1). with Hansa Yellow 5G (47 mol% C.I. Pigment Yellow 5, 53mol% C.I. Pigment Yellow 1) as an intermediate, and in doing so the unit cell volume increases through the series, as would be expected. In the other series a hydrogen atom is replaced by a chlorine atom, but the cell volume increases from a-C.I. Pigment Yellow 5 to Pigment Yellow G583 (40 mol% C.I. Pigment Yellow 5, 60molY0 C.I. Pigment Yellow 6) and then decreases to C.I. Pigment Yellow 6. This decrease is unexpected considering the relative sizes of hydrogen and chlorine.

    In terms of molecular packing within the crystal structure all the molecules are essentially planar and are stacked in columns parallel to the a axis of the lattice. The angles between the molecular plane and the column axis have been calculated and so have the angles between the molecular plane and the unique (6) axis of the unit cell (Table 2). In both cases the angles indicate that the molecules of C.I. Pigment Yellow 6 are stacked slightly differently to all the others, both within the column of molecules and with respect to the unique axis of the crystallographic cell. Thus the detailed crystal structure confirms that the structure of Pigment Yellow G583 is isomorphous with a-C.I. Pigment Yellow 5, as well as with Hansa Yellow 5G and C.I. Pigment Yellow 1, but C.I. Pigment Yellow 6 is not isomorphous with the others.

    TABLE 2

    Angles between the normal to the weighted least squares molecular plane and the column axis of packing (a) and the unique axis of the crystal (6)

    Column axis Unique axis Pigment of packing'") of c rys taP Ref

    C.I. Pigment Yellow 6 27.00" 72.24" PI Pigment Yc,llow G583 28 82" 85.34" [51 C.I. Pigment Yellow 5 29.58" 79.59" 1101 Hansa Yellow 5G 29.22" 85.35" 191 C.1 Pigmerit Yellow 1 29.50" 86.26" 171 C.I. Pigment Yellow 1 29.45" 86.54" [I51 C.I Pigment Yellow 1 29.41" 86.52" @I

    (a) All thew myles were calculated using the same program, PARST[161, which not only cdculatrd the angles between the weighted least squares plane of the molecult, but also the errors, the original references used different programs (usually 1101 weighted) and this gave slightly different values for the angles

    Thus In the case of Pigment Yellow G583 the parent lattice IS that of a-C.I. Pigment Yellow 5 (in spite of it being the minority constituent) and molecules of C.I. Pigment Yellow 6 replace some (most) of those of C.I. Pigment Yellow 5 at random. So, in spite of its composition, Pigment Yellow G583 should be thought of

    as a mixed crystal of (2.1. Pigment Yellow 6 (60 mol%) in a-C.I. Pigment Yellow 5 (40mol%) rather than vice versa. The chemical composition is intermediate between C.I. Pigment Yellow 6 and C.I. Pigment Yellow 5, but nearer the former. Crystallographically (and it must be remem- bered that pigments colour as minute crystals) it is closer to a-C.I. Pigment Yellow 5 than to C.I. Pigment Yellow 6 and its physical properties will be modified accordingly. In addition a solid solution probably exists between this composition and a-C.I. Pigment Yellow 5 and does not exist between this composition and C.I. Pigment Yellow 6.

    The fact that C.I. Pigment Yellow 6 is not isomorphous with the others mentioned in this study is because the molecules are not strictly the same shape (i.e. the proportional change in size of the molecule, as one atom is replaced by another, is not the same in all directions). Therefore when hydrogen is progressively replaced by chlorine at some stage the molecules will repack to fill minimum volume; this occurs at a composition between that of Pigment Yellow G583 and C.I. Pigment Yellow 6.

    Kitaigorodski 1121 uses the term 'molecular isomorph- ism' for the similarity in shape as one atom in a molecule is replaced by a similar one, and he points out that molecular isomorphism does not necessarily result in 'crystal isomorphism'. He gives several other examples where this occurs.

    A caveat Of course being a mixed crystal does not necessarily mean that Pigment Yellow G583 is not a good pigment. The customer is not interested in the crystal lattice; colour, and fastness to light, heat and solvents are far more important to the application properties. In fact, the properties of a mixed crystal may be superior to those of the pure components. Two patents have been filed [13,14] that cover a whole series of solid solutions involving quinacridone, dichloroquinacridone, dimethyl- quinacridone, difluoroquinacridone and dimethoxyquin- acridone; it is claimed that in these cases the solid solutions show superior light fastness compared with quinacridones themselves. Thus being a mixed crystal does not, in itself, make Pigment Yellow G583 an inferior pigment.

    However, the physical properties could change with composition and so, unless the quality control is good, these properties could vary between batches of pigments. In the case of Pigment Yellow G583 this could be worse if the change of composition 'switched' the parent crystal structure from a-C.I. Pigment Yellow 5 to C.I. Pigment Yellow 6, and this will happen at some intermediate composition as the chlorine content increases.

    JSDC Volume 103 December 1987 445

  • Certainly s o m e b o d y accustomed to using a pure C 1 Pigment Yellow 6 m a y find that the physical properties arv different i f he changes t o using a mixed crystal with a different crystal structure T h e only way in which h e can check whether t h e crystal structure has changed is to obtain the X-ray diffraction pattern

    * * *

    The author would like to thank Dr D Patterson of the I lepar tment of Colour Chemistry and Dyeing, University of I x e d s , and Horace Coy a n d Co tor the samples of Recolite Fast Yellow 3G and Pigment Yellow G583 rrspectively

    REFERENCES I 2 3 4 5 6 7 8 9

    10 11 12

    13 14 15 1 6

    A Whitaket. .I S D C , 102 (1986) 66 A Whitaker. Z Knstalloyr , 163 (1983) 19 A Whitaker, J S D C , 99 (1983) 1 5 7 A Whitaker. .I S I1 C , 101 (1985) 21 A Whitaker. Acta Cryst , C42 (1986) 15hb H ~ C Mez, Her Bunsenges Phys. C h e m , 72 Iljh8) 381 A Whttaker. Z Knstallogr , 166 (1984) 177 t-: Paulus. Z Kristallogr , 167 (1984) 65 A Whitaker, Z Knstallogr , 170 (1985) 219 A Whitaker. Z Knstallogi , 171 (1985) 17 A Whitaker, J Applied C y s t . 14 (19811 61 A I Kitaigorodski. Organic chemical cystalloyraphv (New Yolk C o r i w l I , i i ! t ~ Bureau. 1961) 122 F F Ehrich ( to DUP) USP 3 1 0 0 5 1 0 (1%5), HP 9h5450 ( l%4) A R Hanke and W ,I Marshall (to DIJP) US13Z9HX47 ( 1 9 0 7 ~ C Brown and H R Yadav. Acta Cyst. C40 (1984) 5 6 4 M Nardelli. PARST a system ot computer rotintines lor rnlnJlatirrg m o l c ~ ~ ii1,1i parameters froni the results of crystal struckiw analysx (Ilniversity ot Pnrrnn Italy. 1982)

    BOOK REVIEWS Application of disperse dyes, edited by I? M Mittal (Ahmedabad Ahmedabad rextile Industry s Research Association l e l H h ) pp i x i 9 0 Price not disclosed by i)tibli\hers

    This book is described in its foreword as a Hdiik of ATIRA 5 research findings and c ~ x p ~ r i e n c ~ ~ over the years It consists of iiirrc chapters totalling 90 pages and is devoted to the application of disperse elye5 t o polyester onk, I e not to synthetic fibrc.5 generally, as might have been ( isumed from its title T h e b o o k divides into three subject areas iw ti tomprising three chapters The first x e a deals with the general principles of d~/cmg with disperse dyes the second d with pnnting and the third area with dyeing machinery and its use mainly jet iiweiirg machinery Given, on average on ly ten pages per chapter the treatment is tiiidrrstandably lather superficial and this 15 compounded by a certain amount of tcpetition bi.tween chapters It is some what surprising and disappointing there tore that thc reader has not been guided to iurthcir sources of information Only two chapters give specific references and a ilrird chapter gives a bibliography, despite tIic> f,jct that it is clear from the text that iiiiinerou\ other sources have been con

    I t 15 probably inevitable, in view of the i w o k s format. that the subjects are dealt with v c y rnuch in the context of the Indian textile industry Thus the printing Impters are concerned almost entirely

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    Color chemistry: synthesis, proper- ties and applications of organic dyes and pigments, by Heinrich Zollinger (Weinheim: VCH Verlagsgesellschaft, and New York: VCH Publishers, 1987) pp.xii+ 367. Price DM190 (ISBN 3 527262 00 8) or US$121 (ISBN 0 895734 21 4). This is a refreshing approach to the topic of colour chemistry by Prof. Zollinger, who has personally forged many links between this discipline and related branches of organic structural chemistry, reaction kinetics, physical chemistry, chemical engineering and biochemistry. Specialists within the fields covered by this broad-harrow treatment may find that their own interests are only briefly men- tioned but clearly the objective of the author is to provide a highly readable account at a level that will retain the interest of chemists in general, especially non-colour specialists on the fringe of the subject. Chemists engaged in dye synthe- sis will find valuable background informa- tion on properties and applications, whereas analysts and users of colorants for research purposes will learn much about the synthesis of these interesting struc- tures. Probably the most exciting and topical chapters are those devoted to the many applications of colorants outside the traditional substrate-based industries of textiles, paper, leather and so forth. These deal with the photo-, thermo- and electro- chemical properties of dyes, including their uses in lasers and solar energy

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    446 JSDC Volume 103 December 1987